linux/kernel/lockdep.c
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   1/*
   2 * kernel/lockdep.c
   3 *
   4 * Runtime locking correctness validator
   5 *
   6 * Started by Ingo Molnar:
   7 *
   8 *  Copyright (C) 2006,2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
   9 *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
  10 *
  11 * this code maps all the lock dependencies as they occur in a live kernel
  12 * and will warn about the following classes of locking bugs:
  13 *
  14 * - lock inversion scenarios
  15 * - circular lock dependencies
  16 * - hardirq/softirq safe/unsafe locking bugs
  17 *
  18 * Bugs are reported even if the current locking scenario does not cause
  19 * any deadlock at this point.
  20 *
  21 * I.e. if anytime in the past two locks were taken in a different order,
  22 * even if it happened for another task, even if those were different
  23 * locks (but of the same class as this lock), this code will detect it.
  24 *
  25 * Thanks to Arjan van de Ven for coming up with the initial idea of
  26 * mapping lock dependencies runtime.
  27 */
  28#define DISABLE_BRANCH_PROFILING
  29#include <linux/mutex.h>
  30#include <linux/sched.h>
  31#include <linux/delay.h>
  32#include <linux/module.h>
  33#include <linux/proc_fs.h>
  34#include <linux/seq_file.h>
  35#include <linux/spinlock.h>
  36#include <linux/kallsyms.h>
  37#include <linux/interrupt.h>
  38#include <linux/stacktrace.h>
  39#include <linux/debug_locks.h>
  40#include <linux/irqflags.h>
  41#include <linux/utsname.h>
  42#include <linux/hash.h>
  43#include <linux/ftrace.h>
  44#include <linux/stringify.h>
  45#include <trace/lockdep.h>
  46
  47#include <asm/sections.h>
  48
  49#include "lockdep_internals.h"
  50
  51#ifdef CONFIG_PROVE_LOCKING
  52int prove_locking = 1;
  53module_param(prove_locking, int, 0644);
  54#else
  55#define prove_locking 0
  56#endif
  57
  58#ifdef CONFIG_LOCK_STAT
  59int lock_stat = 1;
  60module_param(lock_stat, int, 0644);
  61#else
  62#define lock_stat 0
  63#endif
  64
  65/*
  66 * lockdep_lock: protects the lockdep graph, the hashes and the
  67 *               class/list/hash allocators.
  68 *
  69 * This is one of the rare exceptions where it's justified
  70 * to use a raw spinlock - we really dont want the spinlock
  71 * code to recurse back into the lockdep code...
  72 */
  73static raw_spinlock_t lockdep_lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
  74
  75static int graph_lock(void)
  76{
  77        __raw_spin_lock(&lockdep_lock);
  78        /*
  79         * Make sure that if another CPU detected a bug while
  80         * walking the graph we dont change it (while the other
  81         * CPU is busy printing out stuff with the graph lock
  82         * dropped already)
  83         */
  84        if (!debug_locks) {
  85                __raw_spin_unlock(&lockdep_lock);
  86                return 0;
  87        }
  88        /* prevent any recursions within lockdep from causing deadlocks */
  89        current->lockdep_recursion++;
  90        return 1;
  91}
  92
  93static inline int graph_unlock(void)
  94{
  95        if (debug_locks && !__raw_spin_is_locked(&lockdep_lock))
  96                return DEBUG_LOCKS_WARN_ON(1);
  97
  98        current->lockdep_recursion--;
  99        __raw_spin_unlock(&lockdep_lock);
 100        return 0;
 101}
 102
 103/*
 104 * Turn lock debugging off and return with 0 if it was off already,
 105 * and also release the graph lock:
 106 */
 107static inline int debug_locks_off_graph_unlock(void)
 108{
 109        int ret = debug_locks_off();
 110
 111        __raw_spin_unlock(&lockdep_lock);
 112
 113        return ret;
 114}
 115
 116static int lockdep_initialized;
 117
 118unsigned long nr_list_entries;
 119static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES];
 120
 121/*
 122 * All data structures here are protected by the global debug_lock.
 123 *
 124 * Mutex key structs only get allocated, once during bootup, and never
 125 * get freed - this significantly simplifies the debugging code.
 126 */
 127unsigned long nr_lock_classes;
 128static struct lock_class lock_classes[MAX_LOCKDEP_KEYS];
 129
 130static inline struct lock_class *hlock_class(struct held_lock *hlock)
 131{
 132        if (!hlock->class_idx) {
 133                DEBUG_LOCKS_WARN_ON(1);
 134                return NULL;
 135        }
 136        return lock_classes + hlock->class_idx - 1;
 137}
 138
 139#ifdef CONFIG_LOCK_STAT
 140static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS], lock_stats);
 141
 142static int lock_point(unsigned long points[], unsigned long ip)
 143{
 144        int i;
 145
 146        for (i = 0; i < LOCKSTAT_POINTS; i++) {
 147                if (points[i] == 0) {
 148                        points[i] = ip;
 149                        break;
 150                }
 151                if (points[i] == ip)
 152                        break;
 153        }
 154
 155        return i;
 156}
 157
 158static void lock_time_inc(struct lock_time *lt, s64 time)
 159{
 160        if (time > lt->max)
 161                lt->max = time;
 162
 163        if (time < lt->min || !lt->min)
 164                lt->min = time;
 165
 166        lt->total += time;
 167        lt->nr++;
 168}
 169
 170static inline void lock_time_add(struct lock_time *src, struct lock_time *dst)
 171{
 172        dst->min += src->min;
 173        dst->max += src->max;
 174        dst->total += src->total;
 175        dst->nr += src->nr;
 176}
 177
 178struct lock_class_stats lock_stats(struct lock_class *class)
 179{
 180        struct lock_class_stats stats;
 181        int cpu, i;
 182
 183        memset(&stats, 0, sizeof(struct lock_class_stats));
 184        for_each_possible_cpu(cpu) {
 185                struct lock_class_stats *pcs =
 186                        &per_cpu(lock_stats, cpu)[class - lock_classes];
 187
 188                for (i = 0; i < ARRAY_SIZE(stats.contention_point); i++)
 189                        stats.contention_point[i] += pcs->contention_point[i];
 190
 191                for (i = 0; i < ARRAY_SIZE(stats.contending_point); i++)
 192                        stats.contending_point[i] += pcs->contending_point[i];
 193
 194                lock_time_add(&pcs->read_waittime, &stats.read_waittime);
 195                lock_time_add(&pcs->write_waittime, &stats.write_waittime);
 196
 197                lock_time_add(&pcs->read_holdtime, &stats.read_holdtime);
 198                lock_time_add(&pcs->write_holdtime, &stats.write_holdtime);
 199
 200                for (i = 0; i < ARRAY_SIZE(stats.bounces); i++)
 201                        stats.bounces[i] += pcs->bounces[i];
 202        }
 203
 204        return stats;
 205}
 206
 207void clear_lock_stats(struct lock_class *class)
 208{
 209        int cpu;
 210
 211        for_each_possible_cpu(cpu) {
 212                struct lock_class_stats *cpu_stats =
 213                        &per_cpu(lock_stats, cpu)[class - lock_classes];
 214
 215                memset(cpu_stats, 0, sizeof(struct lock_class_stats));
 216        }
 217        memset(class->contention_point, 0, sizeof(class->contention_point));
 218        memset(class->contending_point, 0, sizeof(class->contending_point));
 219}
 220
 221static struct lock_class_stats *get_lock_stats(struct lock_class *class)
 222{
 223        return &get_cpu_var(lock_stats)[class - lock_classes];
 224}
 225
 226static void put_lock_stats(struct lock_class_stats *stats)
 227{
 228        put_cpu_var(lock_stats);
 229}
 230
 231static void lock_release_holdtime(struct held_lock *hlock)
 232{
 233        struct lock_class_stats *stats;
 234        s64 holdtime;
 235
 236        if (!lock_stat)
 237                return;
 238
 239        holdtime = sched_clock() - hlock->holdtime_stamp;
 240
 241        stats = get_lock_stats(hlock_class(hlock));
 242        if (hlock->read)
 243                lock_time_inc(&stats->read_holdtime, holdtime);
 244        else
 245                lock_time_inc(&stats->write_holdtime, holdtime);
 246        put_lock_stats(stats);
 247}
 248#else
 249static inline void lock_release_holdtime(struct held_lock *hlock)
 250{
 251}
 252#endif
 253
 254/*
 255 * We keep a global list of all lock classes. The list only grows,
 256 * never shrinks. The list is only accessed with the lockdep
 257 * spinlock lock held.
 258 */
 259LIST_HEAD(all_lock_classes);
 260
 261/*
 262 * The lockdep classes are in a hash-table as well, for fast lookup:
 263 */
 264#define CLASSHASH_BITS          (MAX_LOCKDEP_KEYS_BITS - 1)
 265#define CLASSHASH_SIZE          (1UL << CLASSHASH_BITS)
 266#define __classhashfn(key)      hash_long((unsigned long)key, CLASSHASH_BITS)
 267#define classhashentry(key)     (classhash_table + __classhashfn((key)))
 268
 269static struct list_head classhash_table[CLASSHASH_SIZE];
 270
 271/*
 272 * We put the lock dependency chains into a hash-table as well, to cache
 273 * their existence:
 274 */
 275#define CHAINHASH_BITS          (MAX_LOCKDEP_CHAINS_BITS-1)
 276#define CHAINHASH_SIZE          (1UL << CHAINHASH_BITS)
 277#define __chainhashfn(chain)    hash_long(chain, CHAINHASH_BITS)
 278#define chainhashentry(chain)   (chainhash_table + __chainhashfn((chain)))
 279
 280static struct list_head chainhash_table[CHAINHASH_SIZE];
 281
 282/*
 283 * The hash key of the lock dependency chains is a hash itself too:
 284 * it's a hash of all locks taken up to that lock, including that lock.
 285 * It's a 64-bit hash, because it's important for the keys to be
 286 * unique.
 287 */
 288#define iterate_chain_key(key1, key2) \
 289        (((key1) << MAX_LOCKDEP_KEYS_BITS) ^ \
 290        ((key1) >> (64-MAX_LOCKDEP_KEYS_BITS)) ^ \
 291        (key2))
 292
 293void lockdep_off(void)
 294{
 295        current->lockdep_recursion++;
 296}
 297EXPORT_SYMBOL(lockdep_off);
 298
 299void lockdep_on(void)
 300{
 301        current->lockdep_recursion--;
 302}
 303EXPORT_SYMBOL(lockdep_on);
 304
 305/*
 306 * Debugging switches:
 307 */
 308
 309#define VERBOSE                 0
 310#define VERY_VERBOSE            0
 311
 312#if VERBOSE
 313# define HARDIRQ_VERBOSE        1
 314# define SOFTIRQ_VERBOSE        1
 315# define RECLAIM_VERBOSE        1
 316#else
 317# define HARDIRQ_VERBOSE        0
 318# define SOFTIRQ_VERBOSE        0
 319# define RECLAIM_VERBOSE        0
 320#endif
 321
 322#if VERBOSE || HARDIRQ_VERBOSE || SOFTIRQ_VERBOSE || RECLAIM_VERBOSE
 323/*
 324 * Quick filtering for interesting events:
 325 */
 326static int class_filter(struct lock_class *class)
 327{
 328#if 0
 329        /* Example */
 330        if (class->name_version == 1 &&
 331                        !strcmp(class->name, "lockname"))
 332                return 1;
 333        if (class->name_version == 1 &&
 334                        !strcmp(class->name, "&struct->lockfield"))
 335                return 1;
 336#endif
 337        /* Filter everything else. 1 would be to allow everything else */
 338        return 0;
 339}
 340#endif
 341
 342static int verbose(struct lock_class *class)
 343{
 344#if VERBOSE
 345        return class_filter(class);
 346#endif
 347        return 0;
 348}
 349
 350/*
 351 * Stack-trace: tightly packed array of stack backtrace
 352 * addresses. Protected by the graph_lock.
 353 */
 354unsigned long nr_stack_trace_entries;
 355static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];
 356
 357static int save_trace(struct stack_trace *trace)
 358{
 359        trace->nr_entries = 0;
 360        trace->max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries;
 361        trace->entries = stack_trace + nr_stack_trace_entries;
 362
 363        trace->skip = 3;
 364
 365        save_stack_trace(trace);
 366
 367        trace->max_entries = trace->nr_entries;
 368
 369        nr_stack_trace_entries += trace->nr_entries;
 370
 371        if (nr_stack_trace_entries == MAX_STACK_TRACE_ENTRIES) {
 372                if (!debug_locks_off_graph_unlock())
 373                        return 0;
 374
 375                printk("BUG: MAX_STACK_TRACE_ENTRIES too low!\n");
 376                printk("turning off the locking correctness validator.\n");
 377                dump_stack();
 378
 379                return 0;
 380        }
 381
 382        return 1;
 383}
 384
 385unsigned int nr_hardirq_chains;
 386unsigned int nr_softirq_chains;
 387unsigned int nr_process_chains;
 388unsigned int max_lockdep_depth;
 389unsigned int max_recursion_depth;
 390
 391static unsigned int lockdep_dependency_gen_id;
 392
 393static bool lockdep_dependency_visit(struct lock_class *source,
 394                                     unsigned int depth)
 395{
 396        if (!depth)
 397                lockdep_dependency_gen_id++;
 398        if (source->dep_gen_id == lockdep_dependency_gen_id)
 399                return true;
 400        source->dep_gen_id = lockdep_dependency_gen_id;
 401        return false;
 402}
 403
 404#ifdef CONFIG_DEBUG_LOCKDEP
 405/*
 406 * We cannot printk in early bootup code. Not even early_printk()
 407 * might work. So we mark any initialization errors and printk
 408 * about it later on, in lockdep_info().
