lockdep: Print the shortest dependency chain if finding a circle
[linux-2.6.git] / kernel / lockdep.c
1 /*
2  * kernel/lockdep.c
3  *
4  * Runtime locking correctness validator
5  *
6  * Started by Ingo Molnar:
7  *
8  *  Copyright (C) 2006,2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
9  *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
10  *
11  * this code maps all the lock dependencies as they occur in a live kernel
12  * and will warn about the following classes of locking bugs:
13  *
14  * - lock inversion scenarios
15  * - circular lock dependencies
16  * - hardirq/softirq safe/unsafe locking bugs
17  *
18  * Bugs are reported even if the current locking scenario does not cause
19  * any deadlock at this point.
20  *
21  * I.e. if anytime in the past two locks were taken in a different order,
22  * even if it happened for another task, even if those were different
23  * locks (but of the same class as this lock), this code will detect it.
24  *
25  * Thanks to Arjan van de Ven for coming up with the initial idea of
26  * mapping lock dependencies runtime.
27  */
28 #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
46 #include <asm/sections.h>
47
48 #include "lockdep_internals.h"
49
50 #define CREATE_TRACE_POINTS
51 #include <trace/events/lockdep.h>
52
53 #ifdef CONFIG_PROVE_LOCKING
54 int prove_locking = 1;
55 module_param(prove_locking, int, 0644);
56 #else
57 #define prove_locking 0
58 #endif
59
60 #ifdef CONFIG_LOCK_STAT
61 int lock_stat = 1;
62 module_param(lock_stat, int, 0644);
63 #else
64 #define lock_stat 0
65 #endif
66
67 /*
68  * lockdep_lock: protects the lockdep graph, the hashes and the
69  *               class/list/hash allocators.
70  *
71  * This is one of the rare exceptions where it's justified
72  * to use a raw spinlock - we really dont want the spinlock
73  * code to recurse back into the lockdep code...
74  */
75 static raw_spinlock_t lockdep_lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
76
77 static int graph_lock(void)
78 {
79         __raw_spin_lock(&lockdep_lock);
80         /*
81          * Make sure that if another CPU detected a bug while
82          * walking the graph we dont change it (while the other
83          * CPU is busy printing out stuff with the graph lock
84          * dropped already)
85          */
86         if (!debug_locks) {
87                 __raw_spin_unlock(&lockdep_lock);
88                 return 0;
89         }
90         /* prevent any recursions within lockdep from causing deadlocks */
91         current->lockdep_recursion++;
92         return 1;
93 }
94
95 static inline int graph_unlock(void)
96 {
97         if (debug_locks && !__raw_spin_is_locked(&lockdep_lock))
98                 return DEBUG_LOCKS_WARN_ON(1);
99
100         current->lockdep_recursion--;
101         __raw_spin_unlock(&lockdep_lock);
102         return 0;
103 }
104
105 /*
106  * Turn lock debugging off and return with 0 if it was off already,
107  * and also release the graph lock:
108  */
109 static inline int debug_locks_off_graph_unlock(void)
110 {
111         int ret = debug_locks_off();
112
113         __raw_spin_unlock(&lockdep_lock);
114
115         return ret;
116 }
117
118 static int lockdep_initialized;
119
120 unsigned long nr_list_entries;
121 static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES];
122
123 /*
124  * All data structures here are protected by the global debug_lock.
125  *
126  * Mutex key structs only get allocated, once during bootup, and never
127  * get freed - this significantly simplifies the debugging code.
128  */
129 unsigned long nr_lock_classes;
130 static struct lock_class lock_classes[MAX_LOCKDEP_KEYS];
131
132 static inline struct lock_class *hlock_class(struct held_lock *hlock)
133 {
134         if (!hlock->class_idx) {
135                 DEBUG_LOCKS_WARN_ON(1);
136                 return NULL;
137         }
138         return lock_classes + hlock->class_idx - 1;
139 }
140
141 #ifdef CONFIG_LOCK_STAT
142 static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS], lock_stats);
143
144 static int lock_point(unsigned long points[], unsigned long ip)
145 {
146         int i;
147
148         for (i = 0; i < LOCKSTAT_POINTS; i++) {
149                 if (points[i] == 0) {
150                         points[i] = ip;
151                         break;
152                 }
153                 if (points[i] == ip)
154                         break;
155         }
156
157         return i;
158 }
159
160 static void lock_time_inc(struct lock_time *lt, s64 time)
161 {
162         if (time > lt->max)
163                 lt->max = time;
164
165         if (time < lt->min || !lt->min)
166                 lt->min = time;
167
168         lt->total += time;
169         lt->nr++;
170 }
171
172 static inline void lock_time_add(struct lock_time *src, struct lock_time *dst)
173 {
174         dst->min += src->min;
175         dst->max += src->max;
176         dst->total += src->total;
177         dst->nr += src->nr;
178 }
179
180 struct lock_class_stats lock_stats(struct lock_class *class)
181 {
182         struct lock_class_stats stats;
183         int cpu, i;
184
185         memset(&stats, 0, sizeof(struct lock_class_stats));
186         for_each_possible_cpu(cpu) {
187                 struct lock_class_stats *pcs =
188                         &per_cpu(lock_stats, cpu)[class - lock_classes];
189
190                 for (i = 0; i < ARRAY_SIZE(stats.contention_point); i++)
191                         stats.contention_point[i] += pcs->contention_point[i];
192
193                 for (i = 0; i < ARRAY_SIZE(stats.contending_point); i++)
194                         stats.contending_point[i] += pcs->contending_point[i];
195
196                 lock_time_add(&pcs->read_waittime, &stats.read_waittime);
197                 lock_time_add(&pcs->write_waittime, &stats.write_waittime);
198
199                 lock_time_add(&pcs->read_holdtime, &stats.read_holdtime);
200                 lock_time_add(&pcs->write_holdtime, &stats.write_holdtime);
201
202                 for (i = 0; i < ARRAY_SIZE(stats.bounces); i++)
203                         stats.bounces[i] += pcs->bounces[i];
204         }
205
206         return stats;
207 }
208
209 void clear_lock_stats(struct lock_class *class)
210 {
211         int cpu;
212
213         for_each_possible_cpu(cpu) {
214                 struct lock_class_stats *cpu_stats =
215                         &per_cpu(lock_stats, cpu)[class - lock_classes];
216
217                 memset(cpu_stats, 0, sizeof(struct lock_class_stats));
218         }
219         memset(class->contention_point, 0, sizeof(class->contention_point));
220         memset(class->contending_point, 0, sizeof(class->contending_point));
221 }
222
223 static struct lock_class_stats *get_lock_stats(struct lock_class *class)
224 {
225         return &get_cpu_var(lock_stats)[class - lock_classes];
226 }
227
228 static void put_lock_stats(struct lock_class_stats *stats)
229 {
230         put_cpu_var(lock_stats);
231 }
232
233 static void lock_release_holdtime(struct held_lock *hlock)
234 {
235         struct lock_class_stats *stats;
236         s64 holdtime;
237
238         if (!lock_stat)
239                 return;
240
241         holdtime = sched_clock() - hlock->holdtime_stamp;
242
243         stats = get_lock_stats(hlock_class(hlock));
244         if (hlock->read)
245                 lock_time_inc(&stats->read_holdtime, holdtime);
246         else
247                 lock_time_inc(&stats->write_holdtime, holdtime);
248         put_lock_stats(stats);
249 }
250 #else
251 static inline void lock_release_holdtime(struct held_lock *hlock)
252 {
253 }
254 #endif
255
256 /*
257  * We keep a global list of all lock classes. The list only grows,
258  * never shrinks. The list is only accessed with the lockdep
259  * spinlock lock held.
260  */
261 LIST_HEAD(all_lock_classes);
262
263 /*
264  * The lockdep classes are in a hash-table as well, for fast lookup:
265  */
266 #define CLASSHASH_BITS          (MAX_LOCKDEP_KEYS_BITS - 1)
267 #define CLASSHASH_SIZE          (1UL << CLASSHASH_BITS)
268 #define __classhashfn(key)      hash_long((unsigned long)key, CLASSHASH_BITS)
269 #define classhashentry(key)     (classhash_table + __classhashfn((key)))
270
271 static struct list_head classhash_table[CLASSHASH_SIZE];
272
273 /*
274  * We put the lock dependency chains into a hash-table as well, to cache
275  * their existence:
276  */
277 #define CHAINHASH_BITS          (MAX_LOCKDEP_CHAINS_BITS-1)
278 #define CHAINHASH_SIZE          (1UL << CHAINHASH_BITS)
279 #define __chainhashfn(chain)    hash_long(chain, CHAINHASH_BITS)
280 #define chainhashentry(chain)   (chainhash_table + __chainhashfn((chain)))
281
282 static struct list_head chainhash_table[CHAINHASH_SIZE];
283
284 /*
285  * The hash key of the lock dependency chains is a hash itself too:
286  * it's a hash of all locks taken up to that lock, including that lock.
287  * It's a 64-bit hash, because it's important for the keys to be
288  * unique.
289  */
290 #define iterate_chain_key(key1, key2) \
291         (((key1) << MAX_LOCKDEP_KEYS_BITS) ^ \
292         ((key1) >> (64-MAX_LOCKDEP_KEYS_BITS)) ^ \
293         (key2))
294
295 void lockdep_off(void)
296 {
297         current->lockdep_recursion++;
298 }
299 EXPORT_SYMBOL(lockdep_off);
300
301 void lockdep_on(void)
302 {
303         current->lockdep_recursion--;
304 }
305 EXPORT_SYMBOL(lockdep_on);
306
307 /*
308  * Debugging switches:
309  */
310
311 #define VERBOSE                 0
312 #define VERY_VERBOSE            0
313
314 #if VERBOSE
315 # define HARDIRQ_VERBOSE        1
316 # define SOFTIRQ_VERBOSE        1
317 # define RECLAIM_VERBOSE        1
318 #else
319 # define HARDIRQ_VERBOSE        0
320 # define SOFTIRQ_VERBOSE        0
321 # define RECLAIM_VERBOSE        0
322 #endif
323
324 #if VERBOSE || HARDIRQ_VERBOSE || SOFTIRQ_VERBOSE || RECLAIM_VERBOSE
325 /*
326  * Quick filtering for interesting events:
327  */
328 static int class_filter(struct lock_class *class)
329 {
330 #if 0
331         /* Example */
332         if (class->name_version == 1 &&
333                         !strcmp(class->name, "lockname"))
334                 return 1;
335         if (class->name_version == 1 &&
336                         !strcmp(class->name, "&struct->lockfield"))
337                 return 1;
338 #endif
339         /* Filter everything else. 1 would be to allow everything else */
340         return 0;
341 }
342 #endif
343
344 static int verbose(struct lock_class *class)
345 {
346 #if VERBOSE
347         return class_filter(class);
348 #endif
349         return 0;
350 }
351
352 /*
353  * Stack-trace: tightly packed array of stack backtrace
354  * addresses. Protected by the graph_lock.
355  */
356 unsigned long nr_stack_trace_entries;
357 static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];
358
359 static int save_trace(struct stack_trace *trace)
360 {
361         trace->nr_entries = 0;
362         trace->max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries;
363         trace->entries = stack_trace + nr_stack_trace_entries;
364
365         trace->skip = 3;
366
367         save_stack_trace(trace);
368
369         trace->max_entries = trace->nr_entries;
370
371         nr_stack_trace_entries += trace->nr_entries;
372
373         if (nr_stack_trace_entries == MAX_STACK_TRACE_ENTRIES) {
374                 if (!debug_locks_off_graph_unlock())
375                         return 0;
376
377                 printk("BUG: MAX_STACK_TRACE_ENTRIES too low!\n");
378                 printk("turning off the locking correctness validator.\n");
379                 dump_stack();
380
381                 return 0;
382         }
383
384         return 1;
385 }
386
387 unsigned int nr_hardirq_chains;
388 unsigned int nr_softirq_chains;
389 unsigned int nr_process_chains;
390 unsigned int max_lockdep_depth;
391 unsigned int max_recursion_depth;
392
393 static unsigned int lockdep_dependency_gen_id;
394
395 static bool lockdep_dependency_visit(struct lock_class *source,
396                                      unsigned int depth)
397 {
398         if (!depth)
399                 lockdep_dependency_gen_id++;
400         if (source->dep_gen_id == lockdep_dependency_gen_id)
401                 return true;
402         source->dep_gen_id = lockdep_dependency_gen_id;
403         return false;
404 }
405
406 #ifdef CONFIG_DEBUG_LOCKDEP
407 /*
408  * We cannot printk in early bootup code. Not even early_printk()
409  * might work. So we mark any initialization errors and printk
410  * about it later on, in lockdep_info().
