linux/kernel/locking/lockdep.c
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   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 * kernel/lockdep.c
   4 *
   5 * Runtime locking correctness validator
   6 *
   7 * Started by Ingo Molnar:
   8 *
   9 *  Copyright (C) 2006,2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
  10 *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
  11 *
  12 * this code maps all the lock dependencies as they occur in a live kernel
  13 * and will warn about the following classes of locking bugs:
  14 *
  15 * - lock inversion scenarios
  16 * - circular lock dependencies
  17 * - hardirq/softirq safe/unsafe locking bugs
  18 *
  19 * Bugs are reported even if the current locking scenario does not cause
  20 * any deadlock at this point.
  21 *
  22 * I.e. if anytime in the past two locks were taken in a different order,
  23 * even if it happened for another task, even if those were different
  24 * locks (but of the same class as this lock), this code will detect it.
  25 *
  26 * Thanks to Arjan van de Ven for coming up with the initial idea of
  27 * mapping lock dependencies runtime.
  28 */
  29#define DISABLE_BRANCH_PROFILING
  30#include <linux/mutex.h>
  31#include <linux/sched.h>
  32#include <linux/sched/clock.h>
  33#include <linux/sched/task.h>
  34#include <linux/sched/mm.h>
  35#include <linux/delay.h>
  36#include <linux/module.h>
  37#include <linux/proc_fs.h>
  38#include <linux/seq_file.h>
  39#include <linux/spinlock.h>
  40#include <linux/kallsyms.h>
  41#include <linux/interrupt.h>
  42#include <linux/stacktrace.h>
  43#include <linux/debug_locks.h>
  44#include <linux/irqflags.h>
  45#include <linux/utsname.h>
  46#include <linux/hash.h>
  47#include <linux/ftrace.h>
  48#include <linux/stringify.h>
  49#include <linux/bitmap.h>
  50#include <linux/bitops.h>
  51#include <linux/gfp.h>
  52#include <linux/random.h>
  53#include <linux/jhash.h>
  54#include <linux/nmi.h>
  55#include <linux/rcupdate.h>
  56#include <linux/kprobes.h>
  57#include <linux/lockdep.h>
  58
  59#include <asm/sections.h>
  60
  61#include "lockdep_internals.h"
  62
  63#define CREATE_TRACE_POINTS
  64#include <trace/events/lock.h>
  65
  66#ifdef CONFIG_PROVE_LOCKING
  67int prove_locking = 1;
  68module_param(prove_locking, int, 0644);
  69#else
  70#define prove_locking 0
  71#endif
  72
  73#ifdef CONFIG_LOCK_STAT
  74int lock_stat = 1;
  75module_param(lock_stat, int, 0644);
  76#else
  77#define lock_stat 0
  78#endif
  79
  80DEFINE_PER_CPU(unsigned int, lockdep_recursion);
  81EXPORT_PER_CPU_SYMBOL_GPL(lockdep_recursion);
  82
  83static __always_inline bool lockdep_enabled(void)
  84{
  85        if (!debug_locks)
  86                return false;
  87
  88        if (this_cpu_read(lockdep_recursion))
  89                return false;
  90
  91        if (current->lockdep_recursion)
  92                return false;
  93
  94        return true;
  95}
  96
  97/*
  98 * lockdep_lock: protects the lockdep graph, the hashes and the
  99 *               class/list/hash allocators.
 100 *
 101 * This is one of the rare exceptions where it's justified
 102 * to use a raw spinlock - we really dont want the spinlock
 103 * code to recurse back into the lockdep code...
 104 */
 105static arch_spinlock_t __lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
 106static struct task_struct *__owner;
 107
 108static inline void lockdep_lock(void)
 109{
 110        DEBUG_LOCKS_WARN_ON(!irqs_disabled());
 111
 112        __this_cpu_inc(lockdep_recursion);
 113        arch_spin_lock(&__lock);
 114        __owner = current;
 115}
 116
 117static inline void lockdep_unlock(void)
 118{
 119        DEBUG_LOCKS_WARN_ON(!irqs_disabled());
 120
 121        if (debug_locks && DEBUG_LOCKS_WARN_ON(__owner != current))
 122                return;
 123
 124        __owner = NULL;
 125        arch_spin_unlock(&__lock);
 126        __this_cpu_dec(lockdep_recursion);
 127}
 128
 129static inline bool lockdep_assert_locked(void)
 130{
 131        return DEBUG_LOCKS_WARN_ON(__owner != current);
 132}
 133
 134static struct task_struct *lockdep_selftest_task_struct;
 135
 136
 137static int graph_lock(void)
 138{
 139        lockdep_lock();
 140        /*
 141         * Make sure that if another CPU detected a bug while
 142         * walking the graph we dont change it (while the other
 143         * CPU is busy printing out stuff with the graph lock
 144         * dropped already)
 145         */
 146        if (!debug_locks) {
 147                lockdep_unlock();
 148                return 0;
 149        }
 150        return 1;
 151}
 152
 153static inline void graph_unlock(void)
 154{
 155        lockdep_unlock();
 156}
 157
 158/*
 159 * Turn lock debugging off and return with 0 if it was off already,
 160 * and also release the graph lock:
 161 */
 162static inline int debug_locks_off_graph_unlock(void)
 163{
 164        int ret = debug_locks_off();
 165
 166        lockdep_unlock();
 167
 168        return ret;
 169}
 170
 171unsigned long nr_list_entries;
 172static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES];
 173static DECLARE_BITMAP(list_entries_in_use, MAX_LOCKDEP_ENTRIES);
 174
 175/*
 176 * All data structures here are protected by the global debug_lock.
 177 *
 178 * nr_lock_classes is the number of elements of lock_classes[] that is
 179 * in use.
 180 */
 181#define KEYHASH_BITS            (MAX_LOCKDEP_KEYS_BITS - 1)
 182#define KEYHASH_SIZE            (1UL << KEYHASH_BITS)
 183static struct hlist_head lock_keys_hash[KEYHASH_SIZE];
 184unsigned long nr_lock_classes;
 185unsigned long nr_zapped_classes;
 186#ifndef CONFIG_DEBUG_LOCKDEP
 187static
 188#endif
 189struct lock_class lock_classes[MAX_LOCKDEP_KEYS];
 190static DECLARE_BITMAP(lock_classes_in_use, MAX_LOCKDEP_KEYS);
 191
 192static inline struct lock_class *hlock_class(struct held_lock *hlock)
 193{
 194        unsigned int class_idx = hlock->class_idx;
 195
 196        /* Don't re-read hlock->class_idx, can't use READ_ONCE() on bitfield */
 197        barrier();
 198
 199        if (!test_bit(class_idx, lock_classes_in_use)) {
 200                /*
 201                 * Someone passed in garbage, we give up.
 202                 */
 203                DEBUG_LOCKS_WARN_ON(1);
 204                return NULL;
 205        }
 206
 207        /*
 208         * At this point, if the passed hlock->class_idx is still garbage,
 209         * we just have to live with it
 210         */
 211        return lock_classes + class_idx;
 212}
 213
 214#ifdef CONFIG_LOCK_STAT
 215static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS], cpu_lock_stats);
 216
 217static inline u64 lockstat_clock(void)
 218{
 219        return local_clock();
 220}
 221
 222static int lock_point(unsigned long points[], unsigned long ip)
 223{
 224        int i;
 225
 226        for (i = 0; i < LOCKSTAT_POINTS; i++) {
 227                if (points[i] == 0) {
 228                        points[i] = ip;
 229                        break;
 230                }
 231                if (points[i] == ip)
 232                        break;
 233        }
 234
 235        return i;
 236}
 237
 238static void lock_time_inc(struct lock_time *lt, u64 time)
 239{
 240        if (time > lt->max)
 241                lt->max = time;
 242
 243        if (time < lt->min || !lt->nr)
 244                lt->min = time;
 245
 246        lt->total += time;
 247        lt->nr++;
 248}
 249
 250static inline void lock_time_add(struct lock_time *src, struct lock_time *dst)
 251{
 252        if (!src->nr)
 253                return;
 254
 255        if (src->max > dst->max)
 256                dst->max = src->max;
 257
 258        if (src->min < dst->min || !dst->nr)
 259                dst->min = src->min;
 260
 261        dst->total += src->total;
 262        dst->nr += src->nr;
 263}
 264
 265struct lock_class_stats lock_stats(struct lock_class *class)
 266{
 267        struct lock_class_stats stats;
 268        int cpu, i;
 269
 270        memset(&stats, 0, sizeof(struct lock_class_stats));
 271        for_each_possible_cpu(cpu) {
 272                struct lock_class_stats *pcs =
 273                        &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
 274
 275                for (i = 0; i < ARRAY_SIZE(stats.contention_point); i++)
 276                        stats.contention_point[i] += pcs->contention_point[i];
 277
 278                for (i = 0; i < ARRAY_SIZE(stats.contending_point); i++)
 279                        stats.contending_point[i] += pcs->contending_point[i];
 280
 281                lock_time_add(&pcs->read_waittime, &stats.read_waittime);
 282                lock_time_add(&pcs->write_waittime, &stats.write_waittime);
 283
 284                lock_time_add(&pcs->read_holdtime, &stats.read_holdtime);
 285                lock_time_add(&pcs->write_holdtime, &stats.write_holdtime);
 286
 287                for (i = 0; i < ARRAY_SIZE(stats.bounces); i++)
 288                        stats.bounces[i] += pcs->bounces[i];
 289        }
 290
 291        return stats;
 292}
 293
 294void clear_lock_stats(struct lock_class *class)
 295{
 296        int cpu;
 297
 298        for_each_possible_cpu(cpu) {
 299                struct lock_class_stats *cpu_stats =
 300                        &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
 301
 302                memset(cpu_stats, 0, sizeof(struct lock_class_stats));
 303        }
 304        memset(class->contention_point, 0, sizeof(class->contention_point));
 305        memset(class->contending_point, 0, sizeof(class->contending_point));
 306}
 307
 308static struct lock_class_stats *get_lock_stats(struct lock_class *class)
 309{
 310        return &this_cpu_ptr(cpu_lock_stats)[class - lock_classes];
 311}
 312
 313static void lock_release_holdtime(struct held_lock *hlock)
 314{
 315        struct lock_class_stats *stats;
 316        u64 holdtime;
 317
 318        if (!lock_stat)
 319                return;
 320
 321        holdtime = lockstat_clock() - hlock->holdtime_stamp;
 322
 323        stats = get_lock_stats(hlock_class(hlock));
 324        if (hlock->read)
 325                lock_time_inc(&stats->read_holdtime, holdtime);
 326        else
 327                lock_time_inc(&stats->write_holdtime, holdtime);
 328}
 329#else
 330static inline void lock_release_holdtime(struct held_lock *hlock)
 331{
 332}
 333#endif
 334
 335/*
 336 * We keep a global list of all lock classes. The list is only accessed with
 337 * the lockdep spinlock lock held. free_lock_classes is a list with free
 338 * elements. These elements are linked together by the lock_entry member in
 339 * struct lock_class.
 340 */
 341LIST_HEAD(all_lock_classes);
 342static LIST_HEAD(free_lock_classes);
 343
 344/**
 345 * struct pending_free - information about data structures about to be freed
 346 * @zapped: Head of a list with struct lock_class elements.
 347 * @lock_chains_being_freed: Bitmap that indicates which lock_chains[] elements
 348 *      are about to be freed.
 349 */
 350struct pending_free {
 351        struct list_head zapped;
 352        DECLARE_BITMAP(lock_chains_being_freed, MAX_LOCKDEP_CHAINS);
 353};
 354
 355/**
 356 * struct delayed_free - data structures used for delayed freeing
 357 *
 358 * A data structure for delayed freeing of data structures that may be
 359 * accessed by RCU readers at the time these were freed.
 360 *
 361 * @rcu_head:  Used to schedule an RCU callback for freeing data structures.
 362 * @index:     Index of @pf to which freed data structures are added.
 363 * @scheduled: Whether or not an RCU callback has been scheduled.
 364 * @pf:        Array with information about data structures about to be freed.
 365 */
 366static struct delayed_free {
 367        struct rcu_head         rcu_head;
 368        int                     index;
 369        int                     scheduled;
 370        struct pending_free     pf[2];
 371} delayed_free;
 372
 373/*
 374 * The lockdep classes are in a hash-table as well, for fast lookup:
 375 */
 376#define CLASSHASH_BITS          (MAX_LOCKDEP_KEYS_BITS - 1)
 377#define CLASSHASH_SIZE          (1UL << CLASSHASH_BITS)
 378#define __classhashfn(key)      hash_long((unsigned long)key, CLASSHASH_BITS)
 379#define classhashentry(key)     (classhash_table + __classhashfn((key)))
 380
 381static struct hlist_head classhash_table[CLASSHASH_SIZE];
 382
 383/*
 384 * We put the lock dependency chains into a hash-table as well, to cache
 385 * their existence:
 386 */
 387#define CHAINHASH_BITS          (MAX_LOCKDEP_CHAINS_BITS-1)
 388#define CHAINHASH_SIZE          (1UL << CHAINHASH_BITS)
 389#define __chainhashfn(chain)    hash_long(chain, CHAINHASH_BITS)
 390#define chainhashentry(chain)   (chainhash_table + __chainhashfn((chain)))
 391
 392static struct hlist_head chainhash_table[CHAINHASH_SIZE];
 393
 394/*
 395 * the id of held_lock
 396 */
 397static inline u16 hlock_id(struct held_lock *hlock)
 398{
 399        BUILD_BUG_ON(MAX_LOCKDEP_KEYS_BITS + 2 > 16);
 400
 401        return (hlock->class_idx | (hlock->read << MAX_LOCKDEP_KEYS_BITS));
 402}
 403
 404static inline unsigned int chain_hlock_class_idx(u16 hlock_id)
 405{
 406        return hlock_id & (MAX_LOCKDEP_KEYS - 1);
 407}
 408
 409/*
 410 * The hash key of the lock dependency chains is a hash itself too:
 411 * it's a hash of all locks taken up to that lock, including that lock.
 412 * It's a 64-bit hash, because it's important for the keys to be
 413 * unique.
 414 */
 415static inline u64 iterate_chain_key(u64 key, u32 idx)
 416{
 417        u32 k0 = key, k1 = key >> 32;
 418
 419        __jhash_mix(idx, k0, k1); /* Macro that modifies arguments! */
 420
 421        return k0 | (u64)k1 << 32;
 422}
 423
 424void lockdep_init_task(struct task_struct *task)
 425{
 426        task->lockdep_depth = 0; /* no locks held yet */
 427        task->curr_chain_key = INITIAL_CHAIN_KEY;
 428        task->lockdep_recursion = 0;
 429}
 430
 431static __always_inline void lockdep_recursion_inc(void)
 432{
 433        __this_cpu_inc(lockdep_recursion);
 434}
 435
 436static __always_inline void lockdep_recursion_finish(void)
 437{
 438        if (WARN_ON_ONCE(__this_cpu_dec_return(lockdep_recursion)))
 439                __this_cpu_write(lockdep_recursion, 0);
 440}
 441
 442void lockdep_set_selftest_task(struct task_struct *task)
 443{
 444        lockdep_selftest_task_struct = task;
 445}
 446
 447/*
 448 * Debugging switches:
 449 */
 450
 451#define VERBOSE                 0
 452#define VERY_VERBOSE            0
 453
 454#if VERBOSE
 455# define HARDIRQ_VERBOSE        1
 456# define SOFTIRQ_VERBOSE        1
 457#else
 458# define HARDIRQ_VERBOSE        0
 459# define SOFTIRQ_VERBOSE        0
 460#endif
 461
 462#if VERBOSE || HARDIRQ_VERBOSE || SOFTIRQ_VERBOSE
 463/*
 464 * Quick filtering for interesting events:
 465 */
 466static int class_filter(struct lock_class *class)
 467{
 468#if 0
 469        /* Example */
 470        if (class->name_version == 1 &&
 471                        !strcmp(class->name, "lockname"))
 472                return 1;
 473        if (class->name_version == 1 &&
 474                        !strcmp(class->name, "&struct->lockfield"))
 475                return 1;
 476#endif
 477        /* Filter everything else. 1 would be to allow everything else */
 478        return 0;
 479}
 480#endif
 481
 482static int verbose(struct lock_class *class)
 483{
 484#if VERBOSE
 485        return class_filter(class);
 486#endif
 487        return 0;
 488}
 489
 490static void print_lockdep_off(const char *bug_msg)
 491{
 492        printk(KERN_DEBUG "%s\n", bug_msg);
 493        printk(KERN_DEBUG "turning off the locking correctness validator.\n");
 494#ifdef CONFIG_LOCK_STAT
 495        printk(KERN_DEBUG "Please attach the output of /proc/lock_stat to the bug report\n");
 496#endif
 497}
 498
 499unsigned long nr_stack_trace_entries;
 500
 501#ifdef CONFIG_PROVE_LOCKING
 502/**
 503 * struct lock_trace - single stack backtrace
 504 * @hash_entry: Entry in a stack_trace_hash[] list.
 505 * @hash:       jhash() of @entries.
 506 * @nr_entries: Number of entries in @entries.
 507 * @entries:    Actual stack backtrace.
 508 */
 509struct lock_trace {
 510        struct hlist_node       hash_entry;
 511        u32                     hash;
 512        u32                     nr_entries;
 513        unsigned long           entries[] __aligned(sizeof(unsigned long));
 514};
 515#define LOCK_TRACE_SIZE_IN_LONGS                                \
 516        (sizeof(struct lock_trace) / sizeof(unsigned long))
 517/*
 518 * Stack-trace: sequence of lock_trace structures. Protected by the graph_lock.
 519 */
 520static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];
 521static struct hlist_head stack_trace_hash[STACK_TRACE_HASH_SIZE];
 522
 523static bool traces_identical(struct lock_trace *t1, struct lock_trace *t2)
 524{
 525        return t1->hash == t2->hash && t1->nr_entries == t2->nr_entries &&
 526                memcmp(t1->entries, t2->entries,
 527                       t1->nr_entries * sizeof(t1->entries[0])) == 0;
 528}
 529
 530static struct lock_trace *save_trace(void)
 531{
 532        struct lock_trace *trace, *t2;
 533        struct hlist_head *hash_head;
 534        u32 hash;
 535        int max_entries;
 536
 537        BUILD_BUG_ON_NOT_POWER_OF_2(STACK_TRACE_HASH_SIZE);
 538        BUILD_BUG_ON(LOCK_TRACE_SIZE_IN_LONGS >= MAX_STACK_TRACE_ENTRIES);
 539
 540        trace = (struct lock_trace *)(stack_trace + nr_stack_trace_entries);
 541        max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries -
 542                LOCK_TRACE_SIZE_IN_LONGS;
 543
 544        if (max_entries <= 0) {
 545                if (!debug_locks_off_graph_unlock())
 546                        return NULL;
 547
 548                print_lockdep_off("BUG: MAX_STACK_TRACE_ENTRIES too low!");
 549                dump_stack();
 550
 551                return NULL;
 552        }
 553        trace->nr_entries = stack_trace_save(trace->entries, max_entries, 3);
 554
 555        hash = jhash(trace->entries, trace->nr_entries *
 556                     sizeof(trace->entries[0]), 0);
 557        trace->hash = hash;
 558        hash_head = stack_trace_hash + (hash & (STACK_TRACE_HASH_SIZE - 1));
 559        hlist_for_each_entry(t2, hash_head, hash_entry) {
 560                if (traces_identical(trace, t2))
 561                        return t2;
 562        }
 563        nr_stack_trace_entries += LOCK_TRACE_SIZE_IN_LONGS + trace->nr_entries;
 564        hlist_add_head(&trace->hash_entry, hash_head);
 565
 566        return trace;
 567}
 568
 569/* Return the number of stack traces in the stack_trace[] array. */
 570u64 lockdep_stack_trace_count(void)
 571{
 572        struct lock_trace *trace;
 573        u64 c = 0;
 574        int i;
 575
 576        for (i = 0; i < ARRAY_SIZE(stack_trace_hash); i++) {
 577                hlist_for_each_entry(trace, &stack_trace_hash[i], hash_entry) {
 578                        c++;
 579                }
 580        }
 581
 582        return c;
 583}
 584
 585/* Return the number of stack hash chains that have at least one stack trace. */
 586u64 lockdep_stack_hash_count(void)
 587{
 588        u64 c = 0;
 589        int i;
 590
 591        for (i = 0; i < ARRAY_SIZE(stack_trace_hash); i++)
 592                if (!hlist_empty(&stack_trace_hash[i]))
 593                        c++;
 594
 595        return c;
 596}
 597#endif
 598
 599unsigned int nr_hardirq_chains;
 600unsigned int nr_softirq_chains;
 601unsigned int nr_process_chains;
 602unsigned int max_lockdep_depth;
 603
 604#ifdef CONFIG_DEBUG_LOCKDEP
 605/*
 606 * Various lockdep statistics:
 607 */
 608DEFINE_PER_CPU(struct lockdep_stats, lockdep_stats);
 609#endif
 610
 611#ifdef CONFIG_PROVE_LOCKING
 612/*
 613 * Locking printouts:
 614 */
 615
 616#define __USAGE(__STATE)                                                \
 617        [LOCK_USED_IN_##__STATE] = "IN-"__stringify(__STATE)"-W",       \
 618        [LOCK_ENABLED_##__STATE] = __stringify(__STATE)"-ON-W",         \
 619        [LOCK_USED_IN_##__STATE##_READ] = "IN-"__stringify(__STATE)"-R",\
 620        [LOCK_ENABLED_##__STATE##_READ] = __stringify(__STATE)"-ON-R",
 621
 622static const char *usage_str[] =
 623{
 624#define LOCKDEP_STATE(__STATE) __USAGE(__STATE)
 625#include "lockdep_states.h"
 626#undef LOCKDEP_STATE
 627        [LOCK_USED] = "INITIAL USE",
 628        [LOCK_USED_READ] = "INITIAL READ USE",
 629        /* abused as string storage for verify_lock_unused() */
 630        [LOCK_USAGE_STATES] = "IN-NMI",
 631};
 632#endif
 633
 634const char *__get_key_name(const struct lockdep_subclass_key *key, char *str)
 635{
 636        return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str);
 637}
 638
 639static inline unsigned long lock_flag(enum lock_usage_bit bit)
 640{
 641        return 1UL << bit;
 642}
 643
 644static char get_usage_char(struct lock_class *class, enum lock_usage_bit bit)
 645{
 646        /*
 647         * The usage character defaults to '.' (i.e., irqs disabled and not in
 648         * irq context), which is the safest usage category.
