8dc24c92dc6d2c1e867c8ce381caec43c9408583
[sfrench/cifs-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  * lockdep_lock: protects the lockdep graph, the hashes and the
47  *               class/list/hash allocators.
48  *
49  * This is one of the rare exceptions where it's justified
50  * to use a raw spinlock - we really dont want the spinlock
51  * code to recurse back into the lockdep code...
52  */
53 static raw_spinlock_t lockdep_lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
54
55 static int graph_lock(void)
56 {
57         __raw_spin_lock(&lockdep_lock);
58         /*
59          * Make sure that if another CPU detected a bug while
60          * walking the graph we dont change it (while the other
61          * CPU is busy printing out stuff with the graph lock
62          * dropped already)
63          */
64         if (!debug_locks) {
65                 __raw_spin_unlock(&lockdep_lock);
66                 return 0;
67         }
68         return 1;
69 }
70
71 static inline int graph_unlock(void)
72 {
73         if (debug_locks && !__raw_spin_is_locked(&lockdep_lock))
74                 return DEBUG_LOCKS_WARN_ON(1);
75
76         __raw_spin_unlock(&lockdep_lock);
77         return 0;
78 }
79
80 /*
81  * Turn lock debugging off and return with 0 if it was off already,
82  * and also release the graph lock:
83  */
84 static inline int debug_locks_off_graph_unlock(void)
85 {
86         int ret = debug_locks_off();
87
88         __raw_spin_unlock(&lockdep_lock);
89
90         return ret;
91 }
92
93 static int lockdep_initialized;
94
95 unsigned long nr_list_entries;
96 static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES];
97
98 /*
99  * Allocate a lockdep entry. (assumes the graph_lock held, returns
100  * with NULL on failure)
101  */
102 static struct lock_list *alloc_list_entry(void)
103 {
104         if (nr_list_entries >= MAX_LOCKDEP_ENTRIES) {
105                 if (!debug_locks_off_graph_unlock())
106                         return NULL;
107
108                 printk("BUG: MAX_LOCKDEP_ENTRIES too low!\n");
109                 printk("turning off the locking correctness validator.\n");
110                 return NULL;
111         }
112         return list_entries + nr_list_entries++;
113 }
114
115 /*
116  * All data structures here are protected by the global debug_lock.
117  *
118  * Mutex key structs only get allocated, once during bootup, and never
119  * get freed - this significantly simplifies the debugging code.
120  */
121 unsigned long nr_lock_classes;
122 static struct lock_class lock_classes[MAX_LOCKDEP_KEYS];
123
124 /*
125  * We keep a global list of all lock classes. The list only grows,
126  * never shrinks. The list is only accessed with the lockdep
127  * spinlock lock held.
128  */
129 LIST_HEAD(all_lock_classes);
130
131 /*
132  * The lockdep classes are in a hash-table as well, for fast lookup:
133  */
134 #define CLASSHASH_BITS          (MAX_LOCKDEP_KEYS_BITS - 1)
135 #define CLASSHASH_SIZE          (1UL << CLASSHASH_BITS)
136 #define CLASSHASH_MASK          (CLASSHASH_SIZE - 1)
137 #define __classhashfn(key)      ((((unsigned long)key >> CLASSHASH_BITS) + (unsigned long)key) & CLASSHASH_MASK)
138 #define classhashentry(key)     (classhash_table + __classhashfn((key)))
139
140 static struct list_head classhash_table[CLASSHASH_SIZE];
141
142 unsigned long nr_lock_chains;
143 static struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
144
145 /*
146  * We put the lock dependency chains into a hash-table as well, to cache
147  * their existence:
148  */
149 #define CHAINHASH_BITS          (MAX_LOCKDEP_CHAINS_BITS-1)
150 #define CHAINHASH_SIZE          (1UL << CHAINHASH_BITS)
151 #define CHAINHASH_MASK          (CHAINHASH_SIZE - 1)
152 #define __chainhashfn(chain) \
153                 (((chain >> CHAINHASH_BITS) + chain) & CHAINHASH_MASK)
154 #define chainhashentry(chain)   (chainhash_table + __chainhashfn((chain)))
155
156 static struct list_head chainhash_table[CHAINHASH_SIZE];
157
158 /*
159  * The hash key of the lock dependency chains is a hash itself too:
160  * it's a hash of all locks taken up to that lock, including that lock.
161  * It's a 64-bit hash, because it's important for the keys to be
162  * unique.
163  */
164 #define iterate_chain_key(key1, key2) \
165         (((key1) << MAX_LOCKDEP_KEYS_BITS) ^ \
166         ((key1) >> (64-MAX_LOCKDEP_KEYS_BITS)) ^ \
167         (key2))
168
169 void lockdep_off(void)
170 {
171         current->lockdep_recursion++;
172 }
173
174 EXPORT_SYMBOL(lockdep_off);
175
176 void lockdep_on(void)
177 {
178         current->lockdep_recursion--;
179 }
180
181 EXPORT_SYMBOL(lockdep_on);
182
183 /*
184  * Debugging switches:
185  */
186
187 #define VERBOSE                 0
188 #define VERY_VERBOSE            0
189
190 #if VERBOSE
191 # define HARDIRQ_VERBOSE        1
192 # define SOFTIRQ_VERBOSE        1
193 #else
194 # define HARDIRQ_VERBOSE        0
195 # define SOFTIRQ_VERBOSE        0
196 #endif
197
198 #if VERBOSE || HARDIRQ_VERBOSE || SOFTIRQ_VERBOSE
199 /*
200  * Quick filtering for interesting events:
201  */
202 static int class_filter(struct lock_class *class)
203 {
204 #if 0
205         /* Example */
206         if (class->name_version == 1 &&
207                         !strcmp(class->name, "lockname"))
208                 return 1;
209         if (class->name_version == 1 &&
210                         !strcmp(class->name, "&struct->lockfield"))
211                 return 1;
212 #endif
213         /* Filter everything else. 1 would be to allow everything else */
214         return 0;
215 }
216 #endif
217
218 static int verbose(struct lock_class *class)
219 {
220 #if VERBOSE
221         return class_filter(class);
222 #endif
223         return 0;
224 }
225
226 #ifdef CONFIG_TRACE_IRQFLAGS
227
228 static int hardirq_verbose(struct lock_class *class)
229 {
230 #if HARDIRQ_VERBOSE
231         return class_filter(class);
232 #endif
233         return 0;
234 }
235
236 static int softirq_verbose(struct lock_class *class)
237 {
238 #if SOFTIRQ_VERBOSE
239         return class_filter(class);
240 #endif
241         return 0;
242 }
243
244 #endif
245
246 /*
247  * Stack-trace: tightly packed array of stack backtrace
248  * addresses. Protected by the graph_lock.
249  */
250 unsigned long nr_stack_trace_entries;
251 static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];
252
253 static int save_trace(struct stack_trace *trace)
254 {
255         trace->nr_entries = 0;
256         trace->max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries;
257         trace->entries = stack_trace + nr_stack_trace_entries;
258
259         trace->skip = 3;
260         trace->all_contexts = 0;
261
262         save_stack_trace(trace, NULL);
263
264         trace->max_entries = trace->nr_entries;
265
266         nr_stack_trace_entries += trace->nr_entries;
267
268         if (nr_stack_trace_entries == MAX_STACK_TRACE_ENTRIES) {
269                 if (!debug_locks_off_graph_unlock())
270                         return 0;
271
272                 printk("BUG: MAX_STACK_TRACE_ENTRIES too low!\n");
273                 printk("turning off the locking correctness validator.\n");
274                 dump_stack();
275
276                 return 0;
277         }
278
279         return 1;
280 }
281
282 unsigned int nr_hardirq_chains;
283 unsigned int nr_softirq_chains;
284 unsigned int nr_process_chains;
285 unsigned int max_lockdep_depth;
286 unsigned int max_recursion_depth;
287
288 #ifdef CONFIG_DEBUG_LOCKDEP
289 /*
290  * We cannot printk in early bootup code. Not even early_printk()
291  * might work. So we mark any initialization errors and printk
292  * about it later on, in lockdep_info().
293  */
294 static int lockdep_init_error;
295
296 /*
297  * Various lockdep statistics:
298  */
299 atomic_t chain_lookup_hits;
300 atomic_t chain_lookup_misses;
301 atomic_t hardirqs_on_events;
302 atomic_t hardirqs_off_events;
303 atomic_t redundant_hardirqs_on;
304 atomic_t redundant_hardirqs_off;
305 atomic_t softirqs_on_events;
306 atomic_t softirqs_off_events;
307 atomic_t redundant_softirqs_on;
308 atomic_t redundant_softirqs_off;
309 atomic_t nr_unused_locks;
310 atomic_t nr_cyclic_checks;
311 atomic_t nr_cyclic_check_recursions;
312 atomic_t nr_find_usage_forwards_checks;
313 atomic_t nr_find_usage_forwards_recursions;
314 atomic_t nr_find_usage_backwards_checks;
315 atomic_t nr_find_usage_backwards_recursions;
316 # define debug_atomic_inc(ptr)          atomic_inc(ptr)
317 # define debug_atomic_dec(ptr)          atomic_dec(ptr)
318 # define debug_atomic_read(ptr)         atomic_read(ptr)
319 #else
320 # define debug_atomic_inc(ptr)          do { } while (0)
321 # define debug_atomic_dec(ptr)          do { } while (0)
322 # define debug_atomic_read(ptr)         0
323 #endif
324
325 /*
326  * Locking printouts:
327  */
328
329 static const char *usage_str[] =
330 {
331         [LOCK_USED] =                   "initial-use ",
332         [LOCK_USED_IN_HARDIRQ] =        "in-hardirq-W",
333         [LOCK_USED_IN_SOFTIRQ] =        "in-softirq-W",
334         [LOCK_ENABLED_SOFTIRQS] =       "softirq-on-W",
335         [LOCK_ENABLED_HARDIRQS] =       "hardirq-on-W",
336         [LOCK_USED_IN_HARDIRQ_READ] =   "in-hardirq-R",
337         [LOCK_USED_IN_SOFTIRQ_READ] =   "in-softirq-R",
338         [LOCK_ENABLED_SOFTIRQS_READ] =  "softirq-on-R",
339         [LOCK_ENABLED_HARDIRQS_READ] =  "hardirq-on-R",
340 };
341
342 const char * __get_key_name(struct lockdep_subclass_key *key, char *str)
343 {
344         unsigned long offs, size;
345         char *modname;
346
347         return kallsyms_lookup((unsigned long)key, &size, &offs, &modname, str);
348 }
349
350 void
351 get_usage_chars(struct lock_class *class, char *c1, char *c2, char *c3, char *c4)
352 {
353         *c1 = '.', *c2 = '.', *c3 = '.', *c4 = '.';
354
355         if (class->usage_mask & LOCKF_USED_IN_HARDIRQ)
356                 *c1 = '+';
357         else
358                 if (class->usage_mask & LOCKF_ENABLED_HARDIRQS)
359                         *c1 = '-';
360
361         if (class->usage_mask & LOCKF_USED_IN_SOFTIRQ)
362                 *c2 = '+';
363         else
364                 if (class->usage_mask & LOCKF_ENABLED_SOFTIRQS)
365                         *c2 = '-';
366
367         if (class->usage_mask & LOCKF_ENABLED_HARDIRQS_READ)
368                 *c3 = '-';
369         if (class->usage_mask & LOCKF_USED_IN_HARDIRQ_READ) {
370                 *c3 = '+';
371                 if (class->usage_mask & LOCKF_ENABLED_HARDIRQS_READ)
372                         *c3 = '?';
373         }
374
375         if (class->usage_mask & LOCKF_ENABLED_SOFTIRQS_READ)
376                 *c4 = '-';
377         if (class->usage_mask & LOCKF_USED_IN_SOFTIRQ_READ) {
378                 *c4 = '+';
379                 if (class->usage_mask & LOCKF_ENABLED_SOFTIRQS_READ)
380                         *c4 = '?';