411  */
412 static int lockdep_init_error;
413 static unsigned long lockdep_init_trace_data[20];
414 static struct stack_trace lockdep_init_trace = {
415         .max_entries = ARRAY_SIZE(lockdep_init_trace_data),
416         .entries = lockdep_init_trace_data,
417 };
418
419 /*
420  * Various lockdep statistics:
421  */
422 atomic_t chain_lookup_hits;
423 atomic_t chain_lookup_misses;
424 atomic_t hardirqs_on_events;
425 atomic_t hardirqs_off_events;
426 atomic_t redundant_hardirqs_on;
427 atomic_t redundant_hardirqs_off;
428 atomic_t softirqs_on_events;
429 atomic_t softirqs_off_events;
430 atomic_t redundant_softirqs_on;
431 atomic_t redundant_softirqs_off;
432 atomic_t nr_unused_locks;
433 atomic_t nr_cyclic_checks;
434 atomic_t nr_cyclic_check_recursions;
435 atomic_t nr_find_usage_forwards_checks;
436 atomic_t nr_find_usage_forwards_recursions;
437 atomic_t nr_find_usage_backwards_checks;
438 atomic_t nr_find_usage_backwards_recursions;
439 #endif
440
441 /*
442  * Locking printouts:
443  */
444
445 #define __USAGE(__STATE)                                                \
446         [LOCK_USED_IN_##__STATE] = "IN-"__stringify(__STATE)"-W",       \
447         [LOCK_ENABLED_##__STATE] = __stringify(__STATE)"-ON-W",         \
448         [LOCK_USED_IN_##__STATE##_READ] = "IN-"__stringify(__STATE)"-R",\
449         [LOCK_ENABLED_##__STATE##_READ] = __stringify(__STATE)"-ON-R",
450
451 static const char *usage_str[] =
452 {
453 #define LOCKDEP_STATE(__STATE) __USAGE(__STATE)
454 #include "lockdep_states.h"
455 #undef LOCKDEP_STATE
456         [LOCK_USED] = "INITIAL USE",
457 };
458
459 const char * __get_key_name(struct lockdep_subclass_key *key, char *str)
460 {
461         return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str);
462 }
463
464 static inline unsigned long lock_flag(enum lock_usage_bit bit)
465 {
466         return 1UL << bit;
467 }
468
469 static char get_usage_char(struct lock_class *class, enum lock_usage_bit bit)
470 {
471         char c = '.';
472
473         if (class->usage_mask & lock_flag(bit + 2))
474                 c = '+';
475         if (class->usage_mask & lock_flag(bit)) {
476                 c = '-';
477                 if (class->usage_mask & lock_flag(bit + 2))
478                         c = '?';
479         }
480
481         return c;
482 }
483
484 void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS])
485 {
486         int i = 0;
487
488 #define LOCKDEP_STATE(__STATE)                                          \
489         usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE);     \
490         usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE##_READ);
491 #include "lockdep_states.h"
492 #undef LOCKDEP_STATE
493
494         usage[i] = '\0';
495 }
496
497 static void print_lock_name(struct lock_class *class)
498 {
499         char str[KSYM_NAME_LEN], usage[LOCK_USAGE_CHARS];
500         const char *name;
501
502         get_usage_chars(class, usage);
503
504         name = class->name;
505         if (!name) {
506                 name = __get_key_name(class->key, str);
507                 printk(" (%s", name);
508         } else {
509                 printk(" (%s", name);
510                 if (class->name_version > 1)
511                         printk("#%d", class->name_version);
512                 if (class->subclass)
513                         printk("/%d", class->subclass);
514         }
515         printk("){%s}", usage);
516 }
517
518 static void print_lockdep_cache(struct lockdep_map *lock)
519 {
520         const char *name;
521         char str[KSYM_NAME_LEN];
522
523         name = lock->name;
524         if (!name)
525                 name = __get_key_name(lock->key->subkeys, str);
526
527         printk("%s", name);
528 }
529
530 static void print_lock(struct held_lock *hlock)
531 {
532         print_lock_name(hlock_class(hlock));
533         printk(", at: ");
534         print_ip_sym(hlock->acquire_ip);
535 }
536
537 static void lockdep_print_held_locks(struct task_struct *curr)
538 {
539         int i, depth = curr->lockdep_depth;
540
541         if (!depth) {
542                 printk("no locks held by %s/%d.\n", curr->comm, task_pid_nr(curr));
543                 return;
544         }
545         printk("%d lock%s held by %s/%d:\n",
546                 depth, depth > 1 ? "s" : "", curr->comm, task_pid_nr(curr));
547
548         for (i = 0; i < depth; i++) {
549                 printk(" #%d: ", i);
550                 print_lock(curr->held_locks + i);
551         }
552 }
553
554 static void print_lock_class_header(struct lock_class *class, int depth)
555 {
556         int bit;
557
558         printk("%*s->", depth, "");
559         print_lock_name(class);
560         printk(" ops: %lu", class->ops);
561         printk(" {\n");
562
563         for (bit = 0; bit < LOCK_USAGE_STATES; bit++) {
564                 if (class->usage_mask & (1 << bit)) {
565                         int len = depth;
566
567                         len += printk("%*s   %s", depth, "", usage_str[bit]);
568                         len += printk(" at:\n");
569                         print_stack_trace(class->usage_traces + bit, len);
570                 }
571         }
572         printk("%*s }\n", depth, "");
573
574         printk("%*s ... key      at: ",depth,"");
575         print_ip_sym((unsigned long)class->key);
576 }
577
578 /*
579  * printk all lock dependencies starting at <entry>:
580  */
581 static void __used
582 print_lock_dependencies(struct lock_class *class, int depth)
583 {
584         struct lock_list *entry;
585
586         if (lockdep_dependency_visit(class, depth))
587                 return;
588
589         if (DEBUG_LOCKS_WARN_ON(depth >= 20))
590                 return;
591
592         print_lock_class_header(class, depth);
593
594         list_for_each_entry(entry, &class->locks_after, entry) {
595                 if (DEBUG_LOCKS_WARN_ON(!entry->class))
596                         return;
597
598                 print_lock_dependencies(entry->class, depth + 1);
599
600                 printk("%*s ... acquired at:\n",depth,"");
601                 print_stack_trace(&entry->trace, 2);
602                 printk("\n");
603         }
604 }
605
606 static void print_kernel_version(void)
607 {
608         printk("%s %.*s\n", init_utsname()->release,
609                 (int)strcspn(init_utsname()->version, " "),
610                 init_utsname()->version);
611 }
612
613 static int very_verbose(struct lock_class *class)
614 {
615 #if VERY_VERBOSE
616         return class_filter(class);
617 #endif
618         return 0;
619 }
620
621 /*
622  * Is this the address of a static object:
623  */
624 static int static_obj(void *obj)
625 {
626         unsigned long start = (unsigned long) &_stext,
627                       end   = (unsigned long) &_end,
628                       addr  = (unsigned long) obj;
629 #ifdef CONFIG_SMP
630         int i;
631 #endif
632
633         /*
634          * static variable?
635          */
636         if ((addr >= start) && (addr < end))
637                 return 1;
638
639 #ifdef CONFIG_SMP
640         /*
641          * percpu var?
642          */
643         for_each_possible_cpu(i) {
644                 start = (unsigned long) &__per_cpu_start + per_cpu_offset(i);
645                 end   = (unsigned long) &__per_cpu_start + PERCPU_ENOUGH_ROOM
646                                         + per_cpu_offset(i);
647
648                 if ((addr >= start) && (addr < end))
649                         return 1;
650         }
651 #endif
652
653         /*
654          * module var?
655          */
656         return is_module_address(addr);
657 }
658
659 /*
660  * To make lock name printouts unique, we calculate a unique
661  * class->name_version generation counter:
662  */
663 static int count_matching_names(struct lock_class *new_class)
664 {
665         struct lock_class *class;
666         int count = 0;
667
668         if (!new_class->name)
669                 return 0;
670
671         list_for_each_entry(class, &all_lock_classes, lock_entry) {
672                 if (new_class->key - new_class->subclass == class->key)
673                         return class->name_version;
674                 if (class->name && !strcmp(class->name, new_class->name))
675                         count = max(count, class->name_version);
676         }
677
678         return count + 1;
679 }
680
681 /*
682  * Register a lock's class in the hash-table, if the class is not present
683  * yet. Otherwise we look it up. We cache the result in the lock object
684  * itself, so actual lookup of the hash should be once per lock object.
685  */
686 static inline struct lock_class *
687 look_up_lock_class(struct lockdep_map *lock, unsigned int subclass)
688 {
689         struct lockdep_subclass_key *key;
690         struct list_head *hash_head;
691         struct lock_class *class;
692
693 #ifdef CONFIG_DEBUG_LOCKDEP
694         /*
695          * If the architecture calls into lockdep before initializing
696          * the hashes then we'll warn about it later. (we cannot printk
697          * right now)
698          */
699         if (unlikely(!lockdep_initialized)) {
700                 lockdep_init();
701                 lockdep_init_error = 1;
702                 save_stack_trace(&lockdep_init_trace);
703         }
704 #endif
705
706         /*
707          * Static locks do not have their class-keys yet - for them the key
708          * is the lock object itself:
709          */
710         if (unlikely(!lock->key))
711                 lock->key = (void *)lock;
712
713         /*
714          * NOTE: the class-key must be unique. For dynamic locks, a static
715          * lock_class_key variable is passed in through the mutex_init()
716          * (or spin_lock_init()) call - which acts as the key. For static
717          * locks we use the lock object itself as the key.
718          */
719         BUILD_BUG_ON(sizeof(struct lock_class_key) >
720                         sizeof(struct lockdep_map));
721
722         key = lock->key->subkeys + subclass;
723
724         hash_head = classhashentry(key);
725
726         /*
727          * We can walk the hash lockfree, because the hash only
728          * grows, and we are careful when adding entries to the end:
729          */
730         list_for_each_entry(class, hash_head, hash_entry) {
731                 if (class->key == key) {
732                         WARN_ON_ONCE(class->name != lock->name);
733                         return class;
734                 }
735         }
736
737         return NULL;
738 }
739
740 /*
741  * Register a lock's class in the hash-table, if the class is not present
742  * yet. Otherwise we look it up. We cache the result in the lock object
743  * itself, so actual lookup of the hash should be once per lock object.
744  */
745 static inline struct lock_class *
746 register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
747 {
748         struct lockdep_subclass_key *key;
749         struct list_head *hash_head;
750         struct lock_class *class;
751         unsigned long flags;
752
753         class = look_up_lock_class(lock, subclass);
754         if (likely(class))
755                 return class;
756
757         /*
758          * Debug-check: all keys must be persistent!
759          */
760         if (!static_obj(lock->key)) {
761                 debug_locks_off();
762                 printk("INFO: trying to register non-static key.\n");
763                 printk("the code is fine but needs lockdep annotation.\n");
764                 printk("turning off the locking correctness validator.\n");
765                 dump_stack();
766
767                 return NULL;
768         }
769
770         key = lock->key->subkeys + subclass;
771         hash_head = classhashentry(key);
772
773         raw_local_irq_save(flags);
774         if (!graph_lock()) {
775                 raw_local_irq_restore(flags);
776                 return NULL;
777         }
778         /*
779          * We have to do the hash-walk again, to avoid races
780          * with another CPU:
781          */
782         list_for_each_entry(class, hash_head, hash_entry)
783                 if (class->key == key)
784                         goto out_unlock_set;
785         /*
786          * Allocate a new key from the static array, and add it to
787          * the hash:
788          */
789         if (nr_lock_classes >= MAX_LOCKDEP_KEYS) {
790                 if (!debug_locks_off_graph_unlock()) {
791                         raw_local_irq_restore(flags);
792                         return NULL;
793                 }
794                 raw_local_irq_restore(flags);
795
796                 printk("BUG: MAX_LOCKDEP_KEYS too low!\n");
797                 printk("turning off the locking correctness validator.\n");
798                 dump_stack();
799                 return NULL;
800         }
801         class = lock_classes + nr_lock_classes++;
802         debug_atomic_inc(&nr_unused_locks);
803         class->key = key;
804         class->name = lock->name;
805         class->subclass = subclass;
806         INIT_LIST_HEAD(&class->lock_entry);
807         INIT_LIST_HEAD(&class->locks_before);
808         INIT_LIST_HEAD(&class->locks_after);
809         class->name_version = count_matching_names(class);
810         /*
811          * We use RCU's safe list-add method to make
812          * parallel walking of the hash-list safe:
813          */
814         list_add_tail_rcu(&class->hash_entry, hash_head);
815         /*
816          * Add it to the global list of classes:
817          */
818         list_add_tail_rcu(&class->lock_entry, &all_lock_classes);
819
820         if (verbose(class)) {
821                 graph_unlock();
822                 raw_local_irq_restore(flags);
823
824                 printk("\nnew class %p: %s", class->key, class->name);
825                 if (class->name_version > 1)
826                         printk("#%d", class->name_version);
827                 printk("\n");
828                 dump_stack();
829
830                 raw_local_irq_save(flags);
831                 if (!graph_lock()) {
832                         raw_local_irq_restore(flags);
833                         return NULL;
834                 }
835         }
836 out_unlock_set:
837         graph_unlock();
838         raw_local_irq_restore(flags);
839
840         if (!subclass || force)
841                 lock->class_cache = class;
842
843         if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))
844                 return NULL;
845
846         return class;
847 }
848
849 #ifdef CONFIG_PROVE_LOCKING
850 /*
851  * Allocate a lockdep entry. (assumes the graph_lock held, returns
852  * with NULL on failure)
853  */
854 static struct lock_list *alloc_list_entry(void)
855 {
856         if (nr_list_entries >= MAX_LOCKDEP_ENTRIES) {
857                 if (!debug_locks_off_graph_unlock())
858                         return NULL;
859
860                 printk("BUG: MAX_LOCKDEP_ENTRIES too low!\n");
861                 printk("turning off the locking correctness validator.\n");
862                 dump_stack();
863                 return NULL;
864         }
865         return list_entries + nr_list_entries++;
866 }
867
868 /*
869  * Add a new dependency to the head of the list:
870  */
871 static int add_lock_to_list(struct lock_class *class, struct lock_class *this,
872                             struct list_head *head, unsigned long ip, int distance)
873 {
874         struct lock_list *entry;
875         /*
876          * Lock not present yet - get a new dependency struct and
877          * add it to the list:
878          */
879         entry = alloc_list_entry();
880         if (!entry)
881                 return 0;
882
883         if (!save_trace(&entry->trace))
884                 return 0;
885
886         entry->class = this;
887         entry->distance = distance;
888         /*
889          * Since we never remove from the dependency list, the list can
890          * be walked lockless by other CPUs, it's only allocation
891          * that must be protected by the spinlock. But this also means
892          * we must make new entries visible only once writes to the
893          * entry become visible - hence the RCU op:
894          */
895         list_add_tail_rcu(&entry->entry, head);
896
897         return 1;
898 }
899
900 static struct circular_queue  lock_cq;
901 static int __search_shortest_path(struct lock_list *source_entry,
902                                 struct lock_class *target,
903                                 struct lock_list **target_entry,
904                                 int forward)
905 {
906         struct lock_list *entry;
907         struct circular_queue *cq = &lock_cq;
908         int ret = 1;
909
910         __cq_init(cq);
911
912         mark_lock_accessed(source_entry, NULL);
913         if (source_entry->class == target) {
914                 *target_entry = source_entry;
915                 ret = 0;
916                 goto exit;
917         }
918
919         __cq_enqueue(cq, (unsigned long)source_entry);
920
921         while (!__cq_empty(cq)) {
922                 struct lock_list *lock;
923                 struct list_head *head;
924
925                 __cq_dequeue(cq, (unsigned long *)&lock);
926
927                 if (!lock->class) {
928                         ret = -2;
929                         goto exit;
930                 }
931
932                 if (forward)
933                         head = &lock->class->locks_after;
934                 else
935                         head = &lock->class->locks_before;
936
937                 list_for_each_entry(entry, head, entry) {
938                         if (!lock_accessed(entry)) {
939                                 mark_lock_accessed(entry, lock);
940                                 if (entry->class == target) {
941                                         *target_entry = entry;
942                                         ret = 0;
943                                         goto exit;
944                                 }
945
946                                 if (__cq_enqueue(cq, (unsigned long)entry)) {
947                                         ret = -1;
948                                         goto exit;
949                                 }
950                         }
951                 }
952         }
953 exit:
954         return ret;
955 }
956
957 static inline int __search_forward_shortest_path(struct lock_list *src_entry,
958                                 struct lock_class *target,
959                                 struct lock_list **target_entry)
960 {
961         return __search_shortest_path(src_entry, target, target_entry, 1);
962
963 }
964
965 static inline int __search_backward_shortest_path(struct lock_list *src_entry,
966                                 struct lock_class *target,
967                                 struct lock_list **target_entry)
968 {
969         return __search_shortest_path(src_entry, target, target_entry, 0);
970
971 }
972
973 /*
974  * Recursive, forwards-direction lock-dependency checking, used for
975  * both noncyclic checking and for hardirq-unsafe/softirq-unsafe
976  * checking.