 649         */
 650        char c = '.';
 651
 652        /*
 653         * The order of the following usage checks matters, which will
 654         * result in the outcome character as follows:
 655         *
 656         * - '+': irq is enabled and not in irq context
 657         * - '-': in irq context and irq is disabled
 658         * - '?': in irq context and irq is enabled
 659         */
 660        if (class->usage_mask & lock_flag(bit + LOCK_USAGE_DIR_MASK)) {
 661                c = '+';
 662                if (class->usage_mask & lock_flag(bit))
 663                        c = '?';
 664        } else if (class->usage_mask & lock_flag(bit))
 665                c = '-';
 666
 667        return c;
 668}
 669
 670void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS])
 671{
 672        int i = 0;
 673
 674#define LOCKDEP_STATE(__STATE)                                          \
 675        usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE);     \
 676        usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE##_READ);
 677#include "lockdep_states.h"
 678#undef LOCKDEP_STATE
 679
 680        usage[i] = '\0';
 681}
 682
 683static void __print_lock_name(struct lock_class *class)
 684{
 685        char str[KSYM_NAME_LEN];
 686        const char *name;
 687
 688        name = class->name;
 689        if (!name) {
 690                name = __get_key_name(class->key, str);
 691                printk(KERN_CONT "%s", name);
 692        } else {
 693                printk(KERN_CONT "%s", name);
 694                if (class->name_version > 1)
 695                        printk(KERN_CONT "#%d", class->name_version);
 696                if (class->subclass)
 697                        printk(KERN_CONT "/%d", class->subclass);
 698        }
 699}
 700
 701static void print_lock_name(struct lock_class *class)
 702{
 703        char usage[LOCK_USAGE_CHARS];
 704
 705        get_usage_chars(class, usage);
 706
 707        printk(KERN_CONT " (");
 708        __print_lock_name(class);
 709        printk(KERN_CONT "){%s}-{%d:%d}", usage,
 710                        class->wait_type_outer ?: class->wait_type_inner,
 711                        class->wait_type_inner);
 712}
 713
 714static void print_lockdep_cache(struct lockdep_map *lock)
 715{
 716        const char *name;
 717        char str[KSYM_NAME_LEN];
 718
 719        name = lock->name;
 720        if (!name)
 721                name = __get_key_name(lock->key->subkeys, str);
 722
 723        printk(KERN_CONT "%s", name);
 724}
 725
 726static void print_lock(struct held_lock *hlock)
 727{
 728        /*
 729         * We can be called locklessly through debug_show_all_locks() so be
 730         * extra careful, the hlock might have been released and cleared.
 731         *
 732         * If this indeed happens, lets pretend it does not hurt to continue
 733         * to print the lock unless the hlock class_idx does not point to a
 734         * registered class. The rationale here is: since we don't attempt
 735         * to distinguish whether we are in this situation, if it just
 736         * happened we can't count on class_idx to tell either.
 737         */
 738        struct lock_class *lock = hlock_class(hlock);
 739
 740        if (!lock) {
 741                printk(KERN_CONT "<RELEASED>\n");
 742                return;
 743        }
 744
 745        printk(KERN_CONT "%px", hlock->instance);
 746        print_lock_name(lock);
 747        printk(KERN_CONT ", at: %pS\n", (void *)hlock->acquire_ip);
 748}
 749
 750static void lockdep_print_held_locks(struct task_struct *p)
 751{
 752        int i, depth = READ_ONCE(p->lockdep_depth);
 753
 754        if (!depth)
 755                printk("no locks held by %s/%d.\n", p->comm, task_pid_nr(p));
 756        else
 757                printk("%d lock%s held by %s/%d:\n", depth,
 758                       depth > 1 ? "s" : "", p->comm, task_pid_nr(p));
 759        /*
 760         * It's not reliable to print a task's held locks if it's not sleeping
 761         * and it's not the current task.
 762         */
 763        if (p != current && task_is_running(p))
 764                return;
 765        for (i = 0; i < depth; i++) {
 766                printk(" #%d: ", i);
 767                print_lock(p->held_locks + i);
 768        }
 769}
 770
 771static void print_kernel_ident(void)
 772{
 773        printk("%s %.*s %s\n", init_utsname()->release,
 774                (int)strcspn(init_utsname()->version, " "),
 775                init_utsname()->version,
 776                print_tainted());
 777}
 778
 779static int very_verbose(struct lock_class *class)
 780{
 781#if VERY_VERBOSE
 782        return class_filter(class);
 783#endif
 784        return 0;
 785}
 786
 787/*
 788 * Is this the address of a static object:
 789 */
 790#ifdef __KERNEL__
 791static int static_obj(const void *obj)
 792{
 793        unsigned long start = (unsigned long) &_stext,
 794                      end   = (unsigned long) &_end,
 795                      addr  = (unsigned long) obj;
 796
 797        if (arch_is_kernel_initmem_freed(addr))
 798                return 0;
 799
 800        /*
 801         * static variable?
 802         */
 803        if ((addr >= start) && (addr < end))
 804                return 1;
 805
 806        if (arch_is_kernel_data(addr))
 807                return 1;
 808
 809        /*
 810         * in-kernel percpu var?
 811         */
 812        if (is_kernel_percpu_address(addr))
 813                return 1;
 814
 815        /*
 816         * module static or percpu var?
 817         */
 818        return is_module_address(addr) || is_module_percpu_address(addr);
 819}
 820#endif
 821
 822/*
 823 * To make lock name printouts unique, we calculate a unique
 824 * class->name_version generation counter. The caller must hold the graph
 825 * lock.
 826 */
 827static int count_matching_names(struct lock_class *new_class)
 828{
 829        struct lock_class *class;
 830        int count = 0;
 831
 832        if (!new_class->name)
 833                return 0;
 834
 835        list_for_each_entry(class, &all_lock_classes, lock_entry) {
 836                if (new_class->key - new_class->subclass == class->key)
 837                        return class->name_version;
 838                if (class->name && !strcmp(class->name, new_class->name))
 839                        count = max(count, class->name_version);
 840        }
 841
 842        return count + 1;
 843}
 844
 845/* used from NMI context -- must be lockless */
 846static noinstr struct lock_class *
 847look_up_lock_class(const struct lockdep_map *lock, unsigned int subclass)
 848{
 849        struct lockdep_subclass_key *key;
 850        struct hlist_head *hash_head;
 851        struct lock_class *class;
 852
 853        if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
 854                instrumentation_begin();
 855                debug_locks_off();
 856                printk(KERN_ERR
 857                        "BUG: looking up invalid subclass: %u\n", subclass);
 858                printk(KERN_ERR
 859                        "turning off the locking correctness validator.\n");
 860                dump_stack();
 861                instrumentation_end();
 862                return NULL;
 863        }
 864
 865        /*
 866         * If it is not initialised then it has never been locked,
 867         * so it won't be present in the hash table.
 868         */
 869        if (unlikely(!lock->key))
 870                return NULL;
 871
 872        /*
 873         * NOTE: the class-key must be unique. For dynamic locks, a static
 874         * lock_class_key variable is passed in through the mutex_init()
 875         * (or spin_lock_init()) call - which acts as the key. For static
 876         * locks we use the lock object itself as the key.
 877         */
 878        BUILD_BUG_ON(sizeof(struct lock_class_key) >
 879                        sizeof(struct lockdep_map));
 880
 881        key = lock->key->subkeys + subclass;
 882
 883        hash_head = classhashentry(key);
 884
 885        /*
 886         * We do an RCU walk of the hash, see lockdep_free_key_range().
 887         */
 888        if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
 889                return NULL;
 890
 891        hlist_for_each_entry_rcu(class, hash_head, hash_entry) {
 892                if (class->key == key) {
 893                        /*
 894                         * Huh! same key, different name? Did someone trample
 895                         * on some memory? We're most confused.
 896                         */
 897                        WARN_ON_ONCE(class->name != lock->name &&
 898                                     lock->key != &__lockdep_no_validate__);
 899                        return class;
 900                }
 901        }
 902
 903        return NULL;
 904}
 905
 906/*
 907 * Static locks do not have their class-keys yet - for them the key is
 908 * the lock object itself. If the lock is in the per cpu area, the
 909 * canonical address of the lock (per cpu offset removed) is used.
 910 */
 911static bool assign_lock_key(struct lockdep_map *lock)
 912{
 913        unsigned long can_addr, addr = (unsigned long)lock;
 914
 915#ifdef __KERNEL__
 916        /*
 917         * lockdep_free_key_range() assumes that struct lock_class_key
 918         * objects do not overlap. Since we use the address of lock
 919         * objects as class key for static objects, check whether the
 920         * size of lock_class_key objects does not exceed the size of
 921         * the smallest lock object.
 922         */
 923        BUILD_BUG_ON(sizeof(struct lock_class_key) > sizeof(raw_spinlock_t));
 924#endif
 925
 926        if (__is_kernel_percpu_address(addr, &can_addr))
 927                lock->key = (void *)can_addr;
 928        else if (__is_module_percpu_address(addr, &can_addr))
 929                lock->key = (void *)can_addr;
 930        else if (static_obj(lock))
 931                lock->key = (void *)lock;
 932        else {
 933                /* Debug-check: all keys must be persistent! */
 934                debug_locks_off();
 935                pr_err("INFO: trying to register non-static key.\n");
 936                pr_err("The code is fine but needs lockdep annotation, or maybe\n");
 937                pr_err("you didn't initialize this object before use?\n");
 938                pr_err("turning off the locking correctness validator.\n");
 939                dump_stack();
 940                return false;
 941        }
 942
 943        return true;
 944}
 945
 946#ifdef CONFIG_DEBUG_LOCKDEP
 947
 948/* Check whether element @e occurs in list @h */
 949static bool in_list(struct list_head *e, struct list_head *h)
 950{
 951        struct list_head *f;
 952
 953        list_for_each(f, h) {
 954                if (e == f)
 955                        return true;
 956        }
 957
 958        return false;
 959}
 960
 961/*
 962 * Check whether entry @e occurs in any of the locks_after or locks_before
 963 * lists.
 964 */
 965static bool in_any_class_list(struct list_head *e)
 966{
 967        struct lock_class *class;
 968        int i;
 969
 970        for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
 971                class = &lock_classes[i];
 972                if (in_list(e, &class->locks_after) ||
 973                    in_list(e, &class->locks_before))
 974                        return true;
 975        }
 976        return false;
 977}
 978
 979static bool class_lock_list_valid(struct lock_class *c, struct list_head *h)
 980{
 981        struct lock_list *e;
 982
 983        list_for_each_entry(e, h, entry) {
 984                if (e->links_to != c) {
 985                        printk(KERN_INFO "class %s: mismatch for lock entry %ld; class %s <> %s",
 986                               c->name ? : "(?)",
 987                               (unsigned long)(e - list_entries),
 988                               e->links_to && e->links_to->name ?
 989                               e->links_to->name : "(?)",
 990                               e->class && e->class->name ? e->class->name :
 991                               "(?)");
 992                        return false;
 993                }
 994        }
 995        return true;
 996}
 997
 998#ifdef CONFIG_PROVE_LOCKING
 999static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
1000#endif
1001
1002static bool check_lock_chain_key(struct lock_chain *chain)
1003{
1004#ifdef CONFIG_PROVE_LOCKING
1005        u64 chain_key = INITIAL_CHAIN_KEY;
1006        int i;
1007
1008        for (i = chain->base; i < chain->base + chain->depth; i++)
1009                chain_key = iterate_chain_key(chain_key, chain_hlocks[i]);
1010        /*
1011         * The 'unsigned long long' casts avoid that a compiler warning
1012         * is reported when building tools/lib/lockdep.
1013         */
1014        if (chain->chain_key != chain_key) {
1015                printk(KERN_INFO "chain %lld: key %#llx <> %#llx\n",
1016                       (unsigned long long)(chain - lock_chains),
1017                       (unsigned long long)chain->chain_key,
1018                       (unsigned long long)chain_key);
1019                return false;
1020        }
1021#endif
1022        return true;
1023}
1024
1025static bool in_any_zapped_class_list(struct lock_class *class)
1026{
1027        struct pending_free *pf;
1028        int i;
1029
1030        for (i = 0, pf = delayed_free.pf; i < ARRAY_SIZE(delayed_free.pf); i++, pf++) {
1031                if (in_list(&class->lock_entry, &pf->zapped))
1032                        return true;
1033        }
1034
1035        return false;
1036}
1037
1038static bool __check_data_structures(void)
1039{
1040        struct lock_class *class;
1041        struct lock_chain *chain;
1042        struct hlist_head *head;
1043        struct lock_list *e;
1044        int i;
1045
1046        /* Check whether all classes occur in a lock list. */
1047        for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
1048                class = &lock_classes[i];
1049                if (!in_list(&class->lock_entry, &all_lock_classes) &&
1050                    !in_list(&class->lock_entry, &free_lock_classes) &&
1051                    !in_any_zapped_class_list(class)) {
1052                        printk(KERN_INFO "class %px/%s is not in any class list\n",
1053                               class, class->name ? : "(?)");
1054                        return false;
1055                }
1056        }
1057
1058        /* Check whether all classes have valid lock lists. */
1059        for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
1060                class = &lock_classes[i];
1061                if (!class_lock_list_valid(class, &class->locks_before))
1062                        return false;
1063                if (!class_lock_list_valid(class, &class->locks_after))
1064                        return false;
1065        }
1066
1067        /* Check the chain_key of all lock chains. */
1068        for (i = 0; i < ARRAY_SIZE(chainhash_table); i++) {
1069                head = chainhash_table + i;
1070                hlist_for_each_entry_rcu(chain, head, entry) {
1071                        if (!check_lock_chain_key(chain))
1072                                return false;
1073                }
1074        }
1075
1076        /*
1077         * Check whether all list entries that are in use occur in a class
1078         * lock list.
1079         */
1080        for_each_set_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
1081                e = list_entries + i;
1082                if (!in_any_class_list(&e->entry)) {
1083                        printk(KERN_INFO "list entry %d is not in any class list; class %s <> %s\n",
1084                               (unsigned int)(e - list_entries),
1085                               e->class->name ? : "(?)",
1086                               e->links_to->name ? : "(?)");
1087                        return false;
1088                }
1089        }
1090
1091        /*
1092         * Check whether all list entries that are not in use do not occur in
1093         * a class lock list.
1094         */
1095        for_each_clear_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
1096                e = list_entries + i;
1097                if (in_any_class_list(&e->entry)) {
1098                        printk(KERN_INFO "list entry %d occurs in a class list; class %s <> %s\n",
1099                               (unsigned int)(e - list_entries),
1100                               e->class && e->class->name ? e->class->name :
1101                               "(?)",
1102                               e->links_to && e->links_to->name ?
1103                               e->links_to->name : "(?)");
1104                        return false;
1105                }
1106        }
1107
1108        return true;
1109}
1110
1111int check_consistency = 0;
1112module_param(check_consistency, int, 0644);
1113
1114static void check_data_structures(void)
1115{
1116        static bool once = false;
1117
1118        if (check_consistency && !once) {
1119                if (!__check_data_structures()) {
1120                        once = true;
1121                        WARN_ON(once);
1122                }
1123        }
1124}
1125
1126#else /* CONFIG_DEBUG_LOCKDEP */
1127
1128static inline void check_data_structures(void) { }
1129
1130#endif /* CONFIG_DEBUG_LOCKDEP */
1131
1132static void init_chain_block_buckets(void);
1133
1134/*
1135 * Initialize the lock_classes[] array elements, the free_lock_classes list
1136 * and also the delayed_free structure.
1137 */
1138static void init_data_structures_once(void)
1139{
1140        static bool __read_mostly ds_initialized, rcu_head_initialized;
1141        int i;
1142
1143        if (likely(rcu_head_initialized))
1144                return;
1145
1146        if (system_state >= SYSTEM_SCHEDULING) {
1147                init_rcu_head(&delayed_free.rcu_head);
1148                rcu_head_initialized = true;
1149        }
1150
1151        if (ds_initialized)
1152                return;
1153
1154        ds_initialized = true;
1155
1156        INIT_LIST_HEAD(&delayed_free.pf[0].zapped);
1157        INIT_LIST_HEAD(&delayed_free.pf[1].zapped);
1158
1159        for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
1160                list_add_tail(&lock_classes[i].lock_entry, &free_lock_classes);
1161                INIT_LIST_HEAD(&lock_classes[i].locks_after);
1162                INIT_LIST_HEAD(&lock_classes[i].locks_before);
1163        }
1164        init_chain_block_buckets();
1165}
1166
1167static inline struct hlist_head *keyhashentry(const struct lock_class_key *key)
1168{
1169        unsigned long hash = hash_long((uintptr_t)key, KEYHASH_BITS);
1170
1171        return lock_keys_hash + hash;
1172}
1173
1174/* Register a dynamically allocated key. */
1175void lockdep_register_key(struct lock_class_key *key)
1176{
1177        struct hlist_head *hash_head;
1178        struct lock_class_key *k;
1179        unsigned long flags;
1180
1181        if (WARN_ON_ONCE(static_obj(key)))
1182                return;
1183        hash_head = keyhashentry(key);
1184
1185        raw_local_irq_save(flags);
1186        if (!graph_lock())
1187                goto restore_irqs;
1188        hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
1189                if (WARN_ON_ONCE(k == key))
1190                        goto out_unlock;
1191        }
1192        hlist_add_head_rcu(&key->hash_entry, hash_head);
1193out_unlock:
1194        graph_unlock();
1195restore_irqs:
1196        raw_local_irq_restore(flags);
1197}
1198EXPORT_SYMBOL_GPL(lockdep_register_key);
1199
1200/* Check whether a key has been registered as a dynamic key. */
1201static bool is_dynamic_key(const struct lock_class_key *key)
1202{
1203        struct hlist_head *hash_head;
1204        struct lock_class_key *k;
1205        bool found = false;
1206
1207        if (WARN_ON_ONCE(static_obj(key)))
1208                return false;
1209
1210        /*
1211         * If lock debugging is disabled lock_keys_hash[] may contain
1212         * pointers to memory that has already been freed. Avoid triggering
1213         * a use-after-free in that case by returning early.
1214         */
1215        if (!debug_locks)
1216                return true;
1217
1218        hash_head = keyhashentry(key);
1219
1220        rcu_read_lock();
1221        hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
1222                if (k == key) {
1223                        found = true;
1224                        break;
1225                }
1226        }
1227        rcu_read_unlock();
1228
1229        return found;
1230}
1231
1232/*
1233 * Register a lock's class in the hash-table, if the class is not present
1234 * yet. Otherwise we look it up. We cache the result in the lock object
1235 * itself, so actual lookup of the hash should be once per lock object.
1236 */
1237static struct lock_class *
1238register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
1239{
1240        struct lockdep_subclass_key *key;
1241        struct hlist_head *hash_head;
1242        struct lock_class *class;
1243
1244        DEBUG_LOCKS_WARN_ON(!irqs_disabled());
1245
1246        class = look_up_lock_class(lock, subclass);
1247        if (likely(class))
1248                goto out_set_class_cache;
1249
1250        if (!lock->key) {
1251                if (!assign_lock_key(lock))
1252                        return NULL;
1253        } else if (!static_obj(lock->key) && !is_dynamic_key(lock->key)) {
1254                return NULL;
1255        }
1256
1257        key = lock->key->subkeys + subclass;
1258        hash_head = classhashentry(key);
1259
1260        if (!graph_lock()) {
1261                return NULL;
1262        }
1263        /*
1264         * We have to do the hash-walk again, to avoid races
1265         * with another CPU:
1266         */
1267        hlist_for_each_entry_rcu(class, hash_head, hash_entry) {
1268                if (class->key == key)
1269                        goto out_unlock_set;
1270        }
1271
1272        init_data_structures_once();
1273
1274        /* Allocate a new lock class and add it to the hash. */
1275        class = list_first_entry_or_null(&free_lock_classes, typeof(*class),
1276                                         lock_entry);
1277        if (!class) {
1278                if (!debug_locks_off_graph_unlock()) {
1279                        return NULL;
1280                }
1281
1282                print_lockdep_off("BUG: MAX_LOCKDEP_KEYS too low!");
1283                dump_stack();
1284                return NULL;
1285        }
1286        nr_lock_classes++;
1287        __set_bit(class - lock_classes, lock_classes_in_use);
1288        debug_atomic_inc(nr_unused_locks);
1289        class->key = key;
1290        class->name = lock->name;
1291        class->subclass = subclass;
1292        WARN_ON_ONCE(!list_empty(&class->locks_before));
1293        WARN_ON_ONCE(!list_empty(&class->locks_after));
1294        class->name_version = count_matching_names(class);
1295        class->wait_type_inner = lock->wait_type_inner;
1296        class->wait_type_outer = lock->wait_type_outer;
1297        class->lock_type = lock->lock_type;
1298        /*
1299         * We use RCU's safe list-add method to make
1300         * parallel walking of the hash-list safe:
1301         */
1302        hlist_add_head_rcu(&class->hash_entry, hash_head);
1303        /*
1304         * Remove the class from the free list and add it to the global list
1305         * of classes.