 409 */
 410static int lockdep_init_error;
 411static unsigned long lockdep_init_trace_data[20];
 412static struct stack_trace lockdep_init_trace = {
 413        .max_entries = ARRAY_SIZE(lockdep_init_trace_data),
 414        .entries = lockdep_init_trace_data,
 415};
 416
 417/*
 418 * Various lockdep statistics:
 419 */
 420atomic_t chain_lookup_hits;
 421atomic_t chain_lookup_misses;
 422atomic_t hardirqs_on_events;
 423atomic_t hardirqs_off_events;
 424atomic_t redundant_hardirqs_on;
 425atomic_t redundant_hardirqs_off;
 426atomic_t softirqs_on_events;
 427atomic_t softirqs_off_events;
 428atomic_t redundant_softirqs_on;
 429atomic_t redundant_softirqs_off;
 430atomic_t nr_unused_locks;
 431atomic_t nr_cyclic_checks;
 432atomic_t nr_cyclic_check_recursions;
 433atomic_t nr_find_usage_forwards_checks;
 434atomic_t nr_find_usage_forwards_recursions;
 435atomic_t nr_find_usage_backwards_checks;
 436atomic_t nr_find_usage_backwards_recursions;
 437#endif
 438
 439/*
 440 * Locking printouts:
 441 */
 442
 443#define __USAGE(__STATE)                                                \
 444        [LOCK_USED_IN_##__STATE] = "IN-"__stringify(__STATE)"-W",       \
 445        [LOCK_ENABLED_##__STATE] = __stringify(__STATE)"-ON-W",         \
 446        [LOCK_USED_IN_##__STATE##_READ] = "IN-"__stringify(__STATE)"-R",\
 447        [LOCK_ENABLED_##__STATE##_READ] = __stringify(__STATE)"-ON-R",
 448
 449static const char *usage_str[] =
 450{
 451#define LOCKDEP_STATE(__STATE) __USAGE(__STATE)
 452#include "lockdep_states.h"
 453#undef LOCKDEP_STATE
 454        [LOCK_USED] = "INITIAL USE",
 455};
 456
 457const char * __get_key_name(struct lockdep_subclass_key *key, char *str)
 458{
 459        return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str);
 460}
 461
 462static inline unsigned long lock_flag(enum lock_usage_bit bit)
 463{
 464        return 1UL << bit;
 465}
 466
 467static char get_usage_char(struct lock_class *class, enum lock_usage_bit bit)
 468{
 469        char c = '.';
 470
 471        if (class->usage_mask & lock_flag(bit + 2))
 472                c = '+';
 473        if (class->usage_mask & lock_flag(bit)) {
 474                c = '-';
 475                if (class->usage_mask & lock_flag(bit + 2))
 476                        c = '?';
 477        }
 478
 479        return c;
 480}
 481
 482void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS])
 483{
 484        int i = 0;
 485
 486#define LOCKDEP_STATE(__STATE)                                          \
 487        usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE);     \
 488        usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE##_READ);
 489#include "lockdep_states.h"
 490#undef LOCKDEP_STATE
 491
 492        usage[i] = '\0';
 493}
 494
 495static void print_lock_name(struct lock_class *class)
 496{
 497        char str[KSYM_NAME_LEN], usage[LOCK_USAGE_CHARS];
 498        const char *name;
 499
 500        get_usage_chars(class, usage);
 501
 502        name = class->name;
 503        if (!name) {
 504                name = __get_key_name(class->key, str);
 505                printk(" (%s", name);
 506        } else {
 507                printk(" (%s", name);
 508                if (class->name_version > 1)
 509                        printk("#%d", class->name_version);
 510                if (class->subclass)
 511                        printk("/%d", class->subclass);
 512        }
 513        printk("){%s}", usage);
 514}
 515
 516static void print_lockdep_cache(struct lockdep_map *lock)
 517{
 518        const char *name;
 519        char str[KSYM_NAME_LEN];
 520
 521        name = lock->name;
 522        if (!name)
 523                name = __get_key_name(lock->key->subkeys, str);
 524
 525        printk("%s", name);
 526}
 527
 528static void print_lock(struct held_lock *hlock)
 529{
 530        print_lock_name(hlock_class(hlock));
 531        printk(", at: ");
 532        print_ip_sym(hlock->acquire_ip);
 533}
 534
 535static void lockdep_print_held_locks(struct task_struct *curr)
 536{
 537        int i, depth = curr->lockdep_depth;
 538
 539        if (!depth) {
 540                printk("no locks held by %s/%d.\n", curr->comm, task_pid_nr(curr));
 541                return;
 542        }
 543        printk("%d lock%s held by %s/%d:\n",
 544                depth, depth > 1 ? "s" : "", curr->comm, task_pid_nr(curr));
 545
 546        for (i = 0; i < depth; i++) {
 547                printk(" #%d: ", i);
 548                print_lock(curr->held_locks + i);
 549        }
 550}
 551
 552static void print_lock_class_header(struct lock_class *class, int depth)
 553{
 554        int bit;
 555
 556        printk("%*s->", depth, "");
 557        print_lock_name(class);
 558        printk(" ops: %lu", class->ops);
 559        printk(" {\n");
 560
 561        for (bit = 0; bit < LOCK_USAGE_STATES; bit++) {
 562                if (class->usage_mask & (1 << bit)) {
 563                        int len = depth;
 564
 565                        len += printk("%*s   %s", depth, "", usage_str[bit]);
 566                        len += printk(" at:\n");
 567                        print_stack_trace(class->usage_traces + bit, len);
 568                }
 569        }
 570        printk("%*s }\n", depth, "");
 571
 572        printk("%*s ... key      at: ",depth,"");
 573        print_ip_sym((unsigned long)class->key);
 574}
 575
 576/*
 577 * printk all lock dependencies starting at <entry>:
 578 */
 579static void __used
 580print_lock_dependencies(struct lock_class *class, int depth)
 581{
 582        struct lock_list *entry;
 583
 584        if (lockdep_dependency_visit(class, depth))
 585                return;
 586
 587        if (DEBUG_LOCKS_WARN_ON(depth >= 20))
 588                return;
 589
 590        print_lock_class_header(class, depth);
 591
 592        list_for_each_entry(entry, &class->locks_after, entry) {
 593                if (DEBUG_LOCKS_WARN_ON(!entry->class))
 594                        return;
 595
 596                print_lock_dependencies(entry->class, depth + 1);
 597
 598                printk("%*s ... acquired at:\n",depth,"");
 599                print_stack_trace(&entry->trace, 2);
 600                printk("\n");
 601        }
 602}
 603
 604static void print_kernel_version(void)
 605{
 606        printk("%s %.*s\n", init_utsname()->release,
 607                (int)strcspn(init_utsname()->version, " "),
 608                init_utsname()->version);
 609}
 610
 611static int very_verbose(struct lock_class *class)
 612{
 613#if VERY_VERBOSE
 614        return class_filter(class);
 615#endif
 616        return 0;
 617}
 618
 619/*
 620 * Is this the address of a static object:
 621 */
 622static int static_obj(void *obj)
 623{
 624        unsigned long start = (unsigned long) &_stext,
 625                      end   = (unsigned long) &_end,
 626                      addr  = (unsigned long) obj;
 627#ifdef CONFIG_SMP
 628        int i;
 629#endif
 630
 631        /*
 632         * static variable?
 633         */
 634        if ((addr >= start) && (addr < end))
 635                return 1;
 636
 637#ifdef CONFIG_SMP
 638        /*
 639         * percpu var?
 640         */
 641        for_each_possible_cpu(i) {
 642                start = (unsigned long) &__per_cpu_start + per_cpu_offset(i);
 643                end   = (unsigned long) &__per_cpu_start + PERCPU_ENOUGH_ROOM
 644                                        + per_cpu_offset(i);
 645
 646                if ((addr >= start) && (addr < end))
 647                        return 1;
 648        }
 649#endif
 650
 651        /*
 652         * module var?
 653         */
 654        return is_module_address(addr);
 655}
 656
 657/*
 658 * To make lock name printouts unique, we calculate a unique
 659 * class->name_version generation counter:
 660 */
 661static int count_matching_names(struct lock_class *new_class)
 662{
 663        struct lock_class *class;
 664        int count = 0;
 665
 666        if (!new_class->name)
 667                return 0;
 668
 669        list_for_each_entry(class, &all_lock_classes, lock_entry) {
 670                if (new_class->key - new_class->subclass == class->key)
 671                        return class->name_version;
 672                if (class->name && !strcmp(class->name, new_class->name))
 673                        count = max(count, class->name_version);
 674        }
 675
 676        return count + 1;
 677}
 678
 679/*
 680 * Register a lock's class in the hash-table, if the class is not present
 681 * yet. Otherwise we look it up. We cache the result in the lock object
 682 * itself, so actual lookup of the hash should be once per lock object.
 683 */
 684static inline struct lock_class *
 685look_up_lock_class(struct lockdep_map *lock, unsigned int subclass)
 686{
 687        struct lockdep_subclass_key *key;
 688        struct list_head *hash_head;
 689        struct lock_class *class;
 690
 691#ifdef CONFIG_DEBUG_LOCKDEP
 692        /*
 693         * If the architecture calls into lockdep before initializing
 694         * the hashes then we'll warn about it later. (we cannot printk
 695         * right now)
 696         */
 697        if (unlikely(!lockdep_initialized)) {
 698                lockdep_init();
 699                lockdep_init_error = 1;
 700                save_stack_trace(&lockdep_init_trace);
 701        }
 702#endif
 703
 704        /*
 705         * Static locks do not have their class-keys yet - for them the key
 706         * is the lock object itself:
 707         */
 708        if (unlikely(!lock->key))
 709                lock->key = (void *)lock;
 710
 711        /*
 712         * NOTE: the class-key must be unique. For dynamic locks, a static
 713         * lock_class_key variable is passed in through the mutex_init()
 714         * (or spin_lock_init()) call - which acts as the key. For static
 715         * locks we use the lock object itself as the key.
 716         */
 717        BUILD_BUG_ON(sizeof(struct lock_class_key) >
 718                        sizeof(struct lockdep_map));
 719
 720        key = lock->key->subkeys + subclass;
 721
 722        hash_head = classhashentry(key);
 723
 724        /*
 725         * We can walk the hash lockfree, because the hash only
 726         * grows, and we are careful when adding entries to the end:
 727         */
 728        list_for_each_entry(class, hash_head, hash_entry) {
 729                if (class->key == key) {
 730                        WARN_ON_ONCE(class->name != lock->name);
 731                        return class;
 732                }
 733        }
 734
 735        return NULL;
 736}
 737
 738/*
 739 * Register a lock's class in the hash-table, if the class is not present
 740 * yet. Otherwise we look it up. We cache the result in the lock object
 741 * itself, so actual lookup of the hash should be once per lock object.
 742 */
 743static inline struct lock_class *
 744register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
 745{
 746        struct lockdep_subclass_key *key;
 747        struct list_head *hash_head;
 748        struct lock_class *class;
 749        unsigned long flags;
 750
 751        class = look_up_lock_class(lock, subclass);
 752        if (likely(class))
 753                return class;
 754
 755        /*
 756         * Debug-check: all keys must be persistent!
 757         */
 758        if (!static_obj(lock->key)) {
 759                debug_locks_off();
 760                printk("INFO: trying to register non-static key.\n");
 761                printk("the code is fine but needs lockdep annotation.\n");
 762                printk("turning off the locking correctness validator.\n");
 763                dump_stack();
 764
 765                return NULL;
 766        }
 767
 768        key = lock->key->subkeys + subclass;
 769        hash_head = classhashentry(key);
 770
 771        raw_local_irq_save(flags);
 772        if (!graph_lock()) {
 773                raw_local_irq_restore(flags);
 774                return NULL;
 775        }
 776        /*
 777         * We have to do the hash-walk again, to avoid races
 778         * with another CPU:
 779         */
 780        list_for_each_entry(class, hash_head, hash_entry)
 781                if (class->key == key)
 782                        goto out_unlock_set;
 783        /*
 784         * Allocate a new key from the static array, and add it to
 785         * the hash:
 786         */
 787        if (nr_lock_classes >= MAX_LOCKDEP_KEYS) {
 788                if (!debug_locks_off_graph_unlock()) {
 789                        raw_local_irq_restore(flags);
 790                        return NULL;
 791                }
 792                raw_local_irq_restore(flags);
 793
 794                printk("BUG: MAX_LOCKDEP_KEYS too low!\n");
 795                printk("turning off the locking correctness validator.\n");
 796                dump_stack();
 797                return NULL;
 798        }
 799        class = lock_classes + nr_lock_classes++;
 800        debug_atomic_inc(&nr_unused_locks);
 801        class->key = key;
 802        class->name = lock->name;
 803        class->subclass = subclass;
 804        INIT_LIST_HEAD(&class->lock_entry);
 805        INIT_LIST_HEAD(&class->locks_before);
 806        INIT_LIST_HEAD(&class->locks_after);
 807        class->name_version = count_matching_names(class);
 808        /*
 809         * We use RCU's safe list-add method to make
 810         * parallel walking of the hash-list safe:
 811         */
 812        list_add_tail_rcu(&class->hash_entry, hash_head);
 813        /*
 814         * Add it to the global list of classes:
 815         */
 816        list_add_tail_rcu(&class->lock_entry, &all_lock_classes);
 817
 818        if (verbose(class)) {
 819                graph_unlock();
 820                raw_local_irq_restore(flags);
 821
 822                printk("\nnew class %p: %s", class->key, class->name);
 823                if (class->name_version > 1)
 824                        printk("#%d", class->name_version);
 825                printk("\n");
 826                dump_stack();
 827
 828                raw_local_irq_save(flags);
 829                if (!graph_lock()) {
 830                        raw_local_irq_restore(flags);
 831                        return NULL;
 832                }
 833        }
 834out_unlock_set:
 835        graph_unlock();
 836        raw_local_irq_restore(flags);
 837
 838        if (!subclass || force)
 839                lock->class_cache = class;
 840
 841        if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))
 842                return NULL;
 843
 844        return class;
 845}
 846
 847#ifdef CONFIG_PROVE_LOCKING
 848/*
 849 * Allocate a lockdep entry. (assumes the graph_lock held, returns
 850 * with NULL on failure)
 851 */
 852static struct lock_list *alloc_list_entry(void)
 853{
 854        if (nr_list_entries >= MAX_LOCKDEP_ENTRIES) {
 855                if (!debug_locks_off_graph_unlock())
 856                        return NULL;
 857
 858                printk("BUG: MAX_LOCKDEP_ENTRIES too low!\n");
 859                printk("turning off the locking correctness validator.\n");
 860                dump_stack();
 861                return NULL;
 862        }
 863        return list_entries + nr_list_entries++;
 864}
 865
 866/*
 867 * Add a new dependency to the head of the list:
 868 */
 869static int add_lock_to_list(struct lock_class *class, struct lock_class *this,
 870                            struct list_head *head, unsigned long ip, int distance)
 871{
 872        struct lock_list *entry;
 873        /*
 874         * Lock not present yet - get a new dependency struct and
 875         * add it to the list:
 876         */
 877        entry = alloc_list_entry();
 878        if (!entry)
 879                return 0;
 880
 881        if (!save_trace(&entry->trace))
 882                return 0;
 883
 884        entry->class = this;
 885        entry->distance = distance;
 886        /*
 887         * Since we never remove from the dependency list, the list can
 888         * be walked lockless by other CPUs, it's only allocation
 889         * that must be protected by the spinlock. But this also means
 890         * we must make new entries visible only once writes to the
 891         * entry become visible - hence the RCU op:
 892         */
 893        list_add_tail_rcu(&entry->entry, head);
 894
 895        return 1;
 896}
 897
 898/*
 899 * Recursive, forwards-direction lock-dependency checking, used for
 900 * both noncyclic checking and for hardirq-unsafe/softirq-unsafe
 901 * checking.
