4 * Runtime locking correctness validator
6 * Started by Ingo Molnar:
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>
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:
14 * - lock inversion scenarios
15 * - circular lock dependencies
16 * - hardirq/softirq safe/unsafe locking bugs
18 * Bugs are reported even if the current locking scenario does not cause
19 * any deadlock at this point.
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.
25 * Thanks to Arjan van de Ven for coming up with the initial idea of
26 * mapping lock dependencies runtime.
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>
47 #include <asm/sections.h>
49 #include "lockdep_internals.h"
51 #define CREATE_TRACE_POINTS
52 #include <trace/events/lock.h>
54 #ifdef CONFIG_PROVE_LOCKING
55 int prove_locking = 1;
56 module_param(prove_locking, int, 0644);
58 #define prove_locking 0
61 #ifdef CONFIG_LOCK_STAT
63 module_param(lock_stat, int, 0644);
69 * lockdep_lock: protects the lockdep graph, the hashes and the
70 * class/list/hash allocators.
72 * This is one of the rare exceptions where it's justified
73 * to use a raw spinlock - we really dont want the spinlock
74 * code to recurse back into the lockdep code...
76 static arch_spinlock_t lockdep_lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
78 static int graph_lock(void)
80 arch_spin_lock(&lockdep_lock);
82 * Make sure that if another CPU detected a bug while
83 * walking the graph we dont change it (while the other
84 * CPU is busy printing out stuff with the graph lock
88 arch_spin_unlock(&lockdep_lock);
91 /* prevent any recursions within lockdep from causing deadlocks */
92 current->lockdep_recursion++;
96 static inline int graph_unlock(void)
98 if (debug_locks && !arch_spin_is_locked(&lockdep_lock))
99 return DEBUG_LOCKS_WARN_ON(1);
101 current->lockdep_recursion--;
102 arch_spin_unlock(&lockdep_lock);
107 * Turn lock debugging off and return with 0 if it was off already,
108 * and also release the graph lock:
110 static inline int debug_locks_off_graph_unlock(void)
112 int ret = debug_locks_off();
114 arch_spin_unlock(&lockdep_lock);
119 static int lockdep_initialized;
121 unsigned long nr_list_entries;
122 static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES];
125 * All data structures here are protected by the global debug_lock.
127 * Mutex key structs only get allocated, once during bootup, and never
128 * get freed - this significantly simplifies the debugging code.
130 unsigned long nr_lock_classes;
131 static struct lock_class lock_classes[MAX_LOCKDEP_KEYS];
133 static inline struct lock_class *hlock_class(struct held_lock *hlock)
135 if (!hlock->class_idx) {
136 DEBUG_LOCKS_WARN_ON(1);
139 return lock_classes + hlock->class_idx - 1;
142 #ifdef CONFIG_LOCK_STAT
143 static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS],
146 static inline u64 lockstat_clock(void)
148 return cpu_clock(smp_processor_id());
151 static int lock_point(unsigned long points[], unsigned long ip)
155 for (i = 0; i < LOCKSTAT_POINTS; i++) {
156 if (points[i] == 0) {
167 static void lock_time_inc(struct lock_time *lt, u64 time)
172 if (time < lt->min || !lt->nr)
179 static inline void lock_time_add(struct lock_time *src, struct lock_time *dst)
184 if (src->max > dst->max)
187 if (src->min < dst->min || !dst->nr)
190 dst->total += src->total;
194 struct lock_class_stats lock_stats(struct lock_class *class)
196 struct lock_class_stats stats;
199 memset(&stats, 0, sizeof(struct lock_class_stats));
200 for_each_possible_cpu(cpu) {
201 struct lock_class_stats *pcs =
202 &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
204 for (i = 0; i < ARRAY_SIZE(stats.contention_point); i++)
205 stats.contention_point[i] += pcs->contention_point[i];
207 for (i = 0; i < ARRAY_SIZE(stats.contending_point); i++)
208 stats.contending_point[i] += pcs->contending_point[i];
210 lock_time_add(&pcs->read_waittime, &stats.read_waittime);
211 lock_time_add(&pcs->write_waittime, &stats.write_waittime);
213 lock_time_add(&pcs->read_holdtime, &stats.read_holdtime);
214 lock_time_add(&pcs->write_holdtime, &stats.write_holdtime);
216 for (i = 0; i < ARRAY_SIZE(stats.bounces); i++)
217 stats.bounces[i] += pcs->bounces[i];
223 void clear_lock_stats(struct lock_class *class)
227 for_each_possible_cpu(cpu) {
228 struct lock_class_stats *cpu_stats =
229 &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
231 memset(cpu_stats, 0, sizeof(struct lock_class_stats));
233 memset(class->contention_point, 0, sizeof(class->contention_point));
234 memset(class->contending_point, 0, sizeof(class->contending_point));
237 static struct lock_class_stats *get_lock_stats(struct lock_class *class)
239 return &get_cpu_var(cpu_lock_stats)[class - lock_classes];
242 static void put_lock_stats(struct lock_class_stats *stats)
244 put_cpu_var(cpu_lock_stats);
247 static void lock_release_holdtime(struct held_lock *hlock)
249 struct lock_class_stats *stats;
255 holdtime = lockstat_clock() - hlock->holdtime_stamp;
257 stats = get_lock_stats(hlock_class(hlock));
259 lock_time_inc(&stats->read_holdtime, holdtime);
261 lock_time_inc(&stats->write_holdtime, holdtime);
262 put_lock_stats(stats);
265 static inline void lock_release_holdtime(struct held_lock *hlock)
271 * We keep a global list of all lock classes. The list only grows,
272 * never shrinks. The list is only accessed with the lockdep
273 * spinlock lock held.
275 LIST_HEAD(all_lock_classes);
278 * The lockdep classes are in a hash-table as well, for fast lookup:
280 #define CLASSHASH_BITS (MAX_LOCKDEP_KEYS_BITS - 1)
281 #define CLASSHASH_SIZE (1UL << CLASSHASH_BITS)
282 #define __classhashfn(key) hash_long((unsigned long)key, CLASSHASH_BITS)
283 #define classhashentry(key) (classhash_table + __classhashfn((key)))
285 static struct list_head classhash_table[CLASSHASH_SIZE];
288 * We put the lock dependency chains into a hash-table as well, to cache
291 #define CHAINHASH_BITS (MAX_LOCKDEP_CHAINS_BITS-1)
292 #define CHAINHASH_SIZE (1UL << CHAINHASH_BITS)
293 #define __chainhashfn(chain) hash_long(chain, CHAINHASH_BITS)
294 #define chainhashentry(chain) (chainhash_table + __chainhashfn((chain)))
296 static struct list_head chainhash_table[CHAINHASH_SIZE];
299 * The hash key of the lock dependency chains is a hash itself too:
300 * it's a hash of all locks taken up to that lock, including that lock.
301 * It's a 64-bit hash, because it's important for the keys to be
304 #define iterate_chain_key(key1, key2) \
305 (((key1) << MAX_LOCKDEP_KEYS_BITS) ^ \
306 ((key1) >> (64-MAX_LOCKDEP_KEYS_BITS)) ^ \
309 void lockdep_off(void)
311 current->lockdep_recursion++;
313 EXPORT_SYMBOL(lockdep_off);
315 void lockdep_on(void)
317 current->lockdep_recursion--;
319 EXPORT_SYMBOL(lockdep_on);
322 * Debugging switches:
326 #define VERY_VERBOSE 0
329 # define HARDIRQ_VERBOSE 1
330 # define SOFTIRQ_VERBOSE 1
331 # define RECLAIM_VERBOSE 1
333 # define HARDIRQ_VERBOSE 0
334 # define SOFTIRQ_VERBOSE 0
335 # define RECLAIM_VERBOSE 0
338 #if VERBOSE || HARDIRQ_VERBOSE || SOFTIRQ_VERBOSE || RECLAIM_VERBOSE
340 * Quick filtering for interesting events:
342 static int class_filter(struct lock_class *class)
346 if (class->name_version == 1 &&
347 !strcmp(class->name, "lockname"))
349 if (class->name_version == 1 &&
350 !strcmp(class->name, "&struct->lockfield"))
353 /* Filter everything else. 1 would be to allow everything else */
358 static int verbose(struct lock_class *class)
361 return class_filter(class);
367 * Stack-trace: tightly packed array of stack backtrace
368 * addresses. Protected by the graph_lock.
370 unsigned long nr_stack_trace_entries;
371 static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];
373 static int save_trace(struct stack_trace *trace)
375 trace->nr_entries = 0;
376 trace->max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries;
377 trace->entries = stack_trace + nr_stack_trace_entries;
381 save_stack_trace(trace);
384 * Some daft arches put -1 at the end to indicate its a full trace.
386 * <rant> this is buggy anyway, since it takes a whole extra entry so a
387 * complete trace that maxes out the entries provided will be reported
388 * as incomplete, friggin useless </rant>
390 if (trace->nr_entries != 0 &&
391 trace->entries[trace->nr_entries-1] == ULONG_MAX)
394 trace->max_entries = trace->nr_entries;
396 nr_stack_trace_entries += trace->nr_entries;
398 if (nr_stack_trace_entries >= MAX_STACK_TRACE_ENTRIES-1) {
399 if (!debug_locks_off_graph_unlock())
402 printk("BUG: MAX_STACK_TRACE_ENTRIES too low!\n");
403 printk("turning off the locking correctness validator.\n");
412 unsigned int nr_hardirq_chains;
413 unsigned int nr_softirq_chains;
414 unsigned int nr_process_chains;
415 unsigned int max_lockdep_depth;
417 #ifdef CONFIG_DEBUG_LOCKDEP
419 * We cannot printk in early bootup code. Not even early_printk()
420 * might work. So we mark any initialization errors and printk
421 * about it later on, in lockdep_info().
423 static int lockdep_init_error;
424 static unsigned long lockdep_init_trace_data[20];
425 static struct stack_trace lockdep_init_trace = {
426 .max_entries = ARRAY_SIZE(lockdep_init_trace_data),
427 .entries = lockdep_init_trace_data,
431 * Various lockdep statistics:
433 atomic_t chain_lookup_hits;
434 atomic_t chain_lookup_misses;
435 atomic_t hardirqs_on_events;
436 atomic_t hardirqs_off_events;
437 atomic_t redundant_hardirqs_on;
438 atomic_t redundant_hardirqs_off;
439 atomic_t softirqs_on_events;
440 atomic_t softirqs_off_events;
441 atomic_t redundant_softirqs_on;
442 atomic_t redundant_softirqs_off;
443 atomic_t nr_unused_locks;
444 atomic_t nr_cyclic_checks;
445 atomic_t nr_find_usage_forwards_checks;
446 atomic_t nr_find_usage_backwards_checks;
453 #define __USAGE(__STATE) \
454 [LOCK_USED_IN_##__STATE] = "IN-"__stringify(__STATE)"-W", \
455 [LOCK_ENABLED_##__STATE] = __stringify(__STATE)"-ON-W", \
456 [LOCK_USED_IN_##__STATE##_READ] = "IN-"__stringify(__STATE)"-R",\
457 [LOCK_ENABLED_##__STATE##_READ] = __stringify(__STATE)"-ON-R",
459 static const char *usage_str[] =
461 #define LOCKDEP_STATE(__STATE) __USAGE(__STATE)
462 #include "lockdep_states.h"
464 [LOCK_USED] = "INITIAL USE",
467 const char * __get_key_name(struct lockdep_subclass_key *key, char *str)
469 return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str);
472 static inline unsigned long lock_flag(enum lock_usage_bit bit)
477 static char get_usage_char(struct lock_class *class, enum lock_usage_bit bit)
481 if (class->usage_mask & lock_flag(bit + 2))
483 if (class->usage_mask & lock_flag(bit)) {
485 if (class->usage_mask & lock_flag(bit + 2))
492 void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS])
496 #define LOCKDEP_STATE(__STATE) \
497 usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE); \
498 usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE##_READ);
499 #include "lockdep_states.h"
505 static void print_lock_name(struct lock_class *class)
507 char str[KSYM_NAME_LEN], usage[LOCK_USAGE_CHARS];
510 get_usage_chars(class, usage);
514 name = __get_key_name(class->key, str);
515 printk(" (%s", name);
517 printk(" (%s", name);
518 if (class->name_version > 1)
519 printk("#%d", class->name_version);
521 printk("/%d", class->subclass);
523 printk("){%s}", usage);
526 static void print_lockdep_cache(struct lockdep_map *lock)
529 char str[KSYM_NAME_LEN];
533 name = __get_key_name(lock->key->subkeys, str);
538 static void print_lock(struct held_lock *hlock)
540 print_lock_name(hlock_class(hlock));
542 print_ip_sym(hlock->acquire_ip);
545 static void lockdep_print_held_locks(struct task_struct *curr)
547 int i, depth = curr->lockdep_depth;
550 printk("no locks held by %s/%d.\n", curr->comm, task_pid_nr(curr));
553 printk("%d lock%s held by %s/%d:\n",
554 depth, depth > 1 ? "s" : "", curr->comm, task_pid_nr(curr));
556 for (i = 0; i < depth; i++) {
558 print_lock(curr->held_locks + i);
562 static void print_kernel_version(void)
564 printk("%s %.*s\n", init_utsname()->release,
565 (int)strcspn(init_utsname()->version, " "),
566 init_utsname()->version);
569 static int very_verbose(struct lock_class *class)
572 return class_filter(class);
578 * Is this the address of a static object:
580 static int static_obj(void *obj)
582 unsigned long start = (unsigned long) &_stext,
583 end = (unsigned long) &_end,
584 addr = (unsigned long) obj;
589 if ((addr >= start) && (addr < end))
592 if (arch_is_kernel_data(addr))
596 * in-kernel percpu var?
