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>
46 #include <linux/gfp.h>
48 #include <asm/sections.h>
50 #include "lockdep_internals.h"
52 #define CREATE_TRACE_POINTS
53 #include <trace/events/lock.h>
55 #ifdef CONFIG_PROVE_LOCKING
56 int prove_locking = 1;
57 module_param(prove_locking, int, 0644);
59 #define prove_locking 0
62 #ifdef CONFIG_LOCK_STAT
64 module_param(lock_stat, int, 0644);
70 * lockdep_lock: protects the lockdep graph, the hashes and the
71 * class/list/hash allocators.
73 * This is one of the rare exceptions where it's justified
74 * to use a raw spinlock - we really dont want the spinlock
75 * code to recurse back into the lockdep code...
77 static arch_spinlock_t lockdep_lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
79 static int graph_lock(void)
81 arch_spin_lock(&lockdep_lock);
83 * Make sure that if another CPU detected a bug while
84 * walking the graph we dont change it (while the other
85 * CPU is busy printing out stuff with the graph lock
89 arch_spin_unlock(&lockdep_lock);
92 /* prevent any recursions within lockdep from causing deadlocks */
93 current->lockdep_recursion++;
97 static inline int graph_unlock(void)
99 if (debug_locks && !arch_spin_is_locked(&lockdep_lock))
100 return DEBUG_LOCKS_WARN_ON(1);
102 current->lockdep_recursion--;
103 arch_spin_unlock(&lockdep_lock);
108 * Turn lock debugging off and return with 0 if it was off already,
109 * and also release the graph lock:
111 static inline int debug_locks_off_graph_unlock(void)
113 int ret = debug_locks_off();
115 arch_spin_unlock(&lockdep_lock);
120 static int lockdep_initialized;
122 unsigned long nr_list_entries;
123 static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES];
126 * All data structures here are protected by the global debug_lock.
128 * Mutex key structs only get allocated, once during bootup, and never
129 * get freed - this significantly simplifies the debugging code.
131 unsigned long nr_lock_classes;
132 static struct lock_class lock_classes[MAX_LOCKDEP_KEYS];
134 static inline struct lock_class *hlock_class(struct held_lock *hlock)
136 if (!hlock->class_idx) {
137 DEBUG_LOCKS_WARN_ON(1);
140 return lock_classes + hlock->class_idx - 1;
143 #ifdef CONFIG_LOCK_STAT
144 static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS],
147 static inline u64 lockstat_clock(void)
149 return cpu_clock(smp_processor_id());
152 static int lock_point(unsigned long points[], unsigned long ip)
156 for (i = 0; i < LOCKSTAT_POINTS; i++) {
157 if (points[i] == 0) {
168 static void lock_time_inc(struct lock_time *lt, u64 time)
173 if (time < lt->min || !lt->nr)
180 static inline void lock_time_add(struct lock_time *src, struct lock_time *dst)
185 if (src->max > dst->max)
188 if (src->min < dst->min || !dst->nr)
191 dst->total += src->total;
195 struct lock_class_stats lock_stats(struct lock_class *class)
197 struct lock_class_stats stats;
200 memset(&stats, 0, sizeof(struct lock_class_stats));
201 for_each_possible_cpu(cpu) {
202 struct lock_class_stats *pcs =
203 &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
205 for (i = 0; i < ARRAY_SIZE(stats.contention_point); i++)
206 stats.contention_point[i] += pcs->contention_point[i];
208 for (i = 0; i < ARRAY_SIZE(stats.contending_point); i++)
209 stats.contending_point[i] += pcs->contending_point[i];
211 lock_time_add(&pcs->read_waittime, &stats.read_waittime);
212 lock_time_add(&pcs->write_waittime, &stats.write_waittime);
214 lock_time_add(&pcs->read_holdtime, &stats.read_holdtime);
215 lock_time_add(&pcs->write_holdtime, &stats.write_holdtime);
217 for (i = 0; i < ARRAY_SIZE(stats.bounces); i++)
218 stats.bounces[i] += pcs->bounces[i];
224 void clear_lock_stats(struct lock_class *class)
228 for_each_possible_cpu(cpu) {
229 struct lock_class_stats *cpu_stats =
230 &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
232 memset(cpu_stats, 0, sizeof(struct lock_class_stats));
234 memset(class->contention_point, 0, sizeof(class->contention_point));
235 memset(class->contending_point, 0, sizeof(class->contending_point));
238 static struct lock_class_stats *get_lock_stats(struct lock_class *class)
240 return &get_cpu_var(cpu_lock_stats)[class - lock_classes];
243 static void put_lock_stats(struct lock_class_stats *stats)
245 put_cpu_var(cpu_lock_stats);
248 static void lock_release_holdtime(struct held_lock *hlock)
250 struct lock_class_stats *stats;
256 holdtime = lockstat_clock() - hlock->holdtime_stamp;
258 stats = get_lock_stats(hlock_class(hlock));
260 lock_time_inc(&stats->read_holdtime, holdtime);
262 lock_time_inc(&stats->write_holdtime, holdtime);
263 put_lock_stats(stats);
266 static inline void lock_release_holdtime(struct held_lock *hlock)
272 * We keep a global list of all lock classes. The list only grows,
273 * never shrinks. The list is only accessed with the lockdep
274 * spinlock lock held.