977  *
978  * (to keep the stackframe of the recursive functions small we
979  *  use these global variables, and we also mark various helper
980  *  functions as noinline.)
981  */
982 static struct held_lock *check_source, *check_target;
983
984 /*
985  * Print a dependency chain entry (this is only done when a deadlock
986  * has been detected):
987  */
988 static noinline int
989 print_circular_bug_entry(struct lock_list *target, unsigned int depth)
990 {
991         if (debug_locks_silent)
992                 return 0;
993         printk("\n-> #%u", depth);
994         print_lock_name(target->class);
995         printk(":\n");
996         print_stack_trace(&target->trace, 6);
997
998         return 0;
999 }
1000
1001 /*
1002  * When a circular dependency is detected, print the
1003  * header first:
1004  */
1005 static noinline int
1006 print_circular_bug_header(struct lock_list *entry, unsigned int depth)
1007 {
1008         struct task_struct *curr = current;
1009
1010         if (debug_locks_silent)
1011                 return 0;
1012
1013         printk("\n=======================================================\n");
1014         printk(  "[ INFO: possible circular locking dependency detected ]\n");
1015         print_kernel_version();
1016         printk(  "-------------------------------------------------------\n");
1017         printk("%s/%d is trying to acquire lock:\n",
1018                 curr->comm, task_pid_nr(curr));
1019         print_lock(check_source);
1020         printk("\nbut task is already holding lock:\n");
1021         print_lock(check_target);
1022         printk("\nwhich lock already depends on the new lock.\n\n");
1023         printk("\nthe existing dependency chain (in reverse order) is:\n");
1024
1025         print_circular_bug_entry(entry, depth);
1026
1027         return 0;
1028 }
1029
1030 static noinline int print_circular_bug(void)
1031 {
1032         struct task_struct *curr = current;
1033         struct lock_list this;
1034         struct lock_list *target;
1035         struct lock_list *parent;
1036         int result;
1037         unsigned long depth;
1038
1039         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1040                 return 0;
1041
1042         this.class = hlock_class(check_source);
1043         if (!save_trace(&this.trace))
1044                 return 0;
1045
1046         result = __search_forward_shortest_path(&this,
1047                                                 hlock_class(check_target),
1048                                                 &target);
1049         if (result) {
1050                 printk("\n%s:search shortest path failed:%d\n", __func__,
1051                         result);
1052                 return 0;
1053         }
1054
1055         depth = get_lock_depth(target);
1056
1057         print_circular_bug_header(target, depth);
1058
1059         parent = get_lock_parent(target);
1060
1061         while (parent) {
1062                 print_circular_bug_entry(parent, --depth);
1063                 parent = get_lock_parent(parent);
1064         }
1065
1066         printk("\nother info that might help us debug this:\n\n");
1067         lockdep_print_held_locks(curr);
1068
1069         printk("\nstack backtrace:\n");
1070         dump_stack();
1071
1072         return 0;
1073 }
1074
1075 #define RECURSION_LIMIT 40
1076
1077 static int noinline print_infinite_recursion_bug(void)
1078 {
1079         if (!debug_locks_off_graph_unlock())
1080                 return 0;
1081
1082         WARN_ON(1);
1083
1084         return 0;
1085 }
1086
1087 unsigned long __lockdep_count_forward_deps(struct lock_class *class,
1088                                            unsigned int depth)
1089 {
1090         struct lock_list *entry;
1091         unsigned long ret = 1;
1092
1093         if (lockdep_dependency_visit(class, depth))
1094                 return 0;
1095
1096         /*
1097          * Recurse this class's dependency list:
1098          */
1099         list_for_each_entry(entry, &class->locks_after, entry)
1100                 ret += __lockdep_count_forward_deps(entry->class, depth + 1);
1101
1102         return ret;
1103 }
1104
1105 unsigned long lockdep_count_forward_deps(struct lock_class *class)
1106 {
1107         unsigned long ret, flags;
1108
1109         local_irq_save(flags);
1110         __raw_spin_lock(&lockdep_lock);
1111         ret = __lockdep_count_forward_deps(class, 0);
1112         __raw_spin_unlock(&lockdep_lock);
1113         local_irq_restore(flags);
1114
1115         return ret;
1116 }
1117
1118 unsigned long __lockdep_count_backward_deps(struct lock_class *class,
1119                                             unsigned int depth)
1120 {
1121         struct lock_list *entry;
1122         unsigned long ret = 1;
1123
1124         if (lockdep_dependency_visit(class, depth))
1125                 return 0;
1126         /*
1127          * Recurse this class's dependency list:
1128          */
1129         list_for_each_entry(entry, &class->locks_before, entry)
1130                 ret += __lockdep_count_backward_deps(entry->class, depth + 1);
1131
1132         return ret;
1133 }
1134
1135 unsigned long lockdep_count_backward_deps(struct lock_class *class)
1136 {
1137         unsigned long ret, flags;
1138
1139         local_irq_save(flags);
1140         __raw_spin_lock(&lockdep_lock);
1141         ret = __lockdep_count_backward_deps(class, 0);
1142         __raw_spin_unlock(&lockdep_lock);
1143         local_irq_restore(flags);
1144
1145         return ret;
1146 }
1147
1148 /*
1149  * Prove that the dependency graph starting at <entry> can not
1150  * lead to <target>. Print an error and return 0 if it does.
1151  */
1152 static noinline int
1153 check_noncircular(struct lock_class *source, unsigned int depth)
1154 {
1155         struct lock_list *entry;
1156
1157         if (lockdep_dependency_visit(source, depth))
1158                 return 1;
1159
1160         debug_atomic_inc(&nr_cyclic_check_recursions);
1161         if (depth > max_recursion_depth)
1162                 max_recursion_depth = depth;
1163         if (depth >= RECURSION_LIMIT)
1164                 return print_infinite_recursion_bug();
1165         /*
1166          * Check this lock's dependency list:
1167          */
1168         list_for_each_entry(entry, &source->locks_after, entry) {
1169                 if (entry->class == hlock_class(check_target))
1170                         return 2;
1171                 debug_atomic_inc(&nr_cyclic_checks);
1172                 if (check_noncircular(entry->class, depth+1) == 2)
1173                         return 2;
1174         }
1175         return 1;
1176 }
1177
1178
1179 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
1180 /*
1181  * Forwards and backwards subgraph searching, for the purposes of
1182  * proving that two subgraphs can be connected by a new dependency
1183  * without creating any illegal irq-safe -> irq-unsafe lock dependency.
1184  */
1185 static enum lock_usage_bit find_usage_bit;
1186 static struct lock_class *forwards_match, *backwards_match;
1187
1188 /*
1189  * Find a node in the forwards-direction dependency sub-graph starting
1190  * at <source> that matches <find_usage_bit>.
1191  *
1192  * Return 2 if such a node exists in the subgraph, and put that node
1193  * into <forwards_match>.
1194  *
1195  * Return 1 otherwise and keep <forwards_match> unchanged.
1196  * Return 0 on error.
1197  */
1198 static noinline int
1199 find_usage_forwards(struct lock_class *source, unsigned int depth)
1200 {
1201         struct lock_list *entry;
1202         int ret;
1203
1204         if (lockdep_dependency_visit(source, depth))
1205                 return 1;
1206
1207         if (depth > max_recursion_depth)
1208                 max_recursion_depth = depth;
1209         if (depth >= RECURSION_LIMIT)
1210                 return print_infinite_recursion_bug();
1211
1212         debug_atomic_inc(&nr_find_usage_forwards_checks);
1213         if (source->usage_mask & (1 << find_usage_bit)) {
1214                 forwards_match = source;
1215                 return 2;
1216         }
1217
1218         /*
1219          * Check this lock's dependency list:
1220          */
1221         list_for_each_entry(entry, &source->locks_after, entry) {
1222                 debug_atomic_inc(&nr_find_usage_forwards_recursions);
1223                 ret = find_usage_forwards(entry->class, depth+1);
1224                 if (ret == 2 || ret == 0)
1225                         return ret;
1226         }
1227         return 1;
1228 }
1229
1230 /*
1231  * Find a node in the backwards-direction dependency sub-graph starting
1232  * at <source> that matches <find_usage_bit>.
1233  *
1234  * Return 2 if such a node exists in the subgraph, and put that node
1235  * into <backwards_match>.
1236  *
1237  * Return 1 otherwise and keep <backwards_match> unchanged.
1238  * Return 0 on error.
1239  */
1240 static noinline int
1241 find_usage_backwards(struct lock_class *source, unsigned int depth)
1242 {
1243         struct lock_list *entry;
1244         int ret;
1245
1246         if (lockdep_dependency_visit(source, depth))
1247                 return 1;
1248
1249         if (!__raw_spin_is_locked(&lockdep_lock))
1250                 return DEBUG_LOCKS_WARN_ON(1);
1251
1252         if (depth > max_recursion_depth)
1253                 max_recursion_depth = depth;
1254         if (depth >= RECURSION_LIMIT)
1255                 return print_infinite_recursion_bug();
1256
1257         debug_atomic_inc(&nr_find_usage_backwards_checks);
1258         if (source->usage_mask & (1 << find_usage_bit)) {
1259                 backwards_match = source;
1260                 return 2;
1261         }
1262
1263         if (!source && debug_locks_off_graph_unlock()) {
1264                 WARN_ON(1);
1265                 return 0;
1266         }
1267
1268         /*
1269          * Check this lock's dependency list:
1270          */
1271         list_for_each_entry(entry, &source->locks_before, entry) {
1272                 debug_atomic_inc(&nr_find_usage_backwards_recursions);
1273                 ret = find_usage_backwards(entry->class, depth+1);
1274                 if (ret == 2 || ret == 0)
1275                         return ret;
1276         }
1277         return 1;
1278 }
1279
1280 static int
1281 print_bad_irq_dependency(struct task_struct *curr,
1282                          struct held_lock *prev,
1283                          struct held_lock *next,
1284                          enum lock_usage_bit bit1,
1285                          enum lock_usage_bit bit2,
1286                          const char *irqclass)
1287 {
1288         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1289                 return 0;
1290
1291         printk("\n======================================================\n");
1292         printk(  "[ INFO: %s-safe -> %s-unsafe lock order detected ]\n",
1293                 irqclass, irqclass);
1294         print_kernel_version();
1295         printk(  "------------------------------------------------------\n");
1296         printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
1297                 curr->comm, task_pid_nr(curr),
1298                 curr->hardirq_context, hardirq_count() >> HARDIRQ_SHIFT,
1299                 curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT,
1300                 curr->hardirqs_enabled,
1301                 curr->softirqs_enabled);
1302         print_lock(next);
1303
1304         printk("\nand this task is already holding:\n");
1305         print_lock(prev);
1306         printk("which would create a new lock dependency:\n");
1307         print_lock_name(hlock_class(prev));
1308         printk(" ->");
1309         print_lock_name(hlock_class(next));
1310         printk("\n");
1311
1312         printk("\nbut this new dependency connects a %s-irq-safe lock:\n",
1313                 irqclass);
1314         print_lock_name(backwards_match);
1315         printk("\n... which became %s-irq-safe at:\n", irqclass);
1316
1317         print_stack_trace(backwards_match->usage_traces + bit1, 1);
1318
1319         printk("\nto a %s-irq-unsafe lock:\n", irqclass);
1320         print_lock_name(forwards_match);
1321         printk("\n... which became %s-irq-unsafe at:\n", irqclass);
1322         printk("...");
1323
1324         print_stack_trace(forwards_match->usage_traces + bit2, 1);
1325
1326         printk("\nother info that might help us debug this:\n\n");
1327         lockdep_print_held_locks(curr);
1328
1329         printk("\nthe %s-irq-safe lock's dependencies:\n", irqclass);
1330         print_lock_dependencies(backwards_match, 0);
1331
1332         printk("\nthe %s-irq-unsafe lock's dependencies:\n", irqclass);
1333         print_lock_dependencies(forwards_match, 0);
1334
1335         printk("\nstack backtrace:\n");
1336         dump_stack();
1337
1338         return 0;
1339 }
1340
1341 static int
1342 check_usage(struct task_struct *curr, struct held_lock *prev,
1343             struct held_lock *next, enum lock_usage_bit bit_backwards,
1344             enum lock_usage_bit bit_forwards, const char *irqclass)
1345 {
1346         int ret;
1347
1348         find_usage_bit = bit_backwards;
1349         /* fills in <backwards_match> */
1350         ret = find_usage_backwards(hlock_class(prev), 0);
1351         if (!ret || ret == 1)
1352                 return ret;
1353
1354         find_usage_bit = bit_forwards;
1355         ret = find_usage_forwards(hlock_class(next), 0);
1356         if (!ret || ret == 1)
1357                 return ret;
1358         /* ret == 2 */
1359         return print_bad_irq_dependency(curr, prev, next,
1360                         bit_backwards, bit_forwards, irqclass);
1361 }
1362
1363 static const char *state_names[] = {
1364 #define LOCKDEP_STATE(__STATE) \
1365         __stringify(__STATE),
1366 #include "lockdep_states.h"
1367 #undef LOCKDEP_STATE
1368 };
1369
1370 static const char *state_rnames[] = {
1371 #define LOCKDEP_STATE(__STATE) \
1372         __stringify(__STATE)"-READ",
1373 #include "lockdep_states.h"
1374 #undef LOCKDEP_STATE
1375 };
1376
1377 static inline const char *state_name(enum lock_usage_bit bit)
1378 {
1379         return (bit & 1) ? state_rnames[bit >> 2] : state_names[bit >> 2];
1380 }
1381
1382 static int exclusive_bit(int new_bit)
1383 {
1384         /*
1385          * USED_IN
1386          * USED_IN_READ
1387          * ENABLED
1388          * ENABLED_READ
1389          *
1390          * bit 0 - write/read
1391          * bit 1 - used_in/enabled
1392          * bit 2+  state
1393          */
1394
1395         int state = new_bit & ~3;
1396         int dir = new_bit & 2;
1397
1398         /*
1399          * keep state, bit flip the direction and strip read.
