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