 902 *
 903 * (to keep the stackframe of the recursive functions small we
 904 *  use these global variables, and we also mark various helper
 905 *  functions as noinline.)
 906 */
 907static struct held_lock *check_source, *check_target;
 908
 909/*
 910 * Print a dependency chain entry (this is only done when a deadlock
 911 * has been detected):
 912 */
 913static noinline int
 914print_circular_bug_entry(struct lock_list *target, unsigned int depth)
 915{
 916        if (debug_locks_silent)
 917                return 0;
 918        printk("\n-> #%u", depth);
 919        print_lock_name(target->class);
 920        printk(":\n");
 921        print_stack_trace(&target->trace, 6);
 922
 923        return 0;
 924}
 925
 926/*
 927 * When a circular dependency is detected, print the
 928 * header first:
 929 */
 930static noinline int
 931print_circular_bug_header(struct lock_list *entry, unsigned int depth)
 932{
 933        struct task_struct *curr = current;
 934
 935        if (!debug_locks_off_graph_unlock() || debug_locks_silent)
 936                return 0;
 937
 938        printk("\n=======================================================\n");
 939        printk(  "[ INFO: possible circular locking dependency detected ]\n");
 940        print_kernel_version();
 941        printk(  "-------------------------------------------------------\n");
 942        printk("%s/%d is trying to acquire lock:\n",
 943                curr->comm, task_pid_nr(curr));
 944        print_lock(check_source);
 945        printk("\nbut task is already holding lock:\n");
 946        print_lock(check_target);
 947        printk("\nwhich lock already depends on the new lock.\n\n");
 948        printk("\nthe existing dependency chain (in reverse order) is:\n");
 949
 950        print_circular_bug_entry(entry, depth);
 951
 952        return 0;
 953}
 954
 955static noinline int print_circular_bug_tail(void)
 956{
 957        struct task_struct *curr = current;
 958        struct lock_list this;
 959
 960        if (debug_locks_silent)
 961                return 0;
 962
 963        this.class = hlock_class(check_source);
 964        if (!save_trace(&this.trace))
 965                return 0;
 966
 967        print_circular_bug_entry(&this, 0);
 968
 969        printk("\nother info that might help us debug this:\n\n");
 970        lockdep_print_held_locks(curr);
 971
 972        printk("\nstack backtrace:\n");
 973        dump_stack();
 974
 975        return 0;
 976}
 977
 978#define RECURSION_LIMIT 40
 979
 980static int noinline print_infinite_recursion_bug(void)
 981{
 982        if (!debug_locks_off_graph_unlock())
 983                return 0;
 984
 985        WARN_ON(1);
 986
 987        return 0;
 988}
 989
 990unsigned long __lockdep_count_forward_deps(struct lock_class *class,
 991                                           unsigned int depth)
 992{
 993        struct lock_list *entry;
 994        unsigned long ret = 1;
 995
 996        if (lockdep_dependency_visit(class, depth))
 997                return 0;
 998
 999        /*
1000         * Recurse this class's dependency list:
1001         */
1002        list_for_each_entry(entry, &class->locks_after, entry)
1003                ret += __lockdep_count_forward_deps(entry->class, depth + 1);
1004
1005        return ret;
1006}
1007
1008unsigned long lockdep_count_forward_deps(struct lock_class *class)
1009{
1010        unsigned long ret, flags;
1011
1012        local_irq_save(flags);
1013        __raw_spin_lock(&lockdep_lock);
1014        ret = __lockdep_count_forward_deps(class, 0);
1015        __raw_spin_unlock(&lockdep_lock);
1016        local_irq_restore(flags);
1017
1018        return ret;
1019}
1020
1021unsigned long __lockdep_count_backward_deps(struct lock_class *class,
1022                                            unsigned int depth)
1023{
1024        struct lock_list *entry;
1025        unsigned long ret = 1;
1026
1027        if (lockdep_dependency_visit(class, depth))
1028                return 0;
1029        /*
1030         * Recurse this class's dependency list:
1031         */
1032        list_for_each_entry(entry, &class->locks_before, entry)
1033                ret += __lockdep_count_backward_deps(entry->class, depth + 1);
1034
1035        return ret;
1036}
1037
1038unsigned long lockdep_count_backward_deps(struct lock_class *class)
1039{
1040        unsigned long ret, flags;
1041
1042        local_irq_save(flags);
1043        __raw_spin_lock(&lockdep_lock);
1044        ret = __lockdep_count_backward_deps(class, 0);
1045        __raw_spin_unlock(&lockdep_lock);
1046        local_irq_restore(flags);
1047
1048        return ret;
1049}
1050
1051/*
1052 * Prove that the dependency graph starting at <entry> can not
1053 * lead to <target>. Print an error and return 0 if it does.
1054 */
1055static noinline int
1056check_noncircular(struct lock_class *source, unsigned int depth)
1057{
1058        struct lock_list *entry;
1059
1060        if (lockdep_dependency_visit(source, depth))
1061                return 1;
1062
1063        debug_atomic_inc(&nr_cyclic_check_recursions);
1064        if (depth > max_recursion_depth)
1065                max_recursion_depth = depth;
1066        if (depth >= RECURSION_LIMIT)
1067                return print_infinite_recursion_bug();
1068        /*
1069         * Check this lock's dependency list:
1070         */
1071        list_for_each_entry(entry, &source->locks_after, entry) {
1072                if (entry->class == hlock_class(check_target))
1073                        return print_circular_bug_header(entry, depth+1);
1074                debug_atomic_inc(&nr_cyclic_checks);
1075                if (!check_noncircular(entry->class, depth+1))
1076                        return print_circular_bug_entry(entry, depth+1);
1077        }
1078        return 1;
1079}
1080
1081#if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
1082/*
1083 * Forwards and backwards subgraph searching, for the purposes of
1084 * proving that two subgraphs can be connected by a new dependency
1085 * without creating any illegal irq-safe -> irq-unsafe lock dependency.
1086 */
1087static enum lock_usage_bit find_usage_bit;
1088static struct lock_class *forwards_match, *backwards_match;
1089
1090/*
1091 * Find a node in the forwards-direction dependency sub-graph starting
1092 * at <source> that matches <find_usage_bit>.
1093 *
1094 * Return 2 if such a node exists in the subgraph, and put that node
1095 * into <forwards_match>.
1096 *
1097 * Return 1 otherwise and keep <forwards_match> unchanged.
1098 * Return 0 on error.
1099 */
1100static noinline int
1101find_usage_forwards(struct lock_class *source, unsigned int depth)
1102{
1103        struct lock_list *entry;
1104        int ret;
1105
1106        if (lockdep_dependency_visit(source, depth))
1107                return 1;
1108
1109        if (depth > max_recursion_depth)
1110                max_recursion_depth = depth;
1111        if (depth >= RECURSION_LIMIT)
1112                return print_infinite_recursion_bug();
1113
1114        debug_atomic_inc(&nr_find_usage_forwards_checks);
1115        if (source->usage_mask & (1 << find_usage_bit)) {
1116                forwards_match = source;
1117                return 2;
1118        }
1119
1120        /*
1121         * Check this lock's dependency list:
1122         */
1123        list_for_each_entry(entry, &source->locks_after, entry) {
1124                debug_atomic_inc(&nr_find_usage_forwards_recursions);
1125                ret = find_usage_forwards(entry->class, depth+1);
1126                if (ret == 2 || ret == 0)
1127                        return ret;
1128        }
1129        return 1;
1130}
1131
1132/*
1133 * Find a node in the backwards-direction dependency sub-graph starting
1134 * at <source> that matches <find_usage_bit>.
1135 *
1136 * Return 2 if such a node exists in the subgraph, and put that node
1137 * into <backwards_match>.
1138 *
1139 * Return 1 otherwise and keep <backwards_match> unchanged.
1140 * Return 0 on error.
1141 */
1142static noinline int
1143find_usage_backwards(struct lock_class *source, unsigned int depth)
1144{
1145        struct lock_list *entry;
1146        int ret;
1147
1148        if (lockdep_dependency_visit(source, depth))
1149                return 1;
1150
1151        if (!__raw_spin_is_locked(&lockdep_lock))
1152                return DEBUG_LOCKS_WARN_ON(1);
1153
1154        if (depth > max_recursion_depth)
1155                max_recursion_depth = depth;
1156        if (depth >= RECURSION_LIMIT)
1157                return print_infinite_recursion_bug();
1158
1159        debug_atomic_inc(&nr_find_usage_backwards_checks);
1160        if (source->usage_mask & (1 << find_usage_bit)) {
1161                backwards_match = source;
1162                return 2;
1163        }
1164
1165        if (!source && debug_locks_off_graph_unlock()) {
1166                WARN_ON(1);
1167                return 0;
1168        }
1169
1170        /*
1171         * Check this lock's dependency list:
1172         */
1173        list_for_each_entry(entry, &source->locks_before, entry) {
1174                debug_atomic_inc(&nr_find_usage_backwards_recursions);
1175                ret = find_usage_backwards(entry->class, depth+1);
1176                if (ret == 2 || ret == 0)
1177                        return ret;
1178        }
1179        return 1;
1180}
1181
1182static int
1183print_bad_irq_dependency(struct task_struct *curr,
1184                         struct held_lock *prev,
1185                         struct held_lock *next,
1186                         enum lock_usage_bit bit1,
1187                         enum lock_usage_bit bit2,
1188                         const char *irqclass)
1189{
1190        if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1191                return 0;
1192
1193        printk("\n======================================================\n");
1194        printk(  "[ INFO: %s-safe -> %s-unsafe lock order detected ]\n",
1195                irqclass, irqclass);
1196        print_kernel_version();
1197        printk(  "------------------------------------------------------\n");
1198        printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
1199                curr->comm, task_pid_nr(curr),
1200                curr->hardirq_context, hardirq_count() >> HARDIRQ_SHIFT,
1201                curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT,
1202                curr->hardirqs_enabled,
1203                curr->softirqs_enabled);
1204        print_lock(next);
1205
1206        printk("\nand this task is already holding:\n");
1207        print_lock(prev);
1208        printk("which would create a new lock dependency:\n");
1209        print_lock_name(hlock_class(prev));
1210        printk(" ->");
1211        print_lock_name(hlock_class(next));
1212        printk("\n");
1213
1214        printk("\nbut this new dependency connects a %s-irq-safe lock:\n",
1215                irqclass);
1216        print_lock_name(backwards_match);
1217        printk("\n... which became %s-irq-safe at:\n", irqclass);
1218
1219        print_stack_trace(backwards_match->usage_traces + bit1, 1);
1220
1221        printk("\nto a %s-irq-unsafe lock:\n", irqclass);
1222        print_lock_name(forwards_match);
1223        printk("\n... which became %s-irq-unsafe at:\n", irqclass);
1224        printk("...");
1225
1226        print_stack_trace(forwards_match->usage_traces + bit2, 1);
1227
1228        printk("\nother info that might help us debug this:\n\n");
1229        lockdep_print_held_locks(curr);
1230
1231        printk("\nthe %s-irq-safe lock's dependencies:\n", irqclass);
1232        print_lock_dependencies(backwards_match, 0);
1233
1234        printk("\nthe %s-irq-unsafe lock's dependencies:\n", irqclass);
1235        print_lock_dependencies(forwards_match, 0);
1236
1237        printk("\nstack backtrace:\n");
1238        dump_stack();
1239
1240        return 0;
1241}
1242
1243static int
1244check_usage(struct task_struct *curr, struct held_lock *prev,
1245            struct held_lock *next, enum lock_usage_bit bit_backwards,
1246            enum lock_usage_bit bit_forwards, const char *irqclass)
1247{
1248        int ret;
1249
1250        find_usage_bit = bit_backwards;
1251        /* fills in <backwards_match> */
1252        ret = find_usage_backwards(hlock_class(prev), 0);
1253        if (!ret || ret == 1)
1254                return ret;
1255
1256        find_usage_bit = bit_forwards;
1257        ret = find_usage_forwards(hlock_class(next), 0);
1258        if (!ret || ret == 1)
1259                return ret;
1260        /* ret == 2 */
1261        return print_bad_irq_dependency(curr, prev, next,
1262                        bit_backwards, bit_forwards, irqclass);
1263}
1264
1265static const char *state_names[] = {
1266#define LOCKDEP_STATE(__STATE) \
1267        __stringify(__STATE),
1268#include "lockdep_states.h"
1269#undef LOCKDEP_STATE
1270};
1271
1272static const char *state_rnames[] = {
1273#define LOCKDEP_STATE(__STATE) \
1274        __stringify(__STATE)"-READ",
1275#include "lockdep_states.h"
1276#undef LOCKDEP_STATE
1277};
1278
1279static inline const char *state_name(enum lock_usage_bit bit)
1280{
1281        return (bit & 1) ? state_rnames[bit >> 2] : state_names[bit >> 2];
1282}
1283
1284static int exclusive_bit(int new_bit)
1285{
1286        /*
1287         * USED_IN
1288         * USED_IN_READ
1289         * ENABLED
1290         * ENABLED_READ
1291         *
1292         * bit 0 - write/read
1293         * bit 1 - used_in/enabled
1294         * bit 2+  state
1295         */
1296
1297        int state = new_bit & ~3;
1298        int dir = new_bit & 2;
1299
1300        /*
1301         * keep state, bit flip the direction and strip read.
