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 <linux/bitops.h>
  46#include <linux/gfp.h>
  47#include <linux/kmemcheck.h>
  48
  49#include <asm/sections.h>
  50
  51#include "lockdep_internals.h"
  52
  53#define CREATE_TRACE_POINTS
  54#include <trace/events/lock.h>
  55
  56#ifdef CONFIG_PROVE_LOCKING
  57int prove_locking = 1;
  58module_param(prove_locking, int, 0644);
  59#else
  60#define prove_locking 0
  61#endif
  62
  63#ifdef CONFIG_LOCK_STAT
  64int lock_stat = 1;
  65module_param(lock_stat, int, 0644);
  66#else
  67#define lock_stat 0
  68#endif
  69
  70/*
  71 * lockdep_lock: protects the lockdep graph, the hashes and the
  72 *               class/list/hash allocators.
  73 *
  74 * This is one of the rare exceptions where it's justified
  75 * to use a raw spinlock - we really dont want the spinlock
  76 * code to recurse back into the lockdep code...
  77 */
  78static arch_spinlock_t lockdep_lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
  79
  80static int graph_lock(void)
  81{
  82        arch_spin_lock(&lockdep_lock);
  83        /*
  84         * Make sure that if another CPU detected a bug while
  85         * walking the graph we dont change it (while the other
  86         * CPU is busy printing out stuff with the graph lock
  87         * dropped already)
  88         */
  89        if (!debug_locks) {
  90                arch_spin_unlock(&lockdep_lock);
  91                return 0;
  92        }
  93        /* prevent any recursions within lockdep from causing deadlocks */
  94        current->lockdep_recursion++;
  95        return 1;
  96}
  97
  98static inline int graph_unlock(void)
  99{
 100        if (debug_locks && !arch_spin_is_locked(&lockdep_lock)) {
 101                /*
 102                 * The lockdep graph lock isn't locked while we expect it to
 103                 * be, we're confused now, bye!
 104                 */
 105                return DEBUG_LOCKS_WARN_ON(1);
 106        }
 107
 108        current->lockdep_recursion--;
 109        arch_spin_unlock(&lockdep_lock);
 110        return 0;
 111}
 112
 113/*
 114 * Turn lock debugging off and return with 0 if it was off already,
 115 * and also release the graph lock:
 116 */
 117static inline int debug_locks_off_graph_unlock(void)
 118{
 119        int ret = debug_locks_off();
 120
 121        arch_spin_unlock(&lockdep_lock);
 122
 123        return ret;
 124}
 125
 126static int lockdep_initialized;
 127
 128unsigned long nr_list_entries;
 129static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES];
 130
 131/*
 132 * All data structures here are protected by the global debug_lock.
 133 *
 134 * Mutex key structs only get allocated, once during bootup, and never
 135 * get freed - this significantly simplifies the debugging code.
 136 */
 137unsigned long nr_lock_classes;
 138static struct lock_class lock_classes[MAX_LOCKDEP_KEYS];
 139
 140static inline struct lock_class *hlock_class(struct held_lock *hlock)
 141{
 142        if (!hlock->class_idx) {
 143                /*
 144                 * Someone passed in garbage, we give up.
 145                 */
 146                DEBUG_LOCKS_WARN_ON(1);
 147                return NULL;
 148        }
 149        return lock_classes + hlock->class_idx - 1;
 150}
 151
 152#ifdef CONFIG_LOCK_STAT
 153static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS],
 154                      cpu_lock_stats);
 155
 156static inline u64 lockstat_clock(void)
 157{
 158        return local_clock();
 159}
 160
 161static int lock_point(unsigned long points[], unsigned long ip)
 162{
 163        int i;
 164
 165        for (i = 0; i < LOCKSTAT_POINTS; i++) {
 166                if (points[i] == 0) {
 167                        points[i] = ip;
 168                        break;
 169                }
 170                if (points[i] == ip)
 171                        break;
 172        }
 173
 174        return i;
 175}
 176
 177static void lock_time_inc(struct lock_time *lt, u64 time)
 178{
 179        if (time > lt->max)
 180                lt->max = time;
 181
 182        if (time < lt->min || !lt->nr)
 183                lt->min = time;
 184
 185        lt->total += time;
 186        lt->nr++;
 187}
 188
 189static inline void lock_time_add(struct lock_time *src, struct lock_time *dst)
 190{
 191        if (!src->nr)
 192                return;
 193
 194        if (src->max > dst->max)
 195                dst->max = src->max;
 196
 197        if (src->min < dst->min || !dst->nr)
 198                dst->min = src->min;
 199
 200        dst->total += src->total;
 201        dst->nr += src->nr;
 202}
 203
 204struct lock_class_stats lock_stats(struct lock_class *class)
 205{
 206        struct lock_class_stats stats;
 207        int cpu, i;
 208
 209        memset(&stats, 0, sizeof(struct lock_class_stats));
 210        for_each_possible_cpu(cpu) {
 211                struct lock_class_stats *pcs =
 212                        &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
 213
 214                for (i = 0; i < ARRAY_SIZE(stats.contention_point); i++)
 215                        stats.contention_point[i] += pcs->contention_point[i];
 216
 217                for (i = 0; i < ARRAY_SIZE(stats.contending_point); i++)
 218                        stats.contending_point[i] += pcs->contending_point[i];
 219
 220                lock_time_add(&pcs->read_waittime, &stats.read_waittime);
 221                lock_time_add(&pcs->write_waittime, &stats.write_waittime);
 222
 223                lock_time_add(&pcs->read_holdtime, &stats.read_holdtime);
 224                lock_time_add(&pcs->write_holdtime, &stats.write_holdtime);
 225
 226                for (i = 0; i < ARRAY_SIZE(stats.bounces); i++)
 227                        stats.bounces[i] += pcs->bounces[i];
 228        }
 229
 230        return stats;
 231}
 232
 233void clear_lock_stats(struct lock_class *class)
 234{
 235        int cpu;
 236
 237        for_each_possible_cpu(cpu) {
 238                struct lock_class_stats *cpu_stats =
 239                        &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
 240
 241                memset(cpu_stats, 0, sizeof(struct lock_class_stats));
 242        }
 243        memset(class->contention_point, 0, sizeof(class->contention_point));
 244        memset(class->contending_point, 0, sizeof(class->contending_point));
 245}
 246
 247static struct lock_class_stats *get_lock_stats(struct lock_class *class)
 248{
 249        return &get_cpu_var(cpu_lock_stats)[class - lock_classes];
 250}
 251
 252static void put_lock_stats(struct lock_class_stats *stats)
 253{
 254        put_cpu_var(cpu_lock_stats);
 255}
 256
 257static void lock_release_holdtime(struct held_lock *hlock)
 258{
 259        struct lock_class_stats *stats;
 260        u64 holdtime;
 261
 262        if (!lock_stat)
 263                return;
 264
 265        holdtime = lockstat_clock() - hlock->holdtime_stamp;
 266
 267        stats = get_lock_stats(hlock_class(hlock));
 268        if (hlock->read)
 269                lock_time_inc(&stats->read_holdtime, holdtime);
 270        else
 271                lock_time_inc(&stats->write_holdtime, holdtime);
 272        put_lock_stats(stats);
 273}
 274#else
 275static inline void lock_release_holdtime(struct held_lock *hlock)
 276{
 277}
 278#endif
 279
 280/*
 281 * We keep a global list of all lock classes. The list only grows,
 282 * never shrinks. The list is only accessed with the lockdep
 283 * spinlock lock held.
 284 */
 285LIST_HEAD(all_lock_classes);
 286
 287/*
 288 * The lockdep classes are in a hash-table as well, for fast lookup:
 289 */
 290#define CLASSHASH_BITS          (MAX_LOCKDEP_KEYS_BITS - 1)
 291#define CLASSHASH_SIZE          (1UL << CLASSHASH_BITS)
 292#define __classhashfn(key)      hash_long((unsigned long)key, CLASSHASH_BITS)
 293#define classhashentry(key)     (classhash_table + __classhashfn((key)))
 294
 295static struct list_head classhash_table[CLASSHASH_SIZE];
 296
 297/*
 298 * We put the lock dependency chains into a hash-table as well, to cache
 299 * their existence:
 300 */
 301#define CHAINHASH_BITS          (MAX_LOCKDEP_CHAINS_BITS-1)
 302#define CHAINHASH_SIZE          (1UL << CHAINHASH_BITS)
 303#define __chainhashfn(chain)    hash_long(chain, CHAINHASH_BITS)
 304#define chainhashentry(chain)   (chainhash_table + __chainhashfn((chain)))
 305
 306static struct list_head chainhash_table[CHAINHASH_SIZE];
 307
 308/*
 309 * The hash key of the lock dependency chains is a hash itself too:
 310 * it's a hash of all locks taken up to that lock, including that lock.
 311 * It's a 64-bit hash, because it's important for the keys to be
 312 * unique.
 313 */
 314#define iterate_chain_key(key1, key2) \
 315        (((key1) << MAX_LOCKDEP_KEYS_BITS) ^ \
 316        ((key1) >> (64-MAX_LOCKDEP_KEYS_BITS)) ^ \
 317        (key2))
 318
 319void lockdep_off(void)
 320{
 321        current->lockdep_recursion++;
 322}
 323EXPORT_SYMBOL(lockdep_off);
 324
 325void lockdep_on(void)
 326{
 327        current->lockdep_recursion--;
 328}
 329EXPORT_SYMBOL(lockdep_on);
 330
 331/*
 332 * Debugging switches:
 333 */
 334
 335#define VERBOSE                 0
 336#define VERY_VERBOSE            0
 337
 338#if VERBOSE
 339# define HARDIRQ_VERBOSE        1
 340# define SOFTIRQ_VERBOSE        1
 341# define RECLAIM_VERBOSE        1
 342#else
 343# define HARDIRQ_VERBOSE        0
 344# define SOFTIRQ_VERBOSE        0
 345# define RECLAIM_VERBOSE        0
 346#endif
 347
 348#if VERBOSE || HARDIRQ_VERBOSE || SOFTIRQ_VERBOSE || RECLAIM_VERBOSE
 349/*
 350 * Quick filtering for interesting events:
 351 */
 352static int class_filter(struct lock_class *class)
 353{
 354#if 0
 355        /* Example */
 356        if (class->name_version == 1 &&
 357                        !strcmp(class->name, "lockname"))
 358                return 1;
 359        if (class->name_version == 1 &&
 360                        !strcmp(class->name, "&struct->lockfield"))
 361                return 1;
 362#endif
 363        /* Filter everything else. 1 would be to allow everything else */
 364        return 0;
 365}
 366#endif
 367
 368static int verbose(struct lock_class *class)
 369{
 370#if VERBOSE
 371        return class_filter(class);
 372#endif
 373        return 0;
 374}
 375
 376/*
 377 * Stack-trace: tightly packed array of stack backtrace
 378 * addresses. Protected by the graph_lock.
 379 */
 380unsigned long nr_stack_trace_entries;
 381static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];
 382
 383static void print_lockdep_off(const char *bug_msg)
 384{
 385        printk(KERN_DEBUG "%s\n", bug_msg);
 386        printk(KERN_DEBUG "turning off the locking correctness validator.\n");
 387        printk(KERN_DEBUG "Please attach the output of /proc/lock_stat to the bug report\n");
 388}
 389
 390static int save_trace(struct stack_trace *trace)
 391{
 392        trace->nr_entries = 0;
 393        trace->max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries;
 394        trace->entries = stack_trace + nr_stack_trace_entries;
 395
 396        trace->skip = 3;
 397
 398        save_stack_trace(trace);
 399
 400        /*
 401         * Some daft arches put -1 at the end to indicate its a full trace.
 402         *
 403         * <rant> this is buggy anyway, since it takes a whole extra entry so a
 404         * complete trace that maxes out the entries provided will be reported
 405         * as incomplete, friggin useless </rant>
 406         */
 407        if (trace->nr_entries != 0 &&
 408            trace->entries[trace->nr_entries-1] == ULONG_MAX)
 409                trace->nr_entries--;
 410
 411        trace->max_entries = trace->nr_entries;
 412
 413        nr_stack_trace_entries += trace->nr_entries;
 414
 415        if (nr_stack_trace_entries >= MAX_STACK_TRACE_ENTRIES-1) {
 416                if (!debug_locks_off_graph_unlock())
 417                        return 0;
 418
 419                print_lockdep_off("BUG: MAX_STACK_TRACE_ENTRIES too low!");
 420                dump_stack();
 421
 422                return 0;
 423        }
 424
 425        return 1;
 426}
 427
 428unsigned int nr_hardirq_chains;
 429unsigned int nr_softirq_chains;
 430unsigned int nr_process_chains;
 431unsigned int max_lockdep_depth;
 432
 433#ifdef CONFIG_DEBUG_LOCKDEP
 434/*
 435 * We cannot printk in early bootup code. Not even early_printk()
 436 * might work. So we mark any initialization errors and printk
 437 * about it later on, in lockdep_info().
 438 */
 439static int lockdep_init_error;
 440static const char *lock_init_error;
 441static unsigned long lockdep_init_trace_data[20];
 442static struct stack_trace lockdep_init_trace = {
 443        .max_entries = ARRAY_SIZE(lockdep_init_trace_data),
 444        .entries = lockdep_init_trace_data,
 445};
 446
 447/*
 448 * Various lockdep statistics:
 449 */
 450DEFINE_PER_CPU(struct lockdep_stats, lockdep_stats);
 451#endif
 452
 453/*
 454 * Locking printouts:
 455 */
 456
 457#define __USAGE(__STATE)                                                \
 458        [LOCK_USED_IN_##__STATE] = "IN-"__stringify(__STATE)"-W",       \
 459        [LOCK_ENABLED_##__STATE] = __stringify(__STATE)"-ON-W",         \
 460        [LOCK_USED_IN_##__STATE##_READ] = "IN-"__stringify(__STATE)"-R",\
 461        [LOCK_ENABLED_##__STATE##_READ] = __stringify(__STATE)"-ON-R",
 462
 463static const char *usage_str[] =
 464{
 465#define LOCKDEP_STATE(__STATE) __USAGE(__STATE)
 466#include "lockdep_states.h"
 467#undef LOCKDEP_STATE
 468        [LOCK_USED] = "INITIAL USE",
 469};
 470
 471const char * __get_key_name(struct lockdep_subclass_key *key, char *str)
 472{
 473        return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str);
 474}
 475
 476static inline unsigned long lock_flag(enum lock_usage_bit bit)
 477{
 478        return 1UL << bit;
 479}
 480
 481static char get_usage_char(struct lock_class *class, enum lock_usage_bit bit)
 482{
 483        char c = '.';
 484
 485        if (class->usage_mask & lock_flag(bit + 2))
 486                c = '+';
 487        if (class->usage_mask & lock_flag(bit)) {
 488                c = '-';
 489                if (class->usage_mask & lock_flag(bit + 2))
 490                        c = '?';
 491        }
 492
 493        return c;
 494}
 495
 496void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS])
 497{
 498        int i = 0;
 499
 500#define LOCKDEP_STATE(__STATE)                                          \
 501        usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE);     \
 502        usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE##_READ);
 503#include "lockdep_states.h"
 504#undef LOCKDEP_STATE
 505
 506        usage[i] = '\0';
 507}
 508
 509static void __print_lock_name(struct lock_class *class)
 510{
 511        char str[KSYM_NAME_LEN];
 512        const char *name;
 513
 514        name = class->name;
 515        if (!name) {
 516                name = __get_key_name(class->key, str);
 517                printk("%s", name);
 518        } else {
 519                printk("%s", name);
 520                if (class->name_version > 1)
 521                        printk("#%d", class->name_version);
 522                if (class->subclass)
 523                        printk("/%d", class->subclass);
 524        }
 525}
 526
 527static void print_lock_name(struct lock_class *class)
 528{
 529        char usage[LOCK_USAGE_CHARS];
 530
 531        get_usage_chars(class, usage);
 532
 533        printk(" (");
 534        __print_lock_name(class);
 535        printk("){%s}", usage);
 536}
 537
 538static void print_lockdep_cache(struct lockdep_map *lock)
 539{
 540        const char *name;
 541        char str[KSYM_NAME_LEN];
 542
 543        name = lock->name;
 544        if (!name)
 545                name = __get_key_name(lock->key->subkeys, str);
 546
 547        printk("%s", name);
 548}
 549
 550static void print_lock(struct held_lock *hlock)
 551{
 552        print_lock_name(hlock_class(hlock));
 553        printk(", at: ");
 554        print_ip_sym(hlock->acquire_ip);
 555}
 556
 557static void lockdep_print_held_locks(struct task_struct *curr)
 558{
 559        int i, depth = curr->lockdep_depth;
 560
 561        if (!depth) {
 562                printk("no locks held by %s/%d.\n", curr->comm, task_pid_nr(curr));
 563                return;
 564        }
 565        printk("%d lock%s held by %s/%d:\n",
 566                depth, depth > 1 ? "s" : "", curr->comm, task_pid_nr(curr));
 567
 568        for (i = 0; i < depth; i++) {
 569                printk(" #%d: ", i);
 570                print_lock(curr->held_locks + i);
 571        }
 572}
 573
 574static void print_kernel_ident(void)
 575{
 576        printk("%s %.*s %s\n", init_utsname()->release,
 577                (int)strcspn(init_utsname()->version, " "),
 578                init_utsname()->version,
 579                print_tainted());
 580}
 581
 582static int very_verbose(struct lock_class *class)
 583{
 584#if VERY_VERBOSE
 585        return class_filter(class);
 586#endif
 587        return 0;
 588}
 589
 590/*
 591 * Is this the address of a static object:
 592 */
 593static int static_obj(void *obj)
 594{
 595        unsigned long start = (unsigned long) &_stext,
 596                      end   = (unsigned long) &_end,
 597                      addr  = (unsigned long) obj;
 598
 599        /*
 600         * static variable?
