lockdep: change a held lock's class
[linux-2.6.git] / kernel / lockdep.c
1 /*
2  * kernel/lockdep.c
3  *
4  * Runtime locking correctness validator
5  *
6  * Started by Ingo Molnar:
7  *
8  *  Copyright (C) 2006,2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
9  *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
10  *
11  * this code maps all the lock dependencies as they occur in a live kernel
12  * and will warn about the following classes of locking bugs:
13  *
14  * - lock inversion scenarios
15  * - circular lock dependencies
16  * - hardirq/softirq safe/unsafe locking bugs
17  *
18  * Bugs are reported even if the current locking scenario does not cause
19  * any deadlock at this point.
20  *
21  * I.e. if anytime in the past two locks were taken in a different order,
22  * even if it happened for another task, even if those were different
23  * locks (but of the same class as this lock), this code will detect it.
24  *
25  * Thanks to Arjan van de Ven for coming up with the initial idea of
26  * mapping lock dependencies runtime.
27  */
28 #include <linux/mutex.h>
29 #include <linux/sched.h>
30 #include <linux/delay.h>
31 #include <linux/module.h>
32 #include <linux/proc_fs.h>
33 #include <linux/seq_file.h>
34 #include <linux/spinlock.h>
35 #include <linux/kallsyms.h>
36 #include <linux/interrupt.h>
37 #include <linux/stacktrace.h>
38 #include <linux/debug_locks.h>
39 #include <linux/irqflags.h>
40 #include <linux/utsname.h>
41 #include <linux/hash.h>
42 #include <linux/ftrace.h>
43
44 #include <asm/sections.h>
45
46 #include "lockdep_internals.h"
47
48 #ifdef CONFIG_PROVE_LOCKING
49 int prove_locking = 1;
50 module_param(prove_locking, int, 0644);
51 #else
52 #define prove_locking 0
53 #endif
54
55 #ifdef CONFIG_LOCK_STAT
56 int lock_stat = 1;
57 module_param(lock_stat, int, 0644);
58 #else
59 #define lock_stat 0
60 #endif
61
62 /*
63  * lockdep_lock: protects the lockdep graph, the hashes and the
64  *               class/list/hash allocators.
65  *
66  * This is one of the rare exceptions where it's justified
67  * to use a raw spinlock - we really dont want the spinlock
68  * code to recurse back into the lockdep code...
69  */
70 static raw_spinlock_t lockdep_lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
71
72 static int graph_lock(void)
73 {
74         __raw_spin_lock(&lockdep_lock);
75         /*
76          * Make sure that if another CPU detected a bug while
77          * walking the graph we dont change it (while the other
78          * CPU is busy printing out stuff with the graph lock
79          * dropped already)
80          */
81         if (!debug_locks) {
82                 __raw_spin_unlock(&lockdep_lock);
83                 return 0;
84         }
85         /* prevent any recursions within lockdep from causing deadlocks */
86         current->lockdep_recursion++;
87         return 1;
88 }
89
90 static inline int graph_unlock(void)
91 {
92         if (debug_locks && !__raw_spin_is_locked(&lockdep_lock))
93                 return DEBUG_LOCKS_WARN_ON(1);
94
95         current->lockdep_recursion--;
96         __raw_spin_unlock(&lockdep_lock);
97         return 0;
98 }
99
100 /*
101  * Turn lock debugging off and return with 0 if it was off already,
102  * and also release the graph lock:
103  */
104 static inline int debug_locks_off_graph_unlock(void)
105 {
106         int ret = debug_locks_off();
107
108         __raw_spin_unlock(&lockdep_lock);
109
110         return ret;
111 }
112
113 static int lockdep_initialized;
114
115 unsigned long nr_list_entries;
116 static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES];
117
118 /*
119  * All data structures here are protected by the global debug_lock.
120  *
121  * Mutex key structs only get allocated, once during bootup, and never
122  * get freed - this significantly simplifies the debugging code.
123  */
124 unsigned long nr_lock_classes;
125 static struct lock_class lock_classes[MAX_LOCKDEP_KEYS];
126
127 static inline struct lock_class *hlock_class(struct held_lock *hlock)
128 {
129         if (!hlock->class_idx) {
130                 DEBUG_LOCKS_WARN_ON(1);
131                 return NULL;
132         }
133         return lock_classes + hlock->class_idx - 1;
134 }
135
136 #ifdef CONFIG_LOCK_STAT
137 static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS], lock_stats);
138
139 static int lock_point(unsigned long points[], unsigned long ip)
140 {
141         int i;
142
143         for (i = 0; i < LOCKSTAT_POINTS; i++) {
144                 if (points[i] == 0) {
145                         points[i] = ip;
146                         break;
147                 }
148                 if (points[i] == ip)
149                         break;
150         }
151
152         return i;
153 }
154
155 static void lock_time_inc(struct lock_time *lt, s64 time)
156 {
157         if (time > lt->max)
158                 lt->max = time;
159
160         if (time < lt->min || !lt->min)
161                 lt->min = time;
162
163         lt->total += time;
164         lt->nr++;
165 }
166
167 static inline void lock_time_add(struct lock_time *src, struct lock_time *dst)
168 {
169         dst->min += src->min;
170         dst->max += src->max;
171         dst->total += src->total;
172         dst->nr += src->nr;
173 }
174
175 struct lock_class_stats lock_stats(struct lock_class *class)
176 {
177         struct lock_class_stats stats;
178         int cpu, i;
179
180         memset(&stats, 0, sizeof(struct lock_class_stats));
181         for_each_possible_cpu(cpu) {
182                 struct lock_class_stats *pcs =
183                         &per_cpu(lock_stats, cpu)[class - lock_classes];
184
185                 for (i = 0; i < ARRAY_SIZE(stats.contention_point); i++)
186                         stats.contention_point[i] += pcs->contention_point[i];
187
188                 for (i = 0; i < ARRAY_SIZE(stats.contending_point); i++)
189                         stats.contending_point[i] += pcs->contending_point[i];
190
191                 lock_time_add(&pcs->read_waittime, &stats.read_waittime);
192                 lock_time_add(&pcs->write_waittime, &stats.write_waittime);
193
194                 lock_time_add(&pcs->read_holdtime, &stats.read_holdtime);
195                 lock_time_add(&pcs->write_holdtime, &stats.write_holdtime);
196
197                 for (i = 0; i < ARRAY_SIZE(stats.bounces); i++)
198                         stats.bounces[i] += pcs->bounces[i];
199         }
200
201         return stats;
202 }
203
204 void clear_lock_stats(struct lock_class *class)
205 {
206         int cpu;
207
208         for_each_possible_cpu(cpu) {
209                 struct lock_class_stats *cpu_stats =
210                         &per_cpu(lock_stats, cpu)[class - lock_classes];
211
212                 memset(cpu_stats, 0, sizeof(struct lock_class_stats));
213         }
214         memset(class->contention_point, 0, sizeof(class->contention_point));
215         memset(class->contending_point, 0, sizeof(class->contending_point));
216 }
217
218 static struct lock_class_stats *get_lock_stats(struct lock_class *class)
219 {
220         return &get_cpu_var(lock_stats)[class - lock_classes];
221 }
222
223 static void put_lock_stats(struct lock_class_stats *stats)
224 {
225         put_cpu_var(lock_stats);
226 }
227
228 static void lock_release_holdtime(struct held_lock *hlock)
229 {
230         struct lock_class_stats *stats;
231         s64 holdtime;
232
233         if (!lock_stat)
234                 return;
235
236         holdtime = sched_clock() - hlock->holdtime_stamp;
237
238         stats = get_lock_stats(hlock_class(hlock));
239         if (hlock->read)
240                 lock_time_inc(&stats->read_holdtime, holdtime);
241         else
242                 lock_time_inc(&stats->write_holdtime, holdtime);
243         put_lock_stats(stats);
244 }
245 #else
246 static inline void lock_release_holdtime(struct held_lock *hlock)
247 {
248 }
249 #endif
250
251 /*
252  * We keep a global list of all lock classes. The list only grows,
253  * never shrinks. The list is only accessed with the lockdep
254  * spinlock lock held.
255  */
256 LIST_HEAD(all_lock_classes);
257
258 /*
259  * The lockdep classes are in a hash-table as well, for fast lookup:
260  */
261 #define CLASSHASH_BITS          (MAX_LOCKDEP_KEYS_BITS - 1)
262 #define CLASSHASH_SIZE          (1UL << CLASSHASH_BITS)
263 #define __classhashfn(key)      hash_long((unsigned long)key, CLASSHASH_BITS)
264 #define classhashentry(key)     (classhash_table + __classhashfn((key)))
265
266 static struct list_head classhash_table[CLASSHASH_SIZE];
267
268 /*
269  * We put the lock dependency chains into a hash-table as well, to cache
270  * their existence:
271  */
272 #define CHAINHASH_BITS          (MAX_LOCKDEP_CHAINS_BITS-1)
273 #define CHAINHASH_SIZE          (1UL << CHAINHASH_BITS)
274 #define __chainhashfn(chain)    hash_long(chain, CHAINHASH_BITS)
275 #define chainhashentry(chain)   (chainhash_table + __chainhashfn((chain)))
276
277 static struct list_head chainhash_table[CHAINHASH_SIZE];
278
279 /*
280  * The hash key of the lock dependency chains is a hash itself too:
281  * it's a hash of all locks taken up to that lock, including that lock.
282  * It's a 64-bit hash, because it's important for the keys to be
283  * unique.
284  */
285 #define iterate_chain_key(key1, key2) \
286         (((key1) << MAX_LOCKDEP_KEYS_BITS) ^ \
287         ((key1) >> (64-MAX_LOCKDEP_KEYS_BITS)) ^ \
288         (key2))
289
290 void lockdep_off(void)
291 {
292         current->lockdep_recursion++;
293 }
294 EXPORT_SYMBOL(lockdep_off);
295
296 void lockdep_on(void)
297 {
298         current->lockdep_recursion--;
299 }
300 EXPORT_SYMBOL(lockdep_on);
301
302 /*
303  * Debugging switches:
304  */
305
306 #define VERBOSE                 0
307 #define VERY_VERBOSE            0
308
309 #if VERBOSE
310 # define HARDIRQ_VERBOSE        1
311 # define SOFTIRQ_VERBOSE        1
312 #else
313 # define HARDIRQ_VERBOSE        0
314 # define SOFTIRQ_VERBOSE        0
315 #endif
316
317 #if VERBOSE || HARDIRQ_VERBOSE || SOFTIRQ_VERBOSE
318 /*
319  * Quick filtering for interesting events:
320  */
321 static int class_filter(struct lock_class *class)
322 {
323 #if 0
324         /* Example */
325         if (class->name_version == 1 &&
326                         !strcmp(class->name, "lockname"))
327                 return 1;
328         if (class->name_version == 1 &&
329                         !strcmp(class->name, "&struct->lockfield"))
330                 return 1;
331 #endif
332         /* Filter everything else. 1 would be to allow everything else */
333         return 0;
334 }
335 #endif
336
337 static int verbose(struct lock_class *class)
338 {
339 #if VERBOSE
340         return class_filter(class);
341 #endif
342         return 0;
343 }
344
345 /*
346  * Stack-trace: tightly packed array of stack backtrace
347  * addresses. Protected by the graph_lock.
348  */
349 unsigned long nr_stack_trace_entries;
350 static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];
351
352 static int save_trace(struct stack_trace *trace)
353 {
354         trace->nr_entries = 0;
355         trace->max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries;
356         trace->entries = stack_trace + nr_stack_trace_entries;
357
358         trace->skip = 3;
359
360         save_stack_trace(trace);
361
362         trace->max_entries = trace->nr_entries;
363
364         nr_stack_trace_entries += trace->nr_entries;
365
366         if (nr_stack_trace_entries == MAX_STACK_TRACE_ENTRIES) {
367                 if (!debug_locks_off_graph_unlock())
368                         return 0;
369
370                 printk("BUG: MAX_STACK_TRACE_ENTRIES too low!\n");
371                 printk("turning off the locking correctness validator.\n");
372                 dump_stack();
373
374                 return 0;
375         }
376
377         return 1;
378 }
379
380 unsigned int nr_hardirq_chains;
381 unsigned int nr_softirq_chains;
382 unsigned int nr_process_chains;
383 unsigned int max_lockdep_depth;
384 unsigned int max_recursion_depth;
385
386 static unsigned int lockdep_dependency_gen_id;
387
388 static bool lockdep_dependency_visit(struct lock_class *source,
389                                      unsigned int depth)
390 {
391         if (!depth)
392                 lockdep_dependency_gen_id++;
393         if (source->dep_gen_id == lockdep_dependency_gen_id)
394                 return true;
395         source->dep_gen_id = lockdep_dependency_gen_id;
396         return false;
397 }
398
399 #ifdef CONFIG_DEBUG_LOCKDEP
400 /*
401  * We cannot printk in early bootup code. Not even early_printk()
402  * might work. So we mark any initialization errors and printk
403  * about it later on, in lockdep_info().