276 LIST_HEAD(all_lock_classes);
279 * The lockdep classes are in a hash-table as well, for fast lookup:
281 #define CLASSHASH_BITS (MAX_LOCKDEP_KEYS_BITS - 1)
282 #define CLASSHASH_SIZE (1UL << CLASSHASH_BITS)
283 #define __classhashfn(key) hash_long((unsigned long)key, CLASSHASH_BITS)
284 #define classhashentry(key) (classhash_table + __classhashfn((key)))
286 static struct list_head classhash_table[CLASSHASH_SIZE];
289 * We put the lock dependency chains into a hash-table as well, to cache
292 #define CHAINHASH_BITS (MAX_LOCKDEP_CHAINS_BITS-1)
293 #define CHAINHASH_SIZE (1UL << CHAINHASH_BITS)
294 #define __chainhashfn(chain) hash_long(chain, CHAINHASH_BITS)
295 #define chainhashentry(chain) (chainhash_table + __chainhashfn((chain)))
297 static struct list_head chainhash_table[CHAINHASH_SIZE];
300 * The hash key of the lock dependency chains is a hash itself too:
301 * it's a hash of all locks taken up to that lock, including that lock.
302 * It's a 64-bit hash, because it's important for the keys to be
305 #define iterate_chain_key(key1, key2) \
306 (((key1) << MAX_LOCKDEP_KEYS_BITS) ^ \
307 ((key1) >> (64-MAX_LOCKDEP_KEYS_BITS)) ^ \
310 void lockdep_off(void)
312 current->lockdep_recursion++;
314 EXPORT_SYMBOL(lockdep_off);
316 void lockdep_on(void)
318 current->lockdep_recursion--;
320 EXPORT_SYMBOL(lockdep_on);
323 * Debugging switches:
327 #define VERY_VERBOSE 0
330 # define HARDIRQ_VERBOSE 1
331 # define SOFTIRQ_VERBOSE 1
332 # define RECLAIM_VERBOSE 1
334 # define HARDIRQ_VERBOSE 0
335 # define SOFTIRQ_VERBOSE 0
336 # define RECLAIM_VERBOSE 0
339 #if VERBOSE || HARDIRQ_VERBOSE || SOFTIRQ_VERBOSE || RECLAIM_VERBOSE
341 * Quick filtering for interesting events:
343 static int class_filter(struct lock_class *class)
347 if (class->name_version == 1 &&
348 !strcmp(class->name, "lockname"))
350 if (class->name_version == 1 &&
351 !strcmp(class->name, "&struct->lockfield"))
354 /* Filter everything else. 1 would be to allow everything else */
359 static int verbose(struct lock_class *class)
362 return class_filter(class);
368 * Stack-trace: tightly packed array of stack backtrace
369 * addresses. Protected by the graph_lock.
371 unsigned long nr_stack_trace_entries;
372 static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];
374 static int save_trace(struct stack_trace *trace)
376 trace->nr_entries = 0;
377 trace->max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries;
378 trace->entries = stack_trace + nr_stack_trace_entries;
382 save_stack_trace(trace);
385 * Some daft arches put -1 at the end to indicate its a full trace.
