lockdep: add lock_class information to lock_chain and output it
[linux-2.6.git] / kernel / lockdep.c
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 #include <linux/mutex.h>
29 #include <linux/sched.h>
30 #include <linux/delay.h>
31 #include <linux/module.h>
32 #include <linux/proc_fs.h>
33 #include <linux/seq_file.h>
34 #include <linux/spinlock.h>
35 #include <linux/kallsyms.h>
36 #include <linux/interrupt.h>
37 #include <linux/stacktrace.h>
38 #include <linux/debug_locks.h>
39 #include <linux/irqflags.h>
40 #include <linux/utsname.h>
41 #include <linux/hash.h>
42
43 #include <asm/sections.h>
44
45 #include "lockdep_internals.h"
46
47 #ifdef CONFIG_PROVE_LOCKING
48 int prove_locking = 1;
49 module_param(prove_locking, int, 0644);
50 #else
51 #define prove_locking 0
52 #endif
53
54 #ifdef CONFIG_LOCK_STAT
55 int lock_stat = 1;
56 module_param(lock_stat, int, 0644);
57 #else
58 #define lock_stat 0
59 #endif
60
61 /*
62  * lockdep_lock: protects the lockdep graph, the hashes and the
63  *               class/list/hash allocators.
64  *
65  * This is one of the rare exceptions where it's justified
66  * to use a raw spinlock - we really dont want the spinlock
67  * code to recurse back into the lockdep code...
68  */
69 static raw_spinlock_t lockdep_lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
70
71 static int graph_lock(void)
72 {
73         __raw_spin_lock(&lockdep_lock);
74         /*
75          * Make sure that if another CPU detected a bug while
76          * walking the graph we dont change it (while the other
77          * CPU is busy printing out stuff with the graph lock
78          * dropped already)
79          */
80         if (!debug_locks) {
81                 __raw_spin_unlock(&lockdep_lock);
82                 return 0;
83         }
84         return 1;
85 }
86
87 static inline int graph_unlock(void)
88 {
89         if (debug_locks && !__raw_spin_is_locked(&lockdep_lock))
90                 return DEBUG_LOCKS_WARN_ON(1);
91
92         __raw_spin_unlock(&lockdep_lock);
93         return 0;
94 }
95
96 /*
97  * Turn lock debugging off and return with 0 if it was off already,
98  * and also release the graph lock:
99  */
100 static inline int debug_locks_off_graph_unlock(void)
101 {
102         int ret = debug_locks_off();
103
104         __raw_spin_unlock(&lockdep_lock);
105
106         return ret;
107 }
108
109 static int lockdep_initialized;
110
111 unsigned long nr_list_entries;
112 static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES];
113
114 /*
115  * All data structures here are protected by the global debug_lock.
116  *
117  * Mutex key structs only get allocated, once during bootup, and never
118  * get freed - this significantly simplifies the debugging code.
119  */
120 unsigned long nr_lock_classes;
121 static struct lock_class lock_classes[MAX_LOCKDEP_KEYS];
122
123 #ifdef CONFIG_LOCK_STAT
124 static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS], lock_stats);
125
126 static int lock_contention_point(struct lock_class *class, unsigned long ip)
127 {
128         int i;
129
130         for (i = 0; i < ARRAY_SIZE(class->contention_point); i++) {
131                 if (class->contention_point[i] == 0) {
132                         class->contention_point[i] = ip;
133                         break;
134                 }
135                 if (class->contention_point[i] == ip)
136                         break;
137         }
138
139         return i;
140 }
141
142 static void lock_time_inc(struct lock_time *lt, s64 time)
143 {
144         if (time > lt->max)
145                 lt->max = time;
146
147         if (time < lt->min || !lt->min)
148                 lt->min = time;
149
150         lt->total += time;
151         lt->nr++;
152 }
153
154 static inline void lock_time_add(struct lock_time *src, struct lock_time *dst)
155 {
156         dst->min += src->min;
157         dst->max += src->max;
158         dst->total += src->total;
159         dst->nr += src->nr;
160 }
161
162 struct lock_class_stats lock_stats(struct lock_class *class)
163 {
164         struct lock_class_stats stats;
165         int cpu, i;
166
167         memset(&stats, 0, sizeof(struct lock_class_stats));
168         for_each_possible_cpu(cpu) {
169                 struct lock_class_stats *pcs =
170                         &per_cpu(lock_stats, cpu)[class - lock_classes];
171
172                 for (i = 0; i < ARRAY_SIZE(stats.contention_point); i++)
173                         stats.contention_point[i] += pcs->contention_point[i];
174
175                 lock_time_add(&pcs->read_waittime, &stats.read_waittime);
176                 lock_time_add(&pcs->write_waittime, &stats.write_waittime);
177
178                 lock_time_add(&pcs->read_holdtime, &stats.read_holdtime);
179                 lock_time_add(&pcs->write_holdtime, &stats.write_holdtime);
180
181                 for (i = 0; i < ARRAY_SIZE(stats.bounces); i++)
182                         stats.bounces[i] += pcs->bounces[i];
183         }
184
185         return stats;
186 }
187
188 void clear_lock_stats(struct lock_class *class)
189 {
190         int cpu;
191
192         for_each_possible_cpu(cpu) {
193                 struct lock_class_stats *cpu_stats =
194                         &per_cpu(lock_stats, cpu)[class - lock_classes];
195
196                 memset(cpu_stats, 0, sizeof(struct lock_class_stats));
197         }
198         memset(class->contention_point, 0, sizeof(class->contention_point));
199 }
200
201 static struct lock_class_stats *get_lock_stats(struct lock_class *class)
202 {
203         return &get_cpu_var(lock_stats)[class - lock_classes];
204 }
205
206 static void put_lock_stats(struct lock_class_stats *stats)
207 {
208         put_cpu_var(lock_stats);
209 }
210
211 static void lock_release_holdtime(struct held_lock *hlock)
212 {
213         struct lock_class_stats *stats;
214         s64 holdtime;
215
216         if (!lock_stat)
217                 return;
218
219         holdtime = sched_clock() - hlock->holdtime_stamp;
220
221         stats = get_lock_stats(hlock->class);
222         if (hlock->read)
223                 lock_time_inc(&stats->read_holdtime, holdtime);
224         else
225                 lock_time_inc(&stats->write_holdtime, holdtime);
226         put_lock_stats(stats);
227 }
228 #else
229 static inline void lock_release_holdtime(struct held_lock *hlock)
230 {
231 }
232 #endif
233
234 /*
235  * We keep a global list of all lock classes. The list only grows,
236  * never shrinks. The list is only accessed with the lockdep
237  * spinlock lock held.
238  */
239 LIST_HEAD(all_lock_classes);
240
241 /*
242  * The lockdep classes are in a hash-table as well, for fast lookup:
243  */
244 #define CLASSHASH_BITS          (MAX_LOCKDEP_KEYS_BITS - 1)
245 #define CLASSHASH_SIZE          (1UL << CLASSHASH_BITS)
246 #define __classhashfn(key)      hash_long((unsigned long)key, CLASSHASH_BITS)
247 #define classhashentry(key)     (classhash_table + __classhashfn((key)))
248
249 static struct list_head classhash_table[CLASSHASH_SIZE];
250
251 /*
252  * We put the lock dependency chains into a hash-table as well, to cache
253  * their existence:
254  */
255 #define CHAINHASH_BITS          (MAX_LOCKDEP_CHAINS_BITS-1)
256 #define CHAINHASH_SIZE          (1UL << CHAINHASH_BITS)
257 #define __chainhashfn(chain)    hash_long(chain, CHAINHASH_BITS)
258 #define chainhashentry(chain)   (chainhash_table + __chainhashfn((chain)))
259
260 static struct list_head chainhash_table[CHAINHASH_SIZE];
261
262 /*
263  * The hash key of the lock dependency chains is a hash itself too:
264  * it's a hash of all locks taken up to that lock, including that lock.
265  * It's a 64-bit hash, because it's important for the keys to be
266  * unique.
267  */
268 #define iterate_chain_key(key1, key2) \
269         (((key1) << MAX_LOCKDEP_KEYS_BITS) ^ \
270         ((key1) >> (64-MAX_LOCKDEP_KEYS_BITS)) ^ \
271         (key2))
272
273 void lockdep_off(void)
274 {
275         current->lockdep_recursion++;
276 }
277
278 EXPORT_SYMBOL(lockdep_off);
279
280 void lockdep_on(void)
281 {
282         current->lockdep_recursion--;
283 }
284
285 EXPORT_SYMBOL(lockdep_on);
286
287 /*
288  * Debugging switches:
289  */
290
291 #define VERBOSE                 0
292 #define VERY_VERBOSE            0
293
294 #if VERBOSE
295 # define HARDIRQ_VERBOSE        1
296 # define SOFTIRQ_VERBOSE        1
297 #else
298 # define HARDIRQ_VERBOSE        0
299 # define SOFTIRQ_VERBOSE        0
300 #endif
301
302 #if VERBOSE || HARDIRQ_VERBOSE || SOFTIRQ_VERBOSE
303 /*
304  * Quick filtering for interesting events:
305  */
306 static int class_filter(struct lock_class *class)
307 {
308 #if 0
309         /* Example */
310         if (class->name_version == 1 &&
311                         !strcmp(class->name, "lockname"))
312                 return 1;
313         if (class->name_version == 1 &&
314                         !strcmp(class->name, "&struct->lockfield"))
315                 return 1;
316 #endif
317         /* Filter everything else. 1 would be to allow everything else */
318         return 0;
319 }
320 #endif
321
322 static int verbose(struct lock_class *class)
323 {
324 #if VERBOSE
325         return class_filter(class);
326 #endif
327         return 0;
328 }
329
330 /*
331  * Stack-trace: tightly packed array of stack backtrace
332  * addresses. Protected by the graph_lock.
333  */
334 unsigned long nr_stack_trace_entries;
335 static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];
336
337 static int save_trace(struct stack_trace *trace)
338 {
339         trace->nr_entries = 0;
340         trace->max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries;
341         trace->entries = stack_trace + nr_stack_trace_entries;
342
343         trace->skip = 3;
344
345         save_stack_trace(trace);
346
347         trace->max_entries = trace->nr_entries;
348
349         nr_stack_trace_entries += trace->nr_entries;
350
351         if (nr_stack_trace_entries == MAX_STACK_TRACE_ENTRIES) {
352                 if (!debug_locks_off_graph_unlock())
353                         return 0;
354
355                 printk("BUG: MAX_STACK_TRACE_ENTRIES too low!\n");
356                 printk("turning off the locking correctness validator.\n");
357                 dump_stack();
358
359                 return 0;
360         }
361
362         return 1;
363 }
364
365 unsigned int nr_hardirq_chains;
366 unsigned int nr_softirq_chains;
367 unsigned int nr_process_chains;
368 unsigned int max_lockdep_depth;
369 unsigned int max_recursion_depth;
370
371 #ifdef CONFIG_DEBUG_LOCKDEP
372 /*
373  * We cannot printk in early bootup code. Not even early_printk()
374  * might work. So we mark any initialization errors and printk
375  * about it later on, in lockdep_info().
