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TOMOYO Linux Cross Reference
Linux/kernel/locking/lockdep.c

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  1 /*
  2  * kernel/lockdep.c
  3  *
  4  * Runtime locking correctness validator
  5  *
  6  * Started by Ingo Molnar:
  7  *
  8  *  Copyright (C) 2006,2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
  9  *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
 10  *
 11  * this code maps all the lock dependencies as they occur in a live kernel
 12  * and will warn about the following classes of locking bugs:
 13  *
 14  * - lock inversion scenarios
 15  * - circular lock dependencies
 16  * - hardirq/softirq safe/unsafe locking bugs
 17  *
 18  * Bugs are reported even if the current locking scenario does not cause
 19  * any deadlock at this point.
 20  *
 21  * I.e. if anytime in the past two locks were taken in a different order,
 22  * even if it happened for another task, even if those were different
 23  * locks (but of the same class as this lock), this code will detect it.
 24  *
 25  * Thanks to Arjan van de Ven for coming up with the initial idea of
 26  * mapping lock dependencies runtime.
 27  */
 28 #define DISABLE_BRANCH_PROFILING
 29 #include <linux/mutex.h>
 30 #include <linux/sched.h>
 31 #include <linux/delay.h>
 32 #include <linux/module.h>
 33 #include <linux/proc_fs.h>
 34 #include <linux/seq_file.h>
 35 #include <linux/spinlock.h>
 36 #include <linux/kallsyms.h>
 37 #include <linux/interrupt.h>
 38 #include <linux/stacktrace.h>
 39 #include <linux/debug_locks.h>
 40 #include <linux/irqflags.h>
 41 #include <linux/utsname.h>
 42 #include <linux/hash.h>
 43 #include <linux/ftrace.h>
 44 #include <linux/stringify.h>
 45 #include <linux/bitops.h>
 46 #include <linux/gfp.h>
 47 #include <linux/kmemcheck.h>
 48 #include <linux/random.h>
 49 
 50 #include <asm/sections.h>
 51 
 52 #include "lockdep_internals.h"
 53 
 54 #define CREATE_TRACE_POINTS
 55 #include <trace/events/lock.h>
 56 
 57 #ifdef CONFIG_PROVE_LOCKING
 58 int prove_locking = 1;
 59 module_param(prove_locking, int, 0644);
 60 #else
 61 #define prove_locking 0
 62 #endif
 63 
 64 #ifdef CONFIG_LOCK_STAT
 65 int lock_stat = 1;
 66 module_param(lock_stat, int, 0644);
 67 #else
 68 #define lock_stat 0
 69 #endif
 70 
 71 /*
 72  * lockdep_lock: protects the lockdep graph, the hashes and the
 73  *               class/list/hash allocators.
 74  *
 75  * This is one of the rare exceptions where it's justified
 76  * to use a raw spinlock - we really dont want the spinlock
 77  * code to recurse back into the lockdep code...
 78  */
 79 static arch_spinlock_t lockdep_lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
 80 
 81 static int graph_lock(void)
 82 {
 83         arch_spin_lock(&lockdep_lock);
 84         /*
 85          * Make sure that if another CPU detected a bug while
 86          * walking the graph we dont change it (while the other
 87          * CPU is busy printing out stuff with the graph lock
 88          * dropped already)
 89          */
 90         if (!debug_locks) {
 91                 arch_spin_unlock(&lockdep_lock);
 92                 return 0;
 93         }
 94         /* prevent any recursions within lockdep from causing deadlocks */
 95         current->lockdep_recursion++;
 96         return 1;
 97 }
 98 
 99 static inline int graph_unlock(void)
100 {
101         if (debug_locks && !arch_spin_is_locked(&lockdep_lock)) {
102                 /*
103                  * The lockdep graph lock isn't locked while we expect it to
104                  * be, we're confused now, bye!
105                  */
106                 return DEBUG_LOCKS_WARN_ON(1);
107         }
108 
109         current->lockdep_recursion--;
110         arch_spin_unlock(&lockdep_lock);
111         return 0;
112 }
113 
114 /*
115  * Turn lock debugging off and return with 0 if it was off already,
116  * and also release the graph lock:
117  */
118 static inline int debug_locks_off_graph_unlock(void)
119 {
120         int ret = debug_locks_off();
121 
122         arch_spin_unlock(&lockdep_lock);
123 
124         return ret;
125 }
126 
127 unsigned long nr_list_entries;
128 static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES];
129 
130 /*
131  * All data structures here are protected by the global debug_lock.
132  *
133  * Mutex key structs only get allocated, once during bootup, and never
134  * get freed - this significantly simplifies the debugging code.
135  */
136 unsigned long nr_lock_classes;
137 static struct lock_class lock_classes[MAX_LOCKDEP_KEYS];
138 
139 static inline struct lock_class *hlock_class(struct held_lock *hlock)
140 {
141         if (!hlock->class_idx) {
142                 /*
143                  * Someone passed in garbage, we give up.
144                  */
145                 DEBUG_LOCKS_WARN_ON(1);
146                 return NULL;
147         }
148         return lock_classes + hlock->class_idx - 1;
149 }
150 
151 #ifdef CONFIG_LOCK_STAT
152 static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS], cpu_lock_stats);
153 
154 static inline u64 lockstat_clock(void)
155 {
156         return local_clock();
157 }
158 
159 static int lock_point(unsigned long points[], unsigned long ip)
160 {
161         int i;
162 
163         for (i = 0; i < LOCKSTAT_POINTS; i++) {
164                 if (points[i] == 0) {
165                         points[i] = ip;
166                         break;
167                 }
168                 if (points[i] == ip)
169                         break;
170         }
171 
172         return i;
173 }
174 
175 static void lock_time_inc(struct lock_time *lt, u64 time)
176 {
177         if (time > lt->max)
178                 lt->max = time;
179 
180         if (time < lt->min || !lt->nr)
181                 lt->min = time;
182 
183         lt->total += time;
184         lt->nr++;
185 }
186 
187 static inline void lock_time_add(struct lock_time *src, struct lock_time *dst)
188 {
189         if (!src->nr)
190                 return;
191 
192         if (src->max > dst->max)
193                 dst->max = src->max;
194 
195         if (src->min < dst->min || !dst->nr)
196                 dst->min = src->min;
197 
198         dst->total += src->total;
199         dst->nr += src->nr;
200 }
201 
202 struct lock_class_stats lock_stats(struct lock_class *class)
203 {
204         struct lock_class_stats stats;
205         int cpu, i;
206 
207         memset(&stats, 0, sizeof(struct lock_class_stats));
208         for_each_possible_cpu(cpu) {
209                 struct lock_class_stats *pcs =
210                         &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
211 
212                 for (i = 0; i < ARRAY_SIZE(stats.contention_point); i++)
213                         stats.contention_point[i] += pcs->contention_point[i];
214 
215                 for (i = 0; i < ARRAY_SIZE(stats.contending_point); i++)
216                         stats.contending_point[i] += pcs->contending_point[i];
217 
218                 lock_time_add(&pcs->read_waittime, &stats.read_waittime);
219                 lock_time_add(&pcs->write_waittime, &stats.write_waittime);
220 
221                 lock_time_add(&pcs->read_holdtime, &stats.read_holdtime);
222                 lock_time_add(&pcs->write_holdtime, &stats.write_holdtime);
223 
224                 for (i = 0; i < ARRAY_SIZE(stats.bounces); i++)
225                         stats.bounces[i] += pcs->bounces[i];
226         }
227 
228         return stats;
229 }
230 
231 void clear_lock_stats(struct lock_class *class)
232 {
233         int cpu;
234 
235         for_each_possible_cpu(cpu) {
236                 struct lock_class_stats *cpu_stats =
237                         &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
238 
239                 memset(cpu_stats, 0, sizeof(struct lock_class_stats));
240         }
241         memset(class->contention_point, 0, sizeof(class->contention_point));
242         memset(class->contending_point, 0, sizeof(class->contending_point));
243 }
244 
245 static struct lock_class_stats *get_lock_stats(struct lock_class *class)
246 {
247         return &get_cpu_var(cpu_lock_stats)[class - lock_classes];
248 }
249 
250 static void put_lock_stats(struct lock_class_stats *stats)
251 {
252         put_cpu_var(cpu_lock_stats);
253 }
254 
255 static void lock_release_holdtime(struct held_lock *hlock)
256 {
257         struct lock_class_stats *stats;
258         u64 holdtime;
259 
260         if (!lock_stat)
261                 return;
262 
263         holdtime = lockstat_clock() - hlock->holdtime_stamp;
264 
265         stats = get_lock_stats(hlock_class(hlock));
266         if (hlock->read)
267                 lock_time_inc(&stats->read_holdtime, holdtime);
268         else
269                 lock_time_inc(&stats->write_holdtime, holdtime);
270         put_lock_stats(stats);
271 }
272 #else
273 static inline void lock_release_holdtime(struct held_lock *hlock)
274 {
275 }
276 #endif
277 
278 /*
279  * We keep a global list of all lock classes. The list only grows,
280  * never shrinks. The list is only accessed with the lockdep
281  * spinlock lock held.
282  */
283 LIST_HEAD(all_lock_classes);
284 
285 /*
286  * The lockdep classes are in a hash-table as well, for fast lookup:
287  */
288 #define CLASSHASH_BITS          (MAX_LOCKDEP_KEYS_BITS - 1)
289 #define CLASSHASH_SIZE          (1UL << CLASSHASH_BITS)
290 #define __classhashfn(key)      hash_long((unsigned long)key, CLASSHASH_BITS)
291 #define classhashentry(key)     (classhash_table + __classhashfn((key)))
292 
293 static struct hlist_head classhash_table[CLASSHASH_SIZE];
294 
295 /*
296  * We put the lock dependency chains into a hash-table as well, to cache
297  * their existence:
298  */
299 #define CHAINHASH_BITS          (MAX_LOCKDEP_CHAINS_BITS-1)
300 #define CHAINHASH_SIZE          (1UL << CHAINHASH_BITS)
301 #define __chainhashfn(chain)    hash_long(chain, CHAINHASH_BITS)
302 #define chainhashentry(chain)   (chainhash_table + __chainhashfn((chain)))
303 
304 static struct hlist_head chainhash_table[CHAINHASH_SIZE];
305 
306 /*
307  * The hash key of the lock dependency chains is a hash itself too:
308  * it's a hash of all locks taken up to that lock, including that lock.
309  * It's a 64-bit hash, because it's important for the keys to be
310  * unique.
311  */
312 #define iterate_chain_key(key1, key2) \
313         (((key1) << MAX_LOCKDEP_KEYS_BITS) ^ \
314         ((key1) >> (64-MAX_LOCKDEP_KEYS_BITS)) ^ \
315         (key2))
316 
317 void lockdep_off(void)
318 {
319         current->lockdep_recursion++;
320 }
321 EXPORT_SYMBOL(lockdep_off);
322 
323 void lockdep_on(void)
324 {
325         current->lockdep_recursion--;
326 }
327 EXPORT_SYMBOL(lockdep_on);
328 
329 /*
330  * Debugging switches:
331  */
332 
333 #define VERBOSE                 0
334 #define VERY_VERBOSE            0
335 
336 #if VERBOSE
337 # define HARDIRQ_VERBOSE        1
338 # define SOFTIRQ_VERBOSE        1
339 # define RECLAIM_VERBOSE        1
340 #else
341 # define HARDIRQ_VERBOSE        0
342 # define SOFTIRQ_VERBOSE        0
343 # define RECLAIM_VERBOSE        0
344 #endif
345 
346 #if VERBOSE || HARDIRQ_VERBOSE || SOFTIRQ_VERBOSE || RECLAIM_VERBOSE
347 /*
348  * Quick filtering for interesting events:
349  */
350 static int class_filter(struct lock_class *class)
351 {
352 #if 0
353         /* Example */
354         if (class->name_version == 1 &&
355                         !strcmp(class->name, "lockname"))
356                 return 1;
357         if (class->name_version == 1 &&
358                         !strcmp(class->name, "&struct->lockfield"))
359                 return 1;
360 #endif
361         /* Filter everything else. 1 would be to allow everything else */
362         return 0;
363 }
364 #endif
365 
366 static int verbose(struct lock_class *class)
367 {
368 #if VERBOSE
369         return class_filter(class);
370 #endif
371         return 0;
372 }
373 
374 /*
375  * Stack-trace: tightly packed array of stack backtrace
376  * addresses. Protected by the graph_lock.
377  */
378 unsigned long nr_stack_trace_entries;
379 static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];
380 
381 static void print_lockdep_off(const char *bug_msg)
382 {
383         printk(KERN_DEBUG "%s\n", bug_msg);
384         printk(KERN_DEBUG "turning off the locking correctness validator.\n");
385 #ifdef CONFIG_LOCK_STAT
386         printk(KERN_DEBUG "Please attach the output of /proc/lock_stat to the bug report\n");
387 #endif
388 }
389 
390 static int save_trace(struct stack_trace *trace)
391 {
392         trace->nr_entries = 0;
393         trace->max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries;
394         trace->entries = stack_trace + nr_stack_trace_entries;
395 
396         trace->skip = 3;
397 
398         save_stack_trace(trace);
399 
400         /*
401          * Some daft arches put -1 at the end to indicate its a full trace.
402          *
403          * <rant> this is buggy anyway, since it takes a whole extra entry so a
404          * complete trace that maxes out the entries provided will be reported
405          * as incomplete, friggin useless </rant>
406          */
407         if (trace->nr_entries != 0 &&
408             trace->entries[trace->nr_entries-1] == ULONG_MAX)
409                 trace->nr_entries--;
410 
411         trace->max_entries = trace->nr_entries;
412 
413         nr_stack_trace_entries += trace->nr_entries;
414 
415         if (nr_stack_trace_entries >= MAX_STACK_TRACE_ENTRIES-1) {
416                 if (!debug_locks_off_graph_unlock())
417                         return 0;
418 
419                 print_lockdep_off("BUG: MAX_STACK_TRACE_ENTRIES too low!");
420                 dump_stack();
421 
422                 return 0;
423         }
424 
425         return 1;
426 }
427 
428 unsigned int nr_hardirq_chains;
429 unsigned int nr_softirq_chains;
430 unsigned int nr_process_chains;
431 unsigned int max_lockdep_depth;
432 
433 #ifdef CONFIG_DEBUG_LOCKDEP
434 /*
435  * Various lockdep statistics:
436  */
437 DEFINE_PER_CPU(struct lockdep_stats, lockdep_stats);
438 #endif
439 
440 /*
441  * Locking printouts:
442  */
443 
444 #define __USAGE(__STATE)                                                \
445         [LOCK_USED_IN_##__STATE] = "IN-"__stringify(__STATE)"-W",       \
446         [LOCK_ENABLED_##__STATE] = __stringify(__STATE)"-ON-W",         \
447         [LOCK_USED_IN_##__STATE##_READ] = "IN-"__stringify(__STATE)"-R",\
448         [LOCK_ENABLED_##__STATE##_READ] = __stringify(__STATE)"-ON-R",
449 
450 static const char *usage_str[] =
451 {
452 #define LOCKDEP_STATE(__STATE) __USAGE(__STATE)
453 #include "lockdep_states.h"
454 #undef LOCKDEP_STATE
455         [LOCK_USED] = "INITIAL USE",
456 };
457 
458 const char * __get_key_name(struct lockdep_subclass_key *key, char *str)
459 {
460         return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str);
461 }
462 
463 static inline unsigned long lock_flag(enum lock_usage_bit bit)
464 {
465         return 1UL << bit;
466 }
467 
468 static char get_usage_char(struct lock_class *class, enum lock_usage_bit bit)
469 {
470         char c = '.';
471 
472         if (class->usage_mask & lock_flag(bit + 2))
473                 c = '+';
474         if (class->usage_mask & lock_flag(bit)) {
475                 c = '-';
476                 if (class->usage_mask & lock_flag(bit + 2))
477                         c = '?';
478         }
479 
480         return c;
481 }
482 
483 void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS])
484 {
485         int i = 0;
486 
487 #define LOCKDEP_STATE(__STATE)                                          \
488         usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE);     \
489         usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE##_READ);
490 #include "lockdep_states.h"
491 #undef LOCKDEP_STATE
492 
493         usage[i] = '\0';
494 }
495 
496 static void __print_lock_name(struct lock_class *class)
497 {
498         char str[KSYM_NAME_LEN];
499         const char *name;
500 
501         name = class->name;
502         if (!name) {
503                 name = __get_key_name(class->key, str);
504                 printk("%s", name);
505         } else {
506                 printk("%s", name);
507                 if (class->name_version > 1)
508                         printk("#%d", class->name_version);
509                 if (class->subclass)
510                         printk("/%d", class->subclass);
511         }
512 }
513 
514 static void print_lock_name(struct lock_class *class)
515 {
516         char usage[LOCK_USAGE_CHARS];
517 
518         get_usage_chars(class, usage);
519 
520         printk(" (");
521         __print_lock_name(class);
522         printk("){%s}", usage);
523 }
524 
525 static void print_lockdep_cache(struct lockdep_map *lock)
526 {
527         const char *name;
528         char str[KSYM_NAME_LEN];
529 
530         name = lock->name;
531         if (!name)
532                 name = __get_key_name(lock->key->subkeys, str);
533 
534         printk("%s", name);
535 }
536 
537 static void print_lock(struct held_lock *hlock)
538 {
539         /*
540          * We can be called locklessly through debug_show_all_locks() so be
541          * extra careful, the hlock might have been released and cleared.
542          */
543         unsigned int class_idx = hlock->class_idx;
544 
545         /* Don't re-read hlock->class_idx, can't use READ_ONCE() on bitfields: */
546         barrier();
547 
548         if (!class_idx || (class_idx - 1) >= MAX_LOCKDEP_KEYS) {
549                 printk("<RELEASED>\n");
550                 return;
551         }
552 
553         print_lock_name(lock_classes + class_idx - 1);
554         printk(", at: ");
555         print_ip_sym(hlock->acquire_ip);
556 }
557 
558 static void lockdep_print_held_locks(struct task_struct *curr)
559 {
560         int i, depth = curr->lockdep_depth;
561 
562         if (!depth) {
563                 printk("no locks held by %s/%d.\n", curr->comm, task_pid_nr(curr));
564                 return;
565         }
566         printk("%d lock%s held by %s/%d:\n",
567                 depth, depth > 1 ? "s" : "", curr->comm, task_pid_nr(curr));
568 
569         for (i = 0; i < depth; i++) {
570                 printk(" #%d: ", i);
571                 print_lock(curr->held_locks + i);
572         }
573 }
574 
575 static void print_kernel_ident(void)
576 {
577         printk("%s %.*s %s\n", init_utsname()->release,
578                 (int)strcspn(init_utsname()->version, " "),
579                 init_utsname()->version,
580                 print_tainted());
581 }
582 
583 static int very_verbose(struct lock_class *class)
584 {
585 #if VERY_VERBOSE
586         return class_filter(class);
587 #endif
588         return 0;
589 }
590 
591 /*
592  * Is this the address of a static object:
593  */
594 #ifdef __KERNEL__
595 static int static_obj(void *obj)
596 {
597         unsigned long start = (unsigned long) &_stext,
598                       end   = (unsigned long) &_end,
599                       addr  = (unsigned long) obj;
600 
601         /*
602          * static variable?