381         }
382 }
383
384 static void print_lock_name(struct lock_class *class)
385 {
386         char str[KSYM_NAME_LEN + 1], c1, c2, c3, c4;
387         const char *name;
388
389         get_usage_chars(class, &c1, &c2, &c3, &c4);
390
391         name = class->name;
392         if (!name) {
393                 name = __get_key_name(class->key, str);
394                 printk(" (%s", name);
395         } else {
396                 printk(" (%s", name);
397                 if (class->name_version > 1)
398                         printk("#%d", class->name_version);
399                 if (class->subclass)
400                         printk("/%d", class->subclass);
401         }
402         printk("){%c%c%c%c}", c1, c2, c3, c4);
403 }
404
405 static void print_lockdep_cache(struct lockdep_map *lock)
406 {
407         const char *name;
408         char str[KSYM_NAME_LEN + 1];
409
410         name = lock->name;
411         if (!name)
412                 name = __get_key_name(lock->key->subkeys, str);
413
414         printk("%s", name);
415 }
416
417 static void print_lock(struct held_lock *hlock)
418 {
419         print_lock_name(hlock->class);
420         printk(", at: ");
421         print_ip_sym(hlock->acquire_ip);
422 }
423
424 static void lockdep_print_held_locks(struct task_struct *curr)
425 {
426         int i, depth = curr->lockdep_depth;
427
428         if (!depth) {
429                 printk("no locks held by %s/%d.\n", curr->comm, curr->pid);
430                 return;
431         }
432         printk("%d lock%s held by %s/%d:\n",
433                 depth, depth > 1 ? "s" : "", curr->comm, curr->pid);
434
435         for (i = 0; i < depth; i++) {
436                 printk(" #%d: ", i);
437                 print_lock(curr->held_locks + i);
438         }
439 }
440
441 static void print_lock_class_header(struct lock_class *class, int depth)
442 {
443         int bit;
444
445         printk("%*s->", depth, "");
446         print_lock_name(class);
447         printk(" ops: %lu", class->ops);
448         printk(" {\n");
449
450         for (bit = 0; bit < LOCK_USAGE_STATES; bit++) {
451                 if (class->usage_mask & (1 << bit)) {
452                         int len = depth;
453
454                         len += printk("%*s   %s", depth, "", usage_str[bit]);
455                         len += printk(" at:\n");
456                         print_stack_trace(class->usage_traces + bit, len);
457                 }
458         }
459         printk("%*s }\n", depth, "");
460
461         printk("%*s ... key      at: ",depth,"");
462         print_ip_sym((unsigned long)class->key);
463 }
464
465 /*
466  * printk all lock dependencies starting at <entry>:
467  */
468 static void print_lock_dependencies(struct lock_class *class, int depth)
469 {
470         struct lock_list *entry;
471
472         if (DEBUG_LOCKS_WARN_ON(depth >= 20))
473                 return;
474
475         print_lock_class_header(class, depth);
476
477         list_for_each_entry(entry, &class->locks_after, entry) {
478                 if (DEBUG_LOCKS_WARN_ON(!entry->class))
479                         return;
480
481                 print_lock_dependencies(entry->class, depth + 1);
482
483                 printk("%*s ... acquired at:\n",depth,"");
484                 print_stack_trace(&entry->trace, 2);
485                 printk("\n");
486         }
487 }
488
489 /*
490  * Add a new dependency to the head of the list:
491  */
492 static int add_lock_to_list(struct lock_class *class, struct lock_class *this,
493                             struct list_head *head, unsigned long ip, int distance)
494 {
495         struct lock_list *entry;
496         /*
497          * Lock not present yet - get a new dependency struct and
498          * add it to the list:
499          */
500         entry = alloc_list_entry();
501         if (!entry)
502                 return 0;
503
504         entry->class = this;
505         entry->distance = distance;
506         if (!save_trace(&entry->trace))
507                 return 0;
508
509         /*
510          * Since we never remove from the dependency list, the list can
511          * be walked lockless by other CPUs, it's only allocation
512          * that must be protected by the spinlock. But this also means
513          * we must make new entries visible only once writes to the
514          * entry become visible - hence the RCU op:
515          */
516         list_add_tail_rcu(&entry->entry, head);
517
518         return 1;
519 }
520
521 /*
522  * Recursive, forwards-direction lock-dependency checking, used for
523  * both noncyclic checking and for hardirq-unsafe/softirq-unsafe
524  * checking.
525  *
526  * (to keep the stackframe of the recursive functions small we
527  *  use these global variables, and we also mark various helper
528  *  functions as noinline.)
529  */
530 static struct held_lock *check_source, *check_target;
531
532 /*
533  * Print a dependency chain entry (this is only done when a deadlock
534  * has been detected):
535  */
536 static noinline int
537 print_circular_bug_entry(struct lock_list *target, unsigned int depth)
538 {
539         if (debug_locks_silent)
540                 return 0;
541         printk("\n-> #%u", depth);
542         print_lock_name(target->class);
543         printk(":\n");
544         print_stack_trace(&target->trace, 6);
545
546         return 0;
547 }
548
549 static void print_kernel_version(void)
550 {
551         printk("%s %.*s\n", init_utsname()->release,
552                 (int)strcspn(init_utsname()->version, " "),
553                 init_utsname()->version);
554 }
555
556 /*
557  * When a circular dependency is detected, print the
558  * header first:
559  */
560 static noinline int
561 print_circular_bug_header(struct lock_list *entry, unsigned int depth)
562 {
563         struct task_struct *curr = current;
564
565         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
566                 return 0;
567
568         printk("\n=======================================================\n");
569         printk(  "[ INFO: possible circular locking dependency detected ]\n");
570         print_kernel_version();
571         printk(  "-------------------------------------------------------\n");
572         printk("%s/%d is trying to acquire lock:\n",
573                 curr->comm, curr->pid);
574         print_lock(check_source);
575         printk("\nbut task is already holding lock:\n");
576         print_lock(check_target);
577         printk("\nwhich lock already depends on the new lock.\n\n");
578         printk("\nthe existing dependency chain (in reverse order) is:\n");
579
580         print_circular_bug_entry(entry, depth);
581
582         return 0;
583 }
584
585 static noinline int print_circular_bug_tail(void)
586 {
587         struct task_struct *curr = current;
588         struct lock_list this;
589
590         if (debug_locks_silent)
591                 return 0;
592
593         this.class = check_source->class;
594         if (!save_trace(&this.trace))
595                 return 0;
596
597         print_circular_bug_entry(&this, 0);
598
599         printk("\nother info that might help us debug this:\n\n");
600         lockdep_print_held_locks(curr);
601
602         printk("\nstack backtrace:\n");
603         dump_stack();
604
605         return 0;
606 }
607
608 #define RECURSION_LIMIT 40
609
610 static int noinline print_infinite_recursion_bug(void)
611 {
612         if (!debug_locks_off_graph_unlock())
613                 return 0;
614
615         WARN_ON(1);
616
617         return 0;
618 }
619
620 /*
621  * Prove that the dependency graph starting at <entry> can not
622  * lead to <target>. Print an error and return 0 if it does.
623  */
624 static noinline int
625 check_noncircular(struct lock_class *source, unsigned int depth)
626 {
627         struct lock_list *entry;
628
629         debug_atomic_inc(&nr_cyclic_check_recursions);
630         if (depth > max_recursion_depth)
631                 max_recursion_depth = depth;
632         if (depth >= RECURSION_LIMIT)
633                 return print_infinite_recursion_bug();
634         /*
635          * Check this lock's dependency list:
636          */
637         list_for_each_entry(entry, &source->locks_after, entry) {
638                 if (entry->class == check_target->class)
639                         return print_circular_bug_header(entry, depth+1);
640                 debug_atomic_inc(&nr_cyclic_checks);
641                 if (!check_noncircular(entry->class, depth+1))
642                         return print_circular_bug_entry(entry, depth+1);
643         }
644         return 1;
645 }
646
647 static int very_verbose(struct lock_class *class)
648 {
649 #if VERY_VERBOSE
650         return class_filter(class);
651 #endif
652         return 0;
653 }
654 #ifdef CONFIG_TRACE_IRQFLAGS
655
656 /*
657  * Forwards and backwards subgraph searching, for the purposes of
658  * proving that two subgraphs can be connected by a new dependency
659  * without creating any illegal irq-safe -> irq-unsafe lock dependency.
660  */
661 static enum lock_usage_bit find_usage_bit;
662 static struct lock_class *forwards_match, *backwards_match;
663
664 /*
665  * Find a node in the forwards-direction dependency sub-graph starting
666  * at <source> that matches <find_usage_bit>.
667  *
668  * Return 2 if such a node exists in the subgraph, and put that node
669  * into <forwards_match>.
670  *
671  * Return 1 otherwise and keep <forwards_match> unchanged.
672  * Return 0 on error.
673  */
674 static noinline int
675 find_usage_forwards(struct lock_class *source, unsigned int depth)
676 {
677         struct lock_list *entry;
678         int ret;
679
680         if (depth > max_recursion_depth)
681                 max_recursion_depth = depth;
682         if (depth >= RECURSION_LIMIT)
683                 return print_infinite_recursion_bug();
684
685         debug_atomic_inc(&nr_find_usage_forwards_checks);
686         if (source->usage_mask & (1 << find_usage_bit)) {
687                 forwards_match = source;
688                 return 2;
689         }
690
691         /*
692          * Check this lock's dependency list:
693          */
694         list_for_each_entry(entry, &source->locks_after, entry) {
695                 debug_atomic_inc(&nr_find_usage_forwards_recursions);
696                 ret = find_usage_forwards(entry->class, depth+1);
697                 if (ret == 2 || ret == 0)
698                         return ret;
699         }
700         return 1;
701 }
702
703 /*
704  * Find a node in the backwards-direction dependency sub-graph starting
705  * at <source> that matches <find_usage_bit>.
706  *
707  * Return 2 if such a node exists in the subgraph, and put that node
708  * into <backwards_match>.
709  *
710  * Return 1 otherwise and keep <backwards_match> unchanged.
711  * Return 0 on error.