 601         */
 602        if ((addr >= start) && (addr < end))
 603                return 1;
 604
 605        if (arch_is_kernel_data(addr))
 606                return 1;
 607
 608        /*
 609         * in-kernel percpu var?
 610         */
 611        if (is_kernel_percpu_address(addr))
 612                return 1;
 613
 614        /*
 615         * module static or percpu var?
 616         */
 617        return is_module_address(addr) || is_module_percpu_address(addr);
 618}
 619
 620/*
 621 * To make lock name printouts unique, we calculate a unique
 622 * class->name_version generation counter:
 623 */
 624static int count_matching_names(struct lock_class *new_class)
 625{
 626        struct lock_class *class;
 627        int count = 0;
 628
 629        if (!new_class->name)
 630                return 0;
 631
 632        list_for_each_entry(class, &all_lock_classes, lock_entry) {
 633                if (new_class->key - new_class->subclass == class->key)
 634                        return class->name_version;
 635                if (class->name && !strcmp(class->name, new_class->name))
 636                        count = max(count, class->name_version);
 637        }
 638
 639        return count + 1;
 640}
 641
 642/*
 643 * Register a lock's class in the hash-table, if the class is not present
 644 * yet. Otherwise we look it up. We cache the result in the lock object
 645 * itself, so actual lookup of the hash should be once per lock object.
 646 */
 647static inline struct lock_class *
 648look_up_lock_class(struct lockdep_map *lock, unsigned int subclass)
 649{
 650        struct lockdep_subclass_key *key;
 651        struct list_head *hash_head;
 652        struct lock_class *class;
 653
 654#ifdef CONFIG_DEBUG_LOCKDEP
 655        /*
 656         * If the architecture calls into lockdep before initializing
 657         * the hashes then we'll warn about it later. (we cannot printk
 658         * right now)
 659         */
 660        if (unlikely(!lockdep_initialized)) {
 661                lockdep_init();
 662                lockdep_init_error = 1;
 663                lock_init_error = lock->name;
 664                save_stack_trace(&lockdep_init_trace);
 665        }
 666#endif
 667
 668        if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
 669                debug_locks_off();
 670                printk(KERN_ERR
 671                        "BUG: looking up invalid subclass: %u\n", subclass);
 672                printk(KERN_ERR
 673                        "turning off the locking correctness validator.\n");
 674                dump_stack();
 675                return NULL;
 676        }
 677
 678        /*
 679         * Static locks do not have their class-keys yet - for them the key
 680         * is the lock object itself:
 681         */
 682        if (unlikely(!lock->key))
 683                lock->key = (void *)lock;
 684
 685        /*
 686         * NOTE: the class-key must be unique. For dynamic locks, a static
 687         * lock_class_key variable is passed in through the mutex_init()
 688         * (or spin_lock_init()) call - which acts as the key. For static
 689         * locks we use the lock object itself as the key.
 690         */
 691        BUILD_BUG_ON(sizeof(struct lock_class_key) >
 692                        sizeof(struct lockdep_map));
 693
 694        key = lock->key->subkeys + subclass;
 695
 696        hash_head = classhashentry(key);
 697
 698        /*
 699         * We can walk the hash lockfree, because the hash only
 700         * grows, and we are careful when adding entries to the end:
 701         */
 702        list_for_each_entry(class, hash_head, hash_entry) {
 703                if (class->key == key) {
 704                        /*
 705                         * Huh! same key, different name? Did someone trample
 706                         * on some memory? We're most confused.
 707                         */
 708                        WARN_ON_ONCE(class->name != lock->name);
 709                        return class;
 710                }
 711        }
 712
 713        return NULL;
 714}
 715
 716/*
 717 * Register a lock's class in the hash-table, if the class is not present
 718 * yet. Otherwise we look it up. We cache the result in the lock object
 719 * itself, so actual lookup of the hash should be once per lock object.
 720 */
 721static inline struct lock_class *
 722register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
 723{
 724        struct lockdep_subclass_key *key;
 725        struct list_head *hash_head;
 726        struct lock_class *class;
 727        unsigned long flags;
 728
 729        class = look_up_lock_class(lock, subclass);
 730        if (likely(class))
 731                goto out_set_class_cache;
 732
 733        /*
 734         * Debug-check: all keys must be persistent!
 735         */
 736        if (!static_obj(lock->key)) {
 737                debug_locks_off();
 738                printk("INFO: trying to register non-static key.\n");
 739                printk("the code is fine but needs lockdep annotation.\n");
 740                printk("turning off the locking correctness validator.\n");
 741                dump_stack();
 742
 743                return NULL;
 744        }
 745
 746        key = lock->key->subkeys + subclass;
 747        hash_head = classhashentry(key);
 748
 749        raw_local_irq_save(flags);
 750        if (!graph_lock()) {
 751                raw_local_irq_restore(flags);
 752                return NULL;
 753        }
 754        /*
 755         * We have to do the hash-walk again, to avoid races
 756         * with another CPU:
 757         */
 758        list_for_each_entry(class, hash_head, hash_entry)
 759                if (class->key == key)
 760                        goto out_unlock_set;
 761        /*
 762         * Allocate a new key from the static array, and add it to
 763         * the hash:
 764         */
 765        if (nr_lock_classes >= MAX_LOCKDEP_KEYS) {
 766                if (!debug_locks_off_graph_unlock()) {
 767                        raw_local_irq_restore(flags);
 768                        return NULL;
 769                }
 770                raw_local_irq_restore(flags);
 771
 772                print_lockdep_off("BUG: MAX_LOCKDEP_KEYS too low!");
 773                dump_stack();
 774                return NULL;
 775        }
 776        class = lock_classes + nr_lock_classes++;
 777        debug_atomic_inc(nr_unused_locks);
 778        class->key = key;
 779        class->name = lock->name;
 780        class->subclass = subclass;
 781        INIT_LIST_HEAD(&class->lock_entry);
 782        INIT_LIST_HEAD(&class->locks_before);
 783        INIT_LIST_HEAD(&class->locks_after);
 784        class->name_version = count_matching_names(class);
 785        /*
 786         * We use RCU's safe list-add method to make
 787         * parallel walking of the hash-list safe:
 788         */
 789        list_add_tail_rcu(&class->hash_entry, hash_head);
 790        /*
 791         * Add it to the global list of classes:
 792         */
 793        list_add_tail_rcu(&class->lock_entry, &all_lock_classes);
 794
 795        if (verbose(class)) {
 796                graph_unlock();
 797                raw_local_irq_restore(flags);
 798
 799                printk("\nnew class %p: %s", class->key, class->name);
 800                if (class->name_version > 1)
 801                        printk("#%d", class->name_version);
 802                printk("\n");
 803                dump_stack();
 804
 805                raw_local_irq_save(flags);
 806                if (!graph_lock()) {
 807                        raw_local_irq_restore(flags);
 808                        return NULL;
 809                }
 810        }
 811out_unlock_set:
 812        graph_unlock();
 813        raw_local_irq_restore(flags);
 814
 815out_set_class_cache:
 816        if (!subclass || force)
 817                lock->class_cache[0] = class;
 818        else if (subclass < NR_LOCKDEP_CACHING_CLASSES)
 819                lock->class_cache[subclass] = class;
 820
 821        /*
 822         * Hash collision, did we smoke some? We found a class with a matching
 823         * hash but the subclass -- which is hashed in -- didn't match.
 824         */
 825        if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))
 826                return NULL;
 827
 828        return class;
 829}
 830
 831#ifdef CONFIG_PROVE_LOCKING
 832/*
 833 * Allocate a lockdep entry. (assumes the graph_lock held, returns
 834 * with NULL on failure)
 835 */
 836static struct lock_list *alloc_list_entry(void)
 837{
 838        if (nr_list_entries >= MAX_LOCKDEP_ENTRIES) {
 839                if (!debug_locks_off_graph_unlock())
 840                        return NULL;
 841
 842                print_lockdep_off("BUG: MAX_LOCKDEP_ENTRIES too low!");
 843                dump_stack();
 844                return NULL;
 845        }
 846        return list_entries + nr_list_entries++;
 847}
 848
 849/*
 850 * Add a new dependency to the head of the list:
 851 */
 852static int add_lock_to_list(struct lock_class *class, struct lock_class *this,
 853                            struct list_head *head, unsigned long ip,
 854                            int distance, struct stack_trace *trace)
 855{
 856        struct lock_list *entry;
 857        /*
 858         * Lock not present yet - get a new dependency struct and
 859         * add it to the list:
 860         */
 861        entry = alloc_list_entry();
 862        if (!entry)
 863                return 0;
 864
 865        entry->class = this;
 866        entry->distance = distance;
 867        entry->trace = *trace;
 868        /*
 869         * Since we never remove from the dependency list, the list can
 870         * be walked lockless by other CPUs, it's only allocation
 871         * that must be protected by the spinlock. But this also means
 872         * we must make new entries visible only once writes to the
 873         * entry become visible - hence the RCU op:
 874         */
 875        list_add_tail_rcu(&entry->entry, head);
 876
 877        return 1;
 878}
 879
 880/*
 881 * For good efficiency of modular, we use power of 2
 882 */
 883#define MAX_CIRCULAR_QUEUE_SIZE         4096UL
 884#define CQ_MASK                         (MAX_CIRCULAR_QUEUE_SIZE-1)
 885
 886/*
 887 * The circular_queue and helpers is used to implement the
 888 * breadth-first search(BFS)algorithem, by which we can build
 889 * the shortest path from the next lock to be acquired to the
 890 * previous held lock if there is a circular between them.
 891 */
 892struct circular_queue {
 893        unsigned long element[MAX_CIRCULAR_QUEUE_SIZE];
 894        unsigned int  front, rear;
 895};
 896
 897static struct circular_queue lock_cq;
 898
 899unsigned int max_bfs_queue_depth;
 900
 901static unsigned int lockdep_dependency_gen_id;
 902
 903static inline void __cq_init(struct circular_queue *cq)
 904{
 905        cq->front = cq->rear = 0;
 906        lockdep_dependency_gen_id++;
 907}
 908
 909static inline int __cq_empty(struct circular_queue *cq)
 910{
 911        return (cq->front == cq->rear);
 912}
 913
 914static inline int __cq_full(struct circular_queue *cq)
 915{
 916        return ((cq->rear + 1) & CQ_MASK) == cq->front;
 917}
 918
 919static inline int __cq_enqueue(struct circular_queue *cq, unsigned long elem)
 920{
 921        if (__cq_full(cq))
 922                return -1;
 923
 924        cq->element[cq->rear] = elem;
 925        cq->rear = (cq->rear + 1) & CQ_MASK;
 926        return 0;
 927}
 928
 929static inline int __cq_dequeue(struct circular_queue *cq, unsigned long *elem)
 930{
 931        if (__cq_empty(cq))
 932                return -1;
 933
 934        *elem = cq->element[cq->front];
 935        cq->front = (cq->front + 1) & CQ_MASK;
 936        return 0;
 937}
 938
 939static inline unsigned int  __cq_get_elem_count(struct circular_queue *cq)
 940{
 941        return (cq->rear - cq->front) & CQ_MASK;
 942}
 943
 944static inline void mark_lock_accessed(struct lock_list *lock,
 945                                        struct lock_list *parent)
 946{
 947        unsigned long nr;
 948
 949        nr = lock - list_entries;
 950        WARN_ON(nr >= nr_list_entries); /* Out-of-bounds, input fail */
 951        lock->parent = parent;
 952        lock->class->dep_gen_id = lockdep_dependency_gen_id;
 953}
 954
 955static inline unsigned long lock_accessed(struct lock_list *lock)
 956{
 957        unsigned long nr;
 958
 959        nr = lock - list_entries;
 960        WARN_ON(nr >= nr_list_entries); /* Out-of-bounds, input fail */
 961        return lock->class->dep_gen_id == lockdep_dependency_gen_id;
 962}
 963
 964static inline struct lock_list *get_lock_parent(struct lock_list *child)
 965{
 966        return child->parent;
 967}
 968
 969static inline int get_lock_depth(struct lock_list *child)
 970{
 971        int depth = 0;
 972        struct lock_list *parent;
 973
 974        while ((parent = get_lock_parent(child))) {
 975                child = parent;
 976                depth++;
 977        }
 978        return depth;
 979}
 980
 981static int __bfs(struct lock_list *source_entry,
 982                 void *data,
 983                 int (*match)(struct lock_list *entry, void *data),
 984                 struct lock_list **target_entry,
 985                 int forward)
 986{
 987        struct lock_list *entry;
 988        struct list_head *head;
 989        struct circular_queue *cq = &lock_cq;
 990        int ret = 1;
 991
 992        if (match(source_entry, data)) {
 993                *target_entry = source_entry;
 994                ret = 0;
 995                goto exit;
 996        }
 997
 998        if (forward)
 999                head = &source_entry->class->locks_after;
1000        else
1001                head = &source_entry->class->locks_before;
1002
1003        if (list_empty(head))
1004                goto exit;
1005
1006        __cq_init(cq);
1007        __cq_enqueue(cq, (unsigned long)source_entry);
1008
1009        while (!__cq_empty(cq)) {
1010                struct lock_list *lock;
1011
1012                __cq_dequeue(cq, (unsigned long *)&lock);
1013
1014                if (!lock->class) {
1015                        ret = -2;
1016                        goto exit;
1017                }
1018
1019                if (forward)
1020                        head = &lock->class->locks_after;
1021                else
1022                        head = &lock->class->locks_before;
1023
1024                list_for_each_entry(entry, head, entry) {
1025                        if (!lock_accessed(entry)) {
1026                                unsigned int cq_depth;
1027                                mark_lock_accessed(entry, lock);
1028                                if (match(entry, data)) {
1029                                        *target_entry = entry;
1030                                        ret = 0;
1031                                        goto exit;
1032                                }
1033
1034                                if (__cq_enqueue(cq, (unsigned long)entry)) {
1035                                        ret = -1;
1036                                        goto exit;
1037                                }
1038                                cq_depth = __cq_get_elem_count(cq);
1039                                if (max_bfs_queue_depth < cq_depth)
1040                                        max_bfs_queue_depth = cq_depth;
1041                        }
1042                }
1043        }
1044exit:
1045        return ret;
1046}
1047
1048static inline int __bfs_forwards(struct lock_list *src_entry,
1049                        void *data,
1050                        int (*match)(struct lock_list *entry, void *data),
1051                        struct lock_list **target_entry)
1052{
1053        return __bfs(src_entry, data, match, target_entry, 1);
1054
1055}
1056
1057static inline int __bfs_backwards(struct lock_list *src_entry,
1058                        void *data,
1059                        int (*match)(struct lock_list *entry, void *data),
1060                        struct lock_list **target_entry)
1061{
1062        return __bfs(src_entry, data, match, target_entry, 0);
1063
1064}
1065
1066/*
1067 * Recursive, forwards-direction lock-dependency checking, used for
1068 * both noncyclic checking and for hardirq-unsafe/softirq-unsafe
1069 * checking.
1070 */
1071
1072/*
1073 * Print a dependency chain entry (this is only done when a deadlock
1074 * has been detected):
1075 */
1076static noinline int
1077print_circular_bug_entry(struct lock_list *target, int depth)
1078{
1079        if (debug_locks_silent)
1080                return 0;
1081        printk("\n-> #%u", depth);
1082        print_lock_name(target->class);
1083        printk(":\n");
1084        print_stack_trace(&target->trace, 6);
1085
1086        return 0;
1087}
1088
1089static void
1090print_circular_lock_scenario(struct held_lock *src,
1091                             struct held_lock *tgt,
1092                             struct lock_list *prt)
1093{
1094        struct lock_class *source = hlock_class(src);
1095        struct lock_class *target = hlock_class(tgt);
1096        struct lock_class *parent = prt->class;
1097
1098        /*
1099         * A direct locking problem where unsafe_class lock is taken
1100         * directly by safe_class lock, then all we need to show
1101         * is the deadlock scenario, as it is obvious that the
1102         * unsafe lock is taken under the safe lock.
1103         *
1104         * But if there is a chain instead, where the safe lock takes
1105         * an intermediate lock (middle_class) where this lock is
1106         * not the same as the safe lock, then the lock chain is
1107         * used to describe the problem. Otherwise we would need
1108         * to show a different CPU case for each link in the chain
1109         * from the safe_class lock to the unsafe_class lock.