603          */
604         if ((addr >= start) && (addr < end))
605                 return 1;
606 
607         if (arch_is_kernel_data(addr))
608                 return 1;
609 
610         /*
611          * in-kernel percpu var?
612          */
613         if (is_kernel_percpu_address(addr))
614                 return 1;
615 
616         /*
617          * module static or percpu var?
618          */
619         return is_module_address(addr) || is_module_percpu_address(addr);
620 }
621 #endif
622 
623 /*
624  * To make lock name printouts unique, we calculate a unique
625  * class->name_version generation counter:
626  */
627 static int count_matching_names(struct lock_class *new_class)
628 {
629         struct lock_class *class;
630         int count = 0;
631 
632         if (!new_class->name)
633                 return 0;
634 
635         list_for_each_entry_rcu(class, &all_lock_classes, lock_entry) {
636                 if (new_class->key - new_class->subclass == class->key)
637                         return class->name_version;
638                 if (class->name && !strcmp(class->name, new_class->name))
639                         count = max(count, class->name_version);
640         }
641 
642         return count + 1;
643 }
644 
645 /*
646  * Register a lock's class in the hash-table, if the class is not present
647  * yet. Otherwise we look it up. We cache the result in the lock object
648  * itself, so actual lookup of the hash should be once per lock object.
649  */
650 static inline struct lock_class *
651 look_up_lock_class(struct lockdep_map *lock, unsigned int subclass)
652 {
653         struct lockdep_subclass_key *key;
654         struct hlist_head *hash_head;
655         struct lock_class *class;
656 
657         if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
658                 debug_locks_off();
659                 printk(KERN_ERR
660                         "BUG: looking up invalid subclass: %u\n", subclass);
661                 printk(KERN_ERR
662                         "turning off the locking correctness validator.\n");
663                 dump_stack();
664                 return NULL;
665         }
666 
667         /*
668          * Static locks do not have their class-keys yet - for them the key
669          * is the lock object itself:
670          */
671         if (unlikely(!lock->key))
672                 lock->key = (void *)lock;
673 
674         /*
675          * NOTE: the class-key must be unique. For dynamic locks, a static
676          * lock_class_key variable is passed in through the mutex_init()
677          * (or spin_lock_init()) call - which acts as the key. For static
678          * locks we use the lock object itself as the key.
679          */
680         BUILD_BUG_ON(sizeof(struct lock_class_key) >
681                         sizeof(struct lockdep_map));
682 
683         key = lock->key->subkeys + subclass;
684 
685         hash_head = classhashentry(key);
686 
687         /*
688          * We do an RCU walk of the hash, see lockdep_free_key_range().
689          */
690         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
691                 return NULL;
692 
693         hlist_for_each_entry_rcu(class, hash_head, hash_entry) {
694                 if (class->key == key) {
695                         /*
696                          * Huh! same key, different name? Did someone trample
697                          * on some memory? We're most confused.
698                          */
699                         WARN_ON_ONCE(class->name != lock->name);
700                         return class;
701                 }
702         }
703 
704         return NULL;
705 }
706 
707 /*
708  * Register a lock's class in the hash-table, if the class is not present
709  * yet. Otherwise we look it up. We cache the result in the lock object
710  * itself, so actual lookup of the hash should be once per lock object.
711  */
712 static struct lock_class *
713 register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
714 {
715         struct lockdep_subclass_key *key;
716         struct hlist_head *hash_head;
717         struct lock_class *class;
718 
719         DEBUG_LOCKS_WARN_ON(!irqs_disabled());
720 
721         class = look_up_lock_class(lock, subclass);
722         if (likely(class))
723                 goto out_set_class_cache;
724 
725         /*
726          * Debug-check: all keys must be persistent!
727          */
728         if (!static_obj(lock->key)) {
729                 debug_locks_off();
730                 printk("INFO: trying to register non-static key.\n");
731                 printk("the code is fine but needs lockdep annotation.\n");
732                 printk("turning off the locking correctness validator.\n");
733                 dump_stack();
734 
735                 return NULL;
736         }
737 
738         key = lock->key->subkeys + subclass;
739         hash_head = classhashentry(key);
740 
741         if (!graph_lock()) {
742                 return NULL;
743         }
744         /*
745          * We have to do the hash-walk again, to avoid races
746          * with another CPU:
747          */
748         hlist_for_each_entry_rcu(class, hash_head, hash_entry) {
749                 if (class->key == key)
750                         goto out_unlock_set;
751         }
752 
753         /*
754          * Allocate a new key from the static array, and add it to
755          * the hash:
756          */
757         if (nr_lock_classes >= MAX_LOCKDEP_KEYS) {
758                 if (!debug_locks_off_graph_unlock()) {
759                         return NULL;
760                 }
761 
762                 print_lockdep_off("BUG: MAX_LOCKDEP_KEYS too low!");
763                 dump_stack();
764                 return NULL;
765         }
766         class = lock_classes + nr_lock_classes++;
767         debug_atomic_inc(nr_unused_locks);
768         class->key = key;
769         class->name = lock->name;
770         class->subclass = subclass;
771         INIT_LIST_HEAD(&class->lock_entry);
772         INIT_LIST_HEAD(&class->locks_before);
773         INIT_LIST_HEAD(&class->locks_after);
774         class->name_version = count_matching_names(class);
775         /*
776          * We use RCU's safe list-add method to make
777          * parallel walking of the hash-list safe:
778          */
779         hlist_add_head_rcu(&class->hash_entry, hash_head);
780         /*
781          * Add it to the global list of classes:
782          */
783         list_add_tail_rcu(&class->lock_entry, &all_lock_classes);
784 
785         if (verbose(class)) {
786                 graph_unlock();
787 
788                 printk("\nnew class %p: %s", class->key, class->name);
789                 if (class->name_version > 1)
790                         printk("#%d", class->name_version);
791                 printk("\n");
792                 dump_stack();
793 
794                 if (!graph_lock()) {
795                         return NULL;
796                 }
797         }
798 out_unlock_set:
799         graph_unlock();
800 
801 out_set_class_cache:
802         if (!subclass || force)
803                 lock->class_cache[0] = class;
804         else if (subclass < NR_LOCKDEP_CACHING_CLASSES)
805                 lock->class_cache[subclass] = class;
806 
807         /*
808          * Hash collision, did we smoke some? We found a class with a matching
809          * hash but the subclass -- which is hashed in -- didn't match.
810          */
811         if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))
812                 return NULL;
813 
814         return class;
815 }
816 
817 #ifdef CONFIG_PROVE_LOCKING
818 /*
819  * Allocate a lockdep entry. (assumes the graph_lock held, returns
820  * with NULL on failure)
821  */
822 static struct lock_list *alloc_list_entry(void)
823 {
824         if (nr_list_entries >= MAX_LOCKDEP_ENTRIES) {
825                 if (!debug_locks_off_graph_unlock())
826                         return NULL;
827 
828                 print_lockdep_off("BUG: MAX_LOCKDEP_ENTRIES too low!");
829                 dump_stack();
830                 return NULL;
831         }
832         return list_entries + nr_list_entries++;
833 }
834 
835 /*
836  * Add a new dependency to the head of the list:
837  */
838 static int add_lock_to_list(struct lock_class *class, struct lock_class *this,
839                             struct list_head *head, unsigned long ip,
840                             int distance, struct stack_trace *trace)
841 {
842         struct lock_list *entry;
843         /*
844          * Lock not present yet - get a new dependency struct and
845          * add it to the list:
846          */
847         entry = alloc_list_entry();
848         if (!entry)
849                 return 0;
850 
851         entry->class = this;
852         entry->distance = distance;
853         entry->trace = *trace;
854         /*
855          * Both allocation and removal are done under the graph lock; but
856          * iteration is under RCU-sched; see look_up_lock_class() and
857          * lockdep_free_key_range().
858          */
859         list_add_tail_rcu(&entry->entry, head);
860 
861         return 1;
862 }
863 
864 /*
865  * For good efficiency of modular, we use power of 2
866  */
867 #define MAX_CIRCULAR_QUEUE_SIZE         4096UL
868 #define CQ_MASK                         (MAX_CIRCULAR_QUEUE_SIZE-1)
869 
870 /*
871  * The circular_queue and helpers is used to implement the
872  * breadth-first search(BFS)algorithem, by which we can build
873  * the shortest path from the next lock to be acquired to the
874  * previous held lock if there is a circular between them.
875  */
876 struct circular_queue {
877         unsigned long element[MAX_CIRCULAR_QUEUE_SIZE];
878         unsigned int  front, rear;
879 };
880 
881 static struct circular_queue lock_cq;
882 
883 unsigned int max_bfs_queue_depth;
884 
885 static unsigned int lockdep_dependency_gen_id;
886 
887 static inline void __cq_init(struct circular_queue *cq)
888 {
889         cq->front = cq->rear = 0;
890         lockdep_dependency_gen_id++;
891 }
892 
893 static inline int __cq_empty(struct circular_queue *cq)
894 {
895         return (cq->front == cq->rear);
896 }
897 
898 static inline int __cq_full(struct circular_queue *cq)
899 {
900         return ((cq->rear + 1) & CQ_MASK) == cq->front;
901 }
902 
903 static inline int __cq_enqueue(struct circular_queue *cq, unsigned long elem)
904 {
905         if (__cq_full(cq))
906                 return -1;
907 
908         cq->element[cq->rear] = elem;
909         cq->rear = (cq->rear + 1) & CQ_MASK;
910         return 0;
911 }
912 
913 static inline int __cq_dequeue(struct circular_queue *cq, unsigned long *elem)
914 {
915         if (__cq_empty(cq))
916                 return -1;
917 
918         *elem = cq->element[cq->front];
919         cq->front = (cq->front + 1) & CQ_MASK;
920         return 0;
921 }
922 
923 static inline unsigned int  __cq_get_elem_count(struct circular_queue *cq)
924 {
925         return (cq->rear - cq->front) & CQ_MASK;
926 }
927 
928 static inline void mark_lock_accessed(struct lock_list *lock,
929                                         struct lock_list *parent)
930 {
931         unsigned long nr;
932 
933         nr = lock - list_entries;
934         WARN_ON(nr >= nr_list_entries); /* Out-of-bounds, input fail */
935         lock->parent = parent;
936         lock->class->dep_gen_id = lockdep_dependency_gen_id;
937 }
938 
939 static inline unsigned long lock_accessed(struct lock_list *lock)
940 {
941         unsigned long nr;
942 
943         nr = lock - list_entries;
944         WARN_ON(nr >= nr_list_entries); /* Out-of-bounds, input fail */
945         return lock->class->dep_gen_id == lockdep_dependency_gen_id;
946 }
947 
948 static inline struct lock_list *get_lock_parent(struct lock_list *child)
949 {
950         return child->parent;
951 }
952 
953 static inline int get_lock_depth(struct lock_list *child)
954 {
955         int depth = 0;
956         struct lock_list *parent;
957 
958         while ((parent = get_lock_parent(child))) {
959                 child = parent;
960                 depth++;
961         }
962         return depth;
963 }
964 
965 static int __bfs(struct lock_list *source_entry,
966                  void *data,
967                  int (*match)(struct lock_list *entry, void *data),
968                  struct lock_list **target_entry,
969                  int forward)
970 {
971         struct lock_list *entry;
972         struct list_head *head;
973         struct circular_queue *cq = &lock_cq;
974         int ret = 1;
975 
976         if (match(source_entry, data)) {
977                 *target_entry = source_entry;
978                 ret = 0;
979                 goto exit;
980         }
981 
982         if (forward)
983                 head = &source_entry->class->locks_after;
984         else
985                 head = &source_entry->class->locks_before;
986 
987         if (list_empty(head))
988                 goto exit;
989 
990         __cq_init(cq);
991         __cq_enqueue(cq, (unsigned long)source_entry);
992 
993         while (!__cq_empty(cq)) {
994                 struct lock_list *lock;
995 
996                 __cq_dequeue(cq, (unsigned long *)&lock);
997 
998                 if (!lock->class) {
999                         ret = -2;
1000                         goto exit;
1001                 }
1002 
1003                 if (forward)
1004                         head = &lock->class->locks_after;
1005                 else
1006                         head = &lock->class->locks_before;
1007 
1008                 DEBUG_LOCKS_WARN_ON(!irqs_disabled());
1009 
1010                 list_for_each_entry_rcu(entry, head, entry) {
1011                         if (!lock_accessed(entry)) {
1012                                 unsigned int cq_depth;
1013                                 mark_lock_accessed(entry, lock);
1014                                 if (match(entry, data)) {
1015                                         *target_entry = entry;
1016                                         ret = 0;
1017                                         goto exit;
1018                                 }
1019 
1020                                 if (__cq_enqueue(cq, (unsigned long)entry)) {
1021                                         ret = -1;
1022                                         goto exit;
1023                                 }
1024                                 cq_depth = __cq_get_elem_count(cq);
1025                                 if (max_bfs_queue_depth < cq_depth)
1026                                         max_bfs_queue_depth = cq_depth;
1027                         }
1028                 }
1029         }
1030 exit:
1031         return ret;
1032 }
1033 
1034 static inline int __bfs_forwards(struct lock_list *src_entry,
1035                         void *data,
1036                         int (*match)(struct lock_list *entry, void *data),
1037                         struct lock_list **target_entry)
1038 {
1039         return __bfs(src_entry, data, match, target_entry, 1);
1040 
1041 }
1042 
1043 static inline int __bfs_backwards(struct lock_list *src_entry,
1044                         void *data,
1045                         int (*match)(struct lock_list *entry, void *data),
1046                         struct lock_list **target_entry)
1047 {
1048         return __bfs(src_entry, data, match, target_entry, 0);
1049 
1050 }
1051 
1052 /*
1053  * Recursive, forwards-direction lock-dependency checking, used for
1054  * both noncyclic checking and for hardirq-unsafe/softirq-unsafe
1055  * checking.
1056  */
1057 
1058 /*
1059  * Print a dependency chain entry (this is only done when a deadlock
1060  * has been detected):
1061  */
1062 static noinline int
1063 print_circular_bug_entry(struct lock_list *target, int depth)
1064 {
1065         if (debug_locks_silent)
1066                 return 0;
1067         printk("\n-> #%u", depth);
1068         print_lock_name(target->class);
1069         printk(":\n");
1070         print_stack_trace(&target->trace, 6);
1071 
1072         return 0;
1073 }
1074 
1075 static void
1076 print_circular_lock_scenario(struct held_lock *src,
1077                              struct held_lock *tgt,
1078                              struct lock_list *prt)
1079 {
1080         struct lock_class *source = hlock_class(src);
1081         struct lock_class *target = hlock_class(tgt);
1082         struct lock_class *parent = prt->class;
1083 
1084         /*
1085          * A direct locking problem where unsafe_class lock is taken
1086          * directly by safe_class lock, then all we need to show
1087          * is the deadlock scenario, as it is obvious that the
1088          * unsafe lock is taken under the safe lock.
1089          *
1090          * But if there is a chain instead, where the safe lock takes
1091          * an intermediate lock (middle_class) where this lock is
1092          * not the same as the safe lock, then the lock chain is
1093          * used to describe the problem. Otherwise we would need
1094          * to show a different CPU case for each link in the chain
1095          * from the safe_class lock to the unsafe_class lock.
1096          */
1097         if (parent != source) {
1098                 printk("Chain exists of:\n  ");
1099                 __print_lock_name(source);
1100                 printk(" --> ");
1101                 __print_lock_name(parent);
1102                 printk(" --> ");
1103                 __print_lock_name(target);
1104                 printk("\n\n");
1105         }
1106 
1107         printk(" Possible unsafe locking scenario:\n\n");
1108         printk("       CPU0                    CPU1\n");
1109         printk("       ----                    ----\n");
1110         printk("  lock(");
1111         __print_lock_name(target);
1112         printk(");\n");
1113         printk("                               lock(");
1114         __print_lock_name(parent);
1115         printk(");\n");
1116         printk("                               lock(");
1117         __print_lock_name(target);
1118         printk(");\n");
1119         printk("  lock(");
1120         __print_lock_name(source);
1121         printk(");\n");
1122         printk("\n *** DEADLOCK ***\n\n");
1123 }
1124 
1125 /*
1126  * When a circular dependency is detected, print the
1127  * header first:
1128  */
1129 static noinline int
1130 print_circular_bug_header(struct lock_list *entry, unsigned int depth,
1131                         struct held_lock *check_src,
1132                         struct held_lock *check_tgt)
1133 {
1134         struct task_struct *curr = current;
1135 
1136         if (debug_locks_silent)
1137                 return 0;
1138 
1139         printk("\n");
1140         printk("======================================================\n");
1141         printk("[ INFO: possible circular locking dependency detected ]\n");
1142         print_kernel_ident();
1143         printk("-------------------------------------------------------\n");
1144         printk("%s/%d is trying to acquire lock:\n",
1145                 curr->comm, task_pid_nr(curr));
1146         print_lock(check_src);
1147         printk("\nbut task is already holding lock:\n");
1148         print_lock(check_tgt);
1149         printk("\nwhich lock already depends on the new lock.\n\n");
1150         printk("\nthe existing dependency chain (in reverse order) is:\n");
1151 
1152         print_circular_bug_entry(entry, depth);
1153 
1154         return 0;
1155 }
1156 
1157 static inline int class_equal(struct lock_list *entry, void *data)
1158 {
1159         return entry->class == data;
1160 }
1161 
1162 static noinline int print_circular_bug(struct lock_list *this,
1163                                 struct lock_list *target,
1164                                 struct held_lock *check_src,
1165                                 struct held_lock *check_tgt)
1166 {
1167         struct task_struct *curr = current;
1168         struct lock_list *parent;
1169         struct lock_list *first_parent;
1170         int depth;
1171 
1172         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1173                 return 0;
1174 
1175         if (!save_trace(&this->trace))
1176                 return 0;
1177 
1178         depth = get_lock_depth(target);
1179 
1180         print_circular_bug_header(target, depth, check_src, check_tgt);
1181 
1182         parent = get_lock_parent(target);
1183         first_parent = parent;
1184 
1185         while (parent) {
1186                 print_circular_bug_entry(parent, --depth);
1187                 parent = get_lock_parent(parent);
1188         }
1189 
1190         printk("\nother info that might help us debug this:\n\n");
1191         print_circular_lock_scenario(check_src, check_tgt,
1192                                      first_parent);
1193 
1194         lockdep_print_held_locks(curr);
1195 
1196         printk("\nstack backtrace:\n");
1197         dump_stack();
1198 
1199         return 0;
1200 }
1201 
1202 static noinline int print_bfs_bug(int ret)
1203 {
1204         if (!debug_locks_off_graph_unlock())
1205                 return 0;
1206 
1207         /*
1208          * Breadth-first-search failed, graph got corrupted?