1306         */
1307        list_move_tail(&class->lock_entry, &all_lock_classes);
1308
1309        if (verbose(class)) {
1310                graph_unlock();
1311
1312                printk("\nnew class %px: %s", class->key, class->name);
1313                if (class->name_version > 1)
1314                        printk(KERN_CONT "#%d", class->name_version);
1315                printk(KERN_CONT "\n");
1316                dump_stack();
1317
1318                if (!graph_lock()) {
1319                        return NULL;
1320                }
1321        }
1322out_unlock_set:
1323        graph_unlock();
1324
1325out_set_class_cache:
1326        if (!subclass || force)
1327                lock->class_cache[0] = class;
1328        else if (subclass < NR_LOCKDEP_CACHING_CLASSES)
1329                lock->class_cache[subclass] = class;
1330
1331        /*
1332         * Hash collision, did we smoke some? We found a class with a matching
1333         * hash but the subclass -- which is hashed in -- didn't match.
1334         */
1335        if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))
1336                return NULL;
1337
1338        return class;
1339}
1340
1341#ifdef CONFIG_PROVE_LOCKING
1342/*
1343 * Allocate a lockdep entry. (assumes the graph_lock held, returns
1344 * with NULL on failure)
1345 */
1346static struct lock_list *alloc_list_entry(void)
1347{
1348        int idx = find_first_zero_bit(list_entries_in_use,
1349                                      ARRAY_SIZE(list_entries));
1350
1351        if (idx >= ARRAY_SIZE(list_entries)) {
1352                if (!debug_locks_off_graph_unlock())
1353                        return NULL;
1354
1355                print_lockdep_off("BUG: MAX_LOCKDEP_ENTRIES too low!");
1356                dump_stack();
1357                return NULL;
1358        }
1359        nr_list_entries++;
1360        __set_bit(idx, list_entries_in_use);
1361        return list_entries + idx;
1362}
1363
1364/*
1365 * Add a new dependency to the head of the list:
1366 */
1367static int add_lock_to_list(struct lock_class *this,
1368                            struct lock_class *links_to, struct list_head *head,
1369                            unsigned long ip, u16 distance, u8 dep,
1370                            const struct lock_trace *trace)
1371{
1372        struct lock_list *entry;
1373        /*
1374         * Lock not present yet - get a new dependency struct and
1375         * add it to the list:
1376         */
1377        entry = alloc_list_entry();
1378        if (!entry)
1379                return 0;
1380
1381        entry->class = this;
1382        entry->links_to = links_to;
1383        entry->dep = dep;
1384        entry->distance = distance;
1385        entry->trace = trace;
1386        /*
1387         * Both allocation and removal are done under the graph lock; but
1388         * iteration is under RCU-sched; see look_up_lock_class() and
1389         * lockdep_free_key_range().
1390         */
1391        list_add_tail_rcu(&entry->entry, head);
1392
1393        return 1;
1394}
1395
1396/*
1397 * For good efficiency of modular, we use power of 2
1398 */
1399#define MAX_CIRCULAR_QUEUE_SIZE         (1UL << CONFIG_LOCKDEP_CIRCULAR_QUEUE_BITS)
1400#define CQ_MASK                         (MAX_CIRCULAR_QUEUE_SIZE-1)
1401
1402/*
1403 * The circular_queue and helpers are used to implement graph
1404 * breadth-first search (BFS) algorithm, by which we can determine
1405 * whether there is a path from a lock to another. In deadlock checks,
1406 * a path from the next lock to be acquired to a previous held lock
1407 * indicates that adding the <prev> -> <next> lock dependency will
1408 * produce a circle in the graph. Breadth-first search instead of
1409 * depth-first search is used in order to find the shortest (circular)
1410 * path.
1411 */
1412struct circular_queue {
1413        struct lock_list *element[MAX_CIRCULAR_QUEUE_SIZE];
1414        unsigned int  front, rear;
1415};
1416
1417static struct circular_queue lock_cq;
1418
1419unsigned int max_bfs_queue_depth;
1420
1421static unsigned int lockdep_dependency_gen_id;
1422
1423static inline void __cq_init(struct circular_queue *cq)
1424{
1425        cq->front = cq->rear = 0;
1426        lockdep_dependency_gen_id++;
1427}
1428
1429static inline int __cq_empty(struct circular_queue *cq)
1430{
1431        return (cq->front == cq->rear);
1432}
1433
1434static inline int __cq_full(struct circular_queue *cq)
1435{
1436        return ((cq->rear + 1) & CQ_MASK) == cq->front;
1437}
1438
1439static inline int __cq_enqueue(struct circular_queue *cq, struct lock_list *elem)
1440{
1441        if (__cq_full(cq))
1442                return -1;
1443
1444        cq->element[cq->rear] = elem;
1445        cq->rear = (cq->rear + 1) & CQ_MASK;
1446        return 0;
1447}
1448
1449/*
1450 * Dequeue an element from the circular_queue, return a lock_list if
1451 * the queue is not empty, or NULL if otherwise.
1452 */
1453static inline struct lock_list * __cq_dequeue(struct circular_queue *cq)
1454{
1455        struct lock_list * lock;
1456
1457        if (__cq_empty(cq))
1458                return NULL;
1459
1460        lock = cq->element[cq->front];
1461        cq->front = (cq->front + 1) & CQ_MASK;
1462
1463        return lock;
1464}
1465
1466static inline unsigned int  __cq_get_elem_count(struct circular_queue *cq)
1467{
1468        return (cq->rear - cq->front) & CQ_MASK;
1469}
1470
1471static inline void mark_lock_accessed(struct lock_list *lock)
1472{
1473        lock->class->dep_gen_id = lockdep_dependency_gen_id;
1474}
1475
1476static inline void visit_lock_entry(struct lock_list *lock,
1477                                    struct lock_list *parent)
1478{
1479        lock->parent = parent;
1480}
1481
1482static inline unsigned long lock_accessed(struct lock_list *lock)
1483{
1484        return lock->class->dep_gen_id == lockdep_dependency_gen_id;
1485}
1486
1487static inline struct lock_list *get_lock_parent(struct lock_list *child)
1488{
1489        return child->parent;
1490}
1491
1492static inline int get_lock_depth(struct lock_list *child)
1493{
1494        int depth = 0;
1495        struct lock_list *parent;
1496
1497        while ((parent = get_lock_parent(child))) {
1498                child = parent;
1499                depth++;
1500        }
1501        return depth;
1502}
1503
1504/*
1505 * Return the forward or backward dependency list.
1506 *
1507 * @lock:   the lock_list to get its class's dependency list
1508 * @offset: the offset to struct lock_class to determine whether it is
1509 *          locks_after or locks_before
1510 */
1511static inline struct list_head *get_dep_list(struct lock_list *lock, int offset)
1512{
1513        void *lock_class = lock->class;
1514
1515        return lock_class + offset;
1516}
1517/*
1518 * Return values of a bfs search:
1519 *
1520 * BFS_E* indicates an error
1521 * BFS_R* indicates a result (match or not)
1522 *
1523 * BFS_EINVALIDNODE: Find a invalid node in the graph.
1524 *
1525 * BFS_EQUEUEFULL: The queue is full while doing the bfs.
1526 *
1527 * BFS_RMATCH: Find the matched node in the graph, and put that node into
1528 *             *@target_entry.
1529 *
1530 * BFS_RNOMATCH: Haven't found the matched node and keep *@target_entry
1531 *               _unchanged_.
1532 */
1533enum bfs_result {
1534        BFS_EINVALIDNODE = -2,
1535        BFS_EQUEUEFULL = -1,
1536        BFS_RMATCH = 0,
1537        BFS_RNOMATCH = 1,
1538};
1539
1540/*
1541 * bfs_result < 0 means error
1542 */
1543static inline bool bfs_error(enum bfs_result res)
1544{
1545        return res < 0;
1546}
1547
1548/*
1549 * DEP_*_BIT in lock_list::dep
1550 *
1551 * For dependency @prev -> @next:
1552 *
1553 *   SR: @prev is shared reader (->read != 0) and @next is recursive reader
1554 *       (->read == 2)
1555 *   ER: @prev is exclusive locker (->read == 0) and @next is recursive reader
1556 *   SN: @prev is shared reader and @next is non-recursive locker (->read != 2)
1557 *   EN: @prev is exclusive locker and @next is non-recursive locker
1558 *
1559 * Note that we define the value of DEP_*_BITs so that:
1560 *   bit0 is prev->read == 0
1561 *   bit1 is next->read != 2
1562 */
1563#define DEP_SR_BIT (0 + (0 << 1)) /* 0 */
1564#define DEP_ER_BIT (1 + (0 << 1)) /* 1 */
1565#define DEP_SN_BIT (0 + (1 << 1)) /* 2 */
1566#define DEP_EN_BIT (1 + (1 << 1)) /* 3 */
1567
1568#define DEP_SR_MASK (1U << (DEP_SR_BIT))
1569#define DEP_ER_MASK (1U << (DEP_ER_BIT))
1570#define DEP_SN_MASK (1U << (DEP_SN_BIT))
1571#define DEP_EN_MASK (1U << (DEP_EN_BIT))
1572
1573static inline unsigned int
1574__calc_dep_bit(struct held_lock *prev, struct held_lock *next)
1575{
1576        return (prev->read == 0) + ((next->read != 2) << 1);
1577}
1578
1579static inline u8 calc_dep(struct held_lock *prev, struct held_lock *next)
1580{
1581        return 1U << __calc_dep_bit(prev, next);
1582}
1583
1584/*
1585 * calculate the dep_bit for backwards edges. We care about whether @prev is
1586 * shared and whether @next is recursive.
1587 */
1588static inline unsigned int
1589__calc_dep_bitb(struct held_lock *prev, struct held_lock *next)
1590{
1591        return (next->read != 2) + ((prev->read == 0) << 1);
1592}
1593
1594static inline u8 calc_depb(struct held_lock *prev, struct held_lock *next)
1595{
1596        return 1U << __calc_dep_bitb(prev, next);
1597}
1598
1599/*
1600 * Initialize a lock_list entry @lock belonging to @class as the root for a BFS
1601 * search.
1602 */
1603static inline void __bfs_init_root(struct lock_list *lock,
1604                                   struct lock_class *class)
1605{
1606        lock->class = class;
1607        lock->parent = NULL;
1608        lock->only_xr = 0;
1609}
1610
1611/*
1612 * Initialize a lock_list entry @lock based on a lock acquisition @hlock as the
1613 * root for a BFS search.
1614 *
1615 * ->only_xr of the initial lock node is set to @hlock->read == 2, to make sure
1616 * that <prev> -> @hlock and @hlock -> <whatever __bfs() found> is not -(*R)->
1617 * and -(S*)->.
1618 */
1619static inline void bfs_init_root(struct lock_list *lock,
1620                                 struct held_lock *hlock)
1621{
1622        __bfs_init_root(lock, hlock_class(hlock));
1623        lock->only_xr = (hlock->read == 2);
1624}
1625
1626/*
1627 * Similar to bfs_init_root() but initialize the root for backwards BFS.
1628 *
1629 * ->only_xr of the initial lock node is set to @hlock->read != 0, to make sure
1630 * that <next> -> @hlock and @hlock -> <whatever backwards BFS found> is not
1631 * -(*S)-> and -(R*)-> (reverse order of -(*R)-> and -(S*)->).
1632 */
1633static inline void bfs_init_rootb(struct lock_list *lock,
1634                                  struct held_lock *hlock)
1635{
1636        __bfs_init_root(lock, hlock_class(hlock));
1637        lock->only_xr = (hlock->read != 0);
1638}
1639
1640static inline struct lock_list *__bfs_next(struct lock_list *lock, int offset)
1641{
1642        if (!lock || !lock->parent)
1643                return NULL;
1644
1645        return list_next_or_null_rcu(get_dep_list(lock->parent, offset),
1646                                     &lock->entry, struct lock_list, entry);
1647}
1648
1649/*
1650 * Breadth-First Search to find a strong path in the dependency graph.
1651 *
1652 * @source_entry: the source of the path we are searching for.
1653 * @data: data used for the second parameter of @match function
1654 * @match: match function for the search
1655 * @target_entry: pointer to the target of a matched path
1656 * @offset: the offset to struct lock_class to determine whether it is
1657 *          locks_after or locks_before
1658 *
1659 * We may have multiple edges (considering different kinds of dependencies,
1660 * e.g. ER and SN) between two nodes in the dependency graph. But
1661 * only the strong dependency path in the graph is relevant to deadlocks. A
1662 * strong dependency path is a dependency path that doesn't have two adjacent
1663 * dependencies as -(*R)-> -(S*)->, please see:
1664 *
1665 *         Documentation/locking/lockdep-design.rst
1666 *
1667 * for more explanation of the definition of strong dependency paths
1668 *
1669 * In __bfs(), we only traverse in the strong dependency path:
1670 *
1671 *     In lock_list::only_xr, we record whether the previous dependency only
1672 *     has -(*R)-> in the search, and if it does (prev only has -(*R)->), we
1673 *     filter out any -(S*)-> in the current dependency and after that, the
1674 *     ->only_xr is set according to whether we only have -(*R)-> left.
1675 */
1676static enum bfs_result __bfs(struct lock_list *source_entry,
1677                             void *data,
1678                             bool (*match)(struct lock_list *entry, void *data),
1679                             bool (*skip)(struct lock_list *entry, void *data),
1680                             struct lock_list **target_entry,
1681                             int offset)
1682{
1683        struct circular_queue *cq = &lock_cq;
1684        struct lock_list *lock = NULL;
1685        struct lock_list *entry;
1686        struct list_head *head;
1687        unsigned int cq_depth;
1688        bool first;
1689
1690        lockdep_assert_locked();
1691
1692        __cq_init(cq);
1693        __cq_enqueue(cq, source_entry);
1694
1695        while ((lock = __bfs_next(lock, offset)) || (lock = __cq_dequeue(cq))) {
1696                if (!lock->class)
1697                        return BFS_EINVALIDNODE;
1698
1699                /*
1700                 * Step 1: check whether we already finish on this one.
1701                 *
1702                 * If we have visited all the dependencies from this @lock to
1703                 * others (iow, if we have visited all lock_list entries in
1704                 * @lock->class->locks_{after,before}) we skip, otherwise go
1705                 * and visit all the dependencies in the list and mark this
1706                 * list accessed.
1707                 */
1708                if (lock_accessed(lock))
1709                        continue;
1710                else
1711                        mark_lock_accessed(lock);
1712
1713                /*
1714                 * Step 2: check whether prev dependency and this form a strong
1715                 *         dependency path.
1716                 */
1717                if (lock->parent) { /* Parent exists, check prev dependency */
1718                        u8 dep = lock->dep;
1719                        bool prev_only_xr = lock->parent->only_xr;
1720
1721                        /*
1722                         * Mask out all -(S*)-> if we only have *R in previous
1723                         * step, because -(*R)-> -(S*)-> don't make up a strong
1724                         * dependency.
1725                         */
1726                        if (prev_only_xr)
1727                                dep &= ~(DEP_SR_MASK | DEP_SN_MASK);
1728
1729                        /* If nothing left, we skip */
1730                        if (!dep)
1731                                continue;
1732
1733                        /* If there are only -(*R)-> left, set that for the next step */
1734                        lock->only_xr = !(dep & (DEP_SN_MASK | DEP_EN_MASK));
1735                }
1736
1737                /*
1738                 * Step 3: we haven't visited this and there is a strong
1739                 *         dependency path to this, so check with @match.
1740                 *         If @skip is provide and returns true, we skip this
1741                 *         lock (and any path this lock is in).
1742                 */
1743                if (skip && skip(lock, data))
1744                        continue;
1745
1746                if (match(lock, data)) {
1747                        *target_entry = lock;
1748                        return BFS_RMATCH;
1749                }
1750
1751                /*
1752                 * Step 4: if not match, expand the path by adding the
1753                 *         forward or backwards dependencies in the search
1754                 *
1755                 */
1756                first = true;
1757                head = get_dep_list(lock, offset);
1758                list_for_each_entry_rcu(entry, head, entry) {
1759                        visit_lock_entry(entry, lock);
1760
1761                        /*
1762                         * Note we only enqueue the first of the list into the
1763                         * queue, because we can always find a sibling
1764                         * dependency from one (see __bfs_next()), as a result
1765                         * the space of queue is saved.
1766                         */
1767                        if (!first)
1768                                continue;
1769
1770                        first = false;
1771
1772                        if (__cq_enqueue(cq, entry))
1773                                return BFS_EQUEUEFULL;
1774
1775                        cq_depth = __cq_get_elem_count(cq);
1776                        if (max_bfs_queue_depth < cq_depth)
1777                                max_bfs_queue_depth = cq_depth;
1778                }
1779        }
1780
1781        return BFS_RNOMATCH;
1782}
1783
1784static inline enum bfs_result
1785__bfs_forwards(struct lock_list *src_entry,
1786               void *data,
1787               bool (*match)(struct lock_list *entry, void *data),
1788               bool (*skip)(struct lock_list *entry, void *data),
1789               struct lock_list **target_entry)
1790{
1791        return __bfs(src_entry, data, match, skip, target_entry,
1792                     offsetof(struct lock_class, locks_after));
1793
1794}
1795
1796static inline enum bfs_result
1797__bfs_backwards(struct lock_list *src_entry,
1798                void *data,
1799                bool (*match)(struct lock_list *entry, void *data),
1800               bool (*skip)(struct lock_list *entry, void *data),
1801                struct lock_list **target_entry)
1802{
1803        return __bfs(src_entry, data, match, skip, target_entry,
1804                     offsetof(struct lock_class, locks_before));
1805
1806}
1807
1808static void print_lock_trace(const struct lock_trace *trace,
1809                             unsigned int spaces)
1810{
1811        stack_trace_print(trace->entries, trace->nr_entries, spaces);
1812}
1813
1814/*
1815 * Print a dependency chain entry (this is only done when a deadlock
1816 * has been detected):
1817 */
1818static noinline void
1819print_circular_bug_entry(struct lock_list *target, int depth)
1820{
1821        if (debug_locks_silent)
1822                return;
1823        printk("\n-> #%u", depth);
1824        print_lock_name(target->class);
1825        printk(KERN_CONT ":\n");
1826        print_lock_trace(target->trace, 6);
1827}
1828
1829static void
1830print_circular_lock_scenario(struct held_lock *src,
1831                             struct held_lock *tgt,
1832                             struct lock_list *prt)
1833{
1834        struct lock_class *source = hlock_class(src);
1835        struct lock_class *target = hlock_class(tgt);
1836        struct lock_class *parent = prt->class;
1837
1838        /*
1839         * A direct locking problem where unsafe_class lock is taken
1840         * directly by safe_class lock, then all we need to show
1841         * is the deadlock scenario, as it is obvious that the
1842         * unsafe lock is taken under the safe lock.
1843         *
1844         * But if there is a chain instead, where the safe lock takes
1845         * an intermediate lock (middle_class) where this lock is
1846         * not the same as the safe lock, then the lock chain is
1847         * used to describe the problem. Otherwise we would need
1848         * to show a different CPU case for each link in the chain
1849         * from the safe_class lock to the unsafe_class lock.
1850         */
1851        if (parent != source) {
1852                printk("Chain exists of:\n  ");
1853                __print_lock_name(source);
1854                printk(KERN_CONT " --> ");
1855                __print_lock_name(parent);
1856                printk(KERN_CONT " --> ");
1857                __print_lock_name(target);
1858                printk(KERN_CONT "\n\n");
1859        }
1860
1861        printk(" Possible unsafe locking scenario:\n\n");
1862        printk("       CPU0                    CPU1\n");
1863        printk("       ----                    ----\n");
1864        printk("  lock(");
1865        __print_lock_name(target);
1866        printk(KERN_CONT ");\n");
1867        printk("                               lock(");
1868        __print_lock_name(parent);
1869        printk(KERN_CONT ");\n");
1870        printk("                               lock(");
1871        __print_lock_name(target);
1872        printk(KERN_CONT ");\n");
1873        printk("  lock(");
1874        __print_lock_name(source);
1875        printk(KERN_CONT ");\n");
1876        printk("\n *** DEADLOCK ***\n\n");
1877}
1878
1879/*
1880 * When a circular dependency is detected, print the
1881 * header first:
1882 */
1883static noinline void
1884print_circular_bug_header(struct lock_list *entry, unsigned int depth,
1885                        struct held_lock *check_src,
1886                        struct held_lock *check_tgt)
1887{
1888        struct task_struct *curr = current;
1889
1890        if (debug_locks_silent)
1891                return;
1892
1893        pr_warn("\n");
1894        pr_warn("======================================================\n");
1895        pr_warn("WARNING: possible circular locking dependency detected\n");
1896        print_kernel_ident();
1897        pr_warn("------------------------------------------------------\n");
1898        pr_warn("%s/%d is trying to acquire lock:\n",
1899                curr->comm, task_pid_nr(curr));
1900        print_lock(check_src);
1901
1902        pr_warn("\nbut task is already holding lock:\n");
1903
1904        print_lock(check_tgt);
1905        pr_warn("\nwhich lock already depends on the new lock.\n\n");
1906        pr_warn("\nthe existing dependency chain (in reverse order) is:\n");
1907
1908        print_circular_bug_entry(entry, depth);
1909}
1910
1911/*
1912 * We are about to add A -> B into the dependency graph, and in __bfs() a
1913 * strong dependency path A -> .. -> B is found: hlock_class equals
1914 * entry->class.