1302         */
1303        return state | (dir ^ 2);
1304}
1305
1306static int check_irq_usage(struct task_struct *curr, struct held_lock *prev,
1307                           struct held_lock *next, enum lock_usage_bit bit)
1308{
1309        /*
1310         * Prove that the new dependency does not connect a hardirq-safe
1311         * lock with a hardirq-unsafe lock - to achieve this we search
1312         * the backwards-subgraph starting at <prev>, and the
1313         * forwards-subgraph starting at <next>:
1314         */
1315        if (!check_usage(curr, prev, next, bit,
1316                           exclusive_bit(bit), state_name(bit)))
1317                return 0;
1318
1319        bit++; /* _READ */
1320
1321        /*
1322         * Prove that the new dependency does not connect a hardirq-safe-read
1323         * lock with a hardirq-unsafe lock - to achieve this we search
1324         * the backwards-subgraph starting at <prev>, and the
1325         * forwards-subgraph starting at <next>:
1326         */
1327        if (!check_usage(curr, prev, next, bit,
1328                           exclusive_bit(bit), state_name(bit)))
1329                return 0;
1330
1331        return 1;
1332}
1333
1334static int
1335check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
1336                struct held_lock *next)
1337{
1338#define LOCKDEP_STATE(__STATE)                                          \
1339        if (!check_irq_usage(curr, prev, next, LOCK_USED_IN_##__STATE)) \
1340                return 0;
1341#include "lockdep_states.h"
1342#undef LOCKDEP_STATE
1343
1344        return 1;
1345}
1346
1347static void inc_chains(void)
1348{
1349        if (current->hardirq_context)
1350                nr_hardirq_chains++;
1351        else {
1352                if (current->softirq_context)
1353                        nr_softirq_chains++;
1354                else
1355                        nr_process_chains++;
1356        }
1357}
1358
1359#else
1360
1361static inline int
1362check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
1363                struct held_lock *next)
1364{
1365        return 1;
1366}
1367
1368static inline void inc_chains(void)
1369{
1370        nr_process_chains++;
1371}
1372
1373#endif
1374
1375static int
1376print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
1377                   struct held_lock *next)
1378{
1379        if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1380                return 0;
1381
1382        printk("\n=============================================\n");
1383        printk(  "[ INFO: possible recursive locking detected ]\n");
1384        print_kernel_version();
1385        printk(  "---------------------------------------------\n");
1386        printk("%s/%d is trying to acquire lock:\n",
1387                curr->comm, task_pid_nr(curr));
1388        print_lock(next);
1389        printk("\nbut task is already holding lock:\n");
1390        print_lock(prev);
1391
1392        printk("\nother info that might help us debug this:\n");
1393        lockdep_print_held_locks(curr);
1394
1395        printk("\nstack backtrace:\n");
1396        dump_stack();
1397
1398        return 0;
1399}
1400
1401/*
1402 * Check whether we are holding such a class already.
1403 *
1404 * (Note that this has to be done separately, because the graph cannot
1405 * detect such classes of deadlocks.)
1406 *
1407 * Returns: 0 on deadlock detected, 1 on OK, 2 on recursive read
1408 */
1409static int
1410check_deadlock(struct task_struct *curr, struct held_lock *next,
1411               struct lockdep_map *next_instance, int read)
1412{
1413        struct held_lock *prev;
1414        struct held_lock *nest = NULL;
1415        int i;
1416
1417        for (i = 0; i < curr->lockdep_depth; i++) {
1418                prev = curr->held_locks + i;
1419
1420                if (prev->instance == next->nest_lock)
1421                        nest = prev;
1422
1423                if (hlock_class(prev) != hlock_class(next))
1424                        continue;
1425
1426                /*
1427                 * Allow read-after-read recursion of the same
1428                 * lock class (i.e. read_lock(lock)+read_lock(lock)):
1429                 */
1430                if ((read == 2) && prev->read)
1431                        return 2;
1432
1433                /*
1434                 * We're holding the nest_lock, which serializes this lock's
1435                 * nesting behaviour.
1436                 */
1437                if (nest)
1438                        return 2;
1439
1440                return print_deadlock_bug(curr, prev, next);
1441        }
1442        return 1;
1443}
1444
1445/*
1446 * There was a chain-cache miss, and we are about to add a new dependency
1447 * to a previous lock. We recursively validate the following rules:
1448 *
1449 *  - would the adding of the <prev> -> <next> dependency create a
1450 *    circular dependency in the graph? [== circular deadlock]
1451 *
1452 *  - does the new prev->next dependency connect any hardirq-safe lock
1453 *    (in the full backwards-subgraph starting at <prev>) with any
1454 *    hardirq-unsafe lock (in the full forwards-subgraph starting at
1455 *    <next>)? [== illegal lock inversion with hardirq contexts]
1456 *
1457 *  - does the new prev->next dependency connect any softirq-safe lock
1458 *    (in the full backwards-subgraph starting at <prev>) with any
1459 *    softirq-unsafe lock (in the full forwards-subgraph starting at
1460 *    <next>)? [== illegal lock inversion with softirq contexts]
1461 *
1462 * any of these scenarios could lead to a deadlock.
1463 *
1464 * Then if all the validations pass, we add the forwards and backwards
1465 * dependency.
1466 */
1467static int
1468check_prev_add(struct task_struct *curr, struct held_lock *prev,
1469               struct held_lock *next, int distance)
1470{
1471        struct lock_list *entry;
1472        int ret;
1473
1474        /*
1475         * Prove that the new <prev> -> <next> dependency would not
1476         * create a circular dependency in the graph. (We do this by
1477         * forward-recursing into the graph starting at <next>, and
1478         * checking whether we can reach <prev>.)
1479         *
1480         * We are using global variables to control the recursion, to
1481         * keep the stackframe size of the recursive functions low:
1482         */
1483        check_source = next;
1484        check_target = prev;
1485        if (!(check_noncircular(hlock_class(next), 0)))
1486                return print_circular_bug_tail();
1487
1488        if (!check_prev_add_irq(curr, prev, next))
1489                return 0;
1490
1491        /*
1492         * For recursive read-locks we do all the dependency checks,
1493         * but we dont store read-triggered dependencies (only
1494         * write-triggered dependencies). This ensures that only the
1495         * write-side dependencies matter, and that if for example a
1496         * write-lock never takes any other locks, then the reads are
1497         * equivalent to a NOP.
1498         */
1499        if (next->read == 2 || prev->read == 2)
1500                return 1;
1501        /*
1502         * Is the <prev> -> <next> dependency already present?
1503         *
1504         * (this may occur even though this is a new chain: consider
1505         *  e.g. the L1 -> L2 -> L3 -> L4 and the L5 -> L1 -> L2 -> L3
1506         *  chains - the second one will be new, but L1 already has
1507         *  L2 added to its dependency list, due to the first chain.)
1508         */
1509        list_for_each_entry(entry, &hlock_class(prev)->locks_after, entry) {
1510                if (entry->class == hlock_class(next)) {
1511                        if (distance == 1)
1512                                entry->distance = 1;
1513                        return 2;
1514                }
1515        }
1516
1517        /*
1518         * Ok, all validations passed, add the new lock
1519         * to the previous lock's dependency list:
1520         */
1521        ret = add_lock_to_list(hlock_class(prev), hlock_class(next),
1522                               &hlock_class(prev)->locks_after,
1523                               next->acquire_ip, distance);
1524
1525        if (!ret)
1526                return 0;
1527
1528        ret = add_lock_to_list(hlock_class(next), hlock_class(prev),
1529                               &hlock_class(next)->locks_before,
1530                               next->acquire_ip, distance);
1531        if (!ret)
1532                return 0;
1533
1534        /*
1535         * Debugging printouts:
1536         */
1537        if (verbose(hlock_class(prev)) || verbose(hlock_class(next))) {
1538                graph_unlock();
1539                printk("\n new dependency: ");
1540                print_lock_name(hlock_class(prev));
1541                printk(" => ");
1542                print_lock_name(hlock_class(next));
1543                printk("\n");
1544                dump_stack();
1545                return graph_lock();
1546        }
1547        return 1;
1548}
1549
1550/*
1551 * Add the dependency to all directly-previous locks that are 'relevant'.
1552 * The ones that are relevant are (in increasing distance from curr):
1553 * all consecutive trylock entries and the final non-trylock entry - or
1554 * the end of this context's lock-chain - whichever comes first.
1555 */
1556static int
1557check_prevs_add(struct task_struct *curr, struct held_lock *next)
1558{
1559        int depth = curr->lockdep_depth;
1560        struct held_lock *hlock;
1561
1562        /*
1563         * Debugging checks.
1564         *
1565         * Depth must not be zero for a non-head lock:
1566         */
1567        if (!depth)
1568                goto out_bug;
1569        /*
1570         * At least two relevant locks must exist for this
1571         * to be a head:
1572         */
1573        if (curr->held_locks[depth].irq_context !=
1574                        curr->held_locks[depth-1].irq_context)
1575                goto out_bug;
1576
1577        for (;;) {
1578                int distance = curr->lockdep_depth - depth + 1;
1579                hlock = curr->held_locks + depth-1;
1580                /*
1581                 * Only non-recursive-read entries get new dependencies
1582                 * added:
1583                 */
1584                if (hlock->read != 2) {
1585                        if (!check_prev_add(curr, hlock, next, distance))
1586                                return 0;
1587                        /*
1588                         * Stop after the first non-trylock entry,
1589                         * as non-trylock entries have added their
1590                         * own direct dependencies already, so this
1591                         * lock is connected to them indirectly:
1592                         */
1593                        if (!hlock->trylock)
1594                                break;
1595                }
1596                depth--;
1597                /*
1598                 * End of lock-stack?
1599                 */
1600                if (!depth)
1601                        break;
1602                /*
1603                 * Stop the search if we cross into another context:
1604                 */
1605                if (curr->held_locks[depth].irq_context !=
1606                                curr->held_locks[depth-1].irq_context)
1607                        break;
1608        }
1609        return 1;
1610out_bug:
1611        if (!debug_locks_off_graph_unlock())
1612                return 0;
1613
1614        WARN_ON(1);
1615
1616        return 0;
1617}
1618
1619unsigned long nr_lock_chains;
1620struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
1621int nr_chain_hlocks;
1622static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
1623
1624struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
1625{
1626        return lock_classes + chain_hlocks[chain->base + i];
1627}
1628
1629/*
1630 * Look up a dependency chain. If the key is not present yet then
1631 * add it and return 1 - in this case the new dependency chain is
1632 * validated. If the key is already hashed, return 0.
1633 * (On return with 1 graph_lock is held.)
1634 */
1635static inline int lookup_chain_cache(struct task_struct *curr,
1636                                     struct held_lock *hlock,
1637                                     u64 chain_key)
1638{
1639        struct lock_class *class = hlock_class(hlock);
1640        struct list_head *hash_head = chainhashentry(chain_key);
1641        struct lock_chain *chain;
1642        struct held_lock *hlock_curr, *hlock_next;
1643        int i, j, n, cn;
1644
1645        if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
1646                return 0;
1647        /*
1648         * We can walk it lock-free, because entries only get added
1649         * to the hash:
1650         */
1651        list_for_each_entry(chain, hash_head, entry) {
1652                if (chain->chain_key == chain_key) {
1653cache_hit:
1654                        debug_atomic_inc(&chain_lookup_hits);
1655                        if (very_verbose(class))
1656                                printk("\nhash chain already cached, key: "
1657                                        "%016Lx tail class: [%p] %s\n",
1658                                        (unsigned long long)chain_key,
1659                                        class->key, class->name);
1660                        return 0;
1661                }
1662        }
1663        if (very_verbose(class))
1664                printk("\nnew hash chain, key: %016Lx tail class: [%p] %s\n",
1665                        (unsigned long long)chain_key, class->key, class->name);
1666        /*
1667         * Allocate a new chain entry from the static array, and add
1668         * it to the hash:
1669         */
1670        if (!graph_lock())
1671                return 0;
1672        /*
1673         * We have to walk the chain again locked - to avoid duplicates:
1674         */
1675        list_for_each_entry(chain, hash_head, entry) {
1676                if (chain->chain_key == chain_key) {
1677                        graph_unlock();
1678                        goto cache_hit;
1679                }
1680        }
1681        if (unlikely(nr_lock_chains >= MAX_LOCKDEP_CHAINS)) {
1682                if (!debug_locks_off_graph_unlock())
1683                        return 0;
1684
1685                printk("BUG: MAX_LOCKDEP_CHAINS too low!\n");
1686                printk("turning off the locking correctness validator.\n");
1687                dump_stack();
1688                return 0;
1689        }
1690        chain = lock_chains + nr_lock_chains++;
1691        chain->chain_key = chain_key;
1692        chain->irq_context = hlock->irq_context;
1693        /* Find the first held_lock of current chain */
1694        hlock_next = hlock;
1695        for (i = curr->lockdep_depth - 1; i >= 0; i--) {
1696                hlock_curr = curr->held_locks + i;
1697                if (hlock_curr->irq_context != hlock_next->irq_context)
1698                        break;
1699                hlock_next = hlock;
1700        }
1701        i++;
1702        chain->depth = curr->lockdep_depth + 1 - i;
1703        cn = nr_chain_hlocks;
1704        while (cn + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS) {
1705                n = cmpxchg(&nr_chain_hlocks, cn, cn + chain->depth);
1706                if (n == cn)
1707                        break;
1708                cn = n;
1709        }
1710        if (likely(cn + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) {
1711                chain->base = cn;
1712                for (j = 0; j < chain->depth - 1; j++, i++) {
1713                        int lock_id = curr->held_locks[i].class_idx - 1;
1714                        chain_hlocks[chain->base + j] = lock_id;
1715                }
1716                chain_hlocks[chain->base + j] = class - lock_classes;
1717        }
1718        list_add_tail_rcu(&chain->entry, hash_head);
1719        debug_atomic_inc(&chain_lookup_misses);
1720        inc_chains();
1721
1722        return 1;
1723}
1724
1725static int validate_chain(struct task_struct *curr, struct lockdep_map *lock,
1726                struct held_lock *hlock, int chain_head, u64 chain_key)
1727{
1728        /*
1729         * Trylock needs to maintain the stack of held locks, but it
1730         * does not add new dependencies, because trylock can be done
1731         * in any order.
1732         *
1733         * We look up the chain_key and do the O(N^2) check and update of
1734         * the dependencies only if this is a new dependency chain.
1735         * (If lookup_chain_cache() returns with 1 it acquires
1736         * graph_lock for us)
1737         */
1738        if (!hlock->trylock && (hlock->check == 2) &&
1739            lookup_chain_cache(curr, hlock, chain_key)) {
1740                /*
1741                 * Check whether last held lock:
1742                 *
1743                 * - is irq-safe, if this lock is irq-unsafe
1744                 * - is softirq-safe, if this lock is hardirq-unsafe
1745                 *
1746                 * And check whether the new lock's dependency graph
1747                 * could lead back to the previous lock.