1400          */
1401         return state | (dir ^ 2);
1402 }
1403
1404 static int check_irq_usage(struct task_struct *curr, struct held_lock *prev,
1405                            struct held_lock *next, enum lock_usage_bit bit)
1406 {
1407         /*
1408          * Prove that the new dependency does not connect a hardirq-safe
1409          * lock with a hardirq-unsafe lock - to achieve this we search
1410          * the backwards-subgraph starting at <prev>, and the
1411          * forwards-subgraph starting at <next>:
1412          */
1413         if (!check_usage(curr, prev, next, bit,
1414                            exclusive_bit(bit), state_name(bit)))
1415                 return 0;
1416
1417         bit++; /* _READ */
1418
1419         /*
1420          * Prove that the new dependency does not connect a hardirq-safe-read
1421          * lock with a hardirq-unsafe lock - to achieve this we search
1422          * the backwards-subgraph starting at <prev>, and the
1423          * forwards-subgraph starting at <next>:
1424          */
1425         if (!check_usage(curr, prev, next, bit,
1426                            exclusive_bit(bit), state_name(bit)))
1427                 return 0;
1428
1429         return 1;
1430 }
1431
1432 static int
1433 check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
1434                 struct held_lock *next)
1435 {
1436 #define LOCKDEP_STATE(__STATE)                                          \
1437         if (!check_irq_usage(curr, prev, next, LOCK_USED_IN_##__STATE)) \
1438                 return 0;
1439 #include "lockdep_states.h"
1440 #undef LOCKDEP_STATE
1441
1442         return 1;
1443 }
1444
1445 static void inc_chains(void)
1446 {
1447         if (current->hardirq_context)
1448                 nr_hardirq_chains++;
1449         else {
1450                 if (current->softirq_context)
1451                         nr_softirq_chains++;
1452                 else
1453                         nr_process_chains++;
1454         }
1455 }
1456
1457 #else
1458
1459 static inline int
1460 check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
1461                 struct held_lock *next)
1462 {
1463         return 1;
1464 }
1465
1466 static inline void inc_chains(void)
1467 {
1468         nr_process_chains++;
1469 }
1470
1471 #endif
1472
1473 static int
1474 print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
1475                    struct held_lock *next)
1476 {
1477         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1478                 return 0;
1479
1480         printk("\n=============================================\n");
1481         printk(  "[ INFO: possible recursive locking detected ]\n");
1482         print_kernel_version();
1483         printk(  "---------------------------------------------\n");
1484         printk("%s/%d is trying to acquire lock:\n",
1485                 curr->comm, task_pid_nr(curr));
1486         print_lock(next);
1487         printk("\nbut task is already holding lock:\n");
1488         print_lock(prev);
1489
1490         printk("\nother info that might help us debug this:\n");
1491         lockdep_print_held_locks(curr);
1492
1493         printk("\nstack backtrace:\n");
1494         dump_stack();
1495
1496         return 0;
1497 }
1498
1499 /*
1500  * Check whether we are holding such a class already.
1501  *
1502  * (Note that this has to be done separately, because the graph cannot
1503  * detect such classes of deadlocks.)
1504  *
1505  * Returns: 0 on deadlock detected, 1 on OK, 2 on recursive read
1506  */
1507 static int
1508 check_deadlock(struct task_struct *curr, struct held_lock *next,
1509                struct lockdep_map *next_instance, int read)
1510 {
1511         struct held_lock *prev;
1512         struct held_lock *nest = NULL;
1513         int i;
1514
1515         for (i = 0; i < curr->lockdep_depth; i++) {
1516                 prev = curr->held_locks + i;
1517
1518                 if (prev->instance == next->nest_lock)
1519                         nest = prev;
1520
1521                 if (hlock_class(prev) != hlock_class(next))
1522                         continue;
1523
1524                 /*
1525                  * Allow read-after-read recursion of the same
1526                  * lock class (i.e. read_lock(lock)+read_lock(lock)):
1527                  */
1528                 if ((read == 2) && prev->read)
1529                         return 2;
1530
1531                 /*
1532                  * We're holding the nest_lock, which serializes this lock's
1533                  * nesting behaviour.
1534                  */
1535                 if (nest)
1536                         return 2;
1537
1538                 return print_deadlock_bug(curr, prev, next);
1539         }
1540         return 1;
1541 }
1542
1543 /*
1544  * There was a chain-cache miss, and we are about to add a new dependency
1545  * to a previous lock. We recursively validate the following rules:
1546  *
1547  *  - would the adding of the <prev> -> <next> dependency create a
1548  *    circular dependency in the graph? [== circular deadlock]
1549  *
1550  *  - does the new prev->next dependency connect any hardirq-safe lock
1551  *    (in the full backwards-subgraph starting at <prev>) with any
1552  *    hardirq-unsafe lock (in the full forwards-subgraph starting at
1553  *    <next>)? [== illegal lock inversion with hardirq contexts]
1554  *
1555  *  - does the new prev->next dependency connect any softirq-safe lock
1556  *    (in the full backwards-subgraph starting at <prev>) with any
1557  *    softirq-unsafe lock (in the full forwards-subgraph starting at
1558  *    <next>)? [== illegal lock inversion with softirq contexts]
1559  *
1560  * any of these scenarios could lead to a deadlock.
1561  *
1562  * Then if all the validations pass, we add the forwards and backwards
1563  * dependency.
1564  */
1565 static int
1566 check_prev_add(struct task_struct *curr, struct held_lock *prev,
1567                struct held_lock *next, int distance)
1568 {
1569         struct lock_list *entry;
1570         int ret;
1571
1572         /*
1573          * Prove that the new <prev> -> <next> dependency would not
1574          * create a circular dependency in the graph. (We do this by
1575          * forward-recursing into the graph starting at <next>, and
1576          * checking whether we can reach <prev>.)
1577          *
1578          * We are using global variables to control the recursion, to
1579          * keep the stackframe size of the recursive functions low:
1580          */
1581         check_source = next;
1582         check_target = prev;
1583         if (check_noncircular(hlock_class(next), 0) == 2)
1584                 return print_circular_bug();
1585
1586
1587         if (!check_prev_add_irq(curr, prev, next))
1588                 return 0;
1589
1590         /*
1591          * For recursive read-locks we do all the dependency checks,
1592          * but we dont store read-triggered dependencies (only
1593          * write-triggered dependencies). This ensures that only the
1594          * write-side dependencies matter, and that if for example a
1595          * write-lock never takes any other locks, then the reads are
1596          * equivalent to a NOP.
1597          */
1598         if (next->read == 2 || prev->read == 2)
1599                 return 1;
1600         /*
1601          * Is the <prev> -> <next> dependency already present?
1602          *
1603          * (this may occur even though this is a new chain: consider
1604          *  e.g. the L1 -> L2 -> L3 -> L4 and the L5 -> L1 -> L2 -> L3
1605          *  chains - the second one will be new, but L1 already has
1606          *  L2 added to its dependency list, due to the first chain.)
1607          */
1608         list_for_each_entry(entry, &hlock_class(prev)->locks_after, entry) {
1609                 if (entry->class == hlock_class(next)) {
1610                         if (distance == 1)
1611                                 entry->distance = 1;
1612                         return 2;
1613                 }
1614         }
1615
1616         /*
1617          * Ok, all validations passed, add the new lock
1618          * to the previous lock's dependency list:
1619          */
1620         ret = add_lock_to_list(hlock_class(prev), hlock_class(next),
1621                                &hlock_class(prev)->locks_after,
1622                                next->acquire_ip, distance);
1623
1624         if (!ret)
1625                 return 0;
1626
1627         ret = add_lock_to_list(hlock_class(next), hlock_class(prev),
1628                                &hlock_class(next)->locks_before,
1629                                next->acquire_ip, distance);
1630         if (!ret)
1631                 return 0;
1632
1633         /*
1634          * Debugging printouts:
1635          */
1636         if (verbose(hlock_class(prev)) || verbose(hlock_class(next))) {
1637                 graph_unlock();
1638                 printk("\n new dependency: ");
1639                 print_lock_name(hlock_class(prev));
1640                 printk(" => ");
1641                 print_lock_name(hlock_class(next));
1642                 printk("\n");
1643                 dump_stack();
1644                 return graph_lock();
1645         }
1646         return 1;
1647 }
1648
1649 /*
1650  * Add the dependency to all directly-previous locks that are 'relevant'.
1651  * The ones that are relevant are (in increasing distance from curr):
1652  * all consecutive trylock entries and the final non-trylock entry - or
1653  * the end of this context's lock-chain - whichever comes first.
1654  */
1655 static int
1656 check_prevs_add(struct task_struct *curr, struct held_lock *next)
1657 {
1658         int depth = curr->lockdep_depth;
1659         struct held_lock *hlock;
1660
1661         /*
1662          * Debugging checks.
1663          *
1664          * Depth must not be zero for a non-head lock:
1665          */
1666         if (!depth)
1667                 goto out_bug;
1668         /*
1669          * At least two relevant locks must exist for this
1670          * to be a head:
1671          */
1672         if (curr->held_locks[depth].irq_context !=
1673                         curr->held_locks[depth-1].irq_context)
1674                 goto out_bug;
1675
1676         for (;;) {
1677                 int distance = curr->lockdep_depth - depth + 1;
1678                 hlock = curr->held_locks + depth-1;
1679                 /*
1680                  * Only non-recursive-read entries get new dependencies
1681                  * added:
1682                  */
1683                 if (hlock->read != 2) {
1684                         if (!check_prev_add(curr, hlock, next, distance))
1685                                 return 0;
1686                         /*
1687                          * Stop after the first non-trylock entry,
1688                          * as non-trylock entries have added their
1689                          * own direct dependencies already, so this
1690                          * lock is connected to them indirectly:
1691                          */
1692                         if (!hlock->trylock)
1693                                 break;
1694                 }
1695                 depth--;
1696                 /*
1697                  * End of lock-stack?
1698                  */
1699                 if (!depth)
1700                         break;
1701                 /*
1702                  * Stop the search if we cross into another context:
1703                  */
1704                 if (curr->held_locks[depth].irq_context !=
1705                                 curr->held_locks[depth-1].irq_context)
1706                         break;
1707         }
1708         return 1;
1709 out_bug:
1710         if (!debug_locks_off_graph_unlock())
1711                 return 0;
1712
1713         WARN_ON(1);
1714
1715         return 0;
1716 }
1717
1718 unsigned long nr_lock_chains;
1719 struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
1720 int nr_chain_hlocks;
1721 static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
1722
1723 struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
1724 {
1725         return lock_classes + chain_hlocks[chain->base + i];
1726 }
1727
1728 /*
1729  * Look up a dependency chain. If the key is not present yet then
1730  * add it and return 1 - in this case the new dependency chain is
1731  * validated. If the key is already hashed, return 0.
1732  * (On return with 1 graph_lock is held.)
1733  */
1734 static inline int lookup_chain_cache(struct task_struct *curr,
1735                                      struct held_lock *hlock,
1736                                      u64 chain_key)
1737 {
1738         struct lock_class *class = hlock_class(hlock);
1739         struct list_head *hash_head = chainhashentry(chain_key);
1740         struct lock_chain *chain;
1741         struct held_lock *hlock_curr, *hlock_next;
1742         int i, j, n, cn;
1743
1744         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
1745                 return 0;
1746         /*
1747          * We can walk it lock-free, because entries only get added
1748          * to the hash:
1749          */
1750         list_for_each_entry(chain, hash_head, entry) {
1751                 if (chain->chain_key == chain_key) {
1752 cache_hit:
1753                         debug_atomic_inc(&chain_lookup_hits);
1754                         if (very_verbose(class))
1755                                 printk("\nhash chain already cached, key: "
1756                                         "%016Lx tail class: [%p] %s\n",
1757                                         (unsigned long long)chain_key,
1758                                         class->key, class->name);
1759                         return 0;
1760                 }
1761         }
1762         if (very_verbose(class))
1763                 printk("\nnew hash chain, key: %016Lx tail class: [%p] %s\n",
1764                         (unsigned long long)chain_key, class->key, class->name);
1765         /*
1766          * Allocate a new chain entry from the static array, and add
1767          * it to the hash:
1768          */
1769         if (!graph_lock())
1770                 return 0;
1771         /*
1772          * We have to walk the chain again locked - to avoid duplicates:
1773          */
1774         list_for_each_entry(chain, hash_head, entry) {
1775                 if (chain->chain_key == chain_key) {
1776                         graph_unlock();
1777                         goto cache_hit;
1778                 }
1779         }
1780         if (unlikely(nr_lock_chains >= MAX_LOCKDEP_CHAINS)) {
1781                 if (!debug_locks_off_graph_unlock())
1782                         return 0;
1783
1784                 printk("BUG: MAX_LOCKDEP_CHAINS too low!\n");
1785                 printk("turning off the locking correctness validator.\n");
1786                 dump_stack();
1787                 return 0;
1788         }
1789         chain = lock_chains + nr_lock_chains++;
1790         chain->chain_key = chain_key;
1791         chain->irq_context = hlock->irq_context;
1792         /* Find the first held_lock of current chain */
1793         hlock_next = hlock;
1794         for (i = curr->lockdep_depth - 1; i >= 0; i--) {
1795                 hlock_curr = curr->held_locks + i;
1796                 if (hlock_curr->irq_context != hlock_next->irq_context)
1797                         break;
1798                 hlock_next = hlock;
1799         }
1800         i++;
1801         chain->depth = curr->lockdep_depth + 1 - i;
1802         cn = nr_chain_hlocks;
1803         while (cn + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS) {
1804                 n = cmpxchg(&nr_chain_hlocks, cn, cn + chain->depth);
1805                 if (n == cn)
1806                         break;
1807                 cn = n;
1808         }
1809         if (likely(cn + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) {
1810                 chain->base = cn;
1811                 for (j = 0; j < chain->depth - 1; j++, i++) {
1812                         int lock_id = curr->held_locks[i].class_idx - 1;
1813                         chain_hlocks[chain->base + j] = lock_id;
1814                 }
1815                 chain_hlocks[chain->base + j] = class - lock_classes;
1816         }
1817         list_add_tail_rcu(&chain->entry, hash_head);
1818         debug_atomic_inc(&chain_lookup_misses);
1819         inc_chains();
1820
1821         return 1;
1822 }
1823
1824 static int validate_chain(struct task_struct *curr, struct lockdep_map *lock,
1825                 struct held_lock *hlock, int chain_head, u64 chain_key)
1826 {
1827         /*
1828          * Trylock needs to maintain the stack of held locks, but it
1829          * does not add new dependencies, because trylock can be done
1830          * in any order.
1831          *
1832          * We look up the chain_key and do the O(N^2) check and update of
1833          * the dependencies only if this is a new dependency chain.
1834          * (If lookup_chain_cache() returns with 1 it acquires
1835          * graph_lock for us)
1836          */
1837         if (!hlock->trylock && (hlock->check == 2) &&
1838             lookup_chain_cache(curr, hlock, chain_key)) {
1839                 /*
1840                  * Check whether last held lock:
1841                  *
1842                  * - is irq-safe, if this lock is irq-unsafe
1843                  * - is softirq-safe, if this lock is hardirq-unsafe
1844                  *
1845                  * And check whether the new lock's dependency graph
1846                  * could lead back to the previous lock.