598 if (is_kernel_percpu_address(addr))
602 * module static or percpu var?
604 return is_module_address(addr) || is_module_percpu_address(addr);
608 * To make lock name printouts unique, we calculate a unique
609 * class->name_version generation counter:
611 static int count_matching_names(struct lock_class *new_class)
613 struct lock_class *class;
616 if (!new_class->name)
619 list_for_each_entry(class, &all_lock_classes, lock_entry) {
620 if (new_class->key - new_class->subclass == class->key)
621 return class->name_version;
622 if (class->name && !strcmp(class->name, new_class->name))
623 count = max(count, class->name_version);
630 * Register a lock's class in the hash-table, if the class is not present
631 * yet. Otherwise we look it up. We cache the result in the lock object
632 * itself, so actual lookup of the hash should be once per lock object.
634 static inline struct lock_class *
635 look_up_lock_class(struct lockdep_map *lock, unsigned int subclass)
637 struct lockdep_subclass_key *key;
638 struct list_head *hash_head;
639 struct lock_class *class;
641 #ifdef CONFIG_DEBUG_LOCKDEP
643 * If the architecture calls into lockdep before initializing
644 * the hashes then we'll warn about it later. (we cannot printk
647 if (unlikely(!lockdep_initialized)) {
649 lockdep_init_error = 1;
650 save_stack_trace(&lockdep_init_trace);
655 * Static locks do not have their class-keys yet - for them the key
656 * is the lock object itself:
658 if (unlikely(!lock->key))
659 lock->key = (void *)lock;
662 * NOTE: the class-key must be unique. For dynamic locks, a static
663 * lock_class_key variable is passed in through the mutex_init()
664 * (or spin_lock_init()) call - which acts as the key. For static
665 * locks we use the lock object itself as the key.
667 BUILD_BUG_ON(sizeof(struct lock_class_key) >
668 sizeof(struct lockdep_map));
670 key = lock->key->subkeys + subclass;
672 hash_head = classhashentry(key);
675 * We can walk the hash lockfree, because the hash only
676 * grows, and we are careful when adding entries to the end:
678 list_for_each_entry(class, hash_head, hash_entry) {
679 if (class->key == key) {
680 WARN_ON_ONCE(class->name != lock->name);
689 * Register a lock's class in the hash-table, if the class is not present
690 * yet. Otherwise we look it up. We cache the result in the lock object
691 * itself, so actual lookup of the hash should be once per lock object.
693 static inline struct lock_class *
694 register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
696 struct lockdep_subclass_key *key;
697 struct list_head *hash_head;
698 struct lock_class *class;
701 class = look_up_lock_class(lock, subclass);
706 * Debug-check: all keys must be persistent!
708 if (!static_obj(lock->key)) {
710 printk("INFO: trying to register non-static key.\n");
711 printk("the code is fine but needs lockdep annotation.\n");
712 printk("turning off the locking correctness validator.\n");
718 key = lock->key->subkeys + subclass;
719 hash_head = classhashentry(key);
721 raw_local_irq_save(flags);
723 raw_local_irq_restore(flags);
727 * We have to do the hash-walk again, to avoid races
730 list_for_each_entry(class, hash_head, hash_entry)
731 if (class->key == key)
734 * Allocate a new key from the static array, and add it to
737 if (nr_lock_classes >= MAX_LOCKDEP_KEYS) {
738 if (!debug_locks_off_graph_unlock()) {
739 raw_local_irq_restore(flags);
742 raw_local_irq_restore(flags);
744 printk("BUG: MAX_LOCKDEP_KEYS too low!\n");
745 printk("turning off the locking correctness validator.\n");
749 class = lock_classes + nr_lock_classes++;
750 debug_atomic_inc(&nr_unused_locks);
752 class->name = lock->name;
753 class->subclass = subclass;
754 INIT_LIST_HEAD(&class->lock_entry);
755 INIT_LIST_HEAD(&class->locks_before);
756 INIT_LIST_HEAD(&class->locks_after);
757 class->name_version = count_matching_names(class);
759 * We use RCU's safe list-add method to make
760 * parallel walking of the hash-list safe:
762 list_add_tail_rcu(&class->hash_entry, hash_head);
764 * Add it to the global list of classes:
766 list_add_tail_rcu(&class->lock_entry, &all_lock_classes);
768 if (verbose(class)) {
770 raw_local_irq_restore(flags);
772 printk("\nnew class %p: %s", class->key, class->name);
773 if (class->name_version > 1)
774 printk("#%d", class->name_version);
778 raw_local_irq_save(flags);
780 raw_local_irq_restore(flags);
786 raw_local_irq_restore(flags);
788 if (!subclass || force)
789 lock->class_cache = class;
791 if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))
797 #ifdef CONFIG_PROVE_LOCKING
799 * Allocate a lockdep entry. (assumes the graph_lock held, returns
800 * with NULL on failure)
802 static struct lock_list *alloc_list_entry(void)
804 if (nr_list_entries >= MAX_LOCKDEP_ENTRIES) {
805 if (!debug_locks_off_graph_unlock())
808 printk("BUG: MAX_LOCKDEP_ENTRIES too low!\n");
809 printk("turning off the locking correctness validator.\n");
813 return list_entries + nr_list_entries++;
817 * Add a new dependency to the head of the list:
819 static int add_lock_to_list(struct lock_class *class, struct lock_class *this,
820 struct list_head *head, unsigned long ip, int distance)
822 struct lock_list *entry;
824 * Lock not present yet - get a new dependency struct and
825 * add it to the list:
827 entry = alloc_list_entry();
831 if (!save_trace(&entry->trace))
835 entry->distance = distance;
837 * Since we never remove from the dependency list, the list can
838 * be walked lockless by other CPUs, it's only allocation
839 * that must be protected by the spinlock. But this also means
840 * we must make new entries visible only once writes to the
841 * entry become visible - hence the RCU op:
843 list_add_tail_rcu(&entry->entry, head);
849 * For good efficiency of modular, we use power of 2
851 #define MAX_CIRCULAR_QUEUE_SIZE 4096UL
852 #define CQ_MASK (MAX_CIRCULAR_QUEUE_SIZE-1)
855 * The circular_queue and helpers is used to implement the
856 * breadth-first search(BFS)algorithem, by which we can build
857 * the shortest path from the next lock to be acquired to the
858 * previous held lock if there is a circular between them.
860 struct circular_queue {
861 unsigned long element[MAX_CIRCULAR_QUEUE_SIZE];
862 unsigned int front, rear;
865 static struct circular_queue lock_cq;
867 unsigned int max_bfs_queue_depth;
869 static unsigned int lockdep_dependency_gen_id;
871 static inline void __cq_init(struct circular_queue *cq)
873 cq->front = cq->rear = 0;
874 lockdep_dependency_gen_id++;
877 static inline int __cq_empty(struct circular_queue *cq)
879 return (cq->front == cq->rear);
882 static inline int __cq_full(struct circular_queue *cq)
884 return ((cq->rear + 1) & CQ_MASK) == cq->front;
887 static inline int __cq_enqueue(struct circular_queue *cq, unsigned long elem)
892 cq->element[cq->rear] = elem;
893 cq->rear = (cq->rear + 1) & CQ_MASK;
897 static inline int __cq_dequeue(struct circular_queue *cq, unsigned long *elem)
902 *elem = cq->element[cq->front];
903 cq->front = (cq->front + 1) & CQ_MASK;
907 static inline unsigned int __cq_get_elem_count(struct circular_queue *cq)
909 return (cq->rear - cq->front) & CQ_MASK;
912 static inline void mark_lock_accessed(struct lock_list *lock,
913 struct lock_list *parent)
917 nr = lock - list_entries;
918 WARN_ON(nr >= nr_list_entries);
919 lock->parent = parent;
920 lock->class->dep_gen_id = lockdep_dependency_gen_id;
923 static inline unsigned long lock_accessed(struct lock_list *lock)
927 nr = lock - list_entries;
928 WARN_ON(nr >= nr_list_entries);
929 return lock->class->dep_gen_id == lockdep_dependency_gen_id;
932 static inline struct lock_list *get_lock_parent(struct lock_list *child)
934 return child->parent;
937 static inline int get_lock_depth(struct lock_list *child)
940 struct lock_list *parent;
942 while ((parent = get_lock_parent(child))) {
949 static int __bfs(struct lock_list *source_entry,
951 int (*match)(struct lock_list *entry, void *data),
952 struct lock_list **target_entry,
955 struct lock_list *entry;
956 struct list_head *head;
957 struct circular_queue *cq = &lock_cq;
960 if (match(source_entry, data)) {
961 *target_entry = source_entry;
967 head = &source_entry->class->locks_after;
969 head = &source_entry->class->locks_before;
971 if (list_empty(head))
975 __cq_enqueue(cq, (unsigned long)source_entry);
977 while (!__cq_empty(cq)) {
978 struct lock_list *lock;
980 __cq_dequeue(cq, (unsigned long *)&lock);
988 head = &lock->class->locks_after;
990 head = &lock->class->locks_before;
992 list_for_each_entry(entry, head, entry) {
993 if (!lock_accessed(entry)) {
994 unsigned int cq_depth;
995 mark_lock_accessed(entry, lock);
996 if (match(entry, data)) {
997 *target_entry = entry;
1002 if (__cq_enqueue(cq, (unsigned long)entry)) {
1006 cq_depth = __cq_get_elem_count(cq);
1007 if (max_bfs_queue_depth < cq_depth)
1008 max_bfs_queue_depth = cq_depth;
1016 static inline int __bfs_forwards(struct lock_list *src_entry,
1018 int (*match)(struct lock_list *entry, void *data),
1019 struct lock_list **target_entry)
1021 return __bfs(src_entry, data, match, target_entry, 1);
1025 static inline int __bfs_backwards(struct lock_list *src_entry,
1027 int (*match)(struct lock_list *entry, void *data),
1028 struct lock_list **target_entry)
1030 return __bfs(src_entry, data, match, target_entry, 0);
1035 * Recursive, forwards-direction lock-dependency checking, used for
1036 * both noncyclic checking and for hardirq-unsafe/softirq-unsafe
1041 * Print a dependency chain entry (this is only done when a deadlock
1042 * has been detected):
1045 print_circular_bug_entry(struct lock_list *target, int depth)
1047 if (debug_locks_silent)
1049 printk("\n-> #%u", depth);
1050 print_lock_name(target->class);
1052 print_stack_trace(&target->trace, 6);