712  */
713 static noinline int
714 find_usage_backwards(struct lock_class *source, unsigned int depth)
715 {
716         struct lock_list *entry;
717         int ret;
718
719         if (!__raw_spin_is_locked(&lockdep_lock))
720                 return DEBUG_LOCKS_WARN_ON(1);
721
722         if (depth > max_recursion_depth)
723                 max_recursion_depth = depth;
724         if (depth >= RECURSION_LIMIT)
725                 return print_infinite_recursion_bug();
726
727         debug_atomic_inc(&nr_find_usage_backwards_checks);
728         if (source->usage_mask & (1 << find_usage_bit)) {
729                 backwards_match = source;
730                 return 2;
731         }
732
733         /*
734          * Check this lock's dependency list:
735          */
736         list_for_each_entry(entry, &source->locks_before, entry) {
737                 debug_atomic_inc(&nr_find_usage_backwards_recursions);
738                 ret = find_usage_backwards(entry->class, depth+1);
739                 if (ret == 2 || ret == 0)
740                         return ret;
741         }
742         return 1;
743 }
744
745 static int
746 print_bad_irq_dependency(struct task_struct *curr,
747                          struct held_lock *prev,
748                          struct held_lock *next,
749                          enum lock_usage_bit bit1,
750                          enum lock_usage_bit bit2,
751                          const char *irqclass)
752 {
753         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
754                 return 0;
755
756         printk("\n======================================================\n");
757         printk(  "[ INFO: %s-safe -> %s-unsafe lock order detected ]\n",
758                 irqclass, irqclass);
759         print_kernel_version();
760         printk(  "------------------------------------------------------\n");
761         printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
762                 curr->comm, curr->pid,
763                 curr->hardirq_context, hardirq_count() >> HARDIRQ_SHIFT,
764                 curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT,
765                 curr->hardirqs_enabled,
766                 curr->softirqs_enabled);
767         print_lock(next);
768
769         printk("\nand this task is already holding:\n");
770         print_lock(prev);
771         printk("which would create a new lock dependency:\n");
772         print_lock_name(prev->class);
773         printk(" ->");
774         print_lock_name(next->class);
775         printk("\n");
776
777         printk("\nbut this new dependency connects a %s-irq-safe lock:\n",
778                 irqclass);
779         print_lock_name(backwards_match);
780         printk("\n... which became %s-irq-safe at:\n", irqclass);
781
782         print_stack_trace(backwards_match->usage_traces + bit1, 1);
783
784         printk("\nto a %s-irq-unsafe lock:\n", irqclass);
785         print_lock_name(forwards_match);
786         printk("\n... which became %s-irq-unsafe at:\n", irqclass);
787         printk("...");
788
789         print_stack_trace(forwards_match->usage_traces + bit2, 1);
790
791         printk("\nother info that might help us debug this:\n\n");
792         lockdep_print_held_locks(curr);
793
794         printk("\nthe %s-irq-safe lock's dependencies:\n", irqclass);
795         print_lock_dependencies(backwards_match, 0);
796
797         printk("\nthe %s-irq-unsafe lock's dependencies:\n", irqclass);
798         print_lock_dependencies(forwards_match, 0);
799
800         printk("\nstack backtrace:\n");
801         dump_stack();
802
803         return 0;
804 }
805
806 static int
807 check_usage(struct task_struct *curr, struct held_lock *prev,
808             struct held_lock *next, enum lock_usage_bit bit_backwards,
809             enum lock_usage_bit bit_forwards, const char *irqclass)
810 {
811         int ret;
812
813         find_usage_bit = bit_backwards;
814         /* fills in <backwards_match> */
815         ret = find_usage_backwards(prev->class, 0);
816         if (!ret || ret == 1)
817                 return ret;
818
819         find_usage_bit = bit_forwards;
820         ret = find_usage_forwards(next->class, 0);
821         if (!ret || ret == 1)
822                 return ret;
823         /* ret == 2 */
824         return print_bad_irq_dependency(curr, prev, next,
825                         bit_backwards, bit_forwards, irqclass);
826 }
827
828 #endif
829
830 static int
831 print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
832                    struct held_lock *next)
833 {
834         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
835                 return 0;
836
837         printk("\n=============================================\n");
838         printk(  "[ INFO: possible recursive locking detected ]\n");
839         print_kernel_version();
840         printk(  "---------------------------------------------\n");
841         printk("%s/%d is trying to acquire lock:\n",
842                 curr->comm, curr->pid);
843         print_lock(next);
844         printk("\nbut task is already holding lock:\n");
845         print_lock(prev);
846
847         printk("\nother info that might help us debug this:\n");
848         lockdep_print_held_locks(curr);
849
850         printk("\nstack backtrace:\n");
851         dump_stack();
852
853         return 0;
854 }
855
856 /*
857  * Check whether we are holding such a class already.
858  *
859  * (Note that this has to be done separately, because the graph cannot
860  * detect such classes of deadlocks.)
861  *
862  * Returns: 0 on deadlock detected, 1 on OK, 2 on recursive read
863  */
864 static int
865 check_deadlock(struct task_struct *curr, struct held_lock *next,
866                struct lockdep_map *next_instance, int read)
867 {
868         struct held_lock *prev;
869         int i;
870
871         for (i = 0; i < curr->lockdep_depth; i++) {
872                 prev = curr->held_locks + i;
873                 if (prev->class != next->class)
874                         continue;
875                 /*
876                  * Allow read-after-read recursion of the same
877                  * lock class (i.e. read_lock(lock)+read_lock(lock)):
878                  */
879                 if ((read == 2) && prev->read)
880                         return 2;
881                 return print_deadlock_bug(curr, prev, next);
882         }
883         return 1;
884 }
885
886 /*
887  * There was a chain-cache miss, and we are about to add a new dependency
888  * to a previous lock. We recursively validate the following rules:
889  *
890  *  - would the adding of the <prev> -> <next> dependency create a
891  *    circular dependency in the graph? [== circular deadlock]
892  *
893  *  - does the new prev->next dependency connect any hardirq-safe lock
894  *    (in the full backwards-subgraph starting at <prev>) with any
895  *    hardirq-unsafe lock (in the full forwards-subgraph starting at
896  *    <next>)? [== illegal lock inversion with hardirq contexts]
897  *
898  *  - does the new prev->next dependency connect any softirq-safe lock
899  *    (in the full backwards-subgraph starting at <prev>) with any
900  *    softirq-unsafe lock (in the full forwards-subgraph starting at
901  *    <next>)? [== illegal lock inversion with softirq contexts]
902  *
903  * any of these scenarios could lead to a deadlock.
904  *
905  * Then if all the validations pass, we add the forwards and backwards
906  * dependency.
907  */
908 static int
909 check_prev_add(struct task_struct *curr, struct held_lock *prev,
910                struct held_lock *next, int distance)
911 {
912         struct lock_list *entry;
913         int ret;
914
915         /*
916          * Prove that the new <prev> -> <next> dependency would not
917          * create a circular dependency in the graph. (We do this by
918          * forward-recursing into the graph starting at <next>, and
919          * checking whether we can reach <prev>.)
920          *
921          * We are using global variables to control the recursion, to
922          * keep the stackframe size of the recursive functions low:
923          */
924         check_source = next;
925         check_target = prev;
926         if (!(check_noncircular(next->class, 0)))
927                 return print_circular_bug_tail();
928
929 #ifdef CONFIG_TRACE_IRQFLAGS
930         /*
931          * Prove that the new dependency does not connect a hardirq-safe
932          * lock with a hardirq-unsafe lock - to achieve this we search
933          * the backwards-subgraph starting at <prev>, and the
934          * forwards-subgraph starting at <next>:
935          */
936         if (!check_usage(curr, prev, next, LOCK_USED_IN_HARDIRQ,
937                                         LOCK_ENABLED_HARDIRQS, "hard"))
938                 return 0;
939
940         /*
941          * Prove that the new dependency does not connect a hardirq-safe-read
942          * lock with a hardirq-unsafe lock - to achieve this we search
943          * the backwards-subgraph starting at <prev>, and the
944          * forwards-subgraph starting at <next>:
945          */
946         if (!check_usage(curr, prev, next, LOCK_USED_IN_HARDIRQ_READ,
947                                         LOCK_ENABLED_HARDIRQS, "hard-read"))
948                 return 0;
949
950         /*
951          * Prove that the new dependency does not connect a softirq-safe
952          * lock with a softirq-unsafe lock - to achieve this we search
953          * the backwards-subgraph starting at <prev>, and the
954          * forwards-subgraph starting at <next>:
955          */
956         if (!check_usage(curr, prev, next, LOCK_USED_IN_SOFTIRQ,
957                                         LOCK_ENABLED_SOFTIRQS, "soft"))
958                 return 0;
959         /*
960          * Prove that the new dependency does not connect a softirq-safe-read
961          * lock with a softirq-unsafe lock - to achieve this we search
962          * the backwards-subgraph starting at <prev>, and the
963          * forwards-subgraph starting at <next>:
964          */
965         if (!check_usage(curr, prev, next, LOCK_USED_IN_SOFTIRQ_READ,
966                                         LOCK_ENABLED_SOFTIRQS, "soft"))
967                 return 0;
968 #endif
969         /*
970          * For recursive read-locks we do all the dependency checks,
971          * but we dont store read-triggered dependencies (only
972          * write-triggered dependencies). This ensures that only the
973          * write-side dependencies matter, and that if for example a
974          * write-lock never takes any other locks, then the reads are
975          * equivalent to a NOP.
976          */
977         if (next->read == 2 || prev->read == 2)
978                 return 1;
979         /*
980          * Is the <prev> -> <next> dependency already present?
981          *
982          * (this may occur even though this is a new chain: consider
983          *  e.g. the L1 -> L2 -> L3 -> L4 and the L5 -> L1 -> L2 -> L3
984          *  chains - the second one will be new, but L1 already has
985          *  L2 added to its dependency list, due to the first chain.)
986          */
987         list_for_each_entry(entry, &prev->class->locks_after, entry) {
988                 if (entry->class == next->class) {
989                         if (distance == 1)
990                                 entry->distance = 1;
991                         return 2;
992                 }
993         }
994
995         /*
996          * Ok, all validations passed, add the new lock
997          * to the previous lock's dependency list:
998          */
999         ret = add_lock_to_list(prev->class, next->class,
1000                                &prev->class->locks_after, next->acquire_ip, distance);
1001
1002         if (!ret)
1003                 return 0;
1004
1005         ret = add_lock_to_list(next->class, prev->class,
1006                                &next->class->locks_before, next->acquire_ip, distance);
1007         if (!ret)
1008                 return 0;
1009
1010         /*
1011          * Debugging printouts:
1012          */
1013         if (verbose(prev->class) || verbose(next->class)) {
1014                 graph_unlock();
1015                 printk("\n new dependency: ");
1016                 print_lock_name(prev->class);
1017                 printk(" => ");
1018                 print_lock_name(next->class);
1019                 printk("\n");
1020                 dump_stack();
1021                 return graph_lock();
1022         }
1023         return 1;
1024 }
1025
1026 /*
1027  * Add the dependency to all directly-previous locks that are 'relevant'.
1028  * The ones that are relevant are (in increasing distance from curr):
1029  * all consecutive trylock entries and the final non-trylock entry - or
1030  * the end of this context's lock-chain - whichever comes first.
1031  */
1032 static int
1033 check_prevs_add(struct task_struct *curr, struct held_lock *next)
1034 {
1035         int depth = curr->lockdep_depth;
1036         struct held_lock *hlock;
1037
1038         /*
1039          * Debugging checks.
1040          *
1041          * Depth must not be zero for a non-head lock:
1042          */
1043         if (!depth)
1044                 goto out_bug;
1045         /*
1046          * At least two relevant locks must exist for this
1047          * to be a head:
1048          */
1049         if (curr->held_locks[depth].irq_context !=
1050                         curr->held_locks[depth-1].irq_context)
1051                 goto out_bug;
1052
1053         for (;;) {
1054                 int distance = curr->lockdep_depth - depth + 1;
1055                 hlock = curr->held_locks + depth-1;
1056                 /*
1057                  * Only non-recursive-read entries get new dependencies
1058                  * added:
1059                  */
1060                 if (hlock->read != 2) {
1061                         if (!check_prev_add(curr, hlock, next, distance))
1062                                 return 0;
1063                         /*
1064                          * Stop after the first non-trylock entry,
1065                          * as non-trylock entries have added their
1066                          * own direct dependencies already, so this
1067                          * lock is connected to them indirectly:
1068                          */
1069                         if (!hlock->trylock)
1070                                 break;
1071                 }
1072                 depth--;
1073                 /*
1074                  * End of lock-stack?
1075                  */
1076                 if (!depth)
1077                         break;
1078                 /*
1079                  * Stop the search if we cross into another context:
1080                  */
1081                 if (curr->held_locks[depth].irq_context !=
1082                                 curr->held_locks[depth-1].irq_context)
1083                         break;
1084         }
1085         return 1;
1086 out_bug:
1087         if (!debug_locks_off_graph_unlock())
1088                 return 0;
1089
1090         WARN_ON(1);
1091
1092         return 0;
1093 }
1094
1095
1096 /*
1097  * Is this the address of a static object:
1098  */
1099 static int static_obj(void *obj)
1100 {
1101         unsigned long start = (unsigned long) &_stext,
1102                       end   = (unsigned long) &_end,
1103                       addr  = (unsigned long) obj;
1104 #ifdef CONFIG_SMP
1105         int i;
1106 #endif
1107
1108         /*
1109          * static variable?