1847                  *
1848                  * any of these scenarios could lead to a deadlock. If
1849                  * All validations
1850                  */
1851                 int ret = check_deadlock(curr, hlock, lock, hlock->read);
1852
1853                 if (!ret)
1854                         return 0;
1855                 /*
1856                  * Mark recursive read, as we jump over it when
1857                  * building dependencies (just like we jump over
1858                  * trylock entries):
1859                  */
1860                 if (ret == 2)
1861                         hlock->read = 2;
1862                 /*
1863                  * Add dependency only if this lock is not the head
1864                  * of the chain, and if it's not a secondary read-lock:
1865                  */
1866                 if (!chain_head && ret != 2)
1867                         if (!check_prevs_add(curr, hlock))
1868                                 return 0;
1869                 graph_unlock();
1870         } else
1871                 /* after lookup_chain_cache(): */
1872                 if (unlikely(!debug_locks))
1873                         return 0;
1874
1875         return 1;
1876 }
1877 #else
1878 static inline int validate_chain(struct task_struct *curr,
1879                 struct lockdep_map *lock, struct held_lock *hlock,
1880                 int chain_head, u64 chain_key)
1881 {
1882         return 1;
1883 }
1884 #endif
1885
1886 /*
1887  * We are building curr_chain_key incrementally, so double-check
1888  * it from scratch, to make sure that it's done correctly:
1889  */
1890 static void check_chain_key(struct task_struct *curr)
1891 {
1892 #ifdef CONFIG_DEBUG_LOCKDEP
1893         struct held_lock *hlock, *prev_hlock = NULL;
1894         unsigned int i, id;
1895         u64 chain_key = 0;
1896
1897         for (i = 0; i < curr->lockdep_depth; i++) {
1898                 hlock = curr->held_locks + i;
1899                 if (chain_key != hlock->prev_chain_key) {
1900                         debug_locks_off();
1901                         WARN(1, "hm#1, depth: %u [%u], %016Lx != %016Lx\n",
1902                                 curr->lockdep_depth, i,
1903                                 (unsigned long long)chain_key,
1904                                 (unsigned long long)hlock->prev_chain_key);
1905                         return;
1906                 }
1907                 id = hlock->class_idx - 1;
1908                 if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
1909                         return;
1910
1911                 if (prev_hlock && (prev_hlock->irq_context !=
1912                                                         hlock->irq_context))
1913                         chain_key = 0;
1914                 chain_key = iterate_chain_key(chain_key, id);
1915                 prev_hlock = hlock;
1916         }
1917         if (chain_key != curr->curr_chain_key) {
1918                 debug_locks_off();
1919                 WARN(1, "hm#2, depth: %u [%u], %016Lx != %016Lx\n",
1920                         curr->lockdep_depth, i,
1921                         (unsigned long long)chain_key,
1922                         (unsigned long long)curr->curr_chain_key);
1923         }
1924 #endif
1925 }
1926
1927 static int
1928 print_usage_bug(struct task_struct *curr, struct held_lock *this,
1929                 enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
1930 {
1931         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1932                 return 0;
1933
1934         printk("\n=================================\n");
1935         printk(  "[ INFO: inconsistent lock state ]\n");
1936         print_kernel_version();
1937         printk(  "---------------------------------\n");
1938
1939         printk("inconsistent {%s} -> {%s} usage.\n",
1940                 usage_str[prev_bit], usage_str[new_bit]);
1941
1942         printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] takes:\n",
1943                 curr->comm, task_pid_nr(curr),
1944                 trace_hardirq_context(curr), hardirq_count() >> HARDIRQ_SHIFT,
1945                 trace_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT,
1946                 trace_hardirqs_enabled(curr),
1947                 trace_softirqs_enabled(curr));
1948         print_lock(this);
1949
1950         printk("{%s} state was registered at:\n", usage_str[prev_bit]);
1951         print_stack_trace(hlock_class(this)->usage_traces + prev_bit, 1);
1952
1953         print_irqtrace_events(curr);
1954         printk("\nother info that might help us debug this:\n");
1955         lockdep_print_held_locks(curr);
1956
1957         printk("\nstack backtrace:\n");
1958         dump_stack();
1959
1960         return 0;
1961 }
1962
1963 /*
1964  * Print out an error if an invalid bit is set:
1965  */
1966 static inline int
1967 valid_state(struct task_struct *curr, struct held_lock *this,
1968             enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit)
1969 {
1970         if (unlikely(hlock_class(this)->usage_mask & (1 << bad_bit)))
1971                 return print_usage_bug(curr, this, bad_bit, new_bit);
1972         return 1;
1973 }
1974
1975 static int mark_lock(struct task_struct *curr, struct held_lock *this,
1976                      enum lock_usage_bit new_bit);
1977
1978 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
1979
1980 /*
1981  * print irq inversion bug:
1982  */
1983 static int
1984 print_irq_inversion_bug(struct task_struct *curr, struct lock_class *other,
1985                         struct held_lock *this, int forwards,
1986                         const char *irqclass)
1987 {
1988         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1989                 return 0;
1990
1991         printk("\n=========================================================\n");
1992         printk(  "[ INFO: possible irq lock inversion dependency detected ]\n");
1993         print_kernel_version();
1994         printk(  "---------------------------------------------------------\n");
1995         printk("%s/%d just changed the state of lock:\n",
1996                 curr->comm, task_pid_nr(curr));
1997         print_lock(this);
1998         if (forwards)
1999                 printk("but this lock took another, %s-unsafe lock in the past:\n", irqclass);
2000         else
2001                 printk("but this lock was taken by another, %s-safe lock in the past:\n", irqclass);
2002         print_lock_name(other);
2003         printk("\n\nand interrupts could create inverse lock ordering between them.\n\n");
2004
2005         printk("\nother info that might help us debug this:\n");
2006         lockdep_print_held_locks(curr);
2007
2008         printk("\nthe first lock's dependencies:\n");
2009         print_lock_dependencies(hlock_class(this), 0);
2010
2011         printk("\nthe second lock's dependencies:\n");
2012         print_lock_dependencies(other, 0);
2013
2014         printk("\nstack backtrace:\n");
2015         dump_stack();
2016
2017         return 0;
2018 }
2019
2020 /*
2021  * Prove that in the forwards-direction subgraph starting at <this>
2022  * there is no lock matching <mask>:
2023  */
2024 static int
2025 check_usage_forwards(struct task_struct *curr, struct held_lock *this,
2026                      enum lock_usage_bit bit, const char *irqclass)
2027 {
2028         int ret;
2029
2030         find_usage_bit = bit;
2031         /* fills in <forwards_match> */
2032         ret = find_usage_forwards(hlock_class(this), 0);
2033         if (!ret || ret == 1)
2034                 return ret;
2035
2036         return print_irq_inversion_bug(curr, forwards_match, this, 1, irqclass);
2037 }
2038
2039 /*
2040  * Prove that in the backwards-direction subgraph starting at <this>
2041  * there is no lock matching <mask>:
2042  */
2043 static int
2044 check_usage_backwards(struct task_struct *curr, struct held_lock *this,
2045                       enum lock_usage_bit bit, const char *irqclass)
2046 {
2047         int ret;
2048
2049         find_usage_bit = bit;
2050         /* fills in <backwards_match> */
2051         ret = find_usage_backwards(hlock_class(this), 0);
2052         if (!ret || ret == 1)
2053                 return ret;
2054
2055         return print_irq_inversion_bug(curr, backwards_match, this, 0, irqclass);
2056 }
2057
2058 void print_irqtrace_events(struct task_struct *curr)
2059 {
2060         printk("irq event stamp: %u\n", curr->irq_events);
2061         printk("hardirqs last  enabled at (%u): ", curr->hardirq_enable_event);
2062         print_ip_sym(curr->hardirq_enable_ip);
2063         printk("hardirqs last disabled at (%u): ", curr->hardirq_disable_event);
2064         print_ip_sym(curr->hardirq_disable_ip);
2065         printk("softirqs last  enabled at (%u): ", curr->softirq_enable_event);
2066         print_ip_sym(curr->softirq_enable_ip);
2067         printk("softirqs last disabled at (%u): ", curr->softirq_disable_event);
2068         print_ip_sym(curr->softirq_disable_ip);
2069 }
2070
2071 static int HARDIRQ_verbose(struct lock_class *class)
2072 {
2073 #if HARDIRQ_VERBOSE
2074         return class_filter(class);
2075 #endif
2076         return 0;
2077 }
2078
2079 static int SOFTIRQ_verbose(struct lock_class *class)
2080 {
2081 #if SOFTIRQ_VERBOSE
2082         return class_filter(class);
2083 #endif
2084         return 0;
2085 }
2086
2087 static int RECLAIM_FS_verbose(struct lock_class *class)
2088 {
2089 #if RECLAIM_VERBOSE
2090         return class_filter(class);
2091 #endif
2092         return 0;
2093 }
2094
2095 #define STRICT_READ_CHECKS      1
2096
2097 static int (*state_verbose_f[])(struct lock_class *class) = {
2098 #define LOCKDEP_STATE(__STATE) \
2099         __STATE##_verbose,
2100 #include "lockdep_states.h"
2101 #undef LOCKDEP_STATE
2102 };
2103
2104 static inline int state_verbose(enum lock_usage_bit bit,
2105                                 struct lock_class *class)
2106 {
2107         return state_verbose_f[bit >> 2](class);
2108 }
2109
2110 typedef int (*check_usage_f)(struct task_struct *, struct held_lock *,
2111                              enum lock_usage_bit bit, const char *name);
2112
2113 static int
2114 mark_lock_irq(struct task_struct *curr, struct held_lock *this,
2115                 enum lock_usage_bit new_bit)
2116 {
2117         int excl_bit = exclusive_bit(new_bit);
2118         int read = new_bit & 1;
2119         int dir = new_bit & 2;
2120
2121         /*
2122          * mark USED_IN has to look forwards -- to ensure no dependency
2123          * has ENABLED state, which would allow recursion deadlocks.
2124          *
2125          * mark ENABLED has to look backwards -- to ensure no dependee
2126          * has USED_IN state, which, again, would allow  recursion deadlocks.
2127          */
2128         check_usage_f usage = dir ?
2129                 check_usage_backwards : check_usage_forwards;
2130
2131         /*
2132          * Validate that this particular lock does not have conflicting
2133          * usage states.
2134          */
2135         if (!valid_state(curr, this, new_bit, excl_bit))
2136                 return 0;
2137
2138         /*
2139          * Validate that the lock dependencies don't have conflicting usage
2140          * states.
2141          */
2142         if ((!read || !dir || STRICT_READ_CHECKS) &&
2143                         !usage(curr, this, excl_bit, state_name(new_bit & ~1)))
2144                 return 0;
2145
2146         /*
2147          * Check for read in write conflicts
2148          */
2149         if (!read) {
2150                 if (!valid_state(curr, this, new_bit, excl_bit + 1))
2151                         return 0;
2152
2153                 if (STRICT_READ_CHECKS &&
2154                         !usage(curr, this, excl_bit + 1,
2155                                 state_name(new_bit + 1)))
2156                         return 0;
2157         }
2158
2159         if (state_verbose(new_bit, hlock_class(this)))
2160                 return 2;
2161
2162         return 1;
2163 }
2164
2165 enum mark_type {
2166 #define LOCKDEP_STATE(__STATE)  __STATE,
2167 #include "lockdep_states.h"
2168 #undef LOCKDEP_STATE
2169 };
2170
2171 /*
2172  * Mark all held locks with a usage bit:
2173  */
2174 static int
2175 mark_held_locks(struct task_struct *curr, enum mark_type mark)
2176 {
2177         enum lock_usage_bit usage_bit;
2178         struct held_lock *hlock;
2179         int i;
2180
2181         for (i = 0; i < curr->lockdep_depth; i++) {
2182                 hlock = curr->held_locks + i;
2183
2184                 usage_bit = 2 + (mark << 2); /* ENABLED */
2185                 if (hlock->read)
2186                         usage_bit += 1; /* READ */
2187
2188                 BUG_ON(usage_bit >= LOCK_USAGE_STATES);
2189
2190                 if (!mark_lock(curr, hlock, usage_bit))
2191                         return 0;
2192         }
2193
2194         return 1;
2195 }
2196
2197 /*
2198  * Debugging helper: via this flag we know that we are in
2199  * 'early bootup code', and will warn about any invalid irqs-on event:
2200  */
2201 static int early_boot_irqs_enabled;
2202
2203 void early_boot_irqs_off(void)
2204 {
2205         early_boot_irqs_enabled = 0;
2206 }
2207
2208 void early_boot_irqs_on(void)
2209 {
2210         early_boot_irqs_enabled = 1;
2211 }
2212
2213 /*
2214  * Hardirqs will be enabled:
2215  */
2216 void trace_hardirqs_on_caller(unsigned long ip)
2217 {
2218         struct task_struct *curr = current;
2219
2220         time_hardirqs_on(CALLER_ADDR0, ip);
2221
2222         if (unlikely(!debug_locks || current->lockdep_recursion))
2223                 return;
2224
2225         if (DEBUG_LOCKS_WARN_ON(unlikely(!early_boot_irqs_enabled)))
2226                 return;
2227
2228         if (unlikely(curr->hardirqs_enabled)) {
2229                 debug_atomic_inc(&redundant_hardirqs_on);
2230                 return;
2231         }
2232         /* we'll do an OFF -> ON transition: */
2233         curr->hardirqs_enabled = 1;
2234
2235         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2236                 return;
2237         if (DEBUG_LOCKS_WARN_ON(current->hardirq_context))
2238                 return;
2239         /*
2240          * We are going to turn hardirqs on, so set the
2241          * usage bit for all held locks:
2242          */
2243         if (!mark_held_locks(curr, HARDIRQ))
2244                 return;
2245         /*
2246          * If we have softirqs enabled, then set the usage
2247          * bit for all held locks. (disabled hardirqs prevented
2248          * this bit from being set before)
2249          */
2250         if (curr->softirqs_enabled)
2251                 if (!mark_held_locks(curr, SOFTIRQ))
2252                         return;
2253
2254         curr->hardirq_enable_ip = ip;
2255         curr->hardirq_enable_event = ++curr->irq_events;
2256         debug_atomic_inc(&hardirqs_on_events);
2257 }
2258 EXPORT_SYMBOL(trace_hardirqs_on_caller);
2259
2260 void trace_hardirqs_on(void)
2261 {
2262         trace_hardirqs_on_caller(CALLER_ADDR0);
2263 }
2264 EXPORT_SYMBOL(trace_hardirqs_on);
2265
2266 /*
2267  * Hardirqs were disabled:
2268  */
2269 void trace_hardirqs_off_caller(unsigned long ip)
2270 {
2271         struct task_struct *curr = current;
2272
2273         time_hardirqs_off(CALLER_ADDR0, ip);
2274
2275         if (unlikely(!debug_locks || current->lockdep_recursion))
2276                 return;
2277
2278         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2279                 return;
2280
