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

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