1058 * When a circular dependency is detected, print the
1062 print_circular_bug_header(struct lock_list *entry, unsigned int depth,
1063 struct held_lock *check_src,
1064 struct held_lock *check_tgt)
1066 struct task_struct *curr = current;
1068 if (debug_locks_silent)
1071 printk("\n=======================================================\n");
1072 printk( "[ INFO: possible circular locking dependency detected ]\n");
1073 print_kernel_version();
1074 printk( "-------------------------------------------------------\n");
1075 printk("%s/%d is trying to acquire lock:\n",
1076 curr->comm, task_pid_nr(curr));
1077 print_lock(check_src);
1078 printk("\nbut task is already holding lock:\n");
1079 print_lock(check_tgt);
1080 printk("\nwhich lock already depends on the new lock.\n\n");
1081 printk("\nthe existing dependency chain (in reverse order) is:\n");
1083 print_circular_bug_entry(entry, depth);
1088 static inline int class_equal(struct lock_list *entry, void *data)
1090 return entry->class == data;
1093 static noinline int print_circular_bug(struct lock_list *this,
1094 struct lock_list *target,
1095 struct held_lock *check_src,
1096 struct held_lock *check_tgt)
1098 struct task_struct *curr = current;
1099 struct lock_list *parent;
1102 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1105 if (!save_trace(&this->trace))
1108 depth = get_lock_depth(target);
1110 print_circular_bug_header(target, depth, check_src, check_tgt);
1112 parent = get_lock_parent(target);
1115 print_circular_bug_entry(parent, --depth);
1116 parent = get_lock_parent(parent);
1119 printk("\nother info that might help us debug this:\n\n");
1120 lockdep_print_held_locks(curr);
1122 printk("\nstack backtrace:\n");
1128 static noinline int print_bfs_bug(int ret)
1130 if (!debug_locks_off_graph_unlock())
1133 WARN(1, "lockdep bfs error:%d\n", ret);
1138 static int noop_count(struct lock_list *entry, void *data)
1140 (*(unsigned long *)data)++;
1144 unsigned long __lockdep_count_forward_deps(struct lock_list *this)
1146 unsigned long count = 0;
1147 struct lock_list *uninitialized_var(target_entry);
1149 __bfs_forwards(this, (void *)&count, noop_count, &target_entry);
1153 unsigned long lockdep_count_forward_deps(struct lock_class *class)
1155 unsigned long ret, flags;
1156 struct lock_list this;
1161 local_irq_save(flags);
1162 arch_spin_lock(&lockdep_lock);
1163 ret = __lockdep_count_forward_deps(&this);
1164 arch_spin_unlock(&lockdep_lock);
1165 local_irq_restore(flags);
1170 unsigned long __lockdep_count_backward_deps(struct lock_list *this)
1172 unsigned long count = 0;
1173 struct lock_list *uninitialized_var(target_entry);
1175 __bfs_backwards(this, (void *)&count, noop_count, &target_entry);
1180 unsigned long lockdep_count_backward_deps(struct lock_class *class)
1182 unsigned long ret, flags;
1183 struct lock_list this;
1188 local_irq_save(flags);
1189 arch_spin_lock(&lockdep_lock);
1190 ret = __lockdep_count_backward_deps(&this);
1191 arch_spin_unlock(&lockdep_lock);
1192 local_irq_restore(flags);
1198 * Prove that the dependency graph starting at <entry> can not
1199 * lead to <target>. Print an error and return 0 if it does.
1202 check_noncircular(struct lock_list *root, struct lock_class *target,
1203 struct lock_list **target_entry)
1207 debug_atomic_inc(&nr_cyclic_checks);
1209 result = __bfs_forwards(root, target, class_equal, target_entry);
1214 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
1216 * Forwards and backwards subgraph searching, for the purposes of
1217 * proving that two subgraphs can be connected by a new dependency
1218 * without creating any illegal irq-safe -> irq-unsafe lock dependency.
1221 static inline int usage_match(struct lock_list *entry, void *bit)
1223 return entry->class->usage_mask & (1 << (enum lock_usage_bit)bit);
1229 * Find a node in the forwards-direction dependency sub-graph starting
1230 * at @root->class that matches @bit.
1232 * Return 0 if such a node exists in the subgraph, and put that node
1233 * into *@target_entry.
1235 * Return 1 otherwise and keep *@target_entry unchanged.
1236 * Return <0 on error.
1239 find_usage_forwards(struct lock_list *root, enum lock_usage_bit bit,
1240 struct lock_list **target_entry)
1244 debug_atomic_inc(&nr_find_usage_forwards_checks);
1246 result = __bfs_forwards(root, (void *)bit, usage_match, target_entry);
1252 * Find a node in the backwards-direction dependency sub-graph starting
1253 * at @root->class that matches @bit.
1255 * Return 0 if such a node exists in the subgraph, and put that node
1256 * into *@target_entry.
1258 * Return 1 otherwise and keep *@target_entry unchanged.
1259 * Return <0 on error.
1262 find_usage_backwards(struct lock_list *root, enum lock_usage_bit bit,
1263 struct lock_list **target_entry)
1267 debug_atomic_inc(&nr_find_usage_backwards_checks);
1269 result = __bfs_backwards(root, (void *)bit, usage_match, target_entry);
1274 static void print_lock_class_header(struct lock_class *class, int depth)
1278 printk("%*s->", depth, "");
1279 print_lock_name(class);
1280 printk(" ops: %lu", class->ops);
1283 for (bit = 0; bit < LOCK_USAGE_STATES; bit++) {
1284 if (class->usage_mask & (1 << bit)) {
1287 len += printk("%*s %s", depth, "", usage_str[bit]);
1288 len += printk(" at:\n");
1289 print_stack_trace(class->usage_traces + bit, len);
1292 printk("%*s }\n", depth, "");
1294 printk("%*s ... key at: ",depth,"");
1295 print_ip_sym((unsigned long)class->key);
1299 * printk the shortest lock dependencies from @start to @end in reverse order:
1302 print_shortest_lock_dependencies(struct lock_list *leaf,
1303 struct lock_list *root)
1305 struct lock_list *entry = leaf;
1308 /*compute depth from generated tree by BFS*/
1309 depth = get_lock_depth(leaf);
1312 print_lock_class_header(entry->class, depth);
1313 printk("%*s ... acquired at:\n", depth, "");
1314 print_stack_trace(&entry->trace, 2);
1317 if (depth == 0 && (entry != root)) {
1318 printk("lockdep:%s bad BFS generated tree\n", __func__);
1322 entry = get_lock_parent(entry);
1324 } while (entry && (depth >= 0));
1330 print_bad_irq_dependency(struct task_struct *curr,
1331 struct lock_list *prev_root,
1332 struct lock_list *next_root,
1333 struct lock_list *backwards_entry,
1334 struct lock_list *forwards_entry,
1335 struct held_lock *prev,
1336 struct held_lock *next,
1337 enum lock_usage_bit bit1,
1338 enum lock_usage_bit bit2,
1339 const char *irqclass)
1341 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1344 printk("\n======================================================\n");
1345 printk( "[ INFO: %s-safe -> %s-unsafe lock order detected ]\n",
1346 irqclass, irqclass);
1347 print_kernel_version();
1348 printk( "------------------------------------------------------\n");
1349 printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
1350 curr->comm, task_pid_nr(curr),
1351 curr->hardirq_context, hardirq_count() >> HARDIRQ_SHIFT,
1352 curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT,
1353 curr->hardirqs_enabled,
1354 curr->softirqs_enabled);
1357 printk("\nand this task is already holding:\n");
1359 printk("which would create a new lock dependency:\n");
1360 print_lock_name(hlock_class(prev));
1362 print_lock_name(hlock_class(next));
1365 printk("\nbut this new dependency connects a %s-irq-safe lock:\n",
1367 print_lock_name(backwards_entry->class);
1368 printk("\n... which became %s-irq-safe at:\n", irqclass);
1370 print_stack_trace(backwards_entry->class->usage_traces + bit1, 1);
1372 printk("\nto a %s-irq-unsafe lock:\n", irqclass);
1373 print_lock_name(forwards_entry->class);
1374 printk("\n... which became %s-irq-unsafe at:\n", irqclass);
1377 print_stack_trace(forwards_entry->class->usage_traces + bit2, 1);
1379 printk("\nother info that might help us debug this:\n\n");
1380 lockdep_print_held_locks(curr);
1382 printk("\nthe dependencies between %s-irq-safe lock", irqclass);
1383 printk(" and the holding lock:\n");
1384 if (!save_trace(&prev_root->trace))
1386 print_shortest_lock_dependencies(backwards_entry, prev_root);
1388 printk("\nthe dependencies between the lock to be acquired");
1389 printk(" and %s-irq-unsafe lock:\n", irqclass);
1390 if (!save_trace(&next_root->trace))
1392 print_shortest_lock_dependencies(forwards_entry, next_root);
1394 printk("\nstack backtrace:\n");
1401 check_usage(struct task_struct *curr, struct held_lock *prev,
1402 struct held_lock *next, enum lock_usage_bit bit_backwards,
1403 enum lock_usage_bit bit_forwards, const char *irqclass)
1406 struct lock_list this, that;
1407 struct lock_list *uninitialized_var(target_entry);
1408 struct lock_list *uninitialized_var(target_entry1);
1412 this.class = hlock_class(prev);
1413 ret = find_usage_backwards(&this, bit_backwards, &target_entry);
1415 return print_bfs_bug(ret);
1420 that.class = hlock_class(next);
1421 ret = find_usage_forwards(&that, bit_forwards, &target_entry1);
1423 return print_bfs_bug(ret);
1427 return print_bad_irq_dependency(curr, &this, &that,
1428 target_entry, target_entry1,
1430 bit_backwards, bit_forwards, irqclass);
1433 static const char *state_names[] = {
1434 #define LOCKDEP_STATE(__STATE) \
1435 __stringify(__STATE),
1436 #include "lockdep_states.h"
1437 #undef LOCKDEP_STATE
1440 static const char *state_rnames[] = {
1441 #define LOCKDEP_STATE(__STATE) \
1442 __stringify(__STATE)"-READ",
1443 #include "lockdep_states.h"
1444 #undef LOCKDEP_STATE
1447 static inline const char *state_name(enum lock_usage_bit bit)
1449 return (bit & 1) ? state_rnames[bit >> 2] : state_names[bit >> 2];
1452 static int exclusive_bit(int new_bit)
1460 * bit 0 - write/read
1461 * bit 1 - used_in/enabled
1465 int state = new_bit & ~3;
1466 int dir = new_bit & 2;
1469 * keep state, bit flip the direction and strip read.