1748                 *
1749                 * any of these scenarios could lead to a deadlock. If
1750                 * All validations
1751                 */
1752                int ret = check_deadlock(curr, hlock, lock, hlock->read);
1753
1754                if (!ret)
1755                        return 0;
1756                /*
1757                 * Mark recursive read, as we jump over it when
1758                 * building dependencies (just like we jump over
1759                 * trylock entries):
1760                 */
1761                if (ret == 2)
1762                        hlock->read = 2;
1763                /*
1764                 * Add dependency only if this lock is not the head
1765                 * of the chain, and if it's not a secondary read-lock:
1766                 */
1767                if (!chain_head && ret != 2)
1768                        if (!check_prevs_add(curr, hlock))
1769                                return 0;
1770                graph_unlock();
1771        } else
1772                /* after lookup_chain_cache(): */
1773                if (unlikely(!debug_locks))
1774                        return 0;
1775
1776        return 1;
1777}
1778#else
1779static inline int validate_chain(struct task_struct *curr,
1780                struct lockdep_map *lock, struct held_lock *hlock,
1781                int chain_head, u64 chain_key)
1782{
1783        return 1;
1784}
1785#endif
1786
1787/*
1788 * We are building curr_chain_key incrementally, so double-check
1789 * it from scratch, to make sure that it's done correctly:
1790 */
1791static void check_chain_key(struct task_struct *curr)
1792{
1793#ifdef CONFIG_DEBUG_LOCKDEP
1794        struct held_lock *hlock, *prev_hlock = NULL;
1795        unsigned int i, id;
1796        u64 chain_key = 0;
1797
1798        for (i = 0; i < curr->lockdep_depth; i++) {
1799                hlock = curr->held_locks + i;
1800                if (chain_key != hlock->prev_chain_key) {
1801                        debug_locks_off();
1802                        WARN(1, "hm#1, depth: %u [%u], %016Lx != %016Lx\n",
1803                                curr->lockdep_depth, i,
1804                                (unsigned long long)chain_key,
1805                                (unsigned long long)hlock->prev_chain_key);
1806                        return;
1807                }
1808                id = hlock->class_idx - 1;
1809                if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
1810                        return;
1811
1812                if (prev_hlock && (prev_hlock->irq_context !=
1813                                                        hlock->irq_context))
1814                        chain_key = 0;
1815                chain_key = iterate_chain_key(chain_key, id);
1816                prev_hlock = hlock;
1817        }
1818        if (chain_key != curr->curr_chain_key) {
1819                debug_locks_off();
1820                WARN(1, "hm#2, depth: %u [%u], %016Lx != %016Lx\n",
1821                        curr->lockdep_depth, i,
1822                        (unsigned long long)chain_key,
1823                        (unsigned long long)curr->curr_chain_key);
1824        }
1825#endif
1826}
1827
1828static int
1829print_usage_bug(struct task_struct *curr, struct held_lock *this,
1830                enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
1831{
1832        if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1833                return 0;
1834
1835        printk("\n=================================\n");
1836        printk(  "[ INFO: inconsistent lock state ]\n");
1837        print_kernel_version();
1838        printk(  "---------------------------------\n");
1839
1840        printk("inconsistent {%s} -> {%s} usage.\n",
1841                usage_str[prev_bit], usage_str[new_bit]);
1842
1843        printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] takes:\n",
1844                curr->comm, task_pid_nr(curr),
1845                trace_hardirq_context(curr), hardirq_count() >> HARDIRQ_SHIFT,
1846                trace_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT,
1847                trace_hardirqs_enabled(curr),
1848                trace_softirqs_enabled(curr));
1849        print_lock(this);
1850
1851        printk("{%s} state was registered at:\n", usage_str[prev_bit]);
1852        print_stack_trace(hlock_class(this)->usage_traces + prev_bit, 1);
1853
1854        print_irqtrace_events(curr);
1855        printk("\nother info that might help us debug this:\n");
1856        lockdep_print_held_locks(curr);
1857
1858        printk("\nstack backtrace:\n");
1859        dump_stack();
1860
1861        return 0;
1862}
1863
1864/*
1865 * Print out an error if an invalid bit is set:
1866 */
1867static inline int
1868valid_state(struct task_struct *curr, struct held_lock *this,
1869            enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit)
1870{
1871        if (unlikely(hlock_class(this)->usage_mask & (1 << bad_bit)))
1872                return print_usage_bug(curr, this, bad_bit, new_bit);
1873        return 1;
1874}
1875
1876static int mark_lock(struct task_struct *curr, struct held_lock *this,
1877                     enum lock_usage_bit new_bit);
1878
1879#if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
1880
1881/*
1882 * print irq inversion bug:
1883 */
1884static int
1885print_irq_inversion_bug(struct task_struct *curr, struct lock_class *other,
1886                        struct held_lock *this, int forwards,
1887                        const char *irqclass)
1888{
1889        if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1890                return 0;
1891
1892        printk("\n=========================================================\n");
1893        printk(  "[ INFO: possible irq lock inversion dependency detected ]\n");
1894        print_kernel_version();
1895        printk(  "---------------------------------------------------------\n");
1896        printk("%s/%d just changed the state of lock:\n",
1897                curr->comm, task_pid_nr(curr));
1898        print_lock(this);
1899        if (forwards)
1900                printk("but this lock took another, %s-unsafe lock in the past:\n", irqclass);
1901        else
1902                printk("but this lock was taken by another, %s-safe lock in the past:\n", irqclass);
1903        print_lock_name(other);
1904        printk("\n\nand interrupts could create inverse lock ordering between them.\n\n");
1905
1906        printk("\nother info that might help us debug this:\n");
1907        lockdep_print_held_locks(curr);
1908
1909        printk("\nthe first lock's dependencies:\n");
1910        print_lock_dependencies(hlock_class(this), 0);
1911
1912        printk("\nthe second lock's dependencies:\n");
1913        print_lock_dependencies(other, 0);
1914
1915        printk("\nstack backtrace:\n");
1916        dump_stack();
1917
1918        return 0;
1919}
1920
1921/*
1922 * Prove that in the forwards-direction subgraph starting at <this>
1923 * there is no lock matching <mask>:
1924 */
1925static int
1926check_usage_forwards(struct task_struct *curr, struct held_lock *this,
1927                     enum lock_usage_bit bit, const char *irqclass)
1928{
1929        int ret;
1930
1931        find_usage_bit = bit;
1932        /* fills in <forwards_match> */
1933        ret = find_usage_forwards(hlock_class(this), 0);
1934        if (!ret || ret == 1)
1935                return ret;
1936
1937        return print_irq_inversion_bug(curr, forwards_match, this, 1, irqclass);
1938}
1939
1940/*
1941 * Prove that in the backwards-direction subgraph starting at <this>
1942 * there is no lock matching <mask>:
1943 */
1944static int
1945check_usage_backwards(struct task_struct *curr, struct held_lock *this,
1946                      enum lock_usage_bit bit, const char *irqclass)
1947{
1948        int ret;
1949
1950        find_usage_bit = bit;
1951        /* fills in <backwards_match> */
1952        ret = find_usage_backwards(hlock_class(this), 0);
1953        if (!ret || ret == 1)
1954                return ret;
1955
1956        return print_irq_inversion_bug(curr, backwards_match, this, 0, irqclass);
1957}
1958
1959void print_irqtrace_events(struct task_struct *curr)
1960{
1961        printk("irq event stamp: %u\n", curr->irq_events);
1962        printk("hardirqs last  enabled at (%u): ", curr->hardirq_enable_event);
1963        print_ip_sym(curr->hardirq_enable_ip);
1964        printk("hardirqs last disabled at (%u): ", curr->hardirq_disable_event);
1965        print_ip_sym(curr->hardirq_disable_ip);
1966        printk("softirqs last  enabled at (%u): ", curr->softirq_enable_event);
1967        print_ip_sym(curr->softirq_enable_ip);
1968        printk("softirqs last disabled at (%u): ", curr->softirq_disable_event);
1969        print_ip_sym(curr->softirq_disable_ip);
1970}
1971
1972static int HARDIRQ_verbose(struct lock_class *class)
1973{
1974#if HARDIRQ_VERBOSE
1975        return class_filter(class);
1976#endif
1977        return 0;
1978}
1979
1980static int SOFTIRQ_verbose(struct lock_class *class)
1981{
1982#if SOFTIRQ_VERBOSE
1983        return class_filter(class);
1984#endif
1985        return 0;
1986}
1987
1988static int RECLAIM_FS_verbose(struct lock_class *class)
1989{
1990#if RECLAIM_VERBOSE
1991        return class_filter(class);
1992#endif
1993        return 0;
1994}
1995
1996#define STRICT_READ_CHECKS      1
1997
1998static int (*state_verbose_f[])(struct lock_class *class) = {
1999#define LOCKDEP_STATE(__STATE) \
2000        __STATE##_verbose,
2001#include "lockdep_states.h"
2002#undef LOCKDEP_STATE
2003};
2004
2005static inline int state_verbose(enum lock_usage_bit bit,
2006                                struct lock_class *class)
2007{
2008        return state_verbose_f[bit >> 2](class);
2009}
2010
2011typedef int (*check_usage_f)(struct task_struct *, struct held_lock *,
2012                             enum lock_usage_bit bit, const char *name);
2013
2014static int
2015mark_lock_irq(struct task_struct *curr, struct held_lock *this,
2016                enum lock_usage_bit new_bit)
2017{
2018        int excl_bit = exclusive_bit(new_bit);
2019        int read = new_bit & 1;
2020        int dir = new_bit & 2;
2021
2022        /*
2023         * mark USED_IN has to look forwards -- to ensure no dependency
2024         * has ENABLED state, which would allow recursion deadlocks.
2025         *
2026         * mark ENABLED has to look backwards -- to ensure no dependee
2027         * has USED_IN state, which, again, would allow  recursion deadlocks.
2028         */
2029        check_usage_f usage = dir ?
2030                check_usage_backwards : check_usage_forwards;
2031
2032        /*
2033         * Validate that this particular lock does not have conflicting
2034         * usage states.
2035         */
2036        if (!valid_state(curr, this, new_bit, excl_bit))
2037                return 0;
2038
2039        /*
2040         * Validate that the lock dependencies don't have conflicting usage
2041         * states.
2042         */
2043        if ((!read || !dir || STRICT_READ_CHECKS) &&
2044                        !usage(curr, this, excl_bit, state_name(new_bit & ~1)))
2045                return 0;
2046
2047        /*
2048         * Check for read in write conflicts
2049         */
2050        if (!read) {
2051                if (!valid_state(curr, this, new_bit, excl_bit + 1))
2052                        return 0;
2053
2054                if (STRICT_READ_CHECKS &&
2055                        !usage(curr, this, excl_bit + 1,
2056                                state_name(new_bit + 1)))
2057                        return 0;
2058        }
2059
2060        if (state_verbose(new_bit, hlock_class(this)))
2061                return 2;
2062
2063        return 1;
2064}
2065
2066enum mark_type {
2067#define LOCKDEP_STATE(__STATE)  __STATE,
2068#include "lockdep_states.h"
2069#undef LOCKDEP_STATE
2070};
2071
2072/*
2073 * Mark all held locks with a usage bit:
2074 */
2075static int
2076mark_held_locks(struct task_struct *curr, enum mark_type mark)
2077{
2078        enum lock_usage_bit usage_bit;
2079        struct held_lock *hlock;
2080        int i;
2081
2082        for (i = 0; i < curr->lockdep_depth; i++) {
2083                hlock = curr->held_locks + i;
2084
2085                usage_bit = 2 + (mark << 2); /* ENABLED */
2086                if (hlock->read)
2087                        usage_bit += 1; /* READ */
2088
2089                BUG_ON(usage_bit >= LOCK_USAGE_STATES);
2090
2091                if (!mark_lock(curr, hlock, usage_bit))
2092                        return 0;
2093        }
2094
2095        return 1;
2096}
2097
2098/*
2099 * Debugging helper: via this flag we know that we are in
2100 * 'early bootup code', and will warn about any invalid irqs-on event:
2101 */
2102static int early_boot_irqs_enabled;
2103
2104void early_boot_irqs_off(void)
2105{
2106        early_boot_irqs_enabled = 0;
2107}
2108
2109void early_boot_irqs_on(void)
2110{
2111        early_boot_irqs_enabled = 1;
2112}
2113
2114/*
2115 * Hardirqs will be enabled:
2116 */
2117void trace_hardirqs_on_caller(unsigned long ip)
2118{
2119        struct task_struct *curr = current;
2120
2121        time_hardirqs_on(CALLER_ADDR0, ip);
2122
2123        if (unlikely(!debug_locks || current->lockdep_recursion))
2124                return;
2125
2126        if (DEBUG_LOCKS_WARN_ON(unlikely(!early_boot_irqs_enabled)))
2127                return;
2128
2129        if (unlikely(curr->hardirqs_enabled)) {
2130                debug_atomic_inc(&redundant_hardirqs_on);
2131                return;
2132        }
2133        /* we'll do an OFF -> ON transition: */
2134        curr->hardirqs_enabled = 1;
2135
2136        if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2137                return;
2138        if (DEBUG_LOCKS_WARN_ON(current->hardirq_context))
2139                return;
2140        /*
2141         * We are going to turn hardirqs on, so set the
2142         * usage bit for all held locks:
2143         */
2144        if (!mark_held_locks(curr, HARDIRQ))
2145                return;
2146        /*
2147         * If we have softirqs enabled, then set the usage
2148         * bit for all held locks. (disabled hardirqs prevented
2149         * this bit from being set before)
2150         */
2151        if (curr->softirqs_enabled)
2152                if (!mark_held_locks(curr, SOFTIRQ))
2153                        return;
2154
2155        curr->hardirq_enable_ip = ip;
2156        curr->hardirq_enable_event = ++curr->irq_events;
2157        debug_atomic_inc(&hardirqs_on_events);
2158}
2159EXPORT_SYMBOL(trace_hardirqs_on_caller);
2160
2161void trace_hardirqs_on(void)
2162{
2163        trace_hardirqs_on_caller(CALLER_ADDR0);
2164}
2165EXPORT_SYMBOL(trace_hardirqs_on);
2166
2167/*
2168 * Hardirqs were disabled:
2169 */
2170void trace_hardirqs_off_caller(unsigned long ip)
2171{
2172        struct task_struct *curr = current;
2173
2174        time_hardirqs_off(CALLER_ADDR0, ip);
2175
2176        if (unlikely(!debug_locks || current->lockdep_recursion))
2177                return;
2178
2179        if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2180                return;
2181