404  */
405 static int lockdep_init_error;
406 static unsigned long lockdep_init_trace_data[20];
407 static struct stack_trace lockdep_init_trace = {
408         .max_entries = ARRAY_SIZE(lockdep_init_trace_data),
409         .entries = lockdep_init_trace_data,
410 };
411
412 /*
413  * Various lockdep statistics:
414  */
415 atomic_t chain_lookup_hits;
416 atomic_t chain_lookup_misses;
417 atomic_t hardirqs_on_events;
418 atomic_t hardirqs_off_events;
419 atomic_t redundant_hardirqs_on;
420 atomic_t redundant_hardirqs_off;
421 atomic_t softirqs_on_events;
422 atomic_t softirqs_off_events;
423 atomic_t redundant_softirqs_on;
424 atomic_t redundant_softirqs_off;
425 atomic_t nr_unused_locks;
426 atomic_t nr_cyclic_checks;
427 atomic_t nr_cyclic_check_recursions;
428 atomic_t nr_find_usage_forwards_checks;
429 atomic_t nr_find_usage_forwards_recursions;
430 atomic_t nr_find_usage_backwards_checks;
431 atomic_t nr_find_usage_backwards_recursions;
432 # define debug_atomic_inc(ptr)          atomic_inc(ptr)
433 # define debug_atomic_dec(ptr)          atomic_dec(ptr)
434 # define debug_atomic_read(ptr)         atomic_read(ptr)
435 #else
436 # define debug_atomic_inc(ptr)          do { } while (0)
437 # define debug_atomic_dec(ptr)          do { } while (0)
438 # define debug_atomic_read(ptr)         0
439 #endif
440
441 /*
442  * Locking printouts:
443  */
444
445 static const char *usage_str[] =
446 {
447         [LOCK_USED] =                   "initial-use ",
448         [LOCK_USED_IN_HARDIRQ] =        "in-hardirq-W",
449         [LOCK_USED_IN_SOFTIRQ] =        "in-softirq-W",
450         [LOCK_ENABLED_SOFTIRQS] =       "softirq-on-W",
451         [LOCK_ENABLED_HARDIRQS] =       "hardirq-on-W",
452         [LOCK_USED_IN_HARDIRQ_READ] =   "in-hardirq-R",
453         [LOCK_USED_IN_SOFTIRQ_READ] =   "in-softirq-R",
454         [LOCK_ENABLED_SOFTIRQS_READ] =  "softirq-on-R",
455         [LOCK_ENABLED_HARDIRQS_READ] =  "hardirq-on-R",
456 };
457
458 const char * __get_key_name(struct lockdep_subclass_key *key, char *str)
459 {
460         return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str);
461 }
462
463 void
464 get_usage_chars(struct lock_class *class, char *c1, char *c2, char *c3, char *c4)
465 {
466         *c1 = '.', *c2 = '.', *c3 = '.', *c4 = '.';
467
468         if (class->usage_mask & LOCKF_USED_IN_HARDIRQ)
469                 *c1 = '+';
470         else
471                 if (class->usage_mask & LOCKF_ENABLED_HARDIRQS)
472                         *c1 = '-';
473
474         if (class->usage_mask & LOCKF_USED_IN_SOFTIRQ)
475                 *c2 = '+';
476         else
477                 if (class->usage_mask & LOCKF_ENABLED_SOFTIRQS)
478                         *c2 = '-';
479
480         if (class->usage_mask & LOCKF_ENABLED_HARDIRQS_READ)
481                 *c3 = '-';
482         if (class->usage_mask & LOCKF_USED_IN_HARDIRQ_READ) {
483                 *c3 = '+';
484                 if (class->usage_mask & LOCKF_ENABLED_HARDIRQS_READ)
485                         *c3 = '?';
486         }
487
488         if (class->usage_mask & LOCKF_ENABLED_SOFTIRQS_READ)
489                 *c4 = '-';
490         if (class->usage_mask & LOCKF_USED_IN_SOFTIRQ_READ) {
491                 *c4 = '+';
492                 if (class->usage_mask & LOCKF_ENABLED_SOFTIRQS_READ)
493                         *c4 = '?';
494         }
495 }
496
497 static void print_lock_name(struct lock_class *class)
498 {
499         char str[KSYM_NAME_LEN], c1, c2, c3, c4;
500         const char *name;
501
502         get_usage_chars(class, &c1, &c2, &c3, &c4);
503
504         name = class->name;
505         if (!name) {
506                 name = __get_key_name(class->key, str);
507                 printk(" (%s", name);
508         } else {
509                 printk(" (%s", name);
510                 if (class->name_version > 1)
511                         printk("#%d", class->name_version);
512                 if (class->subclass)
513                         printk("/%d", class->subclass);
514         }
515         printk("){%c%c%c%c}", c1, c2, c3, c4);
516 }
517
518 static void print_lockdep_cache(struct lockdep_map *lock)
519 {
520         const char *name;
521         char str[KSYM_NAME_LEN];
522
523         name = lock->name;
524         if (!name)
525                 name = __get_key_name(lock->key->subkeys, str);
526
527         printk("%s", name);
528 }
529
530 static void print_lock(struct held_lock *hlock)
531 {
532         print_lock_name(hlock_class(hlock));
533         printk(", at: ");
534         print_ip_sym(hlock->acquire_ip);
535 }
536
537 static void lockdep_print_held_locks(struct task_struct *curr)
538 {
539         int i, depth = curr->lockdep_depth;
540
541         if (!depth) {
542                 printk("no locks held by %s/%d.\n", curr->comm, task_pid_nr(curr));
543                 return;
544         }
545         printk("%d lock%s held by %s/%d:\n",
546                 depth, depth > 1 ? "s" : "", curr->comm, task_pid_nr(curr));
547
548         for (i = 0; i < depth; i++) {
549                 printk(" #%d: ", i);
550                 print_lock(curr->held_locks + i);
551         }
552 }
553
554 static void print_lock_class_header(struct lock_class *class, int depth)
555 {
556         int bit;
557
558         printk("%*s->", depth, "");
559         print_lock_name(class);
560         printk(" ops: %lu", class->ops);
561         printk(" {\n");
562
563         for (bit = 0; bit < LOCK_USAGE_STATES; bit++) {
564                 if (class->usage_mask & (1 << bit)) {
565                         int len = depth;
566
567                         len += printk("%*s   %s", depth, "", usage_str[bit]);
568                         len += printk(" at:\n");
569                         print_stack_trace(class->usage_traces + bit, len);
570                 }
571         }
572         printk("%*s }\n", depth, "");
573
574         printk("%*s ... key      at: ",depth,"");
575         print_ip_sym((unsigned long)class->key);
576 }
577
578 /*
579  * printk all lock dependencies starting at <entry>:
580  */
581 static void __used
582 print_lock_dependencies(struct lock_class *class, int depth)
583 {
584         struct lock_list *entry;
585
586         if (lockdep_dependency_visit(class, depth))
587                 return;
588
589         if (DEBUG_LOCKS_WARN_ON(depth >= 20))
590                 return;
591
592         print_lock_class_header(class, depth);
593
594         list_for_each_entry(entry, &class->locks_after, entry) {
595                 if (DEBUG_LOCKS_WARN_ON(!entry->class))
596                         return;
597
598                 print_lock_dependencies(entry->class, depth + 1);
599
600                 printk("%*s ... acquired at:\n",depth,"");
601                 print_stack_trace(&entry->trace, 2);
602                 printk("\n");
603         }
604 }
605
606 static void print_kernel_version(void)
607 {
608         printk("%s %.*s\n", init_utsname()->release,
609                 (int)strcspn(init_utsname()->version, " "),
610                 init_utsname()->version);
611 }
612
613 static int very_verbose(struct lock_class *class)
614 {
615 #if VERY_VERBOSE
616         return class_filter(class);
617 #endif
618         return 0;
619 }
620
621 /*
622  * Is this the address of a static object:
623  */
624 static int static_obj(void *obj)
625 {
626         unsigned long start = (unsigned long) &_stext,
627                       end   = (unsigned long) &_end,
628                       addr  = (unsigned long) obj;
629 #ifdef CONFIG_SMP
630         int i;
631 #endif
632
633         /*
634          * static variable?
635          */
636         if ((addr >= start) && (addr < end))
637                 return 1;
638
639 #ifdef CONFIG_SMP
640         /*
641          * percpu var?
642          */
643         for_each_possible_cpu(i) {
644                 start = (unsigned long) &__per_cpu_start + per_cpu_offset(i);
645                 end   = (unsigned long) &__per_cpu_start + PERCPU_ENOUGH_ROOM
646                                         + per_cpu_offset(i);
647
648                 if ((addr >= start) && (addr < end))
649                         return 1;
650         }
651 #endif
652
653         /*
654          * module var?
655          */
656         return is_module_address(addr);
657 }
658
659 /*
660  * To make lock name printouts unique, we calculate a unique
661  * class->name_version generation counter:
662  */
663 static int count_matching_names(struct lock_class *new_class)
664 {
665         struct lock_class *class;
666         int count = 0;
667
668         if (!new_class->name)
669                 return 0;
670
671         list_for_each_entry(class, &all_lock_classes, lock_entry) {
672                 if (new_class->key - new_class->subclass == class->key)
673                         return class->name_version;
674                 if (class->name && !strcmp(class->name, new_class->name))
675                         count = max(count, class->name_version);
676         }
677
678         return count + 1;
679 }
680
681 /*
682  * Register a lock's class in the hash-table, if the class is not present
683  * yet. Otherwise we look it up. We cache the result in the lock object
684  * itself, so actual lookup of the hash should be once per lock object.
685  */
686 static inline struct lock_class *
687 look_up_lock_class(struct lockdep_map *lock, unsigned int subclass)
688 {
689         struct lockdep_subclass_key *key;
690         struct list_head *hash_head;
691         struct lock_class *class;
692
693 #ifdef CONFIG_DEBUG_LOCKDEP
694         /*
695          * If the architecture calls into lockdep before initializing
696          * the hashes then we'll warn about it later. (we cannot printk
697          * right now)
698          */
699         if (unlikely(!lockdep_initialized)) {
700                 lockdep_init();
701                 lockdep_init_error = 1;
702                 save_stack_trace(&lockdep_init_trace);
703         }
704 #endif
705
706         /*
707          * Static locks do not have their class-keys yet - for them the key
708          * is the lock object itself:
709          */
710         if (unlikely(!lock->key))
711                 lock->key = (void *)lock;
712
713         /*
714          * NOTE: the class-key must be unique. For dynamic locks, a static
715          * lock_class_key variable is passed in through the mutex_init()
716          * (or spin_lock_init()) call - which acts as the key. For static
717          * locks we use the lock object itself as the key.
718          */
719         BUILD_BUG_ON(sizeof(struct lock_class_key) >
720                         sizeof(struct lockdep_map));
721
722         key = lock->key->subkeys + subclass;
723
724         hash_head = classhashentry(key);
725
726         /*
727          * We can walk the hash lockfree, because the hash only
728          * grows, and we are careful when adding entries to the end:
729          */
730         list_for_each_entry(class, hash_head, hash_entry) {
731                 if (class->key == key) {
732                         WARN_ON_ONCE(class->name != lock->name);
733                         return class;
734                 }
735         }
736
737         return NULL;
738 }
739
740 /*
741  * Register a lock's class in the hash-table, if the class is not present
742  * yet. Otherwise we look it up. We cache the result in the lock object
743  * itself, so actual lookup of the hash should be once per lock object.
744  */
745 static inline struct lock_class *
746 register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
747 {
748         struct lockdep_subclass_key *key;
749         struct list_head *hash_head;
750         struct lock_class *class;
751         unsigned long flags;
752
753         class = look_up_lock_class(lock, subclass);
754         if (likely(class))
755                 return class;
756
757         /*
758          * Debug-check: all keys must be persistent!
759          */
760         if (!static_obj(lock->key)) {
761                 debug_locks_off();
762                 printk("INFO: trying to register non-static key.\n");
763                 printk("the code is fine but needs lockdep annotation.\n");
764                 printk("turning off the locking correctness validator.\n");
765                 dump_stack();
766
767                 return NULL;
768         }
769
770         key = lock->key->subkeys + subclass;
771         hash_head = classhashentry(key);
772
773         raw_local_irq_save(flags);
774         if (!graph_lock()) {
775                 raw_local_irq_restore(flags);
776                 return NULL;
777         }
778         /*
779          * We have to do the hash-walk again, to avoid races
780          * with another CPU:
781          */
782         list_for_each_entry(class, hash_head, hash_entry)
783                 if (class->key == key)
784                         goto out_unlock_set;
785         /*
786          * Allocate a new key from the static array, and add it to
787          * the hash:
788          */
789         if (nr_lock_classes >= MAX_LOCKDEP_KEYS) {
790                 if (!debug_locks_off_graph_unlock()) {
791                         raw_local_irq_restore(flags);
792                         return NULL;
793                 }
794                 raw_local_irq_restore(flags);
795
796                 printk("BUG: MAX_LOCKDEP_KEYS too low!\n");
797                 printk("turning off the locking correctness validator.\n");
798                 return NULL;
799         }
800         class = lock_classes + nr_lock_classes++;
801         debug_atomic_inc(&nr_unused_locks);
802         class->key = key;
803         class->name = lock->name;
804         class->subclass = subclass;
805         INIT_LIST_HEAD(&class->lock_entry);
806         INIT_LIST_HEAD(&class->locks_before);
807         INIT_LIST_HEAD(&class->locks_after);
808         class->name_version = count_matching_names(class);
809         /*
810          * We use RCU's safe list-add method to make
811          * parallel walking of the hash-list safe:
812          */
813         list_add_tail_rcu(&class->hash_entry, hash_head);
814         /*
815          * Add it to the global list of classes:
816          */
817         list_add_tail_rcu(&class->lock_entry, &all_lock_classes);
818
819         if (verbose(class)) {
820                 graph_unlock();
821                 raw_local_irq_restore(flags);
822
823                 printk("\nnew class %p: %s", class->key, class->name);
824                 if (class->name_version > 1)
825                         printk("#%d", class->name_version);
826                 printk("\n");
827                 dump_stack();
828
829                 raw_local_irq_save(flags);
830                 if (!graph_lock()) {
831                         raw_local_irq_restore(flags);
832                         return NULL;
833                 }
834         }
835 out_unlock_set:
836         graph_unlock();
837         raw_local_irq_restore(flags);
838
839         if (!subclass || force)
840                 lock->class_cache = class;
841
842         if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))
843                 return NULL;
844
845         return class;
846 }
847
848 #ifdef CONFIG_PROVE_LOCKING
849 /*
850  * Allocate a lockdep entry. (assumes the graph_lock held, returns
851  * with NULL on failure)
852  */
853 static struct lock_list *alloc_list_entry(void)
854 {
855         if (nr_list_entries >= MAX_LOCKDEP_ENTRIES) {
856                 if (!debug_locks_off_graph_unlock())
857                         return NULL;
858
859                 printk("BUG: MAX_LOCKDEP_ENTRIES too low!\n");
860                 printk("turning off the locking correctness validator.\n");
861                 return NULL;
862         }
863         return list_entries + nr_list_entries++;
864 }
865
866 /*
867  * Add a new dependency to the head of the list:
868  */
869 static int add_lock_to_list(struct lock_class *class, struct lock_class *this,
870                             struct list_head *head, unsigned long ip, int distance)
871 {
872         struct lock_list *entry;
873         /*
874          * Lock not present yet - get a new dependency struct and
875          * add it to the list:
876          */
877         entry = alloc_list_entry();
878         if (!entry)
879                 return 0;
880
881         if (!save_trace(&entry->trace))
882                 return 0;
883
884         entry->class = this;
885         entry->distance = distance;
886         /*
887          * Since we never remove from the dependency list, the list can
888          * be walked lockless by other CPUs, it's only allocation
889          * that must be protected by the spinlock. But this also means
890          * we must make new entries visible only once writes to the
891          * entry become visible - hence the RCU op:
892          */
893         list_add_tail_rcu(&entry->entry, head);
894
895         return 1;
896 }
897
898 /*
899  * Recursive, forwards-direction lock-dependency checking, used for
900  * both noncyclic checking and for hardirq-unsafe/softirq-unsafe
901  * checking.
902  *
903  * (to keep the stackframe of the recursive functions small we
904  *  use these global variables, and we also mark various helper
905  *  functions as noinline.)