1110         */
1111        if (parent != source) {
1112                printk("Chain exists of:\n  ");
1113                __print_lock_name(source);
1114                printk(" --> ");
1115                __print_lock_name(parent);
1116                printk(" --> ");
1117                __print_lock_name(target);
1118                printk("\n\n");
1119        }
1120
1121        printk(" Possible unsafe locking scenario:\n\n");
1122        printk("       CPU0                    CPU1\n");
1123        printk("       ----                    ----\n");
1124        printk("  lock(");
1125        __print_lock_name(target);
1126        printk(");\n");
1127        printk("                               lock(");
1128        __print_lock_name(parent);
1129        printk(");\n");
1130        printk("                               lock(");
1131        __print_lock_name(target);
1132        printk(");\n");
1133        printk("  lock(");
1134        __print_lock_name(source);
1135        printk(");\n");
1136        printk("\n *** DEADLOCK ***\n\n");
1137}
1138
1139/*
1140 * When a circular dependency is detected, print the
1141 * header first:
1142 */
1143static noinline int
1144print_circular_bug_header(struct lock_list *entry, unsigned int depth,
1145                        struct held_lock *check_src,
1146                        struct held_lock *check_tgt)
1147{
1148        struct task_struct *curr = current;
1149
1150        if (debug_locks_silent)
1151                return 0;
1152
1153        printk("\n");
1154        printk("======================================================\n");
1155        printk("[ INFO: possible circular locking dependency detected ]\n");
1156        print_kernel_ident();
1157        printk("-------------------------------------------------------\n");
1158        printk("%s/%d is trying to acquire lock:\n",
1159                curr->comm, task_pid_nr(curr));
1160        print_lock(check_src);
1161        printk("\nbut task is already holding lock:\n");
1162        print_lock(check_tgt);
1163        printk("\nwhich lock already depends on the new lock.\n\n");
1164        printk("\nthe existing dependency chain (in reverse order) is:\n");
1165
1166        print_circular_bug_entry(entry, depth);
1167
1168        return 0;
1169}
1170
1171static inline int class_equal(struct lock_list *entry, void *data)
1172{
1173        return entry->class == data;
1174}
1175
1176static noinline int print_circular_bug(struct lock_list *this,
1177                                struct lock_list *target,
1178                                struct held_lock *check_src,
1179                                struct held_lock *check_tgt)
1180{
1181        struct task_struct *curr = current;
1182        struct lock_list *parent;
1183        struct lock_list *first_parent;
1184        int depth;
1185
1186        if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1187                return 0;
1188
1189        if (!save_trace(&this->trace))
1190                return 0;
1191
1192        depth = get_lock_depth(target);
1193
1194        print_circular_bug_header(target, depth, check_src, check_tgt);
1195
1196        parent = get_lock_parent(target);
1197        first_parent = parent;
1198
1199        while (parent) {
1200                print_circular_bug_entry(parent, --depth);
1201                parent = get_lock_parent(parent);
1202        }
1203
1204        printk("\nother info that might help us debug this:\n\n");
1205        print_circular_lock_scenario(check_src, check_tgt,
1206                                     first_parent);
1207
1208        lockdep_print_held_locks(curr);
1209
1210        printk("\nstack backtrace:\n");
1211        dump_stack();
1212
1213        return 0;
1214}
1215
1216static noinline int print_bfs_bug(int ret)
1217{
1218        if (!debug_locks_off_graph_unlock())
1219                return 0;
1220
1221        /*
1222         * Breadth-first-search failed, graph got corrupted?
1223         */
1224        WARN(1, "lockdep bfs error:%d\n", ret);
1225
1226        return 0;
1227}
1228
1229static int noop_count(struct lock_list *entry, void *data)
1230{
1231        (*(unsigned long *)data)++;
1232        return 0;
1233}
1234
1235unsigned long __lockdep_count_forward_deps(struct lock_list *this)
1236{
1237        unsigned long  count = 0;
1238        struct lock_list *uninitialized_var(target_entry);
1239
1240        __bfs_forwards(this, (void *)&count, noop_count, &target_entry);
1241
1242        return count;
1243}
1244unsigned long lockdep_count_forward_deps(struct lock_class *class)
1245{
1246        unsigned long ret, flags;
1247        struct lock_list this;
1248
1249        this.parent = NULL;
1250        this.class = class;
1251
1252        local_irq_save(flags);
1253        arch_spin_lock(&lockdep_lock);
1254        ret = __lockdep_count_forward_deps(&this);
1255        arch_spin_unlock(&lockdep_lock);
1256        local_irq_restore(flags);
1257
1258        return ret;
1259}
1260
1261unsigned long __lockdep_count_backward_deps(struct lock_list *this)
1262{
1263        unsigned long  count = 0;
1264        struct lock_list *uninitialized_var(target_entry);
1265
1266        __bfs_backwards(this, (void *)&count, noop_count, &target_entry);
1267
1268        return count;
1269}
1270
1271unsigned long lockdep_count_backward_deps(struct lock_class *class)
1272{
1273        unsigned long ret, flags;
1274        struct lock_list this;
1275
1276        this.parent = NULL;
1277        this.class = class;
1278
1279        local_irq_save(flags);
1280        arch_spin_lock(&lockdep_lock);
1281        ret = __lockdep_count_backward_deps(&this);
1282        arch_spin_unlock(&lockdep_lock);
1283        local_irq_restore(flags);
1284
1285        return ret;
1286}
1287
1288/*
1289 * Prove that the dependency graph starting at <entry> can not
1290 * lead to <target>. Print an error and return 0 if it does.
1291 */
1292static noinline int
1293check_noncircular(struct lock_list *root, struct lock_class *target,
1294                struct lock_list **target_entry)
1295{
1296        int result;
1297
1298        debug_atomic_inc(nr_cyclic_checks);
1299
1300        result = __bfs_forwards(root, target, class_equal, target_entry);
1301
1302        return result;
1303}
1304
1305#if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
1306/*
1307 * Forwards and backwards subgraph searching, for the purposes of
1308 * proving that two subgraphs can be connected by a new dependency
1309 * without creating any illegal irq-safe -> irq-unsafe lock dependency.
1310 */
1311
1312static inline int usage_match(struct lock_list *entry, void *bit)
1313{
1314        return entry->class->usage_mask & (1 << (enum lock_usage_bit)bit);
1315}
1316
1317
1318
1319/*
1320 * Find a node in the forwards-direction dependency sub-graph starting
1321 * at @root->class that matches @bit.
1322 *
1323 * Return 0 if such a node exists in the subgraph, and put that node
1324 * into *@target_entry.
1325 *
1326 * Return 1 otherwise and keep *@target_entry unchanged.
1327 * Return <0 on error.
1328 */
1329static int
1330find_usage_forwards(struct lock_list *root, enum lock_usage_bit bit,
1331                        struct lock_list **target_entry)
1332{
1333        int result;
1334
1335        debug_atomic_inc(nr_find_usage_forwards_checks);
1336
1337        result = __bfs_forwards(root, (void *)bit, usage_match, target_entry);
1338
1339        return result;
1340}
1341
1342/*
1343 * Find a node in the backwards-direction dependency sub-graph starting
1344 * at @root->class that matches @bit.
1345 *
1346 * Return 0 if such a node exists in the subgraph, and put that node
1347 * into *@target_entry.
1348 *
1349 * Return 1 otherwise and keep *@target_entry unchanged.
1350 * Return <0 on error.
1351 */
1352static int
1353find_usage_backwards(struct lock_list *root, enum lock_usage_bit bit,
1354                        struct lock_list **target_entry)
1355{
1356        int result;
1357
1358        debug_atomic_inc(nr_find_usage_backwards_checks);
1359
1360        result = __bfs_backwards(root, (void *)bit, usage_match, target_entry);
1361
1362        return result;
1363}
1364
1365static void print_lock_class_header(struct lock_class *class, int depth)
1366{
1367        int bit;
1368
1369        printk("%*s->", depth, "");
1370        print_lock_name(class);
1371        printk(" ops: %lu", class->ops);
1372        printk(" {\n");
1373
1374        for (bit = 0; bit < LOCK_USAGE_STATES; bit++) {
1375                if (class->usage_mask & (1 << bit)) {
1376                        int len = depth;
1377
1378                        len += printk("%*s   %s", depth, "", usage_str[bit]);
1379                        len += printk(" at:\n");
1380                        print_stack_trace(class->usage_traces + bit, len);
1381                }
1382        }
1383        printk("%*s }\n", depth, "");
1384
1385        printk("%*s ... key      at: ",depth,"");
1386        print_ip_sym((unsigned long)class->key);
1387}
1388
1389/*
1390 * printk the shortest lock dependencies from @start to @end in reverse order:
1391 */
1392static void __used
1393print_shortest_lock_dependencies(struct lock_list *leaf,
1394                                struct lock_list *root)
1395{
1396        struct lock_list *entry = leaf;
1397        int depth;
1398
1399        /*compute depth from generated tree by BFS*/
1400        depth = get_lock_depth(leaf);
1401
1402        do {
1403                print_lock_class_header(entry->class, depth);
1404                printk("%*s ... acquired at:\n", depth, "");
1405                print_stack_trace(&entry->trace, 2);
1406                printk("\n");
1407
1408                if (depth == 0 && (entry != root)) {
1409                        printk("lockdep:%s bad path found in chain graph\n", __func__);
1410                        break;
1411                }
1412
1413                entry = get_lock_parent(entry);
1414                depth--;
1415        } while (entry && (depth >= 0));
1416
1417        return;
1418}
1419
1420static void
1421print_irq_lock_scenario(struct lock_list *safe_entry,
1422                        struct lock_list *unsafe_entry,
1423                        struct lock_class *prev_class,
1424                        struct lock_class *next_class)
1425{
1426        struct lock_class *safe_class = safe_entry->class;
1427        struct lock_class *unsafe_class = unsafe_entry->class;
1428        struct lock_class *middle_class = prev_class;
1429
1430        if (middle_class == safe_class)
1431                middle_class = next_class;
1432
1433        /*
1434         * A direct locking problem where unsafe_class lock is taken
1435         * directly by safe_class lock, then all we need to show
1436         * is the deadlock scenario, as it is obvious that the
1437         * unsafe lock is taken under the safe lock.
1438         *
1439         * But if there is a chain instead, where the safe lock takes
1440         * an intermediate lock (middle_class) where this lock is
1441         * not the same as the safe lock, then the lock chain is
1442         * used to describe the problem. Otherwise we would need
1443         * to show a different CPU case for each link in the chain
1444         * from the safe_class lock to the unsafe_class lock.
1445         */
1446        if (middle_class != unsafe_class) {
1447                printk("Chain exists of:\n  ");
1448                __print_lock_name(safe_class);
1449                printk(" --> ");
1450                __print_lock_name(middle_class);
1451                printk(" --> ");
1452                __print_lock_name(unsafe_class);
1453                printk("\n\n");
1454        }
1455
1456        printk(" Possible interrupt unsafe locking scenario:\n\n");
1457        printk("       CPU0                    CPU1\n");
1458        printk("       ----                    ----\n");
1459        printk("  lock(");
1460        __print_lock_name(unsafe_class);
1461        printk(");\n");
1462        printk("                               local_irq_disable();\n");
1463        printk("                               lock(");
1464        __print_lock_name(safe_class);
1465        printk(");\n");
1466        printk("                               lock(");
1467        __print_lock_name(middle_class);
1468        printk(");\n");
1469        printk("  <Interrupt>\n");
1470        printk("    lock(");
1471        __print_lock_name(safe_class);
1472        printk(");\n");
1473        printk("\n *** DEADLOCK ***\n\n");
1474}
1475
1476static int
1477print_bad_irq_dependency(struct task_struct *curr,
1478                         struct lock_list *prev_root,
1479                         struct lock_list *next_root,
1480                         struct lock_list *backwards_entry,
1481                         struct lock_list *forwards_entry,
1482                         struct held_lock *prev,
1483                         struct held_lock *next,
1484                         enum lock_usage_bit bit1,
1485                         enum lock_usage_bit bit2,
1486                         const char *irqclass)
1487{
1488        if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1489                return 0;
1490
1491        printk("\n");
1492        printk("======================================================\n");
1493        printk("[ INFO: %s-safe -> %s-unsafe lock order detected ]\n",
1494                irqclass, irqclass);
1495        print_kernel_ident();
1496        printk("------------------------------------------------------\n");
1497        printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
1498                curr->comm, task_pid_nr(curr),
1499                curr->hardirq_context, hardirq_count() >> HARDIRQ_SHIFT,
1500                curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT,
1501                curr->hardirqs_enabled,
1502                curr->softirqs_enabled);
1503        print_lock(next);
1504
1505        printk("\nand this task is already holding:\n");
1506        print_lock(prev);
1507        printk("which would create a new lock dependency:\n");
1508        print_lock_name(hlock_class(prev));
1509        printk(" ->");
1510        print_lock_name(hlock_class(next));
1511        printk("\n");
1512
1513        printk("\nbut this new dependency connects a %s-irq-safe lock:\n",
1514                irqclass);
1515        print_lock_name(backwards_entry->class);
1516        printk("\n... which became %s-irq-safe at:\n", irqclass);
1517
1518        print_stack_trace(backwards_entry->class->usage_traces + bit1, 1);
1519
1520        printk("\nto a %s-irq-unsafe lock:\n", irqclass);
1521        print_lock_name(forwards_entry->class);
1522        printk("\n... which became %s-irq-unsafe at:\n", irqclass);
1523        printk("...");
1524
1525        print_stack_trace(forwards_entry->class->usage_traces + bit2, 1);
1526
1527        printk("\nother info that might help us debug this:\n\n");
1528        print_irq_lock_scenario(backwards_entry, forwards_entry,
1529                                hlock_class(prev), hlock_class(next));
1530
1531        lockdep_print_held_locks(curr);
1532
1533        printk("\nthe dependencies between %s-irq-safe lock", irqclass);
1534        printk(" and the holding lock:\n");
1535        if (!save_trace(&prev_root->trace))
1536                return 0;
1537        print_shortest_lock_dependencies(backwards_entry, prev_root);
1538
1539        printk("\nthe dependencies between the lock to be acquired");
1540        printk(" and %s-irq-unsafe lock:\n", irqclass);
1541        if (!save_trace(&next_root->trace))
1542                return 0;
1543        print_shortest_lock_dependencies(forwards_entry, next_root);
1544
1545        printk("\nstack backtrace:\n");
1546        dump_stack();
1547
1548        return 0;
1549}
1550
1551static int
1552check_usage(struct task_struct *curr, struct held_lock *prev,
1553            struct held_lock *next, enum lock_usage_bit bit_backwards,
1554            enum lock_usage_bit bit_forwards, const char *irqclass)
1555{
1556        int ret;
1557        struct lock_list this, that;
1558        struct lock_list *uninitialized_var(target_entry);
1559        struct lock_list *uninitialized_var(target_entry1);
1560
1561        this.parent = NULL;
1562
1563        this.class = hlock_class(prev);
1564        ret = find_usage_backwards(&this, bit_backwards, &target_entry);
1565        if (ret < 0)
1566                return print_bfs_bug(ret);
1567        if (ret == 1)
1568                return ret;
1569
1570        that.parent = NULL;
1571        that.class = hlock_class(next);
1572        ret = find_usage_forwards(&that, bit_forwards, &target_entry1);
1573        if (ret < 0)
1574                return print_bfs_bug(ret);
1575        if (ret == 1)
1576                return ret;
1577
1578        return print_bad_irq_dependency(curr, &this, &that,
1579                        target_entry, target_entry1,
1580                        prev, next,
1581                        bit_backwards, bit_forwards, irqclass);
1582}
1583
1584static const char *state_names[] = {
1585#define LOCKDEP_STATE(__STATE) \
1586        __stringify(__STATE),
1587#include "lockdep_states.h"
1588#undef LOCKDEP_STATE
1589};
1590
1591static const char *state_rnames[] = {
1592#define LOCKDEP_STATE(__STATE) \
1593        __stringify(__STATE)"-READ",
1594#include "lockdep_states.h"
1595#undef LOCKDEP_STATE
1596};
1597
1598static inline const char *state_name(enum lock_usage_bit bit)
1599{
1600        return (bit & 1) ? state_rnames[bit >> 2] : state_names[bit >> 2];
1601}
1602
1603static int exclusive_bit(int new_bit)
1604{
1605        /*
1606         * USED_IN
1607         * USED_IN_READ
1608         * ENABLED
1609         * ENABLED_READ
1610         *
1611         * bit 0 - write/read
1612         * bit 1 - used_in/enabled
1613         * bit 2+  state
1614         */
1615
1616        int state = new_bit & ~3;
1617        int dir = new_bit & 2;
1618
1619        /*
1620         * keep state, bit flip the direction and strip read.