1110          */
1111         if ((addr >= start) && (addr < end))
1112                 return 1;
1113
1114 #ifdef CONFIG_SMP
1115         /*
1116          * percpu var?
1117          */
1118         for_each_possible_cpu(i) {
1119                 start = (unsigned long) &__per_cpu_start + per_cpu_offset(i);
1120                 end   = (unsigned long) &__per_cpu_start + PERCPU_ENOUGH_ROOM
1121                                         + per_cpu_offset(i);
1122
1123                 if ((addr >= start) && (addr < end))
1124                         return 1;
1125         }
1126 #endif
1127
1128         /*
1129          * module var?
1130          */
1131         return is_module_address(addr);
1132 }
1133
1134 /*
1135  * To make lock name printouts unique, we calculate a unique
1136  * class->name_version generation counter:
1137  */
1138 static int count_matching_names(struct lock_class *new_class)
1139 {
1140         struct lock_class *class;
1141         int count = 0;
1142
1143         if (!new_class->name)
1144                 return 0;
1145
1146         list_for_each_entry(class, &all_lock_classes, lock_entry) {
1147                 if (new_class->key - new_class->subclass == class->key)
1148                         return class->name_version;
1149                 if (class->name && !strcmp(class->name, new_class->name))
1150                         count = max(count, class->name_version);
1151         }
1152
1153         return count + 1;
1154 }
1155
1156 /*
1157  * Register a lock's class in the hash-table, if the class is not present
1158  * yet. Otherwise we look it up. We cache the result in the lock object
1159  * itself, so actual lookup of the hash should be once per lock object.
1160  */
1161 static inline struct lock_class *
1162 look_up_lock_class(struct lockdep_map *lock, unsigned int subclass)
1163 {
1164         struct lockdep_subclass_key *key;
1165         struct list_head *hash_head;
1166         struct lock_class *class;
1167
1168 #ifdef CONFIG_DEBUG_LOCKDEP
1169         /*
1170          * If the architecture calls into lockdep before initializing
1171          * the hashes then we'll warn about it later. (we cannot printk
1172          * right now)
1173          */
1174         if (unlikely(!lockdep_initialized)) {
1175                 lockdep_init();
1176                 lockdep_init_error = 1;
1177         }
1178 #endif
1179
1180         /*
1181          * Static locks do not have their class-keys yet - for them the key
1182          * is the lock object itself:
1183          */
1184         if (unlikely(!lock->key))
1185                 lock->key = (void *)lock;
1186
1187         /*
1188          * NOTE: the class-key must be unique. For dynamic locks, a static
1189          * lock_class_key variable is passed in through the mutex_init()
1190          * (or spin_lock_init()) call - which acts as the key. For static
1191          * locks we use the lock object itself as the key.
1192          */
1193         BUILD_BUG_ON(sizeof(struct lock_class_key) > sizeof(struct lock_class));
1194
1195         key = lock->key->subkeys + subclass;
1196
1197         hash_head = classhashentry(key);
1198
1199         /*
1200          * We can walk the hash lockfree, because the hash only
1201          * grows, and we are careful when adding entries to the end:
1202          */
1203         list_for_each_entry(class, hash_head, hash_entry)
1204                 if (class->key == key)
1205                         return class;
1206
1207         return NULL;
1208 }
1209
1210 /*
1211  * Register a lock's class in the hash-table, if the class is not present
1212  * yet. Otherwise we look it up. We cache the result in the lock object
1213  * itself, so actual lookup of the hash should be once per lock object.
1214  */
1215 static inline struct lock_class *
1216 register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
1217 {
1218         struct lockdep_subclass_key *key;
1219         struct list_head *hash_head;
1220         struct lock_class *class;
1221         unsigned long flags;
1222
1223         class = look_up_lock_class(lock, subclass);
1224         if (likely(class))
1225                 return class;
1226
1227         /*
1228          * Debug-check: all keys must be persistent!
1229          */
1230         if (!static_obj(lock->key)) {
1231                 debug_locks_off();
1232                 printk("INFO: trying to register non-static key.\n");
1233                 printk("the code is fine but needs lockdep annotation.\n");
1234                 printk("turning off the locking correctness validator.\n");
1235                 dump_stack();
1236
1237                 return NULL;
1238         }
1239
1240         key = lock->key->subkeys + subclass;
1241         hash_head = classhashentry(key);
1242
1243         raw_local_irq_save(flags);
1244         if (!graph_lock()) {
1245                 raw_local_irq_restore(flags);
1246                 return NULL;
1247         }
1248         /*
1249          * We have to do the hash-walk again, to avoid races
1250          * with another CPU:
1251          */
1252         list_for_each_entry(class, hash_head, hash_entry)
1253                 if (class->key == key)
1254                         goto out_unlock_set;
1255         /*
1256          * Allocate a new key from the static array, and add it to
1257          * the hash:
1258          */
1259         if (nr_lock_classes >= MAX_LOCKDEP_KEYS) {
1260                 if (!debug_locks_off_graph_unlock()) {
1261                         raw_local_irq_restore(flags);
1262                         return NULL;
1263                 }
1264                 raw_local_irq_restore(flags);
1265
1266                 printk("BUG: MAX_LOCKDEP_KEYS too low!\n");
1267                 printk("turning off the locking correctness validator.\n");
1268                 return NULL;
1269         }
1270         class = lock_classes + nr_lock_classes++;
1271         debug_atomic_inc(&nr_unused_locks);
1272         class->key = key;
1273         class->name = lock->name;
1274         class->subclass = subclass;
1275         INIT_LIST_HEAD(&class->lock_entry);
1276         INIT_LIST_HEAD(&class->locks_before);
1277         INIT_LIST_HEAD(&class->locks_after);
1278         class->name_version = count_matching_names(class);
1279         /*
1280          * We use RCU's safe list-add method to make
1281          * parallel walking of the hash-list safe:
1282          */
1283         list_add_tail_rcu(&class->hash_entry, hash_head);
1284
1285         if (verbose(class)) {
1286                 graph_unlock();
1287                 raw_local_irq_restore(flags);
1288
1289                 printk("\nnew class %p: %s", class->key, class->name);
1290                 if (class->name_version > 1)
1291                         printk("#%d", class->name_version);
1292                 printk("\n");
1293                 dump_stack();
1294
1295                 raw_local_irq_save(flags);
1296                 if (!graph_lock()) {
1297                         raw_local_irq_restore(flags);
1298                         return NULL;
1299                 }
1300         }
1301 out_unlock_set:
1302         graph_unlock();
1303         raw_local_irq_restore(flags);
1304
1305         if (!subclass || force)
1306                 lock->class_cache = class;
1307
1308         if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))
1309                 return NULL;
1310
1311         return class;
1312 }
1313
1314 /*
1315  * Look up a dependency chain. If the key is not present yet then
1316  * add it and return 0 - in this case the new dependency chain is
1317  * validated. If the key is already hashed, return 1.
1318  */
1319 static inline int lookup_chain_cache(u64 chain_key, struct lock_class *class)
1320 {
1321         struct list_head *hash_head = chainhashentry(chain_key);
1322         struct lock_chain *chain;
1323
1324         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
1325                 return 0;
1326         /*
1327          * We can walk it lock-free, because entries only get added
1328          * to the hash:
1329          */
1330         list_for_each_entry(chain, hash_head, entry) {
1331                 if (chain->chain_key == chain_key) {
1332 cache_hit:
1333                         debug_atomic_inc(&chain_lookup_hits);
1334                         if (very_verbose(class))
1335                                 printk("\nhash chain already cached, key: "
1336                                         "%016Lx tail class: [%p] %s\n",
1337                                         (unsigned long long)chain_key,
1338                                         class->key, class->name);
1339                         return 0;
1340                 }
1341         }
1342         if (very_verbose(class))
1343                 printk("\nnew hash chain, key: %016Lx tail class: [%p] %s\n",
1344                         (unsigned long long)chain_key, class->key, class->name);
1345         /*
1346          * Allocate a new chain entry from the static array, and add
1347          * it to the hash:
1348          */
1349         if (!graph_lock())
1350                 return 0;
1351         /*
1352          * We have to walk the chain again locked - to avoid duplicates:
1353          */
1354         list_for_each_entry(chain, hash_head, entry) {
1355                 if (chain->chain_key == chain_key) {
1356                         graph_unlock();
1357                         goto cache_hit;
1358                 }
1359         }
1360         if (unlikely(nr_lock_chains >= MAX_LOCKDEP_CHAINS)) {
1361                 if (!debug_locks_off_graph_unlock())
1362                         return 0;
1363
1364                 printk("BUG: MAX_LOCKDEP_CHAINS too low!\n");
1365                 printk("turning off the locking correctness validator.\n");
1366                 return 0;
1367         }
1368         chain = lock_chains + nr_lock_chains++;
1369         chain->chain_key = chain_key;
1370         list_add_tail_rcu(&chain->entry, hash_head);
1371         debug_atomic_inc(&chain_lookup_misses);
1372 #ifdef CONFIG_TRACE_IRQFLAGS
1373         if (current->hardirq_context)
1374                 nr_hardirq_chains++;
1375         else {
1376                 if (current->softirq_context)
1377                         nr_softirq_chains++;
1378                 else
1379                         nr_process_chains++;
1380         }
1381 #else
1382         nr_process_chains++;
1383 #endif
1384
1385         return 1;
1386 }
1387
1388 /*
1389  * We are building curr_chain_key incrementally, so double-check
1390  * it from scratch, to make sure that it's done correctly:
1391  */
1392 static void check_chain_key(struct task_struct *curr)
1393 {
1394 #ifdef CONFIG_DEBUG_LOCKDEP
1395         struct held_lock *hlock, *prev_hlock = NULL;
1396         unsigned int i, id;
1397         u64 chain_key = 0;
1398
1399         for (i = 0; i < curr->lockdep_depth; i++) {
1400                 hlock = curr->held_locks + i;
1401                 if (chain_key != hlock->prev_chain_key) {
1402                         debug_locks_off();
1403                         printk("hm#1, depth: %u [%u], %016Lx != %016Lx\n",
1404                                 curr->lockdep_depth, i,
1405                                 (unsigned long long)chain_key,
1406                                 (unsigned long long)hlock->prev_chain_key);
1407                         WARN_ON(1);
1408                         return;
1409                 }
1410                 id = hlock->class - lock_classes;
1411                 if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
1412                         return;
1413
1414                 if (prev_hlock && (prev_hlock->irq_context !=
1415                                                         hlock->irq_context))
1416                         chain_key = 0;
1417                 chain_key = iterate_chain_key(chain_key, id);
1418                 prev_hlock = hlock;
1419         }
1420         if (chain_key != curr->curr_chain_key) {
1421                 debug_locks_off();
1422                 printk("hm#2, depth: %u [%u], %016Lx != %016Lx\n",
1423                         curr->lockdep_depth, i,
1424                         (unsigned long long)chain_key,
1425                         (unsigned long long)curr->curr_chain_key);
1426                 WARN_ON(1);
1427         }
1428 #endif
1429 }
1430
1431 #ifdef CONFIG_TRACE_IRQFLAGS
1432
1433 /*
1434  * print irq inversion bug:
1435  */
1436 static int
1437 print_irq_inversion_bug(struct task_struct *curr, struct lock_class *other,
1438                         struct held_lock *this, int forwards,
1439                         const char *irqclass)
1440 {
1441         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1442                 return 0;
1443
1444         printk("\n=========================================================\n");
1445         printk(  "[ INFO: possible irq lock inversion dependency detected ]\n");
1446         print_kernel_version();
1447         printk(  "---------------------------------------------------------\n");
1448         printk("%s/%d just changed the state of lock:\n",
1449                 curr->comm, curr->pid);
1450         print_lock(this);
1451         if (forwards)
1452                 printk("but this lock took another, %s-irq-unsafe lock in the past:\n", irqclass);
1453         else
1454                 printk("but this lock was taken by another, %s-irq-safe lock in the past:\n", irqclass);