1471 return state | (dir ^ 2);
1474 static int check_irq_usage(struct task_struct *curr, struct held_lock *prev,
1475 struct held_lock *next, enum lock_usage_bit bit)
1478 * Prove that the new dependency does not connect a hardirq-safe
1479 * lock with a hardirq-unsafe lock - to achieve this we search
1480 * the backwards-subgraph starting at <prev>, and the
1481 * forwards-subgraph starting at <next>:
1483 if (!check_usage(curr, prev, next, bit,
1484 exclusive_bit(bit), state_name(bit)))
1490 * Prove that the new dependency does not connect a hardirq-safe-read
1491 * lock with a hardirq-unsafe lock - to achieve this we search
1492 * the backwards-subgraph starting at <prev>, and the
1493 * forwards-subgraph starting at <next>:
1495 if (!check_usage(curr, prev, next, bit,
1496 exclusive_bit(bit), state_name(bit)))
1503 check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
1504 struct held_lock *next)
1506 #define LOCKDEP_STATE(__STATE) \
1507 if (!check_irq_usage(curr, prev, next, LOCK_USED_IN_##__STATE)) \
1509 #include "lockdep_states.h"
1510 #undef LOCKDEP_STATE
1515 static void inc_chains(void)
1517 if (current->hardirq_context)
1518 nr_hardirq_chains++;
1520 if (current->softirq_context)
1521 nr_softirq_chains++;
1523 nr_process_chains++;
1530 check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
1531 struct held_lock *next)
1536 static inline void inc_chains(void)
1538 nr_process_chains++;
1544 print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
1545 struct held_lock *next)
1547 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1550 printk("\n=============================================\n");
1551 printk( "[ INFO: possible recursive locking detected ]\n");
1552 print_kernel_version();
1553 printk( "---------------------------------------------\n");
1554 printk("%s/%d is trying to acquire lock:\n",
1555 curr->comm, task_pid_nr(curr));
1557 printk("\nbut task is already holding lock:\n");
1560 printk("\nother info that might help us debug this:\n");
1561 lockdep_print_held_locks(curr);
1563 printk("\nstack backtrace:\n");
1570 * Check whether we are holding such a class already.
1572 * (Note that this has to be done separately, because the graph cannot
1573 * detect such classes of deadlocks.)
1575 * Returns: 0 on deadlock detected, 1 on OK, 2 on recursive read
1578 check_deadlock(struct task_struct *curr, struct held_lock *next,
1579 struct lockdep_map *next_instance, int read)
1581 struct held_lock *prev;
1582 struct held_lock *nest = NULL;
1585 for (i = 0; i < curr->lockdep_depth; i++) {
1586 prev = curr->held_locks + i;
1588 if (prev->instance == next->nest_lock)
1591 if (hlock_class(prev) != hlock_class(next))
1595 * Allow read-after-read recursion of the same
1596 * lock class (i.e. read_lock(lock)+read_lock(lock)):
1598 if ((read == 2) && prev->read)
1602 * We're holding the nest_lock, which serializes this lock's
1603 * nesting behaviour.
1608 return print_deadlock_bug(curr, prev, next);
1614 * There was a chain-cache miss, and we are about to add a new dependency
1615 * to a previous lock. We recursively validate the following rules:
1617 * - would the adding of the <prev> -> <next> dependency create a
1618 * circular dependency in the graph? [== circular deadlock]
1620 * - does the new prev->next dependency connect any hardirq-safe lock
1621 * (in the full backwards-subgraph starting at <prev>) with any
1622 * hardirq-unsafe lock (in the full forwards-subgraph starting at
1623 * <next>)? [== illegal lock inversion with hardirq contexts]
1625 * - does the new prev->next dependency connect any softirq-safe lock
1626 * (in the full backwards-subgraph starting at <prev>) with any
1627 * softirq-unsafe lock (in the full forwards-subgraph starting at
1628 * <next>)? [== illegal lock inversion with softirq contexts]
1630 * any of these scenarios could lead to a deadlock.
1632 * Then if all the validations pass, we add the forwards and backwards
1636 check_prev_add(struct task_struct *curr, struct held_lock *prev,
1637 struct held_lock *next, int distance)
1639 struct lock_list *entry;
1641 struct lock_list this;
1642 struct lock_list *uninitialized_var(target_entry);
1645 * Prove that the new <prev> -> <next> dependency would not
1646 * create a circular dependency in the graph. (We do this by
1647 * forward-recursing into the graph starting at <next>, and
1648 * checking whether we can reach <prev>.)
1650 * We are using global variables to control the recursion, to
1651 * keep the stackframe size of the recursive functions low:
1653 this.class = hlock_class(next);
1655 ret = check_noncircular(&this, hlock_class(prev), &target_entry);
1657 return print_circular_bug(&this, target_entry, next, prev);
1658 else if (unlikely(ret < 0))
1659 return print_bfs_bug(ret);
1661 if (!check_prev_add_irq(curr, prev, next))
1665 * For recursive read-locks we do all the dependency checks,
1666 * but we dont store read-triggered dependencies (only
1667 * write-triggered dependencies). This ensures that only the
1668 * write-side dependencies matter, and that if for example a
1669 * write-lock never takes any other locks, then the reads are
1670 * equivalent to a NOP.
1672 if (next->read == 2 || prev->read == 2)
1675 * Is the <prev> -> <next> dependency already present?
1677 * (this may occur even though this is a new chain: consider
1678 * e.g. the L1 -> L2 -> L3 -> L4 and the L5 -> L1 -> L2 -> L3
1679 * chains - the second one will be new, but L1 already has
1680 * L2 added to its dependency list, due to the first chain.)
1682 list_for_each_entry(entry, &hlock_class(prev)->locks_after, entry) {
1683 if (entry->class == hlock_class(next)) {
1685 entry->distance = 1;
1691 * Ok, all validations passed, add the new lock
1692 * to the previous lock's dependency list:
1694 ret = add_lock_to_list(hlock_class(prev), hlock_class(next),
1695 &hlock_class(prev)->locks_after,
1696 next->acquire_ip, distance);
1701 ret = add_lock_to_list(hlock_class(next), hlock_class(prev),
1702 &hlock_class(next)->locks_before,
1703 next->acquire_ip, distance);
1708 * Debugging printouts:
1710 if (verbose(hlock_class(prev)) || verbose(hlock_class(next))) {
1712 printk("\n new dependency: ");
1713 print_lock_name(hlock_class(prev));
1715 print_lock_name(hlock_class(next));
1718 return graph_lock();
1724 * Add the dependency to all directly-previous locks that are 'relevant'.
1725 * The ones that are relevant are (in increasing distance from curr):
1726 * all consecutive trylock entries and the final non-trylock entry - or
1727 * the end of this context's lock-chain - whichever comes first.
1730 check_prevs_add(struct task_struct *curr, struct held_lock *next)
1732 int depth = curr->lockdep_depth;
1733 struct held_lock *hlock;
1738 * Depth must not be zero for a non-head lock:
1743 * At least two relevant locks must exist for this
1746 if (curr->held_locks[depth].irq_context !=
1747 curr->held_locks[depth-1].irq_context)
1751 int distance = curr->lockdep_depth - depth + 1;
1752 hlock = curr->held_locks + depth-1;
1754 * Only non-recursive-read entries get new dependencies
1757 if (hlock->read != 2) {
1758 if (!check_prev_add(curr, hlock, next, distance))
1761 * Stop after the first non-trylock entry,
1762 * as non-trylock entries have added their
1763 * own direct dependencies already, so this
1764 * lock is connected to them indirectly:
1766 if (!hlock->trylock)
1771 * End of lock-stack?
1776 * Stop the search if we cross into another context:
1778 if (curr->held_locks[depth].irq_context !=
1779 curr->held_locks[depth-1].irq_context)
1784 if (!debug_locks_off_graph_unlock())
1792 unsigned long nr_lock_chains;
1793 struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
1794 int nr_chain_hlocks;
1795 static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
1797 struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
1799 return lock_classes + chain_hlocks[chain->base + i];
1803 * Look up a dependency chain. If the key is not present yet then
1804 * add it and return 1 - in this case the new dependency chain is
1805 * validated. If the key is already hashed, return 0.
1806 * (On return with 1 graph_lock is held.)
1808 static inline int lookup_chain_cache(struct task_struct *curr,
1809 struct held_lock *hlock,
1812 struct lock_class *class = hlock_class(hlock);
1813 struct list_head *hash_head = chainhashentry(chain_key);
1814 struct lock_chain *chain;
1815 struct held_lock *hlock_curr, *hlock_next;
1818 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
1821 * We can walk it lock-free, because entries only get added
1824 list_for_each_entry(chain, hash_head, entry) {
1825 if (chain->chain_key == chain_key) {
1827 debug_atomic_inc(&chain_lookup_hits);
1828 if (very_verbose(class))
1829 printk("\nhash chain already cached, key: "
1830 "%016Lx tail class: [%p] %s\n",
1831 (unsigned long long)chain_key,
1832 class->key, class->name);
1836 if (very_verbose(class))
1837 printk("\nnew hash chain, key: %016Lx tail class: [%p] %s\n",
1838 (unsigned long long)chain_key, class->key, class->name);
1840 * Allocate a new chain entry from the static array, and add
1846 * We have to walk the chain again locked - to avoid duplicates:
1848 list_for_each_entry(chain, hash_head, entry) {
1849 if (chain->chain_key == chain_key) {
1854 if (unlikely(nr_lock_chains >= MAX_LOCKDEP_CHAINS)) {
1855 if (!debug_locks_off_graph_unlock())
1858 printk("BUG: MAX_LOCKDEP_CHAINS too low!\n");
1859 printk("turning off the locking correctness validator.\n");
1863 chain = lock_chains + nr_lock_chains++;
1864 chain->chain_key = chain_key;
1865 chain->irq_context = hlock->irq_context;
1866 /* Find the first held_lock of current chain */
1868 for (i = curr->lockdep_depth - 1; i >= 0; i--) {
1869 hlock_curr = curr->held_locks + i;
1870 if (hlock_curr->irq_context != hlock_next->irq_context)
1875 chain->depth = curr->lockdep_depth + 1 - i;
1876 cn = nr_chain_hlocks;
1877 while (cn + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS) {
1878 n = cmpxchg(&nr_chain_hlocks, cn, cn + chain->depth);
1883 if (likely(cn + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) {
1885 for (j = 0; j < chain->depth - 1; j++, i++) {
1886 int lock_id = curr->held_locks[i].class_idx - 1;
1887 chain_hlocks[chain->base + j] = lock_id;
1889 chain_hlocks[chain->base + j] = class - lock_classes;
1891 list_add_tail_rcu(&chain->entry, hash_head);
1892 debug_atomic_inc(&chain_lookup_misses);
1898 static int validate_chain(struct task_struct *curr, struct lockdep_map *lock,
1899 struct held_lock *hlock, int chain_head, u64 chain_key)
1902 * Trylock needs to maintain the stack of held locks, but it
1903 * does not add new dependencies, because trylock can be done
1906 * We look up the chain_key and do the O(N^2) check and update of
1907 * the dependencies only if this is a new dependency chain.
1908 * (If lookup_chain_cache() returns with 1 it acquires
1909 * graph_lock for us)
1911 if (!hlock->trylock && (hlock->check == 2) &&
1912 lookup_chain_cache(curr, hlock, chain_key)) {
1914 * Check whether last held lock:
1916 * - is irq-safe, if this lock is irq-unsafe
1917 * - is softirq-safe, if this lock is hardirq-unsafe
1919 * And check whether the new lock's dependency graph
1920 * could lead back to the previous lock.