1209          */
1210         WARN(1, "lockdep bfs error:%d\n", ret);
1211 
1212         return 0;
1213 }
1214 
1215 static int noop_count(struct lock_list *entry, void *data)
1216 {
1217         (*(unsigned long *)data)++;
1218         return 0;
1219 }
1220 
1221 static unsigned long __lockdep_count_forward_deps(struct lock_list *this)
1222 {
1223         unsigned long  count = 0;
1224         struct lock_list *uninitialized_var(target_entry);
1225 
1226         __bfs_forwards(this, (void *)&count, noop_count, &target_entry);
1227 
1228         return count;
1229 }
1230 unsigned long lockdep_count_forward_deps(struct lock_class *class)
1231 {
1232         unsigned long ret, flags;
1233         struct lock_list this;
1234 
1235         this.parent = NULL;
1236         this.class = class;
1237 
1238         local_irq_save(flags);
1239         arch_spin_lock(&lockdep_lock);
1240         ret = __lockdep_count_forward_deps(&this);
1241         arch_spin_unlock(&lockdep_lock);
1242         local_irq_restore(flags);
1243 
1244         return ret;
1245 }
1246 
1247 static unsigned long __lockdep_count_backward_deps(struct lock_list *this)
1248 {
1249         unsigned long  count = 0;
1250         struct lock_list *uninitialized_var(target_entry);
1251 
1252         __bfs_backwards(this, (void *)&count, noop_count, &target_entry);
1253 
1254         return count;
1255 }
1256 
1257 unsigned long lockdep_count_backward_deps(struct lock_class *class)
1258 {
1259         unsigned long ret, flags;
1260         struct lock_list this;
1261 
1262         this.parent = NULL;
1263         this.class = class;
1264 
1265         local_irq_save(flags);
1266         arch_spin_lock(&lockdep_lock);
1267         ret = __lockdep_count_backward_deps(&this);
1268         arch_spin_unlock(&lockdep_lock);
1269         local_irq_restore(flags);
1270 
1271         return ret;
1272 }
1273 
1274 /*
1275  * Prove that the dependency graph starting at <entry> can not
1276  * lead to <target>. Print an error and return 0 if it does.
1277  */
1278 static noinline int
1279 check_noncircular(struct lock_list *root, struct lock_class *target,
1280                 struct lock_list **target_entry)
1281 {
1282         int result;
1283 
1284         debug_atomic_inc(nr_cyclic_checks);
1285 
1286         result = __bfs_forwards(root, target, class_equal, target_entry);
1287 
1288         return result;
1289 }
1290 
1291 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
1292 /*
1293  * Forwards and backwards subgraph searching, for the purposes of
1294  * proving that two subgraphs can be connected by a new dependency
1295  * without creating any illegal irq-safe -> irq-unsafe lock dependency.
1296  */
1297 
1298 static inline int usage_match(struct lock_list *entry, void *bit)
1299 {
1300         return entry->class->usage_mask & (1 << (enum lock_usage_bit)bit);
1301 }
1302 
1303 
1304 
1305 /*
1306  * Find a node in the forwards-direction dependency sub-graph starting
1307  * at @root->class that matches @bit.
1308  *
1309  * Return 0 if such a node exists in the subgraph, and put that node
1310  * into *@target_entry.
1311  *
1312  * Return 1 otherwise and keep *@target_entry unchanged.
1313  * Return <0 on error.
1314  */
1315 static int
1316 find_usage_forwards(struct lock_list *root, enum lock_usage_bit bit,
1317                         struct lock_list **target_entry)
1318 {
1319         int result;
1320 
1321         debug_atomic_inc(nr_find_usage_forwards_checks);
1322 
1323         result = __bfs_forwards(root, (void *)bit, usage_match, target_entry);
1324 
1325         return result;
1326 }
1327 
1328 /*
1329  * Find a node in the backwards-direction dependency sub-graph starting
1330  * at @root->class that matches @bit.
1331  *
1332  * Return 0 if such a node exists in the subgraph, and put that node
1333  * into *@target_entry.
1334  *
1335  * Return 1 otherwise and keep *@target_entry unchanged.
1336  * Return <0 on error.
1337  */
1338 static int
1339 find_usage_backwards(struct lock_list *root, enum lock_usage_bit bit,
1340                         struct lock_list **target_entry)
1341 {
1342         int result;
1343 
1344         debug_atomic_inc(nr_find_usage_backwards_checks);
1345 
1346         result = __bfs_backwards(root, (void *)bit, usage_match, target_entry);
1347 
1348         return result;
1349 }
1350 
1351 static void print_lock_class_header(struct lock_class *class, int depth)
1352 {
1353         int bit;
1354 
1355         printk("%*s->", depth, "");
1356         print_lock_name(class);
1357         printk(" ops: %lu", class->ops);
1358         printk(" {\n");
1359 
1360         for (bit = 0; bit < LOCK_USAGE_STATES; bit++) {
1361                 if (class->usage_mask & (1 << bit)) {
1362                         int len = depth;
1363 
1364                         len += printk("%*s   %s", depth, "", usage_str[bit]);
1365                         len += printk(" at:\n");
1366                         print_stack_trace(class->usage_traces + bit, len);
1367                 }
1368         }
1369         printk("%*s }\n", depth, "");
1370 
1371         printk("%*s ... key      at: ",depth,"");
1372         print_ip_sym((unsigned long)class->key);
1373 }
1374 
1375 /*
1376  * printk the shortest lock dependencies from @start to @end in reverse order:
1377  */
1378 static void __used
1379 print_shortest_lock_dependencies(struct lock_list *leaf,
1380                                 struct lock_list *root)
1381 {
1382         struct lock_list *entry = leaf;
1383         int depth;
1384 
1385         /*compute depth from generated tree by BFS*/
1386         depth = get_lock_depth(leaf);
1387 
1388         do {
1389                 print_lock_class_header(entry->class, depth);
1390                 printk("%*s ... acquired at:\n", depth, "");
1391                 print_stack_trace(&entry->trace, 2);
1392                 printk("\n");
1393 
1394                 if (depth == 0 && (entry != root)) {
1395                         printk("lockdep:%s bad path found in chain graph\n", __func__);
1396                         break;
1397                 }
1398 
1399                 entry = get_lock_parent(entry);
1400                 depth--;
1401         } while (entry && (depth >= 0));
1402 
1403         return;
1404 }
1405 
1406 static void
1407 print_irq_lock_scenario(struct lock_list *safe_entry,
1408                         struct lock_list *unsafe_entry,
1409                         struct lock_class *prev_class,
1410                         struct lock_class *next_class)
1411 {
1412         struct lock_class *safe_class = safe_entry->class;
1413         struct lock_class *unsafe_class = unsafe_entry->class;
1414         struct lock_class *middle_class = prev_class;
1415 
1416         if (middle_class == safe_class)
1417                 middle_class = next_class;
1418 
1419         /*
1420          * A direct locking problem where unsafe_class lock is taken
1421          * directly by safe_class lock, then all we need to show
1422          * is the deadlock scenario, as it is obvious that the
1423          * unsafe lock is taken under the safe lock.
1424          *
1425          * But if there is a chain instead, where the safe lock takes
1426          * an intermediate lock (middle_class) where this lock is
1427          * not the same as the safe lock, then the lock chain is
1428          * used to describe the problem. Otherwise we would need
1429          * to show a different CPU case for each link in the chain
1430          * from the safe_class lock to the unsafe_class lock.
1431          */
1432         if (middle_class != unsafe_class) {
1433                 printk("Chain exists of:\n  ");
1434                 __print_lock_name(safe_class);
1435                 printk(" --> ");
1436                 __print_lock_name(middle_class);
1437                 printk(" --> ");
1438                 __print_lock_name(unsafe_class);
1439                 printk("\n\n");
1440         }
1441 
1442         printk(" Possible interrupt unsafe locking scenario:\n\n");
1443         printk("       CPU0                    CPU1\n");
1444         printk("       ----                    ----\n");
1445         printk("  lock(");
1446         __print_lock_name(unsafe_class);
1447         printk(");\n");
1448         printk("                               local_irq_disable();\n");
1449         printk("                               lock(");
1450         __print_lock_name(safe_class);
1451         printk(");\n");
1452         printk("                               lock(");
1453         __print_lock_name(middle_class);
1454         printk(");\n");
1455         printk("  <Interrupt>\n");
1456         printk("    lock(");
1457         __print_lock_name(safe_class);
1458         printk(");\n");
1459         printk("\n *** DEADLOCK ***\n\n");
1460 }
1461 
1462 static int
1463 print_bad_irq_dependency(struct task_struct *curr,
1464                          struct lock_list *prev_root,
1465                          struct lock_list *next_root,
1466                          struct lock_list *backwards_entry,
1467                          struct lock_list *forwards_entry,
1468                          struct held_lock *prev,
1469                          struct held_lock *next,
1470                          enum lock_usage_bit bit1,
1471                          enum lock_usage_bit bit2,
1472                          const char *irqclass)
1473 {
1474         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1475                 return 0;
1476 
1477         printk("\n");
1478         printk("======================================================\n");
1479         printk("[ INFO: %s-safe -> %s-unsafe lock order detected ]\n",
1480                 irqclass, irqclass);
1481         print_kernel_ident();
1482         printk("------------------------------------------------------\n");
1483         printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
1484                 curr->comm, task_pid_nr(curr),
1485                 curr->hardirq_context, hardirq_count() >> HARDIRQ_SHIFT,
1486                 curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT,
1487                 curr->hardirqs_enabled,
1488                 curr->softirqs_enabled);
1489         print_lock(next);
1490 
1491         printk("\nand this task is already holding:\n");
1492         print_lock(prev);
1493         printk("which would create a new lock dependency:\n");
1494         print_lock_name(hlock_class(prev));
1495         printk(" ->");
1496         print_lock_name(hlock_class(next));
1497         printk("\n");
1498 
1499         printk("\nbut this new dependency connects a %s-irq-safe lock:\n",
1500                 irqclass);
1501         print_lock_name(backwards_entry->class);
1502         printk("\n... which became %s-irq-safe at:\n", irqclass);
1503 
1504         print_stack_trace(backwards_entry->class->usage_traces + bit1, 1);
1505 
1506         printk("\nto a %s-irq-unsafe lock:\n", irqclass);
1507         print_lock_name(forwards_entry->class);
1508         printk("\n... which became %s-irq-unsafe at:\n", irqclass);
1509         printk("...");
1510 
1511         print_stack_trace(forwards_entry->class->usage_traces + bit2, 1);
1512 
1513         printk("\nother info that might help us debug this:\n\n");
1514         print_irq_lock_scenario(backwards_entry, forwards_entry,
1515                                 hlock_class(prev), hlock_class(next));
1516 
1517         lockdep_print_held_locks(curr);
1518 
1519         printk("\nthe dependencies between %s-irq-safe lock", irqclass);
1520         printk(" and the holding lock:\n");
1521         if (!save_trace(&prev_root->trace))
1522                 return 0;
1523         print_shortest_lock_dependencies(backwards_entry, prev_root);
1524 
1525         printk("\nthe dependencies between the lock to be acquired");
1526         printk(" and %s-irq-unsafe lock:\n", irqclass);
1527         if (!save_trace(&next_root->trace))
1528                 return 0;
1529         print_shortest_lock_dependencies(forwards_entry, next_root);
1530 
1531         printk("\nstack backtrace:\n");
1532         dump_stack();
1533 
1534         return 0;
1535 }
1536 
1537 static int
1538 check_usage(struct task_struct *curr, struct held_lock *prev,
1539             struct held_lock *next, enum lock_usage_bit bit_backwards,
1540             enum lock_usage_bit bit_forwards, const char *irqclass)
1541 {
1542         int ret;
1543         struct lock_list this, that;
1544         struct lock_list *uninitialized_var(target_entry);
1545         struct lock_list *uninitialized_var(target_entry1);
1546 
1547         this.parent = NULL;
1548 
1549         this.class = hlock_class(prev);
1550         ret = find_usage_backwards(&this, bit_backwards, &target_entry);
1551         if (ret < 0)
1552                 return print_bfs_bug(ret);
1553         if (ret == 1)
1554                 return ret;
1555 
1556         that.parent = NULL;
1557         that.class = hlock_class(next);
1558         ret = find_usage_forwards(&that, bit_forwards, &target_entry1);
1559         if (ret < 0)
1560                 return print_bfs_bug(ret);
1561         if (ret == 1)
1562                 return ret;
1563 
1564         return print_bad_irq_dependency(curr, &this, &that,
1565                         target_entry, target_entry1,
1566                         prev, next,
1567                         bit_backwards, bit_forwards, irqclass);
1568 }
1569 
1570 static const char *state_names[] = {
1571 #define LOCKDEP_STATE(__STATE) \
1572         __stringify(__STATE),
1573 #include "lockdep_states.h"
1574 #undef LOCKDEP_STATE
1575 };
1576 
1577 static const char *state_rnames[] = {
1578 #define LOCKDEP_STATE(__STATE) \
1579         __stringify(__STATE)"-READ",
1580 #include "lockdep_states.h"
1581 #undef LOCKDEP_STATE
1582 };
1583 
1584 static inline const char *state_name(enum lock_usage_bit bit)
1585 {
1586         return (bit & 1) ? state_rnames[bit >> 2] : state_names[bit >> 2];
1587 }
1588 
1589 static int exclusive_bit(int new_bit)
1590 {
1591         /*
1592          * USED_IN
1593          * USED_IN_READ
1594          * ENABLED
1595          * ENABLED_READ
1596          *
1597          * bit 0 - write/read
1598          * bit 1 - used_in/enabled
1599          * bit 2+  state
1600          */
1601 
1602         int state = new_bit & ~3;
1603         int dir = new_bit & 2;
1604 
1605         /*
1606          * keep state, bit flip the direction and strip read.
1607          */
1608         return state | (dir ^ 2);
1609 }
1610 
1611 static int check_irq_usage(struct task_struct *curr, struct held_lock *prev,
1612                            struct held_lock *next, enum lock_usage_bit bit)
1613 {
1614         /*
1615          * Prove that the new dependency does not connect a hardirq-safe
1616          * lock with a hardirq-unsafe lock - to achieve this we search
1617          * the backwards-subgraph starting at <prev>, and the
1618          * forwards-subgraph starting at <next>:
1619          */
1620         if (!check_usage(curr, prev, next, bit,
1621                            exclusive_bit(bit), state_name(bit)))
1622                 return 0;
1623 
1624         bit++; /* _READ */
1625 
1626         /*
1627          * Prove that the new dependency does not connect a hardirq-safe-read
1628          * lock with a hardirq-unsafe lock - to achieve this we search
1629          * the backwards-subgraph starting at <prev>, and the
1630          * forwards-subgraph starting at <next>:
1631          */
1632         if (!check_usage(curr, prev, next, bit,
1633                            exclusive_bit(bit), state_name(bit)))
1634                 return 0;
1635 
1636         return 1;
1637 }
1638 
1639 static int
1640 check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
1641                 struct held_lock *next)
1642 {
1643 #define LOCKDEP_STATE(__STATE)                                          \
1644         if (!check_irq_usage(curr, prev, next, LOCK_USED_IN_##__STATE)) \
1645                 return 0;
1646 #include "lockdep_states.h"
1647 #undef LOCKDEP_STATE
1648 
1649         return 1;
1650 }
1651 
1652 static void inc_chains(void)
1653 {
1654         if (current->hardirq_context)
1655                 nr_hardirq_chains++;
1656         else {
1657                 if (current->softirq_context)
1658                         nr_softirq_chains++;
1659                 else
1660                         nr_process_chains++;
1661         }
1662 }
1663 
1664 #else
1665 
1666 static inline int
1667 check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
1668                 struct held_lock *next)
1669 {
1670         return 1;
1671 }
1672 
1673 static inline void inc_chains(void)
1674 {
1675         nr_process_chains++;
1676 }
1677 
1678 #endif
1679 
1680 static void
1681 print_deadlock_scenario(struct held_lock *nxt,
1682                              struct held_lock *prv)
1683 {
1684         struct lock_class *next = hlock_class(nxt);
1685         struct lock_class *prev = hlock_class(prv);
1686 
1687         printk(" Possible unsafe locking scenario:\n\n");
1688         printk("       CPU0\n");
1689         printk("       ----\n");
1690         printk("  lock(");
1691         __print_lock_name(prev);
1692         printk(");\n");
1693         printk("  lock(");
1694         __print_lock_name(next);
1695         printk(");\n");
1696         printk("\n *** DEADLOCK ***\n\n");
1697         printk(" May be due to missing lock nesting notation\n\n");
1698 }
1699 
1700 static int
1701 print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
1702                    struct held_lock *next)
1703 {
1704         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1705                 return 0;
1706 
1707         printk("\n");
1708         printk("=============================================\n");
1709         printk("[ INFO: possible recursive locking detected ]\n");
1710         print_kernel_ident();
1711         printk("---------------------------------------------\n");
1712         printk("%s/%d is trying to acquire lock:\n",
1713                 curr->comm, task_pid_nr(curr));
1714         print_lock(next);
1715         printk("\nbut task is already holding lock:\n");
1716         print_lock(prev);
1717 
1718         printk("\nother info that might help us debug this:\n");
1719         print_deadlock_scenario(next, prev);
1720         lockdep_print_held_locks(curr);
1721 
1722         printk("\nstack backtrace:\n");
1723         dump_stack();
1724 
1725         return 0;
1726 }
1727 
1728 /*
1729  * Check whether we are holding such a class already.
1730  *
1731  * (Note that this has to be done separately, because the graph cannot
1732  * detect such classes of deadlocks.)
1733  *
1734  * Returns: 0 on deadlock detected, 1 on OK, 2 on recursive read
1735  */
1736 static int
1737 check_deadlock(struct task_struct *curr, struct held_lock *next,
1738                struct lockdep_map *next_instance, int read)
1739 {
1740         struct held_lock *prev;
1741         struct held_lock *nest = NULL;
1742         int i;
1743 
1744         for (i = 0; i < curr->lockdep_depth; i++) {
1745                 prev = curr->held_locks + i;
1746 
1747                 if (prev->instance == next->nest_lock)
1748                         nest = prev;
1749 
1750                 if (hlock_class(prev) != hlock_class(next))
1751                         continue;
1752 
1753                 /*
1754                  * Allow read-after-read recursion of the same
1755                  * lock class (i.e. read_lock(lock)+read_lock(lock)):
1756                  */
1757                 if ((read == 2) && prev->read)
1758                         return 2;
1759 
1760                 /*
1761                  * We're holding the nest_lock, which serializes this lock's
1762                  * nesting behaviour.
1763                  */
1764                 if (nest)
1765                         return 2;
1766 
1767                 return print_deadlock_bug(curr, prev, next);
1768         }
1769         return 1;
1770 }
1771 
1772 /*
1773  * There was a chain-cache miss, and we are about to add a new dependency
1774  * to a previous lock. We recursively validate the following rules:
1775  *
1776  *  - would the adding of the <prev> -> <next> dependency create a
1777  *    circular dependency in the graph? [== circular deadlock]
1778  *
1779  *  - does the new prev->next dependency connect any hardirq-safe lock
1780  *    (in the full backwards-subgraph starting at <prev>) with any
1781  *    hardirq-unsafe lock (in the full forwards-subgraph starting at
1782  *    <next>)? [== illegal lock inversion with hardirq contexts]
1783  *
1784  *  - does the new prev->next dependency connect any softirq-safe lock
1785  *    (in the full backwards-subgraph starting at <prev>) with any
1786  *    softirq-unsafe lock (in the full forwards-subgraph starting at
1787  *    <next>)? [== illegal lock inversion with softirq contexts]
1788  *
1789  * any of these scenarios could lead to a deadlock.
1790  *
1791  * Then if all the validations pass, we add the forwards and backwards
1792  * dependency.
1793  */
1794 static int
1795 check_prev_add(struct task_struct *curr, struct held_lock *prev,
1796                struct held_lock *next, int distance, int *stack_saved)
1797 {
1798         struct lock_list *entry;
1799         int ret;
1800         struct lock_list this;
1801         struct lock_list *uninitialized_var(target_entry);
1802         /*
1803          * Static variable, serialized by the graph_lock().
1804          *
1805          * We use this static variable to save the stack trace in case
1806          * we call into this function multiple times due to encountering
1807          * trylocks in the held lock stack.
1808          */
1809         static struct stack_trace trace;
1810 
1811         /*
1812          * Prove that the new <prev> -> <next> dependency would not
1813          * create a circular dependency in the graph. (We do this by
1814          * forward-recursing into the graph starting at <next>, and
1815          * checking whether we can reach <prev>.)
1816          *
1817          * We are using global variables to control the recursion, to
1818          * keep the stackframe size of the recursive functions low:
1819          */
1820         this.class = hlock_class(next);
1821         this.parent = NULL;
1822         ret = check_noncircular(&this, hlock_class(prev), &target_entry);
1823         if (unlikely(!ret))
1824                 return print_circular_bug(&this, target_entry, next, prev);
1825         else if (unlikely(ret < 0))
1826                 return print_bfs_bug(ret);
1827 
1828         if (!check_prev_add_irq(curr, prev, next))
1829                 return 0;
1830 
1831         /*
1832          * For recursive read-locks we do all the dependency checks,
1833          * but we dont store read-triggered dependencies (only
1834          * write-triggered dependencies). This ensures that only the
1835          * write-side dependencies matter, and that if for example a
1836          * write-lock never takes any other locks, then the reads are
1837          * equivalent to a NOP.
1838          */
1839         if (next->read == 2 || prev->read == 2)
1840                 return 1;
1841         /*
1842          * Is the <prev> -> <next> dependency already present?
1843          *
1844          * (this may occur even though this is a new chain: consider
1845          *  e.g. the L1 -> L2 -> L3 -> L4 and the L5 -> L1 -> L2 -> L3
1846          *  chains - the second one will be new, but L1 already has
1847          *  L2 added to its dependency list, due to the first chain.)
1848          */
1849         list_for_each_entry(entry, &hlock_class(prev)->locks_after, entry) {
1850                 if (entry->class == hlock_class(next)) {
1851                         if (distance == 1)
1852                                 entry->distance = 1;
1853                         return 2;
1854                 }
1855         }
1856 
1857         if (!*stack_saved) {
1858                 if (!save_trace(&trace))
1859                         return 0;
1860                 *stack_saved = 1;
1861         }
1862 
1863         /*
1864          * Ok, all validations passed, add the new lock
1865          * to the previous lock's dependency list:
1866          */
1867         ret = add_lock_to_list(hlock_class(prev), hlock_class(next),
1868                                &hlock_class(prev)->locks_after,
1869                                next->acquire_ip, distance, &trace);
1870 
1871         if (!ret)
1872                 return 0;
1873 
1874         ret = add_lock_to_list(hlock_class(next), hlock_class(prev),
1875                                &hlock_class(next)->locks_before,
1876                                next->acquire_ip, distance, &trace);
1877         if (!ret)
1878                 return 0;
1879 
1880         /*
1881          * Debugging printouts:
1882          */
1883         if (verbose(hlock_class(prev)) || verbose(hlock_class(next))) {
1884                 /* We drop graph lock, so another thread can overwrite trace. */
1885                 *stack_saved = 0;
1886                 graph_unlock();
1887                 printk("\n new dependency: ");
1888                 print_lock_name(hlock_class(prev));
1889                 printk(" => ");
1890                 print_lock_name(hlock_class(next));
1891                 printk("\n");
1892                 dump_stack();
1893                 return graph_lock();
1894         }
1895         return 1;
1896 }
1897 
1898 /*
1899  * Add the dependency to all directly-previous locks that are 'relevant'.
1900  * The ones that are relevant are (in increasing distance from curr):
1901  * all consecutive trylock entries and the final non-trylock entry - or
1902  * the end of this context's lock-chain - whichever comes first.
1903  */
1904 static int
1905 check_prevs_add(struct task_struct *curr, struct held_lock *next)
1906 {
1907         int depth = curr->lockdep_depth;
1908         int stack_saved = 0;
1909         struct held_lock *hlock;
1910 
1911         /*
1912          * Debugging checks.
1913          *
1914          * Depth must not be zero for a non-head lock:
1915          */
1916         if (!depth)
1917                 goto out_bug;
1918         /*
1919          * At least two relevant locks must exist for this
1920          * to be a head:
1921          */
1922         if (curr->held_locks[depth].irq_context !=
1923                         curr->held_locks[depth-1].irq_context)
1924                 goto out_bug;
1925 
1926         for (;;) {
1927                 int distance = curr->lockdep_depth - depth + 1;
1928                 hlock = curr->held_locks + depth - 1;
1929                 /*
1930                  * Only non-recursive-read entries get new dependencies
1931                  * added:
1932                  */
1933                 if (hlock->read != 2 && hlock->check) {
1934                         if (!check_prev_add(curr, hlock, next,
1935                                                 distance, &stack_saved))
1936                                 return 0;
1937                         /*
1938                          * Stop after the first non-trylock entry,
1939                          * as non-trylock entries have added their
1940                          * own direct dependencies already, so this
1941                          * lock is connected to them indirectly:
1942                          */
1943                         if (!hlock->trylock)
1944                                 break;
1945                 }
1946                 depth--;
1947                 /*
1948                  * End of lock-stack?
1949                  */
1950                 if (!depth)
1951                         break;
1952                 /*
1953                  * Stop the search if we cross into another context:
1954                  */
1955                 if (curr->held_locks[depth].irq_context !=
1956                                 curr->held_locks[depth-1].irq_context)
1957                         break;
1958         }
1959         return 1;
1960 out_bug:
1961         if (!debug_locks_off_graph_unlock())
1962                 return 0;
1963 
1964         /*
1965          * Clearly we all shouldn't be here, but since we made it we
1966          * can reliable say we messed up our state. See the above two
1967          * gotos for reasons why we could possibly end up here.
1968          */
1969         WARN_ON(1);
1970 
1971         return 0;
1972 }
1973 
1974 unsigned long nr_lock_chains;
1975 struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
1976 int nr_chain_hlocks;
1977 static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
1978 
1979 struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
1980 {
1981         return lock_classes + chain_hlocks[chain->base + i];
1982 }
1983 
1984 /*
1985  * Returns the index of the first held_lock of the current chain
1986  */
1987 static inline int get_first_held_lock(struct task_struct *curr,
1988                                         struct held_lock *hlock)
1989 {
1990         int i;
1991         struct held_lock *hlock_curr;
1992 
1993         for (i = curr->lockdep_depth - 1; i >= 0; i--) {
1994                 hlock_curr = curr->held_locks + i;
1995                 if (hlock_curr->irq_context != hlock->irq_context)
1996                         break;
1997 
1998         }
1999 
2000         return ++i;
2001 }
2002 
2003 #ifdef CONFIG_DEBUG_LOCKDEP
2004 /*
2005  * Returns the next chain_key iteration
2006  */
2007 static u64 print_chain_key_iteration(int class_idx, u64 chain_key)
2008 {
2009         u64 new_chain_key = iterate_chain_key(chain_key, class_idx);
2010 
2011         printk(" class_idx:%d -> chain_key:%016Lx",
2012                 class_idx,
2013                 (unsigned long long)new_chain_key);
2014         return new_chain_key;
2015 }
2016 
2017 static void
2018 print_chain_keys_held_locks(struct task_struct *curr, struct held_lock *hlock_next)
2019 {
2020         struct held_lock *hlock;
2021         u64 chain_key = 0;
2022         int depth = curr->lockdep_depth;
2023         int i;
2024 
2025         printk("depth: %u\n", depth + 1);
2026         for (i = get_first_held_lock(curr, hlock_next); i < depth; i++) {
2027                 hlock = curr->held_locks + i;
2028                 chain_key = print_chain_key_iteration(hlock->class_idx, chain_key);
2029 
2030                 print_lock(hlock);
2031         }
2032 
2033         print_chain_key_iteration(hlock_next->class_idx, chain_key);
2034         print_lock(hlock_next);
2035 }
2036 
2037 static void print_chain_keys_chain(struct lock_chain *chain)
2038 {
2039         int i;
2040         u64 chain_key = 0;
2041         int class_id;
2042 
2043         printk("depth: %u\n", chain->depth);
2044         for (i = 0; i < chain->depth; i++) {
2045                 class_id = chain_hlocks[chain->base + i];
2046                 chain_key = print_chain_key_iteration(class_id + 1, chain_key);
2047 
2048                 print_lock_name(lock_classes + class_id);
2049                 printk("\n");
2050         }
2051 }
2052 
2053 static void print_collision(struct task_struct *curr,
2054                         struct held_lock *hlock_next,
2055                         struct lock_chain *chain)
2056 {
2057         printk("\n");
2058         printk("======================\n");
2059         printk("[chain_key collision ]\n");
2060         print_kernel_ident();
2061         printk("----------------------\n");
2062         printk("%s/%d: ", current->comm, task_pid_nr(current));
2063         printk("Hash chain already cached but the contents don't match!\n");
2064 
2065         printk("Held locks:");
2066         print_chain_keys_held_locks(curr, hlock_next);
2067 
2068         printk("Locks in cached chain:");
2069         print_chain_keys_chain(chain);
2070 
2071         printk("\nstack backtrace:\n");
2072         dump_stack();
2073 }
2074 #endif
2075 
2076 /*
2077  * Checks whether the chain and the current held locks are consistent
2078  * in depth and also in content. If they are not it most likely means
2079  * that there was a collision during the calculation of the chain_key.
2080  * Returns: 0 not passed, 1 passed
2081  */
2082 static int check_no_collision(struct task_struct *curr,
2083                         struct held_lock *hlock,
2084                         struct lock_chain *chain)
2085 {
2086 #ifdef CONFIG_DEBUG_LOCKDEP
2087         int i, j, id;
2088 
2089         i = get_first_held_lock(curr, hlock);
2090 
2091         if (DEBUG_LOCKS_WARN_ON(chain->depth != curr->lockdep_depth - (i - 1))) {
2092                 print_collision(curr, hlock, chain);
2093                 return 0;
2094         }
2095 
2096         for (j = 0; j < chain->depth - 1; j++, i++) {
2097                 id = curr->held_locks[i].class_idx - 1;
2098 
2099                 if (DEBUG_LOCKS_WARN_ON(chain_hlocks[chain->base + j] != id)) {
2100                         print_collision(curr, hlock, chain);
2101                         return 0;
2102                 }
2103         }
2104 #endif
2105         return 1;
2106 }
2107 
2108 /*
2109  * Look up a dependency chain. If the key is not present yet then
2110  * add it and return 1 - in this case the new dependency chain is
2111  * validated. If the key is already hashed, return 0.
2112  * (On return with 1 graph_lock is held.)
2113  */
2114 static inline int lookup_chain_cache(struct task_struct *curr,
2115                                      struct held_lock *hlock,
2116                                      u64 chain_key)
2117 {
2118         struct lock_class *class = hlock_class(hlock);
2119         struct hlist_head *hash_head = chainhashentry(chain_key);
2120         struct lock_chain *chain;
2121         int i, j;
2122 
2123         /*
2124          * We might need to take the graph lock, ensure we've got IRQs
2125          * disabled to make this an IRQ-safe lock.. for recursion reasons
2126          * lockdep won't complain about its own locking errors.
2127          */
2128         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2129                 return 0;
2130         /*
2131          * We can walk it lock-free, because entries only get added
2132          * to the hash:
2133          */
2134         hlist_for_each_entry_rcu(chain, hash_head, entry) {
2135                 if (chain->chain_key == chain_key) {
2136 cache_hit:
2137                         debug_atomic_inc(chain_lookup_hits);
2138                         if (!check_no_collision(curr, hlock, chain))
2139                                 return 0;
2140 
2141                         if (very_verbose(class))
2142                                 printk("\nhash chain already cached, key: "
2143                                         "%016Lx tail class: [%p] %s\n",
2144                                         (unsigned long long)chain_key,
2145                                         class->key, class->name);
2146                         return 0;
2147                 }
2148         }
2149         if (very_verbose(class))
2150                 printk("\nnew hash chain, key: %016Lx tail class: [%p] %s\n",
2151                         (unsigned long long)chain_key, class->key, class->name);
2152         /*
2153          * Allocate a new chain entry from the static array, and add
2154          * it to the hash:
2155          */
2156         if (!graph_lock())
2157                 return 0;
2158         /*
2159          * We have to walk the chain again locked - to avoid duplicates:
2160          */
2161         hlist_for_each_entry(chain, hash_head, entry) {
2162                 if (chain->chain_key == chain_key) {
2163                         graph_unlock();
2164                         goto cache_hit;
2165                 }
2166         }
2167         if (unlikely(nr_lock_chains >= MAX_LOCKDEP_CHAINS)) {
2168                 if (!debug_locks_off_graph_unlock())
2169                         return 0;
2170 
2171                 print_lockdep_off("BUG: MAX_LOCKDEP_CHAINS too low!");
2172                 dump_stack();
2173                 return 0;
2174         }
2175         chain = lock_chains + nr_lock_chains++;
2176         chain->chain_key = chain_key;
2177         chain->irq_context = hlock->irq_context;
2178         i = get_first_held_lock(curr, hlock);
2179         chain->depth = curr->lockdep_depth + 1 - i;
2180 
2181         BUILD_BUG_ON((1UL << 24) <= ARRAY_SIZE(chain_hlocks));
2182         BUILD_BUG_ON((1UL << 6)  <= ARRAY_SIZE(curr->held_locks));
2183         BUILD_BUG_ON((1UL << 8*sizeof(chain_hlocks[0])) <= ARRAY_SIZE(lock_classes));
2184 
2185         if (likely(nr_chain_hlocks + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) {
2186                 chain->base = nr_chain_hlocks;
2187                 for (j = 0; j < chain->depth - 1; j++, i++) {
2188                         int lock_id = curr->held_locks[i].class_idx - 1;
2189                         chain_hlocks[chain->base + j] = lock_id;
2190                 }
2191                 chain_hlocks[chain->base + j] = class - lock_classes;
2192         }
2193 
2194         if (nr_chain_hlocks < MAX_LOCKDEP_CHAIN_HLOCKS)
2195                 nr_chain_hlocks += chain->depth;
2196 
2197 #ifdef CONFIG_DEBUG_LOCKDEP
2198         /*
2199          * Important for check_no_collision().
2200          */
2201         if (unlikely(nr_chain_hlocks > MAX_LOCKDEP_CHAIN_HLOCKS)) {
2202                 if (debug_locks_off_graph_unlock())
2203                         return 0;
2204 
2205                 print_lockdep_off("BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!");
2206                 dump_stack();
2207                 return 0;
2208         }
2209 #endif
2210 
2211         hlist_add_head_rcu(&chain->entry, hash_head);
2212         debug_atomic_inc(chain_lookup_misses);
2213         inc_chains();
2214 
2215         return 1;
2216 }
2217 
2218 static int validate_chain(struct task_struct *curr, struct lockdep_map *lock,
2219                 struct held_lock *hlock, int chain_head, u64 chain_key)
2220 {
2221         /*
2222          * Trylock needs to maintain the stack of held locks, but it
2223          * does not add new dependencies, because trylock can be done
2224          * in any order.
2225          *
2226          * We look up the chain_key and do the O(N^2) check and update of
2227          * the dependencies only if this is a new dependency chain.
2228          * (If lookup_chain_cache() returns with 1 it acquires
2229          * graph_lock for us)
2230          */
2231         if (!hlock->trylock && hlock->check &&
2232             lookup_chain_cache(curr, hlock, chain_key)) {
2233                 /*
2234                  * Check whether last held lock:
2235                  *
2236                  * - is irq-safe, if this lock is irq-unsafe
2237                  * - is softirq-safe, if this lock is hardirq-unsafe
2238                  *
2239                  * And check whether the new lock's dependency graph
2240                  * could lead back to the previous lock.