1455         print_lock_name(other);
1456         printk("\n\nand interrupts could create inverse lock ordering between them.\n\n");
1457
1458         printk("\nother info that might help us debug this:\n");
1459         lockdep_print_held_locks(curr);
1460
1461         printk("\nthe first lock's dependencies:\n");
1462         print_lock_dependencies(this->class, 0);
1463
1464         printk("\nthe second lock's dependencies:\n");
1465         print_lock_dependencies(other, 0);
1466
1467         printk("\nstack backtrace:\n");
1468         dump_stack();
1469
1470         return 0;
1471 }
1472
1473 /*
1474  * Prove that in the forwards-direction subgraph starting at <this>
1475  * there is no lock matching <mask>:
1476  */
1477 static int
1478 check_usage_forwards(struct task_struct *curr, struct held_lock *this,
1479                      enum lock_usage_bit bit, const char *irqclass)
1480 {
1481         int ret;
1482
1483         find_usage_bit = bit;
1484         /* fills in <forwards_match> */
1485         ret = find_usage_forwards(this->class, 0);
1486         if (!ret || ret == 1)
1487                 return ret;
1488
1489         return print_irq_inversion_bug(curr, forwards_match, this, 1, irqclass);
1490 }
1491
1492 /*
1493  * Prove that in the backwards-direction subgraph starting at <this>
1494  * there is no lock matching <mask>:
1495  */
1496 static int
1497 check_usage_backwards(struct task_struct *curr, struct held_lock *this,
1498                       enum lock_usage_bit bit, const char *irqclass)
1499 {
1500         int ret;
1501
1502         find_usage_bit = bit;
1503         /* fills in <backwards_match> */
1504         ret = find_usage_backwards(this->class, 0);
1505         if (!ret || ret == 1)
1506                 return ret;
1507
1508         return print_irq_inversion_bug(curr, backwards_match, this, 0, irqclass);
1509 }
1510
1511 void print_irqtrace_events(struct task_struct *curr)
1512 {
1513         printk("irq event stamp: %u\n", curr->irq_events);
1514         printk("hardirqs last  enabled at (%u): ", curr->hardirq_enable_event);
1515         print_ip_sym(curr->hardirq_enable_ip);
1516         printk("hardirqs last disabled at (%u): ", curr->hardirq_disable_event);
1517         print_ip_sym(curr->hardirq_disable_ip);
1518         printk("softirqs last  enabled at (%u): ", curr->softirq_enable_event);
1519         print_ip_sym(curr->softirq_enable_ip);
1520         printk("softirqs last disabled at (%u): ", curr->softirq_disable_event);
1521         print_ip_sym(curr->softirq_disable_ip);
1522 }
1523
1524 #endif
1525
1526 static int
1527 print_usage_bug(struct task_struct *curr, struct held_lock *this,
1528                 enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
1529 {
1530         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1531                 return 0;
1532
1533         printk("\n=================================\n");
1534         printk(  "[ INFO: inconsistent lock state ]\n");
1535         print_kernel_version();
1536         printk(  "---------------------------------\n");
1537
1538         printk("inconsistent {%s} -> {%s} usage.\n",
1539                 usage_str[prev_bit], usage_str[new_bit]);
1540
1541         printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] takes:\n",
1542                 curr->comm, curr->pid,
1543                 trace_hardirq_context(curr), hardirq_count() >> HARDIRQ_SHIFT,
1544                 trace_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT,
1545                 trace_hardirqs_enabled(curr),
1546                 trace_softirqs_enabled(curr));
1547         print_lock(this);
1548
1549         printk("{%s} state was registered at:\n", usage_str[prev_bit]);
1550         print_stack_trace(this->class->usage_traces + prev_bit, 1);
1551
1552         print_irqtrace_events(curr);
1553         printk("\nother info that might help us debug this:\n");
1554         lockdep_print_held_locks(curr);
1555
1556         printk("\nstack backtrace:\n");
1557         dump_stack();
1558
1559         return 0;
1560 }
1561
1562 /*
1563  * Print out an error if an invalid bit is set:
1564  */
1565 static inline int
1566 valid_state(struct task_struct *curr, struct held_lock *this,
1567             enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit)
1568 {
1569         if (unlikely(this->class->usage_mask & (1 << bad_bit)))
1570                 return print_usage_bug(curr, this, bad_bit, new_bit);
1571         return 1;
1572 }
1573
1574 #define STRICT_READ_CHECKS      1
1575
1576 /*
1577  * Mark a lock with a usage bit, and validate the state transition:
1578  */
1579 static int mark_lock(struct task_struct *curr, struct held_lock *this,
1580                      enum lock_usage_bit new_bit, unsigned long ip)
1581 {
1582         unsigned int new_mask = 1 << new_bit, ret = 1;
1583
1584         /*
1585          * If already set then do not dirty the cacheline,
1586          * nor do any checks:
1587          */
1588         if (likely(this->class->usage_mask & new_mask))
1589                 return 1;
1590
1591         if (!graph_lock())
1592                 return 0;
1593         /*
1594          * Make sure we didnt race:
1595          */
1596         if (unlikely(this->class->usage_mask & new_mask)) {
1597                 graph_unlock();
1598                 return 1;
1599         }
1600
1601         this->class->usage_mask |= new_mask;
1602
1603 #ifdef CONFIG_TRACE_IRQFLAGS
1604         if (new_bit == LOCK_ENABLED_HARDIRQS ||
1605                         new_bit == LOCK_ENABLED_HARDIRQS_READ)
1606                 ip = curr->hardirq_enable_ip;
1607         else if (new_bit == LOCK_ENABLED_SOFTIRQS ||
1608                         new_bit == LOCK_ENABLED_SOFTIRQS_READ)
1609                 ip = curr->softirq_enable_ip;
1610 #endif
1611         if (!save_trace(this->class->usage_traces + new_bit))
1612                 return 0;
1613
1614         switch (new_bit) {
1615 #ifdef CONFIG_TRACE_IRQFLAGS
1616         case LOCK_USED_IN_HARDIRQ:
1617                 if (!valid_state(curr, this, new_bit, LOCK_ENABLED_HARDIRQS))
1618                         return 0;
1619                 if (!valid_state(curr, this, new_bit,
1620                                  LOCK_ENABLED_HARDIRQS_READ))
1621                         return 0;
1622                 /*
1623                  * just marked it hardirq-safe, check that this lock
1624                  * took no hardirq-unsafe lock in the past:
1625                  */
1626                 if (!check_usage_forwards(curr, this,
1627                                           LOCK_ENABLED_HARDIRQS, "hard"))
1628                         return 0;
1629 #if STRICT_READ_CHECKS
1630                 /*
1631                  * just marked it hardirq-safe, check that this lock
1632                  * took no hardirq-unsafe-read lock in the past:
1633                  */
1634                 if (!check_usage_forwards(curr, this,
1635                                 LOCK_ENABLED_HARDIRQS_READ, "hard-read"))
1636                         return 0;
1637 #endif
1638                 if (hardirq_verbose(this->class))
1639                         ret = 2;
1640                 break;
1641         case LOCK_USED_IN_SOFTIRQ:
1642                 if (!valid_state(curr, this, new_bit, LOCK_ENABLED_SOFTIRQS))
1643                         return 0;
1644                 if (!valid_state(curr, this, new_bit,
1645                                  LOCK_ENABLED_SOFTIRQS_READ))
1646                         return 0;
1647                 /*
1648                  * just marked it softirq-safe, check that this lock
1649                  * took no softirq-unsafe lock in the past:
1650                  */
1651                 if (!check_usage_forwards(curr, this,
1652                                           LOCK_ENABLED_SOFTIRQS, "soft"))
1653                         return 0;
1654 #if STRICT_READ_CHECKS
1655                 /*
1656                  * just marked it softirq-safe, check that this lock
1657                  * took no softirq-unsafe-read lock in the past:
1658                  */
1659                 if (!check_usage_forwards(curr, this,
1660                                 LOCK_ENABLED_SOFTIRQS_READ, "soft-read"))
1661                         return 0;
1662 #endif
1663                 if (softirq_verbose(this->class))
1664                         ret = 2;
1665                 break;
1666         case LOCK_USED_IN_HARDIRQ_READ:
1667                 if (!valid_state(curr, this, new_bit, LOCK_ENABLED_HARDIRQS))
1668                         return 0;
1669                 /*
1670                  * just marked it hardirq-read-safe, check that this lock
1671                  * took no hardirq-unsafe lock in the past:
1672                  */
1673                 if (!check_usage_forwards(curr, this,
1674                                           LOCK_ENABLED_HARDIRQS, "hard"))
1675                         return 0;
1676                 if (hardirq_verbose(this->class))
1677                         ret = 2;
1678                 break;
1679         case LOCK_USED_IN_SOFTIRQ_READ:
1680                 if (!valid_state(curr, this, new_bit, LOCK_ENABLED_SOFTIRQS))
1681                         return 0;
1682                 /*
1683                  * just marked it softirq-read-safe, check that this lock
1684                  * took no softirq-unsafe lock in the past:
1685                  */
1686                 if (!check_usage_forwards(curr, this,
1687                                           LOCK_ENABLED_SOFTIRQS, "soft"))
1688                         return 0;
1689                 if (softirq_verbose(this->class))
1690                         ret = 2;
1691                 break;
1692         case LOCK_ENABLED_HARDIRQS:
1693                 if (!valid_state(curr, this, new_bit, LOCK_USED_IN_HARDIRQ))
1694                         return 0;
1695                 if (!valid_state(curr, this, new_bit,
1696                                  LOCK_USED_IN_HARDIRQ_READ))
1697                         return 0;
1698                 /*
1699                  * just marked it hardirq-unsafe, check that no hardirq-safe
1700                  * lock in the system ever took it in the past:
1701                  */
1702                 if (!check_usage_backwards(curr, this,
1703                                            LOCK_USED_IN_HARDIRQ, "hard"))
1704                         return 0;
1705 #if STRICT_READ_CHECKS
1706                 /*
1707                  * just marked it hardirq-unsafe, check that no
1708                  * hardirq-safe-read lock in the system ever took
1709                  * it in the past:
1710                  */
1711                 if (!check_usage_backwards(curr, this,
1712                                    LOCK_USED_IN_HARDIRQ_READ, "hard-read"))
1713                         return 0;
1714 #endif
1715                 if (hardirq_verbose(this->class))
1716                         ret = 2;
1717                 break;
1718         case LOCK_ENABLED_SOFTIRQS:
1719                 if (!valid_state(curr, this, new_bit, LOCK_USED_IN_SOFTIRQ))
1720                         return 0;
1721                 if (!valid_state(curr, this, new_bit,
1722                                  LOCK_USED_IN_SOFTIRQ_READ))
1723                         return 0;
1724                 /*
1725                  * just marked it softirq-unsafe, check that no softirq-safe
1726                  * lock in the system ever took it in the past:
1727                  */
1728                 if (!check_usage_backwards(curr, this,
1729                                            LOCK_USED_IN_SOFTIRQ, "soft"))
1730                         return 0;
1731 #if STRICT_READ_CHECKS
1732                 /*
1733                  * just marked it softirq-unsafe, check that no
1734                  * softirq-safe-read lock in the system ever took
1735                  * it in the past:
1736                  */
1737                 if (!check_usage_backwards(curr, this,
1738                                    LOCK_USED_IN_SOFTIRQ_READ, "soft-read"))
1739                         return 0;
1740 #endif
1741                 if (softirq_verbose(this->class))
1742                         ret = 2;
1743                 break;
1744         case LOCK_ENABLED_HARDIRQS_READ:
1745                 if (!valid_state(curr, this, new_bit, LOCK_USED_IN_HARDIRQ))
1746                         return 0;
1747 #if STRICT_READ_CHECKS
1748                 /*
1749                  * just marked it hardirq-read-unsafe, check that no
1750                  * hardirq-safe lock in the system ever took it in the past:
1751                  */
1752                 if (!check_usage_backwards(curr, this,
1753                                            LOCK_USED_IN_HARDIRQ, "hard"))
1754                         return 0;
1755 #endif
1756                 if (hardirq_verbose(this->class))
1757                         ret = 2;
1758                 break;
1759         case LOCK_ENABLED_SOFTIRQS_READ:
1760                 if (!valid_state(curr, this, new_bit, LOCK_USED_IN_SOFTIRQ))
1761                         return 0;
1762 #if STRICT_READ_CHECKS
1763                 /*
1764                  * just marked it softirq-read-unsafe, check that no
1765                  * softirq-safe lock in the system ever took it in the past:
1766                  */
1767                 if (!check_usage_backwards(curr, this,
1768                                            LOCK_USED_IN_SOFTIRQ, "soft"))