906  */
907 static struct held_lock *check_source, *check_target;
908
909 /*
910  * Print a dependency chain entry (this is only done when a deadlock
911  * has been detected):
912  */
913 static noinline int
914 print_circular_bug_entry(struct lock_list *target, unsigned int depth)
915 {
916         if (debug_locks_silent)
917                 return 0;
918         printk("\n-> #%u", depth);
919         print_lock_name(target->class);
920         printk(":\n");
921         print_stack_trace(&target->trace, 6);
922
923         return 0;
924 }
925
926 /*
927  * When a circular dependency is detected, print the
928  * header first:
929  */
930 static noinline int
931 print_circular_bug_header(struct lock_list *entry, unsigned int depth)
932 {
933         struct task_struct *curr = current;
934
935         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
936                 return 0;
937
938         printk("\n=======================================================\n");
939         printk(  "[ INFO: possible circular locking dependency detected ]\n");
940         print_kernel_version();
941         printk(  "-------------------------------------------------------\n");
942         printk("%s/%d is trying to acquire lock:\n",
943                 curr->comm, task_pid_nr(curr));
944         print_lock(check_source);
945         printk("\nbut task is already holding lock:\n");
946         print_lock(check_target);
947         printk("\nwhich lock already depends on the new lock.\n\n");
948         printk("\nthe existing dependency chain (in reverse order) is:\n");
949
950         print_circular_bug_entry(entry, depth);
951
952         return 0;
953 }
954
955 static noinline int print_circular_bug_tail(void)
956 {
957         struct task_struct *curr = current;
958         struct lock_list this;
959
960         if (debug_locks_silent)
961                 return 0;
962
963         this.class = hlock_class(check_source);
964         if (!save_trace(&this.trace))
965                 return 0;
966
967         print_circular_bug_entry(&this, 0);
968
969         printk("\nother info that might help us debug this:\n\n");
970         lockdep_print_held_locks(curr);
971
972         printk("\nstack backtrace:\n");
973         dump_stack();
974
975         return 0;
976 }
977
978 #define RECURSION_LIMIT 40
979
980 static int noinline print_infinite_recursion_bug(void)
981 {
982         if (!debug_locks_off_graph_unlock())
983                 return 0;
984
985         WARN_ON(1);
986
987         return 0;
988 }
989
990 unsigned long __lockdep_count_forward_deps(struct lock_class *class,
991                                            unsigned int depth)
992 {
993         struct lock_list *entry;
994         unsigned long ret = 1;
995
996         if (lockdep_dependency_visit(class, depth))
997                 return 0;
998
999         /*
1000          * Recurse this class's dependency list:
1001          */
1002         list_for_each_entry(entry, &class->locks_after, entry)
1003                 ret += __lockdep_count_forward_deps(entry->class, depth + 1);
1004
1005         return ret;
1006 }
1007
1008 unsigned long lockdep_count_forward_deps(struct lock_class *class)
1009 {
1010         unsigned long ret, flags;
1011
1012         local_irq_save(flags);
1013         __raw_spin_lock(&lockdep_lock);
1014         ret = __lockdep_count_forward_deps(class, 0);
1015         __raw_spin_unlock(&lockdep_lock);
1016         local_irq_restore(flags);
1017
1018         return ret;
1019 }
1020
1021 unsigned long __lockdep_count_backward_deps(struct lock_class *class,
1022                                             unsigned int depth)
1023 {
1024         struct lock_list *entry;
1025         unsigned long ret = 1;
1026
1027         if (lockdep_dependency_visit(class, depth))
1028                 return 0;
1029         /*
1030          * Recurse this class's dependency list:
1031          */
1032         list_for_each_entry(entry, &class->locks_before, entry)
1033                 ret += __lockdep_count_backward_deps(entry->class, depth + 1);
1034
1035         return ret;
1036 }
1037
1038 unsigned long lockdep_count_backward_deps(struct lock_class *class)
1039 {
1040         unsigned long ret, flags;
1041
1042         local_irq_save(flags);
1043         __raw_spin_lock(&lockdep_lock);
1044         ret = __lockdep_count_backward_deps(class, 0);
1045         __raw_spin_unlock(&lockdep_lock);
1046         local_irq_restore(flags);
1047
1048         return ret;
1049 }
1050
1051 /*
1052  * Prove that the dependency graph starting at <entry> can not
1053  * lead to <target>. Print an error and return 0 if it does.
1054  */
1055 static noinline int
1056 check_noncircular(struct lock_class *source, unsigned int depth)
1057 {
1058         struct lock_list *entry;
1059
1060         if (lockdep_dependency_visit(source, depth))
1061                 return 1;
1062
1063         debug_atomic_inc(&nr_cyclic_check_recursions);
1064         if (depth > max_recursion_depth)
1065                 max_recursion_depth = depth;
1066         if (depth >= RECURSION_LIMIT)
1067                 return print_infinite_recursion_bug();
1068         /*
1069          * Check this lock's dependency list:
1070          */
1071         list_for_each_entry(entry, &source->locks_after, entry) {
1072                 if (entry->class == hlock_class(check_target))
1073                         return print_circular_bug_header(entry, depth+1);
1074                 debug_atomic_inc(&nr_cyclic_checks);
1075                 if (!check_noncircular(entry->class, depth+1))
1076                         return print_circular_bug_entry(entry, depth+1);
1077         }
1078         return 1;
1079 }
1080
1081 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
1082 /*
1083  * Forwards and backwards subgraph searching, for the purposes of
1084  * proving that two subgraphs can be connected by a new dependency
1085  * without creating any illegal irq-safe -> irq-unsafe lock dependency.
1086  */
1087 static enum lock_usage_bit find_usage_bit;
1088 static struct lock_class *forwards_match, *backwards_match;
1089
1090 /*
1091  * Find a node in the forwards-direction dependency sub-graph starting
1092  * at <source> that matches <find_usage_bit>.
1093  *
1094  * Return 2 if such a node exists in the subgraph, and put that node
1095  * into <forwards_match>.
1096  *
1097  * Return 1 otherwise and keep <forwards_match> unchanged.
1098  * Return 0 on error.
1099  */
1100 static noinline int
1101 find_usage_forwards(struct lock_class *source, unsigned int depth)
1102 {
1103         struct lock_list *entry;
1104         int ret;
1105
1106         if (lockdep_dependency_visit(source, depth))
1107                 return 1;
1108
1109         if (depth > max_recursion_depth)
1110                 max_recursion_depth = depth;
1111         if (depth >= RECURSION_LIMIT)
1112                 return print_infinite_recursion_bug();
1113
1114         debug_atomic_inc(&nr_find_usage_forwards_checks);
1115         if (source->usage_mask & (1 << find_usage_bit)) {
1116                 forwards_match = source;
1117                 return 2;
1118         }
1119
1120         /*
1121          * Check this lock's dependency list:
1122          */
1123         list_for_each_entry(entry, &source->locks_after, entry) {
1124                 debug_atomic_inc(&nr_find_usage_forwards_recursions);
1125                 ret = find_usage_forwards(entry->class, depth+1);
1126                 if (ret == 2 || ret == 0)
1127                         return ret;
1128         }
1129         return 1;
1130 }
1131
1132 /*
1133  * Find a node in the backwards-direction dependency sub-graph starting
1134  * at <source> that matches <find_usage_bit>.
1135  *
1136  * Return 2 if such a node exists in the subgraph, and put that node
1137  * into <backwards_match>.
1138  *
1139  * Return 1 otherwise and keep <backwards_match> unchanged.
1140  * Return 0 on error.
1141  */
1142 static noinline int
1143 find_usage_backwards(struct lock_class *source, unsigned int depth)
1144 {
1145         struct lock_list *entry;
1146         int ret;
1147
1148         if (lockdep_dependency_visit(source, depth))
1149                 return 1;
1150
1151         if (!__raw_spin_is_locked(&lockdep_lock))
1152                 return DEBUG_LOCKS_WARN_ON(1);
1153
1154         if (depth > max_recursion_depth)
1155                 max_recursion_depth = depth;
1156         if (depth >= RECURSION_LIMIT)
1157                 return print_infinite_recursion_bug();
1158
1159         debug_atomic_inc(&nr_find_usage_backwards_checks);
1160         if (source->usage_mask & (1 << find_usage_bit)) {
1161                 backwards_match = source;
1162                 return 2;
1163         }
1164
1165         if (!source && debug_locks_off_graph_unlock()) {
1166                 WARN_ON(1);
1167                 return 0;
1168         }
1169
1170         /*
1171          * Check this lock's dependency list:
1172          */
1173         list_for_each_entry(entry, &source->locks_before, entry) {
1174                 debug_atomic_inc(&nr_find_usage_backwards_recursions);
1175                 ret = find_usage_backwards(entry->class, depth+1);
1176                 if (ret == 2 || ret == 0)
1177                         return ret;
1178         }
1179         return 1;
1180 }
1181
1182 static int
1183 print_bad_irq_dependency(struct task_struct *curr,
1184                          struct held_lock *prev,
1185                          struct held_lock *next,
1186                          enum lock_usage_bit bit1,
1187                          enum lock_usage_bit bit2,
1188                          const char *irqclass)
1189 {
1190         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1191                 return 0;
1192
1193         printk("\n======================================================\n");
1194         printk(  "[ INFO: %s-safe -> %s-unsafe lock order detected ]\n",
1195                 irqclass, irqclass);
1196         print_kernel_version();
1197         printk(  "------------------------------------------------------\n");
1198         printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
1199                 curr->comm, task_pid_nr(curr),
1200                 curr->hardirq_context, hardirq_count() >> HARDIRQ_SHIFT,
1201                 curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT,
1202                 curr->hardirqs_enabled,
1203                 curr->softirqs_enabled);
1204         print_lock(next);
1205
1206         printk("\nand this task is already holding:\n");
1207         print_lock(prev);
1208         printk("which would create a new lock dependency:\n");
1209         print_lock_name(hlock_class(prev));
1210         printk(" ->");
1211         print_lock_name(hlock_class(next));
1212         printk("\n");
1213
1214         printk("\nbut this new dependency connects a %s-irq-safe lock:\n",
1215                 irqclass);
1216         print_lock_name(backwards_match);
1217         printk("\n... which became %s-irq-safe at:\n", irqclass);
1218
1219         print_stack_trace(backwards_match->usage_traces + bit1, 1);
1220
1221         printk("\nto a %s-irq-unsafe lock:\n", irqclass);
1222         print_lock_name(forwards_match);
1223         printk("\n... which became %s-irq-unsafe at:\n", irqclass);
1224         printk("...");
1225
1226         print_stack_trace(forwards_match->usage_traces + bit2, 1);
1227
1228         printk("\nother info that might help us debug this:\n\n");
1229         lockdep_print_held_locks(curr);
1230
1231         printk("\nthe %s-irq-safe lock's dependencies:\n", irqclass);
1232         print_lock_dependencies(backwards_match, 0);
1233
1234         printk("\nthe %s-irq-unsafe lock's dependencies:\n", irqclass);
1235         print_lock_dependencies(forwards_match, 0);
1236
1237         printk("\nstack backtrace:\n");
1238         dump_stack();
1239
1240         return 0;
1241 }
1242
1243 static int
1244 check_usage(struct task_struct *curr, struct held_lock *prev,
1245             struct held_lock *next, enum lock_usage_bit bit_backwards,
1246             enum lock_usage_bit bit_forwards, const char *irqclass)
1247 {
1248         int ret;
1249
1250         find_usage_bit = bit_backwards;
1251         /* fills in <backwards_match> */
1252         ret = find_usage_backwards(hlock_class(prev), 0);
1253         if (!ret || ret == 1)
1254                 return ret;
1255
1256         find_usage_bit = bit_forwards;
1257         ret = find_usage_forwards(hlock_class(next), 0);
1258         if (!ret || ret == 1)
1259                 return ret;
1260         /* ret == 2 */
1261         return print_bad_irq_dependency(curr, prev, next,
1262                         bit_backwards, bit_forwards, irqclass);
1263 }
1264
1265 static int
1266 check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
1267                 struct held_lock *next)
1268 {
1269         /*
1270          * Prove that the new dependency does not connect a hardirq-safe
1271          * lock with a hardirq-unsafe lock - to achieve this we search
1272          * the backwards-subgraph starting at <prev>, and the
1273          * forwards-subgraph starting at <next>:
1274          */
1275         if (!check_usage(curr, prev, next, LOCK_USED_IN_HARDIRQ,
1276                                         LOCK_ENABLED_HARDIRQS, "hard"))
1277                 return 0;
1278
1279         /*
1280          * Prove that the new dependency does not connect a hardirq-safe-read
1281          * lock with a hardirq-unsafe lock - to achieve this we search
1282          * the backwards-subgraph starting at <prev>, and the
1283          * forwards-subgraph starting at <next>:
1284          */
1285         if (!check_usage(curr, prev, next, LOCK_USED_IN_HARDIRQ_READ,
1286                                         LOCK_ENABLED_HARDIRQS, "hard-read"))
1287                 return 0;
1288
1289         /*
1290          * Prove that the new dependency does not connect a softirq-safe
1291          * lock with a softirq-unsafe lock - to achieve this we search
1292          * the backwards-subgraph starting at <prev>, and the
1293          * forwards-subgraph starting at <next>:
1294          */
1295         if (!check_usage(curr, prev, next, LOCK_USED_IN_SOFTIRQ,
1296                                         LOCK_ENABLED_SOFTIRQS, "soft"))
1297                 return 0;
1298         /*
1299          * Prove that the new dependency does not connect a softirq-safe-read
1300          * lock with a softirq-unsafe lock - to achieve this we search
1301          * the backwards-subgraph starting at <prev>, and the
1302          * forwards-subgraph starting at <next>:
1303          */
1304         if (!check_usage(curr, prev, next, LOCK_USED_IN_SOFTIRQ_READ,
1305                                         LOCK_ENABLED_SOFTIRQS, "soft"))
1306                 return 0;
1307
1308         return 1;
1309 }
1310
1311 static void inc_chains(void)
1312 {
1313         if (current->hardirq_context)
1314                 nr_hardirq_chains++;
1315         else {
1316                 if (current->softirq_context)
1317                         nr_softirq_chains++;
1318                 else
1319                         nr_process_chains++;
1320         }
1321 }
1322
1323 #else
1324
1325 static inline int
1326 check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
1327                 struct held_lock *next)
1328 {
1329         return 1;
1330 }
1331
1332 static inline void inc_chains(void)
1333 {
1334         nr_process_chains++;
1335 }
1336
1337 #endif
1338
1339 static int
1340 print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
1341                    struct held_lock *next)
1342 {
1343         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1344                 return 0;
1345
1346         printk("\n=============================================\n");
1347         printk(  "[ INFO: possible recursive locking detected ]\n");
1348         print_kernel_version();
1349         printk(  "---------------------------------------------\n");
1350         printk("%s/%d is trying to acquire lock:\n",
1351                 curr->comm, task_pid_nr(curr));
1352         print_lock(next);
1353         printk("\nbut task is already holding lock:\n");
1354         print_lock(prev);
1355
1356         printk("\nother info that might help us debug this:\n");
1357         lockdep_print_held_locks(curr);
1358
1359         printk("\nstack backtrace:\n");
1360         dump_stack();
1361
1362         return 0;
1363 }
1364
1365 /*
1366  * Check whether we are holding such a class already.