376  */
377 static int lockdep_init_error;
378 static unsigned long lockdep_init_trace_data[20];
379 static struct stack_trace lockdep_init_trace = {
380         .max_entries = ARRAY_SIZE(lockdep_init_trace_data),
381         .entries = lockdep_init_trace_data,
382 };
383
384 /*
385  * Various lockdep statistics:
386  */
387 atomic_t chain_lookup_hits;
388 atomic_t chain_lookup_misses;
389 atomic_t hardirqs_on_events;
390 atomic_t hardirqs_off_events;
391 atomic_t redundant_hardirqs_on;
392 atomic_t redundant_hardirqs_off;
393 atomic_t softirqs_on_events;
394 atomic_t softirqs_off_events;
395 atomic_t redundant_softirqs_on;
396 atomic_t redundant_softirqs_off;
397 atomic_t nr_unused_locks;
398 atomic_t nr_cyclic_checks;
399 atomic_t nr_cyclic_check_recursions;
400 atomic_t nr_find_usage_forwards_checks;
401 atomic_t nr_find_usage_forwards_recursions;
402 atomic_t nr_find_usage_backwards_checks;
403 atomic_t nr_find_usage_backwards_recursions;
404 # define debug_atomic_inc(ptr)          atomic_inc(ptr)
405 # define debug_atomic_dec(ptr)          atomic_dec(ptr)
406 # define debug_atomic_read(ptr)         atomic_read(ptr)
407 #else
408 # define debug_atomic_inc(ptr)          do { } while (0)
409 # define debug_atomic_dec(ptr)          do { } while (0)
410 # define debug_atomic_read(ptr)         0
411 #endif
412
413 /*
414  * Locking printouts:
415  */
416
417 static const char *usage_str[] =
418 {
419         [LOCK_USED] =                   "initial-use ",
420         [LOCK_USED_IN_HARDIRQ] =        "in-hardirq-W",
421         [LOCK_USED_IN_SOFTIRQ] =        "in-softirq-W",
422         [LOCK_ENABLED_SOFTIRQS] =       "softirq-on-W",
423         [LOCK_ENABLED_HARDIRQS] =       "hardirq-on-W",
424         [LOCK_USED_IN_HARDIRQ_READ] =   "in-hardirq-R",
425         [LOCK_USED_IN_SOFTIRQ_READ] =   "in-softirq-R",
426         [LOCK_ENABLED_SOFTIRQS_READ] =  "softirq-on-R",
427         [LOCK_ENABLED_HARDIRQS_READ] =  "hardirq-on-R",
428 };
429
430 const char * __get_key_name(struct lockdep_subclass_key *key, char *str)
431 {
432         return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str);
433 }
434
435 void
436 get_usage_chars(struct lock_class *class, char *c1, char *c2, char *c3, char *c4)
437 {
438         *c1 = '.', *c2 = '.', *c3 = '.', *c4 = '.';
439
440         if (class->usage_mask & LOCKF_USED_IN_HARDIRQ)
441                 *c1 = '+';
442         else
443                 if (class->usage_mask & LOCKF_ENABLED_HARDIRQS)
444                         *c1 = '-';
445
446         if (class->usage_mask & LOCKF_USED_IN_SOFTIRQ)
447                 *c2 = '+';
448         else
449                 if (class->usage_mask & LOCKF_ENABLED_SOFTIRQS)
450                         *c2 = '-';
451
452         if (class->usage_mask & LOCKF_ENABLED_HARDIRQS_READ)
453                 *c3 = '-';
454         if (class->usage_mask & LOCKF_USED_IN_HARDIRQ_READ) {
455                 *c3 = '+';
456                 if (class->usage_mask & LOCKF_ENABLED_HARDIRQS_READ)
457                         *c3 = '?';
458         }
459
460         if (class->usage_mask & LOCKF_ENABLED_SOFTIRQS_READ)
461                 *c4 = '-';
462         if (class->usage_mask & LOCKF_USED_IN_SOFTIRQ_READ) {
463                 *c4 = '+';
464                 if (class->usage_mask & LOCKF_ENABLED_SOFTIRQS_READ)
465                         *c4 = '?';
466         }
467 }
468
469 static void print_lock_name(struct lock_class *class)
470 {
471         char str[KSYM_NAME_LEN], c1, c2, c3, c4;
472         const char *name;
473
474         get_usage_chars(class, &c1, &c2, &c3, &c4);
475
476         name = class->name;
477         if (!name) {
478                 name = __get_key_name(class->key, str);
479                 printk(" (%s", name);
480         } else {
481                 printk(" (%s", name);
482                 if (class->name_version > 1)
483                         printk("#%d", class->name_version);
484                 if (class->subclass)
485                         printk("/%d", class->subclass);
486         }
487         printk("){%c%c%c%c}", c1, c2, c3, c4);
488 }
489
490 static void print_lockdep_cache(struct lockdep_map *lock)
491 {
492         const char *name;
493         char str[KSYM_NAME_LEN];
494
495         name = lock->name;
496         if (!name)
497                 name = __get_key_name(lock->key->subkeys, str);
498
499         printk("%s", name);
500 }
501
502 static void print_lock(struct held_lock *hlock)
503 {
504         print_lock_name(hlock->class);
505         printk(", at: ");
506         print_ip_sym(hlock->acquire_ip);
507 }
508
509 static void lockdep_print_held_locks(struct task_struct *curr)
510 {
511         int i, depth = curr->lockdep_depth;
512
513         if (!depth) {
514                 printk("no locks held by %s/%d.\n", curr->comm, task_pid_nr(curr));
515                 return;
516         }
517         printk("%d lock%s held by %s/%d:\n",
518                 depth, depth > 1 ? "s" : "", curr->comm, task_pid_nr(curr));
519
520         for (i = 0; i < depth; i++) {
521                 printk(" #%d: ", i);
522                 print_lock(curr->held_locks + i);
523         }
524 }
525
526 static void print_lock_class_header(struct lock_class *class, int depth)
527 {
528         int bit;
529
530         printk("%*s->", depth, "");
531         print_lock_name(class);
532         printk(" ops: %lu", class->ops);
533         printk(" {\n");
534
535         for (bit = 0; bit < LOCK_USAGE_STATES; bit++) {
536                 if (class->usage_mask & (1 << bit)) {
537                         int len = depth;
538
539                         len += printk("%*s   %s", depth, "", usage_str[bit]);
540                         len += printk(" at:\n");
541                         print_stack_trace(class->usage_traces + bit, len);
542                 }
543         }
544         printk("%*s }\n", depth, "");
545
546         printk("%*s ... key      at: ",depth,"");
547         print_ip_sym((unsigned long)class->key);
548 }
549
550 /*
551  * printk all lock dependencies starting at <entry>:
552  */
553 static void print_lock_dependencies(struct lock_class *class, int depth)
554 {
555         struct lock_list *entry;
556
557         if (DEBUG_LOCKS_WARN_ON(depth >= 20))
558                 return;
559
560         print_lock_class_header(class, depth);
561
562         list_for_each_entry(entry, &class->locks_after, entry) {
563                 if (DEBUG_LOCKS_WARN_ON(!entry->class))
564                         return;
565
566                 print_lock_dependencies(entry->class, depth + 1);
567
568                 printk("%*s ... acquired at:\n",depth,"");
569                 print_stack_trace(&entry->trace, 2);
570                 printk("\n");
571         }
572 }
573
574 static void print_kernel_version(void)
575 {
576         printk("%s %.*s\n", init_utsname()->release,
577                 (int)strcspn(init_utsname()->version, " "),
578                 init_utsname()->version);
579 }
580
581 static int very_verbose(struct lock_class *class)
582 {
583 #if VERY_VERBOSE
584         return class_filter(class);
585 #endif
586         return 0;
587 }
588
589 /*
590  * Is this the address of a static object:
591  */
592 static int static_obj(void *obj)
593 {
594         unsigned long start = (unsigned long) &_stext,
595                       end   = (unsigned long) &_end,
596                       addr  = (unsigned long) obj;
597 #ifdef CONFIG_SMP
598         int i;
599 #endif
600
601         /*
602          * static variable?
603          */
604         if ((addr >= start) && (addr < end))
605                 return 1;
606
607 #ifdef CONFIG_SMP
608         /*
609          * percpu var?
610          */
611         for_each_possible_cpu(i) {
612                 start = (unsigned long) &__per_cpu_start + per_cpu_offset(i);
613                 end   = (unsigned long) &__per_cpu_start + PERCPU_ENOUGH_ROOM
614                                         + per_cpu_offset(i);
615
616                 if ((addr >= start) && (addr < end))
617                         return 1;
618         }
619 #endif
620
621         /*
622          * module var?
623          */
624         return is_module_address(addr);
625 }
626
627 /*
628  * To make lock name printouts unique, we calculate a unique
629  * class->name_version generation counter:
630  */
631 static int count_matching_names(struct lock_class *new_class)
632 {
633         struct lock_class *class;
634         int count = 0;
635
636         if (!new_class->name)
637                 return 0;
638
639         list_for_each_entry(class, &all_lock_classes, lock_entry) {
640                 if (new_class->key - new_class->subclass == class->key)
641                         return class->name_version;
642                 if (class->name && !strcmp(class->name, new_class->name))
643                         count = max(count, class->name_version);
644         }
645
646         return count + 1;
647 }
648
649 /*
650  * Register a lock's class in the hash-table, if the class is not present
651  * yet. Otherwise we look it up. We cache the result in the lock object
652  * itself, so actual lookup of the hash should be once per lock object.
653  */
654 static inline struct lock_class *
655 look_up_lock_class(struct lockdep_map *lock, unsigned int subclass)
656 {
657         struct lockdep_subclass_key *key;
658         struct list_head *hash_head;
659         struct lock_class *class;
660
661 #ifdef CONFIG_DEBUG_LOCKDEP
662         /*
663          * If the architecture calls into lockdep before initializing
664          * the hashes then we'll warn about it later. (we cannot printk
665          * right now)
666          */
667         if (unlikely(!lockdep_initialized)) {
668                 lockdep_init();
669                 lockdep_init_error = 1;
670                 save_stack_trace(&lockdep_init_trace);
671         }
672 #endif
673
674         /*
675          * Static locks do not have their class-keys yet - for them the key
676          * is the lock object itself:
677          */
678         if (unlikely(!lock->key))
679                 lock->key = (void *)lock;
680
681         /*
682          * NOTE: the class-key must be unique. For dynamic locks, a static
683          * lock_class_key variable is passed in through the mutex_init()
684          * (or spin_lock_init()) call - which acts as the key. For static
685          * locks we use the lock object itself as the key.
686          */
687         BUILD_BUG_ON(sizeof(struct lock_class_key) >
688                         sizeof(struct lockdep_map));
689
690         key = lock->key->subkeys + subclass;
691
692         hash_head = classhashentry(key);
693
694         /*
695          * We can walk the hash lockfree, because the hash only
696          * grows, and we are careful when adding entries to the end:
697          */
698         list_for_each_entry(class, hash_head, hash_entry) {
699                 if (class->key == key) {
700                         WARN_ON_ONCE(class->name != lock->name);
701                         return class;
702                 }
703         }
704
705         return NULL;
706 }
707
708 /*
709  * Register a lock's class in the hash-table, if the class is not present
710  * yet. Otherwise we look it up. We cache the result in the lock object
711  * itself, so actual lookup of the hash should be once per lock object.
712  */
713 static inline struct lock_class *
714 register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
715 {
716         struct lockdep_subclass_key *key;
717         struct list_head *hash_head;
718         struct lock_class *class;
719         unsigned long flags;
720
721         class = look_up_lock_class(lock, subclass);
722         if (likely(class))
723                 return class;
724
725         /*
726          * Debug-check: all keys must be persistent!
727          */
728         if (!static_obj(lock->key)) {
729                 debug_locks_off();
730                 printk("INFO: trying to register non-static key.\n");
731                 printk("the code is fine but needs lockdep annotation.\n");
732                 printk("turning off the locking correctness validator.\n");
733                 dump_stack();
734
735                 return NULL;
736         }
737
738         key = lock->key->subkeys + subclass;
739         hash_head = classhashentry(key);
740
741         raw_local_irq_save(flags);
742         if (!graph_lock()) {
743                 raw_local_irq_restore(flags);
744                 return NULL;
745         }
746         /*
747          * We have to do the hash-walk again, to avoid races
748          * with another CPU:
749          */
750         list_for_each_entry(class, hash_head, hash_entry)
751                 if (class->key == key)
752                         goto out_unlock_set;
753         /*
754          * Allocate a new key from the static array, and add it to
755          * the hash:
756          */
757         if (nr_lock_classes >= MAX_LOCKDEP_KEYS) {
758                 if (!debug_locks_off_graph_unlock()) {
759                         raw_local_irq_restore(flags);
760                         return NULL;
761                 }
762                 raw_local_irq_restore(flags);
763
764                 printk("BUG: MAX_LOCKDEP_KEYS too low!\n");
765                 printk("turning off the locking correctness validator.\n");
766                 return NULL;
767         }
768         class = lock_classes + nr_lock_classes++;
769         debug_atomic_inc(&nr_unused_locks);
770         class->key = key;
771         class->name = lock->name;
772         class->subclass = subclass;
773         INIT_LIST_HEAD(&class->lock_entry);
774         INIT_LIST_HEAD(&class->locks_before);
775         INIT_LIST_HEAD(&class->locks_after);
776         class->name_version = count_matching_names(class);
777         /*
778          * We use RCU's safe list-add method to make
779          * parallel walking of the hash-list safe:
780          */
781         list_add_tail_rcu(&class->hash_entry, hash_head);
782         /*
783          * Add it to the global list of classes:
784          */
785         list_add_tail_rcu(&class->lock_entry, &all_lock_classes);
786
787         if (verbose(class)) {
788                 graph_unlock();
789                 raw_local_irq_restore(flags);
790
791                 printk("\nnew class %p: %s", class->key, class->name);
792                 if (class->name_version > 1)
793                         printk("#%d", class->name_version);
794                 printk("\n");
795                 dump_stack();
796
797                 raw_local_irq_save(flags);
798                 if (!graph_lock()) {
799                         raw_local_irq_restore(flags);
800                         return NULL;
801                 }
802         }
803 out_unlock_set:
804         graph_unlock();
805         raw_local_irq_restore(flags);
806
807         if (!subclass || force)
808                 lock->class_cache = class;
809
810         if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))
811                 return NULL;
812
813         return class;
814 }
815
816 #ifdef CONFIG_PROVE_LOCKING
817 /*
818  * Allocate a lockdep entry. (assumes the graph_lock held, returns
819  * with NULL on failure)
820  */
821 static struct lock_list *alloc_list_entry(void)
822 {
823         if (nr_list_entries >= MAX_LOCKDEP_ENTRIES) {
824                 if (!debug_locks_off_graph_unlock())
825                         return NULL;
826
827                 printk("BUG: MAX_LOCKDEP_ENTRIES too low!\n");
828                 printk("turning off the locking correctness validator.\n");
829                 return NULL;
830         }
831         return list_entries + nr_list_entries++;
832 }
833
834 /*
835  * Add a new dependency to the head of the list:
836  */
837 static int add_lock_to_list(struct lock_class *class, struct lock_class *this,
838                             struct list_head *head, unsigned long ip, int distance)
839 {
840         struct lock_list *entry;
841         /*
842          * Lock not present yet - get a new dependency struct and
843          * add it to the list:
844          */
845         entry = alloc_list_entry();
846         if (!entry)
847                 return 0;
848
849         entry->class = this;
850         entry->distance = distance;
851         if (!save_trace(&entry->trace))
852                 return 0;
853
854         /*
855          * Since we never remove from the dependency list, the list can
856          * be walked lockless by other CPUs, it's only allocation
857          * that must be protected by the spinlock. But this also means
858          * we must make new entries visible only once writes to the
859          * entry become visible - hence the RCU op:
860          */
861         list_add_tail_rcu(&entry->entry, head);
862
863         return 1;
864 }
865
866 /*
867  * Recursive, forwards-direction lock-dependency checking, used for
868  * both noncyclic checking and for hardirq-unsafe/softirq-unsafe
869  * checking.
870  *
871  * (to keep the stackframe of the recursive functions small we
872  *  use these global variables, and we also mark various helper
873  *  functions as noinline.)