387 * <rant> this is buggy anyway, since it takes a whole extra entry so a
388 * complete trace that maxes out the entries provided will be reported
389 * as incomplete, friggin useless </rant>
391 if (trace->nr_entries != 0 &&
392 trace->entries[trace->nr_entries-1] == ULONG_MAX)
395 trace->max_entries = trace->nr_entries;
397 nr_stack_trace_entries += trace->nr_entries;
399 if (nr_stack_trace_entries >= MAX_STACK_TRACE_ENTRIES-1) {
400 if (!debug_locks_off_graph_unlock())
403 printk("BUG: MAX_STACK_TRACE_ENTRIES too low!\n");
404 printk("turning off the locking correctness validator.\n");
413 unsigned int nr_hardirq_chains;
414 unsigned int nr_softirq_chains;
415 unsigned int nr_process_chains;
416 unsigned int max_lockdep_depth;
418 #ifdef CONFIG_DEBUG_LOCKDEP
420 * We cannot printk in early bootup code. Not even early_printk()
421 * might work. So we mark any initialization errors and printk
422 * about it later on, in lockdep_info().
424 static int lockdep_init_error;
425 static unsigned long lockdep_init_trace_data[20];
426 static struct stack_trace lockdep_init_trace = {
427 .max_entries = ARRAY_SIZE(lockdep_init_trace_data),
428 .entries = lockdep_init_trace_data,
432 * Various lockdep statistics:
434 atomic_t chain_lookup_hits;
435 atomic_t chain_lookup_misses;
436 atomic_t hardirqs_on_events;
437 atomic_t hardirqs_off_events;
438 atomic_t redundant_hardirqs_on;
439 atomic_t redundant_hardirqs_off;
440 atomic_t softirqs_on_events;
441 atomic_t softirqs_off_events;
442 atomic_t redundant_softirqs_on;
443 atomic_t redundant_softirqs_off;
444 atomic_t nr_unused_locks;
445 atomic_t nr_cyclic_checks;
446 atomic_t nr_find_usage_forwards_checks;
447 atomic_t nr_find_usage_backwards_checks;
454 #define __USAGE(__STATE) \
455 [LOCK_USED_IN_##__STATE] = "IN-"__stringify(__STATE)"-W", \
456 [LOCK_ENABLED_##__STATE] = __stringify(__STATE)"-ON-W", \
457 [LOCK_USED_IN_##__STATE##_READ] = "IN-"__stringify(__STATE)"-R",\
458 [LOCK_ENABLED_##__STATE##_READ] = __stringify(__STATE)"-ON-R",
460 static const char *usage_str[] =
462 #define LOCKDEP_STATE(__STATE) __USAGE(__STATE)
463 #include "lockdep_states.h"
465 [LOCK_USED] = "INITIAL USE",
468 const char * __get_key_name(struct lockdep_subclass_key *key, char *str)
470 return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str);
473 static inline unsigned long lock_flag(enum lock_usage_bit bit)
478 static char get_usage_char(struct lock_class *class, enum lock_usage_bit bit)
482 if (class->usage_mask & lock_flag(bit + 2))
484 if (class->usage_mask & lock_flag(bit)) {
486 if (class->usage_mask & lock_flag(bit + 2))
493 void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS])
497 #define LOCKDEP_STATE(__STATE) \
498 usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE); \
499 usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE##_READ);
500 #include "lockdep_states.h"
506 static void print_lock_name(struct lock_class *class)
508 char str[KSYM_NAME_LEN], usage[LOCK_USAGE_CHARS];
511 get_usage_chars(class, usage);
515 name = __get_key_name(class->key, str);
516 printk(" (%s", name);
518 printk(" (%s", name);
519 if (class->name_version > 1)
520 printk("#%d", class->name_version);
522 printk("/%d", class->subclass);
524 printk("){%s}", usage);
527 static void print_lockdep_cache(struct lockdep_map *lock)
530 char str[KSYM_NAME_LEN];
534 name = __get_key_name(lock->key->subkeys, str);
539 static void print_lock(struct held_lock *hlock)
541 print_lock_name(hlock_class(hlock));
543 print_ip_sym(hlock->acquire_ip);
546 static void lockdep_print_held_locks(struct task_struct *curr)