1367  *
1368  * (Note that this has to be done separately, because the graph cannot
1369  * detect such classes of deadlocks.)
1370  *
1371  * Returns: 0 on deadlock detected, 1 on OK, 2 on recursive read
1372  */
1373 static int
1374 check_deadlock(struct task_struct *curr, struct held_lock *next,
1375                struct lockdep_map *next_instance, int read)
1376 {
1377         struct held_lock *prev;
1378         struct held_lock *nest = NULL;
1379         int i;
1380
1381         for (i = 0; i < curr->lockdep_depth; i++) {
1382                 prev = curr->held_locks + i;
1383
1384                 if (prev->instance == next->nest_lock)
1385                         nest = prev;
1386
1387                 if (hlock_class(prev) != hlock_class(next))
1388                         continue;
1389
1390                 /*
1391                  * Allow read-after-read recursion of the same
1392                  * lock class (i.e. read_lock(lock)+read_lock(lock)):
1393                  */
1394                 if ((read == 2) && prev->read)
1395                         return 2;
1396
1397                 /*
1398                  * We're holding the nest_lock, which serializes this lock's
1399                  * nesting behaviour.
1400                  */
1401                 if (nest)
1402                         return 2;
1403
1404                 return print_deadlock_bug(curr, prev, next);
1405         }
1406         return 1;
1407 }
1408
1409 /*
1410  * There was a chain-cache miss, and we are about to add a new dependency
1411  * to a previous lock. We recursively validate the following rules:
1412  *
1413  *  - would the adding of the <prev> -> <next> dependency create a
1414  *    circular dependency in the graph? [== circular deadlock]
1415  *
1416  *  - does the new prev->next dependency connect any hardirq-safe lock
1417  *    (in the full backwards-subgraph starting at <prev>) with any
1418  *    hardirq-unsafe lock (in the full forwards-subgraph starting at
1419  *    <next>)? [== illegal lock inversion with hardirq contexts]
1420  *
1421  *  - does the new prev->next dependency connect any softirq-safe lock
1422  *    (in the full backwards-subgraph starting at <prev>) with any
1423  *    softirq-unsafe lock (in the full forwards-subgraph starting at
1424  *    <next>)? [== illegal lock inversion with softirq contexts]
1425  *
1426  * any of these scenarios could lead to a deadlock.
1427  *
1428  * Then if all the validations pass, we add the forwards and backwards
1429  * dependency.
1430  */
1431 static int
1432 check_prev_add(struct task_struct *curr, struct held_lock *prev,
1433                struct held_lock *next, int distance)
1434 {
1435         struct lock_list *entry;
1436         int ret;
1437
1438         /*
1439          * Prove that the new <prev> -> <next> dependency would not
1440          * create a circular dependency in the graph. (We do this by
1441          * forward-recursing into the graph starting at <next>, and
1442          * checking whether we can reach <prev>.)
1443          *
1444          * We are using global variables to control the recursion, to
1445          * keep the stackframe size of the recursive functions low:
1446          */
1447         check_source = next;
1448         check_target = prev;
1449         if (!(check_noncircular(hlock_class(next), 0)))
1450                 return print_circular_bug_tail();
1451
1452         if (!check_prev_add_irq(curr, prev, next))
1453                 return 0;
1454
1455         /*
1456          * For recursive read-locks we do all the dependency checks,
1457          * but we dont store read-triggered dependencies (only
1458          * write-triggered dependencies). This ensures that only the
1459          * write-side dependencies matter, and that if for example a
1460          * write-lock never takes any other locks, then the reads are
1461          * equivalent to a NOP.
1462          */
1463         if (next->read == 2 || prev->read == 2)
1464                 return 1;
1465         /*
1466          * Is the <prev> -> <next> dependency already present?
1467          *
1468          * (this may occur even though this is a new chain: consider
1469          *  e.g. the L1 -> L2 -> L3 -> L4 and the L5 -> L1 -> L2 -> L3
1470          *  chains - the second one will be new, but L1 already has
1471          *  L2 added to its dependency list, due to the first chain.)
1472          */
1473         list_for_each_entry(entry, &hlock_class(prev)->locks_after, entry) {
1474                 if (entry->class == hlock_class(next)) {
1475                         if (distance == 1)
1476                                 entry->distance = 1;
1477                         return 2;
1478                 }
1479         }
1480
1481         /*
1482          * Ok, all validations passed, add the new lock
1483          * to the previous lock's dependency list:
1484          */
1485         ret = add_lock_to_list(hlock_class(prev), hlock_class(next),
1486                                &hlock_class(prev)->locks_after,
1487                                next->acquire_ip, distance);
1488
1489         if (!ret)
1490                 return 0;
1491
1492         ret = add_lock_to_list(hlock_class(next), hlock_class(prev),
1493                                &hlock_class(next)->locks_before,
1494                                next->acquire_ip, distance);
1495         if (!ret)
1496                 return 0;
1497
1498         /*
1499          * Debugging printouts:
1500          */
1501         if (verbose(hlock_class(prev)) || verbose(hlock_class(next))) {
1502                 graph_unlock();
1503                 printk("\n new dependency: ");
1504                 print_lock_name(hlock_class(prev));
1505                 printk(" => ");
1506                 print_lock_name(hlock_class(next));
1507                 printk("\n");
1508                 dump_stack();
1509                 return graph_lock();
1510         }
1511         return 1;
1512 }
1513
1514 /*
1515  * Add the dependency to all directly-previous locks that are 'relevant'.
1516  * The ones that are relevant are (in increasing distance from curr):
1517  * all consecutive trylock entries and the final non-trylock entry - or
1518  * the end of this context's lock-chain - whichever comes first.
1519  */
1520 static int
1521 check_prevs_add(struct task_struct *curr, struct held_lock *next)
1522 {
1523         int depth = curr->lockdep_depth;
1524         struct held_lock *hlock;
1525
1526         /*
1527          * Debugging checks.
1528          *
1529          * Depth must not be zero for a non-head lock:
1530          */
1531         if (!depth)
1532                 goto out_bug;
1533         /*
1534          * At least two relevant locks must exist for this
1535          * to be a head:
1536          */
1537         if (curr->held_locks[depth].irq_context !=
1538                         curr->held_locks[depth-1].irq_context)
1539                 goto out_bug;
1540
1541         for (;;) {
1542                 int distance = curr->lockdep_depth - depth + 1;
1543                 hlock = curr->held_locks + depth-1;
1544                 /*
1545                  * Only non-recursive-read entries get new dependencies
1546                  * added:
1547                  */
1548                 if (hlock->read != 2) {
1549                         if (!check_prev_add(curr, hlock, next, distance))
1550                                 return 0;
1551                         /*
1552                          * Stop after the first non-trylock entry,
1553                          * as non-trylock entries have added their
1554                          * own direct dependencies already, so this
1555                          * lock is connected to them indirectly:
1556                          */
1557                         if (!hlock->trylock)
1558                                 break;
1559                 }
1560                 depth--;
1561                 /*
1562                  * End of lock-stack?
1563                  */
1564                 if (!depth)
1565                         break;
1566                 /*
1567                  * Stop the search if we cross into another context:
1568                  */
1569                 if (curr->held_locks[depth].irq_context !=
1570                                 curr->held_locks[depth-1].irq_context)
1571                         break;
1572         }
1573         return 1;
1574 out_bug:
1575         if (!debug_locks_off_graph_unlock())
1576                 return 0;
1577
1578         WARN_ON(1);
1579
1580         return 0;
1581 }
1582
1583 unsigned long nr_lock_chains;
1584 struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
1585 int nr_chain_hlocks;
1586 static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
1587
1588 struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
1589 {
1590         return lock_classes + chain_hlocks[chain->base + i];
1591 }
1592
1593 /*
1594  * Look up a dependency chain. If the key is not present yet then
1595  * add it and return 1 - in this case the new dependency chain is
1596  * validated. If the key is already hashed, return 0.
1597  * (On return with 1 graph_lock is held.)
1598  */
1599 static inline int lookup_chain_cache(struct task_struct *curr,
1600                                      struct held_lock *hlock,
1601                                      u64 chain_key)
1602 {
1603         struct lock_class *class = hlock_class(hlock);
1604         struct list_head *hash_head = chainhashentry(chain_key);
1605         struct lock_chain *chain;
1606         struct held_lock *hlock_curr, *hlock_next;
1607         int i, j, n, cn;
1608
1609         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
1610                 return 0;
1611         /*
1612          * We can walk it lock-free, because entries only get added
1613          * to the hash:
1614          */
1615         list_for_each_entry(chain, hash_head, entry) {
1616                 if (chain->chain_key == chain_key) {
1617 cache_hit:
1618                         debug_atomic_inc(&chain_lookup_hits);
1619                         if (very_verbose(class))
1620                                 printk("\nhash chain already cached, key: "
1621                                         "%016Lx tail class: [%p] %s\n",
1622                                         (unsigned long long)chain_key,
1623                                         class->key, class->name);
1624                         return 0;
1625                 }
1626         }
1627         if (very_verbose(class))
1628                 printk("\nnew hash chain, key: %016Lx tail class: [%p] %s\n",
1629                         (unsigned long long)chain_key, class->key, class->name);
1630         /*
1631          * Allocate a new chain entry from the static array, and add
1632          * it to the hash:
1633          */
1634         if (!graph_lock())
1635                 return 0;
1636         /*
1637          * We have to walk the chain again locked - to avoid duplicates:
1638          */
1639         list_for_each_entry(chain, hash_head, entry) {
1640                 if (chain->chain_key == chain_key) {
1641                         graph_unlock();
1642                         goto cache_hit;
1643                 }
1644         }
1645         if (unlikely(nr_lock_chains >= MAX_LOCKDEP_CHAINS)) {
1646                 if (!debug_locks_off_graph_unlock())
1647                         return 0;
1648
1649                 printk("BUG: MAX_LOCKDEP_CHAINS too low!\n");
1650                 printk("turning off the locking correctness validator.\n");
1651                 return 0;
1652         }
1653         chain = lock_chains + nr_lock_chains++;
1654         chain->chain_key = chain_key;
1655         chain->irq_context = hlock->irq_context;
1656         /* Find the first held_lock of current chain */
1657         hlock_next = hlock;
1658         for (i = curr->lockdep_depth - 1; i >= 0; i--) {
1659                 hlock_curr = curr->held_locks + i;
1660                 if (hlock_curr->irq_context != hlock_next->irq_context)
1661                         break;
1662                 hlock_next = hlock;
1663         }
1664         i++;
1665         chain->depth = curr->lockdep_depth + 1 - i;
1666         cn = nr_chain_hlocks;
1667         while (cn + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS) {
1668                 n = cmpxchg(&nr_chain_hlocks, cn, cn + chain->depth);
1669                 if (n == cn)
1670                         break;
1671                 cn = n;
1672         }
1673         if (likely(cn + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) {
1674                 chain->base = cn;
1675                 for (j = 0; j < chain->depth - 1; j++, i++) {
1676                         int lock_id = curr->held_locks[i].class_idx - 1;
1677                         chain_hlocks[chain->base + j] = lock_id;
1678                 }
1679                 chain_hlocks[chain->base + j] = class - lock_classes;
1680         }
1681         list_add_tail_rcu(&chain->entry, hash_head);
1682         debug_atomic_inc(&chain_lookup_misses);
1683         inc_chains();
1684
1685         return 1;
1686 }
1687
1688 static int validate_chain(struct task_struct *curr, struct lockdep_map *lock,
1689                 struct held_lock *hlock, int chain_head, u64 chain_key)
1690 {
1691         /*
1692          * Trylock needs to maintain the stack of held locks, but it
1693          * does not add new dependencies, because trylock can be done
1694          * in any order.
1695          *
1696          * We look up the chain_key and do the O(N^2) check and update of
1697          * the dependencies only if this is a new dependency chain.
1698          * (If lookup_chain_cache() returns with 1 it acquires
1699          * graph_lock for us)
1700          */
1701         if (!hlock->trylock && (hlock->check == 2) &&
1702             lookup_chain_cache(curr, hlock, chain_key)) {
1703                 /*
1704                  * Check whether last held lock:
1705                  *
1706                  * - is irq-safe, if this lock is irq-unsafe
1707                  * - is softirq-safe, if this lock is hardirq-unsafe
1708                  *
1709                  * And check whether the new lock's dependency graph
1710                  * could lead back to the previous lock.