874  */
875 static struct held_lock *check_source, *check_target;
876
877 /*
878  * Print a dependency chain entry (this is only done when a deadlock
879  * has been detected):
880  */
881 static noinline int
882 print_circular_bug_entry(struct lock_list *target, unsigned int depth)
883 {
884         if (debug_locks_silent)
885                 return 0;
886         printk("\n-> #%u", depth);
887         print_lock_name(target->class);
888         printk(":\n");
889         print_stack_trace(&target->trace, 6);
890
891         return 0;
892 }
893
894 /*
895  * When a circular dependency is detected, print the
896  * header first:
897  */
898 static noinline int
899 print_circular_bug_header(struct lock_list *entry, unsigned int depth)
900 {
901         struct task_struct *curr = current;
902
903         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
904                 return 0;
905
906         printk("\n=======================================================\n");
907         printk(  "[ INFO: possible circular locking dependency detected ]\n");
908         print_kernel_version();
909         printk(  "-------------------------------------------------------\n");
910         printk("%s/%d is trying to acquire lock:\n",
911                 curr->comm, task_pid_nr(curr));
912         print_lock(check_source);
913         printk("\nbut task is already holding lock:\n");
914         print_lock(check_target);
915         printk("\nwhich lock already depends on the new lock.\n\n");
916         printk("\nthe existing dependency chain (in reverse order) is:\n");
917
918         print_circular_bug_entry(entry, depth);
919
920         return 0;
921 }
922
923 static noinline int print_circular_bug_tail(void)
924 {
925         struct task_struct *curr = current;
926         struct lock_list this;
927
928         if (debug_locks_silent)
929                 return 0;
930
931         this.class = check_source->class;
932         if (!save_trace(&this.trace))
933                 return 0;
934
935         print_circular_bug_entry(&this, 0);
936
937         printk("\nother info that might help us debug this:\n\n");
938         lockdep_print_held_locks(curr);
939
940         printk("\nstack backtrace:\n");
941         dump_stack();
942
943         return 0;
944 }
945
946 #define RECURSION_LIMIT 40
947
948 static int noinline print_infinite_recursion_bug(void)
949 {
950         if (!debug_locks_off_graph_unlock())
951                 return 0;
952
953         WARN_ON(1);
954
955         return 0;
956 }
957
958 /*
959  * Prove that the dependency graph starting at <entry> can not
960  * lead to <target>. Print an error and return 0 if it does.
961  */
962 static noinline int
963 check_noncircular(struct lock_class *source, unsigned int depth)
964 {
965         struct lock_list *entry;
966
967         debug_atomic_inc(&nr_cyclic_check_recursions);
968         if (depth > max_recursion_depth)
969                 max_recursion_depth = depth;
970         if (depth >= RECURSION_LIMIT)
971                 return print_infinite_recursion_bug();
972         /*
973          * Check this lock's dependency list:
974          */
975         list_for_each_entry(entry, &source->locks_after, entry) {
976                 if (entry->class == check_target->class)
977                         return print_circular_bug_header(entry, depth+1);
978                 debug_atomic_inc(&nr_cyclic_checks);
979                 if (!check_noncircular(entry->class, depth+1))
980                         return print_circular_bug_entry(entry, depth+1);
981         }
982         return 1;
983 }
984
985 #ifdef CONFIG_TRACE_IRQFLAGS
986 /*
987  * Forwards and backwards subgraph searching, for the purposes of
988  * proving that two subgraphs can be connected by a new dependency
989  * without creating any illegal irq-safe -> irq-unsafe lock dependency.
990  */
991 static enum lock_usage_bit find_usage_bit;
992 static struct lock_class *forwards_match, *backwards_match;
993
994 /*
995  * Find a node in the forwards-direction dependency sub-graph starting
996  * at <source> that matches <find_usage_bit>.
997  *
998  * Return 2 if such a node exists in the subgraph, and put that node
999  * into <forwards_match>.
1000  *
1001  * Return 1 otherwise and keep <forwards_match> unchanged.
1002  * Return 0 on error.
1003  */
1004 static noinline int
1005 find_usage_forwards(struct lock_class *source, unsigned int depth)
1006 {
1007         struct lock_list *entry;
1008         int ret;
1009
1010         if (depth > max_recursion_depth)
1011                 max_recursion_depth = depth;
1012         if (depth >= RECURSION_LIMIT)
1013                 return print_infinite_recursion_bug();
1014
1015         debug_atomic_inc(&nr_find_usage_forwards_checks);
1016         if (source->usage_mask & (1 << find_usage_bit)) {
1017                 forwards_match = source;
1018                 return 2;
1019         }
1020
1021         /*
1022          * Check this lock's dependency list:
1023          */
1024         list_for_each_entry(entry, &source->locks_after, entry) {
1025                 debug_atomic_inc(&nr_find_usage_forwards_recursions);
1026                 ret = find_usage_forwards(entry->class, depth+1);
1027                 if (ret == 2 || ret == 0)
1028                         return ret;
1029         }
1030         return 1;
1031 }
1032
1033 /*
1034  * Find a node in the backwards-direction dependency sub-graph starting
1035  * at <source> that matches <find_usage_bit>.
1036  *
1037  * Return 2 if such a node exists in the subgraph, and put that node
1038  * into <backwards_match>.
1039  *
1040  * Return 1 otherwise and keep <backwards_match> unchanged.
1041  * Return 0 on error.
1042  */
1043 static noinline int
1044 find_usage_backwards(struct lock_class *source, unsigned int depth)
1045 {
1046         struct lock_list *entry;
1047         int ret;
1048
1049         if (!__raw_spin_is_locked(&lockdep_lock))
1050                 return DEBUG_LOCKS_WARN_ON(1);
1051
1052         if (depth > max_recursion_depth)
1053                 max_recursion_depth = depth;
1054         if (depth >= RECURSION_LIMIT)
1055                 return print_infinite_recursion_bug();
1056
1057         debug_atomic_inc(&nr_find_usage_backwards_checks);
1058         if (source->usage_mask & (1 << find_usage_bit)) {
1059                 backwards_match = source;
1060                 return 2;
1061         }
1062
1063         /*
1064          * Check this lock's dependency list:
1065          */
1066         list_for_each_entry(entry, &source->locks_before, entry) {
1067                 debug_atomic_inc(&nr_find_usage_backwards_recursions);
1068                 ret = find_usage_backwards(entry->class, depth+1);
1069                 if (ret == 2 || ret == 0)
1070                         return ret;
1071         }
1072         return 1;
1073 }
1074
1075 static int
1076 print_bad_irq_dependency(struct task_struct *curr,
1077                          struct held_lock *prev,
1078                          struct held_lock *next,
1079                          enum lock_usage_bit bit1,
1080                          enum lock_usage_bit bit2,
1081                          const char *irqclass)
1082 {
1083         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1084                 return 0;
1085
1086         printk("\n======================================================\n");
1087         printk(  "[ INFO: %s-safe -> %s-unsafe lock order detected ]\n",
1088                 irqclass, irqclass);
1089         print_kernel_version();
1090         printk(  "------------------------------------------------------\n");
1091         printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
1092                 curr->comm, task_pid_nr(curr),
1093                 curr->hardirq_context, hardirq_count() >> HARDIRQ_SHIFT,
1094                 curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT,
1095                 curr->hardirqs_enabled,
1096                 curr->softirqs_enabled);
1097         print_lock(next);
1098
1099         printk("\nand this task is already holding:\n");
1100         print_lock(prev);
1101         printk("which would create a new lock dependency:\n");
1102         print_lock_name(prev->class);
1103         printk(" ->");
1104         print_lock_name(next->class);
1105         printk("\n");
1106
1107         printk("\nbut this new dependency connects a %s-irq-safe lock:\n",
1108                 irqclass);
1109         print_lock_name(backwards_match);
1110         printk("\n... which became %s-irq-safe at:\n", irqclass);
1111
1112         print_stack_trace(backwards_match->usage_traces + bit1, 1);
1113
1114         printk("\nto a %s-irq-unsafe lock:\n", irqclass);
1115         print_lock_name(forwards_match);
1116         printk("\n... which became %s-irq-unsafe at:\n", irqclass);
1117         printk("...");
1118
1119         print_stack_trace(forwards_match->usage_traces + bit2, 1);
1120
1121         printk("\nother info that might help us debug this:\n\n");
1122         lockdep_print_held_locks(curr);
1123
1124         printk("\nthe %s-irq-safe lock's dependencies:\n", irqclass);
1125         print_lock_dependencies(backwards_match, 0);
1126
1127         printk("\nthe %s-irq-unsafe lock's dependencies:\n", irqclass);
1128         print_lock_dependencies(forwards_match, 0);
1129
1130         printk("\nstack backtrace:\n");
1131         dump_stack();
1132
1133         return 0;
1134 }
1135
1136 static int
1137 check_usage(struct task_struct *curr, struct held_lock *prev,
1138             struct held_lock *next, enum lock_usage_bit bit_backwards,
1139             enum lock_usage_bit bit_forwards, const char *irqclass)
1140 {
1141         int ret;
1142
1143         find_usage_bit = bit_backwards;
1144         /* fills in <backwards_match> */
1145         ret = find_usage_backwards(prev->class, 0);
1146         if (!ret || ret == 1)
1147                 return ret;
1148
1149         find_usage_bit = bit_forwards;
1150         ret = find_usage_forwards(next->class, 0);
1151         if (!ret || ret == 1)
1152                 return ret;
1153         /* ret == 2 */
1154         return print_bad_irq_dependency(curr, prev, next,
1155                         bit_backwards, bit_forwards, irqclass);
1156 }
1157
1158 static int
1159 check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
1160                 struct held_lock *next)
1161 {
1162         /*
1163          * Prove that the new dependency does not connect a hardirq-safe
1164          * lock with a hardirq-unsafe lock - to achieve this we search
1165          * the backwards-subgraph starting at <prev>, and the
1166          * forwards-subgraph starting at <next>:
1167          */
1168         if (!check_usage(curr, prev, next, LOCK_USED_IN_HARDIRQ,
1169                                         LOCK_ENABLED_HARDIRQS, "hard"))
1170                 return 0;
1171
1172         /*
1173          * Prove that the new dependency does not connect a hardirq-safe-read
1174          * lock with a hardirq-unsafe lock - to achieve this we search
1175          * the backwards-subgraph starting at <prev>, and the
1176          * forwards-subgraph starting at <next>:
1177          */
1178         if (!check_usage(curr, prev, next, LOCK_USED_IN_HARDIRQ_READ,
1179                                         LOCK_ENABLED_HARDIRQS, "hard-read"))
1180                 return 0;
1181
1182         /*
1183          * Prove that the new dependency does not connect a softirq-safe
1184          * lock with a softirq-unsafe lock - to achieve this we search
1185          * the backwards-subgraph starting at <prev>, and the
1186          * forwards-subgraph starting at <next>:
1187          */
1188         if (!check_usage(curr, prev, next, LOCK_USED_IN_SOFTIRQ,
1189                                         LOCK_ENABLED_SOFTIRQS, "soft"))
1190                 return 0;
1191         /*
1192          * Prove that the new dependency does not connect a softirq-safe-read
1193          * lock with a softirq-unsafe lock - to achieve this we search
1194          * the backwards-subgraph starting at <prev>, and the
1195          * forwards-subgraph starting at <next>:
1196          */
1197         if (!check_usage(curr, prev, next, LOCK_USED_IN_SOFTIRQ_READ,
1198                                         LOCK_ENABLED_SOFTIRQS, "soft"))
1199                 return 0;
1200
1201         return 1;
1202 }
1203
1204 static void inc_chains(void)
1205 {
1206         if (current->hardirq_context)
1207                 nr_hardirq_chains++;
1208         else {
1209                 if (current->softirq_context)
1210                         nr_softirq_chains++;
1211                 else
1212                         nr_process_chains++;
1213         }
1214 }
1215
1216 #else
1217
1218 static inline int
1219 check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
1220                 struct held_lock *next)
1221 {
1222         return 1;
1223 }
1224
1225 static inline void inc_chains(void)
1226 {
1227         nr_process_chains++;
1228 }
1229
1230 #endif
1231
1232 static int
1233 print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
1234                    struct held_lock *next)
1235 {
1236         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1237                 return 0;
1238
1239         printk("\n=============================================\n");
1240         printk(  "[ INFO: possible recursive locking detected ]\n");
1241         print_kernel_version();
1242         printk(  "---------------------------------------------\n");
1243         printk("%s/%d is trying to acquire lock:\n",
1244                 curr->comm, task_pid_nr(curr));
1245         print_lock(next);
1246         printk("\nbut task is already holding lock:\n");
1247         print_lock(prev);
1248
1249         printk("\nother info that might help us debug this:\n");
1250         lockdep_print_held_locks(curr);
1251
1252         printk("\nstack backtrace:\n");
1253         dump_stack();
1254
1255         return 0;
1256 }
1257
1258 /*
1259  * Check whether we are holding such a class already.
1260  *
1261  * (Note that this has to be done separately, because the graph cannot
1262  * detect such classes of deadlocks.)
1263  *
1264  * Returns: 0 on deadlock detected, 1 on OK, 2 on recursive read
1265  */
1266 static int
1267 check_deadlock(struct task_struct *curr, struct held_lock *next,
1268                struct lockdep_map *next_instance, int read)
1269 {
1270         struct held_lock *prev;
1271         int i;
1272
1273         for (i = 0; i < curr->lockdep_depth; i++) {
1274                 prev = curr->held_locks + i;
1275                 if (prev->class != next->class)
1276                         continue;
1277                 /*
1278                  * Allow read-after-read recursion of the same
1279                  * lock class (i.e. read_lock(lock)+read_lock(lock)):
1280                  */
1281                 if ((read == 2) && prev->read)
1282                         return 2;
1283                 return print_deadlock_bug(curr, prev, next);
1284         }
1285         return 1;
1286 }
1287
1288 /*
1289  * There was a chain-cache miss, and we are about to add a new dependency
1290  * to a previous lock. We recursively validate the following rules:
1291  *
1292  *  - would the adding of the <prev> -> <next> dependency create a
1293  *    circular dependency in the graph? [== circular deadlock]
1294  *
1295  *  - does the new prev->next dependency connect any hardirq-safe lock
1296  *    (in the full backwards-subgraph starting at <prev>) with any
1297  *    hardirq-unsafe lock (in the full forwards-subgraph starting at
1298  *    <next>)? [== illegal lock inversion with hardirq contexts]
1299  *
1300  *  - does the new prev->next dependency connect any softirq-safe lock
1301  *    (in the full backwards-subgraph starting at <prev>) with any
1302  *    softirq-unsafe lock (in the full forwards-subgraph starting at
1303  *    <next>)? [== illegal lock inversion with softirq contexts]
1304  *
1305  * any of these scenarios could lead to a deadlock.
