24f176c9fc9ff8f2930f3e92cf81c1f399e2167b
[linux-3.10.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 #define DISABLE_BRANCH_PROFILING
29 #include <linux/mutex.h>
30 #include <linux/sched.h>
31 #include <linux/delay.h>
32 #include <linux/module.h>
33 #include <linux/proc_fs.h>
34 #include <linux/seq_file.h>
35 #include <linux/spinlock.h>
36 #include <linux/kallsyms.h>
37 #include <linux/interrupt.h>
38 #include <linux/stacktrace.h>
39 #include <linux/debug_locks.h>
40 #include <linux/irqflags.h>
41 #include <linux/utsname.h>
42 #include <linux/hash.h>
43 #include <linux/ftrace.h>
44 #include <linux/stringify.h>
45 #include <linux/bitops.h>
46 #include <linux/gfp.h>
47 #include <linux/kmemcheck.h>
48
49 #include <asm/sections.h>
50
51 #include "lockdep_internals.h"
52
53 #define CREATE_TRACE_POINTS
54 #include <trace/events/lock.h>
55
56 #ifdef CONFIG_PROVE_LOCKING
57 int prove_locking = 1;
58 module_param(prove_locking, int, 0644);
59 #else
60 #define prove_locking 0
61 #endif
62
63 #ifdef CONFIG_LOCK_STAT
64 int lock_stat = 1;
65 module_param(lock_stat, int, 0644);
66 #else
67 #define lock_stat 0
68 #endif
69
70 /*
71  * lockdep_lock: protects the lockdep graph, the hashes and the
72  *               class/list/hash allocators.
73  *
74  * This is one of the rare exceptions where it's justified
75  * to use a raw spinlock - we really dont want the spinlock
76  * code to recurse back into the lockdep code...
77  */
78 static arch_spinlock_t lockdep_lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
79
80 static int graph_lock(void)
81 {
82         arch_spin_lock(&lockdep_lock);
83         /*
84          * Make sure that if another CPU detected a bug while
85          * walking the graph we dont change it (while the other
86          * CPU is busy printing out stuff with the graph lock
87          * dropped already)
88          */
89         if (!debug_locks) {
90                 arch_spin_unlock(&lockdep_lock);
91                 return 0;
92         }
93         /* prevent any recursions within lockdep from causing deadlocks */
94         current->lockdep_recursion++;
95         return 1;
96 }
97
98 static inline int graph_unlock(void)
99 {
100         if (debug_locks && !arch_spin_is_locked(&lockdep_lock)) {
101                 /*
102                  * The lockdep graph lock isn't locked while we expect it to
103                  * be, we're confused now, bye!
104                  */
105                 return DEBUG_LOCKS_WARN_ON(1);
106         }
107
108         current->lockdep_recursion--;
109         arch_spin_unlock(&lockdep_lock);
110         return 0;
111 }
112
113 /*
114  * Turn lock debugging off and return with 0 if it was off already,
115  * and also release the graph lock:
116  */
117 static inline int debug_locks_off_graph_unlock(void)
118 {
119         int ret = debug_locks_off();
120
121         arch_spin_unlock(&lockdep_lock);
122
123         return ret;
124 }
125
126 static int lockdep_initialized;
127
128 unsigned long nr_list_entries;
129 static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES];
130
131 /*
132  * All data structures here are protected by the global debug_lock.
133  *
134  * Mutex key structs only get allocated, once during bootup, and never
135  * get freed - this significantly simplifies the debugging code.
136  */
137 unsigned long nr_lock_classes;
138 static struct lock_class lock_classes[MAX_LOCKDEP_KEYS];
139
140 static inline struct lock_class *hlock_class(struct held_lock *hlock)
141 {
142         if (!hlock->class_idx) {
143                 /*
144                  * Someone passed in garbage, we give up.
145                  */
146                 DEBUG_LOCKS_WARN_ON(1);
147                 return NULL;
148         }
149         return lock_classes + hlock->class_idx - 1;
150 }
151
152 #ifdef CONFIG_LOCK_STAT
153 static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS],
154                       cpu_lock_stats);
155
156 static inline u64 lockstat_clock(void)
157 {
158         return local_clock();
159 }
160
161 static int lock_point(unsigned long points[], unsigned long ip)
162 {
163         int i;
164
165         for (i = 0; i < LOCKSTAT_POINTS; i++) {
166                 if (points[i] == 0) {
167                         points[i] = ip;
168                         break;
169                 }
170                 if (points[i] == ip)
171                         break;
172         }
173
174         return i;
175 }
176
177 static void lock_time_inc(struct lock_time *lt, u64 time)
178 {
179         if (time > lt->max)
180                 lt->max = time;
181
182         if (time < lt->min || !lt->nr)
183                 lt->min = time;
184
185         lt->total += time;
186         lt->nr++;
187 }
188
189 static inline void lock_time_add(struct lock_time *src, struct lock_time *dst)
190 {
191         if (!src->nr)
192                 return;
193
194         if (src->max > dst->max)
195                 dst->max = src->max;
196
197         if (src->min < dst->min || !dst->nr)
198                 dst->min = src->min;
199
200         dst->total += src->total;
201         dst->nr += src->nr;
202 }
203
204 struct lock_class_stats lock_stats(struct lock_class *class)
205 {
206         struct lock_class_stats stats;
207         int cpu, i;
208
209         memset(&stats, 0, sizeof(struct lock_class_stats));
210         for_each_possible_cpu(cpu) {
211                 struct lock_class_stats *pcs =
212                         &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
213
214                 for (i = 0; i < ARRAY_SIZE(stats.contention_point); i++)
215                         stats.contention_point[i] += pcs->contention_point[i];
216
217                 for (i = 0; i < ARRAY_SIZE(stats.contending_point); i++)
218                         stats.contending_point[i] += pcs->contending_point[i];
219
220                 lock_time_add(&pcs->read_waittime, &stats.read_waittime);
221                 lock_time_add(&pcs->write_waittime, &stats.write_waittime);
222
223                 lock_time_add(&pcs->read_holdtime, &stats.read_holdtime);
224                 lock_time_add(&pcs->write_holdtime, &stats.write_holdtime);
225
226                 for (i = 0; i < ARRAY_SIZE(stats.bounces); i++)
227                         stats.bounces[i] += pcs->bounces[i];
228         }
229
230         return stats;
231 }
232
233 void clear_lock_stats(struct lock_class *class)
234 {
235         int cpu;
236
237         for_each_possible_cpu(cpu) {
238                 struct lock_class_stats *cpu_stats =
239                         &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
240
241                 memset(cpu_stats, 0, sizeof(struct lock_class_stats));
242         }
243         memset(class->contention_point, 0, sizeof(class->contention_point));
244         memset(class->contending_point, 0, sizeof(class->contending_point));
245 }
246
247 static struct lock_class_stats *get_lock_stats(struct lock_class *class)
248 {
249         return &get_cpu_var(cpu_lock_stats)[class - lock_classes];
250 }
251
252 static void put_lock_stats(struct lock_class_stats *stats)
253 {
254         put_cpu_var(cpu_lock_stats);
255 }
256
257 static void lock_release_holdtime(struct held_lock *hlock)
258 {
259         struct lock_class_stats *stats;
260         u64 holdtime;
261
262         if (!lock_stat)
263                 return;
264
265         holdtime = lockstat_clock() - hlock->holdtime_stamp;
266
267         stats = get_lock_stats(hlock_class(hlock));
268         if (hlock->read)
269                 lock_time_inc(&stats->read_holdtime, holdtime);
270         else
271                 lock_time_inc(&stats->write_holdtime, holdtime);
272         put_lock_stats(stats);
273 }
274 #else
275 static inline void lock_release_holdtime(struct held_lock *hlock)
276 {
277 }
278 #endif
279
280 /*
281  * We keep a global list of all lock classes. The list only grows,
282  * never shrinks. The list is only accessed with the lockdep
283  * spinlock lock held.
284  */
285 LIST_HEAD(all_lock_classes);
286
287 /*
288  * The lockdep classes are in a hash-table as well, for fast lookup:
289  */
290 #define CLASSHASH_BITS          (MAX_LOCKDEP_KEYS_BITS - 1)
291 #define CLASSHASH_SIZE          (1UL << CLASSHASH_BITS)
292 #define __classhashfn(key)      hash_long((unsigned long)key, CLASSHASH_BITS)
293 #define classhashentry(key)     (classhash_table + __classhashfn((key)))
294
295 static struct list_head classhash_table[CLASSHASH_SIZE];
296
297 /*
298  * We put the lock dependency chains into a hash-table as well, to cache
299  * their existence:
300  */
301 #define CHAINHASH_BITS          (MAX_LOCKDEP_CHAINS_BITS-1)
302 #define CHAINHASH_SIZE          (1UL << CHAINHASH_BITS)
303 #define __chainhashfn(chain)    hash_long(chain, CHAINHASH_BITS)
304 #define chainhashentry(chain)   (chainhash_table + __chainhashfn((chain)))
305
306 static struct list_head chainhash_table[CHAINHASH_SIZE];
307
308 /*
309  * The hash key of the lock dependency chains is a hash itself too:
310  * it's a hash of all locks taken up to that lock, including that lock.
311  * It's a 64-bit hash, because it's important for the keys to be
312  * unique.
313  */
314 #define iterate_chain_key(key1, key2) \
315         (((key1) << MAX_LOCKDEP_KEYS_BITS) ^ \
316         ((key1) >> (64-MAX_LOCKDEP_KEYS_BITS)) ^ \
317         (key2))
318
319 void lockdep_off(void)
320 {
321         current->lockdep_recursion++;
322 }
323 EXPORT_SYMBOL(lockdep_off);
324
325 void lockdep_on(void)
326 {
327         current->lockdep_recursion--;
328 }
329 EXPORT_SYMBOL(lockdep_on);
330
331 /*
332  * Debugging switches:
333  */
334
335 #define VERBOSE                 0
336 #define VERY_VERBOSE            0
337
338 #if VERBOSE
339 # define HARDIRQ_VERBOSE        1
340 # define SOFTIRQ_VERBOSE        1
341 # define RECLAIM_VERBOSE        1
342 #else
343 # define HARDIRQ_VERBOSE        0
344 # define SOFTIRQ_VERBOSE        0
345 # define RECLAIM_VERBOSE        0
346 #endif
347
348 #if VERBOSE || HARDIRQ_VERBOSE || SOFTIRQ_VERBOSE || RECLAIM_VERBOSE
349 /*
350  * Quick filtering for interesting events:
351  */
352 static int class_filter(struct lock_class *class)
353 {
354 #if 0
355         /* Example */
356         if (class->name_version == 1 &&
357                         !strcmp(class->name, "lockname"))
358                 return 1;
359         if (class->name_version == 1 &&
360                         !strcmp(class->name, "&struct->lockfield"))
361                 return 1;
362 #endif
363         /* Filter everything else. 1 would be to allow everything else */
364         return 0;
365 }
366 #endif
367
368 static int verbose(struct lock_class *class)
369 {
370 #if VERBOSE
371         return class_filter(class);
372 #endif
373         return 0;
374 }
375
376 /*
377  * Stack-trace: tightly packed array of stack backtrace
378  * addresses. Protected by the graph_lock.
379  */
380 unsigned long nr_stack_trace_entries;
381 static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];
382
383 static int save_trace(struct stack_trace *trace)
384 {
385         trace->nr_entries = 0;
386         trace->max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries;
387         trace->entries = stack_trace + nr_stack_trace_entries;
388
389         trace->skip = 3;
390
391         save_stack_trace(trace);
392
393         /*
394          * Some daft arches put -1 at the end to indicate its a full trace.
395          *
396          * <rant> this is buggy anyway, since it takes a whole extra entry so a
397          * complete trace that maxes out the entries provided will be reported
398          * as incomplete, friggin useless </rant>
399          */
400         if (trace->nr_entries != 0 &&
401             trace->entries[trace->nr_entries-1] == ULONG_MAX)
402                 trace->nr_entries--;
403
404         trace->max_entries = trace->nr_entries;
405
406         nr_stack_trace_entries += trace->nr_entries;
407
408         if (nr_stack_trace_entries >= MAX_STACK_TRACE_ENTRIES-1) {
409                 if (!debug_locks_off_graph_unlock())
410                         return 0;
411
412                 printk("BUG: MAX_STACK_TRACE_ENTRIES too low!\n");
413                 printk("turning off the locking correctness validator.\n");
414                 dump_stack();
415
416                 return 0;
417         }
418
419         return 1;
420 }
421
422 unsigned int nr_hardirq_chains;
423 unsigned int nr_softirq_chains;
424 unsigned int nr_process_chains;
425 unsigned int max_lockdep_depth;
426
427 #ifdef CONFIG_DEBUG_LOCKDEP
428 /*
429  * We cannot printk in early bootup code. Not even early_printk()
430  * might work. So we mark any initialization errors and printk
431  * about it later on, in lockdep_info().
432  */
433 static int lockdep_init_error;
434 static unsigned long lockdep_init_trace_data[20];
435 static struct stack_trace lockdep_init_trace = {
436         .max_entries = ARRAY_SIZE(lockdep_init_trace_data),
437         .entries = lockdep_init_trace_data,
438 };
439
440 /*
441  * Various lockdep statistics:
442  */
443 DEFINE_PER_CPU(struct lockdep_stats, lockdep_stats);
444 #endif
445
446 /*
447  * Locking printouts:
448  */
449
450 #define __USAGE(__STATE)                                                \
451         [LOCK_USED_IN_##__STATE] = "IN-"__stringify(__STATE)"-W",       \
452         [LOCK_ENABLED_##__STATE] = __stringify(__STATE)"-ON-W",         \
453         [LOCK_USED_IN_##__STATE##_READ] = "IN-"__stringify(__STATE)"-R",\
454         [LOCK_ENABLED_##__STATE##_READ] = __stringify(__STATE)"-ON-R",
455
456 static const char *usage_str[] =
457 {
458 #define LOCKDEP_STATE(__STATE) __USAGE(__STATE)
459 #include "lockdep_states.h"
460 #undef LOCKDEP_STATE
461         [LOCK_USED] = "INITIAL USE",
462 };
463
464 const char * __get_key_name(struct lockdep_subclass_key *key, char *str)
465 {
466         return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str);
467 }
468
469 static inline unsigned long lock_flag(enum lock_usage_bit bit)
470 {
471         return 1UL << bit;
472 }
473
474 static char get_usage_char(struct lock_class *class, enum lock_usage_bit bit)
475 {
476         char c = '.';
477
478         if (class->usage_mask & lock_flag(bit + 2))
479                 c = '+';
480         if (class->usage_mask & lock_flag(bit)) {
481                 c = '-';
482                 if (class->usage_mask & lock_flag(bit + 2))
483                         c = '?';
484         }
485
486         return c;
487 }
488
489 void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS])
490 {
491         int i = 0;
492
493 #define LOCKDEP_STATE(__STATE)                                          \
494         usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE);     \
495         usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE##_READ);
496 #include "lockdep_states.h"
497 #undef LOCKDEP_STATE
498
499         usage[i] = '\0';
500 }
501
502 static void __print_lock_name(struct lock_class *class)
503 {
504         char str[KSYM_NAME_LEN];
505         const char *name;
506
507         name = class->name;
508         if (!name) {
509                 name = __get_key_name(class->key, str);
510                 printk("%s", name);
511         } else {
512                 printk("%s", name);
513                 if (class->name_version > 1)
514                         printk("#%d", class->name_version);
515                 if (class->subclass)
516                         printk("/%d", class->subclass);
517         }
518 }
519
520 static void print_lock_name(struct lock_class *class)
521 {
522         char usage[LOCK_USAGE_CHARS];
523
524         get_usage_chars(class, usage);
525
526         printk(" (");
527         __print_lock_name(class);
528         printk("){%s}", usage);
529 }
530
531 static void print_lockdep_cache(struct lockdep_map *lock)
532 {
533         const char *name;
534         char str[KSYM_NAME_LEN];
535
536         name = lock->name;
537         if (!name)
538                 name = __get_key_name(lock->key->subkeys, str);
539
540         printk("%s", name);
541 }
542
543 static void print_lock(struct held_lock *hlock)
544 {
545         print_lock_name(hlock_class(hlock));
546         printk(", at: ");
547         print_ip_sym(hlock->acquire_ip);
548 }
549
550 static void lockdep_print_held_locks(struct task_struct *curr)
551 {
552         int i, depth = curr->lockdep_depth;
553
554         if (!depth) {
555                 printk("no locks held by %s/%d.\n", curr->comm, task_pid_nr(curr));
556                 return;
557         }
558         printk("%d lock%s held by %s/%d:\n",
559                 depth, depth > 1 ? "s" : "", curr->comm, task_pid_nr(curr));
560
561         for (i = 0; i < depth; i++) {
562                 printk(" #%d: ", i);
563                 print_lock(curr->held_locks + i);
564         }
565 }
566
567 static void print_kernel_version(void)
568 {
569         printk("%s %.*s\n", init_utsname()->release,
570                 (int)strcspn(init_utsname()->version, " "),
571                 init_utsname()->version);
572 }
573
574 static int very_verbose(struct lock_class *class)
575 {
576 #if VERY_VERBOSE
577         return class_filter(class);
578 #endif
579         return 0;
580 }
581
582 /*
583  * Is this the address of a static object:
584  */
585 static int static_obj(void *obj)
586 {
587         unsigned long start = (unsigned long) &_stext,
588                       end   = (unsigned long) &_end,
589                       addr  = (unsigned long) obj;
590
591         /*
592          * static variable?