1769                         return 0;
1770 #endif
1771                 if (softirq_verbose(this->class))
1772                         ret = 2;
1773                 break;
1774 #endif
1775         case LOCK_USED:
1776                 /*
1777                  * Add it to the global list of classes:
1778                  */
1779                 list_add_tail_rcu(&this->class->lock_entry, &all_lock_classes);
1780                 debug_atomic_dec(&nr_unused_locks);
1781                 break;
1782         default:
1783                 if (!debug_locks_off_graph_unlock())
1784                         return 0;
1785                 WARN_ON(1);
1786                 return 0;
1787         }
1788
1789         graph_unlock();
1790
1791         /*
1792          * We must printk outside of the graph_lock:
1793          */
1794         if (ret == 2) {
1795                 printk("\nmarked lock as {%s}:\n", usage_str[new_bit]);
1796                 print_lock(this);
1797                 print_irqtrace_events(curr);
1798                 dump_stack();
1799         }
1800
1801         return ret;
1802 }
1803
1804 #ifdef CONFIG_TRACE_IRQFLAGS
1805 /*
1806  * Mark all held locks with a usage bit:
1807  */
1808 static int
1809 mark_held_locks(struct task_struct *curr, int hardirq, unsigned long ip)
1810 {
1811         enum lock_usage_bit usage_bit;
1812         struct held_lock *hlock;
1813         int i;
1814
1815         for (i = 0; i < curr->lockdep_depth; i++) {
1816                 hlock = curr->held_locks + i;
1817
1818                 if (hardirq) {
1819                         if (hlock->read)
1820                                 usage_bit = LOCK_ENABLED_HARDIRQS_READ;
1821                         else
1822                                 usage_bit = LOCK_ENABLED_HARDIRQS;
1823                 } else {
1824                         if (hlock->read)
1825                                 usage_bit = LOCK_ENABLED_SOFTIRQS_READ;
1826                         else
1827                                 usage_bit = LOCK_ENABLED_SOFTIRQS;
1828                 }
1829                 if (!mark_lock(curr, hlock, usage_bit, ip))
1830                         return 0;
1831         }
1832
1833         return 1;
1834 }
1835
1836 /*
1837  * Debugging helper: via this flag we know that we are in
1838  * 'early bootup code', and will warn about any invalid irqs-on event:
1839  */
1840 static int early_boot_irqs_enabled;
1841
1842 void early_boot_irqs_off(void)
1843 {
1844         early_boot_irqs_enabled = 0;
1845 }
1846
1847 void early_boot_irqs_on(void)
1848 {
1849         early_boot_irqs_enabled = 1;
1850 }
1851
1852 /*
1853  * Hardirqs will be enabled:
1854  */
1855 void trace_hardirqs_on(void)
1856 {
1857         struct task_struct *curr = current;
1858         unsigned long ip;
1859
1860         if (unlikely(!debug_locks || current->lockdep_recursion))
1861                 return;
1862
1863         if (DEBUG_LOCKS_WARN_ON(unlikely(!early_boot_irqs_enabled)))
1864                 return;
1865
1866         if (unlikely(curr->hardirqs_enabled)) {
1867                 debug_atomic_inc(&redundant_hardirqs_on);
1868                 return;
1869         }
1870         /* we'll do an OFF -> ON transition: */
1871         curr->hardirqs_enabled = 1;
1872         ip = (unsigned long) __builtin_return_address(0);
1873
1874         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
1875                 return;
1876         if (DEBUG_LOCKS_WARN_ON(current->hardirq_context))
1877                 return;
1878         /*
1879          * We are going to turn hardirqs on, so set the
1880          * usage bit for all held locks:
1881          */
1882         if (!mark_held_locks(curr, 1, ip))
1883                 return;
1884         /*
1885          * If we have softirqs enabled, then set the usage
1886          * bit for all held locks. (disabled hardirqs prevented
1887          * this bit from being set before)
1888          */
1889         if (curr->softirqs_enabled)
1890                 if (!mark_held_locks(curr, 0, ip))
1891                         return;
1892
1893         curr->hardirq_enable_ip = ip;
1894         curr->hardirq_enable_event = ++curr->irq_events;
1895         debug_atomic_inc(&hardirqs_on_events);
1896 }
1897
1898 EXPORT_SYMBOL(trace_hardirqs_on);
1899
1900 /*
1901  * Hardirqs were disabled:
1902  */
1903 void trace_hardirqs_off(void)
1904 {
1905         struct task_struct *curr = current;
1906
1907         if (unlikely(!debug_locks || current->lockdep_recursion))
1908                 return;
1909
1910         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
1911                 return;
1912
1913         if (curr->hardirqs_enabled) {
1914                 /*
1915                  * We have done an ON -> OFF transition:
1916                  */
1917                 curr->hardirqs_enabled = 0;
1918                 curr->hardirq_disable_ip = _RET_IP_;
1919                 curr->hardirq_disable_event = ++curr->irq_events;
1920                 debug_atomic_inc(&hardirqs_off_events);
1921         } else
1922                 debug_atomic_inc(&redundant_hardirqs_off);
1923 }
1924
1925 EXPORT_SYMBOL(trace_hardirqs_off);
1926
1927 /*
1928  * Softirqs will be enabled:
1929  */
1930 void trace_softirqs_on(unsigned long ip)
1931 {
1932         struct task_struct *curr = current;
1933
1934         if (unlikely(!debug_locks))
1935                 return;
1936
1937         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
1938                 return;
1939
1940         if (curr->softirqs_enabled) {
1941                 debug_atomic_inc(&redundant_softirqs_on);
1942                 return;
1943         }
1944
1945         /*
1946          * We'll do an OFF -> ON transition:
1947          */
1948         curr->softirqs_enabled = 1;
1949         curr->softirq_enable_ip = ip;
1950         curr->softirq_enable_event = ++curr->irq_events;
1951         debug_atomic_inc(&softirqs_on_events);
1952         /*
1953          * We are going to turn softirqs on, so set the
1954          * usage bit for all held locks, if hardirqs are
1955          * enabled too:
1956          */
1957         if (curr->hardirqs_enabled)
1958                 mark_held_locks(curr, 0, ip);
1959 }
1960
1961 /*
1962  * Softirqs were disabled:
1963  */
1964 void trace_softirqs_off(unsigned long ip)
1965 {
1966         struct task_struct *curr = current;
1967
1968         if (unlikely(!debug_locks))
1969                 return;
1970
1971         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
1972                 return;
1973
1974         if (curr->softirqs_enabled) {
1975                 /*
1976                  * We have done an ON -> OFF transition:
1977                  */
1978                 curr->softirqs_enabled = 0;
1979                 curr->softirq_disable_ip = ip;
1980                 curr->softirq_disable_event = ++curr->irq_events;
1981                 debug_atomic_inc(&softirqs_off_events);
1982                 DEBUG_LOCKS_WARN_ON(!softirq_count());
1983         } else
1984                 debug_atomic_inc(&redundant_softirqs_off);
1985 }
1986
1987 #endif
1988
1989 /*
1990  * Initialize a lock instance's lock-class mapping info:
1991  */
1992 void lockdep_init_map(struct lockdep_map *lock, const char *name,
1993                       struct lock_class_key *key, int subclass)
1994 {
1995         if (unlikely(!debug_locks))
1996                 return;
1997
1998         if (DEBUG_LOCKS_WARN_ON(!key))
1999                 return;
2000         if (DEBUG_LOCKS_WARN_ON(!name))
2001                 return;
2002         /*
2003          * Sanity check, the lock-class key must be persistent:
2004          */
2005         if (!static_obj(key)) {
2006                 printk("BUG: key %p not in .data!\n", key);
2007                 DEBUG_LOCKS_WARN_ON(1);
2008                 return;
2009         }
2010         lock->name = name;
2011         lock->key = key;
2012         lock->class_cache = NULL;
2013         if (subclass)
2014                 register_lock_class(lock, subclass, 1);
2015 }
2016
2017 EXPORT_SYMBOL_GPL(lockdep_init_map);
2018
2019 /*
2020  * This gets called for every mutex_lock*()/spin_lock*() operation.
2021  * We maintain the dependency maps and validate the locking attempt:
2022  */
2023 static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
2024                           int trylock, int read, int check, int hardirqs_off,
2025                           unsigned long ip)
2026 {
2027         struct task_struct *curr = current;
2028         struct lock_class *class = NULL;
2029         struct held_lock *hlock;
2030         unsigned int depth, id;
2031         int chain_head = 0;
2032         u64 chain_key;
2033
2034         if (unlikely(!debug_locks))
2035                 return 0;
2036
2037         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2038                 return 0;
2039
2040         if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
2041                 debug_locks_off();
2042                 printk("BUG: MAX_LOCKDEP_SUBCLASSES too low!\n");
2043                 printk("turning off the locking correctness validator.\n");
2044                 return 0;
2045         }
2046
2047         if (!subclass)
2048                 class = lock->class_cache;
2049         /*
2050          * Not cached yet or subclass?
2051          */
2052         if (unlikely(!class)) {
2053                 class = register_lock_class(lock, subclass, 0);
2054                 if (!class)
2055                         return 0;
2056         }
2057         debug_atomic_inc((atomic_t *)&class->ops);
2058         if (very_verbose(class)) {
2059                 printk("\nacquire class [%p] %s", class->key, class->name);
2060                 if (class->name_version > 1)
2061                         printk("#%d", class->name_version);
2062                 printk("\n");
2063                 dump_stack();
2064         }
2065
2066         /*
2067          * Add the lock to the list of currently held locks.
2068          * (we dont increase the depth just yet, up until the
2069          * dependency checks are done)
2070          */
2071         depth = curr->lockdep_depth;
2072         if (DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH))
2073                 return 0;
2074
2075         hlock = curr->held_locks + depth;
2076
2077         hlock->class = class;
2078         hlock->acquire_ip = ip;
2079         hlock->instance = lock;
2080         hlock->trylock = trylock;
2081         hlock->read = read;
2082         hlock->check = check;
2083         hlock->hardirqs_off = hardirqs_off;
2084
2085         if (check != 2)
2086                 goto out_calc_hash;
2087 #ifdef CONFIG_TRACE_IRQFLAGS
2088         /*
2089          * If non-trylock use in a hardirq or softirq context, then
2090          * mark the lock as used in these contexts:
2091          */
2092         if (!trylock) {
2093                 if (read) {
2094                         if (curr->hardirq_context)
2095                                 if (!mark_lock(curr, hlock,
2096                                                 LOCK_USED_IN_HARDIRQ_READ, ip))
2097                                         return 0;
2098                         if (curr->softirq_context)
2099                                 if (!mark_lock(curr, hlock,
2100                                                 LOCK_USED_IN_SOFTIRQ_READ, ip))
2101                                         return 0;
2102                 } else {
2103                         if (curr->hardirq_context)
2104                                 if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ, ip))
2105                                         return 0;
2106                         if (curr->softirq_context)
2107                                 if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ, ip))
2108                                         return 0;
2109                 }
2110         }
2111         if (!hardirqs_off) {
2112                 if (read) {
2113                         if (!mark_lock(curr, hlock,
2114                                         LOCK_ENABLED_HARDIRQS_READ, ip))
2115                                 return 0;
2116                         if (curr->softirqs_enabled)
2117                                 if (!mark_lock(curr, hlock,
2118                                                 LOCK_ENABLED_SOFTIRQS_READ, ip))
2119                                         return 0;
2120                 } else {
2121                         if (!mark_lock(curr, hlock,
2122                                         LOCK_ENABLED_HARDIRQS, ip))
2123                                 return 0;
2124                         if (curr->softirqs_enabled)
2125                                 if (!mark_lock(curr, hlock,
2126                                                 LOCK_ENABLED_SOFTIRQS, ip))
2127                                         return 0;
2128                 }
2129         }
2130 #endif
2131         /* mark it as used: */
2132         if (!mark_lock(curr, hlock, LOCK_USED, ip))
2133                 return 0;
2134 out_calc_hash:
2135         /*
2136          * Calculate the chain hash: it's the combined has of all the
2137          * lock keys along the dependency chain. We save the hash value
2138          * at every step so that we can get the current hash easily
2139          * after unlock. The chain hash is then used to cache dependency
2140          * results.