548 int i, depth = curr->lockdep_depth;
551 printk("no locks held by %s/%d.\n", curr->comm, task_pid_nr(curr));
554 printk("%d lock%s held by %s/%d:\n",
555 depth, depth > 1 ? "s" : "", curr->comm, task_pid_nr(curr));
557 for (i = 0; i < depth; i++) {
559 print_lock(curr->held_locks + i);
563 static void print_kernel_version(void)
565 printk("%s %.*s\n", init_utsname()->release,
566 (int)strcspn(init_utsname()->version, " "),
567 init_utsname()->version);
570 static int very_verbose(struct lock_class *class)
573 return class_filter(class);
579 * Is this the address of a static object:
581 static int static_obj(void *obj)
583 unsigned long start = (unsigned long) &_stext,
584 end = (unsigned long) &_end,
585 addr = (unsigned long) obj;
593 if ((addr >= start) && (addr < end))
596 if (arch_is_kernel_data(addr))
603 for_each_possible_cpu(i) {
604 start = (unsigned long) &__per_cpu_start + per_cpu_offset(i);
605 end = (unsigned long) &__per_cpu_start + PERCPU_ENOUGH_ROOM
608 if ((addr >= start) && (addr < end))
616 return is_module_address(addr);
620 * To make lock name printouts unique, we calculate a unique
621 * class->name_version generation counter:
623 static int count_matching_names(struct lock_class *new_class)
625 struct lock_class *class;
628 if (!new_class->name)
631 list_for_each_entry(class, &all_lock_classes, lock_entry) {
632 if (new_class->key - new_class->subclass == class->key)
633 return class->name_version;
634 if (class->name && !strcmp(class->name, new_class->name))
635 count = max(count, class->name_version);
642 * Register a lock's class in the hash-table, if the class is not present
643 * yet. Otherwise we look it up. We cache the result in the lock object
644 * itself, so actual lookup of the hash should be once per lock object.
646 static inline struct lock_class *
647 look_up_lock_class(struct lockdep_map *lock, unsigned int subclass)
649 struct lockdep_subclass_key *key;
650 struct list_head *hash_head;
651 struct lock_class *class;
653 #ifdef CONFIG_DEBUG_LOCKDEP
655 * If the architecture calls into lockdep before initializing
656 * the hashes then we'll warn about it later. (we cannot printk
659 if (unlikely(!lockdep_initialized)) {
661 lockdep_init_error = 1;
662 save_stack_trace(&lockdep_init_trace);
667 * Static locks do not have their class-keys yet - for them the key
668 * is the lock object itself:
670 if (unlikely(!lock->key))
671 lock->key = (void *)lock;
674 * NOTE: the class-key must be unique. For dynamic locks, a static
675 * lock_class_key variable is passed in through the mutex_init()
676 * (or spin_lock_init()) call - which acts as the key. For static
677 * locks we use the lock object itself as the key.
679 BUILD_BUG_ON(sizeof(struct lock_class_key) >
680 sizeof(struct lockdep_map));
682 key = lock->key->subkeys + subclass;
684 hash_head = classhashentry(key);
687 * We can walk the hash lockfree, because the hash only
688 * grows, and we are careful when adding entries to the end:
690 list_for_each_entry(class, hash_head, hash_entry) {
691 if (class->key == key) {
692 WARN_ON_ONCE(class->name != lock->name);
701 * Register a lock's class in the hash-table, if the class is not present
702 * yet. Otherwise we look it up. We cache the result in the lock object
703 * itself, so actual lookup of the hash should be once per lock object.
705 static inline struct lock_class *
706 register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
708 struct lockdep_subclass_key *key;
709 struct list_head *hash_head;
710 struct lock_class *class;
713 class = look_up_lock_class(lock, subclass);
718 * Debug-check: all keys must be persistent!