2182        if (curr->hardirqs_enabled) {
2183                /*
2184                 * We have done an ON -> OFF transition:
2185                 */
2186                curr->hardirqs_enabled = 0;
2187                curr->hardirq_disable_ip = ip;
2188                curr->hardirq_disable_event = ++curr->irq_events;
2189                debug_atomic_inc(&hardirqs_off_events);
2190        } else
2191                debug_atomic_inc(&redundant_hardirqs_off);
2192}
2193EXPORT_SYMBOL(trace_hardirqs_off_caller);
2194
2195void trace_hardirqs_off(void)
2196{
2197        trace_hardirqs_off_caller(CALLER_ADDR0);
2198}
2199EXPORT_SYMBOL(trace_hardirqs_off);
2200
2201/*
2202 * Softirqs will be enabled:
2203 */
2204void trace_softirqs_on(unsigned long ip)
2205{
2206        struct task_struct *curr = current;
2207
2208        if (unlikely(!debug_locks))
2209                return;
2210
2211        if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2212                return;
2213
2214        if (curr->softirqs_enabled) {
2215                debug_atomic_inc(&redundant_softirqs_on);
2216                return;
2217        }
2218
2219        /*
2220         * We'll do an OFF -> ON transition:
2221         */
2222        curr->softirqs_enabled = 1;
2223        curr->softirq_enable_ip = ip;
2224        curr->softirq_enable_event = ++curr->irq_events;
2225        debug_atomic_inc(&softirqs_on_events);
2226        /*
2227         * We are going to turn softirqs on, so set the
2228         * usage bit for all held locks, if hardirqs are
2229         * enabled too:
2230         */
2231        if (curr->hardirqs_enabled)
2232                mark_held_locks(curr, SOFTIRQ);
2233}
2234
2235/*
2236 * Softirqs were disabled:
2237 */
2238void trace_softirqs_off(unsigned long ip)
2239{
2240        struct task_struct *curr = current;
2241
2242        if (unlikely(!debug_locks))
2243                return;
2244
2245        if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2246                return;
2247
2248        if (curr->softirqs_enabled) {
2249                /*
2250                 * We have done an ON -> OFF transition:
2251                 */
2252                curr->softirqs_enabled = 0;
2253                curr->softirq_disable_ip = ip;
2254                curr->softirq_disable_event = ++curr->irq_events;
2255                debug_atomic_inc(&softirqs_off_events);
2256                DEBUG_LOCKS_WARN_ON(!softirq_count());
2257        } else
2258                debug_atomic_inc(&redundant_softirqs_off);
2259}
2260
2261static void __lockdep_trace_alloc(gfp_t gfp_mask, unsigned long flags)
2262{
2263        struct task_struct *curr = current;
2264
2265        if (unlikely(!debug_locks))
2266                return;
2267
2268        /* no reclaim without waiting on it */
2269        if (!(gfp_mask & __GFP_WAIT))
2270                return;
2271
2272        /* this guy won't enter reclaim */
2273        if ((curr->flags & PF_MEMALLOC) && !(gfp_mask & __GFP_NOMEMALLOC))
2274                return;
2275
2276        /* We're only interested __GFP_FS allocations for now */
2277        if (!(gfp_mask & __GFP_FS))
2278                return;
2279
2280        if (DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags)))
2281                return;
2282
2283        mark_held_locks(curr, RECLAIM_FS);
2284}
2285
2286static void check_flags(unsigned long flags);
2287
2288void lockdep_trace_alloc(gfp_t gfp_mask)
2289{
2290        unsigned long flags;
2291
2292        if (unlikely(current->lockdep_recursion))
2293                return;
2294
2295        raw_local_irq_save(flags);
2296        check_flags(flags);
2297        current->lockdep_recursion = 1;
2298        __lockdep_trace_alloc(gfp_mask, flags);
2299        current->lockdep_recursion = 0;
2300        raw_local_irq_restore(flags);
2301}
2302
2303static int mark_irqflags(struct task_struct *curr, struct held_lock *hlock)
2304{
2305        /*
2306         * If non-trylock use in a hardirq or softirq context, then
2307         * mark the lock as used in these contexts:
2308         */
2309        if (!hlock->trylock) {
2310                if (hlock->read) {
2311                        if (curr->hardirq_context)
2312                                if (!mark_lock(curr, hlock,
2313                                                LOCK_USED_IN_HARDIRQ_READ))
2314                                        return 0;
2315                        if (curr->softirq_context)
2316                                if (!mark_lock(curr, hlock,
2317                                                LOCK_USED_IN_SOFTIRQ_READ))
2318                                        return 0;
2319                } else {
2320                        if (curr->hardirq_context)
2321                                if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ))
2322                                        return 0;
2323                        if (curr->softirq_context)
2324                                if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ))
2325                                        return 0;
2326                }
2327        }
2328        if (!hlock->hardirqs_off) {
2329                if (hlock->read) {
2330                        if (!mark_lock(curr, hlock,
2331                                        LOCK_ENABLED_HARDIRQ_READ))
2332                                return 0;
2333                        if (curr->softirqs_enabled)
2334                                if (!mark_lock(curr, hlock,
2335                                                LOCK_ENABLED_SOFTIRQ_READ))
2336                                        return 0;
2337                } else {
2338                        if (!mark_lock(curr, hlock,
2339                                        LOCK_ENABLED_HARDIRQ))
2340                                return 0;
2341                        if (curr->softirqs_enabled)
2342                                if (!mark_lock(curr, hlock,
2343                                                LOCK_ENABLED_SOFTIRQ))
2344                                        return 0;
2345                }
2346        }
2347
2348        /*
2349         * We reuse the irq context infrastructure more broadly as a general
2350         * context checking code. This tests GFP_FS recursion (a lock taken
2351         * during reclaim for a GFP_FS allocation is held over a GFP_FS
2352         * allocation).
2353         */
2354        if (!hlock->trylock && (curr->lockdep_reclaim_gfp & __GFP_FS)) {
2355                if (hlock->read) {
2356                        if (!mark_lock(curr, hlock, LOCK_USED_IN_RECLAIM_FS_READ))
2357                                        return 0;
2358                } else {
2359                        if (!mark_lock(curr, hlock, LOCK_USED_IN_RECLAIM_FS))
2360                                        return 0;
2361                }
2362        }
2363
2364        return 1;
2365}
2366
2367static int separate_irq_context(struct task_struct *curr,
2368                struct held_lock *hlock)
2369{
2370        unsigned int depth = curr->lockdep_depth;
2371
2372        /*
2373         * Keep track of points where we cross into an interrupt context:
2374         */
2375        hlock->irq_context = 2*(curr->hardirq_context ? 1 : 0) +
2376                                curr->softirq_context;
2377        if (depth) {
2378                struct held_lock *prev_hlock;
2379
2380                prev_hlock = curr->held_locks + depth-1;
2381                /*
2382                 * If we cross into another context, reset the
2383                 * hash key (this also prevents the checking and the
2384                 * adding of the dependency to 'prev'):
2385                 */
2386                if (prev_hlock->irq_context != hlock->irq_context)
2387                        return 1;
2388        }
2389        return 0;
2390}
2391
2392#else
2393
2394static inline
2395int mark_lock_irq(struct task_struct *curr, struct held_lock *this,
2396                enum lock_usage_bit new_bit)
2397{
2398        WARN_ON(1);
2399        return 1;
2400}
2401
2402static inline int mark_irqflags(struct task_struct *curr,
2403                struct held_lock *hlock)
2404{
2405        return 1;
2406}
2407
2408static inline int separate_irq_context(struct task_struct *curr,
2409                struct held_lock *hlock)
2410{
2411        return 0;
2412}
2413
2414void lockdep_trace_alloc(gfp_t gfp_mask)
2415{
2416}
2417
2418#endif
2419
2420/*
2421 * Mark a lock with a usage bit, and validate the state transition:
2422 */
2423static int mark_lock(struct task_struct *curr, struct held_lock *this,
2424                             enum lock_usage_bit new_bit)
2425{
2426        unsigned int new_mask = 1 << new_bit, ret = 1;
2427
2428        /*
2429         * If already set then do not dirty the cacheline,
2430         * nor do any checks:
2431         */
2432        if (likely(hlock_class(this)->usage_mask & new_mask))
2433                return 1;
2434
2435        if (!graph_lock())
2436                return 0;
2437        /*
2438         * Make sure we didnt race:
2439         */
2440        if (unlikely(hlock_class(this)->usage_mask & new_mask)) {
2441                graph_unlock();
2442                return 1;
2443        }
2444
2445        hlock_class(this)->usage_mask |= new_mask;
2446
2447        if (!save_trace(hlock_class(this)->usage_traces + new_bit))
2448                return 0;
2449
2450        switch (new_bit) {
2451#define LOCKDEP_STATE(__STATE)                  \
2452        case LOCK_USED_IN_##__STATE:            \
2453        case LOCK_USED_IN_##__STATE##_READ:     \
2454        case LOCK_ENABLED_##__STATE:            \
2455        case LOCK_ENABLED_##__STATE##_READ:
2456#include "lockdep_states.h"
2457#undef LOCKDEP_STATE
2458                ret = mark_lock_irq(curr, this, new_bit);
2459                if (!ret)
2460                        return 0;
2461                break;
2462        case LOCK_USED:
2463                debug_atomic_dec(&nr_unused_locks);
2464                break;
2465        default:
2466                if (!debug_locks_off_graph_unlock())
2467                        return 0;
2468                WARN_ON(1);
2469                return 0;
2470        }
2471
2472        graph_unlock();
2473
2474        /*
2475         * We must printk outside of the graph_lock:
2476         */
2477        if (ret == 2) {
2478                printk("\nmarked lock as {%s}:\n", usage_str[new_bit]);
2479                print_lock(this);
2480                print_irqtrace_events(curr);
2481                dump_stack();
2482        }
2483
2484        return ret;
2485}
2486
2487/*
2488 * Initialize a lock instance's lock-class mapping info:
2489 */
2490void lockdep_init_map(struct lockdep_map *lock, const char *name,
2491                      struct lock_class_key *key, int subclass)
2492{
2493        lock->class_cache = NULL;
2494#ifdef CONFIG_LOCK_STAT
2495        lock->cpu = raw_smp_processor_id();
2496#endif
2497
2498        if (DEBUG_LOCKS_WARN_ON(!name)) {
2499                lock->name = "NULL";
2500                return;
2501        }
2502
2503        lock->name = name;
2504
2505        if (DEBUG_LOCKS_WARN_ON(!key))
2506                return;
2507        /*
2508         * Sanity check, the lock-class key must be persistent:
2509         */
2510        if (!static_obj(key)) {
2511                printk("BUG: key %p not in .data!\n", key);
2512                DEBUG_LOCKS_WARN_ON(1);
2513                return;
2514        }
2515        lock->key = key;
2516
2517        if (unlikely(!debug_locks))
2518                return;
2519
2520        if (subclass)
2521                register_lock_class(lock, subclass, 1);
2522}
2523EXPORT_SYMBOL_GPL(lockdep_init_map);
2524
2525/*
2526 * This gets called for every mutex_lock*()/spin_lock*() operation.
2527 * We maintain the dependency maps and validate the locking attempt:
2528 */
2529static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
2530                          int trylock, int read, int check, int hardirqs_off,
2531                          struct lockdep_map *nest_lock, unsigned long ip)
2532{
2533        struct task_struct *curr = current;
2534        struct lock_class *class = NULL;
2535        struct held_lock *hlock;
2536        unsigned int depth, id;
2537        int chain_head = 0;
2538        u64 chain_key;
2539
2540        if (!prove_locking)
2541                check = 1;
2542
2543        if (unlikely(!debug_locks))
2544                return 0;
2545
2546        if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2547                return 0;
2548
2549        if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
2550                debug_locks_off();
2551                printk("BUG: MAX_LOCKDEP_SUBCLASSES too low!\n");
2552                printk("turning off the locking correctness validator.\n");
2553                dump_stack();
2554                return 0;
2555        }
2556
2557        if (!subclass)
2558                class = lock->class_cache;
2559        /*
2560         * Not cached yet or subclass?
2561         */
2562        if (unlikely(!class)) {
2563                class = register_lock_class(lock, subclass, 0);
2564                if (!class)
2565                        return 0;
2566        }
2567        debug_atomic_inc((atomic_t *)&class->ops);
2568        if (very_verbose(class)) {
2569                printk("\nacquire class [%p] %s", class->key, class->name);
2570                if (class->name_version > 1)
2571                        printk("#%d", class->name_version);
2572                printk("\n");
2573                dump_stack();
2574        }
2575
2576        /*
2577         * Add the lock to the list of currently held locks.
2578         * (we dont increase the depth just yet, up until the
2579         * dependency checks are done)
2580         */
2581        depth = curr->lockdep_depth;
2582        if (DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH))
2583                return 0;
2584
2585        hlock = curr->held_locks + depth;
2586        if (DEBUG_LOCKS_WARN_ON(!class))
2587                return 0;
2588        hlock->class_idx = class - lock_classes + 1;
2589        hlock->acquire_ip = ip;
2590        hlock->instance = lock;
2591        hlock->nest_lock = nest_lock;
2592        hlock->trylock = trylock;
2593        hlock->read = read;
2594        hlock->check = check;
2595        hlock->hardirqs_off = !!hardirqs_off;
2596#ifdef CONFIG_LOCK_STAT
2597        hlock->waittime_stamp = 0;
2598        hlock->holdtime_stamp = sched_clock();
2599#endif
2600
2601        if (check == 2 && !mark_irqflags(curr, hlock))
2602                return 0;
2603
2604        /* mark it as used: */
2605        if (!mark_lock(curr, hlock, LOCK_USED))
2606                return 0;
2607
2608        /*
2609         * Calculate the chain hash: it's the combined hash of all the
2610         * lock keys along the dependency chain. We save the hash value
2611         * at every step so that we can get the current hash easily
2612         * after unlock. The chain hash is then used to cache dependency
2613         * results.
2614         *
2615         * The 'key ID' is what is the most compact key value to drive
2616         * the hash, not class->key.