1306  *
1307  * Then if all the validations pass, we add the forwards and backwards
1308  * dependency.
1309  */
1310 static int
1311 check_prev_add(struct task_struct *curr, struct held_lock *prev,
1312                struct held_lock *next, int distance)
1313 {
1314         struct lock_list *entry;
1315         int ret;
1316
1317         /*
1318          * Prove that the new <prev> -> <next> dependency would not
1319          * create a circular dependency in the graph. (We do this by
1320          * forward-recursing into the graph starting at <next>, and
1321          * checking whether we can reach <prev>.)
1322          *
1323          * We are using global variables to control the recursion, to
1324          * keep the stackframe size of the recursive functions low:
1325          */
1326         check_source = next;
1327         check_target = prev;
1328         if (!(check_noncircular(next->class, 0)))
1329                 return print_circular_bug_tail();
1330
1331         if (!check_prev_add_irq(curr, prev, next))
1332                 return 0;
1333
1334         /*
1335          * For recursive read-locks we do all the dependency checks,
1336          * but we dont store read-triggered dependencies (only
1337          * write-triggered dependencies). This ensures that only the
1338          * write-side dependencies matter, and that if for example a
1339          * write-lock never takes any other locks, then the reads are
1340          * equivalent to a NOP.
1341          */
1342         if (next->read == 2 || prev->read == 2)
1343                 return 1;
1344         /*
1345          * Is the <prev> -> <next> dependency already present?
1346          *
1347          * (this may occur even though this is a new chain: consider
1348          *  e.g. the L1 -> L2 -> L3 -> L4 and the L5 -> L1 -> L2 -> L3
1349          *  chains - the second one will be new, but L1 already has
1350          *  L2 added to its dependency list, due to the first chain.)
1351          */
1352         list_for_each_entry(entry, &prev->class->locks_after, entry) {
1353                 if (entry->class == next->class) {
1354                         if (distance == 1)
1355                                 entry->distance = 1;
1356                         return 2;
1357                 }
1358         }
1359
1360         /*
1361          * Ok, all validations passed, add the new lock
1362          * to the previous lock's dependency list:
1363          */
1364         ret = add_lock_to_list(prev->class, next->class,
1365                                &prev->class->locks_after, next->acquire_ip, distance);
1366
1367         if (!ret)
1368                 return 0;
1369
1370         ret = add_lock_to_list(next->class, prev->class,
1371                                &next->class->locks_before, next->acquire_ip, distance);
1372         if (!ret)
1373                 return 0;
1374
1375         /*
1376          * Debugging printouts:
1377          */
1378         if (verbose(prev->class) || verbose(next->class)) {
1379                 graph_unlock();
1380                 printk("\n new dependency: ");
1381                 print_lock_name(prev->class);
1382                 printk(" => ");
1383                 print_lock_name(next->class);
1384                 printk("\n");
1385                 dump_stack();
1386                 return graph_lock();
1387         }
1388         return 1;
1389 }
1390
1391 /*
1392  * Add the dependency to all directly-previous locks that are 'relevant'.
1393  * The ones that are relevant are (in increasing distance from curr):
1394  * all consecutive trylock entries and the final non-trylock entry - or
1395  * the end of this context's lock-chain - whichever comes first.
1396  */
1397 static int
1398 check_prevs_add(struct task_struct *curr, struct held_lock *next)
1399 {
1400         int depth = curr->lockdep_depth;
1401         struct held_lock *hlock;
1402
1403         /*
1404          * Debugging checks.
1405          *
1406          * Depth must not be zero for a non-head lock:
1407          */
1408         if (!depth)
1409                 goto out_bug;
1410         /*
1411          * At least two relevant locks must exist for this
1412          * to be a head:
1413          */
1414         if (curr->held_locks[depth].irq_context !=
1415                         curr->held_locks[depth-1].irq_context)
1416                 goto out_bug;
1417
1418         for (;;) {
1419                 int distance = curr->lockdep_depth - depth + 1;
1420                 hlock = curr->held_locks + depth-1;
1421                 /*
1422                  * Only non-recursive-read entries get new dependencies
1423                  * added:
1424                  */
1425                 if (hlock->read != 2) {
1426                         if (!check_prev_add(curr, hlock, next, distance))
1427                                 return 0;
1428                         /*
1429                          * Stop after the first non-trylock entry,
1430                          * as non-trylock entries have added their
1431                          * own direct dependencies already, so this
1432                          * lock is connected to them indirectly:
1433                          */
1434                         if (!hlock->trylock)
1435                                 break;
1436                 }
1437                 depth--;
1438                 /*
1439                  * End of lock-stack?
1440                  */
1441                 if (!depth)
1442                         break;
1443                 /*
1444                  * Stop the search if we cross into another context:
1445                  */
1446                 if (curr->held_locks[depth].irq_context !=
1447                                 curr->held_locks[depth-1].irq_context)
1448                         break;
1449         }
1450         return 1;
1451 out_bug:
1452         if (!debug_locks_off_graph_unlock())
1453                 return 0;
1454
1455         WARN_ON(1);
1456
1457         return 0;
1458 }
1459
1460 unsigned long nr_lock_chains;
1461 struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
1462 atomic_t nr_chain_hlocks;
1463 static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
1464
1465 struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
1466 {
1467         return lock_classes + chain_hlocks[chain->base + i];
1468 }
1469
1470 /*
1471  * Look up a dependency chain. If the key is not present yet then
1472  * add it and return 1 - in this case the new dependency chain is
1473  * validated. If the key is already hashed, return 0.
1474  * (On return with 1 graph_lock is held.)
1475  */
1476 static inline int lookup_chain_cache(struct task_struct *curr,
1477                                      struct held_lock *hlock,
1478                                      u64 chain_key)
1479 {
1480         struct lock_class *class = hlock->class;
1481         struct list_head *hash_head = chainhashentry(chain_key);
1482         struct lock_chain *chain;
1483         struct held_lock *hlock_curr, *hlock_next;
1484         int i, j, n;
1485
1486         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
1487                 return 0;
1488         /*
1489          * We can walk it lock-free, because entries only get added
1490          * to the hash:
1491          */
1492         list_for_each_entry(chain, hash_head, entry) {
1493                 if (chain->chain_key == chain_key) {
1494 cache_hit:
1495                         debug_atomic_inc(&chain_lookup_hits);
1496                         if (very_verbose(class))
1497                                 printk("\nhash chain already cached, key: "
1498                                         "%016Lx tail class: [%p] %s\n",
1499                                         (unsigned long long)chain_key,
1500                                         class->key, class->name);
1501                         return 0;
1502                 }
1503         }
1504         if (very_verbose(class))
1505                 printk("\nnew hash chain, key: %016Lx tail class: [%p] %s\n",
1506                         (unsigned long long)chain_key, class->key, class->name);
1507         /*
1508          * Allocate a new chain entry from the static array, and add
1509          * it to the hash:
1510          */
1511         if (!graph_lock())
1512                 return 0;
1513         /*
1514          * We have to walk the chain again locked - to avoid duplicates:
1515          */
1516         list_for_each_entry(chain, hash_head, entry) {
1517                 if (chain->chain_key == chain_key) {
1518                         graph_unlock();
1519                         goto cache_hit;
1520                 }
1521         }
1522         if (unlikely(nr_lock_chains >= MAX_LOCKDEP_CHAINS)) {
1523                 if (!debug_locks_off_graph_unlock())
1524                         return 0;
1525
1526                 printk("BUG: MAX_LOCKDEP_CHAINS too low!\n");
1527                 printk("turning off the locking correctness validator.\n");
1528                 return 0;
1529         }
1530         chain = lock_chains + nr_lock_chains++;
1531         chain->chain_key = chain_key;
1532         chain->irq_context = hlock->irq_context;
1533         /* Find the first held_lock of current chain */
1534         hlock_next = hlock;
1535         for (i = curr->lockdep_depth - 1; i >= 0; i--) {
1536                 hlock_curr = curr->held_locks + i;
1537                 if (hlock_curr->irq_context != hlock_next->irq_context)
1538                         break;
1539                 hlock_next = hlock;
1540         }
1541         i++;
1542         chain->depth = curr->lockdep_depth + 1 - i;
1543         n = atomic_add_return(chain->depth, &nr_chain_hlocks);
1544         if (unlikely(n < MAX_LOCKDEP_CHAIN_HLOCKS)) {
1545                 chain->base = n - chain->depth;
1546                 for (j = 0; j < chain->depth - 1; j++, i++) {
1547                         int lock_id = curr->held_locks[i].class - lock_classes;
1548                         chain_hlocks[chain->base + j] = lock_id;
1549                 }
1550                 chain_hlocks[chain->base + j] = class - lock_classes;
1551         }
1552         list_add_tail_rcu(&chain->entry, hash_head);
1553         debug_atomic_inc(&chain_lookup_misses);
1554         inc_chains();
1555
1556         return 1;
1557 }
1558
1559 static int validate_chain(struct task_struct *curr, struct lockdep_map *lock,
1560                 struct held_lock *hlock, int chain_head, u64 chain_key)
1561 {
1562         /*
1563          * Trylock needs to maintain the stack of held locks, but it
1564          * does not add new dependencies, because trylock can be done
1565          * in any order.
1566          *
1567          * We look up the chain_key and do the O(N^2) check and update of
1568          * the dependencies only if this is a new dependency chain.
1569          * (If lookup_chain_cache() returns with 1 it acquires
1570          * graph_lock for us)
1571          */
1572         if (!hlock->trylock && (hlock->check == 2) &&
1573             lookup_chain_cache(curr, hlock, chain_key)) {
1574                 /*
1575                  * Check whether last held lock:
1576                  *
1577                  * - is irq-safe, if this lock is irq-unsafe
1578                  * - is softirq-safe, if this lock is hardirq-unsafe
1579                  *
1580                  * And check whether the new lock's dependency graph
1581                  * could lead back to the previous lock.