2281         if (curr->hardirqs_enabled) {
2282                 /*
2283                  * We have done an ON -> OFF transition:
2284                  */
2285                 curr->hardirqs_enabled = 0;
2286                 curr->hardirq_disable_ip = ip;
2287                 curr->hardirq_disable_event = ++curr->irq_events;
2288                 debug_atomic_inc(&hardirqs_off_events);
2289         } else
2290                 debug_atomic_inc(&redundant_hardirqs_off);
2291 }
2292 EXPORT_SYMBOL(trace_hardirqs_off_caller);
2293
2294 void trace_hardirqs_off(void)
2295 {
2296         trace_hardirqs_off_caller(CALLER_ADDR0);
2297 }
2298 EXPORT_SYMBOL(trace_hardirqs_off);
2299
2300 /*
2301  * Softirqs will be enabled:
2302  */
2303 void trace_softirqs_on(unsigned long ip)
2304 {
2305         struct task_struct *curr = current;
2306
2307         if (unlikely(!debug_locks))
2308                 return;
2309
2310         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2311                 return;
2312
2313         if (curr->softirqs_enabled) {
2314                 debug_atomic_inc(&redundant_softirqs_on);
2315                 return;
2316         }
2317
2318         /*
2319          * We'll do an OFF -> ON transition:
2320          */
2321         curr->softirqs_enabled = 1;
2322         curr->softirq_enable_ip = ip;
2323         curr->softirq_enable_event = ++curr->irq_events;
2324         debug_atomic_inc(&softirqs_on_events);
2325         /*
2326          * We are going to turn softirqs on, so set the
2327          * usage bit for all held locks, if hardirqs are
2328          * enabled too:
2329          */
2330         if (curr->hardirqs_enabled)
2331                 mark_held_locks(curr, SOFTIRQ);
2332 }
2333
2334 /*
2335  * Softirqs were disabled:
2336  */
2337 void trace_softirqs_off(unsigned long ip)
2338 {
2339         struct task_struct *curr = current;
2340
2341         if (unlikely(!debug_locks))
2342                 return;
2343
2344         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2345                 return;
2346
2347         if (curr->softirqs_enabled) {
2348                 /*
2349                  * We have done an ON -> OFF transition:
2350                  */
2351                 curr->softirqs_enabled = 0;
2352                 curr->softirq_disable_ip = ip;
2353                 curr->softirq_disable_event = ++curr->irq_events;
2354                 debug_atomic_inc(&softirqs_off_events);
2355                 DEBUG_LOCKS_WARN_ON(!softirq_count());
2356         } else
2357                 debug_atomic_inc(&redundant_softirqs_off);
2358 }
2359
2360 static void __lockdep_trace_alloc(gfp_t gfp_mask, unsigned long flags)
2361 {
2362         struct task_struct *curr = current;
2363
2364         if (unlikely(!debug_locks))
2365                 return;
2366
2367         /* no reclaim without waiting on it */
2368         if (!(gfp_mask & __GFP_WAIT))
2369                 return;
2370
2371         /* this guy won't enter reclaim */
2372         if ((curr->flags & PF_MEMALLOC) && !(gfp_mask & __GFP_NOMEMALLOC))
2373                 return;
2374
2375         /* We're only interested __GFP_FS allocations for now */
2376         if (!(gfp_mask & __GFP_FS))
2377                 return;
2378
2379         if (DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags)))
2380                 return;
2381
2382         mark_held_locks(curr, RECLAIM_FS);
2383 }
2384
2385 static void check_flags(unsigned long flags);
2386
2387 void lockdep_trace_alloc(gfp_t gfp_mask)
2388 {
2389         unsigned long flags;
2390
2391         if (unlikely(current->lockdep_recursion))
2392                 return;
2393
2394         raw_local_irq_save(flags);
2395         check_flags(flags);
2396         current->lockdep_recursion = 1;
2397         __lockdep_trace_alloc(gfp_mask, flags);
2398         current->lockdep_recursion = 0;
2399         raw_local_irq_restore(flags);
2400 }
2401
2402 static int mark_irqflags(struct task_struct *curr, struct held_lock *hlock)
2403 {
2404         /*
2405          * If non-trylock use in a hardirq or softirq context, then
2406          * mark the lock as used in these contexts:
2407          */
2408         if (!hlock->trylock) {
2409                 if (hlock->read) {
2410                         if (curr->hardirq_context)
2411                                 if (!mark_lock(curr, hlock,
2412                                                 LOCK_USED_IN_HARDIRQ_READ))
2413                                         return 0;
2414                         if (curr->softirq_context)
2415                                 if (!mark_lock(curr, hlock,
2416                                                 LOCK_USED_IN_SOFTIRQ_READ))
2417                                         return 0;
2418                 } else {
2419                         if (curr->hardirq_context)
2420                                 if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ))
2421                                         return 0;
2422                         if (curr->softirq_context)
2423                                 if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ))
2424                                         return 0;
2425                 }
2426         }
2427         if (!hlock->hardirqs_off) {
2428                 if (hlock->read) {
2429                         if (!mark_lock(curr, hlock,
2430                                         LOCK_ENABLED_HARDIRQ_READ))
2431                                 return 0;
2432                         if (curr->softirqs_enabled)
2433                                 if (!mark_lock(curr, hlock,
2434                                                 LOCK_ENABLED_SOFTIRQ_READ))
2435                                         return 0;
2436                 } else {
2437                         if (!mark_lock(curr, hlock,
2438                                         LOCK_ENABLED_HARDIRQ))
2439                                 return 0;
2440                         if (curr->softirqs_enabled)
2441                                 if (!mark_lock(curr, hlock,
2442                                                 LOCK_ENABLED_SOFTIRQ))
2443                                         return 0;
2444                 }
2445         }
2446
2447         /*
2448          * We reuse the irq context infrastructure more broadly as a general
2449          * context checking code. This tests GFP_FS recursion (a lock taken
2450          * during reclaim for a GFP_FS allocation is held over a GFP_FS
2451          * allocation).
2452          */
2453         if (!hlock->trylock && (curr->lockdep_reclaim_gfp & __GFP_FS)) {
2454                 if (hlock->read) {
2455                         if (!mark_lock(curr, hlock, LOCK_USED_IN_RECLAIM_FS_READ))
2456                                         return 0;
2457                 } else {
2458                         if (!mark_lock(curr, hlock, LOCK_USED_IN_RECLAIM_FS))
2459                                         return 0;
2460                 }
2461         }
2462
2463         return 1;
2464 }
2465
2466 static int separate_irq_context(struct task_struct *curr,
2467                 struct held_lock *hlock)
2468 {
2469         unsigned int depth = curr->lockdep_depth;
2470
2471         /*
2472          * Keep track of points where we cross into an interrupt context:
2473          */
2474         hlock->irq_context = 2*(curr->hardirq_context ? 1 : 0) +
2475                                 curr->softirq_context;
2476         if (depth) {
2477                 struct held_lock *prev_hlock;
2478
2479                 prev_hlock = curr->held_locks + depth-1;
2480                 /*
2481                  * If we cross into another context, reset the
2482                  * hash key (this also prevents the checking and the
2483                  * adding of the dependency to 'prev'):
2484                  */
2485                 if (prev_hlock->irq_context != hlock->irq_context)
2486                         return 1;
2487         }
2488         return 0;
2489 }
2490
2491 #else
2492
2493 static inline
2494 int mark_lock_irq(struct task_struct *curr, struct held_lock *this,
2495                 enum lock_usage_bit new_bit)
2496 {
2497         WARN_ON(1);
2498         return 1;
2499 }
2500
2501 static inline int mark_irqflags(struct task_struct *curr,
2502                 struct held_lock *hlock)
2503 {
2504         return 1;
2505 }
2506
2507 static inline int separate_irq_context(struct task_struct *curr,
2508                 struct held_lock *hlock)
2509 {
2510         return 0;
2511 }
2512
2513 void lockdep_trace_alloc(gfp_t gfp_mask)
2514 {
2515 }
2516
2517 #endif
2518
2519 /*
2520  * Mark a lock with a usage bit, and validate the state transition:
2521  */
2522 static int mark_lock(struct task_struct *curr, struct held_lock *this,
2523                              enum lock_usage_bit new_bit)
2524 {
2525         unsigned int new_mask = 1 << new_bit, ret = 1;
2526
2527         /*
2528          * If already set then do not dirty the cacheline,
2529          * nor do any checks:
2530          */
2531         if (likely(hlock_class(this)->usage_mask & new_mask))
2532                 return 1;
2533
2534         if (!graph_lock())
2535                 return 0;
2536         /*
2537          * Make sure we didnt race:
2538          */
2539         if (unlikely(hlock_class(this)->usage_mask & new_mask)) {
2540                 graph_unlock();
2541                 return 1;
2542         }
2543
2544         hlock_class(this)->usage_mask |= new_mask;
2545
2546         if (!save_trace(hlock_class(this)->usage_traces + new_bit))
2547                 return 0;
2548
2549         switch (new_bit) {
2550 #define LOCKDEP_STATE(__STATE)                  \
2551         case LOCK_USED_IN_##__STATE:            \
2552         case LOCK_USED_IN_##__STATE##_READ:     \
2553         case LOCK_ENABLED_##__STATE:            \
2554         case LOCK_ENABLED_##__STATE##_READ:
2555 #include "lockdep_states.h"
2556 #undef LOCKDEP_STATE
2557                 ret = mark_lock_irq(curr, this, new_bit);
2558                 if (!ret)
2559                         return 0;
2560                 break;
2561         case LOCK_USED:
2562                 debug_atomic_dec(&nr_unused_locks);
2563                 break;
2564         default:
2565                 if (!debug_locks_off_graph_unlock())
2566                         return 0;
2567                 WARN_ON(1);
2568                 return 0;
2569         }
2570
2571         graph_unlock();
2572
2573         /*
2574          * We must printk outside of the graph_lock:
2575          */
2576         if (ret == 2) {
2577                 printk("\nmarked lock as {%s}:\n", usage_str[new_bit]);
2578                 print_lock(this);
2579                 print_irqtrace_events(curr);
2580                 dump_stack();
2581         }
2582
2583         return ret;
2584 }
2585
2586 /*
2587  * Initialize a lock instance's lock-class mapping info:
2588  */
2589 void lockdep_init_map(struct lockdep_map *lock, const char *name,
2590                       struct lock_class_key *key, int subclass)
2591 {
2592         lock->class_cache = NULL;
2593 #ifdef CONFIG_LOCK_STAT
2594         lock->cpu = raw_smp_processor_id();
2595 #endif
2596
2597         if (DEBUG_LOCKS_WARN_ON(!name)) {
2598                 lock->name = "NULL";
2599                 return;
2600         }
2601
2602         lock->name = name;
2603
2604         if (DEBUG_LOCKS_WARN_ON(!key))
2605                 return;
2606         /*
2607          * Sanity check, the lock-class key must be persistent:
2608          */
2609         if (!static_obj(key)) {
2610                 printk("BUG: key %p not in .data!\n", key);
2611                 DEBUG_LOCKS_WARN_ON(1);
2612                 return;
2613         }
2614         lock->key = key;
2615
2616         if (unlikely(!debug_locks))
2617                 return;
2618
2619         if (subclass)
2620                 register_lock_class(lock, subclass, 1);
2621 }
2622 EXPORT_SYMBOL_GPL(lockdep_init_map);
2623
2624 /*
2625  * This gets called for every mutex_lock*()/spin_lock*() operation.
2626  * We maintain the dependency maps and validate the locking attempt:
2627  */
2628 static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
2629                           int trylock, int read, int check, int hardirqs_off,
2630                           struct lockdep_map *nest_lock, unsigned long ip)
2631 {
2632         struct task_struct *curr = current;
2633         struct lock_class *class = NULL;
2634         struct held_lock *hlock;
2635         unsigned int depth, id;
2636         int chain_head = 0;
2637         u64 chain_key;
2638
2639         if (!prove_locking)
2640                 check = 1;
2641
2642         if (unlikely(!debug_locks))
2643                 return 0;
2644
2645         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2646                 return 0;
2647
2648         if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
2649                 debug_locks_off();
2650                 printk("BUG: MAX_LOCKDEP_SUBCLASSES too low!\n");
2651                 printk("turning off the locking correctness validator.\n");
2652                 dump_stack();
2653                 return 0;
2654         }
2655
2656         if (!subclass)
2657                 class = lock->class_cache;
2658         /*
2659          * Not cached yet or subclass?
2660          */
2661         if (unlikely(!class)) {
2662                 class = register_lock_class(lock, subclass, 0);
2663                 if (!class)
2664                         return 0;
2665         }
2666         debug_atomic_inc((atomic_t *)&class->ops);
2667         if (very_verbose(class)) {
2668                 printk("\nacquire class [%p] %s", class->key, class->name);
2669                 if (class->name_version > 1)
2670                         printk("#%d", class->name_version);
2671                 printk("\n");
2672                 dump_stack();
2673         }
2674
2675         /*
2676          * Add the lock to the list of currently held locks.
2677          * (we dont increase the depth just yet, up until the
2678          * dependency checks are done)
2679          */
2680         depth = curr->lockdep_depth;
2681         if (DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH))
2682                 return 0;
2683
2684         hlock = curr->held_locks + depth;
2685         if (DEBUG_LOCKS_WARN_ON(!class))
2686                 return 0;
2687         hlock->class_idx = class - lock_classes + 1;
2688         hlock->acquire_ip = ip;
2689         hlock->instance = lock;
2690         hlock->nest_lock = nest_lock;
2691         hlock->trylock = trylock;
2692         hlock->read = read;
2693         hlock->check = check;
2694         hlock->hardirqs_off = !!hardirqs_off;
2695 #ifdef CONFIG_LOCK_STAT
2696         hlock->waittime_stamp = 0;
2697         hlock->holdtime_stamp = sched_clock();
2698 #endif
2699
2700         if (check == 2 && !mark_irqflags(curr, hlock))
2701                 return 0;
2702
2703         /* mark it as used: */
2704         if (!mark_lock(curr, hlock, LOCK_USED))
2705                 return 0;
2706
2707         /*
2708          * Calculate the chain hash: it's the combined hash of all the
2709          * lock keys along the dependency chain. We save the hash value
2710          * at every step so that we can get the current hash easily
2711          * after unlock. The chain hash is then used to cache dependency
2712          * results.
2713          *
2714          * The 'key ID' is what is the most compact key value to drive
2715          * the hash, not class->key.