2617         */
2618        id = class - lock_classes;
2619        if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
2620                return 0;
2621
2622        chain_key = curr->curr_chain_key;
2623        if (!depth) {
2624                if (DEBUG_LOCKS_WARN_ON(chain_key != 0))
2625                        return 0;
2626                chain_head = 1;
2627        }
2628
2629        hlock->prev_chain_key = chain_key;
2630        if (separate_irq_context(curr, hlock)) {
2631                chain_key = 0;
2632                chain_head = 1;
2633        }
2634        chain_key = iterate_chain_key(chain_key, id);
2635
2636        if (!validate_chain(curr, lock, hlock, chain_head, chain_key))
2637                return 0;
2638
2639        curr->curr_chain_key = chain_key;
2640        curr->lockdep_depth++;
2641        check_chain_key(curr);
2642#ifdef CONFIG_DEBUG_LOCKDEP
2643        if (unlikely(!debug_locks))
2644                return 0;
2645#endif
2646        if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
2647                debug_locks_off();
2648                printk("BUG: MAX_LOCK_DEPTH too low!\n");
2649                printk("turning off the locking correctness validator.\n");
2650                dump_stack();
2651                return 0;
2652        }
2653
2654        if (unlikely(curr->lockdep_depth > max_lockdep_depth))
2655                max_lockdep_depth = curr->lockdep_depth;
2656
2657        return 1;
2658}
2659
2660static int
2661print_unlock_inbalance_bug(struct task_struct *curr, struct lockdep_map *lock,
2662                           unsigned long ip)
2663{
2664        if (!debug_locks_off())
2665                return 0;
2666        if (debug_locks_silent)
2667                return 0;
2668
2669        printk("\n=====================================\n");
2670        printk(  "[ BUG: bad unlock balance detected! ]\n");
2671        printk(  "-------------------------------------\n");
2672        printk("%s/%d is trying to release lock (",
2673                curr->comm, task_pid_nr(curr));
2674        print_lockdep_cache(lock);
2675        printk(") at:\n");
2676        print_ip_sym(ip);
2677        printk("but there are no more locks to release!\n");
2678        printk("\nother info that might help us debug this:\n");
2679        lockdep_print_held_locks(curr);
2680
2681        printk("\nstack backtrace:\n");
2682        dump_stack();
2683
2684        return 0;
2685}
2686
2687/*
2688 * Common debugging checks for both nested and non-nested unlock:
2689 */
2690static int check_unlock(struct task_struct *curr, struct lockdep_map *lock,
2691                        unsigned long ip)
2692{
2693        if (unlikely(!debug_locks))
2694                return 0;
2695        if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2696                return 0;
2697
2698        if (curr->lockdep_depth <= 0)
2699                return print_unlock_inbalance_bug(curr, lock, ip);
2700
2701        return 1;
2702}
2703
2704static int
2705__lock_set_class(struct lockdep_map *lock, const char *name,
2706                 struct lock_class_key *key, unsigned int subclass,
2707                 unsigned long ip)
2708{
2709        struct task_struct *curr = current;
2710        struct held_lock *hlock, *prev_hlock;
2711        struct lock_class *class;
2712        unsigned int depth;
2713        int i;
2714
2715        depth = curr->lockdep_depth;
2716        if (DEBUG_LOCKS_WARN_ON(!depth))
2717                return 0;
2718
2719        prev_hlock = NULL;
2720        for (i = depth-1; i >= 0; i--) {
2721                hlock = curr->held_locks + i;
2722                /*
2723                 * We must not cross into another context:
2724                 */
2725                if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
2726                        break;
2727                if (hlock->instance == lock)
2728                        goto found_it;
2729                prev_hlock = hlock;
2730        }
2731        return print_unlock_inbalance_bug(curr, lock, ip);
2732
2733found_it:
2734        lockdep_init_map(lock, name, key, 0);
2735        class = register_lock_class(lock, subclass, 0);
2736        hlock->class_idx = class - lock_classes + 1;
2737
2738        curr->lockdep_depth = i;
2739        curr->curr_chain_key = hlock->prev_chain_key;
2740
2741        for (; i < depth; i++) {
2742                hlock = curr->held_locks + i;
2743                if (!__lock_acquire(hlock->instance,
2744                        hlock_class(hlock)->subclass, hlock->trylock,
2745                                hlock->read, hlock->check, hlock->hardirqs_off,
2746                                hlock->nest_lock, hlock->acquire_ip))
2747                        return 0;
2748        }
2749
2750        if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth))
2751                return 0;
2752        return 1;
2753}
2754
2755/*
2756 * Remove the lock to the list of currently held locks in a
2757 * potentially non-nested (out of order) manner. This is a
2758 * relatively rare operation, as all the unlock APIs default
2759 * to nested mode (which uses lock_release()):
2760 */
2761static int
2762lock_release_non_nested(struct task_struct *curr,
2763                        struct lockdep_map *lock, unsigned long ip)
2764{
2765        struct held_lock *hlock, *prev_hlock;
2766        unsigned int depth;
2767        int i;
2768
2769        /*
2770         * Check whether the lock exists in the current stack
2771         * of held locks:
2772         */
2773        depth = curr->lockdep_depth;
2774        if (DEBUG_LOCKS_WARN_ON(!depth))
2775                return 0;
2776
2777        prev_hlock = NULL;
2778        for (i = depth-1; i >= 0; i--) {
2779                hlock = curr->held_locks + i;
2780                /*
2781                 * We must not cross into another context:
2782                 */
2783                if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
2784                        break;
2785                if (hlock->instance == lock)
2786                        goto found_it;
2787                prev_hlock = hlock;
2788        }
2789        return print_unlock_inbalance_bug(curr, lock, ip);
2790
2791found_it:
2792        lock_release_holdtime(hlock);
2793
2794        /*
2795         * We have the right lock to unlock, 'hlock' points to it.
2796         * Now we remove it from the stack, and add back the other
2797         * entries (if any), recalculating the hash along the way:
2798         */
2799        curr->lockdep_depth = i;
2800        curr->curr_chain_key = hlock->prev_chain_key;
2801
2802        for (i++; i < depth; i++) {
2803                hlock = curr->held_locks + i;
2804                if (!__lock_acquire(hlock->instance,
2805                        hlock_class(hlock)->subclass, hlock->trylock,
2806                                hlock->read, hlock->check, hlock->hardirqs_off,
2807                                hlock->nest_lock, hlock->acquire_ip))
2808                        return 0;
2809        }
2810
2811        if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - 1))
2812                return 0;
2813        return 1;
2814}
2815
2816/*
2817 * Remove the lock to the list of currently held locks - this gets
2818 * called on mutex_unlock()/spin_unlock*() (or on a failed
2819 * mutex_lock_interruptible()). This is done for unlocks that nest
2820 * perfectly. (i.e. the current top of the lock-stack is unlocked)
2821 */
2822static int lock_release_nested(struct task_struct *curr,
2823                               struct lockdep_map *lock, unsigned long ip)
2824{
2825        struct held_lock *hlock;
2826        unsigned int depth;
2827
2828        /*
2829         * Pop off the top of the lock stack:
2830         */
2831        depth = curr->lockdep_depth - 1;
2832        hlock = curr->held_locks + depth;
2833
2834        /*
2835         * Is the unlock non-nested:
2836         */
2837        if (hlock->instance != lock)
2838                return lock_release_non_nested(curr, lock, ip);
2839        curr->lockdep_depth--;
2840
2841        if (DEBUG_LOCKS_WARN_ON(!depth && (hlock->prev_chain_key != 0)))
2842                return 0;
2843
2844        curr->curr_chain_key = hlock->prev_chain_key;
2845
2846        lock_release_holdtime(hlock);
2847
2848#ifdef CONFIG_DEBUG_LOCKDEP
2849        hlock->prev_chain_key = 0;
2850        hlock->class_idx = 0;
2851        hlock->acquire_ip = 0;
2852        hlock->irq_context = 0;
2853#endif
2854        return 1;
2855}
2856
2857/*
2858 * Remove the lock to the list of currently held locks - this gets
2859 * called on mutex_unlock()/spin_unlock*() (or on a failed
2860 * mutex_lock_interruptible()). This is done for unlocks that nest
2861 * perfectly. (i.e. the current top of the lock-stack is unlocked)
2862 */
2863static void
2864__lock_release(struct lockdep_map *lock, int nested, unsigned long ip)
2865{
2866        struct task_struct *curr = current;
2867
2868        if (!check_unlock(curr, lock, ip))
2869                return;
2870
2871        if (nested) {
2872                if (!lock_release_nested(curr, lock, ip))
2873                        return;
2874        } else {
2875                if (!lock_release_non_nested(curr, lock, ip))
2876                        return;
2877        }
2878
2879        check_chain_key(curr);
2880}
2881
2882/*
2883 * Check whether we follow the irq-flags state precisely:
2884 */
2885static void check_flags(unsigned long flags)
2886{
2887#if defined(CONFIG_PROVE_LOCKING) && defined(CONFIG_DEBUG_LOCKDEP) && \
2888    defined(CONFIG_TRACE_IRQFLAGS)
2889        if (!debug_locks)
2890                return;
2891
2892        if (irqs_disabled_flags(flags)) {
2893                if (DEBUG_LOCKS_WARN_ON(current->hardirqs_enabled)) {
2894                        printk("possible reason: unannotated irqs-off.\n");
2895                }
2896        } else {
2897                if (DEBUG_LOCKS_WARN_ON(!current->hardirqs_enabled)) {
2898                        printk("possible reason: unannotated irqs-on.\n");
2899                }
2900        }
2901
2902        /*
2903         * We dont accurately track softirq state in e.g.
2904         * hardirq contexts (such as on 4KSTACKS), so only
2905         * check if not in hardirq contexts:
2906         */
2907        if (!hardirq_count()) {
2908                if (softirq_count())
2909                        DEBUG_LOCKS_WARN_ON(current->softirqs_enabled);
2910                else
2911                        DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled);
2912        }
2913
2914        if (!debug_locks)
2915                print_irqtrace_events(current);
2916#endif
2917}
2918
2919void lock_set_class(struct lockdep_map *lock, const char *name,
2920                    struct lock_class_key *key, unsigned int subclass,
2921                    unsigned long ip)
2922{
2923        unsigned long flags;
2924
2925        if (unlikely(current->lockdep_recursion))
2926                return;
2927
2928        raw_local_irq_save(flags);
2929        current->lockdep_recursion = 1;
2930        check_flags(flags);
2931        if (__lock_set_class(lock, name, key, subclass, ip))
2932                check_chain_key(current);
2933        current->lockdep_recursion = 0;
2934        raw_local_irq_restore(flags);
2935}
2936EXPORT_SYMBOL_GPL(lock_set_class);
2937
2938DEFINE_TRACE(lock_acquire);
2939
2940/*
2941 * We are not always called with irqs disabled - do that here,
2942 * and also avoid lockdep recursion:
2943 */
2944void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
2945                          int trylock, int read, int check,
2946                          struct lockdep_map *nest_lock, unsigned long ip)
2947{
2948        unsigned long flags;
2949
2950        trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip);
2951
2952        if (unlikely(current->lockdep_recursion))
2953                return;
2954
2955        raw_local_irq_save(flags);
2956        check_flags(flags);
2957
2958        current->lockdep_recursion = 1;
2959        __lock_acquire(lock, subclass, trylock, read, check,
2960                       irqs_disabled_flags(flags), nest_lock, ip);
2961        current->lockdep_recursion = 0;
2962        raw_local_irq_restore(flags);
2963}
2964EXPORT_SYMBOL_GPL(lock_acquire);
2965
2966DEFINE_TRACE(lock_release);
2967
2968void lock_release(struct lockdep_map *lock, int nested,
2969                          unsigned long ip)
2970{
2971        unsigned long flags;
2972
2973        trace_lock_release(lock, nested, ip);
2974
2975        if (unlikely(current->lockdep_recursion))
2976                return;
2977
2978        raw_local_irq_save(flags);
2979        check_flags(flags);
2980        current->lockdep_recursion = 1;
2981        __lock_release(lock, nested, ip);
2982        current->lockdep_recursion = 0;
2983        raw_local_irq_restore(flags);
2984}
2985EXPORT_SYMBOL_GPL(lock_release);
2986
2987void lockdep_set_current_reclaim_state(gfp_t gfp_mask)
2988{
2989        current->lockdep_reclaim_gfp = gfp_mask;
2990}
2991
2992void lockdep_clear_current_reclaim_state(void)
2993{
2994        current->lockdep_reclaim_gfp = 0;
2995}
2996
2997#ifdef CONFIG_LOCK_STAT
2998static int
2999print_lock_contention_bug(struct task_struct *curr, struct lockdep_map *lock,
3000                           unsigned long ip)
3001{
3002        if (!debug_locks_off())
3003                return 0;
3004        if (debug_locks_silent)
3005                return 0;
3006
3007        printk("\n=================================\n");
3008        printk(  "[ BUG: bad contention detected! ]\n");
3009        printk(  "---------------------------------\n");
3010        printk("%s/%d is trying to contend lock (",
3011                curr->comm, task_pid_nr(curr));
3012        print_lockdep_cache(lock);
3013        printk(") at:\n");
3014        print_ip_sym(ip);
3015        printk("but there are no locks held!\n");
3016        printk("\nother info that might help us debug this:\n");
3017        lockdep_print_held_locks(curr);
3018
3019        printk("\nstack backtrace:\n");
3020        dump_stack();
3021
3022        return 0;
3023}
3024
3025static void
3026__lock_contended(struct lockdep_map *lock, unsigned long ip)
3027{
3028        struct task_struct *curr = current;
3029        struct held_lock *hlock, *prev_hlock;
3030        struct lock_class_stats *stats;
3031        unsigned int depth;
3032        int i, contention_point, contending_point;
3033
3034        depth = curr->lockdep_depth;
3035        if (DEBUG_LOCKS_WARN_ON(!depth))
3036                return;
3037
3038        prev_hlock = NULL;
3039        for (i = depth-1; i >= 0; i--) {
3040                hlock = curr->held_locks + i;
3041                /*
3042                 * We must not cross into another context:
3043                 */
3044                if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3045                        break;
3046                if (hlock->instance == lock)
3047                        goto found_it;
3048                prev_hlock = hlock;
3049        }
3050        print_lock_contention_bug(curr, lock, ip);
3051        return;
3052
3053found_it:
3054        hlock->waittime_stamp = sched_clock();
3055
3056        contention_point = lock_point(hlock_class(hlock)->contention_point, ip);
3057        contending_point = lock_point(hlock_class(hlock)->contending_point,
3058                                      lock->ip);
3059
3060        stats = get_lock_stats(hlock_class(hlock));
3061        if (contention_point < LOCKSTAT_POINTS)
3062                stats->contention_point[contention_point]++;
3063        if (contending_point < LOCKSTAT_POINTS)
3064                stats->contending_point[contending_point]++;
3065        if (lock->cpu != smp_processor_id())
3066                stats->bounces[bounce_contended + !!hlock->read]++;
3067        put_lock_stats(stats);