1621         */
1622        return state | (dir ^ 2);
1623}
1624
1625static int check_irq_usage(struct task_struct *curr, struct held_lock *prev,
1626                           struct held_lock *next, enum lock_usage_bit bit)
1627{
1628        /*
1629         * Prove that the new dependency does not connect a hardirq-safe
1630         * lock with a hardirq-unsafe lock - to achieve this we search
1631         * the backwards-subgraph starting at <prev>, and the
1632         * forwards-subgraph starting at <next>:
1633         */
1634        if (!check_usage(curr, prev, next, bit,
1635                           exclusive_bit(bit), state_name(bit)))
1636                return 0;
1637
1638        bit++; /* _READ */
1639
1640        /*
1641         * Prove that the new dependency does not connect a hardirq-safe-read
1642         * lock with a hardirq-unsafe lock - to achieve this we search
1643         * the backwards-subgraph starting at <prev>, and the
1644         * forwards-subgraph starting at <next>:
1645         */
1646        if (!check_usage(curr, prev, next, bit,
1647                           exclusive_bit(bit), state_name(bit)))
1648                return 0;
1649
1650        return 1;
1651}
1652
1653static int
1654check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
1655                struct held_lock *next)
1656{
1657#define LOCKDEP_STATE(__STATE)                                          \
1658        if (!check_irq_usage(curr, prev, next, LOCK_USED_IN_##__STATE)) \
1659                return 0;
1660#include "lockdep_states.h"
1661#undef LOCKDEP_STATE
1662
1663        return 1;
1664}
1665
1666static void inc_chains(void)
1667{
1668        if (current->hardirq_context)
1669                nr_hardirq_chains++;
1670        else {
1671                if (current->softirq_context)
1672                        nr_softirq_chains++;
1673                else
1674                        nr_process_chains++;
1675        }
1676}
1677
1678#else
1679
1680static inline int
1681check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
1682                struct held_lock *next)
1683{
1684        return 1;
1685}
1686
1687static inline void inc_chains(void)
1688{
1689        nr_process_chains++;
1690}
1691
1692#endif
1693
1694static void
1695print_deadlock_scenario(struct held_lock *nxt,
1696                             struct held_lock *prv)
1697{
1698        struct lock_class *next = hlock_class(nxt);
1699        struct lock_class *prev = hlock_class(prv);
1700
1701        printk(" Possible unsafe locking scenario:\n\n");
1702        printk("       CPU0\n");
1703        printk("       ----\n");
1704        printk("  lock(");
1705        __print_lock_name(prev);
1706        printk(");\n");
1707        printk("  lock(");
1708        __print_lock_name(next);
1709        printk(");\n");
1710        printk("\n *** DEADLOCK ***\n\n");
1711        printk(" May be due to missing lock nesting notation\n\n");
1712}
1713
1714static int
1715print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
1716                   struct held_lock *next)
1717{
1718        if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1719                return 0;
1720
1721        printk("\n");
1722        printk("=============================================\n");
1723        printk("[ INFO: possible recursive locking detected ]\n");
1724        print_kernel_ident();
1725        printk("---------------------------------------------\n");
1726        printk("%s/%d is trying to acquire lock:\n",
1727                curr->comm, task_pid_nr(curr));
1728        print_lock(next);
1729        printk("\nbut task is already holding lock:\n");
1730        print_lock(prev);
1731
1732        printk("\nother info that might help us debug this:\n");
1733        print_deadlock_scenario(next, prev);
1734        lockdep_print_held_locks(curr);
1735
1736        printk("\nstack backtrace:\n");
1737        dump_stack();
1738
1739        return 0;
1740}
1741
1742/*
1743 * Check whether we are holding such a class already.
1744 *
1745 * (Note that this has to be done separately, because the graph cannot
1746 * detect such classes of deadlocks.)
1747 *
1748 * Returns: 0 on deadlock detected, 1 on OK, 2 on recursive read
1749 */
1750static int
1751check_deadlock(struct task_struct *curr, struct held_lock *next,
1752               struct lockdep_map *next_instance, int read)
1753{
1754        struct held_lock *prev;
1755        struct held_lock *nest = NULL;
1756        int i;
1757
1758        for (i = 0; i < curr->lockdep_depth; i++) {
1759                prev = curr->held_locks + i;
1760
1761                if (prev->instance == next->nest_lock)
1762                        nest = prev;
1763
1764                if (hlock_class(prev) != hlock_class(next))
1765                        continue;
1766
1767                /*
1768                 * Allow read-after-read recursion of the same
1769                 * lock class (i.e. read_lock(lock)+read_lock(lock)):
1770                 */
1771                if ((read == 2) && prev->read)
1772                        return 2;
1773
1774                /*
1775                 * We're holding the nest_lock, which serializes this lock's
1776                 * nesting behaviour.
1777                 */
1778                if (nest)
1779                        return 2;
1780
1781                return print_deadlock_bug(curr, prev, next);
1782        }
1783        return 1;
1784}
1785
1786/*
1787 * There was a chain-cache miss, and we are about to add a new dependency
1788 * to a previous lock. We recursively validate the following rules:
1789 *
1790 *  - would the adding of the <prev> -> <next> dependency create a
1791 *    circular dependency in the graph? [== circular deadlock]
1792 *
1793 *  - does the new prev->next dependency connect any hardirq-safe lock
1794 *    (in the full backwards-subgraph starting at <prev>) with any
1795 *    hardirq-unsafe lock (in the full forwards-subgraph starting at
1796 *    <next>)? [== illegal lock inversion with hardirq contexts]
1797 *
1798 *  - does the new prev->next dependency connect any softirq-safe lock
1799 *    (in the full backwards-subgraph starting at <prev>) with any
1800 *    softirq-unsafe lock (in the full forwards-subgraph starting at
1801 *    <next>)? [== illegal lock inversion with softirq contexts]
1802 *
1803 * any of these scenarios could lead to a deadlock.
1804 *
1805 * Then if all the validations pass, we add the forwards and backwards
1806 * dependency.
1807 */
1808static int
1809check_prev_add(struct task_struct *curr, struct held_lock *prev,
1810               struct held_lock *next, int distance, int trylock_loop)
1811{
1812        struct lock_list *entry;
1813        int ret;
1814        struct lock_list this;
1815        struct lock_list *uninitialized_var(target_entry);
1816        /*
1817         * Static variable, serialized by the graph_lock().
1818         *
1819         * We use this static variable to save the stack trace in case
1820         * we call into this function multiple times due to encountering
1821         * trylocks in the held lock stack.
1822         */
1823        static struct stack_trace trace;
1824
1825        /*
1826         * Prove that the new <prev> -> <next> dependency would not
1827         * create a circular dependency in the graph. (We do this by
1828         * forward-recursing into the graph starting at <next>, and
1829         * checking whether we can reach <prev>.)
1830         *
1831         * We are using global variables to control the recursion, to
1832         * keep the stackframe size of the recursive functions low:
1833         */
1834        this.class = hlock_class(next);
1835        this.parent = NULL;
1836        ret = check_noncircular(&this, hlock_class(prev), &target_entry);
1837        if (unlikely(!ret))
1838                return print_circular_bug(&this, target_entry, next, prev);
1839        else if (unlikely(ret < 0))
1840                return print_bfs_bug(ret);
1841
1842        if (!check_prev_add_irq(curr, prev, next))
1843                return 0;
1844
1845        /*
1846         * For recursive read-locks we do all the dependency checks,
1847         * but we dont store read-triggered dependencies (only
1848         * write-triggered dependencies). This ensures that only the
1849         * write-side dependencies matter, and that if for example a
1850         * write-lock never takes any other locks, then the reads are
1851         * equivalent to a NOP.
1852         */
1853        if (next->read == 2 || prev->read == 2)
1854                return 1;
1855        /*
1856         * Is the <prev> -> <next> dependency already present?
1857         *
1858         * (this may occur even though this is a new chain: consider
1859         *  e.g. the L1 -> L2 -> L3 -> L4 and the L5 -> L1 -> L2 -> L3
1860         *  chains - the second one will be new, but L1 already has
1861         *  L2 added to its dependency list, due to the first chain.)
1862         */
1863        list_for_each_entry(entry, &hlock_class(prev)->locks_after, entry) {
1864                if (entry->class == hlock_class(next)) {
1865                        if (distance == 1)
1866                                entry->distance = 1;
1867                        return 2;
1868                }
1869        }
1870
1871        if (!trylock_loop && !save_trace(&trace))
1872                return 0;
1873
1874        /*
1875         * Ok, all validations passed, add the new lock
1876         * to the previous lock's dependency list:
1877         */
1878        ret = add_lock_to_list(hlock_class(prev), hlock_class(next),
1879                               &hlock_class(prev)->locks_after,
1880                               next->acquire_ip, distance, &trace);
1881
1882        if (!ret)
1883                return 0;
1884
1885        ret = add_lock_to_list(hlock_class(next), hlock_class(prev),
1886                               &hlock_class(next)->locks_before,
1887                               next->acquire_ip, distance, &trace);
1888        if (!ret)
1889                return 0;
1890
1891        /*
1892         * Debugging printouts:
1893         */
1894        if (verbose(hlock_class(prev)) || verbose(hlock_class(next))) {
1895                graph_unlock();
1896                printk("\n new dependency: ");
1897                print_lock_name(hlock_class(prev));
1898                printk(" => ");
1899                print_lock_name(hlock_class(next));
1900                printk("\n");
1901                dump_stack();
1902                return graph_lock();
1903        }
1904        return 1;
1905}
1906
1907/*
1908 * Add the dependency to all directly-previous locks that are 'relevant'.
1909 * The ones that are relevant are (in increasing distance from curr):
1910 * all consecutive trylock entries and the final non-trylock entry - or
1911 * the end of this context's lock-chain - whichever comes first.
1912 */
1913static int
1914check_prevs_add(struct task_struct *curr, struct held_lock *next)
1915{
1916        int depth = curr->lockdep_depth;
1917        int trylock_loop = 0;
1918        struct held_lock *hlock;
1919
1920        /*
1921         * Debugging checks.
1922         *
1923         * Depth must not be zero for a non-head lock:
1924         */
1925        if (!depth)
1926                goto out_bug;
1927        /*
1928         * At least two relevant locks must exist for this
1929         * to be a head:
1930         */
1931        if (curr->held_locks[depth].irq_context !=
1932                        curr->held_locks[depth-1].irq_context)
1933                goto out_bug;
1934
1935        for (;;) {
1936                int distance = curr->lockdep_depth - depth + 1;
1937                hlock = curr->held_locks + depth-1;
1938                /*
1939                 * Only non-recursive-read entries get new dependencies
1940                 * added:
1941                 */
1942                if (hlock->read != 2) {
1943                        if (!check_prev_add(curr, hlock, next,
1944                                                distance, trylock_loop))
1945                                return 0;
1946                        /*
1947                         * Stop after the first non-trylock entry,
1948                         * as non-trylock entries have added their
1949                         * own direct dependencies already, so this
1950                         * lock is connected to them indirectly:
1951                         */
1952                        if (!hlock->trylock)
1953                                break;
1954                }
1955                depth--;
1956                /*
1957                 * End of lock-stack?
1958                 */
1959                if (!depth)
1960                        break;
1961                /*
1962                 * Stop the search if we cross into another context:
1963                 */
1964                if (curr->held_locks[depth].irq_context !=
1965                                curr->held_locks[depth-1].irq_context)
1966                        break;
1967                trylock_loop = 1;
1968        }
1969        return 1;
1970out_bug:
1971        if (!debug_locks_off_graph_unlock())
1972                return 0;
1973
1974        /*
1975         * Clearly we all shouldn't be here, but since we made it we
1976         * can reliable say we messed up our state. See the above two
1977         * gotos for reasons why we could possibly end up here.
1978         */
1979        WARN_ON(1);
1980
1981        return 0;
1982}
1983
1984unsigned long nr_lock_chains;
1985struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
1986int nr_chain_hlocks;
1987static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
1988
1989struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
1990{
1991        return lock_classes + chain_hlocks[chain->base + i];
1992}
1993
1994/*
1995 * Look up a dependency chain. If the key is not present yet then
1996 * add it and return 1 - in this case the new dependency chain is
1997 * validated. If the key is already hashed, return 0.
1998 * (On return with 1 graph_lock is held.)
1999 */
2000static inline int lookup_chain_cache(struct task_struct *curr,
2001                                     struct held_lock *hlock,
2002                                     u64 chain_key)
2003{
2004        struct lock_class *class = hlock_class(hlock);
2005        struct list_head *hash_head = chainhashentry(chain_key);
2006        struct lock_chain *chain;
2007        struct held_lock *hlock_curr;
2008        int i, j;
2009
2010        /*
2011         * We might need to take the graph lock, ensure we've got IRQs
2012         * disabled to make this an IRQ-safe lock.. for recursion reasons
2013         * lockdep won't complain about its own locking errors.
2014         */
2015        if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2016                return 0;
2017        /*
2018         * We can walk it lock-free, because entries only get added
2019         * to the hash:
2020         */
2021        list_for_each_entry(chain, hash_head, entry) {
2022                if (chain->chain_key == chain_key) {
2023cache_hit:
2024                        debug_atomic_inc(chain_lookup_hits);
2025                        if (very_verbose(class))
2026                                printk("\nhash chain already cached, key: "
2027                                        "%016Lx tail class: [%p] %s\n",
2028                                        (unsigned long long)chain_key,
2029                                        class->key, class->name);
2030                        return 0;
2031                }
2032        }
2033        if (very_verbose(class))
2034                printk("\nnew hash chain, key: %016Lx tail class: [%p] %s\n",
2035                        (unsigned long long)chain_key, class->key, class->name);
2036        /*
2037         * Allocate a new chain entry from the static array, and add
2038         * it to the hash:
2039         */
2040        if (!graph_lock())
2041                return 0;
2042        /*
2043         * We have to walk the chain again locked - to avoid duplicates:
2044         */
2045        list_for_each_entry(chain, hash_head, entry) {
2046                if (chain->chain_key == chain_key) {
2047                        graph_unlock();
2048                        goto cache_hit;
2049                }
2050        }
2051        if (unlikely(nr_lock_chains >= MAX_LOCKDEP_CHAINS)) {
2052                if (!debug_locks_off_graph_unlock())
2053                        return 0;
2054
2055                print_lockdep_off("BUG: MAX_LOCKDEP_CHAINS too low!");
2056                dump_stack();
2057                return 0;
2058        }
2059        chain = lock_chains + nr_lock_chains++;
2060        chain->chain_key = chain_key;
2061        chain->irq_context = hlock->irq_context;
2062        /* Find the first held_lock of current chain */
2063        for (i = curr->lockdep_depth - 1; i >= 0; i--) {
2064                hlock_curr = curr->held_locks + i;
2065                if (hlock_curr->irq_context != hlock->irq_context)
2066                        break;
2067        }
2068        i++;
2069        chain->depth = curr->lockdep_depth + 1 - i;
2070        if (likely(nr_chain_hlocks + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) {
2071                chain->base = nr_chain_hlocks;
2072                nr_chain_hlocks += chain->depth;
2073                for (j = 0; j < chain->depth - 1; j++, i++) {
2074                        int lock_id = curr->held_locks[i].class_idx - 1;
2075                        chain_hlocks[chain->base + j] = lock_id;
2076                }
2077                chain_hlocks[chain->base + j] = class - lock_classes;
2078        }
2079        list_add_tail_rcu(&chain->entry, hash_head);
2080        debug_atomic_inc(chain_lookup_misses);
2081        inc_chains();
2082
2083        return 1;
2084}
2085
2086static int validate_chain(struct task_struct *curr, struct lockdep_map *lock,
2087                struct held_lock *hlock, int chain_head, u64 chain_key)
2088{
2089        /*
2090         * Trylock needs to maintain the stack of held locks, but it
2091         * does not add new dependencies, because trylock can be done
2092         * in any order.
2093         *
2094         * We look up the chain_key and do the O(N^2) check and update of
2095         * the dependencies only if this is a new dependency chain.
2096         * (If lookup_chain_cache() returns with 1 it acquires
2097         * graph_lock for us)
2098         */
2099        if (!hlock->trylock && (hlock->check == 2) &&
2100            lookup_chain_cache(curr, hlock, chain_key)) {
2101                /*
2102                 * Check whether last held lock:
2103                 *
2104                 * - is irq-safe, if this lock is irq-unsafe
2105                 * - is softirq-safe, if this lock is hardirq-unsafe
2106                 *
2107                 * And check whether the new lock's dependency graph
2108                 * could lead back to the previous lock.
2109                 *
2110                 * any of these scenarios could lead to a deadlock. If
2111                 * All validations
2112                 */
2113                int ret = check_deadlock(curr, hlock, lock, hlock->read);
2114
2115                if (!ret)
2116                        return 0;
2117                /*
2118                 * Mark recursive read, as we jump over it when
2119                 * building dependencies (just like we jump over
2120                 * trylock entries):
2121                 */
2122                if (ret == 2)
2123                        hlock->read = 2;
2124                /*
2125                 * Add dependency only if this lock is not the head
2126                 * of the chain, and if it's not a secondary read-lock:
2127                 */
2128                if (!chain_head && ret != 2)
2129                        if (!check_prevs_add(curr, hlock))
2130                                return 0;
2131                graph_unlock();
2132        } else
2133                /* after lookup_chain_cache(): */
2134                if (unlikely(!debug_locks))
2135                        return 0;
2136
2137        return 1;
2138}
2139#else
2140static inline int validate_chain(struct task_struct *curr,
2141                struct lockdep_map *lock, struct held_lock *hlock,
2142                int chain_head, u64 chain_key)
2143{
2144        return 1;
2145}
2146#endif
2147
2148/*
2149 * We are building curr_chain_key incrementally, so double-check
2150 * it from scratch, to make sure that it's done correctly:
2151 */
2152static void check_chain_key(struct task_struct *curr)
2153{
2154#ifdef CONFIG_DEBUG_LOCKDEP
2155        struct held_lock *hlock, *prev_hlock = NULL;
2156        unsigned int i, id;
2157        u64 chain_key = 0;
2158
2159        for (i = 0; i < curr->lockdep_depth; i++) {
2160                hlock = curr->held_locks + i;
2161                if (chain_key != hlock->prev_chain_key) {
2162                        debug_locks_off();
2163                        /*
2164                         * We got mighty confused, our chain keys don't match
2165                         * with what we expect, someone trample on our task state?