2141          *
2142          * The 'key ID' is what is the most compact key value to drive
2143          * the hash, not class->key.
2144          */
2145         id = class - lock_classes;
2146         if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
2147                 return 0;
2148
2149         chain_key = curr->curr_chain_key;
2150         if (!depth) {
2151                 if (DEBUG_LOCKS_WARN_ON(chain_key != 0))
2152                         return 0;
2153                 chain_head = 1;
2154         }
2155
2156         hlock->prev_chain_key = chain_key;
2157
2158 #ifdef CONFIG_TRACE_IRQFLAGS
2159         /*
2160          * Keep track of points where we cross into an interrupt context:
2161          */
2162         hlock->irq_context = 2*(curr->hardirq_context ? 1 : 0) +
2163                                 curr->softirq_context;
2164         if (depth) {
2165                 struct held_lock *prev_hlock;
2166
2167                 prev_hlock = curr->held_locks + depth-1;
2168                 /*
2169                  * If we cross into another context, reset the
2170                  * hash key (this also prevents the checking and the
2171                  * adding of the dependency to 'prev'):
2172                  */
2173                 if (prev_hlock->irq_context != hlock->irq_context) {
2174                         chain_key = 0;
2175                         chain_head = 1;
2176                 }
2177         }
2178 #endif
2179         chain_key = iterate_chain_key(chain_key, id);
2180         curr->curr_chain_key = chain_key;
2181
2182         /*
2183          * Trylock needs to maintain the stack of held locks, but it
2184          * does not add new dependencies, because trylock can be done
2185          * in any order.
2186          *
2187          * We look up the chain_key and do the O(N^2) check and update of
2188          * the dependencies only if this is a new dependency chain.
2189          * (If lookup_chain_cache() returns with 1 it acquires
2190          * graph_lock for us)
2191          */
2192         if (!trylock && (check == 2) && lookup_chain_cache(chain_key, class)) {
2193                 /*
2194                  * Check whether last held lock:
2195                  *
2196                  * - is irq-safe, if this lock is irq-unsafe
2197                  * - is softirq-safe, if this lock is hardirq-unsafe
2198                  *
2199                  * And check whether the new lock's dependency graph
2200                  * could lead back to the previous lock.
2201                  *
2202                  * any of these scenarios could lead to a deadlock. If
2203                  * All validations
2204                  */
2205                 int ret = check_deadlock(curr, hlock, lock, read);
2206
2207                 if (!ret)
2208                         return 0;
2209                 /*
2210                  * Mark recursive read, as we jump over it when
2211                  * building dependencies (just like we jump over
2212                  * trylock entries):
2213                  */
2214                 if (ret == 2)
2215                         hlock->read = 2;
2216                 /*
2217                  * Add dependency only if this lock is not the head
2218                  * of the chain, and if it's not a secondary read-lock:
2219                  */
2220                 if (!chain_head && ret != 2)
2221                         if (!check_prevs_add(curr, hlock))
2222                                 return 0;
2223                 graph_unlock();
2224         } else
2225                 /* after lookup_chain_cache(): */
2226                 if (unlikely(!debug_locks))
2227                         return 0;
2228
2229         curr->lockdep_depth++;
2230         check_chain_key(curr);
2231 #ifdef CONFIG_DEBUG_LOCKDEP
2232         if (unlikely(!debug_locks))
2233                 return 0;
2234 #endif
2235         if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
2236                 debug_locks_off();
2237                 printk("BUG: MAX_LOCK_DEPTH too low!\n");
2238                 printk("turning off the locking correctness validator.\n");
2239                 return 0;
2240         }
2241
2242         if (unlikely(curr->lockdep_depth > max_lockdep_depth))
2243                 max_lockdep_depth = curr->lockdep_depth;
2244
2245         return 1;
2246 }
2247
2248 static int
2249 print_unlock_inbalance_bug(struct task_struct *curr, struct lockdep_map *lock,
2250                            unsigned long ip)
2251 {
2252         if (!debug_locks_off())
2253                 return 0;
2254         if (debug_locks_silent)
2255                 return 0;
2256
2257         printk("\n=====================================\n");
2258         printk(  "[ BUG: bad unlock balance detected! ]\n");
2259         printk(  "-------------------------------------\n");
2260         printk("%s/%d is trying to release lock (",
2261                 curr->comm, curr->pid);
2262         print_lockdep_cache(lock);
2263         printk(") at:\n");
2264         print_ip_sym(ip);
2265         printk("but there are no more locks to release!\n");
2266         printk("\nother info that might help us debug this:\n");
2267         lockdep_print_held_locks(curr);
2268
2269         printk("\nstack backtrace:\n");
2270         dump_stack();
2271
2272         return 0;
2273 }
2274
2275 /*
2276  * Common debugging checks for both nested and non-nested unlock:
2277  */
2278 static int check_unlock(struct task_struct *curr, struct lockdep_map *lock,
2279                         unsigned long ip)
2280 {
2281         if (unlikely(!debug_locks))
2282                 return 0;
2283         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2284                 return 0;
2285
2286         if (curr->lockdep_depth <= 0)
2287                 return print_unlock_inbalance_bug(curr, lock, ip);
2288
2289         return 1;
2290 }
2291
2292 /*
2293  * Remove the lock to the list of currently held locks in a
2294  * potentially non-nested (out of order) manner. This is a
2295  * relatively rare operation, as all the unlock APIs default
2296  * to nested mode (which uses lock_release()):
2297  */
2298 static int
2299 lock_release_non_nested(struct task_struct *curr,
2300                         struct lockdep_map *lock, unsigned long ip)
2301 {
2302         struct held_lock *hlock, *prev_hlock;
2303         unsigned int depth;
2304         int i;
2305
2306         /*
2307          * Check whether the lock exists in the current stack
2308          * of held locks:
2309          */
2310         depth = curr->lockdep_depth;
2311         if (DEBUG_LOCKS_WARN_ON(!depth))
2312                 return 0;
2313
2314         prev_hlock = NULL;
2315         for (i = depth-1; i >= 0; i--) {
2316                 hlock = curr->held_locks + i;
2317                 /*
2318                  * We must not cross into another context:
2319                  */
2320                 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
2321                         break;
2322                 if (hlock->instance == lock)
2323                         goto found_it;
2324                 prev_hlock = hlock;
2325         }
2326         return print_unlock_inbalance_bug(curr, lock, ip);
2327
2328 found_it:
2329         /*
2330          * We have the right lock to unlock, 'hlock' points to it.
2331          * Now we remove it from the stack, and add back the other
2332          * entries (if any), recalculating the hash along the way:
2333          */
2334         curr->lockdep_depth = i;
2335         curr->curr_chain_key = hlock->prev_chain_key;
2336
2337         for (i++; i < depth; i++) {
2338                 hlock = curr->held_locks + i;
2339                 if (!__lock_acquire(hlock->instance,
2340                         hlock->class->subclass, hlock->trylock,
2341                                 hlock->read, hlock->check, hlock->hardirqs_off,
2342                                 hlock->acquire_ip))
2343                         return 0;
2344         }
2345
2346         if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - 1))
2347                 return 0;
2348         return 1;
2349 }
2350
2351 /*
2352  * Remove the lock to the list of currently held locks - this gets
2353  * called on mutex_unlock()/spin_unlock*() (or on a failed
2354  * mutex_lock_interruptible()). This is done for unlocks that nest
2355  * perfectly. (i.e. the current top of the lock-stack is unlocked)
2356  */
2357 static int lock_release_nested(struct task_struct *curr,
2358                                struct lockdep_map *lock, unsigned long ip)
2359 {
2360         struct held_lock *hlock;
2361         unsigned int depth;
2362
2363         /*
2364          * Pop off the top of the lock stack:
2365          */
2366         depth = curr->lockdep_depth - 1;
2367         hlock = curr->held_locks + depth;
2368
2369         /*
2370          * Is the unlock non-nested:
2371          */
2372         if (hlock->instance != lock)
2373                 return lock_release_non_nested(curr, lock, ip);
2374         curr->lockdep_depth--;
2375
2376         if (DEBUG_LOCKS_WARN_ON(!depth && (hlock->prev_chain_key != 0)))
2377                 return 0;
2378
2379         curr->curr_chain_key = hlock->prev_chain_key;
2380
2381 #ifdef CONFIG_DEBUG_LOCKDEP
2382         hlock->prev_chain_key = 0;
2383         hlock->class = NULL;
2384         hlock->acquire_ip = 0;
2385         hlock->irq_context = 0;
2386 #endif
2387         return 1;
2388 }
2389
2390 /*
2391  * Remove the lock to the list of currently held locks - this gets
2392  * called on mutex_unlock()/spin_unlock*() (or on a failed
2393  * mutex_lock_interruptible()). This is done for unlocks that nest
2394  * perfectly. (i.e. the current top of the lock-stack is unlocked)
2395  */
2396 static void
2397 __lock_release(struct lockdep_map *lock, int nested, unsigned long ip)
2398 {
2399         struct task_struct *curr = current;
2400
2401         if (!check_unlock(curr, lock, ip))
2402                 return;
2403
2404         if (nested) {
2405                 if (!lock_release_nested(curr, lock, ip))
2406                         return;
2407         } else {
2408                 if (!lock_release_non_nested(curr, lock, ip))
2409                         return;
2410         }
2411
2412         check_chain_key(curr);
2413 }
2414
2415 /*
2416  * Check whether we follow the irq-flags state precisely:
2417  */
2418 static void check_flags(unsigned long flags)
2419 {
2420 #if defined(CONFIG_DEBUG_LOCKDEP) && defined(CONFIG_TRACE_IRQFLAGS)
2421         if (!debug_locks)
2422                 return;
2423
2424         if (irqs_disabled_flags(flags))
2425                 DEBUG_LOCKS_WARN_ON(current->hardirqs_enabled);
2426         else
2427                 DEBUG_LOCKS_WARN_ON(!current->hardirqs_enabled);
2428
2429         /*
2430          * We dont accurately track softirq state in e.g.