3068}
3069
3070static void
3071__lock_acquired(struct lockdep_map *lock, unsigned long ip)
3072{
3073        struct task_struct *curr = current;
3074        struct held_lock *hlock, *prev_hlock;
3075        struct lock_class_stats *stats;
3076        unsigned int depth;
3077        u64 now;
3078        s64 waittime = 0;
3079        int i, cpu;
3080
3081        depth = curr->lockdep_depth;
3082        if (DEBUG_LOCKS_WARN_ON(!depth))
3083                return;
3084
3085        prev_hlock = NULL;
3086        for (i = depth-1; i >= 0; i--) {
3087                hlock = curr->held_locks + i;
3088                /*
3089                 * We must not cross into another context:
3090                 */
3091                if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3092                        break;
3093                if (hlock->instance == lock)
3094                        goto found_it;
3095                prev_hlock = hlock;
3096        }
3097        print_lock_contention_bug(curr, lock, _RET_IP_);
3098        return;
3099
3100found_it:
3101        cpu = smp_processor_id();
3102        if (hlock->waittime_stamp) {
3103                now = sched_clock();
3104                waittime = now - hlock->waittime_stamp;
3105                hlock->holdtime_stamp = now;
3106        }
3107
3108        stats = get_lock_stats(hlock_class(hlock));
3109        if (waittime) {
3110                if (hlock->read)
3111                        lock_time_inc(&stats->read_waittime, waittime);
3112                else
3113                        lock_time_inc(&stats->write_waittime, waittime);
3114        }
3115        if (lock->cpu != cpu)
3116                stats->bounces[bounce_acquired + !!hlock->read]++;
3117        put_lock_stats(stats);
3118
3119        lock->cpu = cpu;
3120        lock->ip = ip;
3121}
3122
3123DEFINE_TRACE(lock_contended);
3124
3125void lock_contended(struct lockdep_map *lock, unsigned long ip)
3126{
3127        unsigned long flags;
3128
3129        trace_lock_contended(lock, ip);
3130
3131        if (unlikely(!lock_stat))
3132                return;
3133
3134        if (unlikely(current->lockdep_recursion))
3135                return;
3136
3137        raw_local_irq_save(flags);
3138        check_flags(flags);
3139        current->lockdep_recursion = 1;
3140        __lock_contended(lock, ip);
3141        current->lockdep_recursion = 0;
3142        raw_local_irq_restore(flags);
3143}
3144EXPORT_SYMBOL_GPL(lock_contended);
3145
3146DEFINE_TRACE(lock_acquired);
3147
3148void lock_acquired(struct lockdep_map *lock, unsigned long ip)
3149{
3150        unsigned long flags;
3151
3152        trace_lock_acquired(lock, ip);
3153
3154        if (unlikely(!lock_stat))
3155                return;
3156
3157        if (unlikely(current->lockdep_recursion))
3158                return;
3159
3160        raw_local_irq_save(flags);
3161        check_flags(flags);
3162        current->lockdep_recursion = 1;
3163        __lock_acquired(lock, ip);
3164        current->lockdep_recursion = 0;
3165        raw_local_irq_restore(flags);
3166}
3167EXPORT_SYMBOL_GPL(lock_acquired);
3168#endif
3169
3170/*
3171 * Used by the testsuite, sanitize the validator state
3172 * after a simulated failure:
3173 */
3174
3175void lockdep_reset(void)
3176{
3177        unsigned long flags;
3178        int i;
3179
3180        raw_local_irq_save(flags);
3181        current->curr_chain_key = 0;
3182        current->lockdep_depth = 0;
3183        current->lockdep_recursion = 0;
3184        memset(current->held_locks, 0, MAX_LOCK_DEPTH*sizeof(struct held_lock));
3185        nr_hardirq_chains = 0;
3186        nr_softirq_chains = 0;
3187        nr_process_chains = 0;
3188        debug_locks = 1;
3189        for (i = 0; i < CHAINHASH_SIZE; i++)
3190                INIT_LIST_HEAD(chainhash_table + i);
3191        raw_local_irq_restore(flags);
3192}
3193
3194static void zap_class(struct lock_class *class)
3195{
3196        int i;
3197
3198        /*
3199         * Remove all dependencies this lock is
3200         * involved in:
3201         */
3202        for (i = 0; i < nr_list_entries; i++) {
3203                if (list_entries[i].class == class)
3204                        list_del_rcu(&list_entries[i].entry);
3205        }
3206        /*
3207         * Unhash the class and remove it from the all_lock_classes list:
3208         */
3209        list_del_rcu(&class->hash_entry);
3210        list_del_rcu(&class->lock_entry);
3211
3212        class->key = NULL;
3213}
3214
3215static inline int within(const void *addr, void *start, unsigned long size)
3216{
3217        return addr >= start && addr < start + size;
3218}
3219
3220void lockdep_free_key_range(void *start, unsigned long size)
3221{
3222        struct lock_class *class, *next;
3223        struct list_head *head;
3224        unsigned long flags;
3225        int i;
3226        int locked;
3227
3228        raw_local_irq_save(flags);
3229        locked = graph_lock();
3230
3231        /*
3232         * Unhash all classes that were created by this module:
3233         */
3234        for (i = 0; i < CLASSHASH_SIZE; i++) {
3235                head = classhash_table + i;
3236                if (list_empty(head))
3237                        continue;
3238                list_for_each_entry_safe(class, next, head, hash_entry) {
3239                        if (within(class->key, start, size))
3240                                zap_class(class);
3241                        else if (within(class->name, start, size))
3242                                zap_class(class);
3243                }
3244        }
3245
3246        if (locked)
3247                graph_unlock();
3248        raw_local_irq_restore(flags);
3249}
3250
3251void lockdep_reset_lock(struct lockdep_map *lock)
3252{
3253        struct lock_class *class, *next;
3254        struct list_head *head;
3255        unsigned long flags;
3256        int i, j;
3257        int locked;
3258
3259        raw_local_irq_save(flags);
3260
3261        /*
3262         * Remove all classes this lock might have:
3263         */
3264        for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) {
3265                /*
3266                 * If the class exists we look it up and zap it:
3267                 */
3268                class = look_up_lock_class(lock, j);
3269                if (class)
3270                        zap_class(class);
3271        }
3272        /*
3273         * Debug check: in the end all mapped classes should
3274         * be gone.
3275         */
3276        locked = graph_lock();
3277        for (i = 0; i < CLASSHASH_SIZE; i++) {
3278                head = classhash_table + i;
3279                if (list_empty(head))
3280                        continue;
3281                list_for_each_entry_safe(class, next, head, hash_entry) {
3282                        if (unlikely(class == lock->class_cache)) {
3283                                if (debug_locks_off_graph_unlock())
3284                                        WARN_ON(1);
3285                                goto out_restore;
3286                        }
3287                }
3288        }
3289        if (locked)
3290                graph_unlock();
3291
3292out_restore:
3293        raw_local_irq_restore(flags);
3294}
3295
3296void lockdep_init(void)
3297{
3298        int i;
3299
3300        /*
3301         * Some architectures have their own start_kernel()
3302         * code which calls lockdep_init(), while we also
3303         * call lockdep_init() from the start_kernel() itself,
3304         * and we want to initialize the hashes only once:
3305         */
3306        if (lockdep_initialized)
3307                return;
3308
3309        for (i = 0; i < CLASSHASH_SIZE; i++)
3310                INIT_LIST_HEAD(classhash_table + i);
3311
3312        for (i = 0; i < CHAINHASH_SIZE; i++)
3313                INIT_LIST_HEAD(chainhash_table + i);
3314
3315        lockdep_initialized = 1;
3316}
3317
3318void __init lockdep_info(void)
3319{
3320        printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");
3321
3322        printk("... MAX_LOCKDEP_SUBCLASSES:  %lu\n", MAX_LOCKDEP_SUBCLASSES);
3323        printk("... MAX_LOCK_DEPTH:          %lu\n", MAX_LOCK_DEPTH);
3324        printk("... MAX_LOCKDEP_KEYS:        %lu\n", MAX_LOCKDEP_KEYS);
3325        printk("... CLASSHASH_SIZE:          %lu\n", CLASSHASH_SIZE);
3326        printk("... MAX_LOCKDEP_ENTRIES:     %lu\n", MAX_LOCKDEP_ENTRIES);
3327        printk("... MAX_LOCKDEP_CHAINS:      %lu\n", MAX_LOCKDEP_CHAINS);
3328        printk("... CHAINHASH_SIZE:          %lu\n", CHAINHASH_SIZE);
3329
3330        printk(" memory used by lock dependency info: %lu kB\n",
3331                (sizeof(struct lock_class) * MAX_LOCKDEP_KEYS +
3332                sizeof(struct list_head) * CLASSHASH_SIZE +
3333                sizeof(struct lock_list) * MAX_LOCKDEP_ENTRIES +
3334                sizeof(struct lock_chain) * MAX_LOCKDEP_CHAINS +
3335                sizeof(struct list_head) * CHAINHASH_SIZE) / 1024);
3336
3337        printk(" per task-struct memory footprint: %lu bytes\n",
3338                sizeof(struct held_lock) * MAX_LOCK_DEPTH);
3339
3340#ifdef CONFIG_DEBUG_LOCKDEP
3341        if (lockdep_init_error) {
3342                printk("WARNING: lockdep init error! Arch code didn't call lockdep_init() early enough?\n");
3343                printk("Call stack leading to lockdep invocation was:\n");
3344                print_stack_trace(&lockdep_init_trace, 0);
3345        }
3346#endif
3347}
3348
3349static void
3350print_freed_lock_bug(struct task_struct *curr, const void *mem_from,
3351                     const void *mem_to, struct held_lock *hlock)
3352{
3353        if (!debug_locks_off())
3354                return;
3355        if (debug_locks_silent)
3356                return;
3357
3358        printk("\n=========================\n");
3359        printk(  "[ BUG: held lock freed! ]\n");
3360        printk(  "-------------------------\n");
3361        printk("%s/%d is freeing memory %p-%p, with a lock still held there!\n",
3362                curr->comm, task_pid_nr(curr), mem_from, mem_to-1);
3363        print_lock(hlock);
3364        lockdep_print_held_locks(curr);
3365
3366        printk("\nstack backtrace:\n");
3367        dump_stack();
3368}
3369
3370static inline int not_in_range(const void* mem_from, unsigned long mem_len,
3371                                const void* lock_from, unsigned long lock_len)
3372{
3373        return lock_from + lock_len <= mem_from ||
3374                mem_from + mem_len <= lock_from;
3375}
3376
3377/*
3378 * Called when kernel memory is freed (or unmapped), or if a lock
3379 * is destroyed or reinitialized - this code checks whether there is
3380 * any held lock in the memory range of <from> to <to>:
3381 */
3382void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len)
3383{
3384        struct task_struct *curr = current;
3385        struct held_lock *hlock;
3386        unsigned long flags;
3387        int i;
3388
3389        if (unlikely(!debug_locks))
3390                return;
3391
3392        local_irq_save(flags);
3393        for (i = 0; i < curr->lockdep_depth; i++) {
3394                hlock = curr->held_locks + i;
3395
3396                if (not_in_range(mem_from, mem_len, hlock->instance,
3397                                        sizeof(*hlock->instance)))
3398                        continue;
3399
3400                print_freed_lock_bug(curr, mem_from, mem_from + mem_len, hlock);
3401                break;
3402        }
3403        local_irq_restore(flags);
3404}
3405EXPORT_SYMBOL_GPL(debug_check_no_locks_freed);
3406
3407static void print_held_locks_bug(struct task_struct *curr)
3408{
3409        if (!debug_locks_off())
3410                return;
3411        if (debug_locks_silent)
3412                return;
3413
3414        printk("\n=====================================\n");
3415        printk(  "[ BUG: lock held at task exit time! ]\n");
3416        printk(  "-------------------------------------\n");
3417        printk("%s/%d is exiting with locks still held!\n",
3418                curr->comm, task_pid_nr(curr));
3419        lockdep_print_held_locks(curr);
3420
3421        printk("\nstack backtrace:\n");
3422        dump_stack();
3423}
3424
3425void debug_check_no_locks_held(struct task_struct *task)
3426{
3427        if (unlikely(task->lockdep_depth > 0))
3428                print_held_locks_bug(task);
3429}
3430
3431void debug_show_all_locks(void)
3432{
3433        struct task_struct *g, *p;
3434        int count = 10;
3435        int unlock = 1;
3436
3437        if (unlikely(!debug_locks)) {
3438                printk("INFO: lockdep is turned off.\n");
3439                return;
3440        }
3441        printk("\nShowing all locks held in the system:\n");
3442
3443        /*
3444         * Here we try to get the tasklist_lock as hard as possible,
3445         * if not successful after 2 seconds we ignore it (but keep
3446         * trying). This is to enable a debug printout even if a
3447         * tasklist_lock-holding task deadlocks or crashes.
3448         */
3449retry:
3450        if (!read_trylock(&tasklist_lock)) {
3451                if (count == 10)
3452                        printk("hm, tasklist_lock locked, retrying... ");
3453                if (count) {
3454                        count--;
3455                        printk(" #%d", 10-count);
3456                        mdelay(200);
3457                        goto retry;
3458                }
3459                printk(" ignoring it.\n");
3460                unlock = 0;
3461        } else {
3462                if (count != 10)
3463                        printk(KERN_CONT " locked it.\n");
3464        }
3465
3466        do_each_thread(g, p) {
3467                /*
3468                 * It's not reliable to print a task's held locks
3469                 * if it's not sleeping (or if it's not the current
3470                 * task):
3471                 */
3472                if (p->state == TASK_RUNNING && p != current)
3473                        continue;
3474                if (p->lockdep_depth)
3475                        lockdep_print_held_locks(p);
3476                if (!unlock)
3477                        if (read_trylock(&tasklist_lock))
3478                                unlock = 1;
3479        } while_each_thread(g, p);
3480
3481        printk("\n");
3482        printk("=============================================\n\n");
3483
3484        if (unlock)
3485                read_unlock(&tasklist_lock);
3486}
3487EXPORT_SYMBOL_GPL(debug_show_all_locks);
3488
3489/*
3490 * Careful: only use this function if you are sure that
3491 * the task cannot run in parallel!
3492 */
3493void __debug_show_held_locks(struct task_struct *task)
3494{
3495        if (unlikely(!debug_locks)) {
3496                printk("INFO: lockdep is turned off.\n");
3497                return;
3498        }
3499        lockdep_print_held_locks(task);
3500}
3501EXPORT_SYMBOL_GPL(__debug_show_held_locks);
3502
3503void debug_show_held_locks(struct task_struct *task)
3504{
3505                __debug_show_held_locks(task);
3506}
3507EXPORT_SYMBOL_GPL(debug_show_held_locks);
3508
3509void lockdep_sys_exit(void)
3510{
3511        struct task_struct *curr = current;
3512
3513        if (unlikely(curr->lockdep_depth)) {
3514                if (!debug_locks_off())
3515                        return;
3516                printk("\n================================================\n");
3517                printk(  "[ BUG: lock held when returning to user space! ]\n");
3518                printk(  "------------------------------------------------\n");
3519                printk("%s/%d is leaving the kernel with locks still held!\n",
3520                                curr->comm, curr->pid);
3521                lockdep_print_held_locks(curr);
3522        }
3523}
3524