2241                  *
2242                  * any of these scenarios could lead to a deadlock. If
2243                  * All validations
2244                  */
2245                 int ret = check_deadlock(curr, hlock, lock, hlock->read);
2246 
2247                 if (!ret)
2248                         return 0;
2249                 /*
2250                  * Mark recursive read, as we jump over it when
2251                  * building dependencies (just like we jump over
2252                  * trylock entries):
2253                  */
2254                 if (ret == 2)
2255                         hlock->read = 2;
2256                 /*
2257                  * Add dependency only if this lock is not the head
2258                  * of the chain, and if it's not a secondary read-lock:
2259                  */
2260                 if (!chain_head && ret != 2)
2261                         if (!check_prevs_add(curr, hlock))
2262                                 return 0;
2263                 graph_unlock();
2264         } else
2265                 /* after lookup_chain_cache(): */
2266                 if (unlikely(!debug_locks))
2267                         return 0;
2268 
2269         return 1;
2270 }
2271 #else
2272 static inline int validate_chain(struct task_struct *curr,
2273                 struct lockdep_map *lock, struct held_lock *hlock,
2274                 int chain_head, u64 chain_key)
2275 {
2276         return 1;
2277 }
2278 #endif
2279 
2280 /*
2281  * We are building curr_chain_key incrementally, so double-check
2282  * it from scratch, to make sure that it's done correctly:
2283  */
2284 static void check_chain_key(struct task_struct *curr)
2285 {
2286 #ifdef CONFIG_DEBUG_LOCKDEP
2287         struct held_lock *hlock, *prev_hlock = NULL;
2288         unsigned int i;
2289         u64 chain_key = 0;
2290 
2291         for (i = 0; i < curr->lockdep_depth; i++) {
2292                 hlock = curr->held_locks + i;
2293                 if (chain_key != hlock->prev_chain_key) {
2294                         debug_locks_off();
2295                         /*
2296                          * We got mighty confused, our chain keys don't match
2297                          * with what we expect, someone trample on our task state?
2298                          */
2299                         WARN(1, "hm#1, depth: %u [%u], %016Lx != %016Lx\n",
2300                                 curr->lockdep_depth, i,
2301                                 (unsigned long long)chain_key,
2302                                 (unsigned long long)hlock->prev_chain_key);
2303                         return;
2304                 }
2305                 /*
2306                  * Whoops ran out of static storage again?
2307                  */
2308                 if (DEBUG_LOCKS_WARN_ON(hlock->class_idx > MAX_LOCKDEP_KEYS))
2309                         return;
2310 
2311                 if (prev_hlock && (prev_hlock->irq_context !=
2312                                                         hlock->irq_context))
2313                         chain_key = 0;
2314                 chain_key = iterate_chain_key(chain_key, hlock->class_idx);
2315                 prev_hlock = hlock;
2316         }
2317         if (chain_key != curr->curr_chain_key) {
2318                 debug_locks_off();
2319                 /*
2320                  * More smoking hash instead of calculating it, damn see these
2321                  * numbers float.. I bet that a pink elephant stepped on my memory.
2322                  */
2323                 WARN(1, "hm#2, depth: %u [%u], %016Lx != %016Lx\n",
2324                         curr->lockdep_depth, i,
2325                         (unsigned long long)chain_key,
2326                         (unsigned long long)curr->curr_chain_key);
2327         }
2328 #endif
2329 }
2330 
2331 static void
2332 print_usage_bug_scenario(struct held_lock *lock)
2333 {
2334         struct lock_class *class = hlock_class(lock);
2335 
2336         printk(" Possible unsafe locking scenario:\n\n");
2337         printk("       CPU0\n");
2338         printk("       ----\n");
2339         printk("  lock(");
2340         __print_lock_name(class);
2341         printk(");\n");
2342         printk("  <Interrupt>\n");
2343         printk("    lock(");
2344         __print_lock_name(class);
2345         printk(");\n");
2346         printk("\n *** DEADLOCK ***\n\n");
2347 }
2348 
2349 static int
2350 print_usage_bug(struct task_struct *curr, struct held_lock *this,
2351                 enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
2352 {
2353         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2354                 return 0;
2355 
2356         printk("\n");
2357         printk("=================================\n");
2358         printk("[ INFO: inconsistent lock state ]\n");
2359         print_kernel_ident();
2360         printk("---------------------------------\n");
2361 
2362         printk("inconsistent {%s} -> {%s} usage.\n",
2363                 usage_str[prev_bit], usage_str[new_bit]);
2364 
2365         printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] takes:\n",
2366                 curr->comm, task_pid_nr(curr),
2367                 trace_hardirq_context(curr), hardirq_count() >> HARDIRQ_SHIFT,
2368                 trace_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT,
2369                 trace_hardirqs_enabled(curr),
2370                 trace_softirqs_enabled(curr));
2371         print_lock(this);
2372 
2373         printk("{%s} state was registered at:\n", usage_str[prev_bit]);
2374         print_stack_trace(hlock_class(this)->usage_traces + prev_bit, 1);
2375 
2376         print_irqtrace_events(curr);
2377         printk("\nother info that might help us debug this:\n");
2378         print_usage_bug_scenario(this);
2379 
2380         lockdep_print_held_locks(curr);
2381 
2382         printk("\nstack backtrace:\n");
2383         dump_stack();
2384 
2385         return 0;
2386 }
2387 
2388 /*
2389  * Print out an error if an invalid bit is set:
2390  */
2391 static inline int
2392 valid_state(struct task_struct *curr, struct held_lock *this,
2393             enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit)
2394 {
2395         if (unlikely(hlock_class(this)->usage_mask & (1 << bad_bit)))
2396                 return print_usage_bug(curr, this, bad_bit, new_bit);
2397         return 1;
2398 }
2399 
2400 static int mark_lock(struct task_struct *curr, struct held_lock *this,
2401                      enum lock_usage_bit new_bit);
2402 
2403 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
2404 
2405 /*
2406  * print irq inversion bug:
2407  */
2408 static int
2409 print_irq_inversion_bug(struct task_struct *curr,
2410                         struct lock_list *root, struct lock_list *other,
2411                         struct held_lock *this, int forwards,
2412                         const char *irqclass)
2413 {
2414         struct lock_list *entry = other;
2415         struct lock_list *middle = NULL;
2416         int depth;
2417 
2418         if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2419                 return 0;
2420 
2421         printk("\n");
2422         printk("=========================================================\n");
2423         printk("[ INFO: possible irq lock inversion dependency detected ]\n");
2424         print_kernel_ident();
2425         printk("---------------------------------------------------------\n");
2426         printk("%s/%d just changed the state of lock:\n",
2427                 curr->comm, task_pid_nr(curr));
2428         print_lock(this);
2429         if (forwards)
2430                 printk("but this lock took another, %s-unsafe lock in the past:\n", irqclass);
2431         else
2432                 printk("but this lock was taken by another, %s-safe lock in the past:\n", irqclass);
2433         print_lock_name(other->class);
2434         printk("\n\nand interrupts could create inverse lock ordering between them.\n\n");
2435 
2436         printk("\nother info that might help us debug this:\n");
2437 
2438         /* Find a middle lock (if one exists) */
2439         depth = get_lock_depth(other);
2440         do {
2441                 if (depth == 0 && (entry != root)) {
2442                         printk("lockdep:%s bad path found in chain graph\n", __func__);
2443                         break;
2444                 }
2445                 middle = entry;
2446                 entry = get_lock_parent(entry);
2447                 depth--;
2448         } while (entry && entry != root && (depth >= 0));
2449         if (forwards)
2450                 print_irq_lock_scenario(root, other,
2451                         middle ? middle->class : root->class, other->class);
2452         else
2453                 print_irq_lock_scenario(other, root,
2454                         middle ? middle->class : other->class, root->class);
2455 
2456         lockdep_print_held_locks(curr);
2457 
2458         printk("\nthe shortest dependencies between 2nd lock and 1st lock:\n");
2459         if (!save_trace(&root->trace))
2460                 return 0;
2461         print_shortest_lock_dependencies(other, root);
2462 
2463         printk("\nstack backtrace:\n");
2464         dump_stack();
2465 
2466         return 0;
2467 }
2468 
2469 /*
2470  * Prove that in the forwards-direction subgraph starting at <this>
2471  * there is no lock matching <mask>:
2472  */
2473 static int
2474 check_usage_forwards(struct task_struct *curr, struct held_lock *this,
2475                      enum lock_usage_bit bit, const char *irqclass)
2476 {
2477         int ret;
2478         struct lock_list root;
2479         struct lock_list *uninitialized_var(target_entry);
2480 
2481         root.parent = NULL;
2482         root.class = hlock_class(this);
2483         ret = find_usage_forwards(&root, bit, &target_entry);
2484         if (ret < 0)
2485                 return print_bfs_bug(ret);
2486         if (ret == 1)
2487                 return ret;
2488 
2489         return print_irq_inversion_bug(curr, &root, target_entry,
2490                                         this, 1, irqclass);
2491 }
2492 
2493 /*
2494  * Prove that in the backwards-direction subgraph starting at <this>
2495  * there is no lock matching <mask>:
2496  */
2497 static int
2498 check_usage_backwards(struct task_struct *curr, struct held_lock *this,
2499                       enum lock_usage_bit bit, const char *irqclass)
2500 {
2501         int ret;
2502         struct lock_list root;
2503         struct lock_list *uninitialized_var(target_entry);
2504 
2505         root.parent = NULL;
2506         root.class = hlock_class(this);
2507         ret = find_usage_backwards(&root, bit, &target_entry);
2508         if (ret < 0)
2509                 return print_bfs_bug(ret);
2510         if (ret == 1)
2511                 return ret;
2512 
2513         return print_irq_inversion_bug(curr, &root, target_entry,
2514                                         this, 0, irqclass);
2515 }
2516 
2517 void print_irqtrace_events(struct task_struct *curr)
2518 {
2519         printk("irq event stamp: %u\n", curr->irq_events);
2520         printk("hardirqs last  enabled at (%u): ", curr->hardirq_enable_event);
2521         print_ip_sym(curr->hardirq_enable_ip);
2522         printk("hardirqs last disabled at (%u): ", curr->hardirq_disable_event);
2523         print_ip_sym(curr->hardirq_disable_ip);
2524         printk("softirqs last  enabled at (%u): ", curr->softirq_enable_event);
2525         print_ip_sym(curr->softirq_enable_ip);
2526         printk("softirqs last disabled at (%u): ", curr->softirq_disable_event);
2527         print_ip_sym(curr->softirq_disable_ip);
2528 }
2529 
2530 static int HARDIRQ_verbose(struct lock_class *class)
2531 {
2532 #if HARDIRQ_VERBOSE
2533         return class_filter(class);
2534 #endif
2535         return 0;
2536 }
2537 
2538 static int SOFTIRQ_verbose(struct lock_class *class)
2539 {
2540 #if SOFTIRQ_VERBOSE
2541         return class_filter(class);
2542 #endif
2543         return 0;
2544 }
2545 
2546 static int RECLAIM_FS_verbose(struct lock_class *class)
2547 {
2548 #if RECLAIM_VERBOSE
2549         return class_filter(class);
2550 #endif
2551         return 0;
2552 }
2553 
2554 #define STRICT_READ_CHECKS      1
2555 
2556 static int (*state_verbose_f[])(struct lock_class *class) = {
2557 #define LOCKDEP_STATE(__STATE) \
2558         __STATE##_verbose,
2559 #include "lockdep_states.h"
2560 #undef LOCKDEP_STATE
2561 };
2562 
2563 static inline int state_verbose(enum lock_usage_bit bit,
2564                                 struct lock_class *class)
2565 {
2566         return state_verbose_f[bit >> 2](class);
2567 }
2568 
2569 typedef int (*check_usage_f)(struct task_struct *, struct held_lock *,
2570                              enum lock_usage_bit bit, const char *name);
2571 
2572 static int
2573 mark_lock_irq(struct task_struct *curr, struct held_lock *this,
2574                 enum lock_usage_bit new_bit)
2575 {
2576         int excl_bit = exclusive_bit(new_bit);
2577         int read = new_bit & 1;
2578         int dir = new_bit & 2;
2579 
2580         /*
2581          * mark USED_IN has to look forwards -- to ensure no dependency
2582          * has ENABLED state, which would allow recursion deadlocks.
2583          *
2584          * mark ENABLED has to look backwards -- to ensure no dependee
2585          * has USED_IN state, which, again, would allow  recursion deadlocks.
2586          */
2587         check_usage_f usage = dir ?
2588                 check_usage_backwards : check_usage_forwards;
2589 
2590         /*
2591          * Validate that this particular lock does not have conflicting
2592          * usage states.
2593          */
2594         if (!valid_state(curr, this, new_bit, excl_bit))
2595                 return 0;
2596 
2597         /*
2598          * Validate that the lock dependencies don't have conflicting usage
2599          * states.
2600          */
2601         if ((!read || !dir || STRICT_READ_CHECKS) &&
2602                         !usage(curr, this, excl_bit, state_name(new_bit & ~1)))
2603                 return 0;
2604 
2605         /*
2606          * Check for read in write conflicts
2607          */
2608         if (!read) {
2609                 if (!valid_state(curr, this, new_bit, excl_bit + 1))
2610                         return 0;
2611 
2612                 if (STRICT_READ_CHECKS &&
2613                         !usage(curr, this, excl_bit + 1,
2614                                 state_name(new_bit + 1)))
2615                         return 0;
2616         }
2617 
2618         if (state_verbose(new_bit, hlock_class(this)))
2619                 return 2;
2620 
2621         return 1;
2622 }
2623 
2624 enum mark_type {
2625 #define LOCKDEP_STATE(__STATE)  __STATE,
2626 #include "lockdep_states.h"
2627 #undef LOCKDEP_STATE
2628 };
2629 
2630 /*
2631  * Mark all held locks with a usage bit:
2632  */
2633 static int
2634 mark_held_locks(struct task_struct *curr, enum mark_type mark)
2635 {
2636         enum lock_usage_bit usage_bit;
2637         struct held_lock *hlock;
2638         int i;
2639 
2640         for (i = 0; i < curr->lockdep_depth; i++) {
2641                 hlock = curr->held_locks + i;
2642 
2643                 usage_bit = 2 + (mark << 2); /* ENABLED */
2644                 if (hlock->read)
2645                         usage_bit += 1; /* READ */
2646 
2647                 BUG_ON(usage_bit >= LOCK_USAGE_STATES);
2648 
2649                 if (!hlock->check)
2650                         continue;
2651 
2652                 if (!mark_lock(curr, hlock, usage_bit))
2653                         return 0;
2654         }
2655 
2656         return 1;
2657 }
2658 
2659 /*
2660  * Hardirqs will be enabled:
2661  */
2662 static void __trace_hardirqs_on_caller(unsigned long ip)
2663 {
2664         struct task_struct *curr = current;
2665 
2666         /* we'll do an OFF -> ON transition: */
2667         curr->hardirqs_enabled = 1;
2668 
2669         /*
2670          * We are going to turn hardirqs on, so set the
2671          * usage bit for all held locks:
2672          */
2673         if (!mark_held_locks(curr, HARDIRQ))
2674                 return;
2675         /*
2676          * If we have softirqs enabled, then set the usage
2677          * bit for all held locks. (disabled hardirqs prevented
2678          * this bit from being set before)
2679          */
2680         if (curr->softirqs_enabled)
2681                 if (!mark_held_locks(curr, SOFTIRQ))
2682                         return;
2683 
2684         curr->hardirq_enable_ip = ip;
2685         curr->hardirq_enable_event = ++curr->irq_events;
2686         debug_atomic_inc(hardirqs_on_events);
2687 }
2688 
2689 __visible void trace_hardirqs_on_caller(unsigned long ip)
2690 {
2691         time_hardirqs_on(CALLER_ADDR0, ip);
2692 
2693         if (unlikely(!debug_locks || current->lockdep_recursion))
2694                 return;
2695 
2696         if (unlikely(current->hardirqs_enabled)) {
2697                 /*
2698                  * Neither irq nor preemption are disabled here
2699                  * so this is racy by nature but losing one hit
2700                  * in a stat is not a big deal.
2701                  */
2702                 __debug_atomic_inc(redundant_hardirqs_on);
2703                 return;
2704         }
2705 
2706         /*
2707          * We're enabling irqs and according to our state above irqs weren't
2708          * already enabled, yet we find the hardware thinks they are in fact
2709          * enabled.. someone messed up their IRQ state tracing.
2710          */
2711         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2712                 return;
2713 
2714         /*
2715          * See the fine text that goes along with this variable definition.
2716          */
2717         if (DEBUG_LOCKS_WARN_ON(unlikely(early_boot_irqs_disabled)))
2718                 return;
2719 
2720         /*
2721          * Can't allow enabling interrupts while in an interrupt handler,
2722          * that's general bad form and such. Recursion, limited stack etc..
2723          */
2724         if (DEBUG_LOCKS_WARN_ON(current->hardirq_context))
2725                 return;
2726 
2727         current->lockdep_recursion = 1;
2728         __trace_hardirqs_on_caller(ip);
2729         current->lockdep_recursion = 0;
2730 }
2731 EXPORT_SYMBOL(trace_hardirqs_on_caller);
2732 
2733 void trace_hardirqs_on(void)
2734 {
2735         trace_hardirqs_on_caller(CALLER_ADDR0);
2736 }
2737 EXPORT_SYMBOL(trace_hardirqs_on);
2738 
2739 /*
2740  * Hardirqs were disabled:
2741  */
2742 __visible void trace_hardirqs_off_caller(unsigned long ip)
2743 {
2744         struct task_struct *curr = current;
2745 
2746         time_hardirqs_off(CALLER_ADDR0, ip);
2747 
2748         if (unlikely(!debug_locks || current->lockdep_recursion))
2749                 return;
2750 
2751         /*
2752          * So we're supposed to get called after you mask local IRQs, but for
2753          * some reason the hardware doesn't quite think you did a proper job.
2754          */
2755         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2756                 return;
2757 
2758         if (curr->hardirqs_enabled) {
2759                 /*
2760                  * We have done an ON -> OFF transition:
2761                  */
2762                 curr->hardirqs_enabled = 0;
2763                 curr->hardirq_disable_ip = ip;
2764                 curr->hardirq_disable_event = ++curr->irq_events;
2765                 debug_atomic_inc(hardirqs_off_events);
2766         } else
2767                 debug_atomic_inc(redundant_hardirqs_off);
2768 }
2769 EXPORT_SYMBOL(trace_hardirqs_off_caller);
2770 
2771 void trace_hardirqs_off(void)
2772 {
2773         trace_hardirqs_off_caller(CALLER_ADDR0);
2774 }
2775 EXPORT_SYMBOL(trace_hardirqs_off);
2776 
2777 /*
2778  * Softirqs will be enabled:
2779  */
2780 void trace_softirqs_on(unsigned long ip)
2781 {
2782         struct task_struct *curr = current;
2783 
2784         if (unlikely(!debug_locks || current->lockdep_recursion))
2785                 return;
2786 
2787         /*
2788          * We fancy IRQs being disabled here, see softirq.c, avoids
2789          * funny state and nesting things.
2790          */
2791         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2792                 return;
2793 
2794         if (curr->softirqs_enabled) {
2795                 debug_atomic_inc(redundant_softirqs_on);
2796                 return;
2797         }
2798 
2799         current->lockdep_recursion = 1;
2800         /*
2801          * We'll do an OFF -> ON transition:
2802          */
2803         curr->softirqs_enabled = 1;
2804         curr->softirq_enable_ip = ip;
2805         curr->softirq_enable_event = ++curr->irq_events;
2806         debug_atomic_inc(softirqs_on_events);
2807         /*
2808          * We are going to turn softirqs on, so set the
2809          * usage bit for all held locks, if hardirqs are
2810          * enabled too:
2811          */
2812         if (curr->hardirqs_enabled)
2813                 mark_held_locks(curr, SOFTIRQ);
2814         current->lockdep_recursion = 0;
2815 }
2816 
2817 /*
2818  * Softirqs were disabled:
2819  */
2820 void trace_softirqs_off(unsigned long ip)
2821 {
2822         struct task_struct *curr = current;
2823 
2824         if (unlikely(!debug_locks || current->lockdep_recursion))
2825                 return;
2826 
2827         /*
2828          * We fancy IRQs being disabled here, see softirq.c
2829          */
2830         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2831                 return;
2832 
2833         if (curr->softirqs_enabled) {
2834                 /*
2835                  * We have done an ON -> OFF transition:
2836                  */
2837                 curr->softirqs_enabled = 0;
2838                 curr->softirq_disable_ip = ip;
2839                 curr->softirq_disable_event = ++curr->irq_events;
2840                 debug_atomic_inc(softirqs_off_events);
2841                 /*
2842                  * Whoops, we wanted softirqs off, so why aren't they?
2843                  */
2844                 DEBUG_LOCKS_WARN_ON(!softirq_count());
2845         } else
2846                 debug_atomic_inc(redundant_softirqs_off);
2847 }
2848 
2849 static void __lockdep_trace_alloc(gfp_t gfp_mask, unsigned long flags)
2850 {
2851         struct task_struct *curr = current;
2852 
2853         if (unlikely(!debug_locks))
2854                 return;
2855 
2856         /* no reclaim without waiting on it */
2857         if (!(gfp_mask & __GFP_DIRECT_RECLAIM))
2858                 return;
2859 
2860         /* this guy won't enter reclaim */
2861         if ((curr->flags & PF_MEMALLOC) && !(gfp_mask & __GFP_NOMEMALLOC))
2862                 return;
2863 
2864         /* We're only interested __GFP_FS allocations for now */
2865         if (!(gfp_mask & __GFP_FS))
2866                 return;
2867 
2868         /*
2869          * Oi! Can't be having __GFP_FS allocations with IRQs disabled.
2870          */
2871         if (DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags)))
2872                 return;
2873 
2874         mark_held_locks(curr, RECLAIM_FS);
2875 }
2876 
2877 static void check_flags(unsigned long flags);
2878 
2879 void lockdep_trace_alloc(gfp_t gfp_mask)
2880 {
2881         unsigned long flags;
2882 
2883         if (unlikely(current->lockdep_recursion))
2884                 return;
2885 
2886         raw_local_irq_save(flags);
2887         check_flags(flags);
2888         current->lockdep_recursion = 1;
2889         __lockdep_trace_alloc(gfp_mask, flags);
2890         current->lockdep_recursion = 0;
2891         raw_local_irq_restore(flags);
2892 }
2893 
2894 static int mark_irqflags(struct task_struct *curr, struct held_lock *hlock)
2895 {
2896         /*
2897          * If non-trylock use in a hardirq or softirq context, then
2898          * mark the lock as used in these contexts:
2899          */
2900         if (!hlock->trylock) {
2901                 if (hlock->read) {
2902                         if (curr->hardirq_context)
2903                                 if (!mark_lock(curr, hlock,
2904                                                 LOCK_USED_IN_HARDIRQ_READ))
2905                                         return 0;
2906                         if (curr->softirq_context)
2907                                 if (!mark_lock(curr, hlock,
2908                                                 LOCK_USED_IN_SOFTIRQ_READ))
2909                                         return 0;
2910                 } else {
2911                         if (curr->hardirq_context)
2912                                 if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ))
2913                                         return 0;
2914                         if (curr->softirq_context)
2915                                 if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ))
2916                                         return 0;
2917                 }
2918         }
2919         if (!hlock->hardirqs_off) {
2920                 if (hlock->read) {
2921                         if (!mark_lock(curr, hlock,
2922                                         LOCK_ENABLED_HARDIRQ_READ))
2923                                 return 0;
2924                         if (curr->softirqs_enabled)
2925                                 if (!mark_lock(curr, hlock,
2926                                                 LOCK_ENABLED_SOFTIRQ_READ))
2927                                         return 0;
2928                 } else {
2929                         if (!mark_lock(curr, hlock,
2930                                         LOCK_ENABLED_HARDIRQ))
2931                                 return 0;
2932                         if (curr->softirqs_enabled)
2933                                 if (!mark_lock(curr, hlock,
2934                                                 LOCK_ENABLED_SOFTIRQ))
2935                                         return 0;
2936                 }
2937         }
2938 
2939         /*
2940          * We reuse the irq context infrastructure more broadly as a general
2941          * context checking code. This tests GFP_FS recursion (a lock taken
2942          * during reclaim for a GFP_FS allocation is held over a GFP_FS
2943          * allocation).
2944          */
2945         if (!hlock->trylock && (curr->lockdep_reclaim_gfp & __GFP_FS)) {
2946                 if (hlock->read) {
2947                         if (!mark_lock(curr, hlock, LOCK_USED_IN_RECLAIM_FS_READ))
2948                                         return 0;
2949                 } else {
2950                         if (!mark_lock(curr, hlock, LOCK_USED_IN_RECLAIM_FS))
2951                                         return 0;
2952                 }
2953         }
2954 
2955         return 1;
2956 }
2957 
2958 static inline unsigned int task_irq_context(struct task_struct *task)
2959 {
2960         return 2 * !!task->hardirq_context + !!task->softirq_context;
2961 }
2962 
2963 static int separate_irq_context(struct task_struct *curr,
2964                 struct held_lock *hlock)
2965 {
2966         unsigned int depth = curr->lockdep_depth;
2967 
2968         /*
2969          * Keep track of points where we cross into an interrupt context:
2970          */
2971         if (depth) {
2972                 struct held_lock *prev_hlock;
2973 
2974                 prev_hlock = curr->held_locks + depth-1;
2975                 /*
2976                  * If we cross into another context, reset the
2977                  * hash key (this also prevents the checking and the
2978                  * adding of the dependency to 'prev'):
2979                  */
2980                 if (prev_hlock->irq_context != hlock->irq_context)
2981                         return 1;
2982         }
2983         return 0;
2984 }
2985 
2986 #else /* defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING) */
2987 
2988 static inline
2989 int mark_lock_irq(struct task_struct *curr, struct held_lock *this,
2990                 enum lock_usage_bit new_bit)
2991 {
2992         WARN_ON(1); /* Impossible innit? when we don't have TRACE_IRQFLAG */
2993         return 1;
2994 }
2995 
2996 static inline int mark_irqflags(struct task_struct *curr,
2997                 struct held_lock *hlock)
2998 {
2999         return 1;
3000 }
3001 
3002 static inline unsigned int task_irq_context(struct task_struct *task)
3003 {
3004         return 0;
3005 }
3006 
3007 static inline int separate_irq_context(struct task_struct *curr,
3008                 struct held_lock *hlock)
3009 {
3010         return 0;
3011 }
3012 
3013 void lockdep_trace_alloc(gfp_t gfp_mask)
3014 {
3015 }
3016 
3017 #endif /* defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING) */
3018 
3019 /*
3020  * Mark a lock with a usage bit, and validate the state transition:
3021  */
3022 static int mark_lock(struct task_struct *curr, struct held_lock *this,
3023                              enum lock_usage_bit new_bit)
3024 {
3025         unsigned int new_mask = 1 << new_bit, ret = 1;
3026 
3027         /*
3028          * If already set then do not dirty the cacheline,
3029          * nor do any checks:
3030          */
3031         if (likely(hlock_class(this)->usage_mask & new_mask))
3032                 return 1;
3033 
3034         if (!graph_lock())
3035                 return 0;
3036         /*
3037          * Make sure we didn't race:
3038          */
3039         if (unlikely(hlock_class(this)->usage_mask & new_mask)) {
3040                 graph_unlock();
3041                 return 1;
3042         }
3043 
3044         hlock_class(this)->usage_mask |= new_mask;
3045 
3046         if (!save_trace(hlock_class(this)->usage_traces + new_bit))
3047                 return 0;
3048 
3049         switch (new_bit) {
3050 #define LOCKDEP_STATE(__STATE)                  \
3051         case LOCK_USED_IN_##__STATE:            \
3052         case LOCK_USED_IN_##__STATE##_READ:     \
3053         case LOCK_ENABLED_##__STATE:            \
3054         case LOCK_ENABLED_##__STATE##_READ:
3055 #include "lockdep_states.h"
3056 #undef LOCKDEP_STATE
3057                 ret = mark_lock_irq(curr, this, new_bit);
3058                 if (!ret)
3059                         return 0;
3060                 break;
3061         case LOCK_USED:
3062                 debug_atomic_dec(nr_unused_locks);
3063                 break;
3064         default:
3065                 if (!debug_locks_off_graph_unlock())
3066                         return 0;
3067                 WARN_ON(1);
3068                 return 0;
3069         }
3070 
3071         graph_unlock();
3072 
3073         /*
3074          * We must printk outside of the graph_lock:
3075          */
3076         if (ret == 2) {
3077                 printk("\nmarked lock as {%s}:\n", usage_str[new_bit]);
3078                 print_lock(this);
3079                 print_irqtrace_events(curr);
3080                 dump_stack();
3081         }
3082 
3083         return ret;
3084 }
3085 
3086 /*
3087  * Initialize a lock instance's lock-class mapping info:
3088  */
3089 void lockdep_init_map(struct lockdep_map *lock, const char *name,
3090                       struct lock_class_key *key, int subclass)
3091 {
3092         int i;
3093 
3094         kmemcheck_mark_initialized(lock, sizeof(*lock));
3095 
3096         for (i = 0; i < NR_LOCKDEP_CACHING_CLASSES; i++)
3097                 lock->class_cache[i] = NULL;
3098 
3099 #ifdef CONFIG_LOCK_STAT
3100         lock->cpu = raw_smp_processor_id();
3101 #endif
3102 
3103         /*
3104          * Can't be having no nameless bastards around this place!
3105          */
3106         if (DEBUG_LOCKS_WARN_ON(!name)) {
3107                 lock->name = "NULL";
3108                 return;
3109         }
3110 
3111         lock->name = name;
3112 
3113         /*
3114          * No key, no joy, we need to hash something.
3115          */
3116         if (DEBUG_LOCKS_WARN_ON(!key))
3117                 return;
3118         /*
3119          * Sanity check, the lock-class key must be persistent:
3120          */
3121         if (!static_obj(key)) {
3122                 printk("BUG: key %p not in .data!\n", key);
3123                 /*
3124                  * What it says above ^^^^^, I suggest you read it.
3125                  */
3126                 DEBUG_LOCKS_WARN_ON(1);
3127                 return;
3128         }
3129         lock->key = key;
3130 
3131         if (unlikely(!debug_locks))
3132                 return;
3133 
3134         if (subclass) {
3135                 unsigned long flags;
3136 
3137                 if (DEBUG_LOCKS_WARN_ON(current->lockdep_recursion))
3138                         return;
3139 
3140                 raw_local_irq_save(flags);
3141                 current->lockdep_recursion = 1;
3142                 register_lock_class(lock, subclass, 1);
3143                 current->lockdep_recursion = 0;
3144                 raw_local_irq_restore(flags);
3145         }
3146 }
3147 EXPORT_SYMBOL_GPL(lockdep_init_map);
3148 
3149 struct lock_class_key __lockdep_no_validate__;
3150 EXPORT_SYMBOL_GPL(__lockdep_no_validate__);
3151 
3152 static int
3153 print_lock_nested_lock_not_held(struct task_struct *curr,
3154                                 struct held_lock *hlock,
3155                                 unsigned long ip)
3156 {
3157         if (!debug_locks_off())
3158                 return 0;
3159         if (debug_locks_silent)
3160                 return 0;
3161 
3162         printk("\n");
3163         printk("==================================\n");
3164         printk("[ BUG: Nested lock was not taken ]\n");
3165         print_kernel_ident();
3166         printk("----------------------------------\n");
3167 
3168         printk("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr));
3169         print_lock(hlock);
3170 
3171         printk("\nbut this task is not holding:\n");
3172         printk("%s\n", hlock->nest_lock->name);
3173 
3174         printk("\nstack backtrace:\n");
3175         dump_stack();
3176 
3177         printk("\nother info that might help us debug this:\n");
3178         lockdep_print_held_locks(curr);
3179 
3180         printk("\nstack backtrace:\n");
3181         dump_stack();
3182 
3183         return 0;
3184 }
3185 
3186 static int __lock_is_held(struct lockdep_map *lock);
3187 
3188 /*
3189  * This gets called for every mutex_lock*()/spin_lock*() operation.
3190  * We maintain the dependency maps and validate the locking attempt:
3191  */
3192 static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
3193                           int trylock, int read, int check, int hardirqs_off,
3194                           struct lockdep_map *nest_lock, unsigned long ip,
3195                           int references, int pin_count)
3196 {
3197         struct task_struct *curr = current;
3198         struct lock_class *class = NULL;
3199         struct held_lock *hlock;
3200         unsigned int depth;
3201         int chain_head = 0;
3202         int class_idx;
3203         u64 chain_key;
3204 
3205         if (unlikely(!debug_locks))
3206                 return 0;
3207 
3208         /*
3209          * Lockdep should run with IRQs disabled, otherwise we could
3210          * get an interrupt which would want to take locks, which would
3211          * end up in lockdep and have you got a head-ache already?
3212          */
3213         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
3214                 return 0;
3215 
3216         if (!prove_locking || lock->key == &__lockdep_no_validate__)
3217                 check = 0;
3218 
3219         if (subclass < NR_LOCKDEP_CACHING_CLASSES)
3220                 class = lock->class_cache[subclass];
3221         /*
3222          * Not cached?
3223          */
3224         if (unlikely(!class)) {
3225                 class = register_lock_class(lock, subclass, 0);
3226                 if (!class)
3227                         return 0;
3228         }
3229         atomic_inc((atomic_t *)&class->ops);
3230         if (very_verbose(class)) {
3231                 printk("\nacquire class [%p] %s", class->key, class->name);
3232                 if (class->name_version > 1)
3233                         printk("#%d", class->name_version);
3234                 printk("\n");
3235                 dump_stack();
3236         }
3237 
3238         /*
3239          * Add the lock to the list of currently held locks.
3240          * (we dont increase the depth just yet, up until the
3241          * dependency checks are done)
3242          */
3243         depth = curr->lockdep_depth;
3244         /*
3245          * Ran out of static storage for our per-task lock stack again have we?
3246          */
3247         if (DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH))
3248                 return 0;
3249 
3250         class_idx = class - lock_classes + 1;
3251 
3252         if (depth) {
3253                 hlock = curr->held_locks + depth - 1;
3254                 if (hlock->class_idx == class_idx && nest_lock) {
3255                         if (hlock->references)
3256                                 hlock->references++;
3257                         else
3258                                 hlock->references = 2;
3259 
3260                         return 1;
3261                 }
3262         }
3263 
3264         hlock = curr->held_locks + depth;
3265         /*
3266          * Plain impossible, we just registered it and checked it weren't no
3267          * NULL like.. I bet this mushroom I ate was good!
3268          */
3269         if (DEBUG_LOCKS_WARN_ON(!class))
3270                 return 0;
3271         hlock->class_idx = class_idx;
3272         hlock->acquire_ip = ip;
3273         hlock->instance = lock;
3274         hlock->nest_lock = nest_lock;
3275         hlock->irq_context = task_irq_context(curr);
3276         hlock->trylock = trylock;
3277         hlock->read = read;
3278         hlock->check = check;
3279         hlock->hardirqs_off = !!hardirqs_off;
3280         hlock->references = references;
3281 #ifdef CONFIG_LOCK_STAT
3282         hlock->waittime_stamp = 0;
3283         hlock->holdtime_stamp = lockstat_clock();
3284 #endif
3285         hlock->pin_count = pin_count;
3286 
3287         if (check && !mark_irqflags(curr, hlock))
3288                 return 0;
3289 
3290         /* mark it as used: */
3291         if (!mark_lock(curr, hlock, LOCK_USED))
3292                 return 0;
3293 
3294         /*
3295          * Calculate the chain hash: it's the combined hash of all the
3296          * lock keys along the dependency chain. We save the hash value
3297          * at every step so that we can get the current hash easily
3298          * after unlock. The chain hash is then used to cache dependency
3299          * results.
3300          *
3301          * The 'key ID' is what is the most compact key value to drive
3302          * the hash, not class->key.
3303          */
3304         /*
3305          * Whoops, we did it again.. ran straight out of our static allocation.
3306          */
3307         if (DEBUG_LOCKS_WARN_ON(class_idx > MAX_LOCKDEP_KEYS))
3308                 return 0;
3309 
3310         chain_key = curr->curr_chain_key;
3311         if (!depth) {
3312                 /*
3313                  * How can we have a chain hash when we ain't got no keys?!
3314                  */
3315                 if (DEBUG_LOCKS_WARN_ON(chain_key != 0))
3316                         return 0;
3317                 chain_head = 1;
3318         }
3319 
3320         hlock->prev_chain_key = chain_key;
3321         if (separate_irq_context(curr, hlock)) {
3322                 chain_key = 0;
3323                 chain_head = 1;
3324         }
3325         chain_key = iterate_chain_key(chain_key, class_idx);
3326 
3327         if (nest_lock && !__lock_is_held(nest_lock))
3328                 return print_lock_nested_lock_not_held(curr, hlock, ip);
3329 
3330         if (!validate_chain(curr, lock, hlock, chain_head, chain_key))
3331                 return 0;
3332 
3333         curr->curr_chain_key = chain_key;
3334         curr->lockdep_depth++;
3335         check_chain_key(curr);
3336 #ifdef CONFIG_DEBUG_LOCKDEP
3337         if (unlikely(!debug_locks))
3338                 return 0;
3339 #endif
3340         if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
3341                 debug_locks_off();
3342                 print_lockdep_off("BUG: MAX_LOCK_DEPTH too low!");
3343                 printk(KERN_DEBUG "depth: %i  max: %lu!\n",
3344                        curr->lockdep_depth, MAX_LOCK_DEPTH);
3345 
3346                 lockdep_print_held_locks(current);
3347                 debug_show_all_locks();
3348                 dump_stack();
3349 
3350                 return 0;
3351         }
3352 
3353         if (unlikely(curr->lockdep_depth > max_lockdep_depth))
3354                 max_lockdep_depth = curr->lockdep_depth;
3355 
3356         return 1;
3357 }
3358 
3359 static int
3360 print_unlock_imbalance_bug(struct task_struct *curr, struct lockdep_map *lock,
3361                            unsigned long ip)
3362 {
3363         if (!debug_locks_off())
3364                 return 0;
3365         if (debug_locks_silent)
3366                 return 0;
3367 
3368         printk("\n");
3369         printk("=====================================\n");
3370         printk("[ BUG: bad unlock balance detected! ]\n");
3371         print_kernel_ident();
3372         printk("-------------------------------------\n");
3373         printk("%s/%d is trying to release lock (",
3374                 curr->comm, task_pid_nr(curr));
3375         print_lockdep_cache(lock);
3376         printk(") at:\n");
3377         print_ip_sym(ip);
3378         printk("but there are no more locks to release!\n");
3379         printk("\nother info that might help us debug this:\n");
3380         lockdep_print_held_locks(curr);
3381 
3382         printk("\nstack backtrace:\n");
3383         dump_stack();
3384 
3385         return 0;
3386 }
3387 
3388 static int match_held_lock(struct held_lock *hlock, struct lockdep_map *lock)
3389 {
3390         if (hlock->instance == lock)
3391                 return 1;
3392 
3393         if (hlock->references) {
3394                 struct lock_class *class = lock->class_cache[0];
3395 
3396                 if (!class)
3397                         class = look_up_lock_class(lock, 0);
3398 
3399                 /*
3400                  * If look_up_lock_class() failed to find a class, we're trying
3401                  * to test if we hold a lock that has never yet been acquired.