2166                         */
2167                        WARN(1, "hm#1, depth: %u [%u], %016Lx != %016Lx\n",
2168                                curr->lockdep_depth, i,
2169                                (unsigned long long)chain_key,
2170                                (unsigned long long)hlock->prev_chain_key);
2171                        return;
2172                }
2173                id = hlock->class_idx - 1;
2174                /*
2175                 * Whoops ran out of static storage again?
2176                 */
2177                if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
2178                        return;
2179
2180                if (prev_hlock && (prev_hlock->irq_context !=
2181                                                        hlock->irq_context))
2182                        chain_key = 0;
2183                chain_key = iterate_chain_key(chain_key, id);
2184                prev_hlock = hlock;
2185        }
2186        if (chain_key != curr->curr_chain_key) {
2187                debug_locks_off();
2188                /*
2189                 * More smoking hash instead of calculating it, damn see these
2190                 * numbers float.. I bet that a pink elephant stepped on my memory.
2191                 */
2192                WARN(1, "hm#2, depth: %u [%u], %016Lx != %016Lx\n",
2193                        curr->lockdep_depth, i,
2194                        (unsigned long long)chain_key,
2195                        (unsigned long long)curr->curr_chain_key);
2196        }
2197#endif
2198}
2199
2200static void
2201print_usage_bug_scenario(struct held_lock *lock)
2202{
2203        struct lock_class *class = hlock_class(lock);
2204
2205        printk(" Possible unsafe locking scenario:\n\n");
2206        printk("       CPU0\n");
2207        printk("       ----\n");
2208        printk("  lock(");
2209        __print_lock_name(class);
2210        printk(");\n");
2211        printk("  <Interrupt>\n");
2212        printk("    lock(");
2213        __print_lock_name(class);
2214        printk(");\n");
2215        printk("\n *** DEADLOCK ***\n\n");
2216}
2217
2218static int
2219print_usage_bug(struct task_struct *curr, struct held_lock *this,
2220                enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
2221{
2222        if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2223                return 0;
2224
2225        printk("\n");
2226        printk("=================================\n");
2227        printk("[ INFO: inconsistent lock state ]\n");
2228        print_kernel_ident();
2229        printk("---------------------------------\n");
2230
2231        printk("inconsistent {%s} -> {%s} usage.\n",
2232                usage_str[prev_bit], usage_str[new_bit]);
2233
2234        printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] takes:\n",
2235                curr->comm, task_pid_nr(curr),
2236                trace_hardirq_context(curr), hardirq_count() >> HARDIRQ_SHIFT,
2237                trace_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT,
2238                trace_hardirqs_enabled(curr),
2239                trace_softirqs_enabled(curr));
2240        print_lock(this);
2241
2242        printk("{%s} state was registered at:\n", usage_str[prev_bit]);
2243        print_stack_trace(hlock_class(this)->usage_traces + prev_bit, 1);
2244
2245        print_irqtrace_events(curr);
2246        printk("\nother info that might help us debug this:\n");
2247        print_usage_bug_scenario(this);
2248
2249        lockdep_print_held_locks(curr);
2250
2251        printk("\nstack backtrace:\n");
2252        dump_stack();
2253
2254        return 0;
2255}
2256
2257/*
2258 * Print out an error if an invalid bit is set:
2259 */
2260static inline int
2261valid_state(struct task_struct *curr, struct held_lock *this,
2262            enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit)
2263{
2264        if (unlikely(hlock_class(this)->usage_mask & (1 << bad_bit)))
2265                return print_usage_bug(curr, this, bad_bit, new_bit);
2266        return 1;
2267}
2268
2269static int mark_lock(struct task_struct *curr, struct held_lock *this,
2270                     enum lock_usage_bit new_bit);
2271
2272#if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
2273
2274/*
2275 * print irq inversion bug:
2276 */
2277static int
2278print_irq_inversion_bug(struct task_struct *curr,
2279                        struct lock_list *root, struct lock_list *other,
2280                        struct held_lock *this, int forwards,
2281                        const char *irqclass)
2282{
2283        struct lock_list *entry = other;
2284        struct lock_list *middle = NULL;
2285        int depth;
2286
2287        if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2288                return 0;
2289
2290        printk("\n");
2291        printk("=========================================================\n");
2292        printk("[ INFO: possible irq lock inversion dependency detected ]\n");
2293        print_kernel_ident();
2294        printk("---------------------------------------------------------\n");
2295        printk("%s/%d just changed the state of lock:\n",
2296                curr->comm, task_pid_nr(curr));
2297        print_lock(this);
2298        if (forwards)
2299                printk("but this lock took another, %s-unsafe lock in the past:\n", irqclass);
2300        else
2301                printk("but this lock was taken by another, %s-safe lock in the past:\n", irqclass);
2302        print_lock_name(other->class);
2303        printk("\n\nand interrupts could create inverse lock ordering between them.\n\n");
2304
2305        printk("\nother info that might help us debug this:\n");
2306
2307        /* Find a middle lock (if one exists) */
2308        depth = get_lock_depth(other);
2309        do {
2310                if (depth == 0 && (entry != root)) {
2311                        printk("lockdep:%s bad path found in chain graph\n", __func__);
2312                        break;
2313                }
2314                middle = entry;
2315                entry = get_lock_parent(entry);
2316                depth--;
2317        } while (entry && entry != root && (depth >= 0));
2318        if (forwards)
2319                print_irq_lock_scenario(root, other,
2320                        middle ? middle->class : root->class, other->class);
2321        else
2322                print_irq_lock_scenario(other, root,
2323                        middle ? middle->class : other->class, root->class);
2324
2325        lockdep_print_held_locks(curr);
2326
2327        printk("\nthe shortest dependencies between 2nd lock and 1st lock:\n");
2328        if (!save_trace(&root->trace))
2329                return 0;
2330        print_shortest_lock_dependencies(other, root);
2331
2332        printk("\nstack backtrace:\n");
2333        dump_stack();
2334
2335        return 0;
2336}
2337
2338/*
2339 * Prove that in the forwards-direction subgraph starting at <this>
2340 * there is no lock matching <mask>:
2341 */
2342static int
2343check_usage_forwards(struct task_struct *curr, struct held_lock *this,
2344                     enum lock_usage_bit bit, const char *irqclass)
2345{
2346        int ret;
2347        struct lock_list root;
2348        struct lock_list *uninitialized_var(target_entry);
2349
2350        root.parent = NULL;
2351        root.class = hlock_class(this);
2352        ret = find_usage_forwards(&root, bit, &target_entry);
2353        if (ret < 0)
2354                return print_bfs_bug(ret);
2355        if (ret == 1)
2356                return ret;
2357
2358        return print_irq_inversion_bug(curr, &root, target_entry,
2359                                        this, 1, irqclass);
2360}
2361
2362/*
2363 * Prove that in the backwards-direction subgraph starting at <this>
2364 * there is no lock matching <mask>:
2365 */
2366static int
2367check_usage_backwards(struct task_struct *curr, struct held_lock *this,
2368                      enum lock_usage_bit bit, const char *irqclass)
2369{
2370        int ret;
2371        struct lock_list root;
2372        struct lock_list *uninitialized_var(target_entry);
2373
2374        root.parent = NULL;
2375        root.class = hlock_class(this);
2376        ret = find_usage_backwards(&root, bit, &target_entry);
2377        if (ret < 0)
2378                return print_bfs_bug(ret);
2379        if (ret == 1)
2380                return ret;
2381
2382        return print_irq_inversion_bug(curr, &root, target_entry,
2383                                        this, 0, irqclass);
2384}
2385
2386void print_irqtrace_events(struct task_struct *curr)
2387{
2388        printk("irq event stamp: %u\n", curr->irq_events);
2389        printk("hardirqs last  enabled at (%u): ", curr->hardirq_enable_event);
2390        print_ip_sym(curr->hardirq_enable_ip);
2391        printk("hardirqs last disabled at (%u): ", curr->hardirq_disable_event);
2392        print_ip_sym(curr->hardirq_disable_ip);
2393        printk("softirqs last  enabled at (%u): ", curr->softirq_enable_event);
2394        print_ip_sym(curr->softirq_enable_ip);
2395        printk("softirqs last disabled at (%u): ", curr->softirq_disable_event);
2396        print_ip_sym(curr->softirq_disable_ip);
2397}
2398
2399static int HARDIRQ_verbose(struct lock_class *class)
2400{
2401#if HARDIRQ_VERBOSE
2402        return class_filter(class);
2403#endif
2404        return 0;
2405}
2406
2407static int SOFTIRQ_verbose(struct lock_class *class)
2408{
2409#if SOFTIRQ_VERBOSE
2410        return class_filter(class);
2411#endif
2412        return 0;
2413}
2414
2415static int RECLAIM_FS_verbose(struct lock_class *class)
2416{
2417#if RECLAIM_VERBOSE
2418        return class_filter(class);
2419#endif
2420        return 0;
2421}
2422
2423#define STRICT_READ_CHECKS      1
2424
2425static int (*state_verbose_f[])(struct lock_class *class) = {
2426#define LOCKDEP_STATE(__STATE) \
2427        __STATE##_verbose,
2428#include "lockdep_states.h"
2429#undef LOCKDEP_STATE
2430};
2431
2432static inline int state_verbose(enum lock_usage_bit bit,
2433                                struct lock_class *class)
2434{
2435        return state_verbose_f[bit >> 2](class);
2436}
2437
2438typedef int (*check_usage_f)(struct task_struct *, struct held_lock *,
2439                             enum lock_usage_bit bit, const char *name);
2440
2441static int
2442mark_lock_irq(struct task_struct *curr, struct held_lock *this,
2443                enum lock_usage_bit new_bit)
2444{
2445        int excl_bit = exclusive_bit(new_bit);
2446        int read = new_bit & 1;
2447        int dir = new_bit & 2;
2448
2449        /*
2450         * mark USED_IN has to look forwards -- to ensure no dependency
2451         * has ENABLED state, which would allow recursion deadlocks.
2452         *
2453         * mark ENABLED has to look backwards -- to ensure no dependee
2454         * has USED_IN state, which, again, would allow  recursion deadlocks.
2455         */
2456        check_usage_f usage = dir ?
2457                check_usage_backwards : check_usage_forwards;
2458
2459        /*
2460         * Validate that this particular lock does not have conflicting
2461         * usage states.
2462         */
2463        if (!valid_state(curr, this, new_bit, excl_bit))
2464                return 0;
2465
2466        /*
2467         * Validate that the lock dependencies don't have conflicting usage
2468         * states.
2469         */
2470        if ((!read || !dir || STRICT_READ_CHECKS) &&
2471                        !usage(curr, this, excl_bit, state_name(new_bit & ~1)))
2472                return 0;
2473
2474        /*
2475         * Check for read in write conflicts
2476         */
2477        if (!read) {
2478                if (!valid_state(curr, this, new_bit, excl_bit + 1))
2479                        return 0;
2480
2481                if (STRICT_READ_CHECKS &&
2482                        !usage(curr, this, excl_bit + 1,
2483                                state_name(new_bit + 1)))
2484                        return 0;
2485        }
2486
2487        if (state_verbose(new_bit, hlock_class(this)))
2488                return 2;
2489
2490        return 1;
2491}
2492
2493enum mark_type {
2494#define LOCKDEP_STATE(__STATE)  __STATE,
2495#include "lockdep_states.h"
2496#undef LOCKDEP_STATE
2497};
2498
2499/*
2500 * Mark all held locks with a usage bit:
2501 */
2502static int
2503mark_held_locks(struct task_struct *curr, enum mark_type mark)
2504{
2505        enum lock_usage_bit usage_bit;
2506        struct held_lock *hlock;
2507        int i;
2508
2509        for (i = 0; i < curr->lockdep_depth; i++) {
2510                hlock = curr->held_locks + i;
2511
2512                usage_bit = 2 + (mark << 2); /* ENABLED */
2513                if (hlock->read)
2514                        usage_bit += 1; /* READ */
2515
2516                BUG_ON(usage_bit >= LOCK_USAGE_STATES);
2517
2518                if (hlock_class(hlock)->key == __lockdep_no_validate__.subkeys)
2519                        continue;
2520
2521                if (!mark_lock(curr, hlock, usage_bit))
2522                        return 0;
2523        }
2524
2525        return 1;
2526}
2527
2528/*
2529 * Hardirqs will be enabled:
2530 */
2531static void __trace_hardirqs_on_caller(unsigned long ip)
2532{
2533        struct task_struct *curr = current;
2534
2535        /* we'll do an OFF -> ON transition: */
2536        curr->hardirqs_enabled = 1;
2537
2538        /*
2539         * We are going to turn hardirqs on, so set the
2540         * usage bit for all held locks:
2541         */
2542        if (!mark_held_locks(curr, HARDIRQ))
2543                return;
2544        /*
2545         * If we have softirqs enabled, then set the usage
2546         * bit for all held locks. (disabled hardirqs prevented
2547         * this bit from being set before)
2548         */
2549        if (curr->softirqs_enabled)
2550                if (!mark_held_locks(curr, SOFTIRQ))
2551                        return;
2552
2553        curr->hardirq_enable_ip = ip;
2554        curr->hardirq_enable_event = ++curr->irq_events;
2555        debug_atomic_inc(hardirqs_on_events);
2556}
2557
2558void trace_hardirqs_on_caller(unsigned long ip)
2559{
2560        time_hardirqs_on(CALLER_ADDR0, ip);
2561
2562        if (unlikely(!debug_locks || current->lockdep_recursion))
2563                return;
2564
2565        if (unlikely(current->hardirqs_enabled)) {
2566                /*
2567                 * Neither irq nor preemption are disabled here
2568                 * so this is racy by nature but losing one hit
2569                 * in a stat is not a big deal.
2570                 */
2571                __debug_atomic_inc(redundant_hardirqs_on);
2572                return;
2573        }
2574
2575        /*
2576         * We're enabling irqs and according to our state above irqs weren't
2577         * already enabled, yet we find the hardware thinks they are in fact
2578         * enabled.. someone messed up their IRQ state tracing.
2579         */
2580        if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2581                return;
2582
2583        /*
2584         * See the fine text that goes along with this variable definition.
2585         */
2586        if (DEBUG_LOCKS_WARN_ON(unlikely(early_boot_irqs_disabled)))
2587                return;
2588
2589        /*
2590         * Can't allow enabling interrupts while in an interrupt handler,
2591         * that's general bad form and such. Recursion, limited stack etc..
2592         */
2593        if (DEBUG_LOCKS_WARN_ON(current->hardirq_context))
2594                return;
2595
2596        current->lockdep_recursion = 1;
2597        __trace_hardirqs_on_caller(ip);
2598        current->lockdep_recursion = 0;
2599}
2600EXPORT_SYMBOL(trace_hardirqs_on_caller);
2601
2602void trace_hardirqs_on(void)
2603{
2604        trace_hardirqs_on_caller(CALLER_ADDR0);
2605}
2606EXPORT_SYMBOL(trace_hardirqs_on);
2607
2608/*
2609 * Hardirqs were disabled:
2610 */
2611void trace_hardirqs_off_caller(unsigned long ip)
2612{
2613        struct task_struct *curr = current;
2614
2615        time_hardirqs_off(CALLER_ADDR0, ip);
2616
2617        if (unlikely(!debug_locks || current->lockdep_recursion))
2618                return;
2619
2620        /*
2621         * So we're supposed to get called after you mask local IRQs, but for
2622         * some reason the hardware doesn't quite think you did a proper job.
2623         */
2624        if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2625                return;
2626
2627        if (curr->hardirqs_enabled) {
2628                /*
2629                 * We have done an ON -> OFF transition:
2630                 */
2631                curr->hardirqs_enabled = 0;
2632                curr->hardirq_disable_ip = ip;
2633                curr->hardirq_disable_event = ++curr->irq_events;
2634                debug_atomic_inc(hardirqs_off_events);
2635        } else
2636                debug_atomic_inc(redundant_hardirqs_off);
2637}
2638EXPORT_SYMBOL(trace_hardirqs_off_caller);
2639
2640void trace_hardirqs_off(void)
2641{
2642        trace_hardirqs_off_caller(CALLER_ADDR0);
2643}
2644EXPORT_SYMBOL(trace_hardirqs_off);
2645
2646/*
2647 * Softirqs will be enabled:
2648 */
2649void trace_softirqs_on(unsigned long ip)
2650{
2651        struct task_struct *curr = current;
2652
2653        if (unlikely(!debug_locks || current->lockdep_recursion))
2654                return;
2655
2656        /*
2657         * We fancy IRQs being disabled here, see softirq.c, avoids
2658         * funny state and nesting things.
2659         */
2660        if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2661                return;
2662
2663        if (curr->softirqs_enabled) {
2664                debug_atomic_inc(redundant_softirqs_on);
2665                return;
2666        }
2667
2668        current->lockdep_recursion = 1;
2669        /*
2670         * We'll do an OFF -> ON transition:
2671         */
2672        curr->softirqs_enabled = 1;
2673        curr->softirq_enable_ip = ip;
2674        curr->softirq_enable_event = ++curr->irq_events;
2675        debug_atomic_inc(softirqs_on_events);
2676        /*
2677         * We are going to turn softirqs on, so set the
2678         * usage bit for all held locks, if hardirqs are
2679         * enabled too:
2680         */
2681        if (curr->hardirqs_enabled)
2682                mark_held_locks(curr, SOFTIRQ);
2683        current->lockdep_recursion = 0;
2684}
2685
2686/*
2687 * Softirqs were disabled:
2688 */
2689void trace_softirqs_off(unsigned long ip)
2690{
2691        struct task_struct *curr = current;
2692
2693        if (unlikely(!debug_locks || current->lockdep_recursion))
2694                return;
2695
2696        /*
2697         * We fancy IRQs being disabled here, see softirq.c
2698         */
2699        if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2700                return;
2701
2702        if (curr->softirqs_enabled) {
2703                /*
2704                 * We have done an ON -> OFF transition:
2705                 */
2706                curr->softirqs_enabled = 0;
2707                curr->softirq_disable_ip = ip;
2708                curr->softirq_disable_event = ++curr->irq_events;
2709                debug_atomic_inc(softirqs_off_events);
2710                /*
2711                 * Whoops, we wanted softirqs off, so why aren't they?