1915 *
1916 * If A -> .. -> B can replace A -> B in any __bfs() search (means the former
1917 * is _stronger_ than or equal to the latter), we consider A -> B as redundant.
1918 * For example if A -> .. -> B is -(EN)-> (i.e. A -(E*)-> .. -(*N)-> B), and A
1919 * -> B is -(ER)-> or -(EN)->, then we don't need to add A -> B into the
1920 * dependency graph, as any strong path ..-> A -> B ->.. we can get with
1921 * having dependency A -> B, we could already get a equivalent path ..-> A ->
1922 * .. -> B -> .. with A -> .. -> B. Therefore A -> B is redundant.
1923 *
1924 * We need to make sure both the start and the end of A -> .. -> B is not
1925 * weaker than A -> B. For the start part, please see the comment in
1926 * check_redundant(). For the end part, we need:
1927 *
1928 * Either
1929 *
1930 *     a) A -> B is -(*R)-> (everything is not weaker than that)
1931 *
1932 * or
1933 *
1934 *     b) A -> .. -> B is -(*N)-> (nothing is stronger than this)
1935 *
1936 */
1937static inline bool hlock_equal(struct lock_list *entry, void *data)
1938{
1939        struct held_lock *hlock = (struct held_lock *)data;
1940
1941        return hlock_class(hlock) == entry->class && /* Found A -> .. -> B */
1942               (hlock->read == 2 ||  /* A -> B is -(*R)-> */
1943                !entry->only_xr); /* A -> .. -> B is -(*N)-> */
1944}
1945
1946/*
1947 * We are about to add B -> A into the dependency graph, and in __bfs() a
1948 * strong dependency path A -> .. -> B is found: hlock_class equals
1949 * entry->class.
1950 *
1951 * We will have a deadlock case (conflict) if A -> .. -> B -> A is a strong
1952 * dependency cycle, that means:
1953 *
1954 * Either
1955 *
1956 *     a) B -> A is -(E*)->
1957 *
1958 * or
1959 *
1960 *     b) A -> .. -> B is -(*N)-> (i.e. A -> .. -(*N)-> B)
1961 *
1962 * as then we don't have -(*R)-> -(S*)-> in the cycle.
1963 */
1964static inline bool hlock_conflict(struct lock_list *entry, void *data)
1965{
1966        struct held_lock *hlock = (struct held_lock *)data;
1967
1968        return hlock_class(hlock) == entry->class && /* Found A -> .. -> B */
1969               (hlock->read == 0 || /* B -> A is -(E*)-> */
1970                !entry->only_xr); /* A -> .. -> B is -(*N)-> */
1971}
1972
1973static noinline void print_circular_bug(struct lock_list *this,
1974                                struct lock_list *target,
1975                                struct held_lock *check_src,
1976                                struct held_lock *check_tgt)
1977{
1978        struct task_struct *curr = current;
1979        struct lock_list *parent;
1980        struct lock_list *first_parent;
1981        int depth;
1982
1983        if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1984                return;
1985
1986        this->trace = save_trace();
1987        if (!this->trace)
1988                return;
1989
1990        depth = get_lock_depth(target);
1991
1992        print_circular_bug_header(target, depth, check_src, check_tgt);
1993
1994        parent = get_lock_parent(target);
1995        first_parent = parent;
1996
1997        while (parent) {
1998                print_circular_bug_entry(parent, --depth);
1999                parent = get_lock_parent(parent);
2000        }
2001
2002        printk("\nother info that might help us debug this:\n\n");
2003        print_circular_lock_scenario(check_src, check_tgt,
2004                                     first_parent);
2005
2006        lockdep_print_held_locks(curr);
2007
2008        printk("\nstack backtrace:\n");
2009        dump_stack();
2010}
2011
2012static noinline void print_bfs_bug(int ret)
2013{
2014        if (!debug_locks_off_graph_unlock())
2015                return;
2016
2017        /*
2018         * Breadth-first-search failed, graph got corrupted?
2019         */
2020        WARN(1, "lockdep bfs error:%d\n", ret);
2021}
2022
2023static bool noop_count(struct lock_list *entry, void *data)
2024{
2025        (*(unsigned long *)data)++;
2026        return false;
2027}
2028
2029static unsigned long __lockdep_count_forward_deps(struct lock_list *this)
2030{
2031        unsigned long  count = 0;
2032        struct lock_list *target_entry;
2033
2034        __bfs_forwards(this, (void *)&count, noop_count, NULL, &target_entry);
2035
2036        return count;
2037}
2038unsigned long lockdep_count_forward_deps(struct lock_class *class)
2039{
2040        unsigned long ret, flags;
2041        struct lock_list this;
2042
2043        __bfs_init_root(&this, class);
2044
2045        raw_local_irq_save(flags);
2046        lockdep_lock();
2047        ret = __lockdep_count_forward_deps(&this);
2048        lockdep_unlock();
2049        raw_local_irq_restore(flags);
2050
2051        return ret;
2052}
2053
2054static unsigned long __lockdep_count_backward_deps(struct lock_list *this)
2055{
2056        unsigned long  count = 0;
2057        struct lock_list *target_entry;
2058
2059        __bfs_backwards(this, (void *)&count, noop_count, NULL, &target_entry);
2060
2061        return count;
2062}
2063
2064unsigned long lockdep_count_backward_deps(struct lock_class *class)
2065{
2066        unsigned long ret, flags;
2067        struct lock_list this;
2068
2069        __bfs_init_root(&this, class);
2070
2071        raw_local_irq_save(flags);
2072        lockdep_lock();
2073        ret = __lockdep_count_backward_deps(&this);
2074        lockdep_unlock();
2075        raw_local_irq_restore(flags);
2076
2077        return ret;
2078}
2079
2080/*
2081 * Check that the dependency graph starting at <src> can lead to
2082 * <target> or not.
2083 */
2084static noinline enum bfs_result
2085check_path(struct held_lock *target, struct lock_list *src_entry,
2086           bool (*match)(struct lock_list *entry, void *data),
2087           bool (*skip)(struct lock_list *entry, void *data),
2088           struct lock_list **target_entry)
2089{
2090        enum bfs_result ret;
2091
2092        ret = __bfs_forwards(src_entry, target, match, skip, target_entry);
2093
2094        if (unlikely(bfs_error(ret)))
2095                print_bfs_bug(ret);
2096
2097        return ret;
2098}
2099
2100/*
2101 * Prove that the dependency graph starting at <src> can not
2102 * lead to <target>. If it can, there is a circle when adding
2103 * <target> -> <src> dependency.
2104 *
2105 * Print an error and return BFS_RMATCH if it does.
2106 */
2107static noinline enum bfs_result
2108check_noncircular(struct held_lock *src, struct held_lock *target,
2109                  struct lock_trace **const trace)
2110{
2111        enum bfs_result ret;
2112        struct lock_list *target_entry;
2113        struct lock_list src_entry;
2114
2115        bfs_init_root(&src_entry, src);
2116
2117        debug_atomic_inc(nr_cyclic_checks);
2118
2119        ret = check_path(target, &src_entry, hlock_conflict, NULL, &target_entry);
2120
2121        if (unlikely(ret == BFS_RMATCH)) {
2122                if (!*trace) {
2123                        /*
2124                         * If save_trace fails here, the printing might
2125                         * trigger a WARN but because of the !nr_entries it
2126                         * should not do bad things.
2127                         */
2128                        *trace = save_trace();
2129                }
2130
2131                print_circular_bug(&src_entry, target_entry, src, target);
2132        }
2133
2134        return ret;
2135}
2136
2137#ifdef CONFIG_TRACE_IRQFLAGS
2138
2139/*
2140 * Forwards and backwards subgraph searching, for the purposes of
2141 * proving that two subgraphs can be connected by a new dependency
2142 * without creating any illegal irq-safe -> irq-unsafe lock dependency.
2143 *
2144 * A irq safe->unsafe deadlock happens with the following conditions:
2145 *
2146 * 1) We have a strong dependency path A -> ... -> B
2147 *
2148 * 2) and we have ENABLED_IRQ usage of B and USED_IN_IRQ usage of A, therefore
2149 *    irq can create a new dependency B -> A (consider the case that a holder
2150 *    of B gets interrupted by an irq whose handler will try to acquire A).
2151 *
2152 * 3) the dependency circle A -> ... -> B -> A we get from 1) and 2) is a
2153 *    strong circle:
2154 *
2155 *      For the usage bits of B:
2156 *        a) if A -> B is -(*N)->, then B -> A could be any type, so any
2157 *           ENABLED_IRQ usage suffices.
2158 *        b) if A -> B is -(*R)->, then B -> A must be -(E*)->, so only
2159 *           ENABLED_IRQ_*_READ usage suffices.
2160 *
2161 *      For the usage bits of A:
2162 *        c) if A -> B is -(E*)->, then B -> A could be any type, so any
2163 *           USED_IN_IRQ usage suffices.
2164 *        d) if A -> B is -(S*)->, then B -> A must be -(*N)->, so only
2165 *           USED_IN_IRQ_*_READ usage suffices.
2166 */
2167
2168/*
2169 * There is a strong dependency path in the dependency graph: A -> B, and now
2170 * we need to decide which usage bit of A should be accumulated to detect
2171 * safe->unsafe bugs.
2172 *
2173 * Note that usage_accumulate() is used in backwards search, so ->only_xr
2174 * stands for whether A -> B only has -(S*)-> (in this case ->only_xr is true).
2175 *
2176 * As above, if only_xr is false, which means A -> B has -(E*)-> dependency
2177 * path, any usage of A should be considered. Otherwise, we should only
2178 * consider _READ usage.
2179 */
2180static inline bool usage_accumulate(struct lock_list *entry, void *mask)
2181{
2182        if (!entry->only_xr)
2183                *(unsigned long *)mask |= entry->class->usage_mask;
2184        else /* Mask out _READ usage bits */
2185                *(unsigned long *)mask |= (entry->class->usage_mask & LOCKF_IRQ);
2186
2187        return false;
2188}
2189
2190/*
2191 * There is a strong dependency path in the dependency graph: A -> B, and now
2192 * we need to decide which usage bit of B conflicts with the usage bits of A,
2193 * i.e. which usage bit of B may introduce safe->unsafe deadlocks.
2194 *
2195 * As above, if only_xr is false, which means A -> B has -(*N)-> dependency
2196 * path, any usage of B should be considered. Otherwise, we should only
2197 * consider _READ usage.
2198 */
2199static inline bool usage_match(struct lock_list *entry, void *mask)
2200{
2201        if (!entry->only_xr)
2202                return !!(entry->class->usage_mask & *(unsigned long *)mask);
2203        else /* Mask out _READ usage bits */
2204                return !!((entry->class->usage_mask & LOCKF_IRQ) & *(unsigned long *)mask);
2205}
2206
2207static inline bool usage_skip(struct lock_list *entry, void *mask)
2208{
2209        /*
2210         * Skip local_lock() for irq inversion detection.
2211         *
2212         * For !RT, local_lock() is not a real lock, so it won't carry any
2213         * dependency.
2214         *
2215         * For RT, an irq inversion happens when we have lock A and B, and on
2216         * some CPU we can have:
2217         *
2218         *      lock(A);
2219         *      <interrupted>
2220         *        lock(B);
2221         *
2222         * where lock(B) cannot sleep, and we have a dependency B -> ... -> A.
2223         *
2224         * Now we prove local_lock() cannot exist in that dependency. First we
2225         * have the observation for any lock chain L1 -> ... -> Ln, for any
2226         * 1 <= i <= n, Li.inner_wait_type <= L1.inner_wait_type, otherwise
2227         * wait context check will complain. And since B is not a sleep lock,
2228         * therefore B.inner_wait_type >= 2, and since the inner_wait_type of
2229         * local_lock() is 3, which is greater than 2, therefore there is no
2230         * way the local_lock() exists in the dependency B -> ... -> A.
2231         *
2232         * As a result, we will skip local_lock(), when we search for irq
2233         * inversion bugs.
2234         */
2235        if (entry->class->lock_type == LD_LOCK_PERCPU) {
2236                if (DEBUG_LOCKS_WARN_ON(entry->class->wait_type_inner < LD_WAIT_CONFIG))
2237                        return false;
2238
2239                return true;
2240        }
2241
2242        return false;
2243}
2244
2245/*
2246 * Find a node in the forwards-direction dependency sub-graph starting
2247 * at @root->class that matches @bit.
2248 *
2249 * Return BFS_MATCH if such a node exists in the subgraph, and put that node
2250 * into *@target_entry.
2251 */
2252static enum bfs_result
2253find_usage_forwards(struct lock_list *root, unsigned long usage_mask,
2254                        struct lock_list **target_entry)
2255{
2256        enum bfs_result result;
2257
2258        debug_atomic_inc(nr_find_usage_forwards_checks);
2259
2260        result = __bfs_forwards(root, &usage_mask, usage_match, usage_skip, target_entry);
2261
2262        return result;
2263}
2264
2265/*
2266 * Find a node in the backwards-direction dependency sub-graph starting
2267 * at @root->class that matches @bit.
2268 */
2269static enum bfs_result
2270find_usage_backwards(struct lock_list *root, unsigned long usage_mask,
2271                        struct lock_list **target_entry)
2272{
2273        enum bfs_result result;
2274
2275        debug_atomic_inc(nr_find_usage_backwards_checks);
2276
2277        result = __bfs_backwards(root, &usage_mask, usage_match, usage_skip, target_entry);
2278
2279        return result;
2280}
2281
2282static void print_lock_class_header(struct lock_class *class, int depth)
2283{
2284        int bit;
2285
2286        printk("%*s->", depth, "");
2287        print_lock_name(class);
2288#ifdef CONFIG_DEBUG_LOCKDEP
2289        printk(KERN_CONT " ops: %lu", debug_class_ops_read(class));
2290#endif
2291        printk(KERN_CONT " {\n");
2292
2293        for (bit = 0; bit < LOCK_TRACE_STATES; bit++) {
2294                if (class->usage_mask & (1 << bit)) {
2295                        int len = depth;
2296
2297                        len += printk("%*s   %s", depth, "", usage_str[bit]);
2298                        len += printk(KERN_CONT " at:\n");
2299                        print_lock_trace(class->usage_traces[bit], len);
2300                }
2301        }
2302        printk("%*s }\n", depth, "");
2303
2304        printk("%*s ... key      at: [<%px>] %pS\n",
2305                depth, "", class->key, class->key);
2306}
2307
2308/*
2309 * Dependency path printing:
2310 *
2311 * After BFS we get a lock dependency path (linked via ->parent of lock_list),
2312 * printing out each lock in the dependency path will help on understanding how
2313 * the deadlock could happen. Here are some details about dependency path
2314 * printing:
2315 *
2316 * 1)   A lock_list can be either forwards or backwards for a lock dependency,
2317 *      for a lock dependency A -> B, there are two lock_lists:
2318 *
2319 *      a)      lock_list in the ->locks_after list of A, whose ->class is B and
2320 *              ->links_to is A. In this case, we can say the lock_list is
2321 *              "A -> B" (forwards case).
2322 *
2323 *      b)      lock_list in the ->locks_before list of B, whose ->class is A
2324 *              and ->links_to is B. In this case, we can say the lock_list is
2325 *              "B <- A" (bacwards case).
2326 *
2327 *      The ->trace of both a) and b) point to the call trace where B was
2328 *      acquired with A held.
2329 *
2330 * 2)   A "helper" lock_list is introduced during BFS, this lock_list doesn't
2331 *      represent a certain lock dependency, it only provides an initial entry
2332 *      for BFS. For example, BFS may introduce a "helper" lock_list whose
2333 *      ->class is A, as a result BFS will search all dependencies starting with
2334 *      A, e.g. A -> B or A -> C.
2335 *
2336 *      The notation of a forwards helper lock_list is like "-> A", which means
2337 *      we should search the forwards dependencies starting with "A", e.g A -> B
2338 *      or A -> C.
2339 *
2340 *      The notation of a bacwards helper lock_list is like "<- B", which means
2341 *      we should search the backwards dependencies ending with "B", e.g.
2342 *      B <- A or B <- C.
2343 */
2344
2345/*
2346 * printk the shortest lock dependencies from @root to @leaf in reverse order.
2347 *
2348 * We have a lock dependency path as follow:
2349 *
2350 *    @root                                                                 @leaf
2351 *      |                                                                     |
2352 *      V                                                                     V
2353 *                ->parent                                   ->parent
2354 * | lock_list | <--------- | lock_list | ... | lock_list  | <--------- | lock_list |
2355 * |    -> L1  |            | L1 -> L2  | ... |Ln-2 -> Ln-1|            | Ln-1 -> Ln|
2356 *
2357 * , so it's natural that we start from @leaf and print every ->class and
2358 * ->trace until we reach the @root.
2359 */
2360static void __used
2361print_shortest_lock_dependencies(struct lock_list *leaf,
2362                                 struct lock_list *root)
2363{
2364        struct lock_list *entry = leaf;
2365        int depth;
2366
2367        /*compute depth from generated tree by BFS*/
2368        depth = get_lock_depth(leaf);
2369
2370        do {
2371                print_lock_class_header(entry->class, depth);
2372                printk("%*s ... acquired at:\n", depth, "");
2373                print_lock_trace(entry->trace, 2);
2374                printk("\n");
2375
2376                if (depth == 0 && (entry != root)) {
2377                        printk("lockdep:%s bad path found in chain graph\n", __func__);
2378                        break;
2379                }
2380
2381                entry = get_lock_parent(entry);
2382                depth--;
2383        } while (entry && (depth >= 0));
2384}
2385
2386/*
2387 * printk the shortest lock dependencies from @leaf to @root.
2388 *
2389 * We have a lock dependency path (from a backwards search) as follow:
2390 *
2391 *    @leaf                                                                 @root
2392 *      |                                                                     |
2393 *      V                                                                     V
2394 *                ->parent                                   ->parent
2395 * | lock_list | ---------> | lock_list | ... | lock_list  | ---------> | lock_list |
2396 * | L2 <- L1  |            | L3 <- L2  | ... | Ln <- Ln-1 |            |    <- Ln  |
2397 *
2398 * , so when we iterate from @leaf to @root, we actually print the lock
2399 * dependency path L1 -> L2 -> .. -> Ln in the non-reverse order.
2400 *
2401 * Another thing to notice here is that ->class of L2 <- L1 is L1, while the
2402 * ->trace of L2 <- L1 is the call trace of L2, in fact we don't have the call
2403 * trace of L1 in the dependency path, which is alright, because most of the
2404 * time we can figure out where L1 is held from the call trace of L2.
2405 */
2406static void __used
2407print_shortest_lock_dependencies_backwards(struct lock_list *leaf,
2408                                           struct lock_list *root)
2409{
2410        struct lock_list *entry = leaf;
2411        const struct lock_trace *trace = NULL;
2412        int depth;
2413
2414        /*compute depth from generated tree by BFS*/
2415        depth = get_lock_depth(leaf);
2416
2417        do {
2418                print_lock_class_header(entry->class, depth);
2419                if (trace) {
2420                        printk("%*s ... acquired at:\n", depth, "");
2421                        print_lock_trace(trace, 2);
2422                        printk("\n");
2423                }
2424
2425                /*
2426                 * Record the pointer to the trace for the next lock_list
2427                 * entry, see the comments for the function.
2428                 */
2429                trace = entry->trace;
2430
2431                if (depth == 0 && (entry != root)) {
2432                        printk("lockdep:%s bad path found in chain graph\n", __func__);
2433                        break;
2434                }
2435
2436                entry = get_lock_parent(entry);
2437                depth--;
2438        } while (entry && (depth >= 0));
2439}
2440
2441static void
2442print_irq_lock_scenario(struct lock_list *safe_entry,
2443                        struct lock_list *unsafe_entry,
2444                        struct lock_class *prev_class,
2445                        struct lock_class *next_class)
2446{
2447        struct lock_class *safe_class = safe_entry->class;
2448        struct lock_class *unsafe_class = unsafe_entry->class;
2449        struct lock_class *middle_class = prev_class;
2450
2451        if (middle_class == safe_class)
2452                middle_class = next_class;
2453
2454        /*
2455         * A direct locking problem where unsafe_class lock is taken
2456         * directly by safe_class lock, then all we need to show
2457         * is the deadlock scenario, as it is obvious that the
2458         * unsafe lock is taken under the safe lock.