3402                  * Clearly if the lock hasn't been acquired _ever_, we're not
3403                  * holding it either, so report failure.
3404                  */
3405                 if (!class)
3406                         return 0;
3407 
3408                 /*
3409                  * References, but not a lock we're actually ref-counting?
3410                  * State got messed up, follow the sites that change ->references
3411                  * and try to make sense of it.
3412                  */
3413                 if (DEBUG_LOCKS_WARN_ON(!hlock->nest_lock))
3414                         return 0;
3415 
3416                 if (hlock->class_idx == class - lock_classes + 1)
3417                         return 1;
3418         }
3419 
3420         return 0;
3421 }
3422 
3423 static int
3424 __lock_set_class(struct lockdep_map *lock, const char *name,
3425                  struct lock_class_key *key, unsigned int subclass,
3426                  unsigned long ip)
3427 {
3428         struct task_struct *curr = current;
3429         struct held_lock *hlock, *prev_hlock;
3430         struct lock_class *class;
3431         unsigned int depth;
3432         int i;
3433 
3434         depth = curr->lockdep_depth;
3435         /*
3436          * This function is about (re)setting the class of a held lock,
3437          * yet we're not actually holding any locks. Naughty user!
3438          */
3439         if (DEBUG_LOCKS_WARN_ON(!depth))
3440                 return 0;
3441 
3442         prev_hlock = NULL;
3443         for (i = depth-1; i >= 0; i--) {
3444                 hlock = curr->held_locks + i;
3445                 /*
3446                  * We must not cross into another context:
3447                  */
3448                 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3449                         break;
3450                 if (match_held_lock(hlock, lock))
3451                         goto found_it;
3452                 prev_hlock = hlock;
3453         }
3454         return print_unlock_imbalance_bug(curr, lock, ip);
3455 
3456 found_it:
3457         lockdep_init_map(lock, name, key, 0);
3458         class = register_lock_class(lock, subclass, 0);
3459         hlock->class_idx = class - lock_classes + 1;
3460 
3461         curr->lockdep_depth = i;
3462         curr->curr_chain_key = hlock->prev_chain_key;
3463 
3464         for (; i < depth; i++) {
3465                 hlock = curr->held_locks + i;
3466                 if (!__lock_acquire(hlock->instance,
3467                         hlock_class(hlock)->subclass, hlock->trylock,
3468                                 hlock->read, hlock->check, hlock->hardirqs_off,
3469                                 hlock->nest_lock, hlock->acquire_ip,
3470                                 hlock->references, hlock->pin_count))
3471                         return 0;
3472         }
3473 
3474         /*
3475          * I took it apart and put it back together again, except now I have
3476          * these 'spare' parts.. where shall I put them.
3477          */
3478         if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth))
3479                 return 0;
3480         return 1;
3481 }
3482 
3483 /*
3484  * Remove the lock to the list of currently held locks - this gets
3485  * called on mutex_unlock()/spin_unlock*() (or on a failed
3486  * mutex_lock_interruptible()).
3487  *
3488  * @nested is an hysterical artifact, needs a tree wide cleanup.
3489  */
3490 static int
3491 __lock_release(struct lockdep_map *lock, int nested, unsigned long ip)
3492 {
3493         struct task_struct *curr = current;
3494         struct held_lock *hlock, *prev_hlock;
3495         unsigned int depth;
3496         int i;
3497 
3498         if (unlikely(!debug_locks))
3499                 return 0;
3500 
3501         depth = curr->lockdep_depth;
3502         /*
3503          * So we're all set to release this lock.. wait what lock? We don't
3504          * own any locks, you've been drinking again?
3505          */
3506         if (DEBUG_LOCKS_WARN_ON(depth <= 0))
3507                  return print_unlock_imbalance_bug(curr, lock, ip);
3508 
3509         /*
3510          * Check whether the lock exists in the current stack
3511          * of held locks:
3512          */
3513         prev_hlock = NULL;
3514         for (i = depth-1; i >= 0; i--) {
3515                 hlock = curr->held_locks + i;
3516                 /*
3517                  * We must not cross into another context:
3518                  */
3519                 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3520                         break;
3521                 if (match_held_lock(hlock, lock))
3522                         goto found_it;
3523                 prev_hlock = hlock;
3524         }
3525         return print_unlock_imbalance_bug(curr, lock, ip);
3526 
3527 found_it:
3528         if (hlock->instance == lock)
3529                 lock_release_holdtime(hlock);
3530 
3531         WARN(hlock->pin_count, "releasing a pinned lock\n");
3532 
3533         if (hlock->references) {
3534                 hlock->references--;
3535                 if (hlock->references) {
3536                         /*
3537                          * We had, and after removing one, still have
3538                          * references, the current lock stack is still
3539                          * valid. We're done!
3540                          */
3541                         return 1;
3542                 }
3543         }
3544 
3545         /*
3546          * We have the right lock to unlock, 'hlock' points to it.
3547          * Now we remove it from the stack, and add back the other
3548          * entries (if any), recalculating the hash along the way:
3549          */
3550 
3551         curr->lockdep_depth = i;
3552         curr->curr_chain_key = hlock->prev_chain_key;
3553 
3554         for (i++; i < depth; i++) {
3555                 hlock = curr->held_locks + i;
3556                 if (!__lock_acquire(hlock->instance,
3557                         hlock_class(hlock)->subclass, hlock->trylock,
3558                                 hlock->read, hlock->check, hlock->hardirqs_off,
3559                                 hlock->nest_lock, hlock->acquire_ip,
3560                                 hlock->references, hlock->pin_count))
3561                         return 0;
3562         }
3563 
3564         /*
3565          * We had N bottles of beer on the wall, we drank one, but now
3566          * there's not N-1 bottles of beer left on the wall...
3567          */
3568         if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - 1))
3569                 return 0;
3570 
3571         return 1;
3572 }
3573 
3574 static int __lock_is_held(struct lockdep_map *lock)
3575 {
3576         struct task_struct *curr = current;
3577         int i;
3578 
3579         for (i = 0; i < curr->lockdep_depth; i++) {
3580                 struct held_lock *hlock = curr->held_locks + i;
3581 
3582                 if (match_held_lock(hlock, lock))
3583                         return 1;
3584         }
3585 
3586         return 0;
3587 }
3588 
3589 static struct pin_cookie __lock_pin_lock(struct lockdep_map *lock)
3590 {
3591         struct pin_cookie cookie = NIL_COOKIE;
3592         struct task_struct *curr = current;
3593         int i;
3594 
3595         if (unlikely(!debug_locks))
3596                 return cookie;
3597 
3598         for (i = 0; i < curr->lockdep_depth; i++) {
3599                 struct held_lock *hlock = curr->held_locks + i;
3600 
3601                 if (match_held_lock(hlock, lock)) {
3602                         /*
3603                          * Grab 16bits of randomness; this is sufficient to not
3604                          * be guessable and still allows some pin nesting in
3605                          * our u32 pin_count.
3606                          */
3607                         cookie.val = 1 + (prandom_u32() >> 16);
3608                         hlock->pin_count += cookie.val;
3609                         return cookie;
3610                 }
3611         }
3612 
3613         WARN(1, "pinning an unheld lock\n");
3614         return cookie;
3615 }
3616 
3617 static void __lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
3618 {
3619         struct task_struct *curr = current;
3620         int i;
3621 
3622         if (unlikely(!debug_locks))
3623                 return;
3624 
3625         for (i = 0; i < curr->lockdep_depth; i++) {
3626                 struct held_lock *hlock = curr->held_locks + i;
3627 
3628                 if (match_held_lock(hlock, lock)) {
3629                         hlock->pin_count += cookie.val;
3630                         return;
3631                 }
3632         }
3633 
3634         WARN(1, "pinning an unheld lock\n");
3635 }
3636 
3637 static void __lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
3638 {
3639         struct task_struct *curr = current;
3640         int i;
3641 
3642         if (unlikely(!debug_locks))
3643                 return;
3644 
3645         for (i = 0; i < curr->lockdep_depth; i++) {
3646                 struct held_lock *hlock = curr->held_locks + i;
3647 
3648                 if (match_held_lock(hlock, lock)) {
3649                         if (WARN(!hlock->pin_count, "unpinning an unpinned lock\n"))
3650                                 return;
3651 
3652                         hlock->pin_count -= cookie.val;
3653 
3654                         if (WARN((int)hlock->pin_count < 0, "pin count corrupted\n"))
3655                                 hlock->pin_count = 0;
3656 
3657                         return;
3658                 }
3659         }
3660 
3661         WARN(1, "unpinning an unheld lock\n");
3662 }
3663 
3664 /*
3665  * Check whether we follow the irq-flags state precisely:
3666  */
3667 static void check_flags(unsigned long flags)
3668 {
3669 #if defined(CONFIG_PROVE_LOCKING) && defined(CONFIG_DEBUG_LOCKDEP) && \
3670     defined(CONFIG_TRACE_IRQFLAGS)
3671         if (!debug_locks)
3672                 return;
3673 
3674         if (irqs_disabled_flags(flags)) {
3675                 if (DEBUG_LOCKS_WARN_ON(current->hardirqs_enabled)) {
3676                         printk("possible reason: unannotated irqs-off.\n");
3677                 }
3678         } else {
3679                 if (DEBUG_LOCKS_WARN_ON(!current->hardirqs_enabled)) {
3680                         printk("possible reason: unannotated irqs-on.\n");
3681                 }
3682         }
3683 
3684         /*
3685          * We dont accurately track softirq state in e.g.
3686          * hardirq contexts (such as on 4KSTACKS), so only
3687          * check if not in hardirq contexts:
3688          */
3689         if (!hardirq_count()) {
3690                 if (softirq_count()) {
3691                         /* like the above, but with softirqs */
3692                         DEBUG_LOCKS_WARN_ON(current->softirqs_enabled);
3693                 } else {
3694                         /* lick the above, does it taste good? */
3695                         DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled);
3696                 }
3697         }
3698 
3699         if (!debug_locks)
3700                 print_irqtrace_events(current);
3701 #endif
3702 }
3703 
3704 void lock_set_class(struct lockdep_map *lock, const char *name,
3705                     struct lock_class_key *key, unsigned int subclass,
3706                     unsigned long ip)
3707 {
3708         unsigned long flags;
3709 
3710         if (unlikely(current->lockdep_recursion))
3711                 return;
3712 
3713         raw_local_irq_save(flags);
3714         current->lockdep_recursion = 1;
3715         check_flags(flags);
3716         if (__lock_set_class(lock, name, key, subclass, ip))
3717                 check_chain_key(current);
3718         current->lockdep_recursion = 0;
3719         raw_local_irq_restore(flags);
3720 }
3721 EXPORT_SYMBOL_GPL(lock_set_class);
3722 
3723 /*
3724  * We are not always called with irqs disabled - do that here,
3725  * and also avoid lockdep recursion:
3726  */
3727 void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
3728                           int trylock, int read, int check,
3729                           struct lockdep_map *nest_lock, unsigned long ip)
3730 {
3731         unsigned long flags;
3732 
3733         if (unlikely(current->lockdep_recursion))
3734                 return;
3735 
3736         raw_local_irq_save(flags);
3737         check_flags(flags);
3738 
3739         current->lockdep_recursion = 1;
3740         trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip);
3741         __lock_acquire(lock, subclass, trylock, read, check,
3742                        irqs_disabled_flags(flags), nest_lock, ip, 0, 0);
3743         current->lockdep_recursion = 0;
3744         raw_local_irq_restore(flags);
3745 }
3746 EXPORT_SYMBOL_GPL(lock_acquire);
3747 
3748 void lock_release(struct lockdep_map *lock, int nested,
3749                           unsigned long ip)
3750 {
3751         unsigned long flags;
3752 
3753         if (unlikely(current->lockdep_recursion))
3754                 return;
3755 
3756         raw_local_irq_save(flags);
3757         check_flags(flags);
3758         current->lockdep_recursion = 1;
3759         trace_lock_release(lock, ip);
3760         if (__lock_release(lock, nested, ip))
3761                 check_chain_key(current);
3762         current->lockdep_recursion = 0;
3763         raw_local_irq_restore(flags);
3764 }
3765 EXPORT_SYMBOL_GPL(lock_release);
3766 
3767 int lock_is_held(struct lockdep_map *lock)
3768 {
3769         unsigned long flags;
3770         int ret = 0;
3771 
3772         if (unlikely(current->lockdep_recursion))
3773                 return 1; /* avoid false negative lockdep_assert_held() */
3774 
3775         raw_local_irq_save(flags);
3776         check_flags(flags);
3777 
3778         current->lockdep_recursion = 1;
3779         ret = __lock_is_held(lock);
3780         current->lockdep_recursion = 0;
3781         raw_local_irq_restore(flags);
3782 
3783         return ret;
3784 }
3785 EXPORT_SYMBOL_GPL(lock_is_held);
3786 
3787 struct pin_cookie lock_pin_lock(struct lockdep_map *lock)
3788 {
3789         struct pin_cookie cookie = NIL_COOKIE;
3790         unsigned long flags;
3791 
3792         if (unlikely(current->lockdep_recursion))
3793                 return cookie;
3794 
3795         raw_local_irq_save(flags);
3796         check_flags(flags);
3797 
3798         current->lockdep_recursion = 1;
3799         cookie = __lock_pin_lock(lock);
3800         current->lockdep_recursion = 0;
3801         raw_local_irq_restore(flags);
3802 
3803         return cookie;
3804 }
3805 EXPORT_SYMBOL_GPL(lock_pin_lock);
3806 
3807 void lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
3808 {
3809         unsigned long flags;
3810 
3811         if (unlikely(current->lockdep_recursion))
3812                 return;
3813 
3814         raw_local_irq_save(flags);
3815         check_flags(flags);
3816 
3817         current->lockdep_recursion = 1;
3818         __lock_repin_lock(lock, cookie);
3819         current->lockdep_recursion = 0;
3820         raw_local_irq_restore(flags);
3821 }
3822 EXPORT_SYMBOL_GPL(lock_repin_lock);
3823 
3824 void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
3825 {
3826         unsigned long flags;
3827 
3828         if (unlikely(current->lockdep_recursion))
3829                 return;
3830 
3831         raw_local_irq_save(flags);
3832         check_flags(flags);
3833 
3834         current->lockdep_recursion = 1;
3835         __lock_unpin_lock(lock, cookie);
3836         current->lockdep_recursion = 0;
3837         raw_local_irq_restore(flags);
3838 }
3839 EXPORT_SYMBOL_GPL(lock_unpin_lock);
3840 
3841 void lockdep_set_current_reclaim_state(gfp_t gfp_mask)
3842 {
3843         current->lockdep_reclaim_gfp = gfp_mask;
3844 }
3845 
3846 void lockdep_clear_current_reclaim_state(void)
3847 {
3848         current->lockdep_reclaim_gfp = 0;
3849 }
3850 
3851 #ifdef CONFIG_LOCK_STAT
3852 static int
3853 print_lock_contention_bug(struct task_struct *curr, struct lockdep_map *lock,
3854                            unsigned long ip)
3855 {
3856         if (!debug_locks_off())
3857                 return 0;
3858         if (debug_locks_silent)
3859                 return 0;
3860 
3861         printk("\n");
3862         printk("=================================\n");
3863         printk("[ BUG: bad contention detected! ]\n");
3864         print_kernel_ident();
3865         printk("---------------------------------\n");
3866         printk("%s/%d is trying to contend lock (",
3867                 curr->comm, task_pid_nr(curr));
3868         print_lockdep_cache(lock);
3869         printk(") at:\n");
3870         print_ip_sym(ip);
3871         printk("but there are no locks held!\n");
3872         printk("\nother info that might help us debug this:\n");
3873         lockdep_print_held_locks(curr);
3874 
3875         printk("\nstack backtrace:\n");
3876         dump_stack();
3877 
3878         return 0;
3879 }
3880 
3881 static void
3882 __lock_contended(struct lockdep_map *lock, unsigned long ip)
3883 {
3884         struct task_struct *curr = current;
3885         struct held_lock *hlock, *prev_hlock;
3886         struct lock_class_stats *stats;
3887         unsigned int depth;
3888         int i, contention_point, contending_point;
3889 
3890         depth = curr->lockdep_depth;
3891         /*
3892          * Whee, we contended on this lock, except it seems we're not
3893          * actually trying to acquire anything much at all..
3894          */
3895         if (DEBUG_LOCKS_WARN_ON(!depth))
3896                 return;
3897 
3898         prev_hlock = NULL;
3899         for (i = depth-1; i >= 0; i--) {
3900                 hlock = curr->held_locks + i;
3901                 /*
3902                  * We must not cross into another context:
3903                  */
3904                 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3905                         break;
3906                 if (match_held_lock(hlock, lock))
3907                         goto found_it;
3908                 prev_hlock = hlock;
3909         }
3910         print_lock_contention_bug(curr, lock, ip);
3911         return;
3912 
3913 found_it:
3914         if (hlock->instance != lock)
3915                 return;
3916 
3917         hlock->waittime_stamp = lockstat_clock();
3918 
3919         contention_point = lock_point(hlock_class(hlock)->contention_point, ip);
3920         contending_point = lock_point(hlock_class(hlock)->contending_point,
3921                                       lock->ip);
3922 
3923         stats = get_lock_stats(hlock_class(hlock));
3924         if (contention_point < LOCKSTAT_POINTS)
3925                 stats->contention_point[contention_point]++;
3926         if (contending_point < LOCKSTAT_POINTS)
3927                 stats->contending_point[contending_point]++;
3928         if (lock->cpu != smp_processor_id())
3929                 stats->bounces[bounce_contended + !!hlock->read]++;
3930         put_lock_stats(stats);
3931 }
3932 
3933 static void
3934 __lock_acquired(struct lockdep_map *lock, unsigned long ip)
3935 {
3936         struct task_struct *curr = current;
3937         struct held_lock *hlock, *prev_hlock;
3938         struct lock_class_stats *stats;
3939         unsigned int depth;
3940         u64 now, waittime = 0;
3941         int i, cpu;
3942 
3943         depth = curr->lockdep_depth;
3944         /*
3945          * Yay, we acquired ownership of this lock we didn't try to
3946          * acquire, how the heck did that happen?