2431          * hardirq contexts (such as on 4KSTACKS), so only
2432          * check if not in hardirq contexts:
2433          */
2434         if (!hardirq_count()) {
2435                 if (softirq_count())
2436                         DEBUG_LOCKS_WARN_ON(current->softirqs_enabled);
2437                 else
2438                         DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled);
2439         }
2440
2441         if (!debug_locks)
2442                 print_irqtrace_events(current);
2443 #endif
2444 }
2445
2446 /*
2447  * We are not always called with irqs disabled - do that here,
2448  * and also avoid lockdep recursion:
2449  */
2450 void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
2451                   int trylock, int read, int check, unsigned long ip)
2452 {
2453         unsigned long flags;
2454
2455         if (unlikely(current->lockdep_recursion))
2456                 return;
2457
2458         raw_local_irq_save(flags);
2459         check_flags(flags);
2460
2461         current->lockdep_recursion = 1;
2462         __lock_acquire(lock, subclass, trylock, read, check,
2463                        irqs_disabled_flags(flags), ip);
2464         current->lockdep_recursion = 0;
2465         raw_local_irq_restore(flags);
2466 }
2467
2468 EXPORT_SYMBOL_GPL(lock_acquire);
2469
2470 void lock_release(struct lockdep_map *lock, int nested, unsigned long ip)
2471 {
2472         unsigned long flags;
2473
2474         if (unlikely(current->lockdep_recursion))
2475                 return;
2476
2477         raw_local_irq_save(flags);
2478         check_flags(flags);
2479         current->lockdep_recursion = 1;
2480         __lock_release(lock, nested, ip);
2481         current->lockdep_recursion = 0;
2482         raw_local_irq_restore(flags);
2483 }
2484
2485 EXPORT_SYMBOL_GPL(lock_release);
2486
2487 /*
2488  * Used by the testsuite, sanitize the validator state
2489  * after a simulated failure:
2490  */
2491
2492 void lockdep_reset(void)
2493 {
2494         unsigned long flags;
2495         int i;
2496
2497         raw_local_irq_save(flags);
2498         current->curr_chain_key = 0;
2499         current->lockdep_depth = 0;
2500         current->lockdep_recursion = 0;
2501         memset(current->held_locks, 0, MAX_LOCK_DEPTH*sizeof(struct held_lock));
2502         nr_hardirq_chains = 0;
2503         nr_softirq_chains = 0;
2504         nr_process_chains = 0;
2505         debug_locks = 1;
2506         for (i = 0; i < CHAINHASH_SIZE; i++)
2507                 INIT_LIST_HEAD(chainhash_table + i);
2508         raw_local_irq_restore(flags);
2509 }
2510
2511 static void zap_class(struct lock_class *class)
2512 {
2513         int i;
2514
2515         /*
2516          * Remove all dependencies this lock is
2517          * involved in:
2518          */
2519         for (i = 0; i < nr_list_entries; i++) {
2520                 if (list_entries[i].class == class)
2521                         list_del_rcu(&list_entries[i].entry);
2522         }
2523         /*
2524          * Unhash the class and remove it from the all_lock_classes list:
2525          */
2526         list_del_rcu(&class->hash_entry);
2527         list_del_rcu(&class->lock_entry);
2528
2529 }
2530
2531 static inline int within(void *addr, void *start, unsigned long size)
2532 {
2533         return addr >= start && addr < start + size;
2534 }
2535
2536 void lockdep_free_key_range(void *start, unsigned long size)
2537 {
2538         struct lock_class *class, *next;
2539         struct list_head *head;
2540         unsigned long flags;
2541         int i;
2542
2543         raw_local_irq_save(flags);
2544         graph_lock();
2545
2546         /*
2547          * Unhash all classes that were created by this module:
2548          */
2549         for (i = 0; i < CLASSHASH_SIZE; i++) {
2550                 head = classhash_table + i;
2551                 if (list_empty(head))
2552                         continue;
2553                 list_for_each_entry_safe(class, next, head, hash_entry)
2554                         if (within(class->key, start, size))
2555                                 zap_class(class);
2556         }
2557
2558         graph_unlock();
2559         raw_local_irq_restore(flags);
2560 }
2561
2562 void lockdep_reset_lock(struct lockdep_map *lock)
2563 {
2564         struct lock_class *class, *next;
2565         struct list_head *head;
2566         unsigned long flags;
2567         int i, j;
2568
2569         raw_local_irq_save(flags);
2570
2571         /*
2572          * Remove all classes this lock might have:
2573          */
2574         for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) {
2575                 /*
2576                  * If the class exists we look it up and zap it:
2577                  */
2578                 class = look_up_lock_class(lock, j);
2579                 if (class)
2580                         zap_class(class);
2581         }
2582         /*
2583          * Debug check: in the end all mapped classes should
2584          * be gone.
2585          */
2586         graph_lock();
2587         for (i = 0; i < CLASSHASH_SIZE; i++) {
2588                 head = classhash_table + i;
2589                 if (list_empty(head))
2590                         continue;
2591                 list_for_each_entry_safe(class, next, head, hash_entry) {
2592                         if (unlikely(class == lock->class_cache)) {
2593                                 if (debug_locks_off_graph_unlock())
2594                                         WARN_ON(1);
2595                                 goto out_restore;
2596                         }
2597                 }
2598         }
2599         graph_unlock();
2600
2601 out_restore:
2602         raw_local_irq_restore(flags);
2603 }
2604
2605 void lockdep_init(void)
2606 {
2607         int i;
2608
2609         /*
2610          * Some architectures have their own start_kernel()
2611          * code which calls lockdep_init(), while we also
2612          * call lockdep_init() from the start_kernel() itself,
2613          * and we want to initialize the hashes only once:
2614          */
2615         if (lockdep_initialized)
2616                 return;
2617
2618         for (i = 0; i < CLASSHASH_SIZE; i++)
2619                 INIT_LIST_HEAD(classhash_table + i);
2620
2621         for (i = 0; i < CHAINHASH_SIZE; i++)
2622                 INIT_LIST_HEAD(chainhash_table + i);
2623
2624         lockdep_initialized = 1;
2625 }
2626
2627 void __init lockdep_info(void)
2628 {
2629         printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");
2630
2631         printk("... MAX_LOCKDEP_SUBCLASSES:    %lu\n", MAX_LOCKDEP_SUBCLASSES);
2632         printk("... MAX_LOCK_DEPTH:          %lu\n", MAX_LOCK_DEPTH);
2633         printk("... MAX_LOCKDEP_KEYS:        %lu\n", MAX_LOCKDEP_KEYS);
2634         printk("... CLASSHASH_SIZE:           %lu\n", CLASSHASH_SIZE);
2635         printk("... MAX_LOCKDEP_ENTRIES:     %lu\n", MAX_LOCKDEP_ENTRIES);
2636         printk("... MAX_LOCKDEP_CHAINS:      %lu\n", MAX_LOCKDEP_CHAINS);
2637         printk("... CHAINHASH_SIZE:          %lu\n", CHAINHASH_SIZE);
2638
2639         printk(" memory used by lock dependency info: %lu kB\n",
2640                 (sizeof(struct lock_class) * MAX_LOCKDEP_KEYS +
2641                 sizeof(struct list_head) * CLASSHASH_SIZE +
2642                 sizeof(struct lock_list) * MAX_LOCKDEP_ENTRIES +
2643                 sizeof(struct lock_chain) * MAX_LOCKDEP_CHAINS +
2644                 sizeof(struct list_head) * CHAINHASH_SIZE) / 1024);
2645
2646         printk(" per task-struct memory footprint: %lu bytes\n",
2647                 sizeof(struct held_lock) * MAX_LOCK_DEPTH);
2648
2649 #ifdef CONFIG_DEBUG_LOCKDEP
2650         if (lockdep_init_error)
2651                 printk("WARNING: lockdep init error! Arch code didnt call lockdep_init() early enough?\n");
2652 #endif
2653 }
2654
2655 static inline int in_range(const void *start, const void *addr, const void *end)
2656 {
2657         return addr >= start && addr <= end;
2658 }
2659
2660 static void
2661 print_freed_lock_bug(struct task_struct *curr, const void *mem_from,
2662                      const void *mem_to, struct held_lock *hlock)
2663 {
2664         if (!debug_locks_off())
2665                 return;
2666         if (debug_locks_silent)
2667                 return;
2668
2669         printk("\n=========================\n");
2670         printk(  "[ BUG: held lock freed! ]\n");
2671         printk(  "-------------------------\n");
2672         printk("%s/%d is freeing memory %p-%p, with a lock still held there!\n",
2673                 curr->comm, curr->pid, mem_from, mem_to-1);
2674         print_lock(hlock);
2675         lockdep_print_held_locks(curr);
2676
2677         printk("\nstack backtrace:\n");
2678         dump_stack();
2679 }
2680
2681 /*
2682  * Called when kernel memory is freed (or unmapped), or if a lock
2683  * is destroyed or reinitialized - this code checks whether there is
2684  * any held lock in the memory range of <from> to <to>:
2685  */
2686 void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len)
2687 {
2688         const void *mem_to = mem_from + mem_len, *lock_from, *lock_to;
2689         struct task_struct *curr = current;
2690         struct held_lock *hlock;
2691         unsigned long flags;
2692         int i;
2693
2694         if (unlikely(!debug_locks))
2695                 return;
2696
2697         local_irq_save(flags);
2698         for (i = 0; i < curr->lockdep_depth; i++) {
2699                 hlock = curr->held_locks + i;
2700
2701                 lock_from = (void *)hlock->instance;
2702                 lock_to = (void *)(hlock->instance + 1);
2703
2704                 if (!in_range(mem_from, lock_from, mem_to) &&
2705                                         !in_range(mem_from, lock_to, mem_to))
2706                         continue;
2707
2708                 print_freed_lock_bug(curr, mem_from, mem_to, hlock);
2709                 break;
2710         }
2711         local_irq_restore(flags);
2712 }
2713 EXPORT_SYMBOL_GPL(debug_check_no_locks_freed);
2714
2715 static void print_held_locks_bug(struct task_struct *curr)
2716 {
2717         if (!debug_locks_off())
2718                 return;
2719         if (debug_locks_silent)
2720                 return;
2721
2722         printk("\n=====================================\n");
2723         printk(  "[ BUG: lock held at task exit time! ]\n");
2724         printk(  "-------------------------------------\n");
2725         printk("%s/%d is exiting with locks still held!\n",
2726                 curr->comm, curr->pid);
2727         lockdep_print_held_locks(curr);
2728
2729         printk("\nstack backtrace:\n");
2730         dump_stack();
2731 }
2732
2733 void debug_check_no_locks_held(struct task_struct *task)
2734 {
2735         if (unlikely(task->lockdep_depth > 0))
2736                 print_held_locks_bug(task);
2737 }
2738
2739 void debug_show_all_locks(void)
2740 {
2741         struct task_struct *g, *p;
2742         int count = 10;
2743         int unlock = 1;
2744
2745         printk("\nShowing all locks held in the system:\n");
2746
2747         /*
2748          * Here we try to get the tasklist_lock as hard as possible,
2749          * if not successful after 2 seconds we ignore it (but keep
2750          * trying). This is to enable a debug printout even if a
2751          * tasklist_lock-holding task deadlocks or crashes.
2752          */
2753 retry:
2754         if (!read_trylock(&tasklist_lock)) {
2755                 if (count == 10)
2756                         printk("hm, tasklist_lock locked, retrying... ");
2757                 if (count) {
2758                         count--;
2759                         printk(" #%d", 10-count);
2760                         mdelay(200);
2761                         goto retry;
2762                 }
2763                 printk(" ignoring it.\n");
2764                 unlock = 0;
2765         }
2766         if (count != 10)
2767                 printk(" locked it.\n");
2768
2769         do_each_thread(g, p) {
2770                 if (p->lockdep_depth)
2771                         lockdep_print_held_locks(p);
2772                 if (!unlock)
2773                         if (read_trylock(&tasklist_lock))
2774                                 unlock = 1;
2775         } while_each_thread(g, p);
2776
2777         printk("\n");
2778         printk("=============================================\n\n");
2779
2780         if (unlock)
2781                 read_unlock(&tasklist_lock);
2782 }
2783
2784 EXPORT_SYMBOL_GPL(debug_show_all_locks);
2785
2786 void debug_show_held_locks(struct task_struct *task)
2787 {
2788         lockdep_print_held_locks(task);
2789 }
2790
2791 EXPORT_SYMBOL_GPL(debug_show_held_locks);