1711                  *
1712                  * any of these scenarios could lead to a deadlock. If
1713                  * All validations
1714                  */
1715                 int ret = check_deadlock(curr, hlock, lock, hlock->read);
1716
1717                 if (!ret)
1718                         return 0;
1719                 /*
1720                  * Mark recursive read, as we jump over it when
1721                  * building dependencies (just like we jump over
1722                  * trylock entries):
1723                  */
1724                 if (ret == 2)
1725                         hlock->read = 2;
1726                 /*
1727                  * Add dependency only if this lock is not the head
1728                  * of the chain, and if it's not a secondary read-lock:
1729                  */
1730                 if (!chain_head && ret != 2)
1731                         if (!check_prevs_add(curr, hlock))
1732                                 return 0;
1733                 graph_unlock();
1734         } else
1735                 /* after lookup_chain_cache(): */
1736                 if (unlikely(!debug_locks))
1737                         return 0;
1738
1739         return 1;
1740 }
1741 #else
1742 static inline int validate_chain(struct task_struct *curr,
1743                 struct lockdep_map *lock, struct held_lock *hlock,
1744                 int chain_head, u64 chain_key)
1745 {
1746         return 1;
1747 }
1748 #endif
1749
1750 /*
1751  * We are building curr_chain_key incrementally, so double-check
1752  * it from scratch, to make sure that it's done correctly:
1753  */
1754 static void check_chain_key(struct task_struct *curr)
1755 {
1756 #ifdef CONFIG_DEBUG_LOCKDEP
1757         struct held_lock *hlock, *prev_hlock = NULL;
1758         unsigned int i, id;
1759         u64 chain_key = 0;
1760
1761         for (i = 0; i < curr->lockdep_depth; i++) {
1762                 hlock = curr->held_locks + i;
1763                 if (chain_key != hlock->prev_chain_key) {
1764                         debug_locks_off();
1765                         WARN(1, "hm#1, depth: %u [%u], %016Lx != %016Lx\n",
1766                                 curr->lockdep_depth, i,
1767                                 (unsigned long long)chain_key,
1768                                 (unsigned long long)hlock->prev_chain_key);
1769                         return;
1770                 }
1771                 id = hlock->class_idx - 1;
1772                 if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
1773                         return;
1774
1775                 if (prev_hlock && (prev_hlock->irq_context !=
1776                                                         hlock->irq_context))
1777                         chain_key = 0;
1778                 chain_key = iterate_chain_key(chain_key, id);
1779                 prev_hlock = hlock;
1780         }
1781         if (chain_key != curr->curr_chain_key) {
1782                 debug_locks_off();
1783                 WARN(1, "hm#2, depth: %u [%u], %016Lx != %016Lx\n",
1784                         curr->lockdep_depth, i,
1785                         (unsigned long long)chain_key,
1786                         (unsigned long long)curr->curr_chain_key);
1787         }
1788 #endif
1789 }
1790
1791 static int
1792 print_usage_bug(struct task_struct *curr, struct held_lock *this,
1793                 enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
1794 {
1795         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1796                 return 0;
1797
1798         printk("\n=================================\n");
1799         printk(  "[ INFO: inconsistent lock state ]\n");
1800         print_kernel_version();
1801         printk(  "---------------------------------\n");
1802
1803         printk("inconsistent {%s} -> {%s} usage.\n",
1804                 usage_str[prev_bit], usage_str[new_bit]);
1805
1806         printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] takes:\n",
1807                 curr->comm, task_pid_nr(curr),
1808                 trace_hardirq_context(curr), hardirq_count() >> HARDIRQ_SHIFT,
1809                 trace_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT,
1810                 trace_hardirqs_enabled(curr),
1811                 trace_softirqs_enabled(curr));
1812         print_lock(this);
1813
1814         printk("{%s} state was registered at:\n", usage_str[prev_bit]);
1815         print_stack_trace(hlock_class(this)->usage_traces + prev_bit, 1);
1816
1817         print_irqtrace_events(curr);
1818         printk("\nother info that might help us debug this:\n");
1819         lockdep_print_held_locks(curr);
1820
1821         printk("\nstack backtrace:\n");
1822         dump_stack();
1823
1824         return 0;
1825 }
1826
1827 /*
1828  * Print out an error if an invalid bit is set:
1829  */
1830 static inline int
1831 valid_state(struct task_struct *curr, struct held_lock *this,
1832             enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit)
1833 {
1834         if (unlikely(hlock_class(this)->usage_mask & (1 << bad_bit)))
1835                 return print_usage_bug(curr, this, bad_bit, new_bit);
1836         return 1;
1837 }
1838
1839 static int mark_lock(struct task_struct *curr, struct held_lock *this,
1840                      enum lock_usage_bit new_bit);
1841
1842 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
1843
1844 /*
1845  * print irq inversion bug:
1846  */
1847 static int
1848 print_irq_inversion_bug(struct task_struct *curr, struct lock_class *other,
1849                         struct held_lock *this, int forwards,
1850                         const char *irqclass)
1851 {
1852         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1853                 return 0;
1854
1855         printk("\n=========================================================\n");
1856         printk(  "[ INFO: possible irq lock inversion dependency detected ]\n");
1857         print_kernel_version();
1858         printk(  "---------------------------------------------------------\n");
1859         printk("%s/%d just changed the state of lock:\n",
1860                 curr->comm, task_pid_nr(curr));
1861         print_lock(this);
1862         if (forwards)
1863                 printk("but this lock took another, %s-irq-unsafe lock in the past:\n", irqclass);
1864         else
1865                 printk("but this lock was taken by another, %s-irq-safe lock in the past:\n", irqclass);
1866         print_lock_name(other);
1867         printk("\n\nand interrupts could create inverse lock ordering between them.\n\n");
1868
1869         printk("\nother info that might help us debug this:\n");
1870         lockdep_print_held_locks(curr);
1871
1872         printk("\nthe first lock's dependencies:\n");
1873         print_lock_dependencies(hlock_class(this), 0);
1874
1875         printk("\nthe second lock's dependencies:\n");
1876         print_lock_dependencies(other, 0);
1877
1878         printk("\nstack backtrace:\n");
1879         dump_stack();
1880
1881         return 0;
1882 }
1883
1884 /*
1885  * Prove that in the forwards-direction subgraph starting at <this>
1886  * there is no lock matching <mask>:
1887  */
1888 static int
1889 check_usage_forwards(struct task_struct *curr, struct held_lock *this,
1890                      enum lock_usage_bit bit, const char *irqclass)
1891 {
1892         int ret;
1893
1894         find_usage_bit = bit;
1895         /* fills in <forwards_match> */
1896         ret = find_usage_forwards(hlock_class(this), 0);
1897         if (!ret || ret == 1)
1898                 return ret;
1899
1900         return print_irq_inversion_bug(curr, forwards_match, this, 1, irqclass);
1901 }
1902
1903 /*
1904  * Prove that in the backwards-direction subgraph starting at <this>
1905  * there is no lock matching <mask>:
1906  */
1907 static int
1908 check_usage_backwards(struct task_struct *curr, struct held_lock *this,
1909                       enum lock_usage_bit bit, const char *irqclass)
1910 {
1911         int ret;
1912
1913         find_usage_bit = bit;
1914         /* fills in <backwards_match> */
1915         ret = find_usage_backwards(hlock_class(this), 0);
1916         if (!ret || ret == 1)
1917                 return ret;
1918
1919         return print_irq_inversion_bug(curr, backwards_match, this, 0, irqclass);
1920 }
1921
1922 void print_irqtrace_events(struct task_struct *curr)
1923 {
1924         printk("irq event stamp: %u\n", curr->irq_events);
1925         printk("hardirqs last  enabled at (%u): ", curr->hardirq_enable_event);
1926         print_ip_sym(curr->hardirq_enable_ip);
1927         printk("hardirqs last disabled at (%u): ", curr->hardirq_disable_event);
1928         print_ip_sym(curr->hardirq_disable_ip);
1929         printk("softirqs last  enabled at (%u): ", curr->softirq_enable_event);
1930         print_ip_sym(curr->softirq_enable_ip);
1931         printk("softirqs last disabled at (%u): ", curr->softirq_disable_event);
1932         print_ip_sym(curr->softirq_disable_ip);
1933 }
1934
1935 static int hardirq_verbose(struct lock_class *class)
1936 {
1937 #if HARDIRQ_VERBOSE
1938         return class_filter(class);
1939 #endif
1940         return 0;
1941 }
1942
1943 static int softirq_verbose(struct lock_class *class)
1944 {
1945 #if SOFTIRQ_VERBOSE
1946         return class_filter(class);
1947 #endif
1948         return 0;
1949 }
1950
1951 #define STRICT_READ_CHECKS      1
1952
1953 static int mark_lock_irq(struct task_struct *curr, struct held_lock *this,
1954                 enum lock_usage_bit new_bit)
1955 {
1956         int ret = 1;
1957
1958         switch(new_bit) {
1959         case LOCK_USED_IN_HARDIRQ:
1960                 if (!valid_state(curr, this, new_bit, LOCK_ENABLED_HARDIRQS))
1961                         return 0;
1962                 if (!valid_state(curr, this, new_bit,
1963                                  LOCK_ENABLED_HARDIRQS_READ))
1964                         return 0;
1965                 /*
1966                  * just marked it hardirq-safe, check that this lock
1967                  * took no hardirq-unsafe lock in the past:
1968                  */
1969                 if (!check_usage_forwards(curr, this,
1970                                           LOCK_ENABLED_HARDIRQS, "hard"))
1971                         return 0;
1972 #if STRICT_READ_CHECKS
1973                 /*
1974                  * just marked it hardirq-safe, check that this lock
1975                  * took no hardirq-unsafe-read lock in the past:
1976                  */
1977                 if (!check_usage_forwards(curr, this,
1978                                 LOCK_ENABLED_HARDIRQS_READ, "hard-read"))
1979                         return 0;
1980 #endif
1981                 if (hardirq_verbose(hlock_class(this)))
1982                         ret = 2;
1983                 break;
1984         case LOCK_USED_IN_SOFTIRQ:
1985                 if (!valid_state(curr, this, new_bit, LOCK_ENABLED_SOFTIRQS))
1986                         return 0;
1987                 if (!valid_state(curr, this, new_bit,
1988                                  LOCK_ENABLED_SOFTIRQS_READ))
1989                         return 0;
1990                 /*
1991                  * just marked it softirq-safe, check that this lock
1992                  * took no softirq-unsafe lock in the past:
1993                  */
1994                 if (!check_usage_forwards(curr, this,
1995                                           LOCK_ENABLED_SOFTIRQS, "soft"))
1996                         return 0;
1997 #if STRICT_READ_CHECKS
1998                 /*
1999                  * just marked it softirq-safe, check that this lock
2000                  * took no softirq-unsafe-read lock in the past:
2001                  */
2002                 if (!check_usage_forwards(curr, this,
2003                                 LOCK_ENABLED_SOFTIRQS_READ, "soft-read"))
2004                         return 0;
2005 #endif
2006                 if (softirq_verbose(hlock_class(this)))
2007                         ret = 2;
2008                 break;
2009         case LOCK_USED_IN_HARDIRQ_READ:
2010                 if (!valid_state(curr, this, new_bit, LOCK_ENABLED_HARDIRQS))
2011                         return 0;
2012                 /*
2013                  * just marked it hardirq-read-safe, check that this lock
2014                  * took no hardirq-unsafe lock in the past:
2015                  */
2016                 if (!check_usage_forwards(curr, this,
2017                                           LOCK_ENABLED_HARDIRQS, "hard"))
2018                         return 0;
2019                 if (hardirq_verbose(hlock_class(this)))
2020                         ret = 2;
2021                 break;
2022         case LOCK_USED_IN_SOFTIRQ_READ:
2023                 if (!valid_state(curr, this, new_bit, LOCK_ENABLED_SOFTIRQS))
2024                         return 0;
2025                 /*
2026                  * just marked it softirq-read-safe, check that this lock
2027                  * took no softirq-unsafe lock in the past:
2028                  */
2029                 if (!check_usage_forwards(curr, this,
2030                                           LOCK_ENABLED_SOFTIRQS, "soft"))
2031                         return 0;
2032                 if (softirq_verbose(hlock_class(this)))
2033                         ret = 2;
2034                 break;
2035         case LOCK_ENABLED_HARDIRQS:
2036                 if (!valid_state(curr, this, new_bit, LOCK_USED_IN_HARDIRQ))
2037                         return 0;
2038                 if (!valid_state(curr, this, new_bit,
2039                                  LOCK_USED_IN_HARDIRQ_READ))
2040                         return 0;
2041                 /*
2042                  * just marked it hardirq-unsafe, check that no hardirq-safe
2043                  * lock in the system ever took it in the past:
2044                  */
2045                 if (!check_usage_backwards(curr, this,
2046                                            LOCK_USED_IN_HARDIRQ, "hard"))
2047                         return 0;
2048 #if STRICT_READ_CHECKS
2049                 /*
2050                  * just marked it hardirq-unsafe, check that no
2051                  * hardirq-safe-read lock in the system ever took
2052                  * it in the past:
2053                  */
2054                 if (!check_usage_backwards(curr, this,
2055                                    LOCK_USED_IN_HARDIRQ_READ, "hard-read"))
2056                         return 0;
2057 #endif
2058                 if (hardirq_verbose(hlock_class(this)))
2059                         ret = 2;
2060                 break;
2061         case LOCK_ENABLED_SOFTIRQS:
2062                 if (!valid_state(curr, this, new_bit, LOCK_USED_IN_SOFTIRQ))
2063                         return 0;
2064                 if (!valid_state(curr, this, new_bit,
2065                                  LOCK_USED_IN_SOFTIRQ_READ))
2066                         return 0;
2067                 /*
2068                  * just marked it softirq-unsafe, check that no softirq-safe
2069                  * lock in the system ever took it in the past:
2070                  */
2071                 if (!check_usage_backwards(curr, this,
2072                                            LOCK_USED_IN_SOFTIRQ, "soft"))
2073                         return 0;
2074 #if STRICT_READ_CHECKS
2075                 /*
2076                  * just marked it softirq-unsafe, check that no
2077                  * softirq-safe-read lock in the system ever took
2078                  * it in the past:
2079                  */
2080                 if (!check_usage_backwards(curr, this,
2081                                    LOCK_USED_IN_SOFTIRQ_READ, "soft-read"))
2082                         return 0;
2083 #endif
2084                 if (softirq_verbose(hlock_class(this)))
2085                         ret = 2;
2086                 break;
2087         case LOCK_ENABLED_HARDIRQS_READ:
2088                 if (!valid_state(curr, this, new_bit, LOCK_USED_IN_HARDIRQ))
2089                         return 0;
2090 #if STRICT_READ_CHECKS
2091                 /*
2092                  * just marked it hardirq-read-unsafe, check that no
2093                  * hardirq-safe lock in the system ever took it in the past:
2094                  */
2095                 if (!check_usage_backwards(curr, this,
2096                                            LOCK_USED_IN_HARDIRQ, "hard"))
2097                         return 0;
2098 #endif
2099                 if (hardirq_verbose(hlock_class(this)))
2100                         ret = 2;
2101                 break;
2102         case LOCK_ENABLED_SOFTIRQS_READ:
2103                 if (!valid_state(curr, this, new_bit, LOCK_USED_IN_SOFTIRQ))
2104                         return 0;
2105 #if STRICT_READ_CHECKS
2106                 /*
2107                  * just marked it softirq-read-unsafe, check that no
2108                  * softirq-safe lock in the system ever took it in the past:
2109                  */
2110                 if (!check_usage_backwards(curr, this,
2111                                            LOCK_USED_IN_SOFTIRQ, "soft"))
2112                         return 0;
2113 #endif
2114                 if (softirq_verbose(hlock_class(this)))
2115                         ret = 2;
2116                 break;
2117         default:
2118                 WARN_ON(1);
2119                 break;
2120         }
2121
2122         return ret;
2123 }
2124
2125 /*
2126  * Mark all held locks with a usage bit:
2127  */
2128 static int
2129 mark_held_locks(struct task_struct *curr, int hardirq)
2130 {
2131         enum lock_usage_bit usage_bit;
2132         struct held_lock *hlock;
2133         int i;
2134
2135         for (i = 0; i < curr->lockdep_depth; i++) {
2136                 hlock = curr->held_locks + i;
2137
2138                 if (hardirq) {
2139                         if (hlock->read)
2140                                 usage_bit = LOCK_ENABLED_HARDIRQS_READ;
2141                         else
2142                                 usage_bit = LOCK_ENABLED_HARDIRQS;
2143                 } else {
2144                         if (hlock->read)
2145                                 usage_bit = LOCK_ENABLED_SOFTIRQS_READ;
2146                         else
2147                                 usage_bit = LOCK_ENABLED_SOFTIRQS;
2148                 }
2149                 if (!mark_lock(curr, hlock, usage_bit))
2150                         return 0;
2151         }
2152
2153         return 1;
2154 }
2155
2156 /*
2157  * Debugging helper: via this flag we know that we are in
2158  * 'early bootup code', and will warn about any invalid irqs-on event:
2159  */
2160 static int early_boot_irqs_enabled;
2161
2162 void early_boot_irqs_off(void)
2163 {
2164         early_boot_irqs_enabled = 0;
2165 }
2166
2167 void early_boot_irqs_on(void)
2168 {
2169         early_boot_irqs_enabled = 1;
2170 }
2171
2172 /*
2173  * Hardirqs will be enabled:
2174  */
2175 void trace_hardirqs_on_caller(unsigned long ip)
2176 {
2177         struct task_struct *curr = current;
2178
2179         time_hardirqs_on(CALLER_ADDR0, ip);
2180
2181         if (unlikely(!debug_locks || current->lockdep_recursion))
2182                 return;
2183
2184         if (DEBUG_LOCKS_WARN_ON(unlikely(!early_boot_irqs_enabled)))
2185                 return;
2186
2187         if (unlikely(curr->hardirqs_enabled)) {
2188                 debug_atomic_inc(&redundant_hardirqs_on);
2189                 return;
2190         }
2191         /* we'll do an OFF -> ON transition: */
2192         curr->hardirqs_enabled = 1;
2193
2194         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2195                 return;
2196         if (DEBUG_LOCKS_WARN_ON(current->hardirq_context))
2197                 return;
2198         /*
2199          * We are going to turn hardirqs on, so set the
2200          * usage bit for all held locks:
2201          */
2202         if (!mark_held_locks(curr, 1))
2203                 return;
2204         /*
2205          * If we have softirqs enabled, then set the usage
2206          * bit for all held locks. (disabled hardirqs prevented
2207          * this bit from being set before)
2208          */
2209         if (curr->softirqs_enabled)
2210                 if (!mark_held_locks(curr, 0))
2211                         return;
2212
2213         curr->hardirq_enable_ip = ip;
2214         curr->hardirq_enable_event = ++curr->irq_events;
2215         debug_atomic_inc(&hardirqs_on_events);
2216 }
2217 EXPORT_SYMBOL(trace_hardirqs_on_caller);
2218
2219 void trace_hardirqs_on(void)
2220 {
2221         trace_hardirqs_on_caller(CALLER_ADDR0);
2222 }
2223 EXPORT_SYMBOL(trace_hardirqs_on);
2224
2225 /*
2226  * Hardirqs were disabled:
2227  */
2228 void trace_hardirqs_off_caller(unsigned long ip)
2229 {
2230         struct task_struct *curr = current;
2231
2232         time_hardirqs_off(CALLER_ADDR0, ip);
2233
2234         if (unlikely(!debug_locks || current->lockdep_recursion))
2235                 return;
2236
2237         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2238                 return;
2239
2240         if (curr->hardirqs_enabled) {
2241                 /*
2242                  * We have done an ON -> OFF transition:
2243                  */
2244                 curr->hardirqs_enabled = 0;
2245                 curr->hardirq_disable_ip = ip;
2246                 curr->hardirq_disable_event = ++curr->irq_events;
2247                 debug_atomic_inc(&hardirqs_off_events);
2248         } else
2249                 debug_atomic_inc(&redundant_hardirqs_off);
2250 }
2251 EXPORT_SYMBOL(trace_hardirqs_off_caller);
2252
2253 void trace_hardirqs_off(void)
2254 {
2255         trace_hardirqs_off_caller(CALLER_ADDR0);
2256 }
2257 EXPORT_SYMBOL(trace_hardirqs_off);
2258
2259 /*
2260  * Softirqs will be enabled:
2261  */
2262 void trace_softirqs_on(unsigned long ip)
2263 {
2264         struct task_struct *curr = current;
2265
2266         if (unlikely(!debug_locks))
2267                 return;
2268
2269         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2270                 return;
2271
2272         if (curr->softirqs_enabled) {
2273                 debug_atomic_inc(&redundant_softirqs_on);
2274                 return;
2275         }
2276
2277         /*
2278          * We'll do an OFF -> ON transition:
2279          */
2280         curr->softirqs_enabled = 1;
2281         curr->softirq_enable_ip = ip;
2282         curr->softirq_enable_event = ++curr->irq_events;
2283         debug_atomic_inc(&softirqs_on_events);
2284         /*
2285          * We are going to turn softirqs on, so set the
2286          * usage bit for all held locks, if hardirqs are
2287          * enabled too:
2288          */
2289         if (curr->hardirqs_enabled)
2290                 mark_held_locks(curr, 0);
2291 }
2292
2293 /*
2294  * Softirqs were disabled:
2295  */
2296 void trace_softirqs_off(unsigned long ip)
2297 {
2298         struct task_struct *curr = current;
2299
2300         if (unlikely(!debug_locks))
2301                 return;
2302
2303         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2304                 return;
2305
2306         if (curr->softirqs_enabled) {
2307                 /*
2308                  * We have done an ON -> OFF transition:
2309                  */
2310                 curr->softirqs_enabled = 0;
2311                 curr->softirq_disable_ip = ip;
2312                 curr->softirq_disable_event = ++curr->irq_events;
2313                 debug_atomic_inc(&softirqs_off_events);
2314                 DEBUG_LOCKS_WARN_ON(!softirq_count());
2315         } else
2316                 debug_atomic_inc(&redundant_softirqs_off);
2317 }
2318
2319 static int mark_irqflags(struct task_struct *curr, struct held_lock *hlock)
2320 {
2321         /*
2322          * If non-trylock use in a hardirq or softirq context, then
2323          * mark the lock as used in these contexts:
2324          */
2325         if (!hlock->trylock) {
2326                 if (hlock->read) {
2327                         if (curr->hardirq_context)
2328                                 if (!mark_lock(curr, hlock,
2329                                                 LOCK_USED_IN_HARDIRQ_READ))
2330                                         return 0;
2331                         if (curr->softirq_context)
2332                                 if (!mark_lock(curr, hlock,
2333                                                 LOCK_USED_IN_SOFTIRQ_READ))
2334                                         return 0;
2335                 } else {
2336                         if (curr->hardirq_context)
2337                                 if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ))
2338                                         return 0;
2339                         if (curr->softirq_context)
2340                                 if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ))
2341                                         return 0;
2342                 }
2343         }
2344         if (!hlock->hardirqs_off) {
2345                 if (hlock->read) {
2346                         if (!mark_lock(curr, hlock,
2347                                         LOCK_ENABLED_HARDIRQS_READ))
2348                                 return 0;
2349                         if (curr->softirqs_enabled)
2350                                 if (!mark_lock(curr, hlock,
2351                                                 LOCK_ENABLED_SOFTIRQS_READ))
2352                                         return 0;
2353                 } else {
2354                         if (!mark_lock(curr, hlock,
2355                                         LOCK_ENABLED_HARDIRQS))
2356                                 return 0;
2357                         if (curr->softirqs_enabled)
2358                                 if (!mark_lock(curr, hlock,
2359                                                 LOCK_ENABLED_SOFTIRQS))
2360                                         return 0;
2361                 }
2362         }
2363
2364         return 1;
2365 }
2366
2367 static int separate_irq_context(struct task_struct *curr,
2368                 struct held_lock *hlock)
2369 {
2370         unsigned int depth = curr->lockdep_depth;
2371
2372         /*
2373          * Keep track of points where we cross into an interrupt context:
2374          */
2375         hlock->irq_context = 2*(curr->hardirq_context ? 1 : 0) +
2376                                 curr->softirq_context;
2377         if (depth) {
2378                 struct held_lock *prev_hlock;
2379
2380                 prev_hlock = curr->held_locks + depth-1;
2381                 /*
2382                  * If we cross into another context, reset the
2383                  * hash key (this also prevents the checking and the
2384                  * adding of the dependency to 'prev'):
2385                  */
2386                 if (prev_hlock->irq_context != hlock->irq_context)
2387                         return 1;
2388         }
2389         return 0;
2390 }
2391
2392 #else
2393
2394 static inline
2395 int mark_lock_irq(struct task_struct *curr, struct held_lock *this,
2396                 enum lock_usage_bit new_bit)
2397 {
2398         WARN_ON(1);
2399         return 1;
2400 }
2401
2402 static inline int mark_irqflags(struct task_struct *curr,
2403                 struct held_lock *hlock)
2404 {
2405         return 1;
2406 }
2407
2408 static inline int separate_irq_context(struct task_struct *curr,
2409                 struct held_lock *hlock)
2410 {
2411         return 0;
2412 }
2413
2414 #endif
2415
2416 /*
2417  * Mark a lock with a usage bit, and validate the state transition:
2418  */
2419 static int mark_lock(struct task_struct *curr, struct held_lock *this,
2420                              enum lock_usage_bit new_bit)
2421 {
2422         unsigned int new_mask = 1 << new_bit, ret = 1;
2423
2424         /*
2425          * If already set then do not dirty the cacheline,
2426          * nor do any checks:
2427          */
2428         if (likely(hlock_class(this)->usage_mask & new_mask))
2429                 return 1;
2430
2431         if (!graph_lock())
2432                 return 0;
2433         /*
2434          * Make sure we didnt race:
2435          */
2436         if (unlikely(hlock_class(this)->usage_mask & new_mask)) {
2437                 graph_unlock();
2438                 return 1;
2439         }
2440
2441         hlock_class(this)->usage_mask |= new_mask;
2442
2443         if (!save_trace(hlock_class(this)->usage_traces + new_bit))
2444                 return 0;
2445
2446         switch (new_bit) {
2447         case LOCK_USED_IN_HARDIRQ:
2448         case LOCK_USED_IN_SOFTIRQ:
2449         case LOCK_USED_IN_HARDIRQ_READ:
2450         case LOCK_USED_IN_SOFTIRQ_READ:
2451         case LOCK_ENABLED_HARDIRQS:
2452         case LOCK_ENABLED_SOFTIRQS:
2453         case LOCK_ENABLED_HARDIRQS_READ:
2454         case LOCK_ENABLED_SOFTIRQS_READ:
2455                 ret = mark_lock_irq(curr, this, new_bit);
2456                 if (!ret)
2457                         return 0;
2458                 break;
2459         case LOCK_USED:
2460                 debug_atomic_dec(&nr_unused_locks);
2461                 break;
2462         default:
2463                 if (!debug_locks_off_graph_unlock())
2464                         return 0;
2465                 WARN_ON(1);
2466                 return 0;
2467         }
2468
2469         graph_unlock();
2470
2471         /*
2472          * We must printk outside of the graph_lock:
2473          */
2474         if (ret == 2) {
2475                 printk("\nmarked lock as {%s}:\n", usage_str[new_bit]);
2476                 print_lock(this);
2477                 print_irqtrace_events(curr);
2478                 dump_stack();
2479         }
2480
2481         return ret;
2482 }
2483
2484 /*
2485  * Initialize a lock instance's lock-class mapping info:
2486  */
2487 void lockdep_init_map(struct lockdep_map *lock, const char *name,
2488                       struct lock_class_key *key, int subclass)
2489 {
2490         if (unlikely(!debug_locks))
2491                 return;
2492
2493         if (DEBUG_LOCKS_WARN_ON(!key))
2494                 return;
2495         if (DEBUG_LOCKS_WARN_ON(!name))
2496                 return;
2497         /*
2498          * Sanity check, the lock-class key must be persistent:
2499          */
2500         if (!static_obj(key)) {
2501                 printk("BUG: key %p not in .data!\n", key);
2502                 DEBUG_LOCKS_WARN_ON(1);
2503                 return;
2504         }
2505         lock->name = name;
2506         lock->key = key;
2507         lock->class_cache = NULL;
2508 #ifdef CONFIG_LOCK_STAT
2509         lock->cpu = raw_smp_processor_id();
2510 #endif
2511         if (subclass)
2512                 register_lock_class(lock, subclass, 1);
2513 }
2514 EXPORT_SYMBOL_GPL(lockdep_init_map);
2515
2516 /*
2517  * This gets called for every mutex_lock*()/spin_lock*() operation.
2518  * We maintain the dependency maps and validate the locking attempt:
2519  */
2520 static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
2521                           int trylock, int read, int check, int hardirqs_off,
2522                           struct lockdep_map *nest_lock, unsigned long ip)
2523 {
2524         struct task_struct *curr = current;
2525         struct lock_class *class = NULL;
2526         struct held_lock *hlock;
2527         unsigned int depth, id;
2528         int chain_head = 0;
2529         u64 chain_key;
2530
2531         if (!prove_locking)
2532                 check = 1;
2533
2534         if (unlikely(!debug_locks))
2535                 return 0;
2536
2537         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2538                 return 0;
2539
2540         if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
2541                 debug_locks_off();
2542                 printk("BUG: MAX_LOCKDEP_SUBCLASSES too low!\n");
2543                 printk("turning off the locking correctness validator.\n");
2544                 return 0;
2545         }
2546
2547         if (!subclass)
2548                 class = lock->class_cache;
2549         /*
2550          * Not cached yet or subclass?
2551          */
2552         if (unlikely(!class)) {
2553                 class = register_lock_class(lock, subclass, 0);
2554                 if (!class)
2555                         return 0;
2556         }
2557         debug_atomic_inc((atomic_t *)&class->ops);
2558         if (very_verbose(class)) {
2559                 printk("\nacquire class [%p] %s", class->key, class->name);
2560                 if (class->name_version > 1)
2561                         printk("#%d", class->name_version);
2562                 printk("\n");
2563                 dump_stack();
2564         }
2565
2566         /*
2567          * Add the lock to the list of currently held locks.
2568          * (we dont increase the depth just yet, up until the
2569          * dependency checks are done)
2570          */
2571         depth = curr->lockdep_depth;
2572         if (DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH))
2573                 return 0;
2574
2575         hlock = curr->held_locks + depth;
2576         if (DEBUG_LOCKS_WARN_ON(!class))
2577                 return 0;
2578         hlock->class_idx = class - lock_classes + 1;
2579         hlock->acquire_ip = ip;
2580         hlock->instance = lock;
2581         hlock->nest_lock = nest_lock;
2582         hlock->trylock = trylock;
2583         hlock->read = read;
2584         hlock->check = check;
2585         hlock->hardirqs_off = !!hardirqs_off;
2586 #ifdef CONFIG_LOCK_STAT
2587         hlock->waittime_stamp = 0;
2588         hlock->holdtime_stamp = sched_clock();
2589 #endif
2590
2591         if (check == 2 && !mark_irqflags(curr, hlock))
2592                 return 0;
2593
2594         /* mark it as used: */
2595         if (!mark_lock(curr, hlock, LOCK_USED))
2596                 return 0;
2597
2598         /*
2599          * Calculate the chain hash: it's the combined hash of all the
2600          * lock keys along the dependency chain. We save the hash value
2601          * at every step so that we can get the current hash easily
2602          * after unlock. The chain hash is then used to cache dependency
2603          * results.
2604          *
2605          * The 'key ID' is what is the most compact key value to drive
2606          * the hash, not class->key.