2459         *
2460         * But if there is a chain instead, where the safe lock takes
2461         * an intermediate lock (middle_class) where this lock is
2462         * not the same as the safe lock, then the lock chain is
2463         * used to describe the problem. Otherwise we would need
2464         * to show a different CPU case for each link in the chain
2465         * from the safe_class lock to the unsafe_class lock.
2466         */
2467        if (middle_class != unsafe_class) {
2468                printk("Chain exists of:\n  ");
2469                __print_lock_name(safe_class);
2470                printk(KERN_CONT " --> ");
2471                __print_lock_name(middle_class);
2472                printk(KERN_CONT " --> ");
2473                __print_lock_name(unsafe_class);
2474                printk(KERN_CONT "\n\n");
2475        }
2476
2477        printk(" Possible interrupt unsafe locking scenario:\n\n");
2478        printk("       CPU0                    CPU1\n");
2479        printk("       ----                    ----\n");
2480        printk("  lock(");
2481        __print_lock_name(unsafe_class);
2482        printk(KERN_CONT ");\n");
2483        printk("                               local_irq_disable();\n");
2484        printk("                               lock(");
2485        __print_lock_name(safe_class);
2486        printk(KERN_CONT ");\n");
2487        printk("                               lock(");
2488        __print_lock_name(middle_class);
2489        printk(KERN_CONT ");\n");
2490        printk("  <Interrupt>\n");
2491        printk("    lock(");
2492        __print_lock_name(safe_class);
2493        printk(KERN_CONT ");\n");
2494        printk("\n *** DEADLOCK ***\n\n");
2495}
2496
2497static void
2498print_bad_irq_dependency(struct task_struct *curr,
2499                         struct lock_list *prev_root,
2500                         struct lock_list *next_root,
2501                         struct lock_list *backwards_entry,
2502                         struct lock_list *forwards_entry,
2503                         struct held_lock *prev,
2504                         struct held_lock *next,
2505                         enum lock_usage_bit bit1,
2506                         enum lock_usage_bit bit2,
2507                         const char *irqclass)
2508{
2509        if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2510                return;
2511
2512        pr_warn("\n");
2513        pr_warn("=====================================================\n");
2514        pr_warn("WARNING: %s-safe -> %s-unsafe lock order detected\n",
2515                irqclass, irqclass);
2516        print_kernel_ident();
2517        pr_warn("-----------------------------------------------------\n");
2518        pr_warn("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
2519                curr->comm, task_pid_nr(curr),
2520                lockdep_hardirq_context(), hardirq_count() >> HARDIRQ_SHIFT,
2521                curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT,
2522                lockdep_hardirqs_enabled(),
2523                curr->softirqs_enabled);
2524        print_lock(next);
2525
2526        pr_warn("\nand this task is already holding:\n");
2527        print_lock(prev);
2528        pr_warn("which would create a new lock dependency:\n");
2529        print_lock_name(hlock_class(prev));
2530        pr_cont(" ->");
2531        print_lock_name(hlock_class(next));
2532        pr_cont("\n");
2533
2534        pr_warn("\nbut this new dependency connects a %s-irq-safe lock:\n",
2535                irqclass);
2536        print_lock_name(backwards_entry->class);
2537        pr_warn("\n... which became %s-irq-safe at:\n", irqclass);
2538
2539        print_lock_trace(backwards_entry->class->usage_traces[bit1], 1);
2540
2541        pr_warn("\nto a %s-irq-unsafe lock:\n", irqclass);
2542        print_lock_name(forwards_entry->class);
2543        pr_warn("\n... which became %s-irq-unsafe at:\n", irqclass);
2544        pr_warn("...");
2545
2546        print_lock_trace(forwards_entry->class->usage_traces[bit2], 1);
2547
2548        pr_warn("\nother info that might help us debug this:\n\n");
2549        print_irq_lock_scenario(backwards_entry, forwards_entry,
2550                                hlock_class(prev), hlock_class(next));
2551
2552        lockdep_print_held_locks(curr);
2553
2554        pr_warn("\nthe dependencies between %s-irq-safe lock and the holding lock:\n", irqclass);
2555        print_shortest_lock_dependencies_backwards(backwards_entry, prev_root);
2556
2557        pr_warn("\nthe dependencies between the lock to be acquired");
2558        pr_warn(" and %s-irq-unsafe lock:\n", irqclass);
2559        next_root->trace = save_trace();
2560        if (!next_root->trace)
2561                return;
2562        print_shortest_lock_dependencies(forwards_entry, next_root);
2563
2564        pr_warn("\nstack backtrace:\n");
2565        dump_stack();
2566}
2567
2568static const char *state_names[] = {
2569#define LOCKDEP_STATE(__STATE) \
2570        __stringify(__STATE),
2571#include "lockdep_states.h"
2572#undef LOCKDEP_STATE
2573};
2574
2575static const char *state_rnames[] = {
2576#define LOCKDEP_STATE(__STATE) \
2577        __stringify(__STATE)"-READ",
2578#include "lockdep_states.h"
2579#undef LOCKDEP_STATE
2580};
2581
2582static inline const char *state_name(enum lock_usage_bit bit)
2583{
2584        if (bit & LOCK_USAGE_READ_MASK)
2585                return state_rnames[bit >> LOCK_USAGE_DIR_MASK];
2586        else
2587                return state_names[bit >> LOCK_USAGE_DIR_MASK];
2588}
2589
2590/*
2591 * The bit number is encoded like:
2592 *
2593 *  bit0: 0 exclusive, 1 read lock
2594 *  bit1: 0 used in irq, 1 irq enabled
2595 *  bit2-n: state
2596 */
2597static int exclusive_bit(int new_bit)
2598{
2599        int state = new_bit & LOCK_USAGE_STATE_MASK;
2600        int dir = new_bit & LOCK_USAGE_DIR_MASK;
2601
2602        /*
2603         * keep state, bit flip the direction and strip read.
2604         */
2605        return state | (dir ^ LOCK_USAGE_DIR_MASK);
2606}
2607
2608/*
2609 * Observe that when given a bitmask where each bitnr is encoded as above, a
2610 * right shift of the mask transforms the individual bitnrs as -1 and
2611 * conversely, a left shift transforms into +1 for the individual bitnrs.
2612 *
2613 * So for all bits whose number have LOCK_ENABLED_* set (bitnr1 == 1), we can
2614 * create the mask with those bit numbers using LOCK_USED_IN_* (bitnr1 == 0)
2615 * instead by subtracting the bit number by 2, or shifting the mask right by 2.
2616 *
2617 * Similarly, bitnr1 == 0 becomes bitnr1 == 1 by adding 2, or shifting left 2.
2618 *
2619 * So split the mask (note that LOCKF_ENABLED_IRQ_ALL|LOCKF_USED_IN_IRQ_ALL is
2620 * all bits set) and recompose with bitnr1 flipped.
2621 */
2622static unsigned long invert_dir_mask(unsigned long mask)
2623{
2624        unsigned long excl = 0;
2625
2626        /* Invert dir */
2627        excl |= (mask & LOCKF_ENABLED_IRQ_ALL) >> LOCK_USAGE_DIR_MASK;
2628        excl |= (mask & LOCKF_USED_IN_IRQ_ALL) << LOCK_USAGE_DIR_MASK;
2629
2630        return excl;
2631}
2632
2633/*
2634 * Note that a LOCK_ENABLED_IRQ_*_READ usage and a LOCK_USED_IN_IRQ_*_READ
2635 * usage may cause deadlock too, for example:
2636 *
2637 * P1                           P2
2638 * <irq disabled>
2639 * write_lock(l1);              <irq enabled>
2640 *                              read_lock(l2);
2641 * write_lock(l2);
2642 *                              <in irq>
2643 *                              read_lock(l1);
2644 *
2645 * , in above case, l1 will be marked as LOCK_USED_IN_IRQ_HARDIRQ_READ and l2
2646 * will marked as LOCK_ENABLE_IRQ_HARDIRQ_READ, and this is a possible
2647 * deadlock.
2648 *
2649 * In fact, all of the following cases may cause deadlocks:
2650 *
2651 *       LOCK_USED_IN_IRQ_* -> LOCK_ENABLED_IRQ_*
2652 *       LOCK_USED_IN_IRQ_*_READ -> LOCK_ENABLED_IRQ_*
2653 *       LOCK_USED_IN_IRQ_* -> LOCK_ENABLED_IRQ_*_READ
2654 *       LOCK_USED_IN_IRQ_*_READ -> LOCK_ENABLED_IRQ_*_READ
2655 *
2656 * As a result, to calculate the "exclusive mask", first we invert the
2657 * direction (USED_IN/ENABLED) of the original mask, and 1) for all bits with
2658 * bitnr0 set (LOCK_*_READ), add those with bitnr0 cleared (LOCK_*). 2) for all
2659 * bits with bitnr0 cleared (LOCK_*_READ), add those with bitnr0 set (LOCK_*).
2660 */
2661static unsigned long exclusive_mask(unsigned long mask)
2662{
2663        unsigned long excl = invert_dir_mask(mask);
2664
2665        excl |= (excl & LOCKF_IRQ_READ) >> LOCK_USAGE_READ_MASK;
2666        excl |= (excl & LOCKF_IRQ) << LOCK_USAGE_READ_MASK;
2667
2668        return excl;
2669}
2670
2671/*
2672 * Retrieve the _possible_ original mask to which @mask is
2673 * exclusive. Ie: this is the opposite of exclusive_mask().
2674 * Note that 2 possible original bits can match an exclusive
2675 * bit: one has LOCK_USAGE_READ_MASK set, the other has it
2676 * cleared. So both are returned for each exclusive bit.
2677 */
2678static unsigned long original_mask(unsigned long mask)
2679{
2680        unsigned long excl = invert_dir_mask(mask);
2681
2682        /* Include read in existing usages */
2683        excl |= (excl & LOCKF_IRQ_READ) >> LOCK_USAGE_READ_MASK;
2684        excl |= (excl & LOCKF_IRQ) << LOCK_USAGE_READ_MASK;
2685
2686        return excl;
2687}
2688
2689/*
2690 * Find the first pair of bit match between an original
2691 * usage mask and an exclusive usage mask.
2692 */
2693static int find_exclusive_match(unsigned long mask,
2694                                unsigned long excl_mask,
2695                                enum lock_usage_bit *bitp,
2696                                enum lock_usage_bit *excl_bitp)
2697{
2698        int bit, excl, excl_read;
2699
2700        for_each_set_bit(bit, &mask, LOCK_USED) {
2701                /*
2702                 * exclusive_bit() strips the read bit, however,
2703                 * LOCK_ENABLED_IRQ_*_READ may cause deadlocks too, so we need
2704                 * to search excl | LOCK_USAGE_READ_MASK as well.
2705                 */
2706                excl = exclusive_bit(bit);
2707                excl_read = excl | LOCK_USAGE_READ_MASK;
2708                if (excl_mask & lock_flag(excl)) {
2709                        *bitp = bit;
2710                        *excl_bitp = excl;
2711                        return 0;
2712                } else if (excl_mask & lock_flag(excl_read)) {
2713                        *bitp = bit;
2714                        *excl_bitp = excl_read;
2715                        return 0;
2716                }
2717        }
2718        return -1;
2719}
2720
2721/*
2722 * Prove that the new dependency does not connect a hardirq-safe(-read)
2723 * lock with a hardirq-unsafe lock - to achieve this we search
2724 * the backwards-subgraph starting at <prev>, and the
2725 * forwards-subgraph starting at <next>:
2726 */
2727static int check_irq_usage(struct task_struct *curr, struct held_lock *prev,
2728                           struct held_lock *next)
2729{
2730        unsigned long usage_mask = 0, forward_mask, backward_mask;
2731        enum lock_usage_bit forward_bit = 0, backward_bit = 0;
2732        struct lock_list *target_entry1;
2733        struct lock_list *target_entry;
2734        struct lock_list this, that;
2735        enum bfs_result ret;
2736
2737        /*
2738         * Step 1: gather all hard/soft IRQs usages backward in an
2739         * accumulated usage mask.
2740         */
2741        bfs_init_rootb(&this, prev);
2742
2743        ret = __bfs_backwards(&this, &usage_mask, usage_accumulate, usage_skip, NULL);
2744        if (bfs_error(ret)) {
2745                print_bfs_bug(ret);
2746                return 0;
2747        }
2748
2749        usage_mask &= LOCKF_USED_IN_IRQ_ALL;
2750        if (!usage_mask)
2751                return 1;
2752
2753        /*
2754         * Step 2: find exclusive uses forward that match the previous
2755         * backward accumulated mask.
2756         */
2757        forward_mask = exclusive_mask(usage_mask);
2758
2759        bfs_init_root(&that, next);
2760
2761        ret = find_usage_forwards(&that, forward_mask, &target_entry1);
2762        if (bfs_error(ret)) {
2763                print_bfs_bug(ret);
2764                return 0;
2765        }
2766        if (ret == BFS_RNOMATCH)
2767                return 1;
2768
2769        /*
2770         * Step 3: we found a bad match! Now retrieve a lock from the backward
2771         * list whose usage mask matches the exclusive usage mask from the
2772         * lock found on the forward list.
2773         *
2774         * Note, we should only keep the LOCKF_ENABLED_IRQ_ALL bits, considering
2775         * the follow case:
2776         *
2777         * When trying to add A -> B to the graph, we find that there is a
2778         * hardirq-safe L, that L -> ... -> A, and another hardirq-unsafe M,
2779         * that B -> ... -> M. However M is **softirq-safe**, if we use exact
2780         * invert bits of M's usage_mask, we will find another lock N that is
2781         * **softirq-unsafe** and N -> ... -> A, however N -> .. -> M will not
2782         * cause a inversion deadlock.
2783         */
2784        backward_mask = original_mask(target_entry1->class->usage_mask & LOCKF_ENABLED_IRQ_ALL);
2785
2786        ret = find_usage_backwards(&this, backward_mask, &target_entry);
2787        if (bfs_error(ret)) {
2788                print_bfs_bug(ret);
2789                return 0;
2790        }
2791        if (DEBUG_LOCKS_WARN_ON(ret == BFS_RNOMATCH))
2792                return 1;
2793
2794        /*
2795         * Step 4: narrow down to a pair of incompatible usage bits
2796         * and report it.
2797         */
2798        ret = find_exclusive_match(target_entry->class->usage_mask,
2799                                   target_entry1->class->usage_mask,
2800                                   &backward_bit, &forward_bit);
2801        if (DEBUG_LOCKS_WARN_ON(ret == -1))
2802                return 1;
2803
2804        print_bad_irq_dependency(curr, &this, &that,
2805                                 target_entry, target_entry1,
2806                                 prev, next,
2807                                 backward_bit, forward_bit,
2808                                 state_name(backward_bit));
2809
2810        return 0;
2811}
2812
2813#else
2814
2815static inline int check_irq_usage(struct task_struct *curr,
2816                                  struct held_lock *prev, struct held_lock *next)
2817{
2818        return 1;
2819}
2820
2821static inline bool usage_skip(struct lock_list *entry, void *mask)
2822{
2823        return false;
2824}
2825
2826#endif /* CONFIG_TRACE_IRQFLAGS */
2827
2828#ifdef CONFIG_LOCKDEP_SMALL
2829/*
2830 * Check that the dependency graph starting at <src> can lead to
2831 * <target> or not. If it can, <src> -> <target> dependency is already
2832 * in the graph.
2833 *
2834 * Return BFS_RMATCH if it does, or BFS_RNOMATCH if it does not, return BFS_E* if
2835 * any error appears in the bfs search.
2836 */
2837static noinline enum bfs_result
2838check_redundant(struct held_lock *src, struct held_lock *target)
2839{
2840        enum bfs_result ret;
2841        struct lock_list *target_entry;
2842        struct lock_list src_entry;
2843
2844        bfs_init_root(&src_entry, src);
2845        /*
2846         * Special setup for check_redundant().
2847         *
2848         * To report redundant, we need to find a strong dependency path that
2849         * is equal to or stronger than <src> -> <target>. So if <src> is E,
2850         * we need to let __bfs() only search for a path starting at a -(E*)->,
2851         * we achieve this by setting the initial node's ->only_xr to true in
2852         * that case. And if <prev> is S, we set initial ->only_xr to false
2853         * because both -(S*)-> (equal) and -(E*)-> (stronger) are redundant.
2854         */
2855        src_entry.only_xr = src->read == 0;
2856
2857        debug_atomic_inc(nr_redundant_checks);
2858
2859        /*
2860         * Note: we skip local_lock() for redundant check, because as the
2861         * comment in usage_skip(), A -> local_lock() -> B and A -> B are not
2862         * the same.
2863         */
2864        ret = check_path(target, &src_entry, hlock_equal, usage_skip, &target_entry);
2865
2866        if (ret == BFS_RMATCH)
2867                debug_atomic_inc(nr_redundant);
2868
2869        return ret;
2870}
2871
2872#else
2873
2874static inline enum bfs_result
2875check_redundant(struct held_lock *src, struct held_lock *target)
2876{
2877        return BFS_RNOMATCH;
2878}
2879
2880#endif
2881
2882static void inc_chains(int irq_context)
2883{
2884        if (irq_context & LOCK_CHAIN_HARDIRQ_CONTEXT)
2885                nr_hardirq_chains++;
2886        else if (irq_context & LOCK_CHAIN_SOFTIRQ_CONTEXT)
2887                nr_softirq_chains++;
2888        else
2889                nr_process_chains++;
2890}
2891
2892static void dec_chains(int irq_context)
2893{
2894        if (irq_context & LOCK_CHAIN_HARDIRQ_CONTEXT)
2895                nr_hardirq_chains--;
2896        else if (irq_context & LOCK_CHAIN_SOFTIRQ_CONTEXT)
2897                nr_softirq_chains--;
2898        else
2899                nr_process_chains--;
2900}
2901
2902static void
2903print_deadlock_scenario(struct held_lock *nxt, struct held_lock *prv)
2904{
2905        struct lock_class *next = hlock_class(nxt);
2906        struct lock_class *prev = hlock_class(prv);
2907
2908        printk(" Possible unsafe locking scenario:\n\n");
2909        printk("       CPU0\n");
2910        printk("       ----\n");
2911        printk("  lock(");
2912        __print_lock_name(prev);
2913        printk(KERN_CONT ");\n");
2914        printk("  lock(");
2915        __print_lock_name(next);
2916        printk(KERN_CONT ");\n");
2917        printk("\n *** DEADLOCK ***\n\n");
2918        printk(" May be due to missing lock nesting notation\n\n");
2919}
2920
2921static void
2922print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
2923                   struct held_lock *next)
2924{
2925        if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2926                return;
2927
2928        pr_warn("\n");
2929        pr_warn("============================================\n");
2930        pr_warn("WARNING: possible recursive locking detected\n");
2931        print_kernel_ident();
2932        pr_warn("--------------------------------------------\n");
2933        pr_warn("%s/%d is trying to acquire lock:\n",
2934                curr->comm, task_pid_nr(curr));
2935        print_lock(next);
2936        pr_warn("\nbut task is already holding lock:\n");
2937        print_lock(prev);
2938
2939        pr_warn("\nother info that might help us debug this:\n");
2940        print_deadlock_scenario(next, prev);
2941        lockdep_print_held_locks(curr);
2942
2943        pr_warn("\nstack backtrace:\n");
2944        dump_stack();
2945}
2946
2947/*
2948 * Check whether we are holding such a class already.
2949 *
2950 * (Note that this has to be done separately, because the graph cannot
2951 * detect such classes of deadlocks.)
2952 *
2953 * Returns: 0 on deadlock detected, 1 on OK, 2 if another lock with the same
2954 * lock class is held but nest_lock is also held, i.e. we rely on the
2955 * nest_lock to avoid the deadlock.
2956 */
2957static int
2958check_deadlock(struct task_struct *curr, struct held_lock *next)
2959{
2960        struct held_lock *prev;
2961        struct held_lock *nest = NULL;
2962        int i;
2963
2964        for (i = 0; i < curr->lockdep_depth; i++) {
2965                prev = curr->held_locks + i;
2966
2967                if (prev->instance == next->nest_lock)
2968                        nest = prev;
2969
2970                if (hlock_class(prev) != hlock_class(next))
2971                        continue;
2972
2973                /*
2974                 * Allow read-after-read recursion of the same
2975                 * lock class (i.e. read_lock(lock)+read_lock(lock)):
2976                 */
2977                if ((next->read == 2) && prev->read)
2978                        continue;
2979
2980                /*
2981                 * We're holding the nest_lock, which serializes this lock's
2982                 * nesting behaviour.
2983                 */
2984                if (nest)
2985                        return 2;
2986
2987                print_deadlock_bug(curr, prev, next);
2988                return 0;
2989        }
2990        return 1;
2991}
2992
2993/*
2994 * There was a chain-cache miss, and we are about to add a new dependency
2995 * to a previous lock. We validate the following rules:
2996 *
2997 *  - would the adding of the <prev> -> <next> dependency create a
2998 *    circular dependency in the graph? [== circular deadlock]
2999 *
3000 *  - does the new prev->next dependency connect any hardirq-safe lock
3001 *    (in the full backwards-subgraph starting at <prev>) with any
3002 *    hardirq-unsafe lock (in the full forwards-subgraph starting at
3003 *    <next>)? [== illegal lock inversion with hardirq contexts]
3004 *
3005 *  - does the new prev->next dependency connect any softirq-safe lock
3006 *    (in the full backwards-subgraph starting at <prev>) with any
3007 *    softirq-unsafe lock (in the full forwards-subgraph starting at
3008 *    <next>)? [== illegal lock inversion with softirq contexts]
3009 *
3010 * any of these scenarios could lead to a deadlock.