1922 * any of these scenarios could lead to a deadlock. If
1925 int ret = check_deadlock(curr, hlock, lock, hlock->read);
1930 * Mark recursive read, as we jump over it when
1931 * building dependencies (just like we jump over
1937 * Add dependency only if this lock is not the head
1938 * of the chain, and if it's not a secondary read-lock:
1940 if (!chain_head && ret != 2)
1941 if (!check_prevs_add(curr, hlock))
1945 /* after lookup_chain_cache(): */
1946 if (unlikely(!debug_locks))
1952 static inline int validate_chain(struct task_struct *curr,
1953 struct lockdep_map *lock, struct held_lock *hlock,
1954 int chain_head, u64 chain_key)
1961 * We are building curr_chain_key incrementally, so double-check
1962 * it from scratch, to make sure that it's done correctly:
1964 static void check_chain_key(struct task_struct *curr)
1966 #ifdef CONFIG_DEBUG_LOCKDEP
1967 struct held_lock *hlock, *prev_hlock = NULL;
1971 for (i = 0; i < curr->lockdep_depth; i++) {
1972 hlock = curr->held_locks + i;
1973 if (chain_key != hlock->prev_chain_key) {
1975 WARN(1, "hm#1, depth: %u [%u], %016Lx != %016Lx\n",
1976 curr->lockdep_depth, i,
1977 (unsigned long long)chain_key,
1978 (unsigned long long)hlock->prev_chain_key);
1981 id = hlock->class_idx - 1;
1982 if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
1985 if (prev_hlock && (prev_hlock->irq_context !=
1986 hlock->irq_context))
1988 chain_key = iterate_chain_key(chain_key, id);
1991 if (chain_key != curr->curr_chain_key) {
1993 WARN(1, "hm#2, depth: %u [%u], %016Lx != %016Lx\n",
1994 curr->lockdep_depth, i,
1995 (unsigned long long)chain_key,
1996 (unsigned long long)curr->curr_chain_key);
2002 print_usage_bug(struct task_struct *curr, struct held_lock *this,
2003 enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
2005 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2008 printk("\n=================================\n");
2009 printk( "[ INFO: inconsistent lock state ]\n");
2010 print_kernel_version();
2011 printk( "---------------------------------\n");
2013 printk("inconsistent {%s} -> {%s} usage.\n",
2014 usage_str[prev_bit], usage_str[new_bit]);
2016 printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] takes:\n",
2017 curr->comm, task_pid_nr(curr),
2018 trace_hardirq_context(curr), hardirq_count() >> HARDIRQ_SHIFT,
2019 trace_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT,
2020 trace_hardirqs_enabled(curr),
2021 trace_softirqs_enabled(curr));
2024 printk("{%s} state was registered at:\n", usage_str[prev_bit]);
2025 print_stack_trace(hlock_class(this)->usage_traces + prev_bit, 1);
2027 print_irqtrace_events(curr);
2028 printk("\nother info that might help us debug this:\n");
2029 lockdep_print_held_locks(curr);
2031 printk("\nstack backtrace:\n");
2038 * Print out an error if an invalid bit is set:
2041 valid_state(struct task_struct *curr, struct held_lock *this,
2042 enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit)
2044 if (unlikely(hlock_class(this)->usage_mask & (1 << bad_bit)))
2045 return print_usage_bug(curr, this, bad_bit, new_bit);
2049 static int mark_lock(struct task_struct *curr, struct held_lock *this,
2050 enum lock_usage_bit new_bit);
2052 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
2055 * print irq inversion bug:
2058 print_irq_inversion_bug(struct task_struct *curr,
2059 struct lock_list *root, struct lock_list *other,
2060 struct held_lock *this, int forwards,
2061 const char *irqclass)
2063 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2066 printk("\n=========================================================\n");
2067 printk( "[ INFO: possible irq lock inversion dependency detected ]\n");
2068 print_kernel_version();
2069 printk( "---------------------------------------------------------\n");
2070 printk("%s/%d just changed the state of lock:\n",
2071 curr->comm, task_pid_nr(curr));
2074 printk("but this lock took another, %s-unsafe lock in the past:\n", irqclass);
2076 printk("but this lock was taken by another, %s-safe lock in the past:\n", irqclass);
2077 print_lock_name(other->class);
2078 printk("\n\nand interrupts could create inverse lock ordering between them.\n\n");
2080 printk("\nother info that might help us debug this:\n");
2081 lockdep_print_held_locks(curr);
2083 printk("\nthe shortest dependencies between 2nd lock and 1st lock:\n");
2084 if (!save_trace(&root->trace))
2086 print_shortest_lock_dependencies(other, root);
2088 printk("\nstack backtrace:\n");
2095 * Prove that in the forwards-direction subgraph starting at <this>
2096 * there is no lock matching <mask>:
2099 check_usage_forwards(struct task_struct *curr, struct held_lock *this,
2100 enum lock_usage_bit bit, const char *irqclass)
2103 struct lock_list root;
2104 struct lock_list *uninitialized_var(target_entry);
2107 root.class = hlock_class(this);
2108 ret = find_usage_forwards(&root, bit, &target_entry);
2110 return print_bfs_bug(ret);
2114 return print_irq_inversion_bug(curr, &root, target_entry,
2119 * Prove that in the backwards-direction subgraph starting at <this>
2120 * there is no lock matching <mask>:
2123 check_usage_backwards(struct task_struct *curr, struct held_lock *this,
2124 enum lock_usage_bit bit, const char *irqclass)
2127 struct lock_list root;
2128 struct lock_list *uninitialized_var(target_entry);
2131 root.class = hlock_class(this);
2132 ret = find_usage_backwards(&root, bit, &target_entry);
2134 return print_bfs_bug(ret);
2138 return print_irq_inversion_bug(curr, &root, target_entry,
2142 void print_irqtrace_events(struct task_struct *curr)
2144 printk("irq event stamp: %u\n", curr->irq_events);
2145 printk("hardirqs last enabled at (%u): ", curr->hardirq_enable_event);
2146 print_ip_sym(curr->hardirq_enable_ip);
2147 printk("hardirqs last disabled at (%u): ", curr->hardirq_disable_event);
2148 print_ip_sym(curr->hardirq_disable_ip);
2149 printk("softirqs last enabled at (%u): ", curr->softirq_enable_event);
2150 print_ip_sym(curr->softirq_enable_ip);
2151 printk("softirqs last disabled at (%u): ", curr->softirq_disable_event);
2152 print_ip_sym(curr->softirq_disable_ip);
2155 static int HARDIRQ_verbose(struct lock_class *class)
2158 return class_filter(class);
2163 static int SOFTIRQ_verbose(struct lock_class *class)
2166 return class_filter(class);
2171 static int RECLAIM_FS_verbose(struct lock_class *class)
2174 return class_filter(class);
2179 #define STRICT_READ_CHECKS 1
2181 static int (*state_verbose_f[])(struct lock_class *class) = {
2182 #define LOCKDEP_STATE(__STATE) \
2184 #include "lockdep_states.h"
2185 #undef LOCKDEP_STATE
2188 static inline int state_verbose(enum lock_usage_bit bit,
2189 struct lock_class *class)
2191 return state_verbose_f[bit >> 2](class);
2194 typedef int (*check_usage_f)(struct task_struct *, struct held_lock *,
2195 enum lock_usage_bit bit, const char *name);
2198 mark_lock_irq(struct task_struct *curr, struct held_lock *this,
2199 enum lock_usage_bit new_bit)
2201 int excl_bit = exclusive_bit(new_bit);
2202 int read = new_bit & 1;
2203 int dir = new_bit & 2;
2206 * mark USED_IN has to look forwards -- to ensure no dependency
2207 * has ENABLED state, which would allow recursion deadlocks.
2209 * mark ENABLED has to look backwards -- to ensure no dependee
2210 * has USED_IN state, which, again, would allow recursion deadlocks.
2212 check_usage_f usage = dir ?
2213 check_usage_backwards : check_usage_forwards;
2216 * Validate that this particular lock does not have conflicting
2219 if (!valid_state(curr, this, new_bit, excl_bit))
2223 * Validate that the lock dependencies don't have conflicting usage
2226 if ((!read || !dir || STRICT_READ_CHECKS) &&
2227 !usage(curr, this, excl_bit, state_name(new_bit & ~1)))
2231 * Check for read in write conflicts
2234 if (!valid_state(curr, this, new_bit, excl_bit + 1))
2237 if (STRICT_READ_CHECKS &&
2238 !usage(curr, this, excl_bit + 1,
2239 state_name(new_bit + 1)))
2243 if (state_verbose(new_bit, hlock_class(this)))
2250 #define LOCKDEP_STATE(__STATE) __STATE,
2251 #include "lockdep_states.h"
2252 #undef LOCKDEP_STATE
2256 * Mark all held locks with a usage bit:
2259 mark_held_locks(struct task_struct *curr, enum mark_type mark)
2261 enum lock_usage_bit usage_bit;
2262 struct held_lock *hlock;
2265 for (i = 0; i < curr->lockdep_depth; i++) {
2266 hlock = curr->held_locks + i;
2268 usage_bit = 2 + (mark << 2); /* ENABLED */
2270 usage_bit += 1; /* READ */
2272 BUG_ON(usage_bit >= LOCK_USAGE_STATES);
2274 if (!mark_lock(curr, hlock, usage_bit))
2282 * Debugging helper: via this flag we know that we are in
2283 * 'early bootup code', and will warn about any invalid irqs-on event:
2285 static int early_boot_irqs_enabled;
2287 void early_boot_irqs_off(void)
2289 early_boot_irqs_enabled = 0;
2292 void early_boot_irqs_on(void)
2294 early_boot_irqs_enabled = 1;
2298 * Hardirqs will be enabled:
2300 void trace_hardirqs_on_caller(unsigned long ip)
2302 struct task_struct *curr = current;
2304 time_hardirqs_on(CALLER_ADDR0, ip);
2306 if (unlikely(!debug_locks || current->lockdep_recursion))
2309 if (DEBUG_LOCKS_WARN_ON(unlikely(!early_boot_irqs_enabled)))
2312 if (unlikely(curr->hardirqs_enabled)) {
2313 debug_atomic_inc(&redundant_hardirqs_on);
2316 /* we'll do an OFF -> ON transition: */
2317 curr->hardirqs_enabled = 1;
2319 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2321 if (DEBUG_LOCKS_WARN_ON(current->hardirq_context))
2324 * We are going to turn hardirqs on, so set the
2325 * usage bit for all held locks:
2327 if (!mark_held_locks(curr, HARDIRQ))
2330 * If we have softirqs enabled, then set the usage
2331 * bit for all held locks. (disabled hardirqs prevented
2332 * this bit from being set before)
2334 if (curr->softirqs_enabled)
2335 if (!mark_held_locks(curr, SOFTIRQ))