720 if (!static_obj(lock->key)) {
722 printk("INFO: trying to register non-static key.\n");
723 printk("the code is fine but needs lockdep annotation.\n");
724 printk("turning off the locking correctness validator.\n");
730 key = lock->key->subkeys + subclass;
731 hash_head = classhashentry(key);
733 raw_local_irq_save(flags);
735 raw_local_irq_restore(flags);
739 * We have to do the hash-walk again, to avoid races
742 list_for_each_entry(class, hash_head, hash_entry)
743 if (class->key == key)
746 * Allocate a new key from the static array, and add it to
749 if (nr_lock_classes >= MAX_LOCKDEP_KEYS) {
750 if (!debug_locks_off_graph_unlock()) {
751 raw_local_irq_restore(flags);
754 raw_local_irq_restore(flags);
756 printk("BUG: MAX_LOCKDEP_KEYS too low!\n");
757 printk("turning off the locking correctness validator.\n");
761 class = lock_classes + nr_lock_classes++;
762 debug_atomic_inc(&nr_unused_locks);
764 class->name = lock->name;
765 class->subclass = subclass;
766 INIT_LIST_HEAD(&class->lock_entry);
767 INIT_LIST_HEAD(&class->locks_before);
768 INIT_LIST_HEAD(&class->locks_after);
769 class->name_version = count_matching_names(class);
771 * We use RCU's safe list-add method to make
772 * parallel walking of the hash-list safe:
774 list_add_tail_rcu(&class->hash_entry, hash_head);
776 * Add it to the global list of classes:
778 list_add_tail_rcu(&class->lock_entry, &all_lock_classes);
780 if (verbose(class)) {
782 raw_local_irq_restore(flags);
784 printk("\nnew class %p: %s", class->key, class->name);
785 if (class->name_version > 1)
786 printk("#%d", class->name_version);
790 raw_local_irq_save(flags);
792 raw_local_irq_restore(flags);
798 raw_local_irq_restore(flags);
800 if (!subclass || force)
801 lock->class_cache = class;
803 if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))
809 #ifdef CONFIG_PROVE_LOCKING
811 * Allocate a lockdep entry. (assumes the graph_lock held, returns
812 * with NULL on failure)
814 static struct lock_list *alloc_list_entry(void)
816 if (nr_list_entries >= MAX_LOCKDEP_ENTRIES) {
817 if (!debug_locks_off_graph_unlock())
820 printk("BUG: MAX_LOCKDEP_ENTRIES too low!\n");
821 printk("turning off the locking correctness validator.\n");
825 return list_entries + nr_list_entries++;
829 * Add a new dependency to the head of the list:
831 static int add_lock_to_list(struct lock_class *class, struct lock_class *this,
832 struct list_head *head, unsigned long ip, int distance)
834 struct lock_list *entry;
836 * Lock not present yet - get a new dependency struct and
837 * add it to the list:
839 entry = alloc_list_entry();
843 if (!save_trace(&entry->trace))
847 entry->distance = distance;
849 * Since we never remove from the dependency list, the list can
850 * be walked lockless by other CPUs, it's only allocation
851 * that must be protected by the spinlock. But this also means
852 * we must make new entries visible only once writes to the
853 * entry become visible - hence the RCU op:
855 list_add_tail_rcu(&entry->entry, head);
861 * For good efficiency of modular, we use power of 2
863 #define MAX_CIRCULAR_QUEUE_SIZE 4096UL
864 #define CQ_MASK (MAX_CIRCULAR_QUEUE_SIZE-1)
867 * The circular_queue and helpers is used to implement the
868 * breadth-first search(BFS)algorithem, by which we can build
869 * the shortest path from the next lock to be acquired to the
870 * previous held lock if there is a circular between them.
872 struct circular_queue {
873 unsigned long element[MAX_CIRCULAR_QUEUE_SIZE];
874 unsigned int front, rear;
877 static struct circular_queue lock_cq;
879 unsigned int max_bfs_queue_depth;
881 static unsigned int lockdep_dependency_gen_id;
883 static inline void __cq_init(struct circular_queue *cq)
885 cq->front = cq->rear = 0;
886 lockdep_dependency_gen_id++;
889 static inline int __cq_empty(struct circular_queue *cq)
891 return (cq->front == cq->rear);
894 static inline int __cq_full(struct circular_queue *cq)
896 return ((cq->rear + 1) & CQ_MASK) == cq->front;
899 static inline int __cq_enqueue(struct circular_queue *cq, unsigned long elem)
904 cq->element[cq->rear] = elem;
905 cq->rear = (cq->rear + 1) & CQ_MASK;
909 static inline int __cq_dequeue(struct circular_queue *cq, unsigned long *elem)
914 *elem = cq->element[cq->front];
915 cq->front = (cq->front + 1) & CQ_MASK;
919 static inline unsigned int __cq_get_elem_count(struct circular_queue *cq)
921 return (cq->rear - cq->front) & CQ_MASK;
924 static inline void mark_lock_accessed(struct lock_list *lock,
925 struct lock_list *parent)
929 nr = lock - list_entries;
930 WARