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