1582                  *
1583                  * any of these scenarios could lead to a deadlock. If
1584                  * All validations
1585                  */
1586                 int ret = check_deadlock(curr, hlock, lock, hlock->read);
1587
1588                 if (!ret)
1589                         return 0;
1590                 /*
1591                  * Mark recursive read, as we jump over it when
1592                  * building dependencies (just like we jump over
1593                  * trylock entries):
1594                  */
1595                 if (ret == 2)
1596                         hlock->read = 2;
1597                 /*
1598                  * Add dependency only if this lock is not the head
1599                  * of the chain, and if it's not a secondary read-lock:
1600                  */
1601                 if (!chain_head && ret != 2)
1602                         if (!check_prevs_add(curr, hlock))
1603                                 return 0;
1604                 graph_unlock();
1605         } else
1606                 /* after lookup_chain_cache(): */
1607                 if (unlikely(!debug_locks))
1608                         return 0;
1609
1610         return 1;
1611 }
1612 #else
1613 static inline int validate_chain(struct task_struct *curr,
1614                 struct lockdep_map *lock, struct held_lock *hlock,
1615                 int chain_head, u64 chain_key)
1616 {
1617         return 1;
1618 }
1619 #endif
1620
1621 /*
1622  * We are building curr_chain_key incrementally, so double-check
1623  * it from scratch, to make sure that it's done correctly:
1624  */
1625 static void check_chain_key(struct task_struct *curr)
1626 {
1627 #ifdef CONFIG_DEBUG_LOCKDEP
1628         struct held_lock *hlock, *prev_hlock = NULL;
1629         unsigned int i, id;
1630         u64 chain_key = 0;
1631
1632         for (i = 0; i < curr->lockdep_depth; i++) {
1633                 hlock = curr->held_locks + i;
1634                 if (chain_key != hlock->prev_chain_key) {
1635                         debug_locks_off();
1636                         printk("hm#1, depth: %u [%u], %016Lx != %016Lx\n",
1637                                 curr->lockdep_depth, i,
1638                                 (unsigned long long)chain_key,
1639                                 (unsigned long long)hlock->prev_chain_key);
1640                         WARN_ON(1);
1641                         return;
1642                 }
1643                 id = hlock->class - lock_classes;
1644                 if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
1645                         return;
1646
1647                 if (prev_hlock && (prev_hlock->irq_context !=
1648                                                         hlock->irq_context))
1649                         chain_key = 0;
1650                 chain_key = iterate_chain_key(chain_key, id);
1651                 prev_hlock = hlock;
1652         }
1653         if (chain_key != curr->curr_chain_key) {
1654                 debug_locks_off();
1655                 printk("hm#2, depth: %u [%u], %016Lx != %016Lx\n",
1656                         curr->lockdep_depth, i,
1657                         (unsigned long long)chain_key,
1658                         (unsigned long long)curr->curr_chain_key);
1659                 WARN_ON(1);
1660         }
1661 #endif
1662 }
1663
1664 static int
1665 print_usage_bug(struct task_struct *curr, struct held_lock *this,
1666                 enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
1667 {
1668         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1669                 return 0;
1670
1671         printk("\n=================================\n");
1672         printk(  "[ INFO: inconsistent lock state ]\n");
1673         print_kernel_version();
1674         printk(  "---------------------------------\n");
1675
1676         printk("inconsistent {%s} -> {%s} usage.\n",
1677                 usage_str[prev_bit], usage_str[new_bit]);
1678
1679         printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] takes:\n",
1680                 curr->comm, task_pid_nr(curr),
1681                 trace_hardirq_context(curr), hardirq_count() >> HARDIRQ_SHIFT,
1682                 trace_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT,
1683                 trace_hardirqs_enabled(curr),
1684                 trace_softirqs_enabled(curr));
1685         print_lock(this);
1686
1687         printk("{%s} state was registered at:\n", usage_str[prev_bit]);
1688         print_stack_trace(this->class->usage_traces + prev_bit, 1);
1689
1690         print_irqtrace_events(curr);
1691         printk("\nother info that might help us debug this:\n");
1692         lockdep_print_held_locks(curr);
1693
1694         printk("\nstack backtrace:\n");
1695         dump_stack();
1696
1697         return 0;
1698 }
1699
1700 /*
1701  * Print out an error if an invalid bit is set:
1702  */
1703 static inline int
1704 valid_state(struct task_struct *curr, struct held_lock *this,
1705             enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit)
1706 {
1707         if (unlikely(this->class->usage_mask & (1 << bad_bit)))
1708                 return print_usage_bug(curr, this, bad_bit, new_bit);
1709         return 1;
1710 }
1711
1712 static int mark_lock(struct task_struct *curr, struct held_lock *this,
1713                      enum lock_usage_bit new_bit);
1714
1715 #ifdef CONFIG_TRACE_IRQFLAGS
1716
1717 /*
1718  * print irq inversion bug:
1719  */
1720 static int
1721 print_irq_inversion_bug(struct task_struct *curr, struct lock_class *other,
1722                         struct held_lock *this, int forwards,
1723                         const char *irqclass)
1724 {
1725         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1726                 return 0;
1727
1728         printk("\n=========================================================\n");
1729         printk(  "[ INFO: possible irq lock inversion dependency detected ]\n");
1730         print_kernel_version();
1731         printk(  "---------------------------------------------------------\n");
1732         printk("%s/%d just changed the state of lock:\n",
1733                 curr->comm, task_pid_nr(curr));
1734         print_lock(this);
1735         if (forwards)
1736                 printk("but this lock took another, %s-irq-unsafe lock in the past:\n", irqclass);
1737         else
1738                 printk("but this lock was taken by another, %s-irq-safe lock in the past:\n", irqclass);
1739         print_lock_name(other);
1740         printk("\n\nand interrupts could create inverse lock ordering between them.\n\n");
1741
1742         printk("\nother info that might help us debug this:\n");
1743         lockdep_print_held_locks(curr);
1744
1745         printk("\nthe first lock's dependencies:\n");
1746         print_lock_dependencies(this->class, 0);
1747
1748         printk("\nthe second lock's dependencies:\n");
1749         print_lock_dependencies(other, 0);
1750
1751         printk("\nstack backtrace:\n");
1752         dump_stack();
1753
1754         return 0;
1755 }
1756
1757 /*
1758  * Prove that in the forwards-direction subgraph starting at <this>
1759  * there is no lock matching <mask>:
1760  */
1761 static int
1762 check_usage_forwards(struct task_struct *curr, struct held_lock *this,
1763                      enum lock_usage_bit bit, const char *irqclass)
1764 {
1765         int ret;
1766
1767         find_usage_bit = bit;
1768         /* fills in <forwards_match> */
1769         ret = find_usage_forwards(this->class, 0);
1770         if (!ret || ret == 1)
1771                 return ret;
1772
1773         return print_irq_inversion_bug(curr, forwards_match, this, 1, irqclass);
1774 }
1775
1776 /*
1777  * Prove that in the backwards-direction subgraph starting at <this>
1778  * there is no lock matching <mask>:
1779  */
1780 static int
1781 check_usage_backwards(struct task_struct *curr, struct held_lock *this,
1782                       enum lock_usage_bit bit, const char *irqclass)
1783 {
1784         int ret;
1785
1786         find_usage_bit = bit;
1787         /* fills in <backwards_match> */
1788         ret = find_usage_backwards(this->class, 0);
1789         if (!ret || ret == 1)
1790                 return ret;
1791
1792         return print_irq_inversion_bug(curr, backwards_match, this, 0, irqclass);
1793 }
1794
1795 void print_irqtrace_events(struct task_struct *curr)
1796 {
1797         printk("irq event stamp: %u\n", curr->irq_events);
1798         printk("hardirqs last  enabled at (%u): ", curr->hardirq_enable_event);
1799         print_ip_sym(curr->hardirq_enable_ip);
1800         printk("hardirqs last disabled at (%u): ", curr->hardirq_disable_event);
1801         print_ip_sym(curr->hardirq_disable_ip);
1802         printk("softirqs last  enabled at (%u): ", curr->softirq_enable_event);
1803         print_ip_sym(curr->softirq_enable_ip);
1804         printk("softirqs last disabled at (%u): ", curr->softirq_disable_event);
1805         print_ip_sym(curr->softirq_disable_ip);
1806 }
1807
1808 static int hardirq_verbose(struct lock_class *class)
1809 {
1810 #if HARDIRQ_VERBOSE
1811         return class_filter(class);
1812 #endif
1813         return 0;
1814 }
1815
1816 static int softirq_verbose(struct lock_class *class)
1817 {
1818 #if SOFTIRQ_VERBOSE
1819         return class_filter(class);
1820 #endif
1821         return 0;
1822 }
1823
1824 #define STRICT_READ_CHECKS      1
1825
1826 static int mark_lock_irq(struct task_struct *curr, struct held_lock *this,
1827                 enum lock_usage_bit new_bit)
1828 {
1829         int ret = 1;
1830
1831         switch(new_bit) {
1832         case LOCK_USED_IN_HARDIRQ:
1833                 if (!valid_state(curr, this, new_bit, LOCK_ENABLED_HARDIRQS))
1834                         return 0;
1835                 if (!valid_state(curr, this, new_bit,
1836                                  LOCK_ENABLED_HARDIRQS_READ))
1837                         return 0;
1838                 /*
1839                  * just marked it hardirq-safe, check that this lock
1840                  * took no hardirq-unsafe lock in the past:
1841                  */
1842                 if (!check_usage_forwards(curr, this,
1843                                           LOCK_ENABLED_HARDIRQS, "hard"))
1844                         return 0;
1845 #if STRICT_READ_CHECKS
1846                 /*
1847                  * just marked it hardirq-safe, check that this lock
1848                  * took no hardirq-unsafe-read lock in the past:
1849                  */
1850                 if (!check_usage_forwards(curr, this,
1851                                 LOCK_ENABLED_HARDIRQS_READ, "hard-read"))
1852                         return 0;
1853 #endif
1854                 if (hardirq_verbose(this->class))
1855                         ret = 2;
1856                 break;
1857         case LOCK_USED_IN_SOFTIRQ:
1858                 if (!valid_state(curr, this, new_bit, LOCK_ENABLED_SOFTIRQS))
1859                         return 0;
1860                 if (!valid_state(curr, this, new_bit,
1861                                  LOCK_ENABLED_SOFTIRQS_READ))
1862                         return 0;
1863                 /*
1864                  * just marked it softirq-safe, check that this lock
1865                  * took no softirq-unsafe lock in the past:
1866                  */
1867                 if (!check_usage_forwards(curr, this,
1868                                           LOCK_ENABLED_SOFTIRQS, "soft"))
1869                         return 0;
1870 #if STRICT_READ_CHECKS
1871                 /*
1872                  * just marked it softirq-safe, check that this lock
1873                  * took no softirq-unsafe-read lock in the past:
1874                  */
1875                 if (!check_usage_forwards(curr, this,
1876                                 LOCK_ENABLED_SOFTIRQS_READ, "soft-read"))
1877                         return 0;
1878 #endif
1879                 if (softirq_verbose(this->class))
1880                         ret = 2;
1881                 break;
1882         case LOCK_USED_IN_HARDIRQ_READ:
1883                 if (!valid_state(curr, this, new_bit, LOCK_ENABLED_HARDIRQS))
1884                         return 0;
1885                 /*
1886                  * just marked it hardirq-read-safe, check that this lock
1887                  * took no hardirq-unsafe lock in the past:
1888                  */
1889                 if (!check_usage_forwards(curr, this,
1890                                           LOCK_ENABLED_HARDIRQS, "hard"))
1891                         return 0;
1892                 if (hardirq_verbose(this->class))
1893                         ret = 2;
1894                 break;
1895         case LOCK_USED_IN_SOFTIRQ_READ:
1896                 if (!valid_state(curr, this, new_bit, LOCK_ENABLED_SOFTIRQS))
1897                         return 0;
1898                 /*
1899                  * just marked it softirq-read-safe, check that this lock
1900                  * took no softirq-unsafe lock in the past:
1901                  */
1902                 if (!check_usage_forwards(curr, this,
1903                                           LOCK_ENABLED_SOFTIRQS, "soft"))
1904                         return 0;
1905                 if (softirq_verbose(this->class))
1906                         ret = 2;
1907                 break;
1908         case LOCK_ENABLED_HARDIRQS:
1909                 if (!valid_state(curr, this, new_bit, LOCK_USED_IN_HARDIRQ))
1910                         return 0;
1911                 if (!valid_state(curr, this, new_bit,
1912                                  LOCK_USED_IN_HARDIRQ_READ))
1913                         return 0;
1914                 /*
1915                  * just marked it hardirq-unsafe, check that no hardirq-safe
1916                  * lock in the system ever took it in the past:
1917                  */
1918                 if (!check_usage_backwards(curr, this,
1919                                            LOCK_USED_IN_HARDIRQ, "hard"))
1920                         return 0;
1921 #if STRICT_READ_CHECKS
1922                 /*
1923                  * just marked it hardirq-unsafe, check that no
1924                  * hardirq-safe-read lock in the system ever took
1925                  * it in the past:
1926                  */
1927                 if (!check_usage_backwards(curr, this,
1928                                    LOCK_USED_IN_HARDIRQ_READ, "hard-read"))
1929                         return 0;
1930 #endif
1931                 if (hardirq_verbose(this->class))
1932                         ret = 2;
1933                 break;
1934         case LOCK_ENABLED_SOFTIRQS:
1935                 if (!valid_state(curr, this, new_bit, LOCK_USED_IN_SOFTIRQ))
1936                         return 0;
1937                 if (!valid_state(curr, this, new_bit,
1938                                  LOCK_USED_IN_SOFTIRQ_READ))
1939                         return 0;
1940                 /*
1941                  * just marked it softirq-unsafe, check that no softirq-safe
1942                  * lock in the system ever took it in the past:
1943                  */
1944                 if (!check_usage_backwards(curr, this,
1945                                            LOCK_USED_IN_SOFTIRQ, "soft"))
1946                         return 0;
1947 #if STRICT_READ_CHECKS
1948                 /*
1949                  * just marked it softirq-unsafe, check that no
1950                  * softirq-safe-read lock in the system ever took
1951                  * it in the past:
1952                  */
1953                 if (!check_usage_backwards(curr, this,
1954                                    LOCK_USED_IN_SOFTIRQ_READ, "soft-read"))
1955                         return 0;
1956 #endif
1957                 if (softirq_verbose(this->class))
1958                         ret = 2;
1959                 break;
1960         case LOCK_ENABLED_HARDIRQS_READ:
1961                 if (!valid_state(curr, this, new_bit, LOCK_USED_IN_HARDIRQ))
1962                         return 0;
1963 #if STRICT_READ_CHECKS
1964                 /*
1965                  * just marked it hardirq-read-unsafe, check that no
1966                  * hardirq-safe lock in the system ever took it in the past:
1967                  */
1968                 if (!check_usage_backwards(curr, this,
1969                                            LOCK_USED_IN_HARDIRQ, "hard"))
1970                         return 0;
1971 #endif
1972                 if (hardirq_verbose(this->class))
1973                         ret = 2;
1974                 break;
1975         case LOCK_ENABLED_SOFTIRQS_READ:
1976                 if (!valid_state(curr, this, new_bit, LOCK_USED_IN_SOFTIRQ))
1977                         return 0;
1978 #if STRICT_READ_CHECKS
1979                 /*
1980                  * just marked it softirq-read-unsafe, check that no
1981                  * softirq-safe lock in the system ever took it in the past:
1982                  */
1983                 if (!check_usage_backwards(curr, this,
1984                                            LOCK_USED_IN_SOFTIRQ, "soft"))
1985                         return 0;
1986 #endif
1987                 if (softirq_verbose(this->class))
1988                         ret = 2;
1989                 break;
1990         default:
1991                 WARN_ON(1);
1992                 break;
1993         }
1994
1995         return ret;
1996 }
1997
1998 /*
1999  * Mark all held locks with a usage bit:
2000  */
2001 static int
2002 mark_held_locks(struct task_struct *curr, int hardirq)
2003 {
2004         enum lock_usage_bit usage_bit;
2005         struct held_lock *hlock;
2006         int i;
2007
2008         for (i = 0; i < curr->lockdep_depth; i++) {
2009                 hlock = curr->held_locks + i;
2010
2011                 if (hardirq) {
2012                         if (hlock->read)
2013                                 usage_bit = LOCK_ENABLED_HARDIRQS_READ;
2014                         else
2015                                 usage_bit = LOCK_ENABLED_HARDIRQS;
2016                 } else {
2017                         if (hlock->read)
2018                                 usage_bit = LOCK_ENABLED_SOFTIRQS_READ;
2019                         else
2020                                 usage_bit = LOCK_ENABLED_SOFTIRQS;
2021                 }
2022                 if (!mark_lock(curr, hlock, usage_bit))
2023                         return 0;
2024         }
2025
2026         return 1;
2027 }
2028
2029 /*
2030  * Debugging helper: via this flag we know that we are in
2031  * 'early bootup code', and will warn about any invalid irqs-on event:
2032  */
2033 static int early_boot_irqs_enabled;
2034
2035 void early_boot_irqs_off(void)
2036 {
2037         early_boot_irqs_enabled = 0;
2038 }
2039
2040 void early_boot_irqs_on(void)
2041 {
2042         early_boot_irqs_enabled = 1;
2043 }
2044
2045 /*
2046  * Hardirqs will be enabled:
2047  */
2048 void trace_hardirqs_on(void)
2049 {
2050         struct task_struct *curr = current;
2051         unsigned long ip;
2052
2053         if (unlikely(!debug_locks || current->lockdep_recursion))
2054                 return;
2055
2056         if (DEBUG_LOCKS_WARN_ON(unlikely(!early_boot_irqs_enabled)))
2057                 return;
2058
2059         if (unlikely(curr->hardirqs_enabled)) {
2060                 debug_atomic_inc(&redundant_hardirqs_on);
2061                 return;
2062         }
2063         /* we'll do an OFF -> ON transition: */
2064         curr->hardirqs_enabled = 1;
2065         ip = (unsigned long) __builtin_return_address(0);
2066
2067         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2068                 return;
2069         if (DEBUG_LOCKS_WARN_ON(current->hardirq_context))
2070                 return;
2071         /*
2072          * We are going to turn hardirqs on, so set the
2073          * usage bit for all held locks:
2074          */
2075         if (!mark_held_locks(curr, 1))
2076                 return;
2077         /*
2078          * If we have softirqs enabled, then set the usage
2079          * bit for all held locks. (disabled hardirqs prevented
2080          * this bit from being set before)
2081          */
2082         if (curr->softirqs_enabled)
2083                 if (!mark_held_locks(curr, 0))
2084                         return;
2085
2086         curr->hardirq_enable_ip = ip;
2087         curr->hardirq_enable_event = ++curr->irq_events;
2088         debug_atomic_inc(&hardirqs_on_events);
2089 }
2090
2091 EXPORT_SYMBOL(trace_hardirqs_on);
2092
2093 /*
2094  * Hardirqs were disabled:
2095  */
2096 void trace_hardirqs_off(void)
2097 {
2098         struct task_struct *curr = current;
2099
2100         if (unlikely(!debug_locks || current->lockdep_recursion))
2101                 return;
2102
2103         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2104                 return;
2105
2106         if (curr->hardirqs_enabled) {
2107                 /*
2108                  * We have done an ON -> OFF transition:
2109                  */
2110                 curr->hardirqs_enabled = 0;
2111                 curr->hardirq_disable_ip = _RET_IP_;
2112                 curr->hardirq_disable_event = ++curr->irq_events;
2113                 debug_atomic_inc(&hardirqs_off_events);
2114         } else
2115                 debug_atomic_inc(&redundant_hardirqs_off);
2116 }
2117
2118 EXPORT_SYMBOL(trace_hardirqs_off);
2119
2120 /*
2121  * Softirqs will be enabled:
2122  */
2123 void trace_softirqs_on(unsigned long ip)
2124 {
2125         struct task_struct *curr = current;
2126
2127         if (unlikely(!debug_locks))
2128                 return;
2129
2130         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2131                 return;
2132
2133         if (curr->softirqs_enabled) {
2134                 debug_atomic_inc(&redundant_softirqs_on);
2135                 return;
2136         }
2137
2138         /*
2139          * We'll do an OFF -> ON transition:
2140          */
2141         curr->softirqs_enabled = 1;
2142         curr->softirq_enable_ip = ip;
2143         curr->softirq_enable_event = ++curr->irq_events;
2144         debug_atomic_inc(&softirqs_on_events);
2145         /*
2146          * We are going to turn softirqs on, so set the
2147          * usage bit for all held locks, if hardirqs are
2148          * enabled too:
2149          */
2150         if (curr->hardirqs_enabled)
2151                 mark_held_locks(curr, 0);
2152 }
2153
2154 /*
2155  * Softirqs were disabled:
2156  */
2157 void trace_softirqs_off(unsigned long ip)
2158 {
2159         struct task_struct *curr = current;
2160
2161         if (unlikely(!debug_locks))
2162                 return;
2163
2164         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2165                 return;
2166
2167         if (curr->softirqs_enabled) {
2168                 /*
2169                  * We have done an ON -> OFF transition:
2170                  */
2171                 curr->softirqs_enabled = 0;
2172                 curr->softirq_disable_ip = ip;
2173                 curr->softirq_disable_event = ++curr->irq_events;
2174                 debug_atomic_inc(&softirqs_off_events);
2175                 DEBUG_LOCKS_WARN_ON(!softirq_count());
2176         } else
2177                 debug_atomic_inc(&redundant_softirqs_off);
2178 }
2179
2180 static int mark_irqflags(struct task_struct *curr, struct held_lock *hlock)
2181 {
2182         /*
2183          * If non-trylock use in a hardirq or softirq context, then
2184          * mark the lock as used in these contexts:
2185          */
2186         if (!hlock->trylock) {
2187                 if (hlock->read) {
2188                         if (curr->hardirq_context)
2189                                 if (!mark_lock(curr, hlock,
2190                                                 LOCK_USED_IN_HARDIRQ_READ))
2191                                         return 0;
2192                         if (curr->softirq_context)
2193                                 if (!mark_lock(curr, hlock,
2194                                                 LOCK_USED_IN_SOFTIRQ_READ))
2195                                         return 0;
2196                 } else {
2197                         if (curr->hardirq_context)
2198                                 if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ))
2199                                         return 0;
2200                         if (curr->softirq_context)
2201                                 if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ))
2202                                         return 0;
2203                 }
2204         }
2205         if (!hlock->hardirqs_off) {
2206                 if (hlock->read) {
2207                         if (!mark_lock(curr, hlock,
2208                                         LOCK_ENABLED_HARDIRQS_READ))
2209                                 return 0;
2210                         if (curr->softirqs_enabled)
2211                                 if (!mark_lock(curr, hlock,
2212                                                 LOCK_ENABLED_SOFTIRQS_READ))
2213                                         return 0;
2214                 } else {
2215                         if (!mark_lock(curr, hlock,
2216                                         LOCK_ENABLED_HARDIRQS))
2217                                 return 0;
2218                         if (curr->softirqs_enabled)
2219                                 if (!mark_lock(curr, hlock,
2220                                                 LOCK_ENABLED_SOFTIRQS))
2221                                         return 0;
2222                 }
2223         }
2224
2225         return 1;
2226 }
2227
2228 static int separate_irq_context(struct task_struct *curr,
2229                 struct held_lock *hlock)
2230 {
2231         unsigned int depth = curr->lockdep_depth;
2232
2233         /*
2234          * Keep track of points where we cross into an interrupt context:
2235          */
2236         hlock->irq_context = 2*(curr->hardirq_context ? 1 : 0) +
2237                                 curr->softirq_context;
2238         if (depth) {
2239                 struct held_lock *prev_hlock;
2240
2241                 prev_hlock = curr->held_locks + depth-1;
2242                 /*
2243                  * If we cross into another context, reset the
2244                  * hash key (this also prevents the checking and the
2245                  * adding of the dependency to 'prev'):
2246                  */
2247                 if (prev_hlock->irq_context != hlock->irq_context)
2248                         return 1;
2249         }
2250         return 0;
2251 }
2252
2253 #else
2254
2255 static inline
2256 int mark_lock_irq(struct task_struct *curr, struct held_lock *this,
2257                 enum lock_usage_bit new_bit)
2258 {
2259         WARN_ON(1);
2260         return 1;
2261 }
2262
2263 static inline int mark_irqflags(struct task_struct *curr,
2264                 struct held_lock *hlock)
2265 {
2266         return 1;
2267 }
2268
2269 static inline int separate_irq_context(struct task_struct *curr,
2270                 struct held_lock *hlock)
2271 {
2272         return 0;
2273 }
2274
2275 #endif
2276
2277 /*
2278  * Mark a lock with a usage bit, and validate the state transition:
2279  */
2280 static int mark_lock(struct task_struct *curr, struct held_lock *this,
2281                      enum lock_usage_bit new_bit)
2282 {
2283         unsigned int new_mask = 1 << new_bit, ret = 1;
2284
2285         /*
2286          * If already set then do not dirty the cacheline,
2287          * nor do any checks:
2288          */
2289         if (likely(this->class->usage_mask & new_mask))
2290                 return 1;
2291
2292         if (!graph_lock())
2293                 return 0;
2294         /*
2295          * Make sure we didnt race:
2296          */
2297         if (unlikely(this->class->usage_mask & new_mask)) {
2298                 graph_unlock();
2299                 return 1;
2300         }
2301
2302         this->class->usage_mask |= new_mask;
2303
2304         if (!save_trace(this->class->usage_traces + new_bit))
2305                 return 0;
2306
2307         switch (new_bit) {
2308         case LOCK_USED_IN_HARDIRQ:
2309         case LOCK_USED_IN_SOFTIRQ:
2310         case LOCK_USED_IN_HARDIRQ_READ:
2311         case LOCK_USED_IN_SOFTIRQ_READ:
2312         case LOCK_ENABLED_HARDIRQS:
2313         case LOCK_ENABLED_SOFTIRQS:
2314         case LOCK_ENABLED_HARDIRQS_READ:
2315         case LOCK_ENABLED_SOFTIRQS_READ:
2316                 ret = mark_lock_irq(curr, this, new_bit);
2317                 if (!ret)
2318                         return 0;
2319                 break;
2320         case LOCK_USED:
2321                 debug_atomic_dec(&nr_unused_locks);
2322                 break;
2323         default:
2324                 if (!debug_locks_off_graph_unlock())
2325                         return 0;
2326                 WARN_ON(1);
2327                 return 0;
2328         }
2329
2330         graph_unlock();
2331
2332         /*
2333          * We must printk outside of the graph_lock:
2334          */
2335         if (ret == 2) {
2336                 printk("\nmarked lock as {%s}:\n", usage_str[new_bit]);
2337                 print_lock(this);
2338                 print_irqtrace_events(curr);
2339                 dump_stack();
2340         }
2341
2342         return ret;
2343 }
2344
2345 /*
2346  * Initialize a lock instance's lock-class mapping info:
2347  */
2348 void lockdep_init_map(struct lockdep_map *lock, const char *name,
2349                       struct lock_class_key *key, int subclass)
2350 {
2351         if (unlikely(!debug_locks))
2352                 return;
2353
2354         if (DEBUG_LOCKS_WARN_ON(!key))
2355                 return;
2356         if (DEBUG_LOCKS_WARN_ON(!name))
2357                 return;
2358         /*
2359          * Sanity check, the lock-class key must be persistent:
2360          */
2361         if (!static_obj(key)) {
2362                 printk("BUG: key %p not in .data!\n", key);
2363                 DEBUG_LOCKS_WARN_ON(1);
2364                 return;
2365         }
2366         lock->name = name;
2367         lock->key = key;
2368         lock->class_cache = NULL;
2369 #ifdef CONFIG_LOCK_STAT
2370         lock->cpu = raw_smp_processor_id();
2371 #endif
2372         if (subclass)
2373                 register_lock_class(lock, subclass, 1);
2374 }
2375
2376 EXPORT_SYMBOL_GPL(lockdep_init_map);
2377
2378 /*
2379  * This gets called for every mutex_lock*()/spin_lock*() operation.
2380  * We maintain the dependency maps and validate the locking attempt:
2381  */
2382 static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
2383                           int trylock, int read, int check, int hardirqs_off,
2384                           unsigned long ip)
2385 {
2386         struct task_struct *curr = current;
2387         struct lock_class *class = NULL;
2388         struct held_lock *hlock;
2389         unsigned int depth, id;
2390         int chain_head = 0;
2391         u64 chain_key;
2392
2393         if (!prove_locking)
2394                 check = 1;
2395
2396         if (unlikely(!debug_locks))
2397                 return 0;
2398
2399         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2400                 return 0;
2401
2402         if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
2403                 debug_locks_off();
2404                 printk("BUG: MAX_LOCKDEP_SUBCLASSES too low!\n");
2405                 printk("turning off the locking correctness validator.\n");
2406                 return 0;
2407         }
2408
2409         if (!subclass)
2410                 class = lock->class_cache;
2411         /*
2412          * Not cached yet or subclass?
2413          */
2414         if (unlikely(!class)) {
2415                 class = register_lock_class(lock, subclass, 0);
2416                 if (!class)
2417                         return 0;
2418         }
2419         debug_atomic_inc((atomic_t *)&class->ops);
2420         if (very_verbose(class)) {
2421                 printk("\nacquire class [%p] %s", class->key, class->name);
2422                 if (class->name_version > 1)
2423                         printk("#%d", class->name_version);
2424                 printk("\n");
2425                 dump_stack();
2426         }
2427
2428         /*
2429          * Add the lock to the list of currently held locks.
2430          * (we dont increase the depth just yet, up until the
2431          * dependency checks are done)
2432          */
2433         depth = curr->lockdep_depth;
2434         if (DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH))
2435                 return 0;
2436
2437         hlock = curr->held_locks + depth;
2438
2439         hlock->class = class;
2440         hlock->acquire_ip = ip;
2441         hlock->instance = lock;
2442         hlock->trylock = trylock;
2443         hlock->read = read;
2444         hlock->check = check;
2445         hlock->hardirqs_off = hardirqs_off;
2446 #ifdef CONFIG_LOCK_STAT
2447         hlock->waittime_stamp = 0;
2448         hlock->holdtime_stamp = sched_clock();
2449 #endif
2450
2451         if (check == 2 && !mark_irqflags(curr, hlock))
2452                 return 0;
2453
2454         /* mark it as used: */
2455         if (!mark_lock(curr, hlock, LOCK_USED))
2456                 return 0;
2457
2458         /*
2459          * Calculate the chain hash: it's the combined hash of all the
2460          * lock keys along the dependency chain. We save the hash value
2461          * at every step so that we can get the current hash easily
2462          * after unlock. The chain hash is then used to cache dependency
2463          * results.
2464          *
2465          * The 'key ID' is what is the most compact key value to drive
2466          * the hash, not class->key.
2467          */
2468         id = class - lock_classes;
2469         if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
2470                 return 0;
2471
2472         chain_key = curr->curr_chain_key;
2473         if (!depth) {
2474                 if (DEBUG_LOCKS_WARN_ON(chain_key != 0))
2475                         return 0;
2476                 chain_head = 1;
2477         }
2478
2479         hlock->prev_chain_key = chain_key;
2480         if (separate_irq_context(curr, hlock)) {
2481                 chain_key = 0;
2482                 chain_head = 1;
2483         }
2484         chain_key = iterate_chain_key(chain_key, id);
2485
2486         if (!validate_chain(curr, lock, hlock, chain_head, chain_key))
2487                 return 0;
2488
2489         curr->curr_chain_key = chain_key;
2490         curr->lockdep_depth++;
2491         check_chain_key(curr);
2492 #ifdef CONFIG_DEBUG_LOCKDEP
2493         if (unlikely(!debug_locks))
2494                 return 0;
2495 #endif
2496         if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
2497                 debug_locks_off();
2498                 printk("BUG: MAX_LOCK_DEPTH too low!\n");
2499                 printk("turning off the locking correctness validator.\n");
2500                 return 0;
2501         }
2502
2503         if (unlikely(curr->lockdep_depth > max_lockdep_depth))
2504                 max_lockdep_depth = curr->lockdep_depth;
2505
2506         return 1;
2507 }
2508
2509 static int
2510 print_unlock_inbalance_bug(struct task_struct *curr, struct lockdep_map *lock,
2511                            unsigned long ip)
2512 {
2513         if (!debug_locks_off())
2514                 return 0;
2515         if (debug_locks_silent)
2516                 return 0;
2517
2518         printk("\n=====================================\n");
2519         printk(  "[ BUG: bad unlock balance detected! ]\n");
2520         printk(  "-------------------------------------\n");
2521         printk("%s/%d is trying to release lock (",
2522                 curr->comm, task_pid_nr(curr));
2523         print_lockdep_cache(lock);
2524         printk(") at:\n");
2525         print_ip_sym(ip);
2526         printk("but there are no more locks to release!\n");
2527         printk("\nother info that might help us debug this:\n");
2528         lockdep_print_held_locks(curr);
2529
2530         printk("\nstack backtrace:\n");
2531         dump_stack();
2532
2533         return 0;
2534 }
2535
2536 /*
2537  * Common debugging checks for both nested and non-nested unlock:
2538  */
2539 static int check_unlock(struct task_struct *curr, struct lockdep_map *lock,
2540                         unsigned long ip)
2541 {
2542         if (unlikely(!debug_locks))
2543                 return 0;
2544         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2545                 return 0;
2546
2547         if (curr->lockdep_depth <= 0)
2548                 return print_unlock_inbalance_bug(curr, lock, ip);
2549
2550         return 1;
2551 }
2552
2553 /*
2554  * Remove the lock to the list of currently held locks in a
2555  * potentially non-nested (out of order) manner. This is a
2556  * relatively rare operation, as all the unlock APIs default
2557  * to nested mode (which uses lock_release()):
2558  */
2559 static int
2560 lock_release_non_nested(struct task_struct *curr,
2561                         struct lockdep_map *lock, unsigned long ip)
2562 {
2563         struct held_lock *hlock, *prev_hlock;
2564         unsigned int depth;
2565         int i;
2566
2567         /*
2568          * Check whether the lock exists in the current stack
2569          * of held locks:
2570          */
2571         depth = curr->lockdep_depth;
2572         if (DEBUG_LOCKS_WARN_ON(!depth))
2573                 return 0;
2574
2575         prev_hlock = NULL;
2576         for (i = depth-1; i >= 0; i--) {
2577                 hlock = curr->held_locks + i;
2578                 /*
2579                  * We must not cross into another context:
2580                  */
2581                 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
2582                         break;
2583                 if (hlock->instance == lock)
2584                         goto found_it;
2585                 prev_hlock = hlock;
2586         }
2587         return print_unlock_inbalance_bug(curr, lock, ip);
2588
2589 found_it:
2590         lock_release_holdtime(hlock);
2591
2592         /*
2593          * We have the right lock to unlock, 'hlock' points to it.
2594          * Now we remove it from the stack, and add back the other
2595          * entries (if any), recalculating the hash along the way:
2596          */
2597         curr->lockdep_depth = i;
2598         curr->curr_chain_key = hlock->prev_chain_key;
2599
2600         for (i++; i < depth; i++) {
2601                 hlock = curr->held_locks + i;
2602                 if (!__lock_acquire(hlock->instance,
2603                         hlock->class->subclass, hlock->trylock,
2604                                 hlock->read, hlock->check, hlock->hardirqs_off,
2605                                 hlock->acquire_ip))
2606                         return 0;
2607         }
2608
2609         if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - 1))
2610                 return 0;
2611         return 1;
2612 }
2613
2614 /*
2615  * Remove the lock to the list of currently held locks - this gets
2616  * called on mutex_unlock()/spin_unlock*() (or on a failed
2617  * mutex_lock_interruptible()). This is done for unlocks that nest
2618  * perfectly. (i.e. the current top of the lock-stack is unlocked)
2619  */
2620 static int lock_release_nested(struct task_struct *curr,
2621                                struct lockdep_map *lock, unsigned long ip)
2622 {
2623         struct held_lock *hlock;
2624         unsigned int depth;
2625
2626         /*
2627          * Pop off the top of the lock stack:
2628          */
2629         depth = curr->lockdep_depth - 1;
2630         hlock = curr->held_locks + depth;
2631
2632         /*
2633          * Is the unlock non-nested:
2634          */
2635         if (hlock->instance != lock)
2636                 return lock_release_non_nested(curr, lock, ip);
2637         curr->lockdep_depth--;
2638
2639         if (DEBUG_LOCKS_WARN_ON(!depth && (hlock->prev_chain_key != 0)))
2640                 return 0;
2641
2642         curr->curr_chain_key = hlock->prev_chain_key;
2643
2644         lock_release_holdtime(hlock);
2645
2646 #ifdef CONFIG_DEBUG_LOCKDEP
2647         hlock->prev_chain_key = 0;
2648         hlock->class = NULL;
2649         hlock->acquire_ip = 0;
2650         hlock->irq_context = 0;
2651 #endif
2652         return 1;
2653 }
2654
2655 /*
2656  * Remove the lock to the list of currently held locks - this gets
2657  * called on mutex_unlock()/spin_unlock*() (or on a failed
2658  * mutex_lock_interruptible()). This is done for unlocks that nest
2659  * perfectly. (i.e. the current top of the lock-stack is unlocked)
2660  */
2661 static void
2662 __lock_release(struct lockdep_map *lock, int nested, unsigned long ip)
2663 {
2664         struct task_struct *curr = current;
2665
2666         if (!check_unlock(curr, lock, ip))
2667                 return;
2668
2669         if (nested) {
2670                 if (!lock_release_nested(curr, lock, ip))
2671                         return;
2672         } else {
2673                 if (!lock_release_non_nested(curr, lock, ip))
2674                         return;
2675         }
2676
2677         check_chain_key(curr);
2678 }
2679
2680 /*
2681  * Check whether we follow the irq-flags state precisely:
2682  */
2683 static void check_flags(unsigned long flags)
2684 {
2685 #if defined(CONFIG_DEBUG_LOCKDEP) && defined(CONFIG_TRACE_IRQFLAGS)
2686         if (!debug_locks)
2687                 return;
2688
2689         if (irqs_disabled_flags(flags)) {
2690                 if (DEBUG_LOCKS_WARN_ON(current->hardirqs_enabled)) {
2691                         printk("possible reason: unannotated irqs-off.\n");
2692                 }
2693         } else {
2694                 if (DEBUG_LOCKS_WARN_ON(!current->hardirqs_enabled)) {
2695                         printk("possible reason: unannotated irqs-on.\n");
2696                 }
2697         }
2698
2699         /*
2700          * We dont accurately track softirq state in e.g.
2701          * hardirq contexts (such as on 4KSTACKS), so only
2702          * check if not in hardirq contexts:
2703          */
2704         if (!hardirq_count()) {
2705                 if (softirq_count())
2706                         DEBUG_LOCKS_WARN_ON(current->softirqs_enabled);
2707                 else
2708                         DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled);
2709         }
2710
2711         if (!debug_locks)
2712                 print_irqtrace_events(current);
2713 #endif
2714 }
2715
2716 /*
2717  * We are not always called with irqs disabled - do that here,
2718  * and also avoid lockdep recursion:
2719  */
2720 void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
2721                   int trylock, int read, int check, unsigned long ip)
2722 {
2723         unsigned long flags;
2724
2725         if (unlikely(!lock_stat && !prove_locking))
2726                 return;
2727
2728         if (unlikely(current->lockdep_recursion))
2729                 return;
2730
2731         raw_local_irq_save(flags);
2732         check_flags(flags);
2733
2734         current->lockdep_recursion = 1;
2735         __lock_acquire(lock, subclass, trylock, read, check,
2736                        irqs_disabled_flags(flags), ip);
2737         current->lockdep_recursion = 0;
2738         raw_local_irq_restore(flags);
2739 }
2740
2741 EXPORT_SYMBOL_GPL(lock_acquire);
2742
2743 void lock_release(struct lockdep_map *lock, int nested, unsigned long ip)
2744 {
2745         unsigned long flags;
2746
2747         if (unlikely(!lock_stat && !prove_locking))
2748                 return;
2749
2750         if (unlikely(current->lockdep_recursion))
2751                 return;
2752
2753         raw_local_irq_save(flags);
2754         check_flags(flags);
2755         current->lockdep_recursion = 1;
2756         __lock_release(lock, nested, ip);
2757         current->lockdep_recursion = 0;
2758         raw_local_irq_restore(flags);
2759 }
2760
2761 EXPORT_SYMBOL_GPL(lock_release);
2762
2763 #ifdef CONFIG_LOCK_STAT
2764 static int
2765 print_lock_contention_bug(struct task_struct *curr, struct lockdep_map *lock,
2766                            unsigned long ip)
2767 {
2768         if (!debug_locks_off())
2769                 return 0;
2770         if (debug_locks_silent)
2771                 return 0;
2772
2773         printk("\n=================================\n");
2774         printk(  "[ BUG: bad contention detected! ]\n");
2775         printk(  "---------------------------------\n");
2776         printk("%s/%d is trying to contend lock (",
2777                 curr->comm, task_pid_nr(curr));
2778         print_lockdep_cache(lock);
2779         printk(") at:\n");
2780         print_ip_sym(ip);
2781         printk("but there are no locks held!\n");
2782         printk("\nother info that might help us debug this:\n");
2783         lockdep_print_held_locks(curr);
2784
2785         printk("\nstack backtrace:\n");
2786         dump_stack();
2787
2788         return 0;
2789 }
2790
2791 static void
2792 __lock_contended(struct lockdep_map *lock, unsigned long ip)
2793 {
2794         struct task_struct *curr = current;
2795         struct held_lock *hlock, *prev_hlock;
2796         struct lock_class_stats *stats;
2797         unsigned int depth;
2798         int i, point;
2799
2800         depth = curr->lockdep_depth;
2801         if (DEBUG_LOCKS_WARN_ON(!depth))
2802                 return;
2803
2804         prev_hlock = NULL;
2805         for (i = depth-1; i >= 0; i--) {
2806                 hlock = curr->held_locks + i;
2807                 /*
2808                  * We must not cross into another context:
2809                  */
2810                 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
2811                         break;
2812                 if (hlock->instance == lock)
2813                         goto found_it;
2814                 prev_hlock = hlock;
2815         }
2816         print_lock_contention_bug(curr, lock, ip);
2817         return;
2818
2819 found_it:
2820         hlock->waittime_stamp = sched_clock();
2821
2822         point = lock_contention_point(hlock->class, ip);
2823
2824         stats = get_lock_stats(hlock->class);
2825         if (point < ARRAY_SIZE(stats->contention_point))
2826                 stats->contention_point[i]++;
2827         if (lock->cpu != smp_processor_id())
2828                 stats->bounces[bounce_contended + !!hlock->read]++;
2829         put_lock_stats(stats);
2830 }
2831
2832 static void
2833 __lock_acquired(struct lockdep_map *lock)
2834 {
2835         struct task_struct *curr = current;
2836         struct held_lock *hlock, *prev_hlock;
2837         struct lock_class_stats *stats;
2838         unsigned int depth;
2839         u64 now;
2840         s64 waittime = 0;
2841         int i, cpu;
2842
2843         depth = curr->lockdep_depth;
2844         if (DEBUG_LOCKS_WARN_ON(!depth))
2845                 return;
2846
2847         prev_hlock = NULL;
2848         for (i = depth-1; i >= 0; i--) {
2849                 hlock = curr->held_locks + i;
2850                 /*
2851                  * We must not cross into another context:
2852                  */
2853                 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
2854                         break;
2855                 if (hlock->instance == lock)
2856                         goto found_it;
2857                 prev_hlock = hlock;
2858         }
2859         print_lock_contention_bug(curr, lock, _RET_IP_);
2860         return;
2861
2862 found_it:
2863         cpu = smp_processor_id();
2864         if (hlock->waittime_stamp) {
2865                 now = sched_clock();
2866                 waittime = now - hlock->waittime_stamp;
2867                 hlock->holdtime_stamp = now;
2868         }
2869
2870         stats = get_lock_stats(hlock->class);
2871         if (waittime) {
2872                 if (hlock->read)
2873                         lock_time_inc(&stats->read_waittime, waittime);
2874                 else
2875                         lock_time_inc(&stats->write_waittime, waittime);
2876         }
2877         if (lock->cpu != cpu)
2878                 stats->bounces[bounce_acquired + !!hlock->read]++;
2879         put_lock_stats(stats);
2880
2881         lock->cpu = cpu;
2882 }
2883
2884 void lock_contended(struct lockdep_map *lock, unsigned long ip)
2885 {
2886         unsigned long flags;
2887
2888         if (unlikely(!lock_stat))
2889                 return;
2890
2891         if (unlikely(current->lockdep_recursion))
2892                 return;
2893
2894         raw_local_irq_save(flags);
2895         check_flags(flags);
2896         current->lockdep_recursion = 1;
2897         __lock_contended(lock, ip);
2898         current->lockdep_recursion = 0;
2899         raw_local_irq_restore(flags);
2900 }
2901 EXPORT_SYMBOL_GPL(lock_contended);
2902
2903 void lock_acquired(struct lockdep_map *lock)
2904 {
2905         unsigned long flags;
2906
2907         if (unlikely(!lock_stat))
2908                 return;
2909
2910         if (unlikely(current->lockdep_recursion))
2911                 return;
2912
2913         raw_local_irq_save(flags);
2914         check_flags(flags);
2915         current->lockdep_recursion = 1;
2916         __lock_acquired(lock);
2917         current->lockdep_recursion = 0;
2918         raw_local_irq_restore(flags);
2919 }
2920 EXPORT_SYMBOL_GPL(lock_acquired);
2921 #endif
2922
2923 /*
2924  * Used by the testsuite, sanitize the validator state
2925  * after a simulated failure:
2926  */
2927
2928 void lockdep_reset(void)
2929 {
2930         unsigned long flags;
2931         int i;
2932
2933         raw_local_irq_save(flags);
2934         current->curr_chain_key = 0;
2935         current->lockdep_depth = 0;
2936         current->lockdep_recursion = 0;
2937         memset(current->held_locks, 0, MAX_LOCK_DEPTH*sizeof(struct held_lock));
2938         nr_hardirq_chains = 0;
2939         nr_softirq_chains = 0;
2940         nr_process_chains = 0;
2941         debug_locks = 1;
2942         for (i = 0; i < CHAINHASH_SIZE; i++)
2943                 INIT_LIST_HEAD(chainhash_table + i);
2944         raw_local_irq_restore(flags);
2945 }
2946
2947 static void zap_class(struct lock_class *class)
2948 {
2949         int i;
2950
2951         /*
2952          * Remove all dependencies this lock is
2953          * involved in:
2954          */
2955         for (i = 0; i < nr_list_entries; i++) {
2956                 if (list_entries[i].class == class)
2957                         list_del_rcu(&list_entries[i].entry);
2958         }
2959         /*
2960          * Unhash the class and remove it from the all_lock_classes list:
2961          */
2962         list_del_rcu(&class->hash_entry);
2963         list_del_rcu(&class->lock_entry);
2964
2965 }
2966
2967 static inline int within(const void *addr, void *start, unsigned long size)
2968 {
2969         return addr >= start && addr < start + size;
2970 }
2971
2972 void lockdep_free_key_range(void *start, unsigned long size)
2973 {
2974         struct lock_class *class, *next;
2975         struct list_head *head;
2976         unsigned long flags;
2977         int i;
2978         int locked;
2979
2980         raw_local_irq_save(flags);
2981         locked = graph_lock();
2982
2983         /*
2984          * Unhash all classes that were created by this module:
2985          */
2986         for (i = 0; i < CLASSHASH_SIZE; i++) {
2987                 head = classhash_table + i;
2988                 if (list_empty(head))
2989                         continue;
2990                 list_for_each_entry_safe(class, next, head, hash_entry) {
2991                         if (within(class->key, start, size))
2992                                 zap_class(class);
2993                         else if (within(class->name, start, size))
2994                                 zap_class(class);
2995                 }
2996         }
2997
2998         if (locked)
2999                 graph_unlock();
3000         raw_local_irq_restore(flags);
3001 }
3002
3003 void lockdep_reset_lock(struct lockdep_map *lock)
3004 {
3005         struct lock_class *class, *next;
3006         struct list_head *head;
3007         unsigned long flags;
3008         int i, j;
3009         int locked;
3010
3011         raw_local_irq_save(flags);
3012
3013         /*
3014          * Remove all classes this lock might have:
3015          */
3016         for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) {
3017                 /*
3018                  * If the class exists we look it up and zap it:
3019                  */
3020                 class = look_up_lock_class(lock, j);
3021                 if (class)
3022                         zap_class(class);
3023         }
3024         /*
3025          * Debug check: in the end all mapped classes should
3026          * be gone.
3027          */
3028         locked = graph_lock();
3029         for (i = 0; i < CLASSHASH_SIZE; i++) {
3030                 head = classhash_table + i;
3031                 if (list_empty(head))
3032                         continue;
3033                 list_for_each_entry_safe(class, next, head, hash_entry) {
3034                         if (unlikely(class == lock->class_cache)) {
3035                                 if (debug_locks_off_graph_unlock())
3036                                         WARN_ON(1);
3037                                 goto out_restore;
3038                         }
3039                 }
3040         }
3041         if (locked)
3042                 graph_unlock();
3043
3044 out_restore:
3045         raw_local_irq_restore(flags);
3046 }
3047
3048 void lockdep_init(void)
3049 {
3050         int i;
3051
3052         /*
3053          * Some architectures have their own start_kernel()
3054          * code which calls lockdep_init(), while we also
3055          * call lockdep_init() from the start_kernel() itself,
3056          * and we want to initialize the hashes only once:
3057          */
3058         if (lockdep_initialized)
3059                 return;
3060
3061         for (i = 0; i < CLASSHASH_SIZE; i++)
3062                 INIT_LIST_HEAD(classhash_table + i);
3063
3064         for (i = 0; i < CHAINHASH_SIZE; i++)
3065                 INIT_LIST_HEAD(chainhash_table + i);
3066
3067         lockdep_initialized = 1;
3068 }
3069
3070 void __init lockdep_info(void)
3071 {
3072         printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");
3073
3074         printk("... MAX_LOCKDEP_SUBCLASSES:    %lu\n", MAX_LOCKDEP_SUBCLASSES);
3075         printk("... MAX_LOCK_DEPTH:          %lu\n", MAX_LOCK_DEPTH);
3076         printk("... MAX_LOCKDEP_KEYS:        %lu\n", MAX_LOCKDEP_KEYS);
3077         printk("... CLASSHASH_SIZE:           %lu\n", CLASSHASH_SIZE);
3078         printk("... MAX_LOCKDEP_ENTRIES:     %lu\n", MAX_LOCKDEP_ENTRIES);
3079         printk("... MAX_LOCKDEP_CHAINS:      %lu\n", MAX_LOCKDEP_CHAINS);
3080         printk("... CHAINHASH_SIZE:          %lu\n", CHAINHASH_SIZE);
3081
3082         printk(" memory used by lock dependency info: %lu kB\n",
3083                 (sizeof(struct lock_class) * MAX_LOCKDEP_KEYS +
3084                 sizeof(struct list_head) * CLASSHASH_SIZE +
3085                 sizeof(struct lock_list) * MAX_LOCKDEP_ENTRIES +
3086                 sizeof(struct lock_chain) * MAX_LOCKDEP_CHAINS +
3087                 sizeof(struct list_head) * CHAINHASH_SIZE) / 1024);
3088
3089         printk(" per task-struct memory footprint: %lu bytes\n",
3090                 sizeof(struct held_lock) * MAX_LOCK_DEPTH);
3091
3092 #ifdef CONFIG_DEBUG_LOCKDEP
3093         if (lockdep_init_error) {
3094                 printk("WARNING: lockdep init error! Arch code didn't call lockdep_init() early enough?\n");
3095                 printk("Call stack leading to lockdep invocation was:\n");
3096                 print_stack_trace(&lockdep_init_trace, 0);
3097         }
3098 #endif
3099 }
3100
3101 static void
3102 print_freed_lock_bug(struct task_struct *curr, const void *mem_from,
3103                      const void *mem_to, struct held_lock *hlock)
3104 {
3105         if (!debug_locks_off())
3106                 return;
3107         if (debug_locks_silent)
3108                 return;
3109
3110         printk("\n=========================\n");
3111         printk(  "[ BUG: held lock freed! ]\n");
3112         printk(  "-------------------------\n");
3113         printk("%s/%d is freeing memory %p-%p, with a lock still held there!\n",
3114                 curr->comm, task_pid_nr(curr), mem_from, mem_to-1);
3115         print_lock(hlock);
3116         lockdep_print_held_locks(curr);
3117
3118         printk("\nstack backtrace:\n");
3119         dump_stack();
3120 }
3121
3122 static inline int not_in_range(const void* mem_from, unsigned long mem_len,
3123                                 const void* lock_from, unsigned long lock_len)
3124 {
3125         return lock_from + lock_len <= mem_from ||
3126                 mem_from + mem_len <= lock_from;
3127 }
3128
3129 /*
3130  * Called when kernel memory is freed (or unmapped), or if a lock
3131  * is destroyed or reinitialized - this code checks whether there is
3132  * any held lock in the memory range of <from> to <to>:
3133  */
3134 void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len)
3135 {
3136         struct task_struct *curr = current;
3137         struct held_lock *hlock;
3138         unsigned long flags;
3139         int i;
3140
3141         if (unlikely(!debug_locks))
3142                 return;
3143
3144         local_irq_save(flags);
3145         for (i = 0; i < curr->lockdep_depth; i++) {
3146                 hlock = curr->held_locks + i;
3147
3148                 if (not_in_range(mem_from, mem_len, hlock->instance,
3149                                         sizeof(*hlock->instance)))
3150                         continue;
3151
3152                 print_freed_lock_bug(curr, mem_from, mem_from + mem_len, hlock);
3153                 break;
3154         }
3155         local_irq_restore(flags);
3156 }
3157 EXPORT_SYMBOL_GPL(debug_check_no_locks_freed);
3158
3159 static void print_held_locks_bug(struct task_struct *curr)
3160 {
3161         if (!debug_locks_off())
3162                 return;
3163         if (debug_locks_silent)
3164                 return;
3165
3166         printk("\n=====================================\n");
3167         printk(  "[ BUG: lock held at task exit time! ]\n");
3168         printk(  "-------------------------------------\n");
3169         printk("%s/%d is exiting with locks still held!\n",
3170                 curr->comm, task_pid_nr(curr));
3171         lockdep_print_held_locks(curr);
3172
3173         printk("\nstack backtrace:\n");
3174         dump_stack();
3175 }
3176
3177 void debug_check_no_locks_held(struct task_struct *task)
3178 {
3179         if (unlikely(task->lockdep_depth > 0))
3180                 print_held_locks_bug(task);
3181 }
3182
3183 void debug_show_all_locks(void)
3184 {
3185         struct task_struct *g, *p;
3186         int count = 10;
3187         int unlock = 1;
3188
3189         if (unlikely(!debug_locks)) {
3190                 printk("INFO: lockdep is turned off.\n");
3191                 return;
3192         }
3193         printk("\nShowing all locks held in the system:\n");
3194
3195         /*
3196          * Here we try to get the tasklist_lock as hard as possible,
3197          * if not successful after 2 seconds we ignore it (but keep
3198          * trying). This is to enable a debug printout even if a
3199          * tasklist_lock-holding task deadlocks or crashes.
3200          */
3201 retry:
3202         if (!read_trylock(&tasklist_lock)) {
3203                 if (count == 10)
3204                         printk("hm, tasklist_lock locked, retrying... ");
3205                 if (count) {
3206                         count--;
3207                         printk(" #%d", 10-count);
3208                         mdelay(200);
3209                         goto retry;
3210                 }
3211                 printk(" ignoring it.\n");
3212                 unlock = 0;
3213         }
3214         if (count != 10)
3215                 printk(" locked it.\n");
3216
3217         do_each_thread(g, p) {
3218                 /*
3219                  * It's not reliable to print a task's held locks
3220                  * if it's not sleeping (or if it's not the current
3221                  * task):
3222                  */
3223                 if (p->state == TASK_RUNNING && p != current)
3224                         continue;
3225                 if (p->lockdep_depth)
3226                         lockdep_print_held_locks(p);
3227                 if (!unlock)
3228                         if (read_trylock(&tasklist_lock))
3229                                 unlock = 1;
3230         } while_each_thread(g, p);
3231
3232         printk("\n");
3233         printk("=============================================\n\n");
3234
3235         if (unlock)
3236                 read_unlock(&tasklist_lock);
3237 }
3238
3239 EXPORT_SYMBOL_GPL(debug_show_all_locks);
3240
3241 /*
3242  * Careful: only use this function if you are sure that
3243  * the task cannot run in parallel!
3244  */
3245 void __debug_show_held_locks(struct task_struct *task)
3246 {
3247         if (unlikely(!debug_locks)) {
3248                 printk("INFO: lockdep is turned off.\n");
3249                 return;
3250         }
3251         lockdep_print_held_locks(task);
3252 }
3253 EXPORT_SYMBOL_GPL(__debug_show_held_locks);
3254
3255 void debug_show_held_locks(struct task_struct *task)
3256 {
3257                 __debug_show_held_locks(task);
3258 }
3259
3260 EXPORT_SYMBOL_GPL(debug_show_held_locks);
3261
3262 void lockdep_sys_exit(void)
3263 {
3264         struct task_struct *curr = current;
3265
3266         if (unlikely(curr->lockdep_depth)) {
3267                 if (!debug_locks_off())
3268                         return;
3269                 printk("\n================================================\n");
3270                 printk(  "[ BUG: lock held when returning to user space! ]\n");
3271                 printk(  "------------------------------------------------\n");
3272                 printk("%s/%d is leaving the kernel with locks still held!\n",
3273                                 curr->comm, curr->pid);
3274                 lockdep_print_held_locks(curr);
3275         }
3276 }