2607          */
2608         id = class - lock_classes;
2609         if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
2610                 return 0;
2611
2612         chain_key = curr->curr_chain_key;
2613         if (!depth) {
2614                 if (DEBUG_LOCKS_WARN_ON(chain_key != 0))
2615                         return 0;
2616                 chain_head = 1;
2617         }
2618
2619         hlock->prev_chain_key = chain_key;
2620         if (separate_irq_context(curr, hlock)) {
2621                 chain_key = 0;
2622                 chain_head = 1;
2623         }
2624         chain_key = iterate_chain_key(chain_key, id);
2625
2626         if (!validate_chain(curr, lock, hlock, chain_head, chain_key))
2627                 return 0;
2628
2629         curr->curr_chain_key = chain_key;
2630         curr->lockdep_depth++;
2631         check_chain_key(curr);
2632 #ifdef CONFIG_DEBUG_LOCKDEP
2633         if (unlikely(!debug_locks))
2634                 return 0;
2635 #endif
2636         if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
2637                 debug_locks_off();
2638                 printk("BUG: MAX_LOCK_DEPTH too low!\n");
2639                 printk("turning off the locking correctness validator.\n");
2640                 return 0;
2641         }
2642
2643         if (unlikely(curr->lockdep_depth > max_lockdep_depth))
2644                 max_lockdep_depth = curr->lockdep_depth;
2645
2646         return 1;
2647 }
2648
2649 static int
2650 print_unlock_inbalance_bug(struct task_struct *curr, struct lockdep_map *lock,
2651                            unsigned long ip)
2652 {
2653         if (!debug_locks_off())
2654                 return 0;
2655         if (debug_locks_silent)
2656                 return 0;
2657
2658         printk("\n=====================================\n");
2659         printk(  "[ BUG: bad unlock balance detected! ]\n");
2660         printk(  "-------------------------------------\n");
2661         printk("%s/%d is trying to release lock (",
2662                 curr->comm, task_pid_nr(curr));
2663         print_lockdep_cache(lock);
2664         printk(") at:\n");
2665         print_ip_sym(ip);
2666         printk("but there are no more locks to release!\n");
2667         printk("\nother info that might help us debug this:\n");
2668         lockdep_print_held_locks(curr);
2669
2670         printk("\nstack backtrace:\n");
2671         dump_stack();
2672
2673         return 0;
2674 }
2675
2676 /*
2677  * Common debugging checks for both nested and non-nested unlock:
2678  */
2679 static int check_unlock(struct task_struct *curr, struct lockdep_map *lock,
2680                         unsigned long ip)
2681 {
2682         if (unlikely(!debug_locks))
2683                 return 0;
2684         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2685                 return 0;
2686
2687         if (curr->lockdep_depth <= 0)
2688                 return print_unlock_inbalance_bug(curr, lock, ip);
2689
2690         return 1;
2691 }
2692
2693 static int
2694 __lock_set_class(struct lockdep_map *lock, const char *name,
2695                  struct lock_class_key *key, unsigned int subclass,
2696                  unsigned long ip)
2697 {
2698         struct task_struct *curr = current;
2699         struct held_lock *hlock, *prev_hlock;
2700         struct lock_class *class;
2701         unsigned int depth;
2702         int i;
2703
2704         depth = curr->lockdep_depth;
2705         if (DEBUG_LOCKS_WARN_ON(!depth))
2706                 return 0;
2707
2708         prev_hlock = NULL;
2709         for (i = depth-1; i >= 0; i--) {
2710                 hlock = curr->held_locks + i;
2711                 /*
2712                  * We must not cross into another context:
2713                  */
2714                 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
2715                         break;
2716                 if (hlock->instance == lock)
2717                         goto found_it;
2718                 prev_hlock = hlock;
2719         }
2720         return print_unlock_inbalance_bug(curr, lock, ip);
2721
2722 found_it:
2723         lockdep_init_map(lock, name, key, 0);
2724         class = register_lock_class(lock, subclass, 0);
2725         hlock->class_idx = class - lock_classes + 1;
2726
2727         curr->lockdep_depth = i;
2728         curr->curr_chain_key = hlock->prev_chain_key;
2729
2730         for (; i < depth; i++) {
2731                 hlock = curr->held_locks + i;
2732                 if (!__lock_acquire(hlock->instance,
2733                         hlock_class(hlock)->subclass, hlock->trylock,
2734                                 hlock->read, hlock->check, hlock->hardirqs_off,
2735                                 hlock->nest_lock, hlock->acquire_ip))
2736                         return 0;
2737         }
2738
2739         if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth))
2740                 return 0;
2741         return 1;
2742 }
2743
2744 /*
2745  * Remove the lock to the list of currently held locks in a
2746  * potentially non-nested (out of order) manner. This is a
2747  * relatively rare operation, as all the unlock APIs default
2748  * to nested mode (which uses lock_release()):
2749  */
2750 static int
2751 lock_release_non_nested(struct task_struct *curr,
2752                         struct lockdep_map *lock, unsigned long ip)
2753 {
2754         struct held_lock *hlock, *prev_hlock;
2755         unsigned int depth;
2756         int i;
2757
2758         /*
2759          * Check whether the lock exists in the current stack
2760          * of held locks:
2761          */
2762         depth = curr->lockdep_depth;
2763         if (DEBUG_LOCKS_WARN_ON(!depth))
2764                 return 0;
2765
2766         prev_hlock = NULL;
2767         for (i = depth-1; i >= 0; i--) {
2768                 hlock = curr->held_locks + i;
2769                 /*
2770                  * We must not cross into another context:
2771                  */
2772                 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
2773                         break;
2774                 if (hlock->instance == lock)
2775                         goto found_it;
2776                 prev_hlock = hlock;
2777         }
2778         return print_unlock_inbalance_bug(curr, lock, ip);
2779
2780 found_it:
2781         lock_release_holdtime(hlock);
2782
2783         /*
2784          * We have the right lock to unlock, 'hlock' points to it.
2785          * Now we remove it from the stack, and add back the other
2786          * entries (if any), recalculating the hash along the way:
2787          */
2788         curr->lockdep_depth = i;
2789         curr->curr_chain_key = hlock->prev_chain_key;
2790
2791         for (i++; i < depth; i++) {
2792                 hlock = curr->held_locks + i;
2793                 if (!__lock_acquire(hlock->instance,
2794                         hlock_class(hlock)->subclass, hlock->trylock,
2795                                 hlock->read, hlock->check, hlock->hardirqs_off,
2796                                 hlock->nest_lock, hlock->acquire_ip))
2797                         return 0;
2798         }
2799
2800         if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - 1))
2801                 return 0;
2802         return 1;
2803 }
2804
2805 /*
2806  * Remove the lock to the list of currently held locks - this gets
2807  * called on mutex_unlock()/spin_unlock*() (or on a failed
2808  * mutex_lock_interruptible()). This is done for unlocks that nest
2809  * perfectly. (i.e. the current top of the lock-stack is unlocked)
2810  */
2811 static int lock_release_nested(struct task_struct *curr,
2812                                struct lockdep_map *lock, unsigned long ip)
2813 {
2814         struct held_lock *hlock;
2815         unsigned int depth;
2816
2817         /*
2818          * Pop off the top of the lock stack:
2819          */
2820         depth = curr->lockdep_depth - 1;
2821         hlock = curr->held_locks + depth;
2822
2823         /*
2824          * Is the unlock non-nested:
2825          */
2826         if (hlock->instance != lock)
2827                 return lock_release_non_nested(curr, lock, ip);
2828         curr->lockdep_depth--;
2829
2830         if (DEBUG_LOCKS_WARN_ON(!depth && (hlock->prev_chain_key != 0)))
2831                 return 0;
2832
2833         curr->curr_chain_key = hlock->prev_chain_key;
2834
2835         lock_release_holdtime(hlock);
2836
2837 #ifdef CONFIG_DEBUG_LOCKDEP
2838         hlock->prev_chain_key = 0;
2839         hlock->class_idx = 0;
2840         hlock->acquire_ip = 0;
2841         hlock->irq_context = 0;
2842 #endif
2843         return 1;
2844 }
2845
2846 /*
2847  * Remove the lock to the list of currently held locks - this gets
2848  * called on mutex_unlock()/spin_unlock*() (or on a failed
2849  * mutex_lock_interruptible()). This is done for unlocks that nest
2850  * perfectly. (i.e. the current top of the lock-stack is unlocked)
2851  */
2852 static void
2853 __lock_release(struct lockdep_map *lock, int nested, unsigned long ip)
2854 {
2855         struct task_struct *curr = current;
2856
2857         if (!check_unlock(curr, lock, ip))
2858                 return;
2859
2860         if (nested) {
2861                 if (!lock_release_nested(curr, lock, ip))
2862                         return;
2863         } else {
2864                 if (!lock_release_non_nested(curr, lock, ip))
2865                         return;
2866         }
2867
2868         check_chain_key(curr);
2869 }
2870
2871 /*
2872  * Check whether we follow the irq-flags state precisely:
2873  */
2874 static void check_flags(unsigned long flags)
2875 {
2876 #if defined(CONFIG_PROVE_LOCKING) && defined(CONFIG_DEBUG_LOCKDEP) && \
2877     defined(CONFIG_TRACE_IRQFLAGS)
2878         if (!debug_locks)
2879                 return;
2880
2881         if (irqs_disabled_flags(flags)) {
2882                 if (DEBUG_LOCKS_WARN_ON(current->hardirqs_enabled)) {
2883                         printk("possible reason: unannotated irqs-off.\n");
2884                 }
2885         } else {
2886                 if (DEBUG_LOCKS_WARN_ON(!current->hardirqs_enabled)) {
2887                         printk("possible reason: unannotated irqs-on.\n");
2888                 }
2889         }
2890
2891         /*
2892          * We dont accurately track softirq state in e.g.
2893          * hardirq contexts (such as on 4KSTACKS), so only
2894          * check if not in hardirq contexts:
2895          */
2896         if (!hardirq_count()) {
2897                 if (softirq_count())
2898                         DEBUG_LOCKS_WARN_ON(current->softirqs_enabled);
2899                 else
2900                         DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled);
2901         }
2902
2903         if (!debug_locks)
2904                 print_irqtrace_events(current);
2905 #endif
2906 }
2907
2908 void lock_set_class(struct lockdep_map *lock, const char *name,
2909                     struct lock_class_key *key, unsigned int subclass,
2910                     unsigned long ip)
2911 {
2912         unsigned long flags;
2913
2914         if (unlikely(current->lockdep_recursion))
2915                 return;
2916
2917         raw_local_irq_save(flags);
2918         current->lockdep_recursion = 1;
2919         check_flags(flags);
2920         if (__lock_set_class(lock, name, key, subclass, ip))
2921                 check_chain_key(current);
2922         current->lockdep_recursion = 0;
2923         raw_local_irq_restore(flags);
2924 }
2925 EXPORT_SYMBOL_GPL(lock_set_class);
2926
2927 /*
2928  * We are not always called with irqs disabled - do that here,
2929  * and also avoid lockdep recursion:
2930  */
2931 void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
2932                           int trylock, int read, int check,
2933                           struct lockdep_map *nest_lock, unsigned long ip)
2934 {
2935         unsigned long flags;
2936
2937         if (unlikely(current->lockdep_recursion))
2938                 return;
2939
2940         raw_local_irq_save(flags);
2941         check_flags(flags);
2942
2943         current->lockdep_recursion = 1;
2944         __lock_acquire(lock, subclass, trylock, read, check,
2945                        irqs_disabled_flags(flags), nest_lock, ip);
2946         current->lockdep_recursion = 0;
2947         raw_local_irq_restore(flags);
2948 }
2949 EXPORT_SYMBOL_GPL(lock_acquire);
2950
2951 void lock_release(struct lockdep_map *lock, int nested,
2952                           unsigned long ip)
2953 {
2954         unsigned long flags;
2955
2956         if (unlikely(current->lockdep_recursion))
2957                 return;
2958
2959         raw_local_irq_save(flags);
2960         check_flags(flags);
2961         current->lockdep_recursion = 1;
2962         __lock_release(lock, nested, ip);
2963         current->lockdep_recursion = 0;
2964         raw_local_irq_restore(flags);
2965 }
2966 EXPORT_SYMBOL_GPL(lock_release);
2967
2968 #ifdef CONFIG_LOCK_STAT
2969 static int
2970 print_lock_contention_bug(struct task_struct *curr, struct lockdep_map *lock,
2971                            unsigned long ip)
2972 {
2973         if (!debug_locks_off())
2974                 return 0;
2975         if (debug_locks_silent)
2976                 return 0;
2977
2978         printk("\n=================================\n");
2979         printk(  "[ BUG: bad contention detected! ]\n");
2980         printk(  "---------------------------------\n");
2981         printk("%s/%d is trying to contend lock (",
2982                 curr->comm, task_pid_nr(curr));
2983         print_lockdep_cache(lock);
2984         printk(") at:\n");
2985         print_ip_sym(ip);
2986         printk("but there are no locks held!\n");
2987         printk("\nother info that might help us debug this:\n");
2988         lockdep_print_held_locks(curr);
2989
2990         printk("\nstack backtrace:\n");
2991         dump_stack();
2992
2993         return 0;
2994 }
2995
2996 static void
2997 __lock_contended(struct lockdep_map *lock, unsigned long ip)
2998 {
2999         struct task_struct *curr = current;
3000         struct held_lock *hlock, *prev_hlock;
3001         struct lock_class_stats *stats;
3002         unsigned int depth;
3003         int i, contention_point, contending_point;
3004
3005         depth = curr->lockdep_depth;
3006         if (DEBUG_LOCKS_WARN_ON(!depth))
3007                 return;
3008
3009         prev_hlock = NULL;
3010         for (i = depth-1; i >= 0; i--) {
3011                 hlock = curr->held_locks + i;
3012                 /*
3013                  * We must not cross into another context:
3014                  */
3015                 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3016                         break;
3017                 if (hlock->instance == lock)
3018                         goto found_it;
3019                 prev_hlock = hlock;
3020         }
3021         print_lock_contention_bug(curr, lock, ip);
3022         return;
3023
3024 found_it:
3025         hlock->waittime_stamp = sched_clock();
3026
3027         contention_point = lock_point(hlock_class(hlock)->contention_point, ip);
3028         contending_point = lock_point(hlock_class(hlock)->contending_point,
3029                                       lock->ip);
3030
3031         stats = get_lock_stats(hlock_class(hlock));
3032         if (contention_point < LOCKSTAT_POINTS)
3033                 stats->contention_point[contention_point]++;
3034         if (contending_point < LOCKSTAT_POINTS)
3035                 stats->contending_point[contending_point]++;
3036         if (lock->cpu != smp_processor_id())
3037                 stats->bounces[bounce_contended + !!hlock->read]++;
3038         put_lock_stats(stats);
3039 }
3040
3041 static void
3042 __lock_acquired(struct lockdep_map *lock, unsigned long ip)
3043 {
3044         struct task_struct *curr = current;