2338 curr->hardirq_enable_ip = ip;
2339 curr->hardirq_enable_event = ++curr->irq_events;
2340 debug_atomic_inc(&hardirqs_on_events);
2342 EXPORT_SYMBOL(trace_hardirqs_on_caller);
2344 void trace_hardirqs_on(void)
2346 trace_hardirqs_on_caller(CALLER_ADDR0);
2348 EXPORT_SYMBOL(trace_hardirqs_on);
2351 * Hardirqs were disabled:
2353 void trace_hardirqs_off_caller(unsigned long ip)
2355 struct task_struct *curr = current;
2357 time_hardirqs_off(CALLER_ADDR0, ip);
2359 if (unlikely(!debug_locks || current->lockdep_recursion))
2362 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2365 if (curr->hardirqs_enabled) {
2367 * We have done an ON -> OFF transition:
2369 curr->hardirqs_enabled = 0;
2370 curr->hardirq_disable_ip = ip;
2371 curr->hardirq_disable_event = ++curr->irq_events;
2372 debug_atomic_inc(&hardirqs_off_events);
2374 debug_atomic_inc(&redundant_hardirqs_off);
2376 EXPORT_SYMBOL(trace_hardirqs_off_caller);
2378 void trace_hardirqs_off(void)
2380 trace_hardirqs_off_caller(CALLER_ADDR0);
2382 EXPORT_SYMBOL(trace_hardirqs_off);
2385 * Softirqs will be enabled:
2387 void trace_softirqs_on(unsigned long ip)
2389 struct task_struct *curr = current;
2391 if (unlikely(!debug_locks))
2394 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2397 if (curr->softirqs_enabled) {
2398 debug_atomic_inc(&redundant_softirqs_on);
2403 * We'll do an OFF -> ON transition:
2405 curr->softirqs_enabled = 1;
2406 curr->softirq_enable_ip = ip;
2407 curr->softirq_enable_event = ++curr->irq_events;
2408 debug_atomic_inc(&softirqs_on_events);
2410 * We are going to turn softirqs on, so set the
2411 * usage bit for all held locks, if hardirqs are
2414 if (curr->hardirqs_enabled)
2415 mark_held_locks(curr, SOFTIRQ);
2419 * Softirqs were disabled:
2421 void trace_softirqs_off(unsigned long ip)
2423 struct task_struct *curr = current;
2425 if (unlikely(!debug_locks))
2428 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2431 if (curr->softirqs_enabled) {
2433 * We have done an ON -> OFF transition:
2435 curr->softirqs_enabled = 0;
2436 curr->softirq_disable_ip = ip;
2437 curr->softirq_disable_event = ++curr->irq_events;
2438 debug_atomic_inc(&softirqs_off_events);
2439 DEBUG_LOCKS_WARN_ON(!softirq_count());
2441 debug_atomic_inc(&redundant_softirqs_off);
2444 static void __lockdep_trace_alloc(gfp_t gfp_mask, unsigned long flags)
2446 struct task_struct *curr = current;
2448 if (unlikely(!debug_locks))
2451 /* no reclaim without waiting on it */
2452 if (!(gfp_mask & __GFP_WAIT))
2455 /* this guy won't enter reclaim */
2456 if ((curr->flags & PF_MEMALLOC) && !(gfp_mask & __GFP_NOMEMALLOC))
2459 /* We're only interested __GFP_FS allocations for now */
2460 if (!(gfp_mask & __GFP_FS))
2463 if (DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags)))
2466 mark_held_locks(curr, RECLAIM_FS);
2469 static void check_flags(unsigned long flags);
2471 void lockdep_trace_alloc(gfp_t gfp_mask)
2473 unsigned long flags;
2475 if (unlikely(current->lockdep_recursion))
2478 raw_local_irq_save(flags);
2480 current->lockdep_recursion = 1;
2481 __lockdep_trace_alloc(gfp_mask, flags);
2482 current->lockdep_recursion = 0;
2483 raw_local_irq_restore(flags);
2486 static int mark_irqflags(struct task_struct *curr, struct held_lock *hlock)
2489 * If non-trylock use in a hardirq or softirq context, then
2490 * mark the lock as used in these contexts:
2492 if (!hlock->trylock) {
2494 if (curr->hardirq_context)
2495 if (!mark_lock(curr, hlock,
2496 LOCK_USED_IN_HARDIRQ_READ))
2498 if (curr->softirq_context)
2499 if (!mark_lock(curr, hlock,
2500 LOCK_USED_IN_SOFTIRQ_READ))
2503 if (curr->hardirq_context)
2504 if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ))
2506 if (curr->softirq_context)
2507 if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ))
2511 if (!hlock->hardirqs_off) {
2513 if (!mark_lock(curr, hlock,
2514 LOCK_ENABLED_HARDIRQ_READ))
2516 if (curr->softirqs_enabled)
2517 if (!mark_lock(curr, hlock,
2518 LOCK_ENABLED_SOFTIRQ_READ))
2521 if (!mark_lock(curr, hlock,
2522 LOCK_ENABLED_HARDIRQ))
2524 if (curr->softirqs_enabled)
2525 if (!mark_lock(curr, hlock,
2526 LOCK_ENABLED_SOFTIRQ))
2532 * We reuse the irq context infrastructure more broadly as a general
2533 * context checking code. This tests GFP_FS recursion (a lock taken
2534 * during reclaim for a GFP_FS allocation is held over a GFP_FS
2537 if (!hlock->trylock && (curr->lockdep_reclaim_gfp & __GFP_FS)) {
2539 if (!mark_lock(curr, hlock, LOCK_USED_IN_RECLAIM_FS_READ))
2542 if (!mark_lock(curr, hlock, LOCK_USED_IN_RECLAIM_FS))
2550 static int separate_irq_context(struct task_struct *curr,
2551 struct held_lock *hlock)
2553 unsigned int depth = curr->lockdep_depth;
2556 * Keep track of points where we cross into an interrupt context:
2558 hlock->irq_context = 2*(curr->hardirq_context ? 1 : 0) +
2559 curr->softirq_context;
2561 struct held_lock *prev_hlock;
2563 prev_hlock = curr->held_locks + depth-1;
2565 * If we cross into another context, reset the
2566 * hash key (this also prevents the checking and the
2567 * adding of the dependency to 'prev'):
2569 if (prev_hlock->irq_context != hlock->irq_context)
2578 int mark_lock_irq(struct task_struct *curr, struct held_lock *this,
2579 enum lock_usage_bit new_bit)
2585 static inline int mark_irqflags(struct task_struct *curr,
2586 struct held_lock *hlock)
2591 static inline int separate_irq_context(struct task_struct *curr,
2592 struct held_lock *hlock)
2597 void lockdep_trace_alloc(gfp_t gfp_mask)
2604 * Mark a lock with a usage bit, and validate the state transition:
2606 static int mark_lock(struct task_struct *curr, struct held_lock *this,
2607 enum lock_usage_bit new_bit)
2609 unsigned int new_mask = 1 << new_bit, ret = 1;
2612 * If already set then do not dirty the cacheline,
2613 * nor do any checks:
2615 if (likely(hlock_class(this)->usage_mask & new_mask))
2621 * Make sure we didnt race:
2623 if (unlikely(hlock_class(this)->usage_mask & new_mask)) {
2628 hlock_class(this)->usage_mask |= new_mask;
2630 if (!save_trace(hlock_class(this)->usage_traces + new_bit))
2634 #define LOCKDEP_STATE(__STATE) \
2635 case LOCK_USED_IN_##__STATE: \
2636 case LOCK_USED_IN_##__STATE##_READ: \
2637 case LOCK_ENABLED_##__STATE: \
2638 case LOCK_ENABLED_##__STATE##_READ:
2639 #include "lockdep_states.h"
2640 #undef LOCKDEP_STATE
2641 ret = mark_lock_irq(curr, this, new_bit);
2646 debug_atomic_dec(&nr_unused_locks);
2649 if (!debug_locks_off_graph_unlock())
2658 * We must printk outside of the graph_lock:
2661 printk("\nmarked lock as {%s}:\n", usage_str[new_bit]);
2663 print_irqtrace_events(curr);
2671 * Initialize a lock instance's lock-class mapping info:
2673 void lockdep_init_map(struct lockdep_map *lock, const char *name,
2674 struct lock_class_key *key, int subclass)
2676 lock->class_cache = NULL;
2677 #ifdef CONFIG_LOCK_STAT
2678 lock->cpu = raw_smp_processor_id();
2681 if (DEBUG_LOCKS_WARN_ON(!name)) {
2682 lock->name = "NULL";
2688 if (DEBUG_LOCKS_WARN_ON(!key))
2691 * Sanity check, the lock-class key must be persistent:
2693 if (!static_obj(key)) {
2694 printk("BUG: key %p not in .data!\n", key);
2695 DEBUG_LOCKS_WARN_ON(1);
2700 if (unlikely(!debug_locks))
2704 register_lock_class(lock, subclass, 1);
2706 EXPORT_SYMBOL_GPL(lockdep_init_map);
2709 * This gets called for every mutex_lock*()/spin_lock*() operation.
2710 * We maintain the dependency maps and validate the locking attempt:
2712 static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
2713 int trylock, int read, int check, int hardirqs_off,
2714 struct lockdep_map *nest_lock, unsigned long ip,
2717 struct task_struct *curr = current;
2718 struct lock_class *class = NULL;
2719 struct held_lock *hlock;
2720 unsigned int depth, id;
2728 if (unlikely(!debug_locks))
2731 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2734 if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
2736 printk("BUG: MAX_LOCKDEP_SUBCLASSES too low!\n");
2737 printk("turning off the locking correctness validator.\n");
2743 class = lock->class_cache;
2745 * Not cached yet or subclass?
2747 if (unlikely(!class)) {
2748 class = register_lock_class(lock, subclass, 0);
2752 debug_atomic_inc((atomic_t *)&class->ops);
2753 if (very_verbose(class)) {
2754 printk("\nacquire class [%p] %s", class->key, class->name);
2755 if (class->name_version > 1)
2756 printk("#%d", class->name_version);
2762 * Add the lock to the list of currently held locks.
2763 * (we dont increase the depth just yet, up until the
2764 * dependency checks are done)
2766 depth = curr->lockdep_depth;
2767 if (DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH))
2770 class_idx = class - lock_classes + 1;
2773 hlock = curr->held_locks + depth - 1;
2774 if (hlock->class_idx == class_idx && nest_lock) {
2775 if (hlock->references)
2776 hlock->references++;
2778 hlock->references = 2;
2784 hlock = curr->held_locks + depth;
2785 if (DEBUG_LOCKS_WARN_ON(!class))
2787 hlock->class_idx = class_idx;
2788 hlock->acquire_ip = ip;
2789 hlock->instance = lock;
2790 hlock->nest_lock = nest_lock;
2791 hlock->trylock = trylock;
2793 hlock->check = check;
2794 hlock->hardirqs_off = !!hardirqs_off;
2795 hlock->references = references;
2796 #ifdef CONFIG_LOCK_STAT
2797 hlock->waittime_stamp = 0;
2798 hlock->holdtime_stamp = lockstat_clock();
2801 if (check == 2 && !mark_irqflags(curr, hlock))
2804 /* mark it as used: */
2805 if (!mark_lock(curr, hlock, LOCK_USED))
2809 * Calculate the chain hash: it's the combined hash of all the
2810 * lock keys along the dependency chain. We save the hash value
2811 * at every step so that we can get the current hash easily
2812 * after unlock. The chain hash is then used to cache dependency
2815 * The 'key ID' is what is the most compact key value to drive
2816 * the hash, not class->key.
2818 id = class - lock_classes;
2819 if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
2822 chain_key = curr->curr_chain_key;
2824 if (DEBUG_LOCKS_WARN_ON(chain_key != 0))
2829 hlock->prev_chain_key = chain_key;
2830 if (separate_irq_context(curr, hlock)) {
2834 chain_key = iterate_chain_key(chain_key, id);
2836 if (!validate_chain(curr, lock, hlock, chain_head, chain_key))
2839 curr->curr_chain_key = chain_key;
2840 curr->lockdep_depth++;
2841 check_chain_key(curr);
2842 #ifdef CONFIG_DEBUG_LOCKDEP
2843 if (unlikely(!debug_locks))
2846 if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
2848 printk("BUG: MAX_LOCK_DEPTH too low!\n");
2849 printk("turning off the locking correctness validator.\n");
2854 if (unlikely(curr->lockdep_depth > max_lockdep_depth))
2855 max_lockdep_depth = curr->lockdep_depth;
2861 print_unlock_inbalance_bug(struct task_struct *curr, struct lockdep_map *lock,
2864 if (!debug_locks_off())
2866 if (debug_locks_silent)
2869 printk("\n=====================================\n");
2870 printk( "[ BUG: bad unlock balance detected! ]\n");
2871 printk( "-------------------------------------\n");
2872 printk("%s/%d is trying to release lock (",
2873 curr->comm, task_pid_nr(curr));
2874 print_lockdep_cache(lock);
2877 printk("but there are no more locks to release!\n");
2878 printk("\nother info that might help us debug this:\n");
2879 lockdep_print_held_locks(curr);
2881 printk("\nstack backtrace:\n");
2888 * Common debugging checks for both nested and non-nested unlock:
2890 static int check_unlock(struct task_struct *curr, struct lockdep_map *lock,
2893 if (unlikely(!debug_locks))
2895 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2898 if (curr->lockdep_depth <= 0)
2899 return print_unlock_inbalance_bug(curr, lock, ip);
2904 static int match_held_lock(struct held_lock *hlock, struct lockdep_map *lock)
2906 if (hlock->instance == lock)
2909 if (hlock->references) {
2910 struct lock_class *class = lock->class_cache;
2913 class = look_up_lock_class(lock, 0);
2915 if (DEBUG_LOCKS_WARN_ON(!class))
2918 if (DEBUG_LOCKS_WARN_ON(!hlock->nest_lock))
2921 if (hlock->class_idx == class - lock_classes + 1)
2929 __lock_set_class(struct lockdep_map *lock, const char *name,
2930 struct lock_class_key *key, unsigned int subclass,
2933 struct task_struct *curr = current;
2934 struct held_lock *hlock, *prev_hlock;
2935 struct lock_class *class;
2939 depth = curr->lockdep_depth;
2940 if (DEBUG_LOCKS_WARN_ON(!depth))
2944 for (i = depth-1; i >= 0; i--) {
2945 hlock = curr->held_locks + i;
2947 * We must not cross into another context:
2949 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
2951 if (match_held_lock(hlock, lock))
2955 return print_unlock_inbalance_bug(curr, lock, ip);
2958 lockdep_init_map(lock, name, key, 0);
2959 class = register_lock_class(lock, subclass, 0);
2960 hlock->class_idx = class - lock_classes + 1;
2962 curr->lockdep_depth = i;
2963 curr->curr_chain_key = hlock->prev_chain_key;
2965 for (; i < depth; i++) {
2966 hlock = curr->held_locks + i;
2967 if (!__lock_acquire(hlock->instance,
2968 hlock_class(hlock)->subclass, hlock->trylock,
2969 hlock->read, hlock->check, hlock->hardirqs_off,
2970 hlock->nest_lock, hlock->acquire_ip,
2975 if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth))
2981 * Remove the lock to the list of currently held locks in a
2982 * potentially non-nested (out of order) manner. This is a
2983 * relatively rare operation, as all the unlock APIs default
2984 * to nested mode (which uses lock_release()):
2987 lock_release_non_nested(struct task_struct *curr,
2988 struct lockdep_map *lock, unsigned long ip)
2990 struct held_lock *hlock, *prev_hlock;
2995 * Check whether the lock exists in the current stack
2998 depth = curr->lockdep_depth;
2999 if (DEBUG_LOCKS_WARN_ON(!depth))
3003 for (i = depth-1; i >= 0; i--) {
3004 hlock = curr->held_locks + i;
3006 * We must not cross into another context:
3008 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3010 if (match_held_lock(hlock, lock))
3014 return print_unlock_inbalance_bug(curr, lock, ip);
3017 if (hlock->instance == lock)
3018 lock_release_holdtime(hlock);
3020 if (hlock->references) {
3021 hlock->references--;
3022 if (hlock->references) {
3024 * We had, and after removing one, still have
3025 * references, the current lock stack is still
3026 * valid. We're done!
3033 * We have the right lock to unlock, 'hlock' points to it.
3034 * Now we remove it from the stack, and add back the other
3035 * entries (if any), recalculating the hash along the way:
3038 curr->lockdep_depth = i;
3039 curr->curr_chain_key = hlock->prev_chain_key;
3041 for (i++; i < depth; i++) {
3042 hlock = curr->held_locks + i;
3043 if (!__lock_acquire(hlock->instance,
3044 hlock_class(hlock)->subclass, hlock->trylock,
3045 hlock->read, hlock->check, hlock->hardirqs_off,
3046 hlock->nest_lock, hlock->acquire_ip,
3051 if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - 1))
3057 * Remove the lock to the list of currently held locks - this gets
3058 * called on mutex_unlock()/spin_unlock*() (or on a failed
3059 * mutex_lock_interruptible()). This is done for unlocks that nest
3060 * perfectly. (i.e. the current top of the lock-stack is unlocked)
3062 static int lock_release_nested(struct task_struct *curr,
3063 struct lockdep_map *lock, unsigned long ip)
3065 struct held_lock *hlock;
3069 * Pop off the top of the lock stack:
3071 depth = curr->lockdep_depth - 1;
3072 hlock = curr->held_locks + depth;
3075 * Is the unlock non-nested:
3077 if (hlock->instance != lock || hlock->references)
3078 return lock_release_non_nested(curr, lock, ip);
3079 curr->lockdep_depth--;
3081 if (DEBUG_LOCKS_WARN_ON(!depth && (hlock->prev_chain_key != 0)))
3084 curr->curr_chain_key = hlock->prev_chain_key;
3086 lock_release_holdtime(hlock);
3088 #ifdef CONFIG_DEBUG_LOCKDEP
3089 hlock->prev_chain_key = 0;
3090 hlock->class_idx = 0;
3091 hlock->acquire_ip = 0;
3092 hlock->irq_context = 0;
3098 * Remove the lock to the list of currently held locks - this gets
3099 * called on mutex_unlock()/spin_unlock*() (or on a failed
3100 * mutex_lock_interruptible()). This is done for unlocks that nest
3101 * perfectly. (i.e. the current top of the lock-stack is unlocked)
3104 __lock_release(struct lockdep_map *lock, int nested, unsigned long ip)
3106 struct task_struct *curr = current;
3108 if (!check_unlock(curr, lock, ip))
3112 if (!lock_release_nested(curr, lock, ip))
3115 if (!lock_release_non_nested(curr, lock, ip))
3119 check_chain_key(curr);
3122 static int __lock_is_held(struct lockdep_map *lock)
3124 struct task_struct *curr = current;
3127 for (i = 0; i < curr->lockdep_depth; i++) {
3128 struct held_lock *hlock = curr->held_locks + i;
3130 if (match_held_lock(hlock, lock))
3138 * Check whether we follow the irq-flags state precisely:
3140 static void check_flags(unsigned long flags)
3142 #if defined(CONFIG_PROVE_LOCKING) && defined(CONFIG_DEBUG_LOCKDEP) && \
3143 defined(CONFIG_TRACE_IRQFLAGS)
3147 if (irqs_disabled_flags(flags)) {
3148 if (DEBUG_LOCKS_WARN_ON(current->hardirqs_enabled)) {
3149 printk("possible reason: unannotated irqs-off.\n");
3152 if (DEBUG_LOCKS_WARN_ON(!current->hardirqs_enabled)) {
3153 printk("possible reason: unannotated irqs-on.\n");
3158 * We dont accurately track softirq state in e.g.
3159 * hardirq contexts (such as on 4KSTACKS), so only
3160 * check if not in hardirq contexts:
3162 if (!hardirq_count()) {
3163 if (softirq_count())
3164 DEBUG_LOCKS_WARN_ON(current->softirqs_enabled);
3166 DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled);
3170 print_irqtrace_events(current);
3174 void lock_set_class(struct lockdep_map *lock, const char *name,
3175 struct lock_class_key *key, unsigned int subclass,
3178 unsigned long flags;
3180 if (unlikely(current->lockdep_recursion))
3183 raw_local_irq_save(flags);
3184 current->lockdep_recursion = 1;
3186 if (__lock_set_class(lock, name, key, subclass, ip))
3187 check_chain_key(current);
3188 current->lockdep_recursion = 0;
3189 raw_local_irq_restore(flags);
3191 EXPORT_SYMBOL_GPL(lock_set_class);
3194 * We are not always called with irqs disabled - do that here,
3195 * and also avoid lockdep recursion:
3197 void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
3198 int trylock, int read, int check,
3199 struct lockdep_map *nest_lock, unsigned long ip)
3201 unsigned long flags;
3203 if (unlikely(current->lockdep_recursion))
3206 raw_local_irq_save(flags);
3209 current->lockdep_recursion = 1;
3210 trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip);
3211 __lock_acquire(lock, subclass, trylock, read, check,
3212 irqs_disabled_flags(flags), nest_lock, ip, 0);
3213 current->lockdep_recursion = 0;
3214 raw_local_irq_restore(flags);
3216 EXPORT_SYMBOL_GPL(lock_acquire);
3218 void lock_release(struct lockdep_map *lock, int nested,
3221 unsigned long flags;
3223 if (unlikely(current->lockdep_recursion))
3226 raw_local_irq_save(flags);
3228 current->lockdep_recursion = 1;
3229 trace_lock_release(lock, nested, ip);
3230 __lock_release(lock, nested, ip);
3231 current->lockdep_recursion = 0;
3232 raw_local_irq_restore(flags);
3234 EXPORT_SYMBOL_GPL(lock_release);
3236 int lock_is_held(struct lockdep_map *lock)
3238 unsigned long flags;
3241 if (unlikely(current->lockdep_recursion))
3244 raw_local_irq_save(flags);
3247 current->lockdep_recursion = 1;
3248 ret = __lock_is_held(lock);
3249 current->lockdep_recursion = 0;
3250 raw_local_irq_restore(flags);
3254 EXPORT_SYMBOL_GPL(lock_is_held);
3256 void lockdep_set_current_reclaim_state(gfp_t gfp_mask)
3258 current->lockdep_reclaim_gfp = gfp_mask;
3261 void lockdep_clear_current_reclaim_state(void)
3263 current->lockdep_reclaim_gfp = 0;
3266 #ifdef CONFIG_LOCK_STAT
3268 print_lock_contention_bug(struct task_struct *curr, struct lockdep_map *lock,
3271 if (!debug_locks_off())
3273 if (debug_locks_silent)
3276 printk("\n=================================\n");
3277 printk( "[ BUG: bad contention detected! ]\n");
3278 printk( "---------------------------------\n");
3279 printk("%s/%d is trying to contend lock (",
3280 curr->comm, task_pid_nr(curr));
3281 print_lockdep_cache(lock);
3284 printk("but there are no locks held!\n");
3285 printk("\nother info that might help us debug this:\n");
3286 lockdep_print_held_locks(curr);
3288 printk("\nstack backtrace:\n");
3295 __lock_contended(struct lockdep_map *lock, unsigned long ip)
3297 struct task_struct *curr = current;
3298 struct held_lock *hlock, *prev_hlock;
3299 struct lock_class_stats *stats;
3301 int i, contention_point, contending_point;
3303 depth = curr->lockdep_depth;
3304 if (DEBUG_LOCKS_WARN_ON(!depth))
3308 for (i = depth-1; i >= 0; i--) {
3309 hlock = curr->held_locks + i;
3311 * We must not cross into another context:
3313 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3315 if (match_held_lock(hlock, lock))
3319 print_lock_contention_bug(curr, lock, ip);
3323 if (hlock->instance != lock)
3326 hlock->waittime_stamp = lockstat_clock();
3328 contention_point = lock_point(hlock_class(hlock)->contention_point, ip);
3329 contending_point = lock_point(hlock_class(hlock)->contending_point,
3332 stats = get_lock_stats(hlock_class(hlock));
3333 if (contention_point < LOCKSTAT_POINTS)
