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

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