2712                 */
2713                DEBUG_LOCKS_WARN_ON(!softirq_count());
2714        } else
2715                debug_atomic_inc(redundant_softirqs_off);
2716}
2717
2718static void __lockdep_trace_alloc(gfp_t gfp_mask, unsigned long flags)
2719{
2720        struct task_struct *curr = current;
2721
2722        if (unlikely(!debug_locks))
2723                return;
2724
2725        /* no reclaim without waiting on it */
2726        if (!(gfp_mask & __GFP_WAIT))
2727                return;
2728
2729        /* this guy won't enter reclaim */
2730        if ((curr->flags & PF_MEMALLOC) && !(gfp_mask & __GFP_NOMEMALLOC))
2731                return;
2732
2733        /* We're only interested __GFP_FS allocations for now */
2734        if (!(gfp_mask & __GFP_FS))
2735                return;
2736
2737        /*
2738         * Oi! Can't be having __GFP_FS allocations with IRQs disabled.
2739         */
2740        if (DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags)))
2741                return;
2742
2743        mark_held_locks(curr, RECLAIM_FS);
2744}
2745
2746static void check_flags(unsigned long flags);
2747
2748void lockdep_trace_alloc(gfp_t gfp_mask)
2749{
2750        unsigned long flags;
2751
2752        if (unlikely(current->lockdep_recursion))
2753                return;
2754
2755        raw_local_irq_save(flags);
2756        check_flags(flags);
2757        current->lockdep_recursion = 1;
2758        __lockdep_trace_alloc(gfp_mask, flags);
2759        current->lockdep_recursion = 0;
2760        raw_local_irq_restore(flags);
2761}
2762
2763static int mark_irqflags(struct task_struct *curr, struct held_lock *hlock)
2764{
2765        /*
2766         * If non-trylock use in a hardirq or softirq context, then
2767         * mark the lock as used in these contexts:
2768         */
2769        if (!hlock->trylock) {
2770                if (hlock->read) {
2771                        if (curr->hardirq_context)
2772                                if (!mark_lock(curr, hlock,
2773                                                LOCK_USED_IN_HARDIRQ_READ))
2774                                        return 0;
2775                        if (curr->softirq_context)
2776                                if (!mark_lock(curr, hlock,
2777                                                LOCK_USED_IN_SOFTIRQ_READ))
2778                                        return 0;
2779                } else {
2780                        if (curr->hardirq_context)
2781                                if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ))
2782                                        return 0;
2783                        if (curr->softirq_context)
2784                                if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ))
2785                                        return 0;
2786                }
2787        }
2788        if (!hlock->hardirqs_off) {
2789                if (hlock->read) {
2790                        if (!mark_lock(curr, hlock,
2791                                        LOCK_ENABLED_HARDIRQ_READ))
2792                                return 0;
2793                        if (curr->softirqs_enabled)
2794                                if (!mark_lock(curr, hlock,
2795                                                LOCK_ENABLED_SOFTIRQ_READ))
2796                                        return 0;
2797                } else {
2798                        if (!mark_lock(curr, hlock,
2799                                        LOCK_ENABLED_HARDIRQ))
2800                                return 0;
2801                        if (curr->softirqs_enabled)
2802                                if (!mark_lock(curr, hlock,
2803                                                LOCK_ENABLED_SOFTIRQ))
2804                                        return 0;
2805                }
2806        }
2807
2808        /*
2809         * We reuse the irq context infrastructure more broadly as a general
2810         * context checking code. This tests GFP_FS recursion (a lock taken
2811         * during reclaim for a GFP_FS allocation is held over a GFP_FS
2812         * allocation).
2813         */
2814        if (!hlock->trylock && (curr->lockdep_reclaim_gfp & __GFP_FS)) {
2815                if (hlock->read) {
2816                        if (!mark_lock(curr, hlock, LOCK_USED_IN_RECLAIM_FS_READ))
2817                                        return 0;
2818                } else {
2819                        if (!mark_lock(curr, hlock, LOCK_USED_IN_RECLAIM_FS))
2820                                        return 0;
2821                }
2822        }
2823
2824        return 1;
2825}
2826
2827static int separate_irq_context(struct task_struct *curr,
2828                struct held_lock *hlock)
2829{
2830        unsigned int depth = curr->lockdep_depth;
2831
2832        /*
2833         * Keep track of points where we cross into an interrupt context:
2834         */
2835        hlock->irq_context = 2*(curr->hardirq_context ? 1 : 0) +
2836                                curr->softirq_context;
2837        if (depth) {
2838                struct held_lock *prev_hlock;
2839
2840                prev_hlock = curr->held_locks + depth-1;
2841                /*
2842                 * If we cross into another context, reset the
2843                 * hash key (this also prevents the checking and the
2844                 * adding of the dependency to 'prev'):
2845                 */
2846                if (prev_hlock->irq_context != hlock->irq_context)
2847                        return 1;
2848        }
2849        return 0;
2850}
2851
2852#else /* defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING) */
2853
2854static inline
2855int mark_lock_irq(struct task_struct *curr, struct held_lock *this,
2856                enum lock_usage_bit new_bit)
2857{
2858        WARN_ON(1); /* Impossible innit? when we don't have TRACE_IRQFLAG */
2859        return 1;
2860}
2861
2862static inline int mark_irqflags(struct task_struct *curr,
2863                struct held_lock *hlock)
2864{
2865        return 1;
2866}
2867
2868static inline int separate_irq_context(struct task_struct *curr,
2869                struct held_lock *hlock)
2870{
2871        return 0;
2872}
2873
2874void lockdep_trace_alloc(gfp_t gfp_mask)
2875{
2876}
2877
2878#endif /* defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING) */
2879
2880/*
2881 * Mark a lock with a usage bit, and validate the state transition:
2882 */
2883static int mark_lock(struct task_struct *curr, struct held_lock *this,
2884                             enum lock_usage_bit new_bit)
2885{
2886        unsigned int new_mask = 1 << new_bit, ret = 1;
2887
2888        /*
2889         * If already set then do not dirty the cacheline,
2890         * nor do any checks:
2891         */
2892        if (likely(hlock_class(this)->usage_mask & new_mask))
2893                return 1;
2894
2895        if (!graph_lock())
2896                return 0;
2897        /*
2898         * Make sure we didn't race:
2899         */
2900        if (unlikely(hlock_class(this)->usage_mask & new_mask)) {
2901                graph_unlock();
2902                return 1;
2903        }
2904
2905        hlock_class(this)->usage_mask |= new_mask;
2906
2907        if (!save_trace(hlock_class(this)->usage_traces + new_bit))
2908                return 0;
2909
2910        switch (new_bit) {
2911#define LOCKDEP_STATE(__STATE)                  \
2912        case LOCK_USED_IN_##__STATE:            \
2913        case LOCK_USED_IN_##__STATE##_READ:     \
2914        case LOCK_ENABLED_##__STATE:            \
2915        case LOCK_ENABLED_##__STATE##_READ:
2916#include "lockdep_states.h"
2917#undef LOCKDEP_STATE
2918                ret = mark_lock_irq(curr, this, new_bit);
2919                if (!ret)
2920                        return 0;
2921                break;
2922        case LOCK_USED:
2923                debug_atomic_dec(nr_unused_locks);
2924                break;
2925        default:
2926                if (!debug_locks_off_graph_unlock())
2927                        return 0;
2928                WARN_ON(1);
2929                return 0;
2930        }
2931
2932        graph_unlock();
2933
2934        /*
2935         * We must printk outside of the graph_lock:
2936         */
2937        if (ret == 2) {
2938                printk("\nmarked lock as {%s}:\n", usage_str[new_bit]);
2939                print_lock(this);
2940                print_irqtrace_events(curr);
2941                dump_stack();
2942        }
2943
2944        return ret;
2945}
2946
2947/*
2948 * Initialize a lock instance's lock-class mapping info:
2949 */
2950void lockdep_init_map(struct lockdep_map *lock, const char *name,
2951                      struct lock_class_key *key, int subclass)
2952{
2953        int i;
2954
2955        kmemcheck_mark_initialized(lock, sizeof(*lock));
2956
2957        for (i = 0; i < NR_LOCKDEP_CACHING_CLASSES; i++)
2958                lock->class_cache[i] = NULL;
2959
2960#ifdef CONFIG_LOCK_STAT
2961        lock->cpu = raw_smp_processor_id();
2962#endif
2963
2964        /*
2965         * Can't be having no nameless bastards around this place!
2966         */
2967        if (DEBUG_LOCKS_WARN_ON(!name)) {
2968                lock->name = "NULL";
2969                return;
2970        }
2971
2972        lock->name = name;
2973
2974        /*
2975         * No key, no joy, we need to hash something.
2976         */
2977        if (DEBUG_LOCKS_WARN_ON(!key))
2978                return;
2979        /*
2980         * Sanity check, the lock-class key must be persistent:
2981         */
2982        if (!static_obj(key)) {
2983                printk("BUG: key %p not in .data!\n", key);
2984                /*
2985                 * What it says above ^^^^^, I suggest you read it.
2986                 */
2987                DEBUG_LOCKS_WARN_ON(1);
2988                return;
2989        }
2990        lock->key = key;
2991
2992        if (unlikely(!debug_locks))
2993                return;
2994
2995        if (subclass)
2996                register_lock_class(lock, subclass, 1);
2997}
2998EXPORT_SYMBOL_GPL(lockdep_init_map);
2999
3000struct lock_class_key __lockdep_no_validate__;
3001EXPORT_SYMBOL_GPL(__lockdep_no_validate__);
3002
3003static int
3004print_lock_nested_lock_not_held(struct task_struct *curr,
3005                                struct held_lock *hlock,
3006                                unsigned long ip)
3007{
3008        if (!debug_locks_off())
3009                return 0;
3010        if (debug_locks_silent)
3011                return 0;
3012
3013        printk("\n");
3014        printk("==================================\n");
3015        printk("[ BUG: Nested lock was not taken ]\n");
3016        print_kernel_ident();
3017        printk("----------------------------------\n");
3018
3019        printk("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr));
3020        print_lock(hlock);
3021
3022        printk("\nbut this task is not holding:\n");
3023        printk("%s\n", hlock->nest_lock->name);
3024
3025        printk("\nstack backtrace:\n");
3026        dump_stack();
3027
3028        printk("\nother info that might help us debug this:\n");
3029        lockdep_print_held_locks(curr);
3030
3031        printk("\nstack backtrace:\n");
3032        dump_stack();
3033
3034        return 0;
3035}
3036
3037static int __lock_is_held(struct lockdep_map *lock);
3038
3039/*
3040 * This gets called for every mutex_lock*()/spin_lock*() operation.
3041 * We maintain the dependency maps and validate the locking attempt:
3042 */
3043static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
3044                          int trylock, int read, int check, int hardirqs_off,
3045                          struct lockdep_map *nest_lock, unsigned long ip,
3046                          int references)
3047{
3048        struct task_struct *curr = current;
3049        struct lock_class *class = NULL;
3050        struct held_lock *hlock;
3051        unsigned int depth, id;
3052        int chain_head = 0;
3053        int class_idx;
3054        u64 chain_key;
3055
3056        if (!prove_locking)
3057                check = 1;
3058
3059        if (unlikely(!debug_locks))
3060                return 0;
3061
3062        /*
3063         * Lockdep should run with IRQs disabled, otherwise we could
3064         * get an interrupt which would want to take locks, which would
3065         * end up in lockdep and have you got a head-ache already?
3066         */
3067        if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
3068                return 0;
3069
3070        if (lock->key == &__lockdep_no_validate__)
3071                check = 1;
3072
3073        if (subclass < NR_LOCKDEP_CACHING_CLASSES)
3074                class = lock->class_cache[subclass];
3075        /*
3076         * Not cached?
3077         */
3078        if (unlikely(!class)) {
3079                class = register_lock_class(lock, subclass, 0);
3080                if (!class)
3081                        return 0;
3082        }
3083        atomic_inc((atomic_t *)&class->ops);
3084        if (very_verbose(class)) {
3085                printk("\nacquire class [%p] %s", class->key, class->name);
3086                if (class->name_version > 1)
3087                        printk("#%d", class->name_version);
3088                printk("\n");
3089                dump_stack();
3090        }
3091
3092        /*
3093         * Add the lock to the list of currently held locks.
3094         * (we dont increase the depth just yet, up until the
3095         * dependency checks are done)
3096         */
3097        depth = curr->lockdep_depth;
3098        /*
3099         * Ran out of static storage for our per-task lock stack again have we?
3100         */
3101        if (DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH))
3102                return 0;
3103
3104        class_idx = class - lock_classes + 1;
3105
3106        if (depth) {
3107                hlock = curr->held_locks + depth - 1;
3108                if (hlock->class_idx == class_idx && nest_lock) {
3109                        if (hlock->references)
3110                                hlock->references++;
3111                        else
3112                                hlock->references = 2;
3113
3114                        return 1;
3115                }
3116        }
3117
3118        hlock = curr->held_locks + depth;
3119        /*
3120         * Plain impossible, we just registered it and checked it weren't no
3121         * NULL like.. I bet this mushroom I ate was good!
3122         */
3123        if (DEBUG_LOCKS_WARN_ON(!class))
3124                return 0;
3125        hlock->class_idx = class_idx;
3126        hlock->acquire_ip = ip;
3127        hlock->instance = lock;
3128        hlock->nest_lock = nest_lock;
3129        hlock->trylock = trylock;
3130        hlock->read = read;
3131        hlock->check = check;
3132        hlock->hardirqs_off = !!hardirqs_off;
3133        hlock->references = references;
3134#ifdef CONFIG_LOCK_STAT
3135        hlock->waittime_stamp = 0;
3136        hlock->holdtime_stamp = lockstat_clock();
3137#endif
3138
3139        if (check == 2 && !mark_irqflags(curr, hlock))
3140                return 0;
3141
3142        /* mark it as used: */
3143        if (!mark_lock(curr, hlock, LOCK_USED))
3144                return 0;
3145
3146        /*
3147         * Calculate the chain hash: it's the combined hash of all the
3148         * lock keys along the dependency chain. We save the hash value
3149         * at every step so that we can get the current hash easily
3150         * after unlock. The chain hash is then used to cache dependency
3151         * results.
3152         *
3153         * The 'key ID' is what is the most compact key value to drive
3154         * the hash, not class->key.
3155         */
3156        id = class - lock_classes;
3157        /*
3158         * Whoops, we did it again.. ran straight out of our static allocation.
3159         */
3160        if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
3161                return 0;
3162
3163        chain_key = curr->curr_chain_key;
3164        if (!depth) {
3165                /*
3166                 * How can we have a chain hash when we ain't got no keys?!
3167                 */
3168                if (DEBUG_LOCKS_WARN_ON(chain_key != 0))
3169                        return 0;
3170                chain_head = 1;
3171        }
3172
3173        hlock->prev_chain_key = chain_key;
3174        if (separate_irq_context(curr, hlock)) {
3175                chain_key = 0;
3176                chain_head = 1;
3177        }
3178        chain_key = iterate_chain_key(chain_key, id);
3179
3180        if (nest_lock && !__lock_is_held(nest_lock))
3181                return print_lock_nested_lock_not_held(curr, hlock, ip);
3182
3183        if (!validate_chain(curr, lock, hlock, chain_head, chain_key))
3184                return 0;
3185
3186        curr->curr_chain_key = chain_key;
3187        curr->lockdep_depth++;
3188        check_chain_key(curr);
3189#ifdef CONFIG_DEBUG_LOCKDEP
3190        if (unlikely(!debug_locks))
3191                return 0;
3192#endif
3193        if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
3194                debug_locks_off();
3195                print_lockdep_off("BUG: MAX_LOCK_DEPTH too low!");
3196                printk(KERN_DEBUG "depth: %i  max: %lu!\n",
3197                       curr->lockdep_depth, MAX_LOCK_DEPTH);
3198
3199                lockdep_print_held_locks(current);
3200                debug_show_all_locks();
3201                dump_stack();
3202
3203                return 0;
3204        }
3205
3206        if (unlikely(curr->lockdep_depth > max_lockdep_depth))
3207                max_lockdep_depth = curr->lockdep_depth;
3208
3209        return 1;
3210}
3211
3212static int
3213print_unlock_imbalance_bug(struct task_struct *curr, struct lockdep_map *lock,
3214                           unsigned long ip)
3215{
3216        if (!debug_locks_off())
3217                return 0;
3218        if (debug_locks_silent)
3219                return 0;
3220
3221        printk("\n");
3222        printk("=====================================\n");
3223        printk("[ BUG: bad unlock balance detected! ]\n");
3224        print_kernel_ident();
3225        printk("-------------------------------------\n");
3226        printk("%s/%d is trying to release lock (",
3227                curr->comm, task_pid_nr(curr));
3228        print_lockdep_cache(lock);
3229        printk(") at:\n");
3230        print_ip_sym(ip);
3231        printk("but there are no more locks to release!\n");
3232        printk("\nother info that might help us debug this:\n");
3233        lockdep_print_held_locks(curr);
3234
3235        printk("\nstack backtrace:\n");
3236        dump_stack();
3237
3238        return 0;
3239}
3240
3241/*
3242 * Common debugging checks for both nested and non-nested unlock:
3243 */
3244static int check_unlock(struct task_struct *curr, struct lockdep_map *lock,
3245                        unsigned long ip)
3246{
3247        if (unlikely(!debug_locks))
3248                return 0;
3249        /*
3250         * Lockdep should run with IRQs disabled, recursion, head-ache, etc..