593          */
594         if ((addr >= start) && (addr < end))
595                 return 1;
596
597         if (arch_is_kernel_data(addr))
598                 return 1;
599
600         /*
601          * in-kernel percpu var?
602          */
603         if (is_kernel_percpu_address(addr))
604                 return 1;
605
606         /*
607          * module static or percpu var?
608          */
609         return is_module_address(addr) || is_module_percpu_address(addr);
610 }
611
612 /*
613  * To make lock name printouts unique, we calculate a unique
614  * class->name_version generation counter:
615  */
616 static int count_matching_names(struct lock_class *new_class)
617 {
618         struct lock_class *class;
619         int count = 0;
620
621         if (!new_class->name)
622                 return 0;
623
624         list_for_each_entry(class, &all_lock_classes, lock_entry) {
625                 if (new_class->key - new_class->subclass == class->key)
626                         return class->name_version;
627                 if (class->name && !strcmp(class->name, new_class->name))
628                         count = max(count, class->name_version);
629         }
630
631         return count + 1;
632 }
633
634 /*
635  * Register a lock's class in the hash-table, if the class is not present
636  * yet. Otherwise we look it up. We cache the result in the lock object
637  * itself, so actual lookup of the hash should be once per lock object.
638  */
639 static inline struct lock_class *
640 look_up_lock_class(struct lockdep_map *lock, unsigned int subclass)
641 {
642         struct lockdep_subclass_key *key;
643         struct list_head *hash_head;
644         struct lock_class *class;
645
646 #ifdef CONFIG_DEBUG_LOCKDEP
647         /*
648          * If the architecture calls into lockdep before initializing
649          * the hashes then we'll warn about it later. (we cannot printk
650          * right now)
651          */
652         if (unlikely(!lockdep_initialized)) {
653                 lockdep_init();
654                 lockdep_init_error = 1;
655                 save_stack_trace(&lockdep_init_trace);
656         }
657 #endif
658
659         if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
660                 debug_locks_off();
661                 printk(KERN_ERR
662                         "BUG: looking up invalid subclass: %u\n", subclass);
663                 printk(KERN_ERR
664                         "turning off the locking correctness validator.\n");
665                 dump_stack();
666                 return NULL;
667         }
668
669         /*
670          * Static locks do not have their class-keys yet - for them the key
671          * is the lock object itself:
672          */
673         if (unlikely(!lock->key))
674                 lock->key = (void *)lock;
675
676         /*
677          * NOTE: the class-key must be unique. For dynamic locks, a static
678          * lock_class_key variable is passed in through the mutex_init()
679          * (or spin_lock_init()) call - which acts as the key. For static
680          * locks we use the lock object itself as the key.
681          */
682         BUILD_BUG_ON(sizeof(struct lock_class_key) >
683                         sizeof(struct lockdep_map));
684
685         key = lock->key->subkeys + subclass;
686
687         hash_head = classhashentry(key);
688
689         /*
690          * We can walk the hash lockfree, because the hash only
691          * grows, and we are careful when adding entries to the end:
692          */
693         list_for_each_entry(class, hash_head, hash_entry) {
694                 if (class->key == key) {
695                         /*
696                          * Huh! same key, different name? Did someone trample
697                          * on some memory? We're most confused.
698                          */
699                         WARN_ON_ONCE(class->name != lock->name);
700                         return class;
701                 }
702         }
703
704         return NULL;
705 }
706
707 /*
708  * Register a lock's class in the hash-table, if the class is not present
709  * yet. Otherwise we look it up. We cache the result in the lock object
710  * itself, so actual lookup of the hash should be once per lock object.
711  */
712 static inline struct lock_class *
713 register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
714 {
715         struct lockdep_subclass_key *key;
716         struct list_head *hash_head;
717         struct lock_class *class;
718         unsigned long flags;
719
720         class = look_up_lock_class(lock, subclass);
721         if (likely(class))
722                 return class;
723
724         /*
725          * Debug-check: all keys must be persistent!
726          */
727         if (!static_obj(lock->key)) {
728                 debug_locks_off();
729                 printk("INFO: trying to register non-static key.\n");
730                 printk("the code is fine but needs lockdep annotation.\n");
731                 printk("turning off the locking correctness validator.\n");
732                 dump_stack();
733
734                 return NULL;
735         }
736
737         key = lock->key->subkeys + subclass;
738         hash_head = classhashentry(key);
739
740         raw_local_irq_save(flags);
741         if (!graph_lock()) {
742                 raw_local_irq_restore(flags);
743                 return NULL;
744         }
745         /*
746          * We have to do the hash-walk again, to avoid races
747          * with another CPU:
748          */
749         list_for_each_entry(class, hash_head, hash_entry)
750                 if (class->key == key)
751                         goto out_unlock_set;
752         /*
753          * Allocate a new key from the static array, and add it to
754          * the hash:
755          */
756         if (nr_lock_classes >= MAX_LOCKDEP_KEYS) {
757                 if (!debug_locks_off_graph_unlock()) {
758                         raw_local_irq_restore(flags);
759                         return NULL;
760                 }
761                 raw_local_irq_restore(flags);
762
763                 printk("BUG: MAX_LOCKDEP_KEYS too low!\n");
764                 printk("turning off the locking correctness validator.\n");
765                 dump_stack();
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[0] = class;
809         else if (subclass < NR_LOCKDEP_CACHING_CLASSES)
810                 lock->class_cache[subclass] = class;
811
812         /*
813          * Hash collision, did we smoke some? We found a class with a matching
814          * hash but the subclass -- which is hashed in -- didn't match.
815          */
816         if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))
817                 return NULL;
818
819         return class;
820 }
821
822 #ifdef CONFIG_PROVE_LOCKING
823 /*
824  * Allocate a lockdep entry. (assumes the graph_lock held, returns
825  * with NULL on failure)
826  */
827 static struct lock_list *alloc_list_entry(void)
828 {
829         if (nr_list_entries >= MAX_LOCKDEP_ENTRIES) {
830                 if (!debug_locks_off_graph_unlock())
831                         return NULL;
832
833                 printk("BUG: MAX_LOCKDEP_ENTRIES too low!\n");
834                 printk("turning off the locking correctness validator.\n");
835                 dump_stack();
836                 return NULL;
837         }
838         return list_entries + nr_list_entries++;
839 }
840
841 /*
842  * Add a new dependency to the head of the list:
843  */
844 static int add_lock_to_list(struct lock_class *class, struct lock_class *this,
845                             struct list_head *head, unsigned long ip,
846                             int distance, struct stack_trace *trace)
847 {
848         struct lock_list *entry;
849         /*
850          * Lock not present yet - get a new dependency struct and
851          * add it to the list:
852          */
853         entry = alloc_list_entry();
854         if (!entry)
855                 return 0;
856
857         entry->class = this;
858         entry->distance = distance;
859         entry->trace = *trace;
860         /*
861          * Since we never remove from the dependency list, the list can
862          * be walked lockless by other CPUs, it's only allocation
863          * that must be protected by the spinlock. But this also means
864          * we must make new entries visible only once writes to the
865          * entry become visible - hence the RCU op:
866          */
867         list_add_tail_rcu(&entry->entry, head);
868
869         return 1;
870 }
871
872 /*
873  * For good efficiency of modular, we use power of 2
874  */
875 #define MAX_CIRCULAR_QUEUE_SIZE         4096UL
876 #define CQ_MASK                         (MAX_CIRCULAR_QUEUE_SIZE-1)
877
878 /*
879  * The circular_queue and helpers is used to implement the
880  * breadth-first search(BFS)algorithem, by which we can build
881  * the shortest path from the next lock to be acquired to the
882  * previous held lock if there is a circular between them.
883  */
884 struct circular_queue {
885         unsigned long element[MAX_CIRCULAR_QUEUE_SIZE];
886         unsigned int  front, rear;
887 };
888
889 static struct circular_queue lock_cq;
890
891 unsigned int max_bfs_queue_depth;
892
893 static unsigned int lockdep_dependency_gen_id;
894
895 static inline void __cq_init(struct circular_queue *cq)
896 {
897         cq->front = cq->rear = 0;
898         lockdep_dependency_gen_id++;
899 }
900
901 static inline int __cq_empty(struct circular_queue *cq)
902 {
903         return (cq->front == cq->rear);
904 }
905
906 static inline int __cq_full(struct circular_queue *cq)
907 {
908         return ((cq->rear + 1) & CQ_MASK) == cq->front;
909 }
910
911 static inline int __cq_enqueue(struct circular_queue *cq, unsigned long elem)
912 {
913         if (__cq_full(cq))
914                 return -1;
915
916         cq->element[cq->rear] = elem;
917         cq->rear = (cq->rear + 1) & CQ_MASK;
918         return 0;
919 }
920
921 static inline int __cq_dequeue(struct circular_queue *cq, unsigned long *elem)
922 {
923         if (__cq_empty(cq))
924                 return -1;
925
926         *elem = cq->element[cq->front];
927         cq->front = (cq->front + 1) & CQ_MASK;
928         return 0;
929 }
930
931 static inline unsigned int  __cq_get_elem_count(struct circular_queue *cq)
932 {
933         return (cq->rear - cq->front) & CQ_MASK;
934 }
935
936 static inline void mark_lock_accessed(struct lock_list *lock,
937                                         struct lock_list *parent)
938 {
939         unsigned long nr;
940
941         nr = lock - list_entries;
942         WARN_ON(nr >= nr_list_entries); /* Out-of-bounds, input fail */
943         lock->parent = parent;
944         lock->class->dep_gen_id = lockdep_dependency_gen_id;
945 }
946
947 static inline unsigned long lock_accessed(struct lock_list *lock)
948 {
949         unsigned long nr;
950
951         nr = lock - list_entries;
952         WARN_ON(nr >= nr_list_entries); /* Out-of-bounds, input fail */
953         return lock->class->dep_gen_id == lockdep_dependency_gen_id;
954 }
955
956 static inline struct lock_list *get_lock_parent(struct lock_list *child)
957 {
958         return child->parent;
959 }
960
961 static inline int get_lock_depth(struct lock_list *child)
962 {
963         int depth = 0;
964         struct lock_list *parent;
965
966         while ((parent = get_lock_parent(child))) {
967                 child = parent;
968                 depth++;
969         }
970         return depth;
971 }
972
973 static int __bfs(struct lock_list *source_entry,
974                  void *data,
975                  int (*match)(struct lock_list *entry, void *data),
976                  struct lock_list **target_entry,
977                  int forward)
978 {
979         struct lock_list *entry;
980         struct list_head *head;
981         struct circular_queue *cq = &lock_cq;
982         int ret = 1;
983
984         if (match(source_entry, data)) {
985                 *target_entry = source_entry;
986                 ret = 0;
987                 goto exit;
988         }
989
990         if (forward)
991                 head = &source_entry->class->locks_after;
992         else
993                 head = &source_entry->class->locks_before;
994
995         if (list_empty(head))
996                 goto exit;
997
998         __cq_init(cq);
999         __cq_enqueue(cq, (unsigned long)source_entry);
1000
1001         while (!__cq_empty(cq)) {
1002                 struct lock_list *lock;
1003
1004                 __cq_dequeue(cq, (unsigned long *)&lock);
1005
1006                 if (!lock->class) {
1007                         ret = -2;
1008                         goto exit;
1009                 }
1010
1011                 if (forward)
1012                         head = &lock->class->locks_after;
1013                 else
1014                         head = &lock->class->locks_before;
1015
1016                 list_for_each_entry(entry, head, entry) {
1017                         if (!lock_accessed(entry)) {
1018                                 unsigned int cq_depth;
1019                                 mark_lock_accessed(entry, lock);
1020                                 if (match(entry, data)) {
1021                                         *target_entry = entry;
1022                                         ret = 0;
1023                                         goto exit;
1024                                 }
1025
1026                                 if (__cq_enqueue(cq, (unsigned long)entry)) {
1027                                         ret = -1;
1028                                         goto exit;
1029                                 }
1030                                 cq_depth = __cq_get_elem_count(cq);
1031                                 if (max_bfs_queue_depth < cq_depth)
1032                                         max_bfs_queue_depth = cq_depth;
1033                         }
1034                 }
1035         }
1036 exit:
1037         return ret;
1038 }
1039
1040 static inline int __bfs_forwards(struct lock_list *src_entry,
1041                         void *data,
1042                         int (*match)(struct lock_list *entry, void *data),
1043                         struct lock_list **target_entry)
1044 {
1045         return __bfs(src_entry, data, match, target_entry, 1);
1046
1047 }
1048
1049 static inline int __bfs_backwards(struct lock_list *src_entry,
1050                         void *data,
1051                         int (*match)(struct lock_list *entry, void *data),
1052                         struct lock_list **target_entry)
1053 {
1054         return __bfs(src_entry, data, match, target_entry, 0);
1055
1056 }
1057
1058 /*
1059  * Recursive, forwards-direction lock-dependency checking, used for
1060  * both noncyclic checking and for hardirq-unsafe/softirq-unsafe
1061  * checking.
1062  */
1063
1064 /*
1065  * Print a dependency chain entry (this is only done when a deadlock
1066  * has been detected):
1067  */
1068 static noinline int
1069 print_circular_bug_entry(struct lock_list *target, int depth)
1070 {
1071         if (debug_locks_silent)
1072                 return 0;
1073         printk("\n-> #%u", depth);
1074         print_lock_name(target->class);
1075         printk(":\n");
1076         print_stack_trace(&target->trace, 6);
1077
1078         return 0;
1079 }
1080
1081 static void
1082 print_circular_lock_scenario(struct held_lock *src,
1083                              struct held_lock *tgt,
1084                              struct lock_list *prt)
1085 {
1086         struct lock_class *source = hlock_class(src);
1087         struct lock_class *target = hlock_class(tgt);
1088         struct lock_class *parent = prt->class;
1089
1090         /*
1091          * A direct locking problem where unsafe_class lock is taken
1092          * directly by safe_class lock, then all we need to show
1093          * is the deadlock scenario, as it is obvious that the
1094          * unsafe lock is taken under the safe lock.
1095          *
1096          * But if there is a chain instead, where the safe lock takes
1097          * an intermediate lock (middle_class) where this lock is
1098          * not the same as the safe lock, then the lock chain is
1099          * used to describe the problem. Otherwise we would need
1100          * to show a different CPU case for each link in the chain
1101          * from the safe_class lock to the unsafe_class lock.
1102          */
1103         if (parent != source) {
1104                 printk("Chain exists of:\n  ");
1105                 __print_lock_name(source);
1106                 printk(" --> ");
1107                 __print_lock_name(parent);
1108                 printk(" --> ");
1109                 __print_lock_name(target);
1110                 printk("\n\n");
1111         }
1112
1113         printk(" Possible unsafe locking scenario:\n\n");
1114         printk("       CPU0                    CPU1\n");
1115         printk("       ----                    ----\n");
1116         printk("  lock(");
1117         __print_lock_name(target);
1118         printk(");\n");
1119         printk("                               lock(");
1120         __print_lock_name(parent);
1121         printk(");\n");
1122         printk("                               lock(");
1123         __print_lock_name(target);
1124         printk(");\n");
1125         printk("  lock(");
1126         __print_lock_name(source);
1127         printk(");\n");
1128         printk("\n *** DEADLOCK ***\n\n");
1129 }
1130
1131 /*
1132  * When a circular dependency is detected, print the
1133  * header first:
1134  */
1135 static noinline int
1136 print_circular_bug_header(struct lock_list *entry, unsigned int depth,
1137                         struct held_lock *check_src,
1138                         struct held_lock *check_tgt)
1139 {
1140         struct task_struct *curr = current;
1141
1142         if (debug_locks_silent)
1143                 return 0;
1144
1145         printk("\n");
1146         printk("======================================================\n");
1147         printk("[ INFO: possible circular locking dependency detected ]\n");
1148         print_kernel_version();
1149         printk("-------------------------------------------------------\n");
1150         printk("%s/%d is trying to acquire lock:\n",
1151                 curr->comm, task_pid_nr(curr));
1152         print_lock(check_src);
1153         printk("\nbut task is already holding lock:\n");
1154         print_lock(check_tgt);
1155         printk("\nwhich lock already depends on the new lock.\n\n");
1156         printk("\nthe existing dependency chain (in reverse order) is:\n");
1157
1158         print_circular_bug_entry(entry, depth);
1159
1160         return 0;
1161 }
1162
1163 static inline int class_equal(struct lock_list *entry, void *data)
1164 {
1165         return entry->class == data;
1166 }
1167
1168 static noinline int print_circular_bug(struct lock_list *this,
1169                                 struct lock_list *target,
1170                                 struct held_lock *check_src,
1171                                 struct held_lock *check_tgt)
1172 {
1173         struct task_struct *curr = current;
1174         struct lock_list *parent;
1175         struct lock_list *first_parent;
1176         int depth;
1177
1178         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1179                 return 0;
1180
1181         if (!save_trace(&this->trace))
1182                 return 0;
1183
1184         depth = get_lock_depth(target);
1185
1186         print_circular_bug_header(target, depth, check_src, check_tgt);
1187
1188         parent = get_lock_parent(target);
1189         first_parent = parent;
1190
1191         while (parent) {
1192                 print_circular_bug_entry(parent, --depth);
1193                 parent = get_lock_parent(parent);
1194         }
1195
1196         printk("\nother info that might help us debug this:\n\n");
1197         print_circular_lock_scenario(check_src, check_tgt,
1198                                      first_parent);
1199
1200         lockdep_print_held_locks(curr);
1201
1202         printk("\nstack backtrace:\n");
1203         dump_stack();
1204
1205         return 0;
1206 }
1207
1208 static noinline int print_bfs_bug(int ret)
1209 {
1210         if (!debug_locks_off_graph_unlock())
1211                 return 0;
1212
1213         /*
1214          * Breadth-first-search failed, graph got corrupted?
1215          */
1216         WARN(1, "lockdep bfs error:%d\n", ret);
1217
1218         return 0;
1219 }
1220
1221 static int noop_count(struct lock_list *entry, void *data)
1222 {
1223         (*(unsigned long *)data)++;
1224         return 0;
1225 }
1226
1227 unsigned long __lockdep_count_forward_deps(struct lock_list *this)
1228 {
1229         unsigned long  count = 0;
1230         struct lock_list *uninitialized_var(target_entry);
1231
1232         __bfs_forwards(this, (void *)&count, noop_count, &target_entry);
1233
1234         return count;
1235 }
1236 unsigned long lockdep_count_forward_deps(struct lock_class *class)
1237 {
1238         unsigned long ret, flags;
1239         struct lock_list this;
1240
1241         this.parent = NULL;
1242         this.class = class;
1243
1244         local_irq_save(flags);
1245         arch_spin_lock(&lockdep_lock);
1246         ret = __lockdep_count_forward_deps(&this);
1247         arch_spin_unlock(&lockdep_lock);
1248         local_irq_restore(flags);
1249
1250         return ret;
1251 }
1252
1253 unsigned long __lockdep_count_backward_deps(struct lock_list *this)
1254 {
1255         unsigned long  count = 0;
1256         struct lock_list *uninitialized_var(target_entry);
1257
1258         __bfs_backwards(this, (void *)&count, noop_count, &target_entry);
1259
1260         return count;
1261 }
1262
1263 unsigned long lockdep_count_backward_deps(struct lock_class *class)
1264 {
1265         unsigned long ret, flags;
1266         struct lock_list this;
1267
1268         this.parent = NULL;
1269         this.class = class;
1270
1271         local_irq_save(flags);
1272         arch_spin_lock(&lockdep_lock);
1273         ret = __lockdep_count_backward_deps(&this);
1274         arch_spin_unlock(&lockdep_lock);
1275         local_irq_restore(flags);
1276
1277         return ret;
1278 }
1279
1280 /*
1281  * Prove that the dependency graph starting at <entry> can not
1282  * lead to <target>. Print an error and return 0 if it does.
1283  */
1284 static noinline int
1285 check_noncircular(struct lock_list *root, struct lock_class *target,
1286                 struct lock_list **target_entry)
1287 {
1288         int result;
1289
1290         debug_atomic_inc(nr_cyclic_checks);
1291
1292         result = __bfs_forwards(root, target, class_equal, target_entry);
1293
1294         return result;
1295 }
1296
1297 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
1298 /*
1299  * Forwards and backwards subgraph searching, for the purposes of
1300  * proving that two subgraphs can be connected by a new dependency
1301  * without creating any illegal irq-safe -> irq-unsafe lock dependency.
1302  */
1303
1304 static inline int usage_match(struct lock_list *entry, void *bit)
1305 {
1306         return entry->class->usage_mask & (1 << (enum lock_usage_bit)bit);
1307 }
1308
1309
1310
1311 /*
1312  * Find a node in the forwards-direction dependency sub-graph starting
1313  * at @root->class that matches @bit.
1314  *
1315  * Return 0 if such a node exists in the subgraph, and put that node
1316  * into *@target_entry.
1317  *
1318  * Return 1 otherwise and keep *@target_entry unchanged.
1319  * Return <0 on error.
1320  */
1321 static int
1322 find_usage_forwards(struct lock_list *root, enum lock_usage_bit bit,
1323                         struct lock_list **target_entry)
1324 {
1325         int result;
1326
1327         debug_atomic_inc(nr_find_usage_forwards_checks);
1328
1329         result = __bfs_forwards(root, (void *)bit, usage_match, target_entry);
1330
1331         return result;
1332 }
1333
1334 /*
1335  * Find a node in the backwards-direction dependency sub-graph starting
1336  * at @root->class that matches @bit.
1337  *
1338  * Return 0 if such a node exists in the subgraph, and put that node
1339  * into *@target_entry.
1340  *
1341  * Return 1 otherwise and keep *@target_entry unchanged.
1342  * Return <0 on error.
1343  */
1344 static int
1345 find_usage_backwards(struct lock_list *root, enum lock_usage_bit bit,
1346                         struct lock_list **target_entry)
1347 {
1348         int result;
1349
1350         debug_atomic_inc(nr_find_usage_backwards_checks);
1351
1352         result = __bfs_backwards(root, (void *)bit, usage_match, target_entry);
1353
1354         return result;
1355 }
1356
1357 static void print_lock_class_header(struct lock_class *class, int depth)
1358 {
1359         int bit;
1360
1361         printk("%*s->", depth, "");
1362         print_lock_name(class);
1363         printk(" ops: %lu", class->ops);
1364         printk(" {\n");
1365
1366         for (bit = 0; bit < LOCK_USAGE_STATES; bit++) {
1367                 if (class->usage_mask & (1 << bit)) {
1368                         int len = depth;
1369
1370                         len += printk("%*s   %s", depth, "", usage_str[bit]);
1371                         len += printk(" at:\n");
1372                         print_stack_trace(class->usage_traces + bit, len);
1373                 }
1374         }
1375         printk("%*s }\n", depth, "");
1376
1377         printk("%*s ... key      at: ",depth,"");
1378         print_ip_sym((unsigned long)class->key);
1379 }
1380
1381 /*
1382  * printk the shortest lock dependencies from @start to @end in reverse order:
1383  */
1384 static void __used
1385 print_shortest_lock_dependencies(struct lock_list *leaf,
1386                                 struct lock_list *root)
1387 {
1388         struct lock_list *entry = leaf;
1389         int depth;
1390
1391         /*compute depth from generated tree by BFS*/
1392         depth = get_lock_depth(leaf);
1393
1394         do {
1395                 print_lock_class_header(entry->class, depth);
1396                 printk("%*s ... acquired at:\n", depth, "");
1397                 print_stack_trace(&entry->trace, 2);
1398                 printk("\n");
1399
1400                 if (depth == 0 && (entry != root)) {
1401                         printk("lockdep:%s bad path found in chain graph\n", __func__);
1402                         break;
1403                 }
1404
1405                 entry = get_lock_parent(entry);
1406                 depth--;
1407         } while (entry && (depth >= 0));
1408
1409         return;
1410 }
1411
1412 static void
1413 print_irq_lock_scenario(struct lock_list *safe_entry,
1414                         struct lock_list *unsafe_entry,
1415                         struct lock_class *prev_class,
1416                         struct lock_class *next_class)
1417 {
1418         struct lock_class *safe_class = safe_entry->class;
1419         struct lock_class *unsafe_class = unsafe_entry->class;
1420         struct lock_class *middle_class = prev_class;
1421
1422         if (middle_class == safe_class)
1423                 middle_class = next_class;
1424
1425         /*
1426          * A direct locking problem where unsafe_class lock is taken
1427          * directly by safe_class lock, then all we need to show
1428          * is the deadlock scenario, as it is obvious that the
1429          * unsafe lock is taken under the safe lock.
1430          *
1431          * But if there is a chain instead, where the safe lock takes
1432          * an intermediate lock (middle_class) where this lock is
1433          * not the same as the safe lock, then the lock chain is
1434          * used to describe the problem. Otherwise we would need
1435          * to show a different CPU case for each link in the chain
1436          * from the safe_class lock to the unsafe_class lock.
1437          */
1438         if (middle_class != unsafe_class) {
1439                 printk("Chain exists of:\n  ");
1440                 __print_lock_name(safe_class);
1441                 printk(" --> ");
1442                 __print_lock_name(middle_class);
1443                 printk(" --> ");
1444                 __print_lock_name(unsafe_class);
1445                 printk("\n\n");
1446         }
1447
1448         printk(" Possible interrupt unsafe locking scenario:\n\n");
1449         printk("       CPU0                    CPU1\n");
1450         printk("       ----                    ----\n");
1451         printk("  lock(");
1452         __print_lock_name(unsafe_class);
1453         printk(");\n");
1454         printk("                               local_irq_disable();\n");
1455         printk("                               lock(");
1456         __print_lock_name(safe_class);
1457         printk(");\n");
1458         printk("                               lock(");
1459         __print_lock_name(middle_class);
1460         printk(");\n");
1461         printk("  <Interrupt>\n");
1462         printk("    lock(");
1463         __print_lock_name(safe_class);
1464         printk(");\n");
1465         printk("\n *** DEADLOCK ***\n\n");
1466 }
1467
1468 static int
1469 print_bad_irq_dependency(struct task_struct *curr,
1470                          struct lock_list *prev_root,
1471                          struct lock_list *next_root,
1472                          struct lock_list *backwards_entry,
1473                          struct lock_list *forwards_entry,
1474                          struct held_lock *prev,
1475                          struct held_lock *next,
1476                          enum lock_usage_bit bit1,
1477                          enum lock_usage_bit bit2,
1478                          const char *irqclass)
1479 {
1480         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1481                 return 0;
1482
1483         printk("\n");
1484         printk("======================================================\n");
1485         printk("[ INFO: %s-safe -> %s-unsafe lock order detected ]\n",
1486                 irqclass, irqclass);
1487         print_kernel_version();
1488         printk("------------------------------------------------------\n");
1489         printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
1490                 curr->comm, task_pid_nr(curr),
1491                 curr->hardirq_context, hardirq_count() >> HARDIRQ_SHIFT,
1492                 curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT,
1493                 curr->hardirqs_enabled,
1494                 curr->softirqs_enabled);
1495         print_lock(next);
1496
1497         printk("\nand this task is already holding:\n");
1498         print_lock(prev);
1499         printk("which would create a new lock dependency:\n");
1500         print_lock_name(hlock_class(prev));
1501         printk(" ->");
1502         print_lock_name(hlock_class(next));
1503         printk("\n");
1504
1505         printk("\nbut this new dependency connects a %s-irq-safe lock:\n",
1506                 irqclass);
1507         print_lock_name(backwards_entry->class);
1508         printk("\n... which became %s-irq-safe at:\n", irqclass);
1509
1510         print_stack_trace(backwards_entry->class->usage_traces + bit1, 1);
1511
1512         printk("\nto a %s-irq-unsafe lock:\n", irqclass);
1513         print_lock_name(forwards_entry->class);
1514         printk("\n... which became %s-irq-unsafe at:\n", irqclass);
1515         printk("...");
1516
1517         print_stack_trace(forwards_entry->class->usage_traces + bit2, 1);
1518
1519         printk("\nother info that might help us debug this:\n\n");
1520         print_irq_lock_scenario(backwards_entry, forwards_entry,
1521                                 hlock_class(prev), hlock_class(next));
1522
1523         lockdep_print_held_locks(curr);
1524
1525         printk("\nthe dependencies between %s-irq-safe lock", irqclass);
1526         printk(" and the holding lock:\n");
1527         if (!save_trace(&prev_root->trace))
1528                 return 0;
1529         print_shortest_lock_dependencies(backwards_entry, prev_root);
1530
1531         printk("\nthe dependencies between the lock to be acquired");
1532         printk(" and %s-irq-unsafe lock:\n", irqclass);
1533         if (!save_trace(&next_root->trace))
1534                 return 0;
1535         print_shortest_lock_dependencies(forwards_entry, next_root);
1536
1537         printk("\nstack backtrace:\n");
1538         dump_stack();
1539
1540         return 0;
1541 }
1542
1543 static int
1544 check_usage(struct task_struct *curr, struct held_lock *prev,
1545             struct held_lock *next, enum lock_usage_bit bit_backwards,
1546             enum lock_usage_bit bit_forwards, const char *irqclass)
1547 {
1548         int ret;
1549         struct lock_list this, that;
1550         struct lock_list *uninitialized_var(target_entry);
1551         struct lock_list *uninitialized_var(target_entry1);
1552
1553         this.parent = NULL;
1554
1555         this.class = hlock_class(prev);
1556         ret = find_usage_backwards(&this, bit_backwards, &target_entry);
1557         if (ret < 0)
1558                 return print_bfs_bug(ret);
1559         if (ret == 1)
1560                 return ret;
1561
1562         that.parent = NULL;
1563         that.class = hlock_class(next);
1564         ret = find_usage_forwards(&that, bit_forwards, &target_entry1);
1565         if (ret < 0)
1566                 return print_bfs_bug(ret);
1567         if (ret == 1)
1568                 return ret;
1569
1570         return print_bad_irq_dependency(curr, &this, &that,
1571                         target_entry, target_entry1,
1572                         prev, next,
1573                         bit_backwards, bit_forwards, irqclass);
1574 }
1575
1576 static const char *state_names[] = {
1577 #define LOCKDEP_STATE(__STATE) \
1578         __stringify(__STATE),
1579 #include "lockdep_states.h"
1580 #undef LOCKDEP_STATE
1581 };
1582
1583 static const char *state_rnames[] = {
1584 #define LOCKDEP_STATE(__STATE) \
1585         __stringify(__STATE)"-READ",
1586 #include "lockdep_states.h"
1587 #undef LOCKDEP_STATE
1588 };
1589
1590 static inline const char *state_name(enum lock_usage_bit bit)
1591 {
1592         return (bit & 1) ? state_rnames[bit >> 2] : state_names[bit >> 2];
1593 }
1594
1595 static int exclusive_bit(int new_bit)
1596 {
1597         /*
1598          * USED_IN
1599          * USED_IN_READ
1600          * ENABLED
1601          * ENABLED_READ
1602          *
1603          * bit 0 - write/read
1604          * bit 1 - used_in/enabled
1605          * bit 2+  state
1606          */
1607
1608         int state = new_bit & ~3;
1609         int dir = new_bit & 2;
1610
1611         /*
1612          * keep state, bit flip the direction and strip read.
1613          */
1614         return state | (dir ^ 2);
1615 }
1616
1617 static int check_irq_usage(struct task_struct *curr, struct held_lock *prev,
1618                            struct held_lock *next, enum lock_usage_bit bit)
1619 {
1620         /*
1621          * Prove that the new dependency does not connect a hardirq-safe
1622          * lock with a hardirq-unsafe lock - to achieve this we search
1623          * the backwards-subgraph starting at <prev>, and the
1624          * forwards-subgraph starting at <next>:
1625          */
1626         if (!check_usage(curr, prev, next, bit,
1627                            exclusive_bit(bit), state_name(bit)))
1628                 return 0;
1629
1630         bit++; /* _READ */
1631
1632         /*
1633          * Prove that the new dependency does not connect a hardirq-safe-read
1634          * lock with a hardirq-unsafe lock - to achieve this we search
1635          * the backwards-subgraph starting at <prev>, and the
1636          * forwards-subgraph starting at <next>:
1637          */
1638         if (!check_usage(curr, prev, next, bit,
1639                            exclusive_bit(bit), state_name(bit)))
1640                 return 0;
1641
1642         return 1;
1643 }
1644
1645 static int
1646 check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
1647                 struct held_lock *next)
1648 {
1649 #define LOCKDEP_STATE(__STATE)                                          \
1650         if (!check_irq_usage(curr, prev, next, LOCK_USED_IN_##__STATE)) \
1651                 return 0;
1652 #include "lockdep_states.h"
1653 #undef LOCKDEP_STATE
1654
1655         return 1;
1656 }
1657
1658 static void inc_chains(void)
1659 {
1660         if (current->hardirq_context)
1661                 nr_hardirq_chains++;
1662         else {
1663                 if (current->softirq_context)
1664                         nr_softirq_chains++;
1665                 else
1666                         nr_process_chains++;
1667         }
1668 }
1669
1670 #else
1671
1672 static inline int
1673 check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
1674                 struct held_lock *next)
1675 {
1676         return 1;
1677 }
1678
1679 static inline void inc_chains(void)
1680 {
1681         nr_process_chains++;
1682 }
1683
1684 #endif
1685
1686 static void
1687 print_deadlock_scenario(struct held_lock *nxt,
1688                              struct held_lock *prv)
1689 {
1690         struct lock_class *next = hlock_class(nxt);
1691         struct lock_class *prev = hlock_class(prv);
1692
1693         printk(" Possible unsafe locking scenario:\n\n");
1694         printk("       CPU0\n");
1695         printk("       ----\n");
1696         printk("  lock(");
1697         __print_lock_name(prev);
1698         printk(");\n");
1699         printk("  lock(");
1700         __print_lock_name(next);
1701         printk(");\n");
1702         printk("\n *** DEADLOCK ***\n\n");
1703         printk(" May be due to missing lock nesting notation\n\n");
1704 }
1705
1706 static int
1707 print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
1708                    struct held_lock *next)
1709 {
1710         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1711                 return 0;
1712
1713         printk("\n");
1714         printk("=============================================\n");
1715         printk("[ INFO: possible recursive locking detected ]\n");
1716         print_kernel_version();
1717         printk("---------------------------------------------\n");
1718         printk("%s/%d is trying to acquire lock:\n",
1719                 curr->comm, task_pid_nr(curr));
1720         print_lock(next);
1721         printk("\nbut task is already holding lock:\n");
1722         print_lock(prev);
1723
1724         printk("\nother info that might help us debug this:\n");
1725         print_deadlock_scenario(next, prev);
1726         lockdep_print_held_locks(curr);
1727
1728         printk("\nstack backtrace:\n");
1729         dump_stack();
1730
1731         return 0;
1732 }
1733
1734 /*
1735  * Check whether we are holding such a class already.
1736  *
1737  * (Note that this has to be done separately, because the graph cannot
1738  * detect such classes of deadlocks.)
1739  *
1740  * Returns: 0 on deadlock detected, 1 on OK, 2 on recursive read
1741  */
1742 static int
1743 check_deadlock(struct task_struct *curr, struct held_lock *next,
1744                struct lockdep_map *next_instance, int read)
1745 {
1746         struct held_lock *prev;
1747         struct held_lock *nest = NULL;
1748         int i;
1749
1750         for (i = 0; i < curr->lockdep_depth; i++) {
1751                 prev = curr->held_locks + i;
1752
1753                 if (prev->instance == next->nest_lock)
1754                         nest = prev;
1755
1756                 if (hlock_class(prev) != hlock_class(next))
1757                         continue;
1758
1759                 /*
1760                  * Allow read-after-read recursion of the same
1761                  * lock class (i.e. read_lock(lock)+read_lock(lock)):
1762                  */
1763                 if ((read == 2) && prev->read)
1764                         return 2;
1765
1766                 /*
1767                  * We're holding the nest_lock, which serializes this lock's
1768                  * nesting behaviour.
1769                  */
1770                 if (nest)
1771                         return 2;
1772
1773                 return print_deadlock_bug(curr, prev, next);
1774         }
1775         return 1;
1776 }
1777
1778 /*
1779  * There was a chain-cache miss, and we are about to add a new dependency
1780  * to a previous lock. We recursively validate the following rules:
1781  *
1782  *  - would the adding of the <prev> -> <next> dependency create a
1783  *    circular dependency in the graph? [== circular deadlock]
1784  *
1785  *  - does the new prev->next dependency connect any hardirq-safe lock
1786  *    (in the full backwards-subgraph starting at <prev>) with any
1787  *    hardirq-unsafe lock (in the full forwards-subgraph starting at
1788  *    <next>)? [== illegal lock inversion with hardirq contexts]
1789  *
1790  *  - does the new prev->next dependency connect any softirq-safe lock
1791  *    (in the full backwards-subgraph starting at <prev>) with any
1792  *    softirq-unsafe lock (in the full forwards-subgraph starting at
1793  *    <next>)? [== illegal lock inversion with softirq contexts]
1794  *
1795  * any of these scenarios could lead to a deadlock.
1796  *
1797  * Then if all the validations pass, we add the forwards and backwards
1798  * dependency.
1799  */
1800 static int
1801 check_prev_add(struct task_struct *curr, struct held_lock *prev,
1802                struct held_lock *next, int distance, int trylock_loop)
1803 {
1804         struct lock_list *entry;
1805         int ret;
1806         struct lock_list this;
1807         struct lock_list *uninitialized_var(target_entry);
1808         /*
1809          * Static variable, serialized by the graph_lock().
1810          *
1811          * We use this static variable to save the stack trace in case
1812          * we call into this function multiple times due to encountering
1813          * trylocks in the held lock stack.
1814          */
1815         static struct stack_trace trace;
1816
1817         /*
1818          * Prove that the new <prev> -> <next> dependency would not
1819          * create a circular dependency in the graph. (We do this by
1820          * forward-recursing into the graph starting at <next>, and
1821          * checking whether we can reach <prev>.)
1822          *
1823          * We are using global variables to control the recursion, to
1824          * keep the stackframe size of the recursive functions low:
1825          */
1826         this.class = hlock_class(next);
1827         this.parent = NULL;
1828         ret = check_noncircular(&this, hlock_class(prev), &target_entry);
1829         if (unlikely(!ret))
1830                 return print_circular_bug(&this, target_entry, next, prev);
1831         else if (unlikely(ret < 0))
1832                 return print_bfs_bug(ret);
1833
1834         if (!check_prev_add_irq(curr, prev, next))
1835                 return 0;
1836
1837         /*
1838          * For recursive read-locks we do all the dependency checks,
1839          * but we dont store read-triggered dependencies (only
1840          * write-triggered dependencies). This ensures that only the
1841          * write-side dependencies matter, and that if for example a
1842          * write-lock never takes any other locks, then the reads are
1843          * equivalent to a NOP.
1844          */
1845         if (next->read == 2 || prev->read == 2)
1846                 return 1;
1847         /*
1848          * Is the <prev> -> <next> dependency already present?
1849          *
1850          * (this may occur even though this is a new chain: consider
1851          *  e.g. the L1 -> L2 -> L3 -> L4 and the L5 -> L1 -> L2 -> L3
1852          *  chains - the second one will be new, but L1 already has
1853          *  L2 added to its dependency list, due to the first chain.)
1854          */
1855         list_for_each_entry(entry, &hlock_class(prev)->locks_after, entry) {
1856                 if (entry->class == hlock_class(next)) {
1857                         if (distance == 1)
1858                                 entry->distance = 1;
1859                         return 2;
1860                 }
1861         }
1862
1863         if (!trylock_loop && !save_trace(&trace))
1864                 return 0;
1865
1866         /*
1867          * Ok, all validations passed, add the new lock
1868          * to the previous lock's dependency list:
1869          */
1870         ret = add_lock_to_list(hlock_class(prev), hlock_class(next),
1871                                &hlock_class(prev)->locks_after,
1872                                next->acquire_ip, distance, &trace);
1873
1874         if (!ret)
1875                 return 0;
1876
1877         ret = add_lock_to_list(hlock_class(next), hlock_class(prev),
1878                                &hlock_class(next)->locks_before,
1879                                next->acquire_ip, distance, &trace);
1880         if (!ret)
1881                 return 0;
1882
1883         /*
1884          * Debugging printouts:
1885          */
1886         if (verbose(hlock_class(prev)) || verbose(hlock_class(next))) {
1887                 graph_unlock();
1888                 printk("\n new dependency: ");
1889                 print_lock_name(hlock_class(prev));
1890                 printk(" => ");
1891                 print_lock_name(hlock_class(next));
1892                 printk("\n");
1893                 dump_stack();
1894                 return graph_lock();
1895         }
1896         return 1;
1897 }
1898
1899 /*
1900  * Add the dependency to all directly-previous locks that are 'relevant'.
1901  * The ones that are relevant are (in increasing distance from curr):
1902  * all consecutive trylock entries and the final non-trylock entry - or
1903  * the end of this context's lock-chain - whichever comes first.
1904  */
1905 static int
1906 check_prevs_add(struct task_struct *curr, struct held_lock *next)
1907 {
1908         int depth = curr->lockdep_depth;
1909         int trylock_loop = 0;
1910         struct held_lock *hlock;
1911
1912         /*
1913          * Debugging checks.
1914          *
1915          * Depth must not be zero for a non-head lock:
1916          */
1917         if (!depth)
1918                 goto out_bug;
1919         /*
1920          * At least two relevant locks must exist for this
1921          * to be a head:
1922          */
1923         if (curr->held_locks[depth].irq_context !=
1924                         curr->held_locks[depth-1].irq_context)
1925                 goto out_bug;
1926
1927         for (;;) {
1928                 int distance = curr->lockdep_depth - depth + 1;
1929                 hlock = curr->held_locks + depth-1;
1930                 /*
1931                  * Only non-recursive-read entries get new dependencies
1932                  * added:
1933                  */
1934                 if (hlock->read != 2) {
1935                         if (!check_prev_add(curr, hlock, next,
1936                                                 distance, trylock_loop))
1937                                 return 0;
1938                         /*
1939                          * Stop after the first non-trylock entry,
1940                          * as non-trylock entries have added their
1941                          * own direct dependencies already, so this
1942                          * lock is connected to them indirectly:
1943                          */
1944                         if (!hlock->trylock)
1945                                 break;
1946                 }
1947                 depth--;
1948                 /*
1949                  * End of lock-stack?
1950                  */
1951                 if (!depth)
1952                         break;
1953                 /*
1954                  * Stop the search if we cross into another context:
1955                  */
1956                 if (curr->held_locks[depth].irq_context !=
1957                                 curr->held_locks[depth-1].irq_context)
1958                         break;
1959                 trylock_loop = 1;
1960         }
1961         return 1;
1962 out_bug:
1963         if (!debug_locks_off_graph_unlock())
1964                 return 0;
1965
1966         /*
1967          * Clearly we all shouldn't be here, but since we made it we
1968          * can reliable say we messed up our state. See the above two
1969          * gotos for reasons why we could possibly end up here.
1970          */
1971         WARN_ON(1);
1972
1973         return 0;
1974 }
1975
1976 unsigned long nr_lock_chains;
1977 struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
1978 int nr_chain_hlocks;
1979 static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
1980
1981 struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
1982 {
1983         return lock_classes + chain_hlocks[chain->base + i];
1984 }
1985
1986 /*
1987  * Look up a dependency chain. If the key is not present yet then
1988  * add it and return 1 - in this case the new dependency chain is
1989  * validated. If the key is already hashed, return 0.
1990  * (On return with 1 graph_lock is held.)
1991  */
1992 static inline int lookup_chain_cache(struct task_struct *curr,
1993                                      struct held_lock *hlock,
1994                                      u64 chain_key)
1995 {
1996         struct lock_class *class = hlock_class(hlock);
1997         struct list_head *hash_head = chainhashentry(chain_key);
1998         struct lock_chain *chain;
1999         struct held_lock *hlock_curr, *hlock_next;
2000         int i, j;
2001
2002         /*
2003          * We might need to take the graph lock, ensure we've got IRQs
2004          * disabled to make this an IRQ-safe lock.. for recursion reasons
2005          * lockdep won't complain about its own locking errors.
2006          */
2007         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2008                 return 0;
2009         /*
2010          * We can walk it lock-free, because entries only get added
2011          * to the hash:
2012          */
2013         list_for_each_entry(chain, hash_head, entry) {
2014                 if (chain->chain_key == chain_key) {
2015 cache_hit:
2016                         debug_atomic_inc(chain_lookup_hits);
2017                         if (very_verbose(class))
2018                                 printk("\nhash chain already cached, key: "
2019                                         "%016Lx tail class: [%p] %s\n",
2020                                         (unsigned long long)chain_key,
2021                                         class->key, class->name);
2022                         return 0;
2023                 }
2024         }
2025         if (very_verbose(class))
2026                 printk("\nnew hash chain, key: %016Lx tail class: [%p] %s\n",
2027                         (unsigned long long)chain_key, class->key, class->name);
2028         /*
2029          * Allocate a new chain entry from the static array, and add
2030          * it to the hash:
2031          */
2032         if (!graph_lock())
2033                 return 0;
2034         /*
2035          * We have to walk the chain again locked - to avoid duplicates:
2036          */
2037         list_for_each_entry(chain, hash_head, entry) {
2038                 if (chain->chain_key == chain_key) {
2039                         graph_unlock();
2040                         goto cache_hit;
2041                 }
2042         }
2043         if (unlikely(nr_lock_chains >= MAX_LOCKDEP_CHAINS)) {
2044                 if (!debug_locks_off_graph_unlock())
2045                         return 0;
2046
2047                 printk("BUG: MAX_LOCKDEP_CHAINS too low!\n");
2048                 printk("turning off the locking correctness validator.\n");
2049                 dump_stack();
2050                 return 0;
2051         }
2052         chain = lock_chains + nr_lock_chains++;
2053         chain->chain_key = chain_key;
2054         chain->irq_context = hlock->irq_context;
2055         /* Find the first held_lock of current chain */
2056         hlock_next = hlock;
2057         for (i = curr->lockdep_depth - 1; i >= 0; i--) {
2058                 hlock_curr = curr->held_locks + i;
2059                 if (hlock_curr->irq_context != hlock_next->irq_context)
2060                         break;
2061                 hlock_next = hlock;
2062         }
2063         i++;
2064         chain->depth = curr->lockdep_depth + 1 - i;
2065         if (likely(nr_chain_hlocks + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) {
2066                 chain->base = nr_chain_hlocks;
2067                 nr_chain_hlocks += chain->depth;
2068                 for (j = 0; j < chain->depth - 1; j++, i++) {
2069                         int lock_id = curr->held_locks[i].class_idx - 1;
2070                         chain_hlocks[chain->base + j] = lock_id;
2071                 }
2072                 chain_hlocks[chain->base + j] = class - lock_classes;
2073         }
2074         list_add_tail_rcu(&chain->entry, hash_head);
2075         debug_atomic_inc(chain_lookup_misses);
2076         inc_chains();
2077
2078         return 1;
2079 }
2080
2081 static int validate_chain(struct task_struct *curr, struct lockdep_map *lock,
2082                 struct held_lock *hlock, int chain_head, u64 chain_key)
2083 {
2084         /*
2085          * Trylock needs to maintain the stack of held locks, but it
2086          * does not add new dependencies, because trylock can be done
2087          * in any order.
2088          *
2089          * We look up the chain_key and do the O(N^2) check and update of
2090          * the dependencies only if this is a new dependency chain.
2091          * (If lookup_chain_cache() returns with 1 it acquires
2092          * graph_lock for us)
2093          */
2094         if (!hlock->trylock && (hlock->check == 2) &&
2095             lookup_chain_cache(curr, hlock, chain_key)) {
2096                 /*
2097                  * Check whether last held lock:
2098                  *
2099                  * - is irq-safe, if this lock is irq-unsafe
2100                  * - is softirq-safe, if this lock is hardirq-unsafe
2101                  *
2102                  * And check whether the new lock's dependency graph
2103                  * could lead back to the previous lock.
2104                  *
2105                  * any of these scenarios could lead to a deadlock. If
2106                  * All validations
2107                  */
2108                 int ret = check_deadlock(curr, hlock, lock, hlock->read);
2109
2110                 if (!ret)
2111                         return 0;
2112                 /*
2113                  * Mark recursive read, as we jump over it when
2114                  * building dependencies (just like we jump over
2115                  * trylock entries):
2116                  */
2117                 if (ret == 2)
2118                         hlock->read = 2;
2119                 /*
2120                  * Add dependency only if this lock is not the head
2121                  * of the chain, and if it's not a secondary read-lock:
2122                  */
2123                 if (!chain_head && ret != 2)
2124                         if (!check_prevs_add(curr, hlock))
2125                                 return 0;
2126                 graph_unlock();
2127         } else
2128                 /* after lookup_chain_cache(): */
2129                 if (unlikely(!debug_locks))
2130                         return 0;
2131
2132         return 1;
2133 }
2134 #else
2135 static inline int validate_chain(struct task_struct *curr,
2136                 struct lockdep_map *lock, struct held_lock *hlock,
2137                 int chain_head, u64 chain_key)
2138 {
2139         return 1;
2140 }
2141 #endif
2142
2143 /*
2144  * We are building curr_chain_key incrementally, so double-check
2145  * it from scratch, to make sure that it's done correctly:
2146  */
2147 static void check_chain_key(struct task_struct *curr)
2148 {
2149 #ifdef CONFIG_DEBUG_LOCKDEP
2150         struct held_lock *hlock, *prev_hlock = NULL;
2151         unsigned int i, id;
2152         u64 chain_key = 0;
2153
2154         for (i = 0; i < curr->lockdep_depth; i++) {
2155                 hlock = curr->held_locks + i;
2156                 if (chain_key != hlock->prev_chain_key) {
2157                         debug_locks_off();
2158                         /*
2159                          * We got mighty confused, our chain keys don't match
2160                          * with what we expect, someone trample on our task state?
2161                          */
2162                         WARN(1, "hm#1, depth: %u [%u], %016Lx != %016Lx\n",
2163                                 curr->lockdep_depth, i,
2164                                 (unsigned long long)chain_key,
2165                                 (unsigned long long)hlock->prev_chain_key);
2166                         return;
2167                 }
2168                 id = hlock->class_idx - 1;
2169                 /*
2170                  * Whoops ran out of static storage again?
2171                  */
2172                 if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
2173                         return;
2174
2175                 if (prev_hlock && (prev_hlock->irq_context !=
2176                                                         hlock->irq_context))
2177                         chain_key = 0;
2178                 chain_key = iterate_chain_key(chain_key, id);
2179                 prev_hlock = hlock;
2180         }
2181         if (chain_key != curr->curr_chain_key) {
2182                 debug_locks_off();
2183                 /*
2184                  * More smoking hash instead of calculating it, damn see these
2185                  * numbers float.. I bet that a pink elephant stepped on my memory.
2186                  */
2187                 WARN(1, "hm#2, depth: %u [%u], %016Lx != %016Lx\n",
2188                         curr->lockdep_depth, i,
2189                         (unsigned long long)chain_key,
2190                         (unsigned long long)curr->curr_chain_key);
2191         }
2192 #endif
2193 }
2194
2195 static void
2196 print_usage_bug_scenario(struct held_lock *lock)
2197 {
2198         struct lock_class *class = hlock_class(lock);
2199
2200         printk(" Possible unsafe locking scenario:\n\n");
2201         printk("       CPU0\n");
2202         printk("       ----\n");
2203         printk("  lock(");
2204         __print_lock_name(class);
2205         printk(");\n");
2206         printk("  <Interrupt>\n");
2207         printk("    lock(");
2208         __print_lock_name(class);
2209         printk(");\n");
2210         printk("\n *** DEADLOCK ***\n\n");
2211 }
2212
2213 static int
2214 print_usage_bug(struct task_struct *curr, struct held_lock *this,
2215                 enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
2216 {
2217         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2218                 return 0;
2219
2220         printk("\n");
2221         printk("=================================\n");
2222         printk("[ INFO: inconsistent lock state ]\n");
2223         print_kernel_version();
2224         printk("---------------------------------\n");
2225
2226         printk("inconsistent {%s} -> {%s} usage.\n",
2227                 usage_str[prev_bit], usage_str[new_bit]);
2228
2229         printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] takes:\n",
2230                 curr->comm, task_pid_nr(curr),
2231                 trace_hardirq_context(curr), hardirq_count() >> HARDIRQ_SHIFT,
2232                 trace_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT,
2233                 trace_hardirqs_enabled(curr),
2234                 trace_softirqs_enabled(curr));
2235         print_lock(this);
2236
2237         printk("{%s} state was registered at:\n", usage_str[prev_bit]);
2238         print_stack_trace(hlock_class(this)->usage_traces + prev_bit, 1);
2239
2240         print_irqtrace_events(curr);
2241         printk("\nother info that might help us debug this:\n");
2242         print_usage_bug_scenario(this);
2243
2244         lockdep_print_held_locks(curr);
2245
2246         printk("\nstack backtrace:\n");
2247         dump_stack();
2248
2249         return 0;
2250 }
2251
2252 /*
2253  * Print out an error if an invalid bit is set:
2254  */
2255 static inline int
2256 valid_state(struct task_struct *curr, struct held_lock *this,
2257             enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit)
2258 {
2259         if (unlikely(hlock_class(this)->usage_mask & (1 << bad_bit)))
2260                 return print_usage_bug(curr, this, bad_bit, new_bit);
2261         return 1;
2262 }
2263
2264 static int mark_lock(struct task_struct *curr, struct held_lock *this,
2265                      enum lock_usage_bit new_bit);
2266
2267 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
2268
2269 /*
2270  * print irq inversion bug:
2271  */
2272 static int
2273 print_irq_inversion_bug(struct task_struct *curr,
2274                         struct lock_list *root, struct lock_list *other,
2275                         struct held_lock *this, int forwards,
2276                         const char *irqclass)
2277 {
2278         struct lock_list *entry = other;
2279         struct lock_list *middle = NULL;
2280         int depth;
2281
2282         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2283                 return 0;
2284
2285         printk("\n");
2286         printk("=========================================================\n");
2287         printk("[ INFO: possible irq lock inversion dependency detected ]\n");
2288         print_kernel_version();
2289         printk("---------------------------------------------------------\n");
2290         printk("%s/%d just changed the state of lock:\n",
2291                 curr->comm, task_pid_nr(curr));
2292         print_lock(this);
2293         if (forwards)
2294                 printk("but this lock took another, %s-unsafe lock in the past:\n", irqclass);
2295         else
2296                 printk("but this lock was taken by another, %s-safe lock in the past:\n", irqclass);
2297         print_lock_name(other->class);
2298         printk("\n\nand interrupts could create inverse lock ordering between them.\n\n");
2299
2300         printk("\nother info that might help us debug this:\n");
2301
2302         /* Find a middle lock (if one exists) */
2303         depth = get_lock_depth(other);
2304         do {
2305                 if (depth == 0 && (entry != root)) {
2306                         printk("lockdep:%s bad path found in chain graph\n", __func__);
2307                         break;
2308                 }
2309                 middle = entry;
2310                 entry = get_lock_parent(entry);
2311                 depth--;
2312         } while (entry && entry != root && (depth >= 0));
2313         if (forwards)
2314                 print_irq_lock_scenario(root, other,
2315                         middle ? middle->class : root->class, other->class);
2316         else
2317                 print_irq_lock_scenario(other, root,
2318                         middle ? middle->class : other->class, root->class);
2319
2320         lockdep_print_held_locks(curr);
2321
2322         printk("\nthe shortest dependencies between 2nd lock and 1st lock:\n");
2323         if (!save_trace(&root->trace))
2324                 return 0;
2325         print_shortest_lock_dependencies(other, root);
2326
2327         printk("\nstack backtrace:\n");
2328         dump_stack();
2329
2330         return 0;
2331 }
2332
2333 /*
2334  * Prove that in the forwards-direction subgraph starting at <this>
2335  * there is no lock matching <mask>:
2336  */
2337 static int
2338 check_usage_forwards(struct task_struct *curr, struct held_lock *this,
2339                      enum lock_usage_bit bit, const char *irqclass)
2340 {
2341         int ret;
2342         struct lock_list root;
2343         struct lock_list *uninitialized_var(target_entry);
2344
2345         root.parent = NULL;
2346         root.class = hlock_class(this);
2347         ret = find_usage_forwards(&root, bit, &target_entry);
2348         if (ret < 0)
2349                 return print_bfs_bug(ret);
2350         if (ret == 1)
2351                 return ret;
2352
2353         return print_irq_inversion_bug(curr, &root, target_entry,
2354                                         this, 1, irqclass);
2355 }
2356
2357 /*
2358  * Prove that in the backwards-direction subgraph starting at <this>
2359  * there is no lock matching <mask>:
2360  */
2361 static int
2362 check_usage_backwards(struct task_struct *curr, struct held_lock *this,
2363                       enum lock_usage_bit bit, const char *irqclass)
2364 {
2365         int ret;
2366         struct lock_list root;
2367         struct lock_list *uninitialized_var(target_entry);
2368
2369         root.parent = NULL;
2370         root.class = hlock_class(this);
2371         ret = find_usage_backwards(&root, bit, &target_entry);
2372         if (ret < 0)
2373                 return print_bfs_bug(ret);
2374         if (ret == 1)
2375                 return ret;
2376
2377         return print_irq_inversion_bug(curr, &root, target_entry,
2378                                         this, 0, irqclass);
2379 }
2380
2381 void print_irqtrace_events(struct task_struct *curr)
2382 {
2383         printk("irq event stamp: %u\n", curr->irq_events);
2384         printk("hardirqs last  enabled at (%u): ", curr->hardirq_enable_event);
2385         print_ip_sym(curr->hardirq_enable_ip);
2386         printk("hardirqs last disabled at (%u): ", curr->hardirq_disable_event);
2387         print_ip_sym(curr->hardirq_disable_ip);
2388         printk("softirqs last  enabled at (%u): ", curr->softirq_enable_event);
2389         print_ip_sym(curr->softirq_enable_ip);
2390         printk("softirqs last disabled at (%u): ", curr->softirq_disable_event);
2391         print_ip_sym(curr->softirq_disable_ip);
2392 }
2393
2394 static int HARDIRQ_verbose(struct lock_class *class)
2395 {
2396 #if HARDIRQ_VERBOSE
2397         return class_filter(class);
2398 #endif
2399         return 0;
2400 }
2401
2402 static int SOFTIRQ_verbose(struct lock_class *class)
2403 {
2404 #if SOFTIRQ_VERBOSE
2405         return class_filter(class);
2406 #endif
2407         return 0;
2408 }
2409
2410 static int RECLAIM_FS_verbose(struct lock_class *class)
2411 {
2412 #if RECLAIM_VERBOSE
2413         return class_filter(class);
2414 #endif
2415         return 0;
2416 }
2417
2418 #define STRICT_READ_CHECKS      1
2419
2420 static int (*state_verbose_f[])(struct lock_class *class) = {
2421 #define LOCKDEP_STATE(__STATE) \
2422         __STATE##_verbose,
2423 #include "lockdep_states.h"
2424 #undef LOCKDEP_STATE
2425 };
2426
2427 static inline int state_verbose(enum lock_usage_bit bit,
2428                                 struct lock_class *class)
2429 {
2430         return state_verbose_f[bit >> 2](class);
2431 }
2432
2433 typedef int (*check_usage_f)(struct task_struct *, struct held_lock *,
2434                              enum lock_usage_bit bit, const char *name);
2435
2436 static int
2437 mark_lock_irq(struct task_struct *curr, struct held_lock *this,
2438                 enum lock_usage_bit new_bit)
2439 {
2440         int excl_bit = exclusive_bit(new_bit);
2441         int read = new_bit & 1;
2442         int dir = new_bit & 2;
2443
2444         /*
2445          * mark USED_IN has to look forwards -- to ensure no dependency
2446          * has ENABLED state, which would allow recursion deadlocks.
2447          *
2448          * mark ENABLED has to look backwards -- to ensure no dependee
2449          * has USED_IN state, which, again, would allow  recursion deadlocks.
2450          */
2451         check_usage_f usage = dir ?
2452                 check_usage_backwards : check_usage_forwards;
2453
2454         /*
2455          * Validate that this particular lock does not have conflicting
2456          * usage states.
2457          */
2458         if (!valid_state(curr, this, new_bit, excl_bit))
2459                 return 0;
2460
2461         /*
2462          * Validate that the lock dependencies don't have conflicting usage
2463          * states.
2464          */
2465         if ((!read || !dir || STRICT_READ_CHECKS) &&
2466                         !usage(curr, this, excl_bit, state_name(new_bit & ~1)))
2467                 return 0;
2468
2469         /*
2470          * Check for read in write conflicts
2471          */
2472         if (!read) {
2473                 if (!valid_state(curr, this, new_bit, excl_bit + 1))
2474                         return 0;
2475
2476                 if (STRICT_READ_CHECKS &&
2477                         !usage(curr, this, excl_bit + 1,
2478                                 state_name(new_bit + 1)))
2479                         return 0;
2480         }
2481
2482         if (state_verbose(new_bit, hlock_class(this)))
2483                 return 2;
2484
2485         return 1;
2486 }
2487
2488 enum mark_type {
2489 #define LOCKDEP_STATE(__STATE)  __STATE,
2490 #include "lockdep_states.h"
2491 #undef LOCKDEP_STATE
2492 };
2493
2494 /*
2495  * Mark all held locks with a usage bit:
2496  */
2497 static int
2498 mark_held_locks(struct task_struct *curr, enum mark_type mark)
2499 {
2500         enum lock_usage_bit usage_bit;
2501         struct held_lock *hlock;
2502         int i;
2503
2504         for (i = 0; i < curr->lockdep_depth; i++) {
2505                 hlock = curr->held_locks + i;
2506
2507                 usage_bit = 2 + (mark << 2); /* ENABLED */
2508                 if (hlock->read)
2509                         usage_bit += 1; /* READ */
2510
2511                 BUG_ON(usage_bit >= LOCK_USAGE_STATES);
2512
2513                 if (hlock_class(hlock)->key == __lockdep_no_validate__.subkeys)
2514                         continue;
2515
2516                 if (!mark_lock(curr, hlock, usage_bit))
2517                         return 0;
2518         }
2519
2520         return 1;
2521 }
2522
2523 /*
2524  * Hardirqs will be enabled:
2525  */
2526 static void __trace_hardirqs_on_caller(unsigned long ip)
2527 {
2528         struct task_struct *curr = current;
2529
2530         /* we'll do an OFF -> ON transition: */
2531         curr->hardirqs_enabled = 1;
2532
2533         /*
2534          * We are going to turn hardirqs on, so set the
2535          * usage bit for all held locks:
2536          */
2537         if (!mark_held_locks(curr, HARDIRQ))
2538                 return;
2539         /*
2540          * If we have softirqs enabled, then set the usage
2541          * bit for all held locks. (disabled hardirqs prevented
2542          * this bit from being set before)
2543          */
2544         if (curr->softirqs_enabled)
2545                 if (!mark_held_locks(curr, SOFTIRQ))
2546                         return;
2547
2548         curr->hardirq_enable_ip = ip;
2549         curr->hardirq_enable_event = ++curr->irq_events;
2550         debug_atomic_inc(hardirqs_on_events);
2551 }
2552
2553 void trace_hardirqs_on_caller(unsigned long ip)
2554 {
2555         time_hardirqs_on(CALLER_ADDR0, ip);
2556
2557         if (unlikely(!debug_locks || current->lockdep_recursion))
2558                 return;
2559
2560         if (unlikely(current->hardirqs_enabled)) {
2561                 /*
2562                  * Neither irq nor preemption are disabled here
2563                  * so this is racy by nature but losing one hit
2564                  * in a stat is not a big deal.
2565                  */
2566                 __debug_atomic_inc(redundant_hardirqs_on);
2567                 return;
2568         }
2569
2570         /*
2571          * We're enabling irqs and according to our state above irqs weren't
2572          * already enabled, yet we find the hardware thinks they are in fact
2573          * enabled.. someone messed up their IRQ state tracing.
2574          */
2575         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2576                 return;
2577
2578         /*
2579          * See the fine text that goes along with this variable definition.
2580          */
2581         if (DEBUG_LOCKS_WARN_ON(unlikely(early_boot_irqs_disabled)))
2582                 return;
2583
2584         /*
2585          * Can't allow enabling interrupts while in an interrupt handler,
2586          * that's general bad form and such. Recursion, limited stack etc..
2587          */
2588         if (DEBUG_LOCKS_WARN_ON(current->hardirq_context))
2589                 return;
2590
2591         current->lockdep_recursion = 1;
2592         __trace_hardirqs_on_caller(ip);
2593         current->lockdep_recursion = 0;
2594 }
2595 EXPORT_SYMBOL(trace_hardirqs_on_caller);
2596
2597 void trace_hardirqs_on(void)
2598 {
2599         trace_hardirqs_on_caller(CALLER_ADDR0);
2600 }
2601 EXPORT_SYMBOL(trace_hardirqs_on);
2602
2603 /*
2604  * Hardirqs were disabled:
2605  */
2606 void trace_hardirqs_off_caller(unsigned long ip)
2607 {
2608         struct task_struct *curr = current;
2609
2610         time_hardirqs_off(CALLER_ADDR0, ip);
2611
2612         if (unlikely(!debug_locks || current->lockdep_recursion))
2613                 return;
2614
2615         /*
2616          * So we're supposed to get called after you mask local IRQs, but for
2617          * some reason the hardware doesn't quite think you did a proper job.
2618          */
2619         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2620                 return;
2621
2622         if (curr->hardirqs_enabled) {
2623                 /*
2624                  * We have done an ON -> OFF transition:
2625                  */
2626                 curr->hardirqs_enabled = 0;
2627                 curr->hardirq_disable_ip = ip;
2628                 curr->hardirq_disable_event = ++curr->irq_events;
2629                 debug_atomic_inc(hardirqs_off_events);
2630         } else
2631                 debug_atomic_inc(redundant_hardirqs_off);
2632 }
2633 EXPORT_SYMBOL(trace_hardirqs_off_caller);
2634
2635 void trace_hardirqs_off(void)
2636 {
2637         trace_hardirqs_off_caller(CALLER_ADDR0);
2638 }
2639 EXPORT_SYMBOL(trace_hardirqs_off);
2640
2641 /*
2642  * Softirqs will be enabled:
2643  */
2644 void trace_softirqs_on(unsigned long ip)
2645 {
2646         struct task_struct *curr = current;
2647
2648         if (unlikely(!debug_locks || current->lockdep_recursion))
2649                 return;
2650
2651         /*
2652          * We fancy IRQs being disabled here, see softirq.c, avoids
2653          * funny state and nesting things.
2654          */
2655         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2656                 return;
2657
2658         if (curr->softirqs_enabled) {
2659                 debug_atomic_inc(redundant_softirqs_on);
2660                 return;
2661         }
2662
2663         current->lockdep_recursion = 1;
2664         /*
2665          * We'll do an OFF -> ON transition:
2666          */
2667         curr->softirqs_enabled = 1;
2668         curr->softirq_enable_ip = ip;
2669         curr->softirq_enable_event = ++curr->irq_events;
2670         debug_atomic_inc(softirqs_on_events);
2671         /*
2672          * We are going to turn softirqs on, so set the
2673          * usage bit for all held locks, if hardirqs are
2674          * enabled too:
2675          */
2676         if (curr->hardirqs_enabled)
2677                 mark_held_locks(curr, SOFTIRQ);
2678         current->lockdep_recursion = 0;
2679 }
2680
2681 /*
2682  * Softirqs were disabled:
2683  */
2684 void trace_softirqs_off(unsigned long ip)
2685 {
2686         struct task_struct *curr = current;
2687
2688         if (unlikely(!debug_locks || current->lockdep_recursion))
2689                 return;
2690
2691         /*
2692          * We fancy IRQs being disabled here, see softirq.c
2693          */
2694         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2695                 return;
2696
2697         if (curr->softirqs_enabled) {
2698                 /*
2699                  * We have done an ON -> OFF transition:
2700                  */
2701                 curr->softirqs_enabled = 0;
2702                 curr->softirq_disable_ip = ip;
2703                 curr->softirq_disable_event = ++curr->irq_events;
2704                 debug_atomic_inc(softirqs_off_events);
2705                 /*
2706                  * Whoops, we wanted softirqs off, so why aren't they?
2707                  */
2708                 DEBUG_LOCKS_WARN_ON(!softirq_count());
2709         } else
2710                 debug_atomic_inc(redundant_softirqs_off);
2711 }
2712
2713 static void __lockdep_trace_alloc(gfp_t gfp_mask, unsigned long flags)
2714 {
2715         struct task_struct *curr = current;
2716
2717         if (unlikely(!debug_locks))
2718                 return;
2719
2720         /* no reclaim without waiting on it */
2721         if (!(gfp_mask & __GFP_WAIT))
2722                 return;
2723
2724         /* this guy won't enter reclaim */
2725         if ((curr->flags & PF_MEMALLOC) && !(gfp_mask & __GFP_NOMEMALLOC))
2726                 return;
2727
2728         /* We're only interested __GFP_FS allocations for now */
2729         if (!(gfp_mask & __GFP_FS))
2730                 return;
2731
2732         /*
2733          * Oi! Can't be having __GFP_FS allocations with IRQs disabled.
2734          */
2735         if (DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags)))
2736                 return;
2737
2738         mark_held_locks(curr, RECLAIM_FS);
2739 }
2740
2741 static void check_flags(unsigned long flags);
2742
2743 void lockdep_trace_alloc(gfp_t gfp_mask)
2744 {
2745         unsigned long flags;
2746
2747         if (unlikely(current->lockdep_recursion))
2748                 return;
2749
2750         raw_local_irq_save(flags);
2751         check_flags(flags);
2752         current->lockdep_recursion = 1;
2753         __lockdep_trace_alloc(gfp_mask, flags);
2754         current->lockdep_recursion = 0;
2755         raw_local_irq_restore(flags);
2756 }
2757
2758 static int mark_irqflags(struct task_struct *curr, struct held_lock *hlock)
2759 {
2760         /*
2761          * If non-trylock use in a hardirq or softirq context, then
2762          * mark the lock as used in these contexts:
2763          */
2764         if (!hlock->trylock) {
2765                 if (hlock->read) {
2766                         if (curr->hardirq_context)
2767                                 if (!mark_lock(curr, hlock,
2768                                                 LOCK_USED_IN_HARDIRQ_READ))
2769                                         return 0;
2770                         if (curr->softirq_context)
2771                                 if (!mark_lock(curr, hlock,
2772                                                 LOCK_USED_IN_SOFTIRQ_READ))
2773                                         return 0;
2774                 } else {
2775                         if (curr->hardirq_context)
2776                                 if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ))
2777                                         return 0;
2778                         if (curr->softirq_context)
2779                                 if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ))
2780                                         return 0;
2781                 }
2782         }
2783         if (!hlock->hardirqs_off) {
2784                 if (hlock->read) {
2785                         if (!mark_lock(curr, hlock,
2786                                         LOCK_ENABLED_HARDIRQ_READ))
2787                                 return 0;
2788                         if (curr->softirqs_enabled)
2789                                 if (!mark_lock(curr, hlock,
2790                                                 LOCK_ENABLED_SOFTIRQ_READ))
2791                                         return 0;
2792                 } else {
2793                         if (!mark_lock(curr, hlock,
2794                                         LOCK_ENABLED_HARDIRQ))
2795                                 return 0;
2796                         if (curr->softirqs_enabled)
2797                                 if (!mark_lock(curr, hlock,
2798                                                 LOCK_ENABLED_SOFTIRQ))
2799                                         return 0;
2800                 }
2801         }
2802
2803         /*
2804          * We reuse the irq context infrastructure more broadly as a general
2805          * context checking code. This tests GFP_FS recursion (a lock taken
2806          * during reclaim for a GFP_FS allocation is held over a GFP_FS
2807          * allocation).
2808          */
2809         if (!hlock->trylock && (curr->lockdep_reclaim_gfp & __GFP_FS)) {
2810                 if (hlock->read) {
2811                         if (!mark_lock(curr, hlock, LOCK_USED_IN_RECLAIM_FS_READ))
2812                                         return 0;
2813                 } else {
2814                         if (!mark_lock(curr, hlock, LOCK_USED_IN_RECLAIM_FS))
2815                                         return 0;
2816                 }
2817         }
2818
2819         return 1;
2820 }
2821
2822 static int separate_irq_context(struct task_struct *curr,
2823                 struct held_lock *hlock)
2824 {
2825         unsigned int depth = curr->lockdep_depth;
2826
2827         /*
2828          * Keep track of points where we cross into an interrupt context:
2829          */
2830         hlock->irq_context = 2*(curr->hardirq_context ? 1 : 0) +
2831                                 curr->softirq_context;
2832         if (depth) {
2833                 struct held_lock *prev_hlock;
2834
2835                 prev_hlock = curr->held_locks + depth-1;
2836                 /*
2837                  * If we cross into another context, reset the
2838                  * hash key (this also prevents the checking and the
2839                  * adding of the dependency to 'prev'):
2840                  */
2841                 if (prev_hlock->irq_context != hlock->irq_context)
2842                         return 1;
2843         }
2844         return 0;
2845 }
2846
2847 #else /* defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING) */
2848
2849 static inline
2850 int mark_lock_irq(struct task_struct *curr, struct held_lock *this,
2851                 enum lock_usage_bit new_bit)
2852 {
2853         WARN_ON(1); /* Impossible innit? when we don't have TRACE_IRQFLAG */
2854         return 1;
2855 }
2856
2857 static inline int mark_irqflags(struct task_struct *curr,
2858                 struct held_lock *hlock)
2859 {
2860         return 1;
2861 }
2862
2863 static inline int separate_irq_context(struct task_struct *curr,
2864                 struct held_lock *hlock)
2865 {
2866         return 0;
2867 }
2868
2869 void lockdep_trace_alloc(gfp_t gfp_mask)
2870 {
2871 }
2872
2873 #endif /* defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING) */
2874
2875 /*
2876  * Mark a lock with a usage bit, and validate the state transition:
2877  */
2878 static int mark_lock(struct task_struct *curr, struct held_lock *this,
2879                              enum lock_usage_bit new_bit)
2880 {
2881         unsigned int new_mask = 1 << new_bit, ret = 1;
2882
2883         /*
2884          * If already set then do not dirty the cacheline,
2885          * nor do any checks:
2886          */
2887         if (likely(hlock_class(this)->usage_mask & new_mask))
2888                 return 1;
2889
2890         if (!graph_lock())
2891                 return 0;
2892         /*
2893          * Make sure we didn't race:
2894          */
2895         if (unlikely(hlock_class(this)->usage_mask & new_mask)) {
2896                 graph_unlock();
2897                 return 1;
2898         }
2899
2900         hlock_class(this)->usage_mask |= new_mask;
2901
2902         if (!save_trace(hlock_class(this)->usage_traces + new_bit))
2903                 return 0;
2904
2905         switch (new_bit) {
2906 #define LOCKDEP_STATE(__STATE)                  \
2907         case LOCK_USED_IN_##__STATE:            \
2908         case LOCK_USED_IN_##__STATE##_READ:     \
2909         case LOCK_ENABLED_##__STATE:            \
2910         case LOCK_ENABLED_##__STATE##_READ:
2911 #include "lockdep_states.h"
2912 #undef LOCKDEP_STATE
2913                 ret = mark_lock_irq(curr, this, new_bit);
2914                 if (!ret)
2915                         return 0;
2916                 break;
2917         case LOCK_USED:
2918                 debug_atomic_dec(nr_unused_locks);
2919                 break;
2920         default:
2921                 if (!debug_locks_off_graph_unlock())
2922                         return 0;
2923                 WARN_ON(1);
2924                 return 0;
2925         }
2926
2927         graph_unlock();
2928
2929         /*
2930          * We must printk outside of the graph_lock:
2931          */
2932         if (ret == 2) {
2933                 printk("\nmarked lock as {%s}:\n", usage_str[new_bit]);
2934                 print_lock(this);
2935                 print_irqtrace_events(curr);
2936                 dump_stack();
2937         }
2938
2939         return ret;
2940 }
2941
2942 /*
2943  * Initialize a lock instance's lock-class mapping info:
2944  */
2945 void lockdep_init_map(struct lockdep_map *lock, const char *name,
2946                       struct lock_class_key *key, int subclass)
2947 {
2948         int i;
2949
2950         kmemcheck_mark_initialized(lock, sizeof(*lock));
2951
2952         for (i = 0; i < NR_LOCKDEP_CACHING_CLASSES; i++)
2953                 lock->class_cache[i] = NULL;
2954
2955 #ifdef CONFIG_LOCK_STAT
2956         lock->cpu = raw_smp_processor_id();
2957 #endif
2958
2959         /*
2960          * Can't be having no nameless bastards around this place!
2961          */
2962         if (DEBUG_LOCKS_WARN_ON(!name)) {
2963                 lock->name = "NULL";
2964                 return;
2965         }
2966
2967         lock->name = name;
2968
2969         /*
2970          * No key, no joy, we need to hash something.
2971          */
2972         if (DEBUG_LOCKS_WARN_ON(!key))
2973                 return;
2974         /*
2975          * Sanity check, the lock-class key must be persistent:
2976          */
2977         if (!static_obj(key)) {
2978                 printk("BUG: key %p not in .data!\n", key);
2979                 /*
2980                  * What it says above ^^^^^, I suggest you read it.
2981                  */
2982                 DEBUG_LOCKS_WARN_ON(1);
2983                 return;
2984         }
2985         lock->key = key;
2986
2987         if (unlikely(!debug_locks))
2988                 return;
2989
2990         if (subclass)
2991                 register_lock_class(lock, subclass, 1);
2992 }
2993 EXPORT_SYMBOL_GPL(lockdep_init_map);
2994
2995 struct lock_class_key __lockdep_no_validate__;
2996
2997 /*
2998  * This gets called for every mutex_lock*()/spin_lock*() operation.
2999  * We maintain the dependency maps and validate the locking attempt:
3000  */
3001 static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
3002                           int trylock, int read, int check, int hardirqs_off,
3003                           struct lockdep_map *nest_lock, unsigned long ip,
3004                           int references)
3005 {
3006         struct task_struct *curr = current;
3007         struct lock_class *class = NULL;
3008         struct held_lock *hlock;
3009         unsigned int depth, id;
3010         int chain_head = 0;
3011         int class_idx;
3012         u64 chain_key;
3013
3014         if (!prove_locking)
3015                 check = 1;
3016
3017         if (unlikely(!debug_locks))
3018                 return 0;
3019
3020         /*
3021          * Lockdep should run with IRQs disabled, otherwise we could
3022          * get an interrupt which would want to take locks, which would
3023          * end up in lockdep and have you got a head-ache already?
3024          */
3025         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
3026                 return 0;
3027
3028         if (lock->key == &__lockdep_no_validate__)
3029                 check = 1;
3030
3031         if (subclass < NR_LOCKDEP_CACHING_CLASSES)
3032                 class = lock->class_cache[subclass];
3033         /*
3034          * Not cached?
3035          */
3036         if (unlikely(!class)) {
3037                 class = register_lock_class(lock, subclass, 0);
3038                 if (!class)
3039                         return 0;
3040         }
3041         atomic_inc((atomic_t *)&class->ops);
3042         if (very_verbose(class)) {
3043                 printk("\nacquire class [%p] %s", class->key, class->name);
3044                 if (class->name_version > 1)
3045                         printk("#%d", class->name_version);
3046                 printk("\n");
3047                 dump_stack();
3048         }
3049
3050         /*
3051          * Add the lock to the list of currently held locks.
3052          * (we dont increase the depth just yet, up until the
3053          * dependency checks are done)
3054          */
3055         depth = curr->lockdep_depth;
3056         /*
3057          * Ran out of static storage for our per-task lock stack again have we?
3058          */
3059         if (DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH))
3060                 return 0;
3061
3062         class_idx = class - lock_classes + 1;
3063
3064         if (depth) {
3065                 hlock = curr->held_locks + depth - 1;
3066                 if (hlock->class_idx == class_idx && nest_lock) {
3067                         if (hlock->references)
3068                                 hlock->references++;
3069                         else
3070                                 hlock->references = 2;
3071
3072                         return 1;
3073                 }
3074         }
3075
3076         hlock = curr->held_locks + depth;
3077         /*
3078          * Plain impossible, we just registered it and checked it weren't no
3079          * NULL like.. I bet this mushroom I ate was good!
3080          */
3081         if (DEBUG_LOCKS_WARN_ON(!class))
3082                 return 0;
3083         hlock->class_idx = class_idx;
3084         hlock->acquire_ip = ip;
3085         hlock->instance = lock;
3086         hlock->nest_lock = nest_lock;
3087         hlock->trylock = trylock;
3088         hlock->read = read;
3089         hlock->check = check;
3090         hlock->hardirqs_off = !!hardirqs_off;
3091         hlock->references = references;
3092 #ifdef CONFIG_LOCK_STAT
3093         hlock->waittime_stamp = 0;
3094         hlock->holdtime_stamp = lockstat_clock();
3095 #endif
3096
3097         if (check == 2 && !mark_irqflags(curr, hlock))
3098                 return 0;
3099
3100         /* mark it as used: */
3101         if (!mark_lock(curr, hlock, LOCK_USED))
3102                 return 0;
3103
3104         /*
3105          * Calculate the chain hash: it's the combined hash of all the
3106          * lock keys along the dependency chain. We save the hash value
3107          * at every step so that we can get the current hash easily
3108          * after unlock. The chain hash is then used to cache dependency
3109          * results.
3110          *
3111          * The 'key ID' is what is the most compact key value to drive
3112          * the hash, not class->key.
3113          */
3114         id = class - lock_classes;
3115         /*
3116          * Whoops, we did it again.. ran straight out of our static allocation.
3117          */
3118         if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
3119                 return 0;
3120
3121         chain_key = curr->curr_chain_key;
3122         if (!depth) {
3123                 /*
3124                  * How can we have a chain hash when we ain't got no keys?!
3125                  */
3126                 if (DEBUG_LOCKS_WARN_ON(chain_key != 0))
3127                         return 0;
3128                 chain_head = 1;
3129         }
3130
3131         hlock->prev_chain_key = chain_key;
3132         if (separate_irq_context(curr, hlock)) {
3133                 chain_key = 0;
3134                 chain_head = 1;
3135         }
3136         chain_key = iterate_chain_key(chain_key, id);
3137
3138         if (!validate_chain(curr, lock, hlock, chain_head, chain_key))
3139                 return 0;
3140
3141         curr->curr_chain_key = chain_key;
3142         curr->lockdep_depth++;
3143         check_chain_key(curr);
3144 #ifdef CONFIG_DEBUG_LOCKDEP
3145         if (unlikely(!debug_locks))
3146                 return 0;
3147 #endif
3148         if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
3149                 debug_locks_off();
3150                 printk("BUG: MAX_LOCK_DEPTH too low!\n");
3151                 printk("turning off the locking correctness validator.\n");
3152                 dump_stack();
3153                 return 0;
3154         }
3155
3156         if (unlikely(curr->lockdep_depth > max_lockdep_depth))
3157                 max_lockdep_depth = curr->lockdep_depth;
3158
3159         return 1;
3160 }
3161
3162 static int
3163 print_unlock_inbalance_bug(struct task_struct *curr, struct lockdep_map *lock,
3164                            unsigned long ip)
3165 {
3166         if (!debug_locks_off())
3167                 return 0;
3168         if (debug_locks_silent)
3169                 return 0;
3170
3171         printk("\n");
3172         printk("=====================================\n");
3173         printk("[ BUG: bad unlock balance detected! ]\n");
3174         printk("-------------------------------------\n");
3175         printk("%s/%d is trying to release lock (",
3176                 curr->comm, task_pid_nr(curr));
3177         print_lockdep_cache(lock);
3178         printk(") at:\n");
3179         print_ip_sym(ip);
3180         printk("but there are no more locks to release!\n");
3181         printk("\nother info that might help us debug this:\n");
3182         lockdep_print_held_locks(curr);
3183
3184         printk("\nstack backtrace:\n");
3185         dump_stack();
3186
3187         return 0;
3188 }
3189
3190 /*
3191  * Common debugging checks for both nested and non-nested unlock:
3192  */
3193 static int check_unlock(struct task_struct *curr, struct lockdep_map *lock,
3194                         unsigned long ip)
3195 {
3196         if (unlikely(!debug_locks))
3197                 return 0;
3198         /*
3199          * Lockdep should run with IRQs disabled, recursion, head-ache, etc..
3200          */
3201         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
3202                 return 0;
3203
3204         if (curr->lockdep_depth <= 0)
3205                 return print_unlock_inbalance_bug(curr, lock, ip);
3206
3207         return 1;
3208 }
3209
3210 static int match_held_lock(struct held_lock *hlock, struct lockdep_map *lock)
3211 {
3212         if (hlock->instance == lock)
3213                 return 1;
3214
3215         if (hlock->references) {
3216                 struct lock_class *class = lock->class_cache[0];
3217
3218                 if (!class)
3219                         class = look_up_lock_class(lock, 0);
3220
3221                 /*
3222                  * If look_up_lock_class() failed to find a class, we're trying
3223                  * to test if we hold a lock that has never yet been acquired.
3224                  * Clearly if the lock hasn't been acquired _ever_, we're not
3225                  * holding it either, so report failure.
3226                  */
3227                 if (!class)
3228                         return 0;
3229
3230                 /*
3231                  * References, but not a lock we're actually ref-counting?
3232                  * State got messed up, follow the sites that change ->references
3233                  * and try to make sense of it.
3234                  */
3235                 if (DEBUG_LOCKS_WARN_ON(!hlock->nest_lock))
3236                         return 0;
3237
3238                 if (hlock->class_idx == class - lock_classes + 1)
3239                         return 1;
3240         }
3241
3242         return 0;
3243 }
3244
3245 static int
3246 __lock_set_class(struct lockdep_map *lock, const char *name,
3247                  struct lock_class_key *key, unsigned int subclass,
3248                  unsigned long ip)
3249 {
3250         struct task_struct *curr = current;
3251         struct held_lock *hlock, *prev_hlock;
3252         struct lock_class *class;
3253         unsigned int depth;
3254         int i;
3255
3256         depth = curr->lockdep_depth;
3257         /*
3258          * This function is about (re)setting the class of a held lock,
3259          * yet we're not actually holding any locks. Naughty user!
3260          */
3261         if (DEBUG_LOCKS_WARN_ON(!depth))
3262                 return 0;
3263
3264         prev_hlock = NULL;
3265         for (i = depth-1; i >= 0; i--) {
3266                 hlock = curr->held_locks + i;
3267                 /*
3268                  * We must not cross into another context:
3269                  */
3270                 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3271                         break;
3272                 if (match_held_lock(hlock, lock))
3273                         goto found_it;
3274                 prev_hlock = hlock;
3275         }
3276         return print_unlock_inbalance_bug(curr, lock, ip);
3277
3278 found_it:
3279         lockdep_init_map(lock, name, key, 0);
3280         class = register_lock_class(lock, subclass, 0);
3281         hlock->class_idx = class - lock_classes + 1;
3282
3283         curr->lockdep_depth = i;
3284         curr->curr_chain_key = hlock->prev_chain_key;
3285
3286         for (; i < depth; i++) {
3287                 hlock = curr->held_locks + i;
3288                 if (!__lock_acquire(hlock->instance,
3289                         hlock_class(hlock)->subclass, hlock->trylock,
3290                                 hlock->read, hlock->check, hlock->hardirqs_off,
3291                                 hlock->nest_lock, hlock->acquire_ip,
3292                                 hlock->references))
3293                         return 0;
3294         }
3295
3296         /*
3297          * I took it apart and put it back together again, except now I have
3298          * these 'spare' parts.. where shall I put them.
3299          */
3300         if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth))
3301                 return 0;
3302         return 1;
3303 }
3304
3305 /*
3306  * Remove the lock to the list of currently held locks in a
3307  * potentially non-nested (out of order) manner. This is a
3308  * relatively rare operation, as all the unlock APIs default
3309  * to nested mode (which uses lock_release()):
3310  */
3311 static int
3312 lock_release_non_nested(struct task_struct *curr,
3313                         struct lockdep_map *lock, unsigned long ip)
3314 {
3315         struct held_lock *hlock, *prev_hlock;
3316         unsigned int depth;
3317         int i;
3318
3319         /*
3320          * Check whether the lock exists in the current stack
3321          * of held locks:
3322          */
3323         depth = curr->lockdep_depth;
3324         /*
3325          * So we're all set to release this lock.. wait what lock? We don't
3326          * own any locks, you've been drinking again?
3327          */
3328         if (DEBUG_LOCKS_WARN_ON(!depth))
3329                 return 0;
3330
3331         prev_hlock = NULL;
3332         for (i = depth-1; i >= 0; i--) {
3333                 hlock = curr->held_locks + i;
3334                 /*
3335                  * We must not cross into another context:
3336                  */
3337                 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3338                         break;
3339                 if (match_held_lock(hlock, lock))
3340                         goto found_it;
3341                 prev_hlock = hlock;
3342         }
3343         return print_unlock_inbalance_bug(curr, lock, ip);
3344
3345 found_it:
3346         if (hlock->instance == lock)
3347                 lock_release_holdtime(hlock);
3348
3349         if (hlock->references) {
3350                 hlock->references--;
3351                 if (hlock->references) {
3352                         /*
3353                          * We had, and after removing one, still have
3354                          * references, the current lock stack is still
3355                          * valid. We're done!
3356                          */
3357                         return 1;
3358                 }
3359         }
3360
3361         /*
3362          * We have the right lock to unlock, 'hlock' points to it.
3363          * Now we remove it from the stack, and add back the other
3364          * entries (if any), recalculating the hash along the way:
3365          */
3366
3367         curr->lockdep_depth = i;
3368         curr->curr_chain_key = hlock->prev_chain_key;
3369
3370         for (i++; i < depth; i++) {
3371                 hlock = curr->held_locks + i;
3372                 if (!__lock_acquire(hlock->instance,
3373                         hlock_class(hlock)->subclass, hlock->trylock,
3374                                 hlock->read, hlock->check, hlock->hardirqs_off,
3375                                 hlock->nest_lock, hlock->acquire_ip,
3376                                 hlock->references))
3377                         return 0;
3378         }
3379
3380         /*
3381          * We had N bottles of beer on the wall, we drank one, but now
3382          * there's not N-1 bottles of beer left on the wall...
3383          */
3384         if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - 1))
3385                 return 0;
3386         return 1;
3387 }
3388
3389 /*
3390  * Remove the lock to the list of currently held locks - this gets
3391  * called on mutex_unlock()/spin_unlock*() (or on a failed
3392  * mutex_lock_interruptible()). This is done for unlocks that nest
3393  * perfectly. (i.e. the current top of the lock-stack is unlocked)
3394  */
3395 static int lock_release_nested(struct task_struct *curr,
3396                                struct lockdep_map *lock, unsigned long ip)
3397 {
3398         struct held_lock *hlock;
3399         unsigned int depth;
3400
3401         /*
3402          * Pop off the top of the lock stack:
3403          */
3404         depth = curr->lockdep_depth - 1;
3405         hlock = curr->held_locks + depth;
3406
3407         /*
3408          * Is the unlock non-nested:
3409          */
3410         if (hlock->instance != lock || hlock->references)
3411                 return lock_release_non_nested(curr, lock, ip);
3412         curr->lockdep_depth--;
3413
3414         /*
3415          * No more locks, but somehow we've got hash left over, who left it?
3416          */
3417         if (DEBUG_LOCKS_WARN_ON(!depth && (hlock->prev_chain_key != 0)))
3418                 return 0;
3419
3420         curr->curr_chain_key = hlock->prev_chain_key;
3421
3422         lock_release_holdtime(hlock);
3423
3424 #ifdef CONFIG_DEBUG_LOCKDEP
3425         hlock->prev_chain_key = 0;
3426         hlock->class_idx = 0;
3427         hlock->acquire_ip = 0;
3428         hlock->irq_context = 0;
3429 #endif
3430         return 1;
3431 }
3432
3433 /*
3434  * Remove the lock to the list of currently held locks - this gets
3435  * called on mutex_unlock()/spin_unlock*() (or on a failed
3436  * mutex_lock_interruptible()). This is done for unlocks that nest
3437  * perfectly. (i.e. the current top of the lock-stack is unlocked)
3438  */
3439 static void
3440 __lock_release(struct lockdep_map *lock, int nested, unsigned long ip)
3441 {
3442         struct task_struct *curr = current;
3443
3444         if (!check_unlock(curr, lock, ip))
3445                 return;
3446
3447         if (nested) {
3448                 if (!lock_release_nested(curr, lock, ip))
3449                         return;
3450         } else {
3451                 if (!lock_release_non_nested(curr, lock, ip))
3452                         return;
3453         }
3454
3455         check_chain_key(curr);
3456 }
3457
3458 static int __lock_is_held(struct lockdep_map *lock)
3459 {
3460         struct task_struct *curr = current;
3461         int i;
3462
3463         for (i = 0; i < curr->lockdep_depth; i++) {
3464                 struct held_lock *hlock = curr->held_locks + i;
3465
3466                 if (match_held_lock(hlock, lock))
3467                         return 1;
3468         }
3469
3470         return 0;
3471 }
3472
3473 /*
3474  * Check whether we follow the irq-flags state precisely:
3475  */
3476 static void check_flags(unsigned long flags)
3477 {
3478 #if defined(CONFIG_PROVE_LOCKING) && defined(CONFIG_DEBUG_LOCKDEP) && \
3479     defined(CONFIG_TRACE_IRQFLAGS)
3480         if (!debug_locks)
3481                 return;
3482
3483         if (irqs_disabled_flags(flags)) {
3484                 if (DEBUG_LOCKS_WARN_ON(current->hardirqs_enabled)) {
3485                         printk("possible reason: unannotated irqs-off.\n");
3486                 }
3487         } else {
3488                 if (DEBUG_LOCKS_WARN_ON(!current->hardirqs_enabled)) {
3489                         printk("possible reason: unannotated irqs-on.\n");
3490                 }
3491         }
3492
3493         /*
3494          * We dont accurately track softirq state in e.g.
3495          * hardirq contexts (such as on 4KSTACKS), so only
3496          * check if not in hardirq contexts:
3497          */
3498         if (!hardirq_count()) {
3499                 if (softirq_count()) {
3500                         /* like the above, but with softirqs */
3501                         DEBUG_LOCKS_WARN_ON(current->softirqs_enabled);
3502                 } else {
3503                         /* lick the above, does it taste good? */
3504                         DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled);
3505                 }
3506         }
3507
3508         if (!debug_locks)
3509                 print_irqtrace_events(current);
3510 #endif
3511 }
3512
3513 void lock_set_class(struct lockdep_map *lock, const char *name,
3514                     struct lock_class_key *key, unsigned int subclass,
3515                     unsigned long ip)
3516 {
3517         unsigned long flags;
3518
3519         if (unlikely(current->lockdep_recursion))
3520                 return;
3521
3522         raw_local_irq_save(flags);
3523         current->lockdep_recursion = 1;
3524         check_flags(flags);
3525         if (__lock_set_class(lock, name, key, subclass, ip))
3526                 check_chain_key(current);
3527         current->lockdep_recursion = 0;
3528         raw_local_irq_restore(flags);
3529 }
3530 EXPORT_SYMBOL_GPL(lock_set_class);
3531
3532 /*
3533  * We are not always called with irqs disabled - do that here,
3534  * and also avoid lockdep recursion:
3535  */
3536 void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
3537                           int trylock, int read, int check,
3538                           struct lockdep_map *nest_lock, unsigned long ip)
3539 {
3540         unsigned long flags;
3541
3542         if (unlikely(current->lockdep_recursion))
3543                 return;
3544
3545         raw_local_irq_save(flags);
3546         check_flags(flags);
3547
3548         current->lockdep_recursion = 1;
3549         trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip);
3550         __lock_acquire(lock, subclass, trylock, read, check,
3551                        irqs_disabled_flags(flags), nest_lock, ip, 0);
3552         current->lockdep_recursion = 0;
3553         raw_local_irq_restore(flags);
3554 }
3555 EXPORT_SYMBOL_GPL(lock_acquire);
3556
3557 void lock_release(struct lockdep_map *lock, int nested,
3558                           unsigned long ip)
3559 {
3560         unsigned long flags;
3561
3562         if (unlikely(current->lockdep_recursion))
3563                 return;
3564
3565         raw_local_irq_save(flags);
3566         check_flags(flags);
3567         current->lockdep_recursion = 1;
3568         trace_lock_release(lock, ip);
3569         __lock_release(lock, nested, ip);
3570         current->lockdep_recursion = 0;
3571         raw_local_irq_restore(flags);
3572 }
3573 EXPORT_SYMBOL_GPL(lock_release);
3574
3575 int lock_is_held(struct lockdep_map *lock)
3576 {
3577         unsigned long flags;
3578         int ret = 0;
3579
3580         if (unlikely(current->lockdep_recursion))
3581                 return 1; /* avoid false negative lockdep_assert_held() */
3582
3583         raw_local_irq_save(flags);
3584         check_flags(flags);
3585
3586         current->lockdep_recursion = 1;
3587         ret = __lock_is_held(lock);
3588         current->lockdep_recursion = 0;
3589         raw_local_irq_restore(flags);
3590
3591         return ret;
3592 }
3593 EXPORT_SYMBOL_GPL(lock_is_held);
3594
3595 void lockdep_set_current_reclaim_state(gfp_t gfp_mask)
3596 {
3597         current->lockdep_reclaim_gfp = gfp_mask;
3598 }
3599
3600 void lockdep_clear_current_reclaim_state(void)
3601 {
3602         current->lockdep_reclaim_gfp = 0;
3603 }
3604
3605 #ifdef CONFIG_LOCK_STAT
3606 static int
3607 print_lock_contention_bug(struct task_struct *curr, struct lockdep_map *lock,
3608                            unsigned long ip)
3609 {
3610         if (!debug_locks_off())
3611                 return 0;
3612         if (debug_locks_silent)
3613                 return 0;
3614
3615         printk("\n");
3616         printk("=================================\n");
3617         printk("[ BUG: bad contention detected! ]\n");
3618         printk("---------------------------------\n");
3619         printk("%s/%d is trying to contend lock (",
3620                 curr->comm, task_pid_nr(curr));
3621         print_lockdep_cache(lock);
3622         printk(") at:\n");
3623         print_ip_sym(ip);
3624         printk("but there are no locks held!\n");
3625         printk("\nother info that might help us debug this:\n");
3626         lockdep_print_held_locks(curr);
3627
3628         printk("\nstack backtrace:\n");
3629         dump_stack();
3630
3631         return 0;
3632 }
3633
3634 static void
3635 __lock_contended(struct lockdep_map *lock, unsigned long ip)
3636 {
3637         struct task_struct *curr = current;
3638         struct held_lock *hlock, *prev_hlock;
3639         struct lock_class_stats *stats;
3640         unsigned int depth;
3641         int i, contention_point, contending_point;
3642
3643         depth = curr->lockdep_depth;
3644         /*
3645          * Whee, we contended on this lock, except it seems we're not
3646          * actually trying to acquire anything much at all..
3647          */
3648         if (DEBUG_LOCKS_WARN_ON(!depth))
3649                 return;
3650
3651         prev_hlock = NULL;
3652         for (i = depth-1; i >= 0; i--) {
3653                 hlock = curr->held_locks + i;
3654                 /*
3655                  * We must not cross into another context:
3656                  */
3657                 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3658                         break;
3659                 if (match_held_lock(hlock, lock))
3660                         goto found_it;
3661                 prev_hlock = hlock;
3662         }
3663         print_lock_contention_bug(curr, lock, ip);
3664         return;
3665
3666 found_it:
3667         if (hlock->instance != lock)
3668                 return;
3669
3670         hlock->waittime_stamp = lockstat_clock();
3671
3672         contention_point = lock_point(hlock_class(hlock)->contention_point, ip);
3673         contending_point = lock_point(hlock_class(hlock)->contending_point,
3674                                       lock->ip);
3675
3676         stats = get_lock_stats(hlock_class(hlock));
3677         if (contention_point < LOCKSTAT_POINTS)
3678                 stats->contention_point[contention_point]++;
3679         if (contending_point < LOCKSTAT_POINTS)
3680                 stats->contending_point[contending_point]++;
3681         if (lock->cpu != smp_processor_id())
3682                 stats->bounces[bounce_contended + !!hlock->read]++;
3683         put_lock_stats(stats);
3684 }
3685
3686 static void
3687 __lock_acquired(struct lockdep_map *lock, unsigned long ip)
3688 {
3689         struct task_struct *curr = current;
3690         struct held_lock *hlock, *prev_hlock;
3691         struct lock_class_stats *stats;
3692         unsigned int depth;
3693         u64 now, waittime = 0;
3694         int i, cpu;
3695
3696         depth = curr->lockdep_depth;
3697         /*
3698          * Yay, we acquired ownership of this lock we didn't try to
3699          * acquire, how the heck did that happen?
3700          */
3701         if (DEBUG_LOCKS_WARN_ON(!depth))
3702                 return;
3703
3704         prev_hlock = NULL;
3705         for (i = depth-1; i >= 0; i--) {
3706                 hlock = curr->held_locks + i;
3707                 /*
3708                  * We must not cross into another context:
3709                  */
3710                 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3711                         break;
3712                 if (match_held_lock(hlock, lock))
3713                         goto found_it;
3714                 prev_hlock = hlock;
3715         }
3716         print_lock_contention_bug(curr, lock, _RET_IP_);
3717         return;
3718
3719 found_it:
3720         if (hlock->instance != lock)
3721                 return;
3722
3723         cpu = smp_processor_id();
3724         if (hlock->waittime_stamp) {
3725                 now = lockstat_clock();
3726                 waittime = now - hlock->waittime_stamp;
3727                 hlock->holdtime_stamp = now;
3728         }
3729
3730         trace_lock_acquired(lock, ip);
3731
3732         stats = get_lock_stats(hlock_class(hlock));
3733         if (waittime) {
3734                 if (hlock->read)
3735                         lock_time_inc(&stats->read_waittime, waittime);
3736                 else
3737                         lock_time_inc(&stats->write_waittime, waittime);
3738         }
3739         if (lock->cpu != cpu)
3740                 stats->bounces[bounce_acquired + !!hlock->read]++;
3741         put_lock_stats(stats);
3742
3743         lock->cpu = cpu;
3744         lock->ip = ip;
3745 }
3746
3747 void lock_contended(struct lockdep_map *lock, unsigned long ip)
3748 {
3749         unsigned long flags;
3750
3751         if (unlikely(!lock_stat))
3752                 return;
3753
3754         if (unlikely(current->lockdep_recursion))
3755                 return;
3756
3757         raw_local_irq_save(flags);
3758         check_flags(flags);
3759         current->lockdep_recursion = 1;
3760         trace_lock_contended(lock, ip);
3761         __lock_contended(lock, ip);
3762         current->lockdep_recursion = 0;
3763         raw_local_irq_restore(flags);
3764 }
3765 EXPORT_SYMBOL_GPL(lock_contended);
3766
3767 void lock_acquired(struct lockdep_map *lock, unsigned long ip)
3768 {
3769         unsigned long flags;
3770
3771         if (unlikely(!lock_stat))
3772                 return;
3773
3774         if (unlikely(current->lockdep_recursion))
3775                 return;
3776
3777         raw_local_irq_save(flags);
3778         check_flags(flags);
3779         current->lockdep_recursion = 1;
3780         __lock_acquired(lock, ip);
3781         current->lockdep_recursion = 0;
3782         raw_local_irq_restore(flags);
3783 }
3784 EXPORT_SYMBOL_GPL(lock_acquired);
3785 #endif
3786
3787 /*
3788  * Used by the testsuite, sanitize the validator state
3789  * after a simulated failure:
3790  */
3791
3792 void lockdep_reset(void)
3793 {
3794         unsigned long flags;
3795         int i;
3796
3797         raw_local_irq_save(flags);
3798         current->curr_chain_key = 0;
3799         current->lockdep_depth = 0;
3800         current->lockdep_recursion = 0;
3801         memset(current->held_locks, 0, MAX_LOCK_DEPTH*sizeof(struct held_lock));
3802         nr_hardirq_chains = 0;
3803         nr_softirq_chains = 0;
3804         nr_process_chains = 0;
3805         debug_locks = 1;
3806         for (i = 0; i < CHAINHASH_SIZE; i++)
3807                 INIT_LIST_HEAD(chainhash_table + i);
3808         raw_local_irq_restore(flags);
3809 }
3810
3811 static void zap_class(struct lock_class *class)
3812 {
3813         int i;
3814
3815         /*
3816          * Remove all dependencies this lock is
3817          * involved in:
3818          */
3819         for (i = 0; i < nr_list_entries; i++) {
3820                 if (list_entries[i].class == class)
3821                         list_del_rcu(&list_entries[i].entry);
3822         }
3823         /*
3824          * Unhash the class and remove it from the all_lock_classes list:
3825          */
3826         list_del_rcu(&class->hash_entry);
3827         list_del_rcu(&class->lock_entry);
3828
3829         class->key = NULL;
3830 }
3831
3832 static inline int within(const void *addr, void *start, unsigned long size)
3833 {
3834         return addr >= start && addr < start + size;
3835 }
3836
3837 void lockdep_free_key_range(void *start, unsigned long size)
3838 {
3839         struct lock_class *class, *next;
3840         struct list_head *head;
3841         unsigned long flags;
3842         int i;
3843         int locked;
3844
3845         raw_local_irq_save(flags);
3846         locked = graph_lock();
3847
3848         /*
3849          * Unhash all classes that were created by this module:
3850          */
3851         for (i = 0; i < CLASSHASH_SIZE; i++) {
3852                 head = classhash_table + i;
3853                 if (list_empty(head))
3854                         continue;
3855                 list_for_each_entry_safe(class, next, head, hash_entry) {
3856                         if (within(class->key, start, size))
3857                                 zap_class(class);
3858                         else if (within(class->name, start, size))
3859                                 zap_class(class);
3860                 }
3861         }
3862
3863         if (locked)
3864                 graph_unlock();
3865         raw_local_irq_restore(flags);
3866 }
3867
3868 void lockdep_reset_lock(struct lockdep_map *lock)
3869 {
3870         struct lock_class *class, *next;
3871         struct list_head *head;
3872         unsigned long flags;
3873         int i, j;
3874         int locked;
3875
3876         raw_local_irq_save(flags);
3877
3878         /*
3879          * Remove all classes this lock might have:
3880          */
3881         for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) {
3882                 /*
3883                  * If the class exists we look it up and zap it:
3884                  */
3885                 class = look_up_lock_class(lock, j);
3886                 if (class)
3887                         zap_class(class);
3888         }
3889         /*
3890          * Debug check: in the end all mapped classes should
3891          * be gone.
3892          */
3893         locked = graph_lock();
3894         for (i = 0; i < CLASSHASH_SIZE; i++) {
3895                 head = classhash_table + i;
3896                 if (list_empty(head))
3897                         continue;
3898                 list_for_each_entry_safe(class, next, head, hash_entry) {
3899                         int match = 0;
3900
3901                         for (j = 0; j < NR_LOCKDEP_CACHING_CLASSES; j++)
3902                                 match |= class == lock->class_cache[j];
3903
3904                         if (unlikely(match)) {
3905                                 if (debug_locks_off_graph_unlock()) {
3906                                         /*
3907                                          * We all just reset everything, how did it match?
3908                                          */
3909                                         WARN_ON(1);
3910                                 }
3911                                 goto out_restore;
3912                         }
3913                 }
3914         }
3915         if (locked)
3916                 graph_unlock();
3917
3918 out_restore:
3919         raw_local_irq_restore(flags);
3920 }
3921
3922 void lockdep_init(void)
3923 {
3924         int i;
3925
3926         /*
3927          * Some architectures have their own start_kernel()
3928          * code which calls lockdep_init(), while we also
3929          * call lockdep_init() from the start_kernel() itself,
3930          * and we want to initialize the hashes only once:
3931          */
3932         if (lockdep_initialized)
3933                 return;
3934
3935         for (i = 0; i < CLASSHASH_SIZE; i++)
3936                 INIT_LIST_HEAD(classhash_table + i);
3937
3938         for (i = 0; i < CHAINHASH_SIZE; i++)
3939                 INIT_LIST_HEAD(chainhash_table + i);
3940
3941         lockdep_initialized = 1;
3942 }
3943
3944 void __init lockdep_info(void)
3945 {
3946         printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");
3947
3948         printk("... MAX_LOCKDEP_SUBCLASSES:  %lu\n", MAX_LOCKDEP_SUBCLASSES);
3949         printk("... MAX_LOCK_DEPTH:          %lu\n", MAX_LOCK_DEPTH);
3950         printk("... MAX_LOCKDEP_KEYS:        %lu\n", MAX_LOCKDEP_KEYS);
3951         printk("... CLASSHASH_SIZE:          %lu\n", CLASSHASH_SIZE);
3952         printk("... MAX_LOCKDEP_ENTRIES:     %lu\n", MAX_LOCKDEP_ENTRIES);
3953         printk("... MAX_LOCKDEP_CHAINS:      %lu\n", MAX_LOCKDEP_CHAINS);
3954         printk("... CHAINHASH_SIZE:          %lu\n", CHAINHASH_SIZE);
3955
3956         printk(" memory used by lock dependency info: %lu kB\n",
3957                 (sizeof(struct lock_class) * MAX_LOCKDEP_KEYS +
3958                 sizeof(struct list_head) * CLASSHASH_SIZE +
3959                 sizeof(struct lock_list) * MAX_LOCKDEP_ENTRIES +
3960                 sizeof(struct lock_chain) * MAX_LOCKDEP_CHAINS +
3961                 sizeof(struct list_head) * CHAINHASH_SIZE
3962 #ifdef CONFIG_PROVE_LOCKING
3963                 + sizeof(struct circular_queue)
3964 #endif
3965                 ) / 1024
3966                 );
3967
3968         printk(" per task-struct memory footprint: %lu bytes\n",
3969                 sizeof(struct held_lock) * MAX_LOCK_DEPTH);
3970
3971 #ifdef CONFIG_DEBUG_LOCKDEP
3972         if (lockdep_init_error) {
3973                 printk("WARNING: lockdep init error! Arch code didn't call lockdep_init() early enough?\n");
3974                 printk("Call stack leading to lockdep invocation was:\n");
3975                 print_stack_trace(&lockdep_init_trace, 0);
3976         }
3977 #endif
3978 }
3979
3980 static void
3981 print_freed_lock_bug(struct task_struct *curr, const void *mem_from,
3982                      const void *mem_to, struct held_lock *hlock)
3983 {
3984         if (!debug_locks_off())
3985                 return;
3986         if (debug_locks_silent)
3987                 return;
3988
3989         printk("\n");
3990         printk("=========================\n");
3991         printk("[ BUG: held lock freed! ]\n");
3992         printk("-------------------------\n");
3993         printk("%s/%d is freeing memory %p-%p, with a lock still held there!\n",
3994                 curr->comm, task_pid_nr(curr), mem_from, mem_to-1);
3995         print_lock(hlock);
3996         lockdep_print_held_locks(curr);
3997
3998         printk("\nstack backtrace:\n");
3999         dump_stack();
4000 }
4001
4002 static inline int not_in_range(const void* mem_from, unsigned long mem_len,
4003                                 const void* lock_from, unsigned long lock_len)
4004 {
4005         return lock_from + lock_len <= mem_from ||
4006                 mem_from + mem_len <= lock_from;
4007 }
4008
4009 /*
4010  * Called when kernel memory is freed (or unmapped), or if a lock
4011  * is destroyed or reinitialized - this code checks whether there is
4012  * any held lock in the memory range of <from> to <to>:
4013  */
4014 void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len)
4015 {
4016         struct task_struct *curr = current;
4017         struct held_lock *hlock;
4018         unsigned long flags;
4019         int i;
4020
4021         if (unlikely(!debug_locks))
4022                 return;
4023
4024         local_irq_save(flags);
4025         for (i = 0; i < curr->lockdep_depth; i++) {
4026                 hlock = curr->held_locks + i;
4027
4028                 if (not_in_range(mem_from, mem_len, hlock->instance,
4029                                         sizeof(*hlock->instance)))
4030                         continue;
4031
4032                 print_freed_lock_bug(curr, mem_from, mem_from + mem_len, hlock);
4033                 break;
4034         }
4035         local_irq_restore(flags);
4036 }
4037 EXPORT_SYMBOL_GPL(debug_check_no_locks_freed);
4038
4039 static void print_held_locks_bug(struct task_struct *curr)
4040 {
4041         if (!debug_locks_off())
4042                 return;
4043         if (debug_locks_silent)
4044                 return;
4045
4046         printk("\n");
4047         printk("=====================================\n");
4048         printk("[ BUG: lock held at task exit time! ]\n");
4049         printk("-------------------------------------\n");
4050         printk("%s/%d is exiting with locks still held!\n",
4051                 curr->comm, task_pid_nr(curr));
4052         lockdep_print_held_locks(curr);
4053
4054         printk("\nstack backtrace:\n");
4055         dump_stack();
4056 }
4057
4058 void debug_check_no_locks_held(struct task_struct *task)
4059 {
4060         if (unlikely(task->lockdep_depth > 0))
4061                 print_held_locks_bug(task);
4062 }
4063
4064 void debug_show_all_locks(void)
4065 {
4066         struct task_struct *g, *p;
4067         int count = 10;
4068         int unlock = 1;
4069
4070         if (unlikely(!debug_locks)) {
4071                 printk("INFO: lockdep is turned off.\n");
4072                 return;
4073         }
4074         printk("\nShowing all locks held in the system:\n");
4075
4076         /*
4077          * Here we try to get the tasklist_lock as hard as possible,
4078          * if not successful after 2 seconds we ignore it (but keep
4079          * trying). This is to enable a debug printout even if a
4080          * tasklist_lock-holding task deadlocks or crashes.
4081          */
4082 retry:
4083         if (!read_trylock(&tasklist_lock)) {
4084                 if (count == 10)
4085                         printk("hm, tasklist_lock locked, retrying... ");
4086                 if (count) {
4087                         count--;
4088                         printk(" #%d", 10-count);
4089                         mdelay(200);
4090                         goto retry;
4091                 }
4092                 printk(" ignoring it.\n");
4093                 unlock = 0;
4094         } else {
4095                 if (count != 10)
4096                         printk(KERN_CONT " locked it.\n");
4097         }
4098
4099         do_each_thread(g, p) {
4100                 /*
4101                  * It's not reliable to print a task's held locks
4102                  * if it's not sleeping (or if it's not the current
4103                  * task):
4104                  */
4105                 if (p->state == TASK_RUNNING && p != current)
4106                         continue;
4107                 if (p->lockdep_depth)
4108                         lockdep_print_held_locks(p);
4109                 if (!unlock)
4110                         if (read_trylock(&tasklist_lock))
4111                                 unlock = 1;
4112         } while_each_thread(g, p);
4113
4114         printk("\n");
4115         printk("=============================================\n\n");
4116
4117         if (unlock)
4118                 read_unlock(&tasklist_lock);
4119 }
4120 EXPORT_SYMBOL_GPL(debug_show_all_locks);
4121
4122 /*
4123  * Careful: only use this function if you are sure that
4124  * the task cannot run in parallel!
4125  */
4126 void debug_show_held_locks(struct task_struct *task)
4127 {
4128         if (unlikely(!debug_locks)) {
4129                 printk("INFO: lockdep is turned off.\n");
4130                 return;
4131         }
4132         lockdep_print_held_locks(task);
4133 }
4134 EXPORT_SYMBOL_GPL(debug_show_held_locks);
4135
4136 void lockdep_sys_exit(void)
4137 {
4138         struct task_struct *curr = current;
4139
4140         if (unlikely(curr->lockdep_depth)) {
4141                 if (!debug_locks_off())
4142                         return;
4143                 printk("\n");
4144                 printk("================================================\n");
4145                 printk("[ BUG: lock held when returning to user space! ]\n");
4146                 printk("------------------------------------------------\n");
4147                 printk("%s/%d is leaving the kernel with locks still held!\n",
4148                                 curr->comm, curr->pid);
4149                 lockdep_print_held_locks(curr);
4150         }
4151 }
4152
4153 void lockdep_rcu_suspicious(const char *file, const int line, const char *s)
4154 {
4155         struct task_struct *curr = current;
4156
4157 #ifndef CONFIG_PROVE_RCU_REPEATEDLY
4158         if (!debug_locks_off())
4159                 return;
4160 #endif /* #ifdef CONFIG_PROVE_RCU_REPEATEDLY */
4161         /* Note: the following can be executed concurrently, so be careful. */
4162         printk("\n");
4163         printk("===============================\n");
4164         printk("[ INFO: suspicious RCU usage. ]\n");
4165         printk("-------------------------------\n");
4166         printk("%s:%d %s!\n", file, line, s);
4167         printk("\nother info that might help us debug this:\n\n");
4168         printk("\nrcu_scheduler_active = %d, debug_locks = %d\n", rcu_scheduler_active, debug_locks);
4169         lockdep_print_held_locks(curr);
4170         printk("\nstack backtrace:\n");
4171         dump_stack();
4172 }
4173 EXPORT_SYMBOL_GPL(lockdep_rcu_suspicious);