3045         struct held_lock *hlock, *prev_hlock;
3046         struct lock_class_stats *stats;
3047         unsigned int depth;
3048         u64 now;
3049         s64 waittime = 0;
3050         int i, cpu;
3051
3052         depth = curr->lockdep_depth;
3053         if (DEBUG_LOCKS_WARN_ON(!depth))
3054                 return;
3055
3056         prev_hlock = NULL;
3057         for (i = depth-1; i >= 0; i--) {
3058                 hlock = curr->held_locks + i;
3059                 /*
3060                  * We must not cross into another context:
3061                  */
3062                 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3063                         break;
3064                 if (hlock->instance == lock)
3065                         goto found_it;
3066                 prev_hlock = hlock;
3067         }
3068         print_lock_contention_bug(curr, lock, _RET_IP_);
3069         return;
3070
3071 found_it:
3072         cpu = smp_processor_id();
3073         if (hlock->waittime_stamp) {
3074                 now = sched_clock();
3075                 waittime = now - hlock->waittime_stamp;
3076                 hlock->holdtime_stamp = now;
3077         }
3078
3079         stats = get_lock_stats(hlock_class(hlock));
3080         if (waittime) {
3081                 if (hlock->read)
3082                         lock_time_inc(&stats->read_waittime, waittime);
3083                 else
3084                         lock_time_inc(&stats->write_waittime, waittime);
3085         }
3086         if (lock->cpu != cpu)
3087                 stats->bounces[bounce_acquired + !!hlock->read]++;
3088         put_lock_stats(stats);
3089
3090         lock->cpu = cpu;
3091         lock->ip = ip;
3092 }
3093
3094 void lock_contended(struct lockdep_map *lock, unsigned long ip)
3095 {
3096         unsigned long flags;
3097
3098         if (unlikely(!lock_stat))
3099                 return;
3100
3101         if (unlikely(current->lockdep_recursion))
3102                 return;
3103
3104         raw_local_irq_save(flags);
3105         check_flags(flags);
3106         current->lockdep_recursion = 1;
3107         __lock_contended(lock, ip);
3108         current->lockdep_recursion = 0;
3109         raw_local_irq_restore(flags);
3110 }
3111 EXPORT_SYMBOL_GPL(lock_contended);
3112
3113 void lock_acquired(struct lockdep_map *lock, unsigned long ip)
3114 {
3115         unsigned long flags;
3116
3117         if (unlikely(!lock_stat))
3118                 return;
3119
3120         if (unlikely(current->lockdep_recursion))
3121                 return;
3122
3123         raw_local_irq_save(flags);
3124         check_flags(flags);
3125         current->lockdep_recursion = 1;
3126         __lock_acquired(lock, ip);
3127         current->lockdep_recursion = 0;
3128         raw_local_irq_restore(flags);
3129 }
3130 EXPORT_SYMBOL_GPL(lock_acquired);
3131 #endif
3132
3133 /*
3134  * Used by the testsuite, sanitize the validator state
3135  * after a simulated failure:
3136  */
3137
3138 void lockdep_reset(void)
3139 {
3140         unsigned long flags;
3141         int i;
3142
3143         raw_local_irq_save(flags);
3144         current->curr_chain_key = 0;
3145         current->lockdep_depth = 0;
3146         current->lockdep_recursion = 0;
3147         memset(current->held_locks, 0, MAX_LOCK_DEPTH*sizeof(struct held_lock));
3148         nr_hardirq_chains = 0;
3149         nr_softirq_chains = 0;
3150         nr_process_chains = 0;
3151         debug_locks = 1;
3152         for (i = 0; i < CHAINHASH_SIZE; i++)
3153                 INIT_LIST_HEAD(chainhash_table + i);
3154         raw_local_irq_restore(flags);
3155 }
3156
3157 static void zap_class(struct lock_class *class)
3158 {
3159         int i;
3160
3161         /*
3162          * Remove all dependencies this lock is
3163          * involved in:
3164          */
3165         for (i = 0; i < nr_list_entries; i++) {
3166                 if (list_entries[i].class == class)
3167                         list_del_rcu(&list_entries[i].entry);
3168         }
3169         /*
3170          * Unhash the class and remove it from the all_lock_classes list:
3171          */
3172         list_del_rcu(&class->hash_entry);
3173         list_del_rcu(&class->lock_entry);
3174
3175         class->key = NULL;
3176 }
3177
3178 static inline int within(const void *addr, void *start, unsigned long size)
3179 {
3180         return addr >= start && addr < start + size;
3181 }
3182
3183 void lockdep_free_key_range(void *start, unsigned long size)
3184 {
3185         struct lock_class *class, *next;
3186         struct list_head *head;
3187         unsigned long flags;
3188         int i;
3189         int locked;
3190
3191         raw_local_irq_save(flags);
3192         locked = graph_lock();
3193
3194         /*
3195          * Unhash all classes that were created by this module:
3196          */
3197         for (i = 0; i < CLASSHASH_SIZE; i++) {
3198                 head = classhash_table + i;
3199                 if (list_empty(head))
3200                         continue;
3201                 list_for_each_entry_safe(class, next, head, hash_entry) {
3202                         if (within(class->key, start, size))
3203                                 zap_class(class);
3204                         else if (within(class->name, start, size))
3205                                 zap_class(class);
3206                 }
3207         }
3208
3209         if (locked)
3210                 graph_unlock();
3211         raw_local_irq_restore(flags);
3212 }
3213
3214 void lockdep_reset_lock(struct lockdep_map *lock)
3215 {
3216         struct lock_class *class, *next;
3217         struct list_head *head;
3218         unsigned long flags;
3219         int i, j;
3220         int locked;
3221
3222         raw_local_irq_save(flags);
3223
3224         /*
3225          * Remove all classes this lock might have:
3226          */
3227         for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) {
3228                 /*
3229                  * If the class exists we look it up and zap it:
3230                  */
3231                 class = look_up_lock_class(lock, j);
3232                 if (class)
3233                         zap_class(class);
3234         }
3235         /*
3236          * Debug check: in the end all mapped classes should
3237          * be gone.
3238          */
3239         locked = graph_lock();
3240         for (i = 0; i < CLASSHASH_SIZE; i++) {
3241                 head = classhash_table + i;
3242                 if (list_empty(head))
3243                         continue;
3244                 list_for_each_entry_safe(class, next, head, hash_entry) {
3245                         if (unlikely(class == lock->class_cache)) {
3246                                 if (debug_locks_off_graph_unlock())
3247                                         WARN_ON(1);
3248                                 goto out_restore;
3249                         }
3250                 }
3251         }
3252         if (locked)
3253                 graph_unlock();
3254
3255 out_restore:
3256         raw_local_irq_restore(flags);
3257 }
3258
3259 void lockdep_init(void)
3260 {
3261         int i;
3262
3263         /*
3264          * Some architectures have their own start_kernel()
3265          * code which calls lockdep_init(), while we also
3266          * call lockdep_init() from the start_kernel() itself,
3267          * and we want to initialize the hashes only once:
3268          */
3269         if (lockdep_initialized)
3270                 return;
3271
3272         for (i = 0; i < CLASSHASH_SIZE; i++)
3273                 INIT_LIST_HEAD(classhash_table + i);
3274
3275         for (i = 0; i < CHAINHASH_SIZE; i++)
3276                 INIT_LIST_HEAD(chainhash_table + i);
3277
3278         lockdep_initialized = 1;
3279 }
3280
3281 void __init lockdep_info(void)
3282 {
3283         printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");
3284
3285         printk("... MAX_LOCKDEP_SUBCLASSES:  %lu\n", MAX_LOCKDEP_SUBCLASSES);
3286         printk("... MAX_LOCK_DEPTH:          %lu\n", MAX_LOCK_DEPTH);
3287         printk("... MAX_LOCKDEP_KEYS:        %lu\n", MAX_LOCKDEP_KEYS);
3288         printk("... CLASSHASH_SIZE:          %lu\n", CLASSHASH_SIZE);
3289         printk("... MAX_LOCKDEP_ENTRIES:     %lu\n", MAX_LOCKDEP_ENTRIES);
3290         printk("... MAX_LOCKDEP_CHAINS:      %lu\n", MAX_LOCKDEP_CHAINS);
3291         printk("... CHAINHASH_SIZE:          %lu\n", CHAINHASH_SIZE);
3292
3293         printk(" memory used by lock dependency info: %lu kB\n",
3294                 (sizeof(struct lock_class) * MAX_LOCKDEP_KEYS +
3295                 sizeof(struct list_head) * CLASSHASH_SIZE +
3296                 sizeof(struct lock_list) * MAX_LOCKDEP_ENTRIES +
3297                 sizeof(struct lock_chain) * MAX_LOCKDEP_CHAINS +
3298                 sizeof(struct list_head) * CHAINHASH_SIZE) / 1024);
3299
3300         printk(" per task-struct memory footprint: %lu bytes\n",
3301                 sizeof(struct held_lock) * MAX_LOCK_DEPTH);
3302
3303 #ifdef CONFIG_DEBUG_LOCKDEP
3304         if (lockdep_init_error) {
3305                 printk("WARNING: lockdep init error! Arch code didn't call lockdep_init() early enough?\n");
3306                 printk("Call stack leading to lockdep invocation was:\n");
3307                 print_stack_trace(&lockdep_init_trace, 0);
3308         }
3309 #endif
3310 }
3311
3312 static void
3313 print_freed_lock_bug(struct task_struct *curr, const void *mem_from,
3314                      const void *mem_to, struct held_lock *hlock)
3315 {
3316         if (!debug_locks_off())
3317                 return;
3318         if (debug_locks_silent)
3319                 return;
3320
3321         printk("\n=========================\n");
3322         printk(  "[ BUG: held lock freed! ]\n");
3323         printk(  "-------------------------\n");
3324         printk("%s/%d is freeing memory %p-%p, with a lock still held there!\n",
3325                 curr->comm, task_pid_nr(curr), mem_from, mem_to-1);
3326         print_lock(hlock);
3327         lockdep_print_held_locks(curr);
3328
3329         printk("\nstack backtrace:\n");
3330         dump_stack();
3331 }
3332
3333 static inline int not_in_range(const void* mem_from, unsigned long mem_len,
3334                                 const void* lock_from, unsigned long lock_len)
3335 {
3336         return lock_from + lock_len <= mem_from ||
3337                 mem_from + mem_len <= lock_from;
3338 }
3339
3340 /*
3341  * Called when kernel memory is freed (or unmapped), or if a lock
3342  * is destroyed or reinitialized - this code checks whether there is
3343  * any held lock in the memory range of <from> to <to>:
3344  */
3345 void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len)
3346 {
3347         struct task_struct *curr = current;
3348         struct held_lock *hlock;
3349         unsigned long flags;
3350         int i;
3351
3352         if (unlikely(!debug_locks))
3353                 return;
3354
3355         local_irq_save(flags);
3356         for (i = 0; i < curr->lockdep_depth; i++) {
3357                 hlock = curr->held_locks + i;
3358
3359                 if (not_in_range(mem_from, mem_len, hlock->instance,
3360                                         sizeof(*hlock->instance)))
3361                         continue;
3362
3363                 print_freed_lock_bug(curr, mem_from, mem_from + mem_len, hlock);
3364                 break;
3365         }
3366         local_irq_restore(flags);
3367 }
3368 EXPORT_SYMBOL_GPL(debug_check_no_locks_freed);
3369
3370 static void print_held_locks_bug(struct task_struct *curr)
3371 {
3372         if (!debug_locks_off())
3373                 return;
3374         if (debug_locks_silent)
3375                 return;
3376
3377         printk("\n=====================================\n");
3378         printk(  "[ BUG: lock held at task exit time! ]\n");
3379         printk(  "-------------------------------------\n");
3380         printk("%s/%d is exiting with locks still held!\n",
3381                 curr->comm, task_pid_nr(curr));
3382         lockdep_print_held_locks(curr);
3383
3384         printk("\nstack backtrace:\n");
3385         dump_stack();
3386 }
3387
3388 void debug_check_no_locks_held(struct task_struct *task)
3389 {
3390         if (unlikely(task->lockdep_depth > 0))
3391                 print_held_locks_bug(task);
3392 }
3393
3394 void debug_show_all_locks(void)
3395 {
3396         struct task_struct *g, *p;
3397         int count = 10;
3398         int unlock = 1;
3399
3400         if (unlikely(!debug_locks)) {
3401                 printk("INFO: lockdep is turned off.\n");
3402                 return;
3403         }
3404         printk("\nShowing all locks held in the system:\n");
3405
3406         /*
3407          * Here we try to get the tasklist_lock as hard as possible,
3408          * if not successful after 2 seconds we ignore it (but keep
3409          * trying). This is to enable a debug printout even if a
3410          * tasklist_lock-holding task deadlocks or crashes.
3411          */
3412 retry:
3413         if (!read_trylock(&tasklist_lock)) {
3414                 if (count == 10)
3415                         printk("hm, tasklist_lock locked, retrying... ");
3416                 if (count) {
3417                         count--;
3418                         printk(" #%d", 10-count);
3419                         mdelay(200);
3420                         goto retry;
3421                 }
3422                 printk(" ignoring it.\n");
3423                 unlock = 0;
3424         } else {
3425                 if (count != 10)
3426                         printk(KERN_CONT " locked it.\n");
3427         }
3428
3429         do_each_thread(g, p) {
3430                 /*
3431                  * It's not reliable to print a task's held locks
3432                  * if it's not sleeping (or if it's not the current
3433                  * task):
3434                  */
3435                 if (p->state == TASK_RUNNING && p != current)
3436                         continue;
3437                 if (p->lockdep_depth)
3438                         lockdep_print_held_locks(p);
3439                 if (!unlock)
3440                         if (read_trylock(&tasklist_lock))
3441                                 unlock = 1;
3442         } while_each_thread(g, p);
3443
3444         printk("\n");
3445         printk("=============================================\n\n");
3446
3447         if (unlock)
3448                 read_unlock(&tasklist_lock);
3449 }
3450 EXPORT_SYMBOL_GPL(debug_show_all_locks);
3451
3452 /*
3453  * Careful: only use this function if you are sure that
3454  * the task cannot run in parallel!
3455  */
3456 void __debug_show_held_locks(struct task_struct *task)
3457 {
3458         if (unlikely(!debug_locks)) {
3459                 printk("INFO: lockdep is turned off.\n");
3460                 return;
3461         }
3462         lockdep_print_held_locks(task);
3463 }
3464 EXPORT_SYMBOL_GPL(__debug_show_held_locks);
3465
3466 void debug_show_held_locks(struct task_struct *task)
3467 {
3468                 __debug_show_held_locks(task);
3469 }
3470 EXPORT_SYMBOL_GPL(debug_show_held_locks);
3471
3472 void lockdep_sys_exit(void)
3473 {
3474         struct task_struct *curr = current;
3475
3476         if (unlikely(curr->lockdep_depth)) {
3477                 if (!debug_locks_off())
3478                         return;
3479                 printk("\n================================================\n");
3480                 printk(  "[ BUG: lock held when returning to user space! ]\n");
3481                 printk(  "------------------------------------------------\n");
3482                 printk("%s/%d is leaving the kernel with locks still held!\n",
3483                                 curr->comm, curr->pid);
3484                 lockdep_print_held_locks(curr);
3485         }
3486 }