3251         */
3252        if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
3253                return 0;
3254
3255        if (curr->lockdep_depth <= 0)
3256                return print_unlock_imbalance_bug(curr, lock, ip);
3257
3258        return 1;
3259}
3260
3261static int match_held_lock(struct held_lock *hlock, struct lockdep_map *lock)
3262{
3263        if (hlock->instance == lock)
3264                return 1;
3265
3266        if (hlock->references) {
3267                struct lock_class *class = lock->class_cache[0];
3268
3269                if (!class)
3270                        class = look_up_lock_class(lock, 0);
3271
3272                /*
3273                 * If look_up_lock_class() failed to find a class, we're trying
3274                 * to test if we hold a lock that has never yet been acquired.
3275                 * Clearly if the lock hasn't been acquired _ever_, we're not
3276                 * holding it either, so report failure.
3277                 */
3278                if (!class)
3279                        return 0;
3280
3281                /*
3282                 * References, but not a lock we're actually ref-counting?
3283                 * State got messed up, follow the sites that change ->references
3284                 * and try to make sense of it.
3285                 */
3286                if (DEBUG_LOCKS_WARN_ON(!hlock->nest_lock))
3287                        return 0;
3288
3289                if (hlock->class_idx == class - lock_classes + 1)
3290                        return 1;
3291        }
3292
3293        return 0;
3294}
3295
3296static int
3297__lock_set_class(struct lockdep_map *lock, const char *name,
3298                 struct lock_class_key *key, unsigned int subclass,
3299                 unsigned long ip)
3300{
3301        struct task_struct *curr = current;
3302        struct held_lock *hlock, *prev_hlock;
3303        struct lock_class *class;
3304        unsigned int depth;
3305        int i;
3306
3307        depth = curr->lockdep_depth;
3308        /*
3309         * This function is about (re)setting the class of a held lock,
3310         * yet we're not actually holding any locks. Naughty user!
3311         */
3312        if (DEBUG_LOCKS_WARN_ON(!depth))
3313                return 0;
3314
3315        prev_hlock = NULL;
3316        for (i = depth-1; i >= 0; i--) {
3317                hlock = curr->held_locks + i;
3318                /*
3319                 * We must not cross into another context:
3320                 */
3321                if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3322                        break;
3323                if (match_held_lock(hlock, lock))
3324                        goto found_it;
3325                prev_hlock = hlock;
3326        }
3327        return print_unlock_imbalance_bug(curr, lock, ip);
3328
3329found_it:
3330        lockdep_init_map(lock, name, key, 0);
3331        class = register_lock_class(lock, subclass, 0);
3332        hlock->class_idx = class - lock_classes + 1;
3333
3334        curr->lockdep_depth = i;
3335        curr->curr_chain_key = hlock->prev_chain_key;
3336
3337        for (; i < depth; i++) {
3338                hlock = curr->held_locks + i;
3339                if (!__lock_acquire(hlock->instance,
3340                        hlock_class(hlock)->subclass, hlock->trylock,
3341                                hlock->read, hlock->check, hlock->hardirqs_off,
3342                                hlock->nest_lock, hlock->acquire_ip,
3343                                hlock->references))
3344                        return 0;
3345        }
3346
3347        /*
3348         * I took it apart and put it back together again, except now I have
3349         * these 'spare' parts.. where shall I put them.
3350         */
3351        if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth))
3352                return 0;
3353        return 1;
3354}
3355
3356/*
3357 * Remove the lock to the list of currently held locks in a
3358 * potentially non-nested (out of order) manner. This is a
3359 * relatively rare operation, as all the unlock APIs default
3360 * to nested mode (which uses lock_release()):
3361 */
3362static int
3363lock_release_non_nested(struct task_struct *curr,
3364                        struct lockdep_map *lock, unsigned long ip)
3365{
3366        struct held_lock *hlock, *prev_hlock;
3367        unsigned int depth;
3368        int i;
3369
3370        /*
3371         * Check whether the lock exists in the current stack
3372         * of held locks:
3373         */
3374        depth = curr->lockdep_depth;
3375        /*
3376         * So we're all set to release this lock.. wait what lock? We don't
3377         * own any locks, you've been drinking again?
3378         */
3379        if (DEBUG_LOCKS_WARN_ON(!depth))
3380                return 0;
3381
3382        prev_hlock = NULL;
3383        for (i = depth-1; i >= 0; i--) {
3384                hlock = curr->held_locks + i;
3385                /*
3386                 * We must not cross into another context:
3387                 */
3388                if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3389                        break;
3390                if (match_held_lock(hlock, lock))
3391                        goto found_it;
3392                prev_hlock = hlock;
3393        }
3394        return print_unlock_imbalance_bug(curr, lock, ip);
3395
3396found_it:
3397        if (hlock->instance == lock)
3398                lock_release_holdtime(hlock);
3399
3400        if (hlock->references) {
3401                hlock->references--;
3402                if (hlock->references) {
3403                        /*
3404                         * We had, and after removing one, still have
3405                         * references, the current lock stack is still
3406                         * valid. We're done!
3407                         */
3408                        return 1;
3409                }
3410        }
3411
3412        /*
3413         * We have the right lock to unlock, 'hlock' points to it.
3414         * Now we remove it from the stack, and add back the other
3415         * entries (if any), recalculating the hash along the way:
3416         */
3417
3418        curr->lockdep_depth = i;
3419        curr->curr_chain_key = hlock->prev_chain_key;
3420
3421        for (i++; i < depth; i++) {
3422                hlock = curr->held_locks + i;
3423                if (!__lock_acquire(hlock->instance,
3424                        hlock_class(hlock)->subclass, hlock->trylock,
3425                                hlock->read, hlock->check, hlock->hardirqs_off,
3426                                hlock->nest_lock, hlock->acquire_ip,
3427                                hlock->references))
3428                        return 0;
3429        }
3430
3431        /*
3432         * We had N bottles of beer on the wall, we drank one, but now
3433         * there's not N-1 bottles of beer left on the wall...
3434         */
3435        if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - 1))
3436                return 0;
3437        return 1;
3438}
3439
3440/*
3441 * Remove the lock to the list of currently held locks - this gets
3442 * called on mutex_unlock()/spin_unlock*() (or on a failed
3443 * mutex_lock_interruptible()). This is done for unlocks that nest
3444 * perfectly. (i.e. the current top of the lock-stack is unlocked)
3445 */
3446static int lock_release_nested(struct task_struct *curr,
3447                               struct lockdep_map *lock, unsigned long ip)
3448{
3449        struct held_lock *hlock;
3450        unsigned int depth;
3451
3452        /*
3453         * Pop off the top of the lock stack:
3454         */
3455        depth = curr->lockdep_depth - 1;
3456        hlock = curr->held_locks + depth;
3457
3458        /*
3459         * Is the unlock non-nested:
3460         */
3461        if (hlock->instance != lock || hlock->references)
3462                return lock_release_non_nested(curr, lock, ip);
3463        curr->lockdep_depth--;
3464
3465        /*
3466         * No more locks, but somehow we've got hash left over, who left it?
3467         */
3468        if (DEBUG_LOCKS_WARN_ON(!depth && (hlock->prev_chain_key != 0)))
3469                return 0;
3470
3471        curr->curr_chain_key = hlock->prev_chain_key;
3472
3473        lock_release_holdtime(hlock);
3474
3475#ifdef CONFIG_DEBUG_LOCKDEP
3476        hlock->prev_chain_key = 0;
3477        hlock->class_idx = 0;
3478        hlock->acquire_ip = 0;
3479        hlock->irq_context = 0;
3480#endif
3481        return 1;
3482}
3483
3484/*
3485 * Remove the lock to the list of currently held locks - this gets
3486 * called on mutex_unlock()/spin_unlock*() (or on a failed
3487 * mutex_lock_interruptible()). This is done for unlocks that nest
3488 * perfectly. (i.e. the current top of the lock-stack is unlocked)
3489 */
3490static void
3491__lock_release(struct lockdep_map *lock, int nested, unsigned long ip)
3492{
3493        struct task_struct *curr = current;
3494
3495        if (!check_unlock(curr, lock, ip))
3496                return;
3497
3498        if (nested) {
3499                if (!lock_release_nested(curr, lock, ip))
3500                        return;
3501        } else {
3502                if (!lock_release_non_nested(curr, lock, ip))
3503                        return;
3504        }
3505
3506        check_chain_key(curr);
3507}
3508
3509static int __lock_is_held(struct lockdep_map *lock)
3510{
3511        struct task_struct *curr = current;
3512        int i;
3513
3514        for (i = 0; i < curr->lockdep_depth; i++) {
3515                struct held_lock *hlock = curr->held_locks + i;
3516
3517                if (match_held_lock(hlock, lock))
3518                        return 1;
3519        }
3520
3521        return 0;
3522}
3523
3524/*
3525 * Check whether we follow the irq-flags state precisely:
3526 */
3527static void check_flags(unsigned long flags)
3528{
3529#if defined(CONFIG_PROVE_LOCKING) && defined(CONFIG_DEBUG_LOCKDEP) && \
3530    defined(CONFIG_TRACE_IRQFLAGS)
3531        if (!debug_locks)
3532                return;
3533
3534        if (irqs_disabled_flags(flags)) {
3535                if (DEBUG_LOCKS_WARN_ON(current->hardirqs_enabled)) {
3536                        printk("possible reason: unannotated irqs-off.\n");
3537                }
3538        } else {
3539                if (DEBUG_LOCKS_WARN_ON(!current->hardirqs_enabled)) {
3540                        printk("possible reason: unannotated irqs-on.\n");
3541                }
3542        }
3543
3544        /*
3545         * We dont accurately track softirq state in e.g.
3546         * hardirq contexts (such as on 4KSTACKS), so only
3547         * check if not in hardirq contexts:
3548         */
3549        if (!hardirq_count()) {
3550                if (softirq_count()) {
3551                        /* like the above, but with softirqs */
3552                        DEBUG_LOCKS_WARN_ON(current->softirqs_enabled);
3553                } else {
3554                        /* lick the above, does it taste good? */
3555                        DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled);
3556                }
3557        }
3558
3559        if (!debug_locks)
3560                print_irqtrace_events(current);
3561#endif
3562}
3563
3564void lock_set_class(struct lockdep_map *lock, const char *name,
3565                    struct lock_class_key *key, unsigned int subclass,
3566                    unsigned long ip)
3567{
3568        unsigned long flags;
3569
3570        if (unlikely(current->lockdep_recursion))
3571                return;
3572
3573        raw_local_irq_save(flags);
3574        current->lockdep_recursion = 1;
3575        check_flags(flags);
3576        if (__lock_set_class(lock, name, key, subclass, ip))
3577                check_chain_key(current);
3578        current->lockdep_recursion = 0;
3579        raw_local_irq_restore(flags);
3580}
3581EXPORT_SYMBOL_GPL(lock_set_class);
3582
3583/*
3584 * We are not always called with irqs disabled - do that here,
3585 * and also avoid lockdep recursion:
3586 */
3587void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
3588                          int trylock, int read, int check,
3589                          struct lockdep_map *nest_lock, unsigned long ip)
3590{
3591        unsigned long flags;
3592
3593        if (unlikely(current->lockdep_recursion))
3594                return;
3595
3596        raw_local_irq_save(flags);
3597        check_flags(flags);
3598
3599        current->lockdep_recursion = 1;
3600        trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip);
3601        __lock_acquire(lock, subclass, trylock, read, check,
3602                       irqs_disabled_flags(flags), nest_lock, ip, 0);
3603        current->lockdep_recursion = 0;
3604        raw_local_irq_restore(flags);
3605}
3606EXPORT_SYMBOL_GPL(lock_acquire);
3607
3608void lock_release(struct lockdep_map *lock, int nested,
3609                          unsigned long ip)
3610{
3611        unsigned long flags;
3612
3613        if (unlikely(current->lockdep_recursion))
3614                return;
3615
3616        raw_local_irq_save(flags);
3617        check_flags(flags);
3618        current->lockdep_recursion = 1;
3619        trace_lock_release(lock, ip);
3620        __lock_release(lock, nested, ip);
3621        current->lockdep_recursion = 0;
3622        raw_local_irq_restore(flags);
3623}
3624EXPORT_SYMBOL_GPL(lock_release);
3625
3626int lock_is_held(struct lockdep_map *lock)
3627{
3628        unsigned long flags;
3629        int ret = 0;
3630
3631        if (unlikely(current->lockdep_recursion))
3632                return 1; /* avoid false negative lockdep_assert_held() */
3633
3634        raw_local_irq_save(flags);
3635        check_flags(flags);
3636
3637        current->lockdep_recursion = 1;
3638        ret = __lock_is_held(lock);
3639        current->lockdep_recursion = 0;
3640        raw_local_irq_restore(flags);
3641
3642        return ret;
3643}
3644EXPORT_SYMBOL_GPL(lock_is_held);
3645
3646void lockdep_set_current_reclaim_state(gfp_t gfp_mask)
3647{
3648        current->lockdep_reclaim_gfp = gfp_mask;
3649}
3650
3651void lockdep_clear_current_reclaim_state(void)
3652{
3653        current->lockdep_reclaim_gfp = 0;
3654}
3655
3656#ifdef CONFIG_LOCK_STAT
3657static int
3658print_lock_contention_bug(struct task_struct *curr, struct lockdep_map *lock,
3659                           unsigned long ip)
3660{
3661        if (!debug_locks_off())
3662                return 0;
3663        if (debug_locks_silent)
3664                return 0;
3665
3666        printk("\n");
3667        printk("=================================\n");
3668        printk("[ BUG: bad contention detected! ]\n");
3669        print_kernel_ident();
3670        printk("---------------------------------\n");
3671        printk("%s/%d is trying to contend lock (",
3672                curr->comm, task_pid_nr(curr));
3673        print_lockdep_cache(lock);
3674        printk(") at:\n");
3675        print_ip_sym(ip);
3676        printk("but there are no locks held!\n");
3677        printk("\nother info that might help us debug this:\n");
3678        lockdep_print_held_locks(curr);
3679
3680        printk("\nstack backtrace:\n");
3681        dump_stack();
3682
3683        return 0;
3684}
3685
3686static void
3687__lock_contended(struct lockdep_map *lock, unsigned long ip)
3688{
3689        struct task_struct *curr = current;
3690        struct held_lock *hlock, *prev_hlock;
3691        struct lock_class_stats *stats;
3692        unsigned int depth;
3693        int i, contention_point, contending_point;
3694
3695        depth = curr->lockdep_depth;
3696        /*
3697         * Whee, we contended on this lock, except it seems we're not
3698         * actually trying to acquire anything much at all..
3699         */
3700        if (DEBUG_LOCKS_WARN_ON(!depth))
3701                return;
3702
3703        prev_hlock = NULL;
3704        for (i = depth-1; i >= 0; i--) {
3705                hlock = curr->held_locks + i;
3706                /*
3707                 * We must not cross into another context:
3708                 */
3709                if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3710                        break;
3711                if (match_held_lock(hlock, lock))
3712                        goto found_it;
3713                prev_hlock = hlock;
3714        }
3715        print_lock_contention_bug(curr, lock, ip);
3716        return;
3717
3718found_it:
3719        if (hlock->instance != lock)
3720                return;
3721
3722        hlock->waittime_stamp = lockstat_clock();
3723
3724        contention_point = lock_point(hlock_class(hlock)->contention_point, ip);
3725        contending_point = lock_point(hlock_class(hlock)->contending_point,
3726                                      lock->ip);
3727
3728        stats = get_lock_stats(hlock_class(hlock));
3729        if (contention_point < LOCKSTAT_POINTS)
3730                stats->contention_point[contention_point]++;
3731        if (contending_point < LOCKSTAT_POINTS)
3732                stats->contending_point[contending_point]++;
3733        if (lock->cpu != smp_processor_id())
3734                stats->bounces[bounce_contended + !!hlock->read]++;
3735        put_lock_stats(stats);
3736}
3737
3738static void
3739__lock_acquired(struct lockdep_map *lock, unsigned long ip)
3740{
3741        struct task_struct *curr = current;
3742        struct held_lock *hlock, *prev_hlock;
3743        struct lock_class_stats *stats;
3744        unsigned int depth;
3745        u64 now, waittime = 0;
3746        int i, cpu;
3747
3748        depth = curr->lockdep_depth;
3749        /*
3750         * Yay, we acquired ownership of this lock we didn't try to
3751         * acquire, how the heck did that happen?