2716          */
2717         id = class - lock_classes;
2718         if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
2719                 return 0;
2720
2721         chain_key = curr->curr_chain_key;
2722         if (!depth) {
2723                 if (DEBUG_LOCKS_WARN_ON(chain_key != 0))
2724                         return 0;
2725                 chain_head = 1;
2726         }
2727
2728         hlock->prev_chain_key = chain_key;
2729         if (separate_irq_context(curr, hlock)) {
2730                 chain_key = 0;
2731                 chain_head = 1;
2732         }
2733         chain_key = iterate_chain_key(chain_key, id);
2734
2735         if (!validate_chain(curr, lock, hlock, chain_head, chain_key))
2736                 return 0;
2737
2738         curr->curr_chain_key = chain_key;
2739         curr->lockdep_depth++;
2740         check_chain_key(curr);
2741 #ifdef CONFIG_DEBUG_LOCKDEP
2742         if (unlikely(!debug_locks))
2743                 return 0;
2744 #endif
2745         if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
2746                 debug_locks_off();
2747                 printk("BUG: MAX_LOCK_DEPTH too low!\n");
2748                 printk("turning off the locking correctness validator.\n");
2749                 dump_stack();
2750                 return 0;
2751         }
2752
2753         if (unlikely(curr->lockdep_depth > max_lockdep_depth))
2754                 max_lockdep_depth = curr->lockdep_depth;
2755
2756         return 1;
2757 }
2758
2759 static int
2760 print_unlock_inbalance_bug(struct task_struct *curr, struct lockdep_map *lock,
2761                            unsigned long ip)
2762 {
2763         if (!debug_locks_off())
2764                 return 0;
2765         if (debug_locks_silent)
2766                 return 0;
2767
2768         printk("\n=====================================\n");
2769         printk(  "[ BUG: bad unlock balance detected! ]\n");
2770         printk(  "-------------------------------------\n");
2771         printk("%s/%d is trying to release lock (",
2772                 curr->comm, task_pid_nr(curr));
2773         print_lockdep_cache(lock);
2774         printk(") at:\n");
2775         print_ip_sym(ip);
2776         printk("but there are no more locks to release!\n");
2777         printk("\nother info that might help us debug this:\n");
2778         lockdep_print_held_locks(curr);
2779
2780         printk("\nstack backtrace:\n");
2781         dump_stack();
2782
2783         return 0;
2784 }
2785
2786 /*
2787  * Common debugging checks for both nested and non-nested unlock:
2788  */
2789 static int check_unlock(struct task_struct *curr, struct lockdep_map *lock,
2790                         unsigned long ip)
2791 {
2792         if (unlikely(!debug_locks))
2793                 return 0;
2794         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2795                 return 0;
2796
2797         if (curr->lockdep_depth <= 0)
2798                 return print_unlock_inbalance_bug(curr, lock, ip);
2799
2800         return 1;
2801 }
2802
2803 static int
2804 __lock_set_class(struct lockdep_map *lock, const char *name,
2805                  struct lock_class_key *key, unsigned int subclass,
2806                  unsigned long ip)
2807 {
2808         struct task_struct *curr = current;
2809         struct held_lock *hlock, *prev_hlock;
2810         struct lock_class *class;
2811         unsigned int depth;
2812         int i;
2813
2814         depth = curr->lockdep_depth;
2815         if (DEBUG_LOCKS_WARN_ON(!depth))
2816                 return 0;
2817
2818         prev_hlock = NULL;
2819         for (i = depth-1; i >= 0; i--) {
2820                 hlock = curr->held_locks + i;
2821                 /*
2822                  * We must not cross into another context:
2823                  */
2824                 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
2825                         break;
2826                 if (hlock->instance == lock)
2827                         goto found_it;
2828                 prev_hlock = hlock;
2829         }
2830         return print_unlock_inbalance_bug(curr, lock, ip);
2831
2832 found_it:
2833         lockdep_init_map(lock, name, key, 0);
2834         class = register_lock_class(lock, subclass, 0);
2835         hlock->class_idx = class - lock_classes + 1;
2836
2837         curr->lockdep_depth = i;
2838         curr->curr_chain_key = hlock->prev_chain_key;
2839
2840         for (; i < depth; i++) {
2841                 hlock = curr->held_locks + i;
2842                 if (!__lock_acquire(hlock->instance,
2843                         hlock_class(hlock)->subclass, hlock->trylock,
2844                                 hlock->read, hlock->check, hlock->hardirqs_off,
2845                                 hlock->nest_lock, hlock->acquire_ip))
2846                         return 0;
2847         }
2848
2849         if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth))
2850                 return 0;
2851         return 1;
2852 }
2853
2854 /*
2855  * Remove the lock to the list of currently held locks in a
2856  * potentially non-nested (out of order) manner. This is a
2857  * relatively rare operation, as all the unlock APIs default
2858  * to nested mode (which uses lock_release()):
2859  */
2860 static int
2861 lock_release_non_nested(struct task_struct *curr,
2862                         struct lockdep_map *lock, unsigned long ip)
2863 {
2864         struct held_lock *hlock, *prev_hlock;
2865         unsigned int depth;
2866         int i;
2867
2868         /*
2869          * Check whether the lock exists in the current stack
2870          * of held locks:
2871          */
2872         depth = curr->lockdep_depth;
2873         if (DEBUG_LOCKS_WARN_ON(!depth))
2874                 return 0;
2875
2876         prev_hlock = NULL;
2877         for (i = depth-1; i >= 0; i--) {
2878                 hlock = curr->held_locks + i;
2879                 /*
2880                  * We must not cross into another context:
2881                  */
2882                 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
2883                         break;
2884                 if (hlock->instance == lock)
2885                         goto found_it;
2886                 prev_hlock = hlock;
2887         }
2888         return print_unlock_inbalance_bug(curr, lock, ip);
2889
2890 found_it:
2891         lock_release_holdtime(hlock);
2892
2893         /*
2894          * We have the right lock to unlock, 'hlock' points to it.
2895          * Now we remove it from the stack, and add back the other
2896          * entries (if any), recalculating the hash along the way:
2897          */
2898         curr->lockdep_depth = i;
2899         curr->curr_chain_key = hlock->prev_chain_key;
2900
2901         for (i++; i < depth; i++) {
2902                 hlock = curr->held_locks + i;
2903                 if (!__lock_acquire(hlock->instance,
2904                         hlock_class(hlock)->subclass, hlock->trylock,
2905                                 hlock->read, hlock->check, hlock->hardirqs_off,
2906                                 hlock->nest_lock, hlock->acquire_ip))
2907                         return 0;
2908         }
2909
2910         if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - 1))
2911                 return 0;
2912         return 1;
2913 }
2914
2915 /*
2916  * Remove the lock to the list of currently held locks - this gets
2917  * called on mutex_unlock()/spin_unlock*() (or on a failed
2918  * mutex_lock_interruptible()). This is done for unlocks that nest
2919  * perfectly. (i.e. the current top of the lock-stack is unlocked)
2920  */
2921 static int lock_release_nested(struct task_struct *curr,
2922                                struct lockdep_map *lock, unsigned long ip)
2923 {
2924         struct held_lock *hlock;
2925         unsigned int depth;
2926
2927         /*
2928          * Pop off the top of the lock stack:
2929          */
2930         depth = curr->lockdep_depth - 1;
2931         hlock = curr->held_locks + depth;
2932
2933         /*
2934          * Is the unlock non-nested:
2935          */
2936         if (hlock->instance != lock)
2937                 return lock_release_non_nested(curr, lock, ip);
2938         curr->lockdep_depth--;
2939
2940         if (DEBUG_LOCKS_WARN_ON(!depth && (hlock->prev_chain_key != 0)))
2941                 return 0;
2942
2943         curr->curr_chain_key = hlock->prev_chain_key;
2944
2945         lock_release_holdtime(hlock);
2946
2947 #ifdef CONFIG_DEBUG_LOCKDEP
2948         hlock->prev_chain_key = 0;
2949         hlock->class_idx = 0;
2950         hlock->acquire_ip = 0;
2951         hlock->irq_context = 0;
2952 #endif
2953         return 1;
2954 }
2955
2956 /*
2957  * Remove the lock to the list of currently held locks - this gets
2958  * called on mutex_unlock()/spin_unlock*() (or on a failed
2959  * mutex_lock_interruptible()). This is done for unlocks that nest
2960  * perfectly. (i.e. the current top of the lock-stack is unlocked)
2961  */
2962 static void
2963 __lock_release(struct lockdep_map *lock, int nested, unsigned long ip)
2964 {
2965         struct task_struct *curr = current;
2966
2967         if (!check_unlock(curr, lock, ip))
2968                 return;
2969
2970         if (nested) {
2971                 if (!lock_release_nested(curr, lock, ip))
2972                         return;
2973         } else {
2974                 if (!lock_release_non_nested(curr, lock, ip))
2975                         return;
2976         }
2977
2978         check_chain_key(curr);
2979 }
2980
2981 /*
2982  * Check whether we follow the irq-flags state precisely:
2983  */
2984 static void check_flags(unsigned long flags)
2985 {
2986 #if defined(CONFIG_PROVE_LOCKING) && defined(CONFIG_DEBUG_LOCKDEP) && \
2987     defined(CONFIG_TRACE_IRQFLAGS)
2988         if (!debug_locks)
2989                 return;
2990
2991         if (irqs_disabled_flags(flags)) {
2992                 if (DEBUG_LOCKS_WARN_ON(current->hardirqs_enabled)) {
2993                         printk("possible reason: unannotated irqs-off.\n");
2994                 }
2995         } else {
2996                 if (DEBUG_LOCKS_WARN_ON(!current->hardirqs_enabled)) {
2997                         printk("possible reason: unannotated irqs-on.\n");
2998                 }
2999         }
3000
3001         /*
3002          * We dont accurately track softirq state in e.g.
3003          * hardirq contexts (such as on 4KSTACKS), so only
3004          * check if not in hardirq contexts:
3005          */
3006         if (!hardirq_count()) {
3007                 if (softirq_count())
3008                         DEBUG_LOCKS_WARN_ON(current->softirqs_enabled);
3009                 else
3010                         DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled);
3011         }
3012
3013         if (!debug_locks)
3014                 print_irqtrace_events(current);
3015 #endif
3016 }
3017
3018 void lock_set_class(struct lockdep_map *lock, const char *name,
3019                     struct lock_class_key *key, unsigned int subclass,
3020                     unsigned long ip)
3021 {
3022         unsigned long flags;
3023
3024         if (unlikely(current->lockdep_recursion))
3025                 return;
3026
3027         raw_local_irq_save(flags);
3028         current->lockdep_recursion = 1;
3029         check_flags(flags);
3030         if (__lock_set_class(lock, name, key, subclass, ip))
3031                 check_chain_key(current);
3032         current->lockdep_recursion = 0;
3033         raw_local_irq_restore(flags);
3034 }
3035 EXPORT_SYMBOL_GPL(lock_set_class);
3036
3037 /*
3038  * We are not always called with irqs disabled - do that here,
3039  * and also avoid lockdep recursion:
3040  */
3041 void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
3042                           int trylock, int read, int check,
3043                           struct lockdep_map *nest_lock, unsigned long ip)
3044 {
3045         unsigned long flags;
3046
3047         trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip);
3048
3049         if (unlikely(current->lockdep_recursion))
3050                 return;
3051
3052         raw_local_irq_save(flags);
3053         check_flags(flags);
3054
3055         current->lockdep_recursion = 1;
3056         __lock_acquire(lock, subclass, trylock, read, check,
3057                        irqs_disabled_flags(flags), nest_lock, ip);
3058         current->lockdep_recursion = 0;
3059         raw_local_irq_restore(flags);
3060 }
3061 EXPORT_SYMBOL_GPL(lock_acquire);
3062
3063 void lock_release(struct lockdep_map *lock, int nested,
3064                           unsigned long ip)
3065 {
3066         unsigned long flags;
3067
3068         trace_lock_release(lock, nested, ip);
3069
3070         if (unlikely(current->lockdep_recursion))
3071                 return;
3072
3073         raw_local_irq_save(flags);
3074         check_flags(flags);
3075         current->lockdep_recursion = 1;
3076         __lock_release(lock, nested, ip);
3077         current->lockdep_recursion = 0;
3078         raw_local_irq_restore(flags);
3079 }
3080 EXPORT_SYMBOL_GPL(lock_release);
3081
3082 void lockdep_set_current_reclaim_state(gfp_t gfp_mask)
3083 {
3084         current->lockdep_reclaim_gfp = gfp_mask;
3085 }
3086
3087 void lockdep_clear_current_reclaim_state(void)
3088 {
3089         current->lockdep_reclaim_gfp = 0;
3090 }
3091
3092 #ifdef CONFIG_LOCK_STAT
3093 static int
3094 print_lock_contention_bug(struct task_struct *curr, struct lockdep_map *lock,
3095                            unsigned long ip)
3096 {
3097         if (!debug_locks_off())
3098                 return 0;
3099         if (debug_locks_silent)
3100                 return 0;
3101
3102         printk("\n=================================\n");
3103         printk(  "[ BUG: bad contention detected! ]\n");
3104         printk(  "---------------------------------\n");
3105         printk("%s/%d is trying to contend lock (",
3106                 curr->comm, task_pid_nr(curr));
3107         print_lockdep_cache(lock);
3108         printk(") at:\n");
3109         print_ip_sym(ip);
3110         printk("but there are no locks held!\n");
3111         printk("\nother info that might help us debug this:\n");
3112         lockdep_print_held_locks(curr);
3113
3114         printk("\nstack backtrace:\n");
3115         dump_stack();
3116
3117         return 0;
3118 }
3119
3120 static void
3121 __lock_contended(struct lockdep_map *lock, unsigned long ip)
3122 {
3123         struct task_struct *curr = current;
3124         struct held_lock *hlock, *prev_hlock;
3125         struct lock_class_stats *stats;
3126         unsigned int depth;
3127         int i, contention_point, contending_point;
3128
3129         depth = curr->lockdep_depth;
3130         if (DEBUG_LOCKS_WARN_ON(!depth))
3131                 return;
3132
3133         prev_hlock = NULL;
3134         for (i = depth-1; i >= 0; i--) {
3135                 hlock = curr->held_locks + i;
3136                 /*
3137                  * We must not cross into another context:
3138                  */
3139                 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3140                         break;
3141                 if (hlock->instance == lock)
3142                         goto found_it;
3143                 prev_hlock = hlock;
3144         }
3145         print_lock_contention_bug(curr, lock, ip);
3146         return;
3147
3148 found_it:
3149         hlock->waittime_stamp = sched_clock();
3150
3151         contention_point = lock_point(hlock_class(hlock)->contention_point, ip);
3152         contending_point = lock_point(hlock_class(hlock)->contending_point,
3153                                       lock->ip);
3154
3155         stats = get_lock_stats(hlock_class(hlock));
3156         if (contention_point < LOCKSTAT_POINTS)
3157                 stats->contention_point[contention_point]++;
3158         if (contending_point < LOCKSTAT_POINTS)
3159                 stats->contending_point[contending_point]++;
3160         if (lock->cpu != smp_processor_id())
3161                 stats->bounces[bounce_contended + !!hlock->read]++;
3162         put_lock_stats(stats);