3011 *
3012 * Then if all the validations pass, we add the forwards and backwards
3013 * dependency.
3014 */
3015static int
3016check_prev_add(struct task_struct *curr, struct held_lock *prev,
3017               struct held_lock *next, u16 distance,
3018               struct lock_trace **const trace)
3019{
3020        struct lock_list *entry;
3021        enum bfs_result ret;
3022
3023        if (!hlock_class(prev)->key || !hlock_class(next)->key) {
3024                /*
3025                 * The warning statements below may trigger a use-after-free
3026                 * of the class name. It is better to trigger a use-after free
3027                 * and to have the class name most of the time instead of not
3028                 * having the class name available.
3029                 */
3030                WARN_ONCE(!debug_locks_silent && !hlock_class(prev)->key,
3031                          "Detected use-after-free of lock class %px/%s\n",
3032                          hlock_class(prev),
3033                          hlock_class(prev)->name);
3034                WARN_ONCE(!debug_locks_silent && !hlock_class(next)->key,
3035                          "Detected use-after-free of lock class %px/%s\n",
3036                          hlock_class(next),
3037                          hlock_class(next)->name);
3038                return 2;
3039        }
3040
3041        /*
3042         * Prove that the new <prev> -> <next> dependency would not
3043         * create a circular dependency in the graph. (We do this by
3044         * a breadth-first search into the graph starting at <next>,
3045         * and check whether we can reach <prev>.)
3046         *
3047         * The search is limited by the size of the circular queue (i.e.,
3048         * MAX_CIRCULAR_QUEUE_SIZE) which keeps track of a breadth of nodes
3049         * in the graph whose neighbours are to be checked.
3050         */
3051        ret = check_noncircular(next, prev, trace);
3052        if (unlikely(bfs_error(ret) || ret == BFS_RMATCH))
3053                return 0;
3054
3055        if (!check_irq_usage(curr, prev, next))
3056                return 0;
3057
3058        /*
3059         * Is the <prev> -> <next> dependency already present?
3060         *
3061         * (this may occur even though this is a new chain: consider
3062         *  e.g. the L1 -> L2 -> L3 -> L4 and the L5 -> L1 -> L2 -> L3
3063         *  chains - the second one will be new, but L1 already has
3064         *  L2 added to its dependency list, due to the first chain.)
3065         */
3066        list_for_each_entry(entry, &hlock_class(prev)->locks_after, entry) {
3067                if (entry->class == hlock_class(next)) {
3068                        if (distance == 1)
3069                                entry->distance = 1;
3070                        entry->dep |= calc_dep(prev, next);
3071
3072                        /*
3073                         * Also, update the reverse dependency in @next's
3074                         * ->locks_before list.
3075                         *
3076                         *  Here we reuse @entry as the cursor, which is fine
3077                         *  because we won't go to the next iteration of the
3078                         *  outer loop:
3079                         *
3080                         *  For normal cases, we return in the inner loop.
3081                         *
3082                         *  If we fail to return, we have inconsistency, i.e.
3083                         *  <prev>::locks_after contains <next> while
3084                         *  <next>::locks_before doesn't contain <prev>. In
3085                         *  that case, we return after the inner and indicate
3086                         *  something is wrong.
3087                         */
3088                        list_for_each_entry(entry, &hlock_class(next)->locks_before, entry) {
3089                                if (entry->class == hlock_class(prev)) {
3090                                        if (distance == 1)
3091                                                entry->distance = 1;
3092                                        entry->dep |= calc_depb(prev, next);
3093                                        return 1;
3094                                }
3095                        }
3096
3097                        /* <prev> is not found in <next>::locks_before */
3098                        return 0;
3099                }
3100        }
3101
3102        /*
3103         * Is the <prev> -> <next> link redundant?
3104         */
3105        ret = check_redundant(prev, next);
3106        if (bfs_error(ret))
3107                return 0;
3108        else if (ret == BFS_RMATCH)
3109                return 2;
3110
3111        if (!*trace) {
3112                *trace = save_trace();
3113                if (!*trace)
3114                        return 0;
3115        }
3116
3117        /*
3118         * Ok, all validations passed, add the new lock
3119         * to the previous lock's dependency list:
3120         */
3121        ret = add_lock_to_list(hlock_class(next), hlock_class(prev),
3122                               &hlock_class(prev)->locks_after,
3123                               next->acquire_ip, distance,
3124                               calc_dep(prev, next),
3125                               *trace);
3126
3127        if (!ret)
3128                return 0;
3129
3130        ret = add_lock_to_list(hlock_class(prev), hlock_class(next),
3131                               &hlock_class(next)->locks_before,
3132                               next->acquire_ip, distance,
3133                               calc_depb(prev, next),
3134                               *trace);
3135        if (!ret)
3136                return 0;
3137
3138        return 2;
3139}
3140
3141/*
3142 * Add the dependency to all directly-previous locks that are 'relevant'.
3143 * The ones that are relevant are (in increasing distance from curr):
3144 * all consecutive trylock entries and the final non-trylock entry - or
3145 * the end of this context's lock-chain - whichever comes first.
3146 */
3147static int
3148check_prevs_add(struct task_struct *curr, struct held_lock *next)
3149{
3150        struct lock_trace *trace = NULL;
3151        int depth = curr->lockdep_depth;
3152        struct held_lock *hlock;
3153
3154        /*
3155         * Debugging checks.
3156         *
3157         * Depth must not be zero for a non-head lock:
3158         */
3159        if (!depth)
3160                goto out_bug;
3161        /*
3162         * At least two relevant locks must exist for this
3163         * to be a head:
3164         */
3165        if (curr->held_locks[depth].irq_context !=
3166                        curr->held_locks[depth-1].irq_context)
3167                goto out_bug;
3168
3169        for (;;) {
3170                u16 distance = curr->lockdep_depth - depth + 1;
3171                hlock = curr->held_locks + depth - 1;
3172
3173                if (hlock->check) {
3174                        int ret = check_prev_add(curr, hlock, next, distance, &trace);
3175                        if (!ret)
3176                                return 0;
3177
3178                        /*
3179                         * Stop after the first non-trylock entry,
3180                         * as non-trylock entries have added their
3181                         * own direct dependencies already, so this
3182                         * lock is connected to them indirectly:
3183                         */
3184                        if (!hlock->trylock)
3185                                break;
3186                }
3187
3188                depth--;
3189                /*
3190                 * End of lock-stack?
3191                 */
3192                if (!depth)
3193                        break;
3194                /*
3195                 * Stop the search if we cross into another context:
3196                 */
3197                if (curr->held_locks[depth].irq_context !=
3198                                curr->held_locks[depth-1].irq_context)
3199                        break;
3200        }
3201        return 1;
3202out_bug:
3203        if (!debug_locks_off_graph_unlock())
3204                return 0;
3205
3206        /*
3207         * Clearly we all shouldn't be here, but since we made it we
3208         * can reliable say we messed up our state. See the above two
3209         * gotos for reasons why we could possibly end up here.
3210         */
3211        WARN_ON(1);
3212
3213        return 0;
3214}
3215
3216struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
3217static DECLARE_BITMAP(lock_chains_in_use, MAX_LOCKDEP_CHAINS);
3218static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
3219unsigned long nr_zapped_lock_chains;
3220unsigned int nr_free_chain_hlocks;      /* Free chain_hlocks in buckets */
3221unsigned int nr_lost_chain_hlocks;      /* Lost chain_hlocks */
3222unsigned int nr_large_chain_blocks;     /* size > MAX_CHAIN_BUCKETS */
3223
3224/*
3225 * The first 2 chain_hlocks entries in the chain block in the bucket
3226 * list contains the following meta data:
3227 *
3228 *   entry[0]:
3229 *     Bit    15 - always set to 1 (it is not a class index)
3230 *     Bits 0-14 - upper 15 bits of the next block index
3231 *   entry[1]    - lower 16 bits of next block index
3232 *
3233 * A next block index of all 1 bits means it is the end of the list.
3234 *
3235 * On the unsized bucket (bucket-0), the 3rd and 4th entries contain
3236 * the chain block size:
3237 *
3238 *   entry[2] - upper 16 bits of the chain block size
3239 *   entry[3] - lower 16 bits of the chain block size
3240 */
3241#define MAX_CHAIN_BUCKETS       16
3242#define CHAIN_BLK_FLAG          (1U << 15)
3243#define CHAIN_BLK_LIST_END      0xFFFFU
3244
3245static int chain_block_buckets[MAX_CHAIN_BUCKETS];
3246
3247static inline int size_to_bucket(int size)
3248{
3249        if (size > MAX_CHAIN_BUCKETS)
3250                return 0;
3251
3252        return size - 1;
3253}
3254
3255/*
3256 * Iterate all the chain blocks in a bucket.
3257 */
3258#define for_each_chain_block(bucket, prev, curr)                \
3259        for ((prev) = -1, (curr) = chain_block_buckets[bucket]; \
3260             (curr) >= 0;                                       \
3261             (prev) = (curr), (curr) = chain_block_next(curr))
3262
3263/*
3264 * next block or -1
3265 */
3266static inline int chain_block_next(int offset)
3267{
3268        int next = chain_hlocks[offset];
3269
3270        WARN_ON_ONCE(!(next & CHAIN_BLK_FLAG));
3271
3272        if (next == CHAIN_BLK_LIST_END)
3273                return -1;
3274
3275        next &= ~CHAIN_BLK_FLAG;
3276        next <<= 16;
3277        next |= chain_hlocks[offset + 1];
3278
3279        return next;
3280}
3281
3282/*
3283 * bucket-0 only
3284 */
3285static inline int chain_block_size(int offset)
3286{
3287        return (chain_hlocks[offset + 2] << 16) | chain_hlocks[offset + 3];
3288}
3289
3290static inline void init_chain_block(int offset, int next, int bucket, int size)
3291{
3292        chain_hlocks[offset] = (next >> 16) | CHAIN_BLK_FLAG;
3293        chain_hlocks[offset + 1] = (u16)next;
3294
3295        if (size && !bucket) {
3296                chain_hlocks[offset + 2] = size >> 16;
3297                chain_hlocks[offset + 3] = (u16)size;
3298        }
3299}
3300
3301static inline void add_chain_block(int offset, int size)
3302{
3303        int bucket = size_to_bucket(size);
3304        int next = chain_block_buckets[bucket];
3305        int prev, curr;
3306
3307        if (unlikely(size < 2)) {
3308                /*
3309                 * We can't store single entries on the freelist. Leak them.
3310                 *
3311                 * One possible way out would be to uniquely mark them, other
3312                 * than with CHAIN_BLK_FLAG, such that we can recover them when
3313                 * the block before it is re-added.
3314                 */
3315                if (size)
3316                        nr_lost_chain_hlocks++;
3317                return;
3318        }
3319
3320        nr_free_chain_hlocks += size;
3321        if (!bucket) {
3322                nr_large_chain_blocks++;
3323
3324                /*
3325                 * Variable sized, sort large to small.
3326                 */
3327                for_each_chain_block(0, prev, curr) {
3328                        if (size >= chain_block_size(curr))
3329                                break;
3330                }
3331                init_chain_block(offset, curr, 0, size);
3332                if (prev < 0)
3333                        chain_block_buckets[0] = offset;
3334                else
3335                        init_chain_block(prev, offset, 0, 0);
3336                return;
3337        }
3338        /*
3339         * Fixed size, add to head.
3340         */
3341        init_chain_block(offset, next, bucket, size);
3342        chain_block_buckets[bucket] = offset;
3343}
3344
3345/*
3346 * Only the first block in the list can be deleted.
3347 *
3348 * For the variable size bucket[0], the first block (the largest one) is
3349 * returned, broken up and put back into the pool. So if a chain block of
3350 * length > MAX_CHAIN_BUCKETS is ever used and zapped, it will just be
3351 * queued up after the primordial chain block and never be used until the
3352 * hlock entries in the primordial chain block is almost used up. That
3353 * causes fragmentation and reduce allocation efficiency. That can be
3354 * monitored by looking at the "large chain blocks" number in lockdep_stats.
3355 */
3356static inline void del_chain_block(int bucket, int size, int next)
3357{
3358        nr_free_chain_hlocks -= size;
3359        chain_block_buckets[bucket] = next;
3360
3361        if (!bucket)
3362                nr_large_chain_blocks--;
3363}
3364
3365static void init_chain_block_buckets(void)
3366{
3367        int i;
3368
3369        for (i = 0; i < MAX_CHAIN_BUCKETS; i++)
3370                chain_block_buckets[i] = -1;
3371
3372        add_chain_block(0, ARRAY_SIZE(chain_hlocks));
3373}
3374
3375/*
3376 * Return offset of a chain block of the right size or -1 if not found.
3377 *
3378 * Fairly simple worst-fit allocator with the addition of a number of size
3379 * specific free lists.
3380 */
3381static int alloc_chain_hlocks(int req)
3382{
3383        int bucket, curr, size;
3384
3385        /*
3386         * We rely on the MSB to act as an escape bit to denote freelist
3387         * pointers. Make sure this bit isn't set in 'normal' class_idx usage.
3388         */
3389        BUILD_BUG_ON((MAX_LOCKDEP_KEYS-1) & CHAIN_BLK_FLAG);
3390
3391        init_data_structures_once();
3392
3393        if (nr_free_chain_hlocks < req)
3394                return -1;
3395
3396        /*
3397         * We require a minimum of 2 (u16) entries to encode a freelist
3398         * 'pointer'.
3399         */
3400        req = max(req, 2);
3401        bucket = size_to_bucket(req);
3402        curr = chain_block_buckets[bucket];
3403
3404        if (bucket) {
3405                if (curr >= 0) {
3406                        del_chain_block(bucket, req, chain_block_next(curr));
3407                        return curr;
3408                }
3409                /* Try bucket 0 */
3410                curr = chain_block_buckets[0];
3411        }
3412
3413        /*
3414         * The variable sized freelist is sorted by size; the first entry is
3415         * the largest. Use it if it fits.
3416         */
3417        if (curr >= 0) {
3418                size = chain_block_size(curr);
3419                if (likely(size >= req)) {
3420                        del_chain_block(0, size, chain_block_next(curr));
3421                        add_chain_block(curr + req, size - req);
3422                        return curr;
3423                }
3424        }
3425
3426        /*
3427         * Last resort, split a block in a larger sized bucket.
3428         */
3429        for (size = MAX_CHAIN_BUCKETS; size > req; size--) {
3430                bucket = size_to_bucket(size);
3431                curr = chain_block_buckets[bucket];
3432                if (curr < 0)
3433                        continue;
3434
3435                del_chain_block(bucket, size, chain_block_next(curr));
3436                add_chain_block(curr + req, size - req);
3437                return curr;
3438        }
3439
3440        return -1;
3441}
3442
3443static inline void free_chain_hlocks(int base, int size)
3444{
3445        add_chain_block(base, max(size, 2));
3446}
3447
3448struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
3449{
3450        u16 chain_hlock = chain_hlocks[chain->base + i];
3451        unsigned int class_idx = chain_hlock_class_idx(chain_hlock);
3452
3453        return lock_classes + class_idx - 1;
3454}
3455
3456/*
3457 * Returns the index of the first held_lock of the current chain
3458 */
3459static inline int get_first_held_lock(struct task_struct *curr,
3460                                        struct held_lock *hlock)
3461{
3462        int i;
3463        struct held_lock *hlock_curr;
3464
3465        for (i = curr->lockdep_depth - 1; i >= 0; i--) {
3466                hlock_curr = curr->held_locks + i;
3467                if (hlock_curr->irq_context != hlock->irq_context)
3468                        break;
3469
3470        }
3471
3472        return ++i;
3473}
3474
3475#ifdef CONFIG_DEBUG_LOCKDEP
3476/*
3477 * Returns the next chain_key iteration
3478 */
3479static u64 print_chain_key_iteration(u16 hlock_id, u64 chain_key)
3480{
3481        u64 new_chain_key = iterate_chain_key(chain_key, hlock_id);
3482
3483        printk(" hlock_id:%d -> chain_key:%016Lx",
3484                (unsigned int)hlock_id,
3485                (unsigned long long)new_chain_key);
3486        return new_chain_key;
3487}
3488
3489static void
3490print_chain_keys_held_locks(struct task_struct *curr, struct held_lock *hlock_next)
3491{
3492        struct held_lock *hlock;
3493        u64 chain_key = INITIAL_CHAIN_KEY;
3494        int depth = curr->lockdep_depth;
3495        int i = get_first_held_lock(curr, hlock_next);
3496
3497        printk("depth: %u (irq_context %u)\n", depth - i + 1,
3498                hlock_next->irq_context);
3499        for (; i < depth; i++) {
3500                hlock = curr->held_locks + i;
3501                chain_key = print_chain_key_iteration(hlock_id(hlock), chain_key);
3502
3503                print_lock(hlock);
3504        }
3505
3506        print_chain_key_iteration(hlock_id(hlock_next), chain_key);
3507        print_lock(hlock_next);
3508}
3509
3510static void print_chain_keys_chain(struct lock_chain *chain)
3511{
3512        int i;
3513        u64 chain_key = INITIAL_CHAIN_KEY;
3514        u16 hlock_id;
3515
3516        printk("depth: %u\n", chain->depth);
3517        for (i = 0; i < chain->depth; i++) {
3518                hlock_id = chain_hlocks[chain->base + i];
3519                chain_key = print_chain_key_iteration(hlock_id, chain_key);
3520
3521                print_lock_name(lock_classes + chain_hlock_class_idx(hlock_id) - 1);
3522                printk("\n");
3523        }
3524}
3525
3526static void print_collision(struct task_struct *curr,
3527                        struct held_lock *hlock_next,
3528                        struct lock_chain *chain)
3529{
3530        pr_warn("\n");
3531        pr_warn("============================\n");
3532        pr_warn("WARNING: chain_key collision\n");
3533        print_kernel_ident();
3534        pr_warn("----------------------------\n");
3535        pr_warn("%s/%d: ", current->comm, task_pid_nr(current));
3536        pr_warn("Hash chain already cached but the contents don't match!\n");
3537
3538        pr_warn("Held locks:");
3539        print_chain_keys_held_locks(curr, hlock_next);
3540
3541        pr_warn("Locks in cached chain:");
3542        print_chain_keys_chain(chain);
3543
3544        pr_warn("\nstack backtrace:\n");
3545        dump_stack();
3546}
3547#endif
3548
3549/*
3550 * Checks whether the chain and the current held locks are consistent
3551 * in depth and also in content. If they are not it most likely means
3552 * that there was a collision during the calculation of the chain_key.
3553 * Returns: 0 not passed, 1 passed
3554 */
3555static int check_no_collision(struct task_struct *curr,
3556                        struct held_lock *hlock,
3557                        struct lock_chain *chain)
3558{
3559#ifdef CONFIG_DEBUG_LOCKDEP
3560        int i, j, id;
3561
3562        i = get_first_held_lock(curr, hlock);
3563
3564        if (DEBUG_LOCKS_WARN_ON(chain->depth != curr->lockdep_depth - (i - 1))) {
3565                print_collision(curr, hlock, chain);
3566                return 0;
3567        }
3568
3569        for (j = 0; j < chain->depth - 1; j++, i++) {
3570                id = hlock_id(&curr->held_locks[i]);
3571
3572                if (DEBUG_LOCKS_WARN_ON(chain_hlocks[chain->base + j] != id)) {
3573                        print_collision(curr, hlock, chain);
3574                        return 0;
3575                }
3576        }
3577#endif
3578        return 1;
3579}
3580
3581/*
3582 * Given an index that is >= -1, return the index of the next lock chain.
3583 * Return -2 if there is no next lock chain.
3584 */
3585long lockdep_next_lockchain(long i)
3586{
3587        i = find_next_bit(lock_chains_in_use, ARRAY_SIZE(lock_chains), i + 1);
3588        return i < ARRAY_SIZE(lock_chains) ? i : -2;
3589}
3590
3591unsigned long lock_chain_count(void)
3592{
3593        return bitmap_weight(lock_chains_in_use, ARRAY_SIZE(lock_chains));
3594}
3595
3596/* Must be called with the graph lock held. */
3597static struct lock_chain *alloc_lock_chain(void)
3598{
3599        int idx = find_first_zero_bit(lock_chains_in_use,
3600                                      ARRAY_SIZE(lock_chains));
3601
3602        if (unlikely(idx >= ARRAY_SIZE(lock_chains)))
3603                return NULL;
3604        __set_bit(idx, lock_chains_in_use);
3605        return lock_chains + idx;
3606}
3607
3608/*
3609 * Adds a dependency chain into chain hashtable. And must be called with
3610 * graph_lock held.
3611 *
3612 * Return 0 if fail, and graph_lock is released.
3613 * Return 1 if succeed, with graph_lock held.