3752         */
3753        if (DEBUG_LOCKS_WARN_ON(!depth))
3754                return;
3755
3756        prev_hlock = NULL;
3757        for (i = depth-1; i >= 0; i--) {
3758                hlock = curr->held_locks + i;
3759                /*
3760                 * We must not cross into another context:
3761                 */
3762                if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3763                        break;
3764                if (match_held_lock(hlock, lock))
3765                        goto found_it;
3766                prev_hlock = hlock;
3767        }
3768        print_lock_contention_bug(curr, lock, _RET_IP_);
3769        return;
3770
3771found_it:
3772        if (hlock->instance != lock)
3773                return;
3774
3775        cpu = smp_processor_id();
3776        if (hlock->waittime_stamp) {
3777                now = lockstat_clock();
3778                waittime = now - hlock->waittime_stamp;
3779                hlock->holdtime_stamp = now;
3780        }
3781
3782        trace_lock_acquired(lock, ip);
3783
3784        stats = get_lock_stats(hlock_class(hlock));
3785        if (waittime) {
3786                if (hlock->read)
3787                        lock_time_inc(&stats->read_waittime, waittime);
3788                else
3789                        lock_time_inc(&stats->write_waittime, waittime);
3790        }
3791        if (lock->cpu != cpu)
3792                stats->bounces[bounce_acquired + !!hlock->read]++;
3793        put_lock_stats(stats);
3794
3795        lock->cpu = cpu;
3796        lock->ip = ip;
3797}
3798
3799void lock_contended(struct lockdep_map *lock, unsigned long ip)
3800{
3801        unsigned long flags;
3802
3803        if (unlikely(!lock_stat))
3804                return;
3805
3806        if (unlikely(current->lockdep_recursion))
3807                return;
3808
3809        raw_local_irq_save(flags);
3810        check_flags(flags);
3811        current->lockdep_recursion = 1;
3812        trace_lock_contended(lock, ip);
3813        __lock_contended(lock, ip);
3814        current->lockdep_recursion = 0;
3815        raw_local_irq_restore(flags);
3816}
3817EXPORT_SYMBOL_GPL(lock_contended);
3818
3819void lock_acquired(struct lockdep_map *lock, unsigned long ip)
3820{
3821        unsigned long flags;
3822
3823        if (unlikely(!lock_stat))
3824                return;
3825
3826        if (unlikely(current->lockdep_recursion))
3827                return;
3828
3829        raw_local_irq_save(flags);
3830        check_flags(flags);
3831        current->lockdep_recursion = 1;
3832        __lock_acquired(lock, ip);
3833        current->lockdep_recursion = 0;
3834        raw_local_irq_restore(flags);
3835}
3836EXPORT_SYMBOL_GPL(lock_acquired);
3837#endif
3838
3839/*
3840 * Used by the testsuite, sanitize the validator state
3841 * after a simulated failure:
3842 */
3843
3844void lockdep_reset(void)
3845{
3846        unsigned long flags;
3847        int i;
3848
3849        raw_local_irq_save(flags);
3850        current->curr_chain_key = 0;
3851        current->lockdep_depth = 0;
3852        current->lockdep_recursion = 0;
3853        memset(current->held_locks, 0, MAX_LOCK_DEPTH*sizeof(struct held_lock));
3854        nr_hardirq_chains = 0;
3855        nr_softirq_chains = 0;
3856        nr_process_chains = 0;
3857        debug_locks = 1;
3858        for (i = 0; i < CHAINHASH_SIZE; i++)
3859                INIT_LIST_HEAD(chainhash_table + i);
3860        raw_local_irq_restore(flags);
3861}
3862
3863static void zap_class(struct lock_class *class)
3864{
3865        int i;
3866
3867        /*
3868         * Remove all dependencies this lock is
3869         * involved in:
3870         */
3871        for (i = 0; i < nr_list_entries; i++) {
3872                if (list_entries[i].class == class)
3873                        list_del_rcu(&list_entries[i].entry);
3874        }
3875        /*
3876         * Unhash the class and remove it from the all_lock_classes list:
3877         */
3878        list_del_rcu(&class->hash_entry);
3879        list_del_rcu(&class->lock_entry);
3880
3881        class->key = NULL;
3882}
3883
3884static inline int within(const void *addr, void *start, unsigned long size)
3885{
3886        return addr >= start && addr < start + size;
3887}
3888
3889void lockdep_free_key_range(void *start, unsigned long size)
3890{
3891        struct lock_class *class, *next;
3892        struct list_head *head;
3893        unsigned long flags;
3894        int i;
3895        int locked;
3896
3897        raw_local_irq_save(flags);
3898        locked = graph_lock();
3899
3900        /*
3901         * Unhash all classes that were created by this module:
3902         */
3903        for (i = 0; i < CLASSHASH_SIZE; i++) {
3904                head = classhash_table + i;
3905                if (list_empty(head))
3906                        continue;
3907                list_for_each_entry_safe(class, next, head, hash_entry) {
3908                        if (within(class->key, start, size))
3909                                zap_class(class);
3910                        else if (within(class->name, start, size))
3911                                zap_class(class);
3912                }
3913        }
3914
3915        if (locked)
3916                graph_unlock();
3917        raw_local_irq_restore(flags);
3918}
3919
3920void lockdep_reset_lock(struct lockdep_map *lock)
3921{
3922        struct lock_class *class, *next;
3923        struct list_head *head;
3924        unsigned long flags;
3925        int i, j;
3926        int locked;
3927
3928        raw_local_irq_save(flags);
3929
3930        /*
3931         * Remove all classes this lock might have:
3932         */
3933        for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) {
3934                /*
3935                 * If the class exists we look it up and zap it:
3936                 */
3937                class = look_up_lock_class(lock, j);
3938                if (class)
3939                        zap_class(class);
3940        }
3941        /*
3942         * Debug check: in the end all mapped classes should
3943         * be gone.
3944         */
3945        locked = graph_lock();
3946        for (i = 0; i < CLASSHASH_SIZE; i++) {
3947                head = classhash_table + i;
3948                if (list_empty(head))
3949                        continue;
3950                list_for_each_entry_safe(class, next, head, hash_entry) {
3951                        int match = 0;
3952
3953                        for (j = 0; j < NR_LOCKDEP_CACHING_CLASSES; j++)
3954                                match |= class == lock->class_cache[j];
3955
3956                        if (unlikely(match)) {
3957                                if (debug_locks_off_graph_unlock()) {
3958                                        /*
3959                                         * We all just reset everything, how did it match?
3960                                         */
3961                                        WARN_ON(1);
3962                                }
3963                                goto out_restore;
3964                        }
3965                }
3966        }
3967        if (locked)
3968                graph_unlock();
3969
3970out_restore:
3971        raw_local_irq_restore(flags);
3972}
3973
3974void lockdep_init(void)
3975{
3976        int i;
3977
3978        /*
3979         * Some architectures have their own start_kernel()
3980         * code which calls lockdep_init(), while we also
3981         * call lockdep_init() from the start_kernel() itself,
3982         * and we want to initialize the hashes only once:
3983         */
3984        if (lockdep_initialized)
3985                return;
3986
3987        for (i = 0; i < CLASSHASH_SIZE; i++)
3988                INIT_LIST_HEAD(classhash_table + i);
3989
3990        for (i = 0; i < CHAINHASH_SIZE; i++)
3991                INIT_LIST_HEAD(chainhash_table + i);
3992
3993        lockdep_initialized = 1;
3994}
3995
3996void __init lockdep_info(void)
3997{
3998        printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");
3999
4000        printk("... MAX_LOCKDEP_SUBCLASSES:  %lu\n", MAX_LOCKDEP_SUBCLASSES);
4001        printk("... MAX_LOCK_DEPTH:          %lu\n", MAX_LOCK_DEPTH);
4002        printk("... MAX_LOCKDEP_KEYS:        %lu\n", MAX_LOCKDEP_KEYS);
4003        printk("... CLASSHASH_SIZE:          %lu\n", CLASSHASH_SIZE);
4004        printk("... MAX_LOCKDEP_ENTRIES:     %lu\n", MAX_LOCKDEP_ENTRIES);
4005        printk("... MAX_LOCKDEP_CHAINS:      %lu\n", MAX_LOCKDEP_CHAINS);
4006        printk("... CHAINHASH_SIZE:          %lu\n", CHAINHASH_SIZE);
4007
4008        printk(" memory used by lock dependency info: %lu kB\n",
4009                (sizeof(struct lock_class) * MAX_LOCKDEP_KEYS +
4010                sizeof(struct list_head) * CLASSHASH_SIZE +
4011                sizeof(struct lock_list) * MAX_LOCKDEP_ENTRIES +
4012                sizeof(struct lock_chain) * MAX_LOCKDEP_CHAINS +
4013                sizeof(struct list_head) * CHAINHASH_SIZE
4014#ifdef CONFIG_PROVE_LOCKING
4015                + sizeof(struct circular_queue)
4016#endif
4017                ) / 1024
4018                );
4019
4020        printk(" per task-struct memory footprint: %lu bytes\n",
4021                sizeof(struct held_lock) * MAX_LOCK_DEPTH);
4022
4023#ifdef CONFIG_DEBUG_LOCKDEP
4024        if (lockdep_init_error) {
4025                printk("WARNING: lockdep init error! lock-%s was acquired"
4026                        "before lockdep_init\n", lock_init_error);
4027                printk("Call stack leading to lockdep invocation was:\n");
4028                print_stack_trace(&lockdep_init_trace, 0);
4029        }
4030#endif
4031}
4032
4033static void
4034print_freed_lock_bug(struct task_struct *curr, const void *mem_from,
4035                     const void *mem_to, struct held_lock *hlock)
4036{
4037        if (!debug_locks_off())
4038                return;
4039        if (debug_locks_silent)
4040                return;
4041
4042        printk("\n");
4043        printk("=========================\n");
4044        printk("[ BUG: held lock freed! ]\n");
4045        print_kernel_ident();
4046        printk("-------------------------\n");
4047        printk("%s/%d is freeing memory %p-%p, with a lock still held there!\n",
4048                curr->comm, task_pid_nr(curr), mem_from, mem_to-1);
4049        print_lock(hlock);
4050        lockdep_print_held_locks(curr);
4051
4052        printk("\nstack backtrace:\n");
4053        dump_stack();
4054}
4055
4056static inline int not_in_range(const void* mem_from, unsigned long mem_len,
4057                                const void* lock_from, unsigned long lock_len)
4058{
4059        return lock_from + lock_len <= mem_from ||
4060                mem_from + mem_len <= lock_from;
4061}
4062
4063/*
4064 * Called when kernel memory is freed (or unmapped), or if a lock
4065 * is destroyed or reinitialized - this code checks whether there is
4066 * any held lock in the memory range of <from> to <to>:
4067 */
4068void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len)
4069{
4070        struct task_struct *curr = current;
4071        struct held_lock *hlock;
4072        unsigned long flags;
4073        int i;
4074
4075        if (unlikely(!debug_locks))
4076                return;
4077
4078        local_irq_save(flags);
4079        for (i = 0; i < curr->lockdep_depth; i++) {
4080                hlock = curr->held_locks + i;
4081
4082                if (not_in_range(mem_from, mem_len, hlock->instance,
4083                                        sizeof(*hlock->instance)))
4084                        continue;
4085
4086                print_freed_lock_bug(curr, mem_from, mem_from + mem_len, hlock);
4087                break;
4088        }
4089        local_irq_restore(flags);
4090}
4091EXPORT_SYMBOL_GPL(debug_check_no_locks_freed);
4092
4093static void print_held_locks_bug(struct task_struct *curr)
4094{
4095        if (!debug_locks_off())
4096                return;
4097        if (debug_locks_silent)
4098                return;
4099
4100        printk("\n");
4101        printk("=====================================\n");
4102        printk("[ BUG: lock held at task exit time! ]\n");
4103        print_kernel_ident();
4104        printk("-------------------------------------\n");
4105        printk("%s/%d is exiting with locks still held!\n",
4106                curr->comm, task_pid_nr(curr));
4107        lockdep_print_held_locks(curr);
4108
4109        printk("\nstack backtrace:\n");
4110        dump_stack();
4111}
4112
4113void debug_check_no_locks_held(struct task_struct *task)
4114{
4115        if (unlikely(task->lockdep_depth > 0))
4116                print_held_locks_bug(task);
4117}
4118
4119void debug_show_all_locks(void)
4120{
4121        struct task_struct *g, *p;
4122        int count = 10;
4123        int unlock = 1;
4124
4125        if (unlikely(!debug_locks)) {
4126                printk("INFO: lockdep is turned off.\n");
4127                return;
4128        }
4129        printk("\nShowing all locks held in the system:\n");
4130
4131        /*
4132         * Here we try to get the tasklist_lock as hard as possible,
4133         * if not successful after 2 seconds we ignore it (but keep
4134         * trying). This is to enable a debug printout even if a
4135         * tasklist_lock-holding task deadlocks or crashes.
4136         */
4137retry:
4138        if (!read_trylock(&tasklist_lock)) {
4139                if (count == 10)
4140                        printk("hm, tasklist_lock locked, retrying... ");
4141                if (count) {
4142                        count--;
4143                        printk(" #%d", 10-count);
4144                        mdelay(200);
4145                        goto retry;
4146                }
4147                printk(" ignoring it.\n");
4148                unlock = 0;
4149        } else {
4150                if (count != 10)
4151                        printk(KERN_CONT " locked it.\n");
4152        }
4153
4154        do_each_thread(g, p) {
4155                /*
4156                 * It's not reliable to print a task's held locks
4157                 * if it's not sleeping (or if it's not the current
4158                 * task):
4159                 */
4160                if (p->state == TASK_RUNNING && p != current)
4161                        continue;
4162                if (p->lockdep_depth)
4163                        lockdep_print_held_locks(p);
4164                if (!unlock)
4165                        if (read_trylock(&tasklist_lock))
4166                                unlock = 1;
4167        } while_each_thread(g, p);
4168
4169        printk("\n");
4170        printk("=============================================\n\n");
4171
4172        if (unlock)
4173                read_unlock(&tasklist_lock);
4174}
4175EXPORT_SYMBOL_GPL(debug_show_all_locks);
4176
4177/*
4178 * Careful: only use this function if you are sure that
4179 * the task cannot run in parallel!
4180 */
4181void debug_show_held_locks(struct task_struct *task)
4182{
4183        if (unlikely(!debug_locks)) {
4184                printk("INFO: lockdep is turned off.\n");
4185                return;
4186        }
4187        lockdep_print_held_locks(task);
4188}
4189EXPORT_SYMBOL_GPL(debug_show_held_locks);
4190
4191void lockdep_sys_exit(void)
4192{
4193        struct task_struct *curr = current;
4194
4195        if (unlikely(curr->lockdep_depth)) {
4196                if (!debug_locks_off())
4197                        return;
4198                printk("\n");
4199                printk("================================================\n");
4200                printk("[ BUG: lock held when returning to user space! ]\n");
4201                print_kernel_ident();
4202                printk("------------------------------------------------\n");
4203                printk("%s/%d is leaving the kernel with locks still held!\n",
4204                                curr->comm, curr->pid);
4205                lockdep_print_held_locks(curr);
4206        }
4207}
4208
4209void lockdep_rcu_suspicious(const char *file, const int line, const char *s)
4210{
4211        struct task_struct *curr = current;
4212
4213#ifndef CONFIG_PROVE_RCU_REPEATEDLY
4214        if (!debug_locks_off())
4215                return;
4216#endif /* #ifdef CONFIG_PROVE_RCU_REPEATEDLY */
4217        /* Note: the following can be executed concurrently, so be careful. */
4218        printk("\n");
4219        printk("===============================\n");
4220        printk("[ INFO: suspicious RCU usage. ]\n");
4221        print_kernel_ident();
4222        printk("-------------------------------\n");
4223        printk("%s:%d %s!\n", file, line, s);
4224        printk("\nother info that might help us debug this:\n\n");
4225        printk("\n%srcu_scheduler_active = %d, debug_locks = %d\n",
4226               !rcu_lockdep_current_cpu_online()
4227                        ? "RCU used illegally from offline CPU!\n"
4228                        : rcu_is_cpu_idle()
4229                                ? "RCU used illegally from idle CPU!\n"
4230                                : "",
4231               rcu_scheduler_active, debug_locks);
4232
4233        /*
4234         * If a CPU is in the RCU-free window in idle (ie: in the section
4235         * between rcu_idle_enter() and rcu_idle_exit(), then RCU
4236         * considers that CPU to be in an "extended quiescent state",
4237         * which means that RCU will be completely ignoring that CPU.
4238         * Therefore, rcu_read_lock() and friends have absolutely no
4239         * effect on a CPU running in that state. In other words, even if
4240         * such an RCU-idle CPU has called rcu_read_lock(), RCU might well
4241         * delete data structures out from under it.  RCU really has no
4242         * choice here: we need to keep an RCU-free window in idle where
4243         * the CPU may possibly enter into low power mode. This way we can
4244         * notice an extended quiescent state to other CPUs that started a grace
4245         * period. Otherwise we would delay any grace period as long as we run
4246         * in the idle task.
4247         *
4248         * So complain bitterly if someone does call rcu_read_lock(),
4249         * rcu_read_lock_bh() and so on from extended quiescent states.
4250         */
4251        if (rcu_is_cpu_idle())
4252                printk("RCU used illegally from extended quiescent state!\n");
4253
4254        lockdep_print_held_locks(curr);
4255        printk("\nstack backtrace:\n");
4256        dump_stack();
4257}
4258EXPORT_SYMBOL_GPL(lockdep_rcu_suspicious);
4259
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