3163 }
3164
3165 static void
3166 __lock_acquired(struct lockdep_map *lock, unsigned long ip)
3167 {
3168         struct task_struct *curr = current;
3169         struct held_lock *hlock, *prev_hlock;
3170         struct lock_class_stats *stats;
3171         unsigned int depth;
3172         u64 now;
3173         s64 waittime = 0;
3174         int i, cpu;
3175
3176         depth = curr->lockdep_depth;
3177         if (DEBUG_LOCKS_WARN_ON(!depth))
3178                 return;
3179
3180         prev_hlock = NULL;
3181         for (i = depth-1; i >= 0; i--) {
3182                 hlock = curr->held_locks + i;
3183                 /*
3184                  * We must not cross into another context:
3185                  */
3186                 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3187                         break;
3188                 if (hlock->instance == lock)
3189                         goto found_it;
3190                 prev_hlock = hlock;
3191         }
3192         print_lock_contention_bug(curr, lock, _RET_IP_);
3193         return;
3194
3195 found_it:
3196         cpu = smp_processor_id();
3197         if (hlock->waittime_stamp) {
3198                 now = sched_clock();
3199                 waittime = now - hlock->waittime_stamp;
3200                 hlock->holdtime_stamp = now;
3201         }
3202
3203         trace_lock_acquired(lock, ip, waittime);
3204
3205         stats = get_lock_stats(hlock_class(hlock));
3206         if (waittime) {
3207                 if (hlock->read)
3208                         lock_time_inc(&stats->read_waittime, waittime);
3209                 else
3210                         lock_time_inc(&stats->write_waittime, waittime);
3211         }
3212         if (lock->cpu != cpu)
3213                 stats->bounces[bounce_acquired + !!hlock->read]++;
3214         put_lock_stats(stats);
3215
3216         lock->cpu = cpu;
3217         lock->ip = ip;
3218 }
3219
3220 void lock_contended(struct lockdep_map *lock, unsigned long ip)
3221 {
3222         unsigned long flags;
3223
3224         trace_lock_contended(lock, ip);
3225
3226         if (unlikely(!lock_stat))
3227                 return;
3228
3229         if (unlikely(current->lockdep_recursion))
3230                 return;
3231
3232         raw_local_irq_save(flags);
3233         check_flags(flags);
3234         current->lockdep_recursion = 1;
3235         __lock_contended(lock, ip);
3236         current->lockdep_recursion = 0;
3237         raw_local_irq_restore(flags);
3238 }
3239 EXPORT_SYMBOL_GPL(lock_contended);
3240
3241 void lock_acquired(struct lockdep_map *lock, unsigned long ip)
3242 {
3243         unsigned long flags;
3244
3245         if (unlikely(!lock_stat))
3246                 return;
3247
3248         if (unlikely(current->lockdep_recursion))
3249                 return;
3250
3251         raw_local_irq_save(flags);
3252         check_flags(flags);
3253         current->lockdep_recursion = 1;
3254         __lock_acquired(lock, ip);
3255         current->lockdep_recursion = 0;
3256         raw_local_irq_restore(flags);
3257 }
3258 EXPORT_SYMBOL_GPL(lock_acquired);
3259 #endif
3260
3261 /*
3262  * Used by the testsuite, sanitize the validator state
3263  * after a simulated failure:
3264  */
3265
3266 void lockdep_reset(void)
3267 {
3268         unsigned long flags;
3269         int i;
3270
3271         raw_local_irq_save(flags);
3272         current->curr_chain_key = 0;
3273         current->lockdep_depth = 0;
3274         current->lockdep_recursion = 0;
3275         memset(current->held_locks, 0, MAX_LOCK_DEPTH*sizeof(struct held_lock));
3276         nr_hardirq_chains = 0;
3277         nr_softirq_chains = 0;
3278         nr_process_chains = 0;
3279         debug_locks = 1;
3280         for (i = 0; i < CHAINHASH_SIZE; i++)
3281                 INIT_LIST_HEAD(chainhash_table + i);
3282         raw_local_irq_restore(flags);
3283 }
3284
3285 static void zap_class(struct lock_class *class)
3286 {
3287         int i;
3288
3289         /*
3290          * Remove all dependencies this lock is
3291          * involved in:
3292          */
3293         for (i = 0; i < nr_list_entries; i++) {
3294                 if (list_entries[i].class == class)
3295                         list_del_rcu(&list_entries[i].entry);
3296         }
3297         /*
3298          * Unhash the class and remove it from the all_lock_classes list:
3299          */
3300         list_del_rcu(&class->hash_entry);
3301         list_del_rcu(&class->lock_entry);
3302
3303         class->key = NULL;
3304 }
3305
3306 static inline int within(const void *addr, void *start, unsigned long size)
3307 {
3308         return addr >= start && addr < start + size;
3309 }
3310
3311 void lockdep_free_key_range(void *start, unsigned long size)
3312 {
3313         struct lock_class *class, *next;
3314         struct list_head *head;
3315         unsigned long flags;
3316         int i;
3317         int locked;
3318
3319         raw_local_irq_save(flags);
3320         locked = graph_lock();
3321
3322         /*
3323          * Unhash all classes that were created by this module:
3324          */
3325         for (i = 0; i < CLASSHASH_SIZE; i++) {
3326                 head = classhash_table + i;
3327                 if (list_empty(head))
3328                         continue;
3329                 list_for_each_entry_safe(class, next, head, hash_entry) {
3330                         if (within(class->key, start, size))
3331                                 zap_class(class);
3332                         else if (within(class->name, start, size))
3333                                 zap_class(class);
3334                 }
3335         }
3336
3337         if (locked)
3338                 graph_unlock();
3339         raw_local_irq_restore(flags);
3340 }
3341
3342 void lockdep_reset_lock(struct lockdep_map *lock)
3343 {
3344         struct lock_class *class, *next;
3345         struct list_head *head;
3346         unsigned long flags;
3347         int i, j;
3348         int locked;
3349
3350         raw_local_irq_save(flags);
3351
3352         /*
3353          * Remove all classes this lock might have:
3354          */
3355         for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) {
3356                 /*
3357                  * If the class exists we look it up and zap it:
3358                  */
3359                 class = look_up_lock_class(lock, j);
3360                 if (class)
3361                         zap_class(class);
3362         }
3363         /*
3364          * Debug check: in the end all mapped classes should
3365          * be gone.
3366          */
3367         locked = graph_lock();
3368         for (i = 0; i < CLASSHASH_SIZE; i++) {
3369                 head = classhash_table + i;
3370                 if (list_empty(head))
3371                         continue;
3372                 list_for_each_entry_safe(class, next, head, hash_entry) {
3373                         if (unlikely(class == lock->class_cache)) {
3374                                 if (debug_locks_off_graph_unlock())
3375                                         WARN_ON(1);
3376                                 goto out_restore;
3377                         }
3378                 }
3379         }
3380         if (locked)
3381                 graph_unlock();
3382
3383 out_restore:
3384         raw_local_irq_restore(flags);
3385 }
3386
3387 void lockdep_init(void)
3388 {
3389         int i;
3390
3391         /*
3392          * Some architectures have their own start_kernel()
3393          * code which calls lockdep_init(), while we also
3394          * call lockdep_init() from the start_kernel() itself,
3395          * and we want to initialize the hashes only once:
3396          */
3397         if (lockdep_initialized)
3398                 return;
3399
3400         for (i = 0; i < CLASSHASH_SIZE; i++)
3401                 INIT_LIST_HEAD(classhash_table + i);
3402
3403         for (i = 0; i < CHAINHASH_SIZE; i++)
3404                 INIT_LIST_HEAD(chainhash_table + i);
3405
3406         lockdep_initialized = 1;
3407 }
3408
3409 void __init lockdep_info(void)
3410 {
3411         printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");
3412
3413         printk("... MAX_LOCKDEP_SUBCLASSES:  %lu\n", MAX_LOCKDEP_SUBCLASSES);
3414         printk("... MAX_LOCK_DEPTH:          %lu\n", MAX_LOCK_DEPTH);
3415         printk("... MAX_LOCKDEP_KEYS:        %lu\n", MAX_LOCKDEP_KEYS);
3416         printk("... CLASSHASH_SIZE:          %lu\n", CLASSHASH_SIZE);
3417         printk("... MAX_LOCKDEP_ENTRIES:     %lu\n", MAX_LOCKDEP_ENTRIES);
3418         printk("... MAX_LOCKDEP_CHAINS:      %lu\n", MAX_LOCKDEP_CHAINS);
3419         printk("... CHAINHASH_SIZE:          %lu\n", CHAINHASH_SIZE);
3420
3421         printk(" memory used by lock dependency info: %lu kB\n",
3422                 (sizeof(struct lock_class) * MAX_LOCKDEP_KEYS +
3423                 sizeof(struct list_head) * CLASSHASH_SIZE +
3424                 sizeof(struct lock_list) * MAX_LOCKDEP_ENTRIES +
3425                 sizeof(struct lock_chain) * MAX_LOCKDEP_CHAINS +
3426                 sizeof(struct list_head) * CHAINHASH_SIZE) / 1024);
3427
3428         printk(" per task-struct memory footprint: %lu bytes\n",
3429                 sizeof(struct held_lock) * MAX_LOCK_DEPTH);
3430
3431 #ifdef CONFIG_DEBUG_LOCKDEP
3432         if (lockdep_init_error) {
3433                 printk("WARNING: lockdep init error! Arch code didn't call lockdep_init() early enough?\n");
3434                 printk("Call stack leading to lockdep invocation was:\n");
3435                 print_stack_trace(&lockdep_init_trace, 0);
3436         }
3437 #endif
3438 }
3439
3440 static void
3441 print_freed_lock_bug(struct task_struct *curr, const void *mem_from,
3442                      const void *mem_to, struct held_lock *hlock)
3443 {
3444         if (!debug_locks_off())
3445                 return;
3446         if (debug_locks_silent)
3447                 return;
3448
3449         printk("\n=========================\n");
3450         printk(  "[ BUG: held lock freed! ]\n");
3451         printk(  "-------------------------\n");
3452         printk("%s/%d is freeing memory %p-%p, with a lock still held there!\n",
3453                 curr->comm, task_pid_nr(curr), mem_from, mem_to-1);
3454         print_lock(hlock);
3455         lockdep_print_held_locks(curr);
3456
3457         printk("\nstack backtrace:\n");
3458         dump_stack();
3459 }
3460
3461 static inline int not_in_range(const void* mem_from, unsigned long mem_len,
3462                                 const void* lock_from, unsigned long lock_len)
3463 {
3464         return lock_from + lock_len <= mem_from ||
3465                 mem_from + mem_len <= lock_from;
3466 }
3467
3468 /*
3469  * Called when kernel memory is freed (or unmapped), or if a lock
3470  * is destroyed or reinitialized - this code checks whether there is
3471  * any held lock in the memory range of <from> to <to>:
3472  */
3473 void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len)
3474 {
3475         struct task_struct *curr = current;
3476         struct held_lock *hlock;
3477         unsigned long flags;
3478         int i;
3479
3480         if (unlikely(!debug_locks))
3481                 return;
3482
3483         local_irq_save(flags);
3484         for (i = 0; i < curr->lockdep_depth; i++) {
3485                 hlock = curr->held_locks + i;
3486
3487                 if (not_in_range(mem_from, mem_len, hlock->instance,
3488                                         sizeof(*hlock->instance)))
3489                         continue;
3490
3491                 print_freed_lock_bug(curr, mem_from, mem_from + mem_len, hlock);
3492                 break;
3493         }
3494         local_irq_restore(flags);
3495 }
3496 EXPORT_SYMBOL_GPL(debug_check_no_locks_freed);
3497
3498 static void print_held_locks_bug(struct task_struct *curr)
3499 {
3500         if (!debug_locks_off())
3501                 return;
3502         if (debug_locks_silent)
3503                 return;
3504
3505         printk("\n=====================================\n");
3506         printk(  "[ BUG: lock held at task exit time! ]\n");
3507         printk(  "-------------------------------------\n");
3508         printk("%s/%d is exiting with locks still held!\n",
3509                 curr->comm, task_pid_nr(curr));
3510         lockdep_print_held_locks(curr);
3511
3512         printk("\nstack backtrace:\n");
3513         dump_stack();
3514 }
3515
3516 void debug_check_no_locks_held(struct task_struct *task)
3517 {
3518         if (unlikely(task->lockdep_depth > 0))
3519                 print_held_locks_bug(task);
3520 }
3521
3522 void debug_show_all_locks(void)
3523 {
3524         struct task_struct *g, *p;
3525         int count = 10;
3526         int unlock = 1;
3527
3528         if (unlikely(!debug_locks)) {
3529                 printk("INFO: lockdep is turned off.\n");
3530                 return;
3531         }
3532         printk("\nShowing all locks held in the system:\n");
3533
3534         /*
3535          * Here we try to get the tasklist_lock as hard as possible,
3536          * if not successful after 2 seconds we ignore it (but keep
3537          * trying). This is to enable a debug printout even if a
3538          * tasklist_lock-holding task deadlocks or crashes.
3539          */
3540 retry:
3541         if (!read_trylock(&tasklist_lock)) {
3542                 if (count == 10)
3543                         printk("hm, tasklist_lock locked, retrying... ");
3544                 if (count) {
3545                         count--;
3546                         printk(" #%d", 10-count);
3547                         mdelay(200);
3548                         goto retry;
3549                 }
3550                 printk(" ignoring it.\n");
3551                 unlock = 0;
3552         } else {
3553                 if (count != 10)
3554                         printk(KERN_CONT " locked it.\n");
3555         }
3556
3557         do_each_thread(g, p) {
3558                 /*
3559                  * It's not reliable to print a task's held locks
3560                  * if it's not sleeping (or if it's not the current
3561                  * task):
3562                  */
3563                 if (p->state == TASK_RUNNING && p != current)
3564                         continue;
3565                 if (p->lockdep_depth)
3566                         lockdep_print_held_locks(p);
3567                 if (!unlock)
3568                         if (read_trylock(&tasklist_lock))
3569                                 unlock = 1;
3570         } while_each_thread(g, p);
3571
3572         printk("\n");
3573         printk("=============================================\n\n");
3574
3575         if (unlock)
3576                 read_unlock(&tasklist_lock);
3577 }
3578 EXPORT_SYMBOL_GPL(debug_show_all_locks);
3579
3580 /*
3581  * Careful: only use this function if you are sure that
3582  * the task cannot run in parallel!
3583  */
3584 void __debug_show_held_locks(struct task_struct *task)
3585 {
3586         if (unlikely(!debug_locks)) {
3587                 printk("INFO: lockdep is turned off.\n");
3588                 return;
3589         }
3590         lockdep_print_held_locks(task);
3591 }
3592 EXPORT_SYMBOL_GPL(__debug_show_held_locks);
3593
3594 void debug_show_held_locks(struct task_struct *task)
3595 {
3596                 __debug_show_held_locks(task);
3597 }
3598 EXPORT_SYMBOL_GPL(debug_show_held_locks);
3599
3600 void lockdep_sys_exit(void)
3601 {
3602         struct task_struct *curr = current;
3603
3604         if (unlikely(curr->lockdep_depth)) {
3605                 if (!debug_locks_off())
3606                         return;
3607                 printk("\n================================================\n");
3608                 printk(  "[ BUG: lock held when returning to user space! ]\n");
3609                 printk(  "------------------------------------------------\n");
3610                 printk("%s/%d is leaving the kernel with locks still held!\n",
3611                                 curr->comm, curr->pid);
3612                 lockdep_print_held_locks(curr);
3613         }
3614 }