3614 */
3615static inline int add_chain_cache(struct task_struct *curr,
3616                                  struct held_lock *hlock,
3617                                  u64 chain_key)
3618{
3619        struct hlist_head *hash_head = chainhashentry(chain_key);
3620        struct lock_chain *chain;
3621        int i, j;
3622
3623        /*
3624         * The caller must hold the graph lock, ensure we've got IRQs
3625         * disabled to make this an IRQ-safe lock.. for recursion reasons
3626         * lockdep won't complain about its own locking errors.
3627         */
3628        if (lockdep_assert_locked())
3629                return 0;
3630
3631        chain = alloc_lock_chain();
3632        if (!chain) {
3633                if (!debug_locks_off_graph_unlock())
3634                        return 0;
3635
3636                print_lockdep_off("BUG: MAX_LOCKDEP_CHAINS too low!");
3637                dump_stack();
3638                return 0;
3639        }
3640        chain->chain_key = chain_key;
3641        chain->irq_context = hlock->irq_context;
3642        i = get_first_held_lock(curr, hlock);
3643        chain->depth = curr->lockdep_depth + 1 - i;
3644
3645        BUILD_BUG_ON((1UL << 24) <= ARRAY_SIZE(chain_hlocks));
3646        BUILD_BUG_ON((1UL << 6)  <= ARRAY_SIZE(curr->held_locks));
3647        BUILD_BUG_ON((1UL << 8*sizeof(chain_hlocks[0])) <= ARRAY_SIZE(lock_classes));
3648
3649        j = alloc_chain_hlocks(chain->depth);
3650        if (j < 0) {
3651                if (!debug_locks_off_graph_unlock())
3652                        return 0;
3653
3654                print_lockdep_off("BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!");
3655                dump_stack();
3656                return 0;
3657        }
3658
3659        chain->base = j;
3660        for (j = 0; j < chain->depth - 1; j++, i++) {
3661                int lock_id = hlock_id(curr->held_locks + i);
3662
3663                chain_hlocks[chain->base + j] = lock_id;
3664        }
3665        chain_hlocks[chain->base + j] = hlock_id(hlock);
3666        hlist_add_head_rcu(&chain->entry, hash_head);
3667        debug_atomic_inc(chain_lookup_misses);
3668        inc_chains(chain->irq_context);
3669
3670        return 1;
3671}
3672
3673/*
3674 * Look up a dependency chain. Must be called with either the graph lock or
3675 * the RCU read lock held.
3676 */
3677static inline struct lock_chain *lookup_chain_cache(u64 chain_key)
3678{
3679        struct hlist_head *hash_head = chainhashentry(chain_key);
3680        struct lock_chain *chain;
3681
3682        hlist_for_each_entry_rcu(chain, hash_head, entry) {
3683                if (READ_ONCE(chain->chain_key) == chain_key) {
3684                        debug_atomic_inc(chain_lookup_hits);
3685                        return chain;
3686                }
3687        }
3688        return NULL;
3689}
3690
3691/*
3692 * If the key is not present yet in dependency chain cache then
3693 * add it and return 1 - in this case the new dependency chain is
3694 * validated. If the key is already hashed, return 0.
3695 * (On return with 1 graph_lock is held.)
3696 */
3697static inline int lookup_chain_cache_add(struct task_struct *curr,
3698                                         struct held_lock *hlock,
3699                                         u64 chain_key)
3700{
3701        struct lock_class *class = hlock_class(hlock);
3702        struct lock_chain *chain = lookup_chain_cache(chain_key);
3703
3704        if (chain) {
3705cache_hit:
3706                if (!check_no_collision(curr, hlock, chain))
3707                        return 0;
3708
3709                if (very_verbose(class)) {
3710                        printk("\nhash chain already cached, key: "
3711                                        "%016Lx tail class: [%px] %s\n",
3712                                        (unsigned long long)chain_key,
3713                                        class->key, class->name);
3714                }
3715
3716                return 0;
3717        }
3718
3719        if (very_verbose(class)) {
3720                printk("\nnew hash chain, key: %016Lx tail class: [%px] %s\n",
3721                        (unsigned long long)chain_key, class->key, class->name);
3722        }
3723
3724        if (!graph_lock())
3725                return 0;
3726
3727        /*
3728         * We have to walk the chain again locked - to avoid duplicates:
3729         */
3730        chain = lookup_chain_cache(chain_key);
3731        if (chain) {
3732                graph_unlock();
3733                goto cache_hit;
3734        }
3735
3736        if (!add_chain_cache(curr, hlock, chain_key))
3737                return 0;
3738
3739        return 1;
3740}
3741
3742static int validate_chain(struct task_struct *curr,
3743                          struct held_lock *hlock,
3744                          int chain_head, u64 chain_key)
3745{
3746        /*
3747         * Trylock needs to maintain the stack of held locks, but it
3748         * does not add new dependencies, because trylock can be done
3749         * in any order.
3750         *
3751         * We look up the chain_key and do the O(N^2) check and update of
3752         * the dependencies only if this is a new dependency chain.
3753         * (If lookup_chain_cache_add() return with 1 it acquires
3754         * graph_lock for us)
3755         */
3756        if (!hlock->trylock && hlock->check &&
3757            lookup_chain_cache_add(curr, hlock, chain_key)) {
3758                /*
3759                 * Check whether last held lock:
3760                 *
3761                 * - is irq-safe, if this lock is irq-unsafe
3762                 * - is softirq-safe, if this lock is hardirq-unsafe
3763                 *
3764                 * And check whether the new lock's dependency graph
3765                 * could lead back to the previous lock:
3766                 *
3767                 * - within the current held-lock stack
3768                 * - across our accumulated lock dependency records
3769                 *
3770                 * any of these scenarios could lead to a deadlock.
3771                 */
3772                /*
3773                 * The simple case: does the current hold the same lock
3774                 * already?
3775                 */
3776                int ret = check_deadlock(curr, hlock);
3777
3778                if (!ret)
3779                        return 0;
3780                /*
3781                 * Add dependency only if this lock is not the head
3782                 * of the chain, and if the new lock introduces no more
3783                 * lock dependency (because we already hold a lock with the
3784                 * same lock class) nor deadlock (because the nest_lock
3785                 * serializes nesting locks), see the comments for
3786                 * check_deadlock().
3787                 */
3788                if (!chain_head && ret != 2) {
3789                        if (!check_prevs_add(curr, hlock))
3790                                return 0;
3791                }
3792
3793                graph_unlock();
3794        } else {
3795                /* after lookup_chain_cache_add(): */
3796                if (unlikely(!debug_locks))
3797                        return 0;
3798        }
3799
3800        return 1;
3801}
3802#else
3803static inline int validate_chain(struct task_struct *curr,
3804                                 struct held_lock *hlock,
3805                                 int chain_head, u64 chain_key)
3806{
3807        return 1;
3808}
3809
3810static void init_chain_block_buckets(void)      { }
3811#endif /* CONFIG_PROVE_LOCKING */
3812
3813/*
3814 * We are building curr_chain_key incrementally, so double-check
3815 * it from scratch, to make sure that it's done correctly:
3816 */
3817static void check_chain_key(struct task_struct *curr)
3818{
3819#ifdef CONFIG_DEBUG_LOCKDEP
3820        struct held_lock *hlock, *prev_hlock = NULL;
3821        unsigned int i;
3822        u64 chain_key = INITIAL_CHAIN_KEY;
3823
3824        for (i = 0; i < curr->lockdep_depth; i++) {
3825                hlock = curr->held_locks + i;
3826                if (chain_key != hlock->prev_chain_key) {
3827                        debug_locks_off();
3828                        /*
3829                         * We got mighty confused, our chain keys don't match
3830                         * with what we expect, someone trample on our task state?
3831                         */
3832                        WARN(1, "hm#1, depth: %u [%u], %016Lx != %016Lx\n",
3833                                curr->lockdep_depth, i,
3834                                (unsigned long long)chain_key,
3835                                (unsigned long long)hlock->prev_chain_key);
3836                        return;
3837                }
3838
3839                /*
3840                 * hlock->class_idx can't go beyond MAX_LOCKDEP_KEYS, but is
3841                 * it registered lock class index?
3842                 */
3843                if (DEBUG_LOCKS_WARN_ON(!test_bit(hlock->class_idx, lock_classes_in_use)))
3844                        return;
3845
3846                if (prev_hlock && (prev_hlock->irq_context !=
3847                                                        hlock->irq_context))
3848                        chain_key = INITIAL_CHAIN_KEY;
3849                chain_key = iterate_chain_key(chain_key, hlock_id(hlock));
3850                prev_hlock = hlock;
3851        }
3852        if (chain_key != curr->curr_chain_key) {
3853                debug_locks_off();
3854                /*
3855                 * More smoking hash instead of calculating it, damn see these
3856                 * numbers float.. I bet that a pink elephant stepped on my memory.
3857                 */
3858                WARN(1, "hm#2, depth: %u [%u], %016Lx != %016Lx\n",
3859                        curr->lockdep_depth, i,
3860                        (unsigned long long)chain_key,
3861                        (unsigned long long)curr->curr_chain_key);
3862        }
3863#endif
3864}
3865
3866#ifdef CONFIG_PROVE_LOCKING
3867static int mark_lock(struct task_struct *curr, struct held_lock *this,
3868                     enum lock_usage_bit new_bit);
3869
3870static void print_usage_bug_scenario(struct held_lock *lock)
3871{
3872        struct lock_class *class = hlock_class(lock);
3873
3874        printk(" Possible unsafe locking scenario:\n\n");
3875        printk("       CPU0\n");
3876        printk("       ----\n");
3877        printk("  lock(");
3878        __print_lock_name(class);
3879        printk(KERN_CONT ");\n");
3880        printk("  <Interrupt>\n");
3881        printk("    lock(");
3882        __print_lock_name(class);
3883        printk(KERN_CONT ");\n");
3884        printk("\n *** DEADLOCK ***\n\n");
3885}
3886
3887static void
3888print_usage_bug(struct task_struct *curr, struct held_lock *this,
3889                enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
3890{
3891        if (!debug_locks_off() || debug_locks_silent)
3892                return;
3893
3894        pr_warn("\n");
3895        pr_warn("================================\n");
3896        pr_warn("WARNING: inconsistent lock state\n");
3897        print_kernel_ident();
3898        pr_warn("--------------------------------\n");
3899
3900        pr_warn("inconsistent {%s} -> {%s} usage.\n",
3901                usage_str[prev_bit], usage_str[new_bit]);
3902
3903        pr_warn("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] takes:\n",
3904                curr->comm, task_pid_nr(curr),
3905                lockdep_hardirq_context(), hardirq_count() >> HARDIRQ_SHIFT,
3906                lockdep_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT,
3907                lockdep_hardirqs_enabled(),
3908                lockdep_softirqs_enabled(curr));
3909        print_lock(this);
3910
3911        pr_warn("{%s} state was registered at:\n", usage_str[prev_bit]);
3912        print_lock_trace(hlock_class(this)->usage_traces[prev_bit], 1);
3913
3914        print_irqtrace_events(curr);
3915        pr_warn("\nother info that might help us debug this:\n");
3916        print_usage_bug_scenario(this);
3917
3918        lockdep_print_held_locks(curr);
3919
3920        pr_warn("\nstack backtrace:\n");
3921        dump_stack();
3922}
3923
3924/*
3925 * Print out an error if an invalid bit is set:
3926 */
3927static inline int
3928valid_state(struct task_struct *curr, struct held_lock *this,
3929            enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit)
3930{
3931        if (unlikely(hlock_class(this)->usage_mask & (1 << bad_bit))) {
3932                graph_unlock();
3933                print_usage_bug(curr, this, bad_bit, new_bit);
3934                return 0;
3935        }
3936        return 1;
3937}
3938
3939
3940/*
3941 * print irq inversion bug:
3942 */
3943static void
3944print_irq_inversion_bug(struct task_struct *curr,
3945                        struct lock_list *root, struct lock_list *other,
3946                        struct held_lock *this, int forwards,
3947                        const char *irqclass)
3948{
3949        struct lock_list *entry = other;
3950        struct lock_list *middle = NULL;
3951        int depth;
3952
3953        if (!debug_locks_off_graph_unlock() || debug_locks_silent)
3954                return;
3955
3956        pr_warn("\n");
3957        pr_warn("========================================================\n");
3958        pr_warn("WARNING: possible irq lock inversion dependency detected\n");
3959        print_kernel_ident();
3960        pr_warn("--------------------------------------------------------\n");
3961        pr_warn("%s/%d just changed the state of lock:\n",
3962                curr->comm, task_pid_nr(curr));
3963        print_lock(this);
3964        if (forwards)
3965                pr_warn("but this lock took another, %s-unsafe lock in the past:\n", irqclass);
3966        else
3967                pr_warn("but this lock was taken by another, %s-safe lock in the past:\n", irqclass);
3968        print_lock_name(other->class);
3969        pr_warn("\n\nand interrupts could create inverse lock ordering between them.\n\n");
3970
3971        pr_warn("\nother info that might help us debug this:\n");
3972
3973        /* Find a middle lock (if one exists) */
3974        depth = get_lock_depth(other);
3975        do {
3976                if (depth == 0 && (entry != root)) {
3977                        pr_warn("lockdep:%s bad path found in chain graph\n", __func__);
3978                        break;
3979                }
3980                middle = entry;
3981                entry = get_lock_parent(entry);
3982                depth--;
3983        } while (entry && entry != root && (depth >= 0));
3984        if (forwards)
3985                print_irq_lock_scenario(root, other,
3986                        middle ? middle->class : root->class, other->class);
3987        else
3988                print_irq_lock_scenario(other, root,
3989                        middle ? middle->class : other->class, root->class);
3990
3991        lockdep_print_held_locks(curr);
3992
3993        pr_warn("\nthe shortest dependencies between 2nd lock and 1st lock:\n");
3994        root->trace = save_trace();
3995        if (!root->trace)
3996                return;
3997        print_shortest_lock_dependencies(other, root);
3998
3999        pr_warn("\nstack backtrace:\n");
4000        dump_stack();
4001}
4002
4003/*
4004 * Prove that in the forwards-direction subgraph starting at <this>
4005 * there is no lock matching <mask>:
4006 */
4007static int
4008check_usage_forwards(struct task_struct *curr, struct held_lock *this,
4009                     enum lock_usage_bit bit)
4010{
4011        enum bfs_result ret;
4012        struct lock_list root;
4013        struct lock_list *target_entry;
4014        enum lock_usage_bit read_bit = bit + LOCK_USAGE_READ_MASK;
4015        unsigned usage_mask = lock_flag(bit) | lock_flag(read_bit);
4016
4017        bfs_init_root(&root, this);
4018        ret = find_usage_forwards(&root, usage_mask, &target_entry);
4019        if (bfs_error(ret)) {
4020                print_bfs_bug(ret);
4021                return 0;
4022        }
4023        if (ret == BFS_RNOMATCH)
4024                return 1;
4025
4026        /* Check whether write or read usage is the match */
4027        if (target_entry->class->usage_mask & lock_flag(bit)) {
4028                print_irq_inversion_bug(curr, &root, target_entry,
4029                                        this, 1, state_name(bit));
4030        } else {
4031                print_irq_inversion_bug(curr, &root, target_entry,
4032                                        this, 1, state_name(read_bit));
4033        }
4034
4035        return 0;
4036}
4037
4038/*
4039 * Prove that in the backwards-direction subgraph starting at <this>
4040 * there is no lock matching <mask>:
4041 */
4042static int
4043check_usage_backwards(struct task_struct *curr, struct held_lock *this,
4044                      enum lock_usage_bit bit)
4045{
4046        enum bfs_result ret;
4047        struct lock_list root;
4048        struct lock_list *target_entry;
4049        enum lock_usage_bit read_bit = bit + LOCK_USAGE_READ_MASK;
4050        unsigned usage_mask = lock_flag(bit) | lock_flag(read_bit);
4051
4052        bfs_init_rootb(&root, this);
4053        ret = find_usage_backwards(&root, usage_mask, &target_entry);
4054        if (bfs_error(ret)) {
4055                print_bfs_bug(ret);
4056                return 0;
4057        }
4058        if (ret == BFS_RNOMATCH)
4059                return 1;
4060
4061        /* Check whether write or read usage is the match */
4062        if (target_entry->class->usage_mask & lock_flag(bit)) {
4063                print_irq_inversion_bug(curr, &root, target_entry,
4064                                        this, 0, state_name(bit));
4065        } else {
4066                print_irq_inversion_bug(curr, &root, target_entry,
4067                                        this, 0, state_name(read_bit));
4068        }
4069
4070        return 0;
4071}
4072
4073void print_irqtrace_events(struct task_struct *curr)
4074{
4075        const struct irqtrace_events *trace = &curr->irqtrace;
4076
4077        printk("irq event stamp: %u\n", trace->irq_events);
4078        printk("hardirqs last  enabled at (%u): [<%px>] %pS\n",
4079                trace->hardirq_enable_event, (void *)trace->hardirq_enable_ip,
4080                (void *)trace->hardirq_enable_ip);
4081        printk("hardirqs last disabled at (%u): [<%px>] %pS\n",
4082                trace->hardirq_disable_event, (void *)trace->hardirq_disable_ip,
4083                (void *)trace->hardirq_disable_ip);
4084        printk("softirqs last  enabled at (%u): [<%px>] %pS\n",
4085                trace->softirq_enable_event, (void *)trace->softirq_enable_ip,
4086                (void *)trace->softirq_enable_ip);
4087        printk("softirqs last disabled at (%u): [<%px>] %pS\n",
4088                trace->softirq_disable_event, (void *)trace->softirq_disable_ip,
4089                (void *)trace->softirq_disable_ip);
4090}
4091
4092static int HARDIRQ_verbose(struct lock_class *class)
4093{
4094#if HARDIRQ_VERBOSE
4095        return class_filter(class);
4096#endif
4097        return 0;
4098}
4099
4100static int SOFTIRQ_verbose(struct lock_class *class)
4101{
4102#if SOFTIRQ_VERBOSE
4103        return class_filter(class);
4104#endif
4105        return 0;
4106}
4107
4108static int (*state_verbose_f[])(struct lock_class *class) = {
4109#define LOCKDEP_STATE(__STATE) \
4110        __STATE##_verbose,
4111#include "lockdep_states.h"
4112#undef LOCKDEP_STATE
4113};
4114
4115static inline int state_verbose(enum lock_usage_bit bit,
4116                                struct lock_class *class)
4117{
4118        return state_verbose_f[bit >> LOCK_USAGE_DIR_MASK](class);
4119}
4120
4121typedef int (*check_usage_f)(struct task_struct *, struct held_lock *,
4122                             enum lock_usage_bit bit, const char *name);
4123
4124static int
4125mark_lock_irq(struct task_struct *curr, struct held_lock *this,
4126                enum lock_usage_bit new_bit)
4127{
4128        int excl_bit = exclusive_bit(new_bit);
4129        int read = new_bit & LOCK_USAGE_READ_MASK;
4130        int dir = new_bit & LOCK_USAGE_DIR_MASK;
4131
4132        /*
4133         * Validate that this particular lock does not have conflicting
4134         * usage states.
4135         */
4136        if (!valid_state(curr, this, new_bit, excl_bit))
4137                return 0;
4138
4139        /*
4140         * Check for read in write conflicts
4141         */
4142        if (!read && !valid_state(curr, this, new_bit,
4143                                  excl_bit + LOCK_USAGE_READ_MASK))
4144                return 0;
4145
4146
4147        /*
4148         * Validate that the lock dependencies don't have conflicting usage
4149         * states.
4150         */
4151        if (dir) {
4152                /*
4153                 * mark ENABLED has to look backwards -- to ensure no dependee
4154                 * has USED_IN state, which, again, would allow  recursion deadlocks.
4155                 */
4156                if (!check_usage_backwards(curr, this, excl_bit))
4157                        return 0;
4158        } else {
4159                /*
4160                 * mark USED_IN has to look forwards -- to ensure no dependency
4161                 * has ENABLED state, which would allow recursion deadlocks.
4162                 */
4163                if (!check_usage_forwards(curr, this, excl_bit))
4164                        return 0;
4165        }
4166
4167        if (state_verbose(new_bit, hlock_class(this)))
4168                return 2;
4169
4170        return 1;
4171}
4172
4173/*
4174 * Mark all held locks with a usage bit:
4175 */
4176static int
4177mark_held_locks(struct task_struct *curr, enum lock_usage_bit base_bit)
4178{
4179        struct held_lock *hlock;
4180        int i;
4181
4182        for (i = 0; i < curr->lockdep_depth; i++) {
4183                enum lock_usage_bit hlock_bit = base_bit;
4184                hlock = curr->held_locks + i;
4185
4186                if (hlock->read)
4187                        hlock_bit += LOCK_USAGE_READ_MASK;
4188
4189                BUG_ON(hlock_bit >= LOCK_USAGE_STATES);
4190
4191                if (!hlock->check)
4192                        continue;
4193
4194                if (!mark_lock(curr, hlock, hlock_bit))
4195                        return 0;
4196        }
4197
4198        return 1;
4199}
4200
4201/*
4202 * Hardirqs will be enabled:
4203 */
4204static void __trace_hardirqs_on_caller(void)
4205{
4206        struct task_struct *curr = current;
4207
4208        /*
4209         * We are going to turn hardirqs on, so set the
4210         * usage bit for all held locks:
4211         */
4212        if (!mark_held_locks(curr, LOCK_ENABLED_HARDIRQ))
4213                return;
4214        /*
4215         * If we have softirqs enabled, then set the usage
4216         * bit for all held locks. (disabled hardirqs prevented
4217         * this bit from being set before)
4218         */
4219        if (curr->softirqs_enabled)
4220                mark_held_locks(curr, LOCK_ENABLED_SOFTIRQ);
4221}
4222
4223/**
4224 * lockdep_hardirqs_on_prepare - Prepare for enabling interrupts
4225 * @ip:         Caller address
4226 *
4227 * Invoked before a possible transition to RCU idle from exit to user or
4228 * guest mode. This ensures that all RCU operations are done before RCU
4229 * stops watching. After the RCU transition lockdep_hardirqs_on() has to be
4230 * invoked to set the final state.