3334 stats->contention_point[contention_point]++;
3335 if (contending_point < LOCKSTAT_POINTS)
3336 stats->contending_point[contending_point]++;
3337 if (lock->cpu != smp_processor_id())
3338 stats->bounces[bounce_contended + !!hlock->read]++;
3339 put_lock_stats(stats);
3343 __lock_acquired(struct lockdep_map *lock, unsigned long ip)
3345 struct task_struct *curr = current;
3346 struct held_lock *hlock, *prev_hlock;
3347 struct lock_class_stats *stats;
3349 u64 now, waittime = 0;
3352 depth = curr->lockdep_depth;
3353 if (DEBUG_LOCKS_WARN_ON(!depth))
3357 for (i = depth-1; i >= 0; i--) {
3358 hlock = curr->held_locks + i;
3360 * We must not cross into another context:
3362 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3364 if (match_held_lock(hlock, lock))
3368 print_lock_contention_bug(curr, lock, _RET_IP_);
3372 if (hlock->instance != lock)
3375 cpu = smp_processor_id();
3376 if (hlock->waittime_stamp) {
3377 now = lockstat_clock();
3378 waittime = now - hlock->waittime_stamp;
3379 hlock->holdtime_stamp = now;
3382 trace_lock_acquired(lock, ip, waittime);
3384 stats = get_lock_stats(hlock_class(hlock));
3387 lock_time_inc(&stats->read_waittime, waittime);
3389 lock_time_inc(&stats->write_waittime, waittime);
3391 if (lock->cpu != cpu)
3392 stats->bounces[bounce_acquired + !!hlock->read]++;
3393 put_lock_stats(stats);
3399 void lock_contended(struct lockdep_map *lock, unsigned long ip)
3401 unsigned long flags;
3403 if (unlikely(!lock_stat))
3406 if (unlikely(current->lockdep_recursion))
3409 raw_local_irq_save(flags);
3411 current->lockdep_recursion = 1;
3412 trace_lock_contended(lock, ip);
3413 __lock_contended(lock, ip);
3414 current->lockdep_recursion = 0;
3415 raw_local_irq_restore(flags);
3417 EXPORT_SYMBOL_GPL(lock_contended);
3419 void lock_acquired(struct lockdep_map *lock, unsigned long ip)
3421 unsigned long flags;
3423 if (unlikely(!lock_stat))
3426 if (unlikely(current->lockdep_recursion))
3429 raw_local_irq_save(flags);
3431 current->lockdep_recursion = 1;
3432 __lock_acquired(lock, ip);
3433 current->lockdep_recursion = 0;
3434 raw_local_irq_restore(flags);
3436 EXPORT_SYMBOL_GPL(lock_acquired);
3440 * Used by the testsuite, sanitize the validator state
3441 * after a simulated failure:
3444 void lockdep_reset(void)
3446 unsigned long flags;
3449 raw_local_irq_save(flags);
3450 current->curr_chain_key = 0;
3451 current->lockdep_depth = 0;
3452 current->lockdep_recursion = 0;
3453 memset(current->held_locks, 0, MAX_LOCK_DEPTH*sizeof(struct held_lock));
3454 nr_hardirq_chains = 0;
3455 nr_softirq_chains = 0;
3456 nr_process_chains = 0;
3458 for (i = 0; i < CHAINHASH_SIZE; i++)
3459 INIT_LIST_HEAD(chainhash_table + i);
3460 raw_local_irq_restore(flags);
3463 static void zap_class(struct lock_class *class)
3468 * Remove all dependencies this lock is
3471 for (i = 0; i < nr_list_entries; i++) {
3472 if (list_entries[i].class == class)
3473 list_del_rcu(&list_entries[i].entry);
3476 * Unhash the class and remove it from the all_lock_classes list:
3478 list_del_rcu(&class->hash_entry);
3479 list_del_rcu(&class->lock_entry);
3484 static inline int within(const void *addr, void *start, unsigned long size)
3486 return addr >= start && addr < start + size;
3489 void lockdep_free_key_range(void *start, unsigned long size)
3491 struct lock_class *class, *next;
3492 struct list_head *head;
3493 unsigned long flags;
3497 raw_local_irq_save(flags);
3498 locked = graph_lock();
3501 * Unhash all classes that were created by this module:
3503 for (i = 0; i < CLASSHASH_SIZE; i++) {
3504 head = classhash_table + i;
3505 if (list_empty(head))
3507 list_for_each_entry_safe(class, next, head, hash_entry) {
3508 if (within(class->key, start, size))
3510 else if (within(class->name, start, size))
3517 raw_local_irq_restore(flags);
3520 void lockdep_reset_lock(struct lockdep_map *lock)
3522 struct lock_class *class, *next;
3523 struct list_head *head;
3524 unsigned long flags;
3528 raw_local_irq_save(flags);
3531 * Remove all classes this lock might have:
3533 for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) {
3535 * If the class exists we look it up and zap it:
3537 class = look_up_lock_class(lock, j);
3542 * Debug check: in the end all mapped classes should
3545 locked = graph_lock();
3546 for (i = 0; i < CLASSHASH_SIZE; i++) {
3547 head = classhash_table + i;
3548 if (list_empty(head))
3550 list_for_each_entry_safe(class, next, head, hash_entry) {
3551 if (unlikely(class == lock->class_cache)) {
3552 if (debug_locks_off_graph_unlock())
3562 raw_local_irq_restore(flags);
3565 void lockdep_init(void)
3570 * Some architectures have their own start_kernel()
3571 * code which calls lockdep_init(), while we also
3572 * call lockdep_init() from the start_kernel() itself,
3573 * and we want to initialize the hashes only once:
3575 if (lockdep_initialized)
3578 for (i = 0; i < CLASSHASH_SIZE; i++)
3579 INIT_LIST_HEAD(classhash_table + i);
3581 for (i = 0; i < CHAINHASH_SIZE; i++)
3582 INIT_LIST_HEAD(chainhash_table + i);
3584 lockdep_initialized = 1;
3587 void __init lockdep_info(void)
3589 printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");
3591 printk("... MAX_LOCKDEP_SUBCLASSES: %lu\n", MAX_LOCKDEP_SUBCLASSES);
3592 printk("... MAX_LOCK_DEPTH: %lu\n", MAX_LOCK_DEPTH);
3593 printk("... MAX_LOCKDEP_KEYS: %lu\n", MAX_LOCKDEP_KEYS);
3594 printk("... CLASSHASH_SIZE: %lu\n", CLASSHASH_SIZE);
3595 printk("... MAX_LOCKDEP_ENTRIES: %lu\n", MAX_LOCKDEP_ENTRIES);
3596 printk("... MAX_LOCKDEP_CHAINS: %lu\n", MAX_LOCKDEP_CHAINS);
3597 printk("... CHAINHASH_SIZE: %lu\n", CHAINHASH_SIZE);
3599 printk(" memory used by lock dependency info: %lu kB\n",
3600 (sizeof(struct lock_class) * MAX_LOCKDEP_KEYS +
3601 sizeof(struct list_head) * CLASSHASH_SIZE +
3602 sizeof(struct lock_list) * MAX_LOCKDEP_ENTRIES +
3603 sizeof(struct lock_chain) * MAX_LOCKDEP_CHAINS +
3604 sizeof(struct list_head) * CHAINHASH_SIZE
3605 #ifdef CONFIG_PROVE_LOCKING
3606 + sizeof(struct circular_queue)
3611 printk(" per task-struct memory footprint: %lu bytes\n",
3612 sizeof(struct held_lock) * MAX_LOCK_DEPTH);
3614 #ifdef CONFIG_DEBUG_LOCKDEP
3615 if (lockdep_init_error) {
3616 printk("WARNING: lockdep init error! Arch code didn't call lockdep_init() early enough?\n");
3617 printk("Call stack leading to lockdep invocation was:\n");
3618 print_stack_trace(&lockdep_init_trace, 0);
3624 print_freed_lock_bug(struct task_struct *curr, const void *mem_from,
3625 const void *mem_to, struct held_lock *hlock)
3627 if (!debug_locks_off())
3629 if (debug_locks_silent)
3632 printk("\n=========================\n");
3633 printk( "[ BUG: held lock freed! ]\n");
3634 printk( "-------------------------\n");
3635 printk("%s/%d is freeing memory %p-%p, with a lock still held there!\n",
3636 curr->comm, task_pid_nr(curr), mem_from, mem_to-1);
3638 lockdep_print_held_locks(curr);
3640 printk("\nstack backtrace:\n");
3644 static inline int not_in_range(const void* mem_from, unsigned long mem_len,
3645 const void* lock_from, unsigned long lock_len)
3647 return lock_from + lock_len <= mem_from ||
3648 mem_from + mem_len <= lock_from;
3652 * Called when kernel memory is freed (or unmapped), or if a lock
3653 * is destroyed or reinitialized - this code checks whether there is
3654 * any held lock in the memory range of <from> to <to>:
3656 void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len)
3658 struct task_struct *curr = current;
3659 struct held_lock *hlock;
3660 unsigned long flags;
3663 if (unlikely(!debug_locks))
3666 local_irq_save(flags);
3667 for (i = 0; i < curr->lockdep_depth; i++) {
3668 hlock = curr->held_locks + i;
3670 if (not_in_range(mem_from, mem_len, hlock->instance,
3671 sizeof(*hlock->instance)))
3674 print_freed_lock_bug(curr, mem_from, mem_from + mem_len, hlock);
3677 local_irq_restore(flags);
3679 EXPORT_SYMBOL_GPL(debug_check_no_locks_freed);
3681 static void print_held_locks_bug(struct task_struct *curr)
3683 if (!debug_locks_off())
3685 if (debug_locks_silent)
3688 printk("\n=====================================\n");
3689 printk( "[ BUG: lock held at task exit time! ]\n");
3690 printk( "-------------------------------------\n");
3691 printk("%s/%d is exiting with locks still held!\n",
3692 curr->comm, task_pid_nr(curr));
3693 lockdep_print_held_locks(curr);
3695 printk("\nstack backtrace:\n");
3699 void debug_check_no_locks_held(struct task_struct *task)
3701 if (unlikely(task->lockdep_depth > 0))
3702 print_held_locks_bug(task);
3705 void debug_show_all_locks(void)
3707 struct task_struct *g, *p;
3711 if (unlikely(!debug_locks)) {
3712 printk("INFO: lockdep is turned off.\n");
3715 printk("\nShowing all locks held in the system:\n");
3718 * Here we try to get the tasklist_lock as hard as possible,
3719 * if not successful after 2 seconds we ignore it (but keep
3720 * trying). This is to enable a debug printout even if a
3721 * tasklist_lock-holding task deadlocks or crashes.
3724 if (!read_trylock(&tasklist_lock)) {
3726 printk("hm, tasklist_lock locked, retrying... ");
3729 printk(" #%d", 10-count);
3733 printk(" ignoring it.\n");
3737 printk(KERN_CONT " locked it.\n");
3740 do_each_thread(g, p) {
3742 * It's not reliable to print a task's held locks
3743 * if it's not sleeping (or if it's not the current
3746 if (p->state == TASK_RUNNING && p != current)
3748 if (p->lockdep_depth)
3749 lockdep_print_held_locks(p);
3751 if (read_trylock(&tasklist_lock))
3753 } while_each_thread(g, p);
3756 printk("=============================================\n\n");
3759 read_unlock(&tasklist_lock);
3761 EXPORT_SYMBOL_GPL(debug_show_all_locks);
3764 * Careful: only use this function if you are sure that
3765 * the task cannot run in parallel!
3767 void __debug_show_held_locks(struct task_struct *task)
3769 if (unlikely(!debug_locks)) {
3770 printk("INFO: lockdep is turned off.\n");
3773 lockdep_print_held_locks(task);
3775 EXPORT_SYMBOL_GPL(__debug_show_held_locks);
3777 void debug_show_held_locks(struct task_struct *task)
3779 __debug_show_held_locks(task);
3781 EXPORT_SYMBOL_GPL(debug_show_held_locks);
3783 void lockdep_sys_exit(void)
3785 struct task_struct *curr = current;
3787 if (unlikely(curr->lockdep_depth)) {
3788 if (!debug_locks_off())
3790 printk("\n================================================\n");
3791 printk( "[ BUG: lock held when returning to user space! ]\n");
3792 printk( "------------------------------------------------\n");
3793 printk("%s/%d is leaving the kernel with locks still held!\n",
3794 curr->comm, curr->pid);
3795 lockdep_print_held_locks(curr);
3799 void lockdep_rcu_dereference(const char *file, const int line)
3801 struct task_struct *curr = current;
3803 if (!debug_locks_off())
3805 printk("\n===================================================\n");
3806 printk( "[ INFO: suspicious rcu_dereference_check() usage. ]\n");
3807 printk( "---------------------------------------------------\n");
3808 printk("%s:%d invoked rcu_dereference_check() without protection!\n",
3810 printk("\nother info that might help us debug this:\n\n");
3811 printk("\nrcu_scheduler_active = %d, debug_locks = %d\n", rcu_scheduler_active, debug_locks);
3812 lockdep_print_held_locks(curr);
3813 printk("\nstack backtrace:\n");
3816 EXPORT_SYMBOL_GPL(lockdep_rcu_dereference);