3947          */
3948         if (DEBUG_LOCKS_WARN_ON(!depth))
3949                 return;
3950 
3951         prev_hlock = NULL;
3952         for (i = depth-1; i >= 0; i--) {
3953                 hlock = curr->held_locks + i;
3954                 /*
3955                  * We must not cross into another context:
3956                  */
3957                 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3958                         break;
3959                 if (match_held_lock(hlock, lock))
3960                         goto found_it;
3961                 prev_hlock = hlock;
3962         }
3963         print_lock_contention_bug(curr, lock, _RET_IP_);
3964         return;
3965 
3966 found_it:
3967         if (hlock->instance != lock)
3968                 return;
3969 
3970         cpu = smp_processor_id();
3971         if (hlock->waittime_stamp) {
3972                 now = lockstat_clock();
3973                 waittime = now - hlock->waittime_stamp;
3974                 hlock->holdtime_stamp = now;
3975         }
3976 
3977         trace_lock_acquired(lock, ip);
3978 
3979         stats = get_lock_stats(hlock_class(hlock));
3980         if (waittime) {
3981                 if (hlock->read)
3982                         lock_time_inc(&stats->read_waittime, waittime);
3983                 else
3984                         lock_time_inc(&stats->write_waittime, waittime);
3985         }
3986         if (lock->cpu != cpu)
3987                 stats->bounces[bounce_acquired + !!hlock->read]++;
3988         put_lock_stats(stats);
3989 
3990         lock->cpu = cpu;
3991         lock->ip = ip;
3992 }
3993 
3994 void lock_contended(struct lockdep_map *lock, unsigned long ip)
3995 {
3996         unsigned long flags;
3997 
3998         if (unlikely(!lock_stat))
3999                 return;
4000 
4001         if (unlikely(current->lockdep_recursion))
4002                 return;
4003 
4004         raw_local_irq_save(flags);
4005         check_flags(flags);
4006         current->lockdep_recursion = 1;
4007         trace_lock_contended(lock, ip);
4008         __lock_contended(lock, ip);
4009         current->lockdep_recursion = 0;
4010         raw_local_irq_restore(flags);
4011 }
4012 EXPORT_SYMBOL_GPL(lock_contended);
4013 
4014 void lock_acquired(struct lockdep_map *lock, unsigned long ip)
4015 {
4016         unsigned long flags;
4017 
4018         if (unlikely(!lock_stat))
4019                 return;
4020 
4021         if (unlikely(current->lockdep_recursion))
4022                 return;
4023 
4024         raw_local_irq_save(flags);
4025         check_flags(flags);
4026         current->lockdep_recursion = 1;
4027         __lock_acquired(lock, ip);
4028         current->lockdep_recursion = 0;
4029         raw_local_irq_restore(flags);
4030 }
4031 EXPORT_SYMBOL_GPL(lock_acquired);
4032 #endif
4033 
4034 /*
4035  * Used by the testsuite, sanitize the validator state
4036  * after a simulated failure:
4037  */
4038 
4039 void lockdep_reset(void)
4040 {
4041         unsigned long flags;
4042         int i;
4043 
4044         raw_local_irq_save(flags);
4045         current->curr_chain_key = 0;
4046         current->lockdep_depth = 0;
4047         current->lockdep_recursion = 0;
4048         memset(current->held_locks, 0, MAX_LOCK_DEPTH*sizeof(struct held_lock));
4049         nr_hardirq_chains = 0;
4050         nr_softirq_chains = 0;
4051         nr_process_chains = 0;
4052         debug_locks = 1;
4053         for (i = 0; i < CHAINHASH_SIZE; i++)
4054                 INIT_HLIST_HEAD(chainhash_table + i);
4055         raw_local_irq_restore(flags);
4056 }
4057 
4058 static void zap_class(struct lock_class *class)
4059 {
4060         int i;
4061 
4062         /*
4063          * Remove all dependencies this lock is
4064          * involved in:
4065          */
4066         for (i = 0; i < nr_list_entries; i++) {
4067                 if (list_entries[i].class == class)
4068                         list_del_rcu(&list_entries[i].entry);
4069         }
4070         /*
4071          * Unhash the class and remove it from the all_lock_classes list:
4072          */
4073         hlist_del_rcu(&class->hash_entry);
4074         list_del_rcu(&class->lock_entry);
4075 
4076         RCU_INIT_POINTER(class->key, NULL);
4077         RCU_INIT_POINTER(class->name, NULL);
4078 }
4079 
4080 static inline int within(const void *addr, void *start, unsigned long size)
4081 {
4082         return addr >= start && addr < start + size;
4083 }
4084 
4085 /*
4086  * Used in module.c to remove lock classes from memory that is going to be
4087  * freed; and possibly re-used by other modules.
4088  *
4089  * We will have had one sync_sched() before getting here, so we're guaranteed
4090  * nobody will look up these exact classes -- they're properly dead but still
4091  * allocated.
4092  */
4093 void lockdep_free_key_range(void *start, unsigned long size)
4094 {
4095         struct lock_class *class;
4096         struct hlist_head *head;
4097         unsigned long flags;
4098         int i;
4099         int locked;
4100 
4101         raw_local_irq_save(flags);
4102         locked = graph_lock();
4103 
4104         /*
4105          * Unhash all classes that were created by this module:
4106          */
4107         for (i = 0; i < CLASSHASH_SIZE; i++) {
4108                 head = classhash_table + i;
4109                 hlist_for_each_entry_rcu(class, head, hash_entry) {
4110                         if (within(class->key, start, size))
4111                                 zap_class(class);
4112                         else if (within(class->name, start, size))
4113                                 zap_class(class);
4114                 }
4115         }
4116 
4117         if (locked)
4118                 graph_unlock();
4119         raw_local_irq_restore(flags);
4120 
4121         /*
4122          * Wait for any possible iterators from look_up_lock_class() to pass
4123          * before continuing to free the memory they refer to.
4124          *
4125          * sync_sched() is sufficient because the read-side is IRQ disable.
4126          */
4127         synchronize_sched();
4128 
4129         /*
4130          * XXX at this point we could return the resources to the pool;
4131          * instead we leak them. We would need to change to bitmap allocators
4132          * instead of the linear allocators we have now.
4133          */
4134 }
4135 
4136 void lockdep_reset_lock(struct lockdep_map *lock)
4137 {
4138         struct lock_class *class;
4139         struct hlist_head *head;
4140         unsigned long flags;
4141         int i, j;
4142         int locked;
4143 
4144         raw_local_irq_save(flags);
4145 
4146         /*
4147          * Remove all classes this lock might have:
4148          */
4149         for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) {
4150                 /*
4151                  * If the class exists we look it up and zap it:
4152                  */
4153                 class = look_up_lock_class(lock, j);
4154                 if (class)
4155                         zap_class(class);
4156         }
4157         /*
4158          * Debug check: in the end all mapped classes should
4159          * be gone.
4160          */
4161         locked = graph_lock();
4162         for (i = 0; i < CLASSHASH_SIZE; i++) {
4163                 head = classhash_table + i;
4164                 hlist_for_each_entry_rcu(class, head, hash_entry) {
4165                         int match = 0;
4166 
4167                         for (j = 0; j < NR_LOCKDEP_CACHING_CLASSES; j++)
4168                                 match |= class == lock->class_cache[j];
4169 
4170                         if (unlikely(match)) {
4171                                 if (debug_locks_off_graph_unlock()) {
4172                                         /*
4173                                          * We all just reset everything, how did it match?
4174                                          */
4175                                         WARN_ON(1);
4176                                 }
4177                                 goto out_restore;
4178                         }
4179                 }
4180         }
4181         if (locked)
4182                 graph_unlock();
4183 
4184 out_restore:
4185         raw_local_irq_restore(flags);
4186 }
4187 
4188 void __init lockdep_info(void)
4189 {
4190         printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");
4191 
4192         printk("... MAX_LOCKDEP_SUBCLASSES:  %lu\n", MAX_LOCKDEP_SUBCLASSES);
4193         printk("... MAX_LOCK_DEPTH:          %lu\n", MAX_LOCK_DEPTH);
4194         printk("... MAX_LOCKDEP_KEYS:        %lu\n", MAX_LOCKDEP_KEYS);
4195         printk("... CLASSHASH_SIZE:          %lu\n", CLASSHASH_SIZE);
4196         printk("... MAX_LOCKDEP_ENTRIES:     %lu\n", MAX_LOCKDEP_ENTRIES);
4197         printk("... MAX_LOCKDEP_CHAINS:      %lu\n", MAX_LOCKDEP_CHAINS);
4198         printk("... CHAINHASH_SIZE:          %lu\n", CHAINHASH_SIZE);
4199 
4200         printk(" memory used by lock dependency info: %lu kB\n",
4201                 (sizeof(struct lock_class) * MAX_LOCKDEP_KEYS +
4202                 sizeof(struct list_head) * CLASSHASH_SIZE +
4203                 sizeof(struct lock_list) * MAX_LOCKDEP_ENTRIES +
4204                 sizeof(struct lock_chain) * MAX_LOCKDEP_CHAINS +
4205                 sizeof(struct list_head) * CHAINHASH_SIZE
4206 #ifdef CONFIG_PROVE_LOCKING
4207                 + sizeof(struct circular_queue)
4208 #endif
4209                 ) / 1024
4210                 );
4211 
4212         printk(" per task-struct memory footprint: %lu bytes\n",
4213                 sizeof(struct held_lock) * MAX_LOCK_DEPTH);
4214 }
4215 
4216 static void
4217 print_freed_lock_bug(struct task_struct *curr, const void *mem_from,
4218                      const void *mem_to, struct held_lock *hlock)
4219 {
4220         if (!debug_locks_off())
4221                 return;
4222         if (debug_locks_silent)
4223                 return;
4224 
4225         printk("\n");
4226         printk("=========================\n");
4227         printk("[ BUG: held lock freed! ]\n");
4228         print_kernel_ident();
4229         printk("-------------------------\n");
4230         printk("%s/%d is freeing memory %p-%p, with a lock still held there!\n",
4231                 curr->comm, task_pid_nr(curr), mem_from, mem_to-1);
4232         print_lock(hlock);
4233         lockdep_print_held_locks(curr);
4234 
4235         printk("\nstack backtrace:\n");
4236         dump_stack();
4237 }
4238 
4239 static inline int not_in_range(const void* mem_from, unsigned long mem_len,
4240                                 const void* lock_from, unsigned long lock_len)
4241 {
4242         return lock_from + lock_len <= mem_from ||
4243                 mem_from + mem_len <= lock_from;
4244 }
4245 
4246 /*
4247  * Called when kernel memory is freed (or unmapped), or if a lock
4248  * is destroyed or reinitialized - this code checks whether there is
4249  * any held lock in the memory range of <from> to <to>:
4250  */
4251 void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len)
4252 {
4253         struct task_struct *curr = current;
4254         struct held_lock *hlock;
4255         unsigned long flags;
4256         int i;
4257 
4258         if (unlikely(!debug_locks))
4259                 return;
4260 
4261         local_irq_save(flags);
4262         for (i = 0; i < curr->lockdep_depth; i++) {
4263                 hlock = curr->held_locks + i;
4264 
4265                 if (not_in_range(mem_from, mem_len, hlock->instance,
4266                                         sizeof(*hlock->instance)))
4267                         continue;
4268 
4269                 print_freed_lock_bug(curr, mem_from, mem_from + mem_len, hlock);
4270                 break;
4271         }
4272         local_irq_restore(flags);
4273 }
4274 EXPORT_SYMBOL_GPL(debug_check_no_locks_freed);
4275 
4276 static void print_held_locks_bug(void)
4277 {
4278         if (!debug_locks_off())
4279                 return;
4280         if (debug_locks_silent)
4281                 return;
4282 
4283         printk("\n");
4284         printk("=====================================\n");
4285         printk("[ BUG: %s/%d still has locks held! ]\n",
4286                current->comm, task_pid_nr(current));
4287         print_kernel_ident();
4288         printk("-------------------------------------\n");
4289         lockdep_print_held_locks(current);
4290         printk("\nstack backtrace:\n");
4291         dump_stack();
4292 }
4293 
4294 void debug_check_no_locks_held(void)
4295 {
4296         if (unlikely(current->lockdep_depth > 0))
4297                 print_held_locks_bug();
4298 }
4299 EXPORT_SYMBOL_GPL(debug_check_no_locks_held);
4300 
4301 #ifdef __KERNEL__
4302 void debug_show_all_locks(void)
4303 {
4304         struct task_struct *g, *p;
4305         int count = 10;
4306         int unlock = 1;
4307 
4308         if (unlikely(!debug_locks)) {
4309                 printk("INFO: lockdep is turned off.\n");
4310                 return;
4311         }
4312         printk("\nShowing all locks held in the system:\n");
4313 
4314         /*
4315          * Here we try to get the tasklist_lock as hard as possible,
4316          * if not successful after 2 seconds we ignore it (but keep
4317          * trying). This is to enable a debug printout even if a
4318          * tasklist_lock-holding task deadlocks or crashes.
4319          */
4320 retry:
4321         if (!read_trylock(&tasklist_lock)) {
4322                 if (count == 10)
4323                         printk("hm, tasklist_lock locked, retrying... ");
4324                 if (count) {
4325                         count--;
4326                         printk(" #%d", 10-count);
4327                         mdelay(200);
4328                         goto retry;
4329                 }
4330                 printk(" ignoring it.\n");
4331                 unlock = 0;
4332         } else {
4333                 if (count != 10)
4334                         printk(KERN_CONT " locked it.\n");
4335         }
4336 
4337         do_each_thread(g, p) {
4338                 /*
4339                  * It's not reliable to print a task's held locks
4340                  * if it's not sleeping (or if it's not the current
4341                  * task):
4342                  */
4343                 if (p->state == TASK_RUNNING && p != current)
4344                         continue;
4345                 if (p->lockdep_depth)
4346                         lockdep_print_held_locks(p);
4347                 if (!unlock)
4348                         if (read_trylock(&tasklist_lock))
4349                                 unlock = 1;
4350         } while_each_thread(g, p);
4351 
4352         printk("\n");
4353         printk("=============================================\n\n");
4354 
4355         if (unlock)
4356                 read_unlock(&tasklist_lock);
4357 }
4358 EXPORT_SYMBOL_GPL(debug_show_all_locks);
4359 #endif
4360 
4361 /*
4362  * Careful: only use this function if you are sure that
4363  * the task cannot run in parallel!
4364  */
4365 void debug_show_held_locks(struct task_struct *task)
4366 {
4367         if (unlikely(!debug_locks)) {
4368                 printk("INFO: lockdep is turned off.\n");
4369                 return;
4370         }
4371         lockdep_print_held_locks(task);
4372 }
4373 EXPORT_SYMBOL_GPL(debug_show_held_locks);
4374 
4375 asmlinkage __visible void lockdep_sys_exit(void)
4376 {
4377         struct task_struct *curr = current;
4378 
4379         if (unlikely(curr->lockdep_depth)) {
4380                 if (!debug_locks_off())
4381                         return;
4382                 printk("\n");
4383                 printk("================================================\n");
4384                 printk("[ BUG: lock held when returning to user space! ]\n");
4385                 print_kernel_ident();
4386                 printk("------------------------------------------------\n");
4387                 printk("%s/%d is leaving the kernel with locks still held!\n",
4388                                 curr->comm, curr->pid);
4389                 lockdep_print_held_locks(curr);
4390         }
4391 }
4392 
4393 void lockdep_rcu_suspicious(const char *file, const int line, const char *s)
4394 {
4395         struct task_struct *curr = current;
4396 
4397 #ifndef CONFIG_PROVE_RCU_REPEATEDLY
4398         if (!debug_locks_off())
4399                 return;
4400 #endif /* #ifdef CONFIG_PROVE_RCU_REPEATEDLY */
4401         /* Note: the following can be executed concurrently, so be careful. */
4402         printk("\n");
4403         printk("===============================\n");
4404         printk("[ INFO: suspicious RCU usage. ]\n");
4405         print_kernel_ident();
4406         printk("-------------------------------\n");
4407         printk("%s:%d %s!\n", file, line, s);
4408         printk("\nother info that might help us debug this:\n\n");
4409         printk("\n%srcu_scheduler_active = %d, debug_locks = %d\n",
4410                !rcu_lockdep_current_cpu_online()
4411                         ? "RCU used illegally from offline CPU!\n"
4412                         : !rcu_is_watching()
4413                                 ? "RCU used illegally from idle CPU!\n"
4414                                 : "",
4415                rcu_scheduler_active, debug_locks);
4416 
4417         /*
4418          * If a CPU is in the RCU-free window in idle (ie: in the section
4419          * between rcu_idle_enter() and rcu_idle_exit(), then RCU
4420          * considers that CPU to be in an "extended quiescent state",
4421          * which means that RCU will be completely ignoring that CPU.
4422          * Therefore, rcu_read_lock() and friends have absolutely no
4423          * effect on a CPU running in that state. In other words, even if
4424          * such an RCU-idle CPU has called rcu_read_lock(), RCU might well
4425          * delete data structures out from under it.  RCU really has no
4426          * choice here: we need to keep an RCU-free window in idle where
4427          * the CPU may possibly enter into low power mode. This way we can
4428          * notice an extended quiescent state to other CPUs that started a grace
4429          * period. Otherwise we would delay any grace period as long as we run
4430          * in the idle task.
4431          *
4432          * So complain bitterly if someone does call rcu_read_lock(),
4433          * rcu_read_lock_bh() and so on from extended quiescent states.
4434          */
4435         if (!rcu_is_watching())
4436                 printk("RCU used illegally from extended quiescent state!\n");
4437 
4438         lockdep_print_held_locks(curr);
4439         printk("\nstack backtrace:\n");
4440         dump_stack();
4441 }
4442 EXPORT_SYMBOL_GPL(lockdep_rcu_suspicious);
4443 

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