4231 */
4232void lockdep_hardirqs_on_prepare(unsigned long ip)
4233{
4234        if (unlikely(!debug_locks))
4235                return;
4236
4237        /*
4238         * NMIs do not (and cannot) track lock dependencies, nothing to do.
4239         */
4240        if (unlikely(in_nmi()))
4241                return;
4242
4243        if (unlikely(this_cpu_read(lockdep_recursion)))
4244                return;
4245
4246        if (unlikely(lockdep_hardirqs_enabled())) {
4247                /*
4248                 * Neither irq nor preemption are disabled here
4249                 * so this is racy by nature but losing one hit
4250                 * in a stat is not a big deal.
4251                 */
4252                __debug_atomic_inc(redundant_hardirqs_on);
4253                return;
4254        }
4255
4256        /*
4257         * We're enabling irqs and according to our state above irqs weren't
4258         * already enabled, yet we find the hardware thinks they are in fact
4259         * enabled.. someone messed up their IRQ state tracing.
4260         */
4261        if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4262                return;
4263
4264        /*
4265         * See the fine text that goes along with this variable definition.
4266         */
4267        if (DEBUG_LOCKS_WARN_ON(early_boot_irqs_disabled))
4268                return;
4269
4270        /*
4271         * Can't allow enabling interrupts while in an interrupt handler,
4272         * that's general bad form and such. Recursion, limited stack etc..
4273         */
4274        if (DEBUG_LOCKS_WARN_ON(lockdep_hardirq_context()))
4275                return;
4276
4277        current->hardirq_chain_key = current->curr_chain_key;
4278
4279        lockdep_recursion_inc();
4280        __trace_hardirqs_on_caller();
4281        lockdep_recursion_finish();
4282}
4283EXPORT_SYMBOL_GPL(lockdep_hardirqs_on_prepare);
4284
4285void noinstr lockdep_hardirqs_on(unsigned long ip)
4286{
4287        struct irqtrace_events *trace = &current->irqtrace;
4288
4289        if (unlikely(!debug_locks))
4290                return;
4291
4292        /*
4293         * NMIs can happen in the middle of local_irq_{en,dis}able() where the
4294         * tracking state and hardware state are out of sync.
4295         *
4296         * NMIs must save lockdep_hardirqs_enabled() to restore IRQ state from,
4297         * and not rely on hardware state like normal interrupts.
4298         */
4299        if (unlikely(in_nmi())) {
4300                if (!IS_ENABLED(CONFIG_TRACE_IRQFLAGS_NMI))
4301                        return;
4302
4303                /*
4304                 * Skip:
4305                 *  - recursion check, because NMI can hit lockdep;
4306                 *  - hardware state check, because above;
4307                 *  - chain_key check, see lockdep_hardirqs_on_prepare().
4308                 */
4309                goto skip_checks;
4310        }
4311
4312        if (unlikely(this_cpu_read(lockdep_recursion)))
4313                return;
4314
4315        if (lockdep_hardirqs_enabled()) {
4316                /*
4317                 * Neither irq nor preemption are disabled here
4318                 * so this is racy by nature but losing one hit
4319                 * in a stat is not a big deal.
4320                 */
4321                __debug_atomic_inc(redundant_hardirqs_on);
4322                return;
4323        }
4324
4325        /*
4326         * We're enabling irqs and according to our state above irqs weren't
4327         * already enabled, yet we find the hardware thinks they are in fact
4328         * enabled.. someone messed up their IRQ state tracing.
4329         */
4330        if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4331                return;
4332
4333        /*
4334         * Ensure the lock stack remained unchanged between
4335         * lockdep_hardirqs_on_prepare() and lockdep_hardirqs_on().
4336         */
4337        DEBUG_LOCKS_WARN_ON(current->hardirq_chain_key !=
4338                            current->curr_chain_key);
4339
4340skip_checks:
4341        /* we'll do an OFF -> ON transition: */
4342        __this_cpu_write(hardirqs_enabled, 1);
4343        trace->hardirq_enable_ip = ip;
4344        trace->hardirq_enable_event = ++trace->irq_events;
4345        debug_atomic_inc(hardirqs_on_events);
4346}
4347EXPORT_SYMBOL_GPL(lockdep_hardirqs_on);
4348
4349/*
4350 * Hardirqs were disabled:
4351 */
4352void noinstr lockdep_hardirqs_off(unsigned long ip)
4353{
4354        if (unlikely(!debug_locks))
4355                return;
4356
4357        /*
4358         * Matching lockdep_hardirqs_on(), allow NMIs in the middle of lockdep;
4359         * they will restore the software state. This ensures the software
4360         * state is consistent inside NMIs as well.
4361         */
4362        if (in_nmi()) {
4363                if (!IS_ENABLED(CONFIG_TRACE_IRQFLAGS_NMI))
4364                        return;
4365        } else if (__this_cpu_read(lockdep_recursion))
4366                return;
4367
4368        /*
4369         * So we're supposed to get called after you mask local IRQs, but for
4370         * some reason the hardware doesn't quite think you did a proper job.
4371         */
4372        if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4373                return;
4374
4375        if (lockdep_hardirqs_enabled()) {
4376                struct irqtrace_events *trace = &current->irqtrace;
4377
4378                /*
4379                 * We have done an ON -> OFF transition:
4380                 */
4381                __this_cpu_write(hardirqs_enabled, 0);
4382                trace->hardirq_disable_ip = ip;
4383                trace->hardirq_disable_event = ++trace->irq_events;
4384                debug_atomic_inc(hardirqs_off_events);
4385        } else {
4386                debug_atomic_inc(redundant_hardirqs_off);
4387        }
4388}
4389EXPORT_SYMBOL_GPL(lockdep_hardirqs_off);
4390
4391/*
4392 * Softirqs will be enabled:
4393 */
4394void lockdep_softirqs_on(unsigned long ip)
4395{
4396        struct irqtrace_events *trace = &current->irqtrace;
4397
4398        if (unlikely(!lockdep_enabled()))
4399                return;
4400
4401        /*
4402         * We fancy IRQs being disabled here, see softirq.c, avoids
4403         * funny state and nesting things.
4404         */
4405        if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4406                return;
4407
4408        if (current->softirqs_enabled) {
4409                debug_atomic_inc(redundant_softirqs_on);
4410                return;
4411        }
4412
4413        lockdep_recursion_inc();
4414        /*
4415         * We'll do an OFF -> ON transition:
4416         */
4417        current->softirqs_enabled = 1;
4418        trace->softirq_enable_ip = ip;
4419        trace->softirq_enable_event = ++trace->irq_events;
4420        debug_atomic_inc(softirqs_on_events);
4421        /*
4422         * We are going to turn softirqs on, so set the
4423         * usage bit for all held locks, if hardirqs are
4424         * enabled too:
4425         */
4426        if (lockdep_hardirqs_enabled())
4427                mark_held_locks(current, LOCK_ENABLED_SOFTIRQ);
4428        lockdep_recursion_finish();
4429}
4430
4431/*
4432 * Softirqs were disabled:
4433 */
4434void lockdep_softirqs_off(unsigned long ip)
4435{
4436        if (unlikely(!lockdep_enabled()))
4437                return;
4438
4439        /*
4440         * We fancy IRQs being disabled here, see softirq.c
4441         */
4442        if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4443                return;
4444
4445        if (current->softirqs_enabled) {
4446                struct irqtrace_events *trace = &current->irqtrace;
4447
4448                /*
4449                 * We have done an ON -> OFF transition:
4450                 */
4451                current->softirqs_enabled = 0;
4452                trace->softirq_disable_ip = ip;
4453                trace->softirq_disable_event = ++trace->irq_events;
4454                debug_atomic_inc(softirqs_off_events);
4455                /*
4456                 * Whoops, we wanted softirqs off, so why aren't they?
4457                 */
4458                DEBUG_LOCKS_WARN_ON(!softirq_count());
4459        } else
4460                debug_atomic_inc(redundant_softirqs_off);
4461}
4462
4463static int
4464mark_usage(struct task_struct *curr, struct held_lock *hlock, int check)
4465{
4466        if (!check)
4467                goto lock_used;
4468
4469        /*
4470         * If non-trylock use in a hardirq or softirq context, then
4471         * mark the lock as used in these contexts:
4472         */
4473        if (!hlock->trylock) {
4474                if (hlock->read) {
4475                        if (lockdep_hardirq_context())
4476                                if (!mark_lock(curr, hlock,
4477                                                LOCK_USED_IN_HARDIRQ_READ))
4478                                        return 0;
4479                        if (curr->softirq_context)
4480                                if (!mark_lock(curr, hlock,
4481                                                LOCK_USED_IN_SOFTIRQ_READ))
4482                                        return 0;
4483                } else {
4484                        if (lockdep_hardirq_context())
4485                                if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ))
4486                                        return 0;
4487                        if (curr->softirq_context)
4488                                if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ))
4489                                        return 0;
4490                }
4491        }
4492        if (!hlock->hardirqs_off) {
4493                if (hlock->read) {
4494                        if (!mark_lock(curr, hlock,
4495                                        LOCK_ENABLED_HARDIRQ_READ))
4496                                return 0;
4497                        if (curr->softirqs_enabled)
4498                                if (!mark_lock(curr, hlock,
4499                                                LOCK_ENABLED_SOFTIRQ_READ))
4500                                        return 0;
4501                } else {
4502                        if (!mark_lock(curr, hlock,
4503                                        LOCK_ENABLED_HARDIRQ))
4504                                return 0;
4505                        if (curr->softirqs_enabled)
4506                                if (!mark_lock(curr, hlock,
4507                                                LOCK_ENABLED_SOFTIRQ))
4508                                        return 0;
4509                }
4510        }
4511
4512lock_used:
4513        /* mark it as used: */
4514        if (!mark_lock(curr, hlock, LOCK_USED))
4515                return 0;
4516
4517        return 1;
4518}
4519
4520static inline unsigned int task_irq_context(struct task_struct *task)
4521{
4522        return LOCK_CHAIN_HARDIRQ_CONTEXT * !!lockdep_hardirq_context() +
4523               LOCK_CHAIN_SOFTIRQ_CONTEXT * !!task->softirq_context;
4524}
4525
4526static int separate_irq_context(struct task_struct *curr,
4527                struct held_lock *hlock)
4528{
4529        unsigned int depth = curr->lockdep_depth;
4530
4531        /*
4532         * Keep track of points where we cross into an interrupt context:
4533         */
4534        if (depth) {
4535                struct held_lock *prev_hlock;
4536
4537                prev_hlock = curr->held_locks + depth-1;
4538                /*
4539                 * If we cross into another context, reset the
4540                 * hash key (this also prevents the checking and the
4541                 * adding of the dependency to 'prev'):
4542                 */
4543                if (prev_hlock->irq_context != hlock->irq_context)
4544                        return 1;
4545        }
4546        return 0;
4547}
4548
4549/*
4550 * Mark a lock with a usage bit, and validate the state transition:
4551 */
4552static int mark_lock(struct task_struct *curr, struct held_lock *this,
4553                             enum lock_usage_bit new_bit)
4554{
4555        unsigned int new_mask, ret = 1;
4556
4557        if (new_bit >= LOCK_USAGE_STATES) {
4558                DEBUG_LOCKS_WARN_ON(1);
4559                return 0;
4560        }
4561
4562        if (new_bit == LOCK_USED && this->read)
4563                new_bit = LOCK_USED_READ;
4564
4565        new_mask = 1 << new_bit;
4566
4567        /*
4568         * If already set then do not dirty the cacheline,
4569         * nor do any checks:
4570         */
4571        if (likely(hlock_class(this)->usage_mask & new_mask))
4572                return 1;
4573
4574        if (!graph_lock())
4575                return 0;
4576        /*
4577         * Make sure we didn't race:
4578         */
4579        if (unlikely(hlock_class(this)->usage_mask & new_mask))
4580                goto unlock;
4581
4582        if (!hlock_class(this)->usage_mask)
4583                debug_atomic_dec(nr_unused_locks);
4584
4585        hlock_class(this)->usage_mask |= new_mask;
4586
4587        if (new_bit < LOCK_TRACE_STATES) {
4588                if (!(hlock_class(this)->usage_traces[new_bit] = save_trace()))
4589                        return 0;
4590        }
4591
4592        if (new_bit < LOCK_USED) {
4593                ret = mark_lock_irq(curr, this, new_bit);
4594                if (!ret)
4595                        return 0;
4596        }
4597
4598unlock:
4599        graph_unlock();
4600
4601        /*
4602         * We must printk outside of the graph_lock:
4603         */
4604        if (ret == 2) {
4605                printk("\nmarked lock as {%s}:\n", usage_str[new_bit]);
4606                print_lock(this);
4607                print_irqtrace_events(curr);
4608                dump_stack();
4609        }
4610
4611        return ret;
4612}
4613
4614static inline short task_wait_context(struct task_struct *curr)
4615{
4616        /*
4617         * Set appropriate wait type for the context; for IRQs we have to take
4618         * into account force_irqthread as that is implied by PREEMPT_RT.
4619         */
4620        if (lockdep_hardirq_context()) {
4621                /*
4622                 * Check if force_irqthreads will run us threaded.
4623                 */
4624                if (curr->hardirq_threaded || curr->irq_config)
4625                        return LD_WAIT_CONFIG;
4626
4627                return LD_WAIT_SPIN;
4628        } else if (curr->softirq_context) {
4629                /*
4630                 * Softirqs are always threaded.
4631                 */
4632                return LD_WAIT_CONFIG;
4633        }
4634
4635        return LD_WAIT_MAX;
4636}
4637
4638static int
4639print_lock_invalid_wait_context(struct task_struct *curr,
4640                                struct held_lock *hlock)
4641{
4642        short curr_inner;
4643
4644        if (!debug_locks_off())
4645                return 0;
4646        if (debug_locks_silent)
4647                return 0;
4648
4649        pr_warn("\n");
4650        pr_warn("=============================\n");
4651        pr_warn("[ BUG: Invalid wait context ]\n");
4652        print_kernel_ident();
4653        pr_warn("-----------------------------\n");
4654
4655        pr_warn("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr));
4656        print_lock(hlock);
4657
4658        pr_warn("other info that might help us debug this:\n");
4659
4660        curr_inner = task_wait_context(curr);
4661        pr_warn("context-{%d:%d}\n", curr_inner, curr_inner);
4662
4663        lockdep_print_held_locks(curr);
4664
4665        pr_warn("stack backtrace:\n");
4666        dump_stack();
4667
4668        return 0;
4669}
4670
4671/*
4672 * Verify the wait_type context.
4673 *
4674 * This check validates we takes locks in the right wait-type order; that is it
4675 * ensures that we do not take mutexes inside spinlocks and do not attempt to
4676 * acquire spinlocks inside raw_spinlocks and the sort.
4677 *
4678 * The entire thing is slightly more complex because of RCU, RCU is a lock that
4679 * can be taken from (pretty much) any context but also has constraints.
4680 * However when taken in a stricter environment the RCU lock does not loosen
4681 * the constraints.
4682 *
4683 * Therefore we must look for the strictest environment in the lock stack and
4684 * compare that to the lock we're trying to acquire.
4685 */
4686static int check_wait_context(struct task_struct *curr, struct held_lock *next)
4687{
4688        u8 next_inner = hlock_class(next)->wait_type_inner;
4689        u8 next_outer = hlock_class(next)->wait_type_outer;
4690        u8 curr_inner;
4691        int depth;
4692
4693        if (!next_inner || next->trylock)
4694                return 0;
4695
4696        if (!next_outer)
4697                next_outer = next_inner;
4698
4699        /*
4700         * Find start of current irq_context..
4701         */
4702        for (depth = curr->lockdep_depth - 1; depth >= 0; depth--) {
4703                struct held_lock *prev = curr->held_locks + depth;
4704                if (prev->irq_context != next->irq_context)
4705                        break;
4706        }
4707        depth++;
4708
4709        curr_inner = task_wait_context(curr);
4710
4711        for (; depth < curr->lockdep_depth; depth++) {
4712                struct held_lock *prev = curr->held_locks + depth;
4713                u8 prev_inner = hlock_class(prev)->wait_type_inner;
4714
4715                if (prev_inner) {
4716                        /*
4717                         * We can have a bigger inner than a previous one
4718                         * when outer is smaller than inner, as with RCU.
4719                         *
4720                         * Also due to trylocks.
4721                         */
4722                        curr_inner = min(curr_inner, prev_inner);
4723                }
4724        }
4725
4726        if (next_outer > curr_inner)
4727                return print_lock_invalid_wait_context(curr, next);
4728
4729        return 0;
4730}
4731
4732#else /* CONFIG_PROVE_LOCKING */
4733
4734static inline int
4735mark_usage(struct task_struct *curr, struct held_lock *hlock, int check)
4736{
4737        return 1;
4738}
4739
4740static inline unsigned int task_irq_context(struct task_struct *task)
4741{
4742        return 0;
4743}
4744
4745static inline int separate_irq_context(struct task_struct *curr,
4746                struct held_lock *hlock)
4747{
4748        return 0;
4749}
4750
4751static inline int check_wait_context(struct task_struct *curr,
4752                                     struct held_lock *next)
4753{
4754        return 0;
4755}
4756
4757#endif /* CONFIG_PROVE_LOCKING */
4758
4759/*
4760 * Initialize a lock instance's lock-class mapping info:
4761 */
4762void lockdep_init_map_type(struct lockdep_map *lock, const char *name,
4763                            struct lock_class_key *key, int subclass,
4764                            u8 inner, u8 outer, u8 lock_type)
4765{
4766        int i;
4767
4768        for (i = 0; i < NR_LOCKDEP_CACHING_CLASSES; i++)
4769                lock->class_cache[i] = NULL;
4770
4771#ifdef CONFIG_LOCK_STAT
4772        lock->cpu = raw_smp_processor_id();
4773#endif
4774
4775        /*
4776         * Can't be having no nameless bastards around this place!
4777         */
4778        if (DEBUG_LOCKS_WARN_ON(!name)) {
4779                lock->name = "NULL";
4780                return;
4781        }
4782
4783        lock->name = name;
4784
4785        lock->wait_type_outer = outer;
4786        lock->wait_type_inner = inner;
4787        lock->lock_type = lock_type;
4788
4789        /*
4790         * No key, no joy, we need to hash something.
4791         */
4792        if (DEBUG_LOCKS_WARN_ON(!key))
4793                return;
4794        /*
4795         * Sanity check, the lock-class key must either have been allocated
4796         * statically or must have been registered as a dynamic key.
4797         */
4798        if (!static_obj(key) && !is_dynamic_key(key)) {
4799                if (debug_locks)
4800                        printk(KERN_ERR "BUG: key %px has not been registered!\n", key);
4801                DEBUG_LOCKS_WARN_ON(1);
4802                return;
4803        }
4804        lock->key = key;
4805
4806        if (unlikely(!debug_locks))
4807                return;
4808
4809        if (subclass) {
4810                unsigned long flags;
4811
4812                if (DEBUG_LOCKS_WARN_ON(!lockdep_enabled()))
4813                        return;
4814
4815                raw_local_irq_save(flags);
4816                lockdep_recursion_inc();
4817                register_lock_class(lock, subclass, 1);
4818                lockdep_recursion_finish();
4819                raw_local_irq_restore(flags);
4820        }
4821}
4822EXPORT_SYMBOL_GPL(lockdep_init_map_type);
4823
4824struct lock_class_key __lockdep_no_validate__;
4825EXPORT_SYMBOL_GPL(__lockdep_no_validate__);
4826
4827static void
4828print_lock_nested_lock_not_held(struct task_struct *curr,
4829                                struct held_lock *hlock,
4830                                unsigned long ip)
4831{
4832        if (!debug_locks_off())
4833                return;
4834        if (debug_locks_silent)
4835                return;
4836
4837        pr_warn("\n");
4838        pr_warn("==================================\n");
4839        pr_warn("WARNING: Nested lock was not taken\n");
4840        print_kernel_ident();
4841        pr_warn("----------------------------------\n");
4842
4843        pr_warn("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr));
4844        print_lock(hlock);
4845
4846        pr_warn("\nbut this task is not holding:\n");
4847        pr_warn("%s\n", hlock->nest_lock->name);
4848
4849        pr_warn("\nstack backtrace:\n");
4850        dump_stack();
4851
4852        pr_warn("\nother info that might help us debug this:\n");
4853        lockdep_print_held_locks(curr);
4854
4855        pr_warn("\nstack backtrace:\n");
4856        dump_stack();
4857}
4858
4859static int __lock_is_held(const struct lockdep_map *lock, int read);
4860
4861/*
4862 * This gets called for every mutex_lock*()/spin_lock*() operation.
4863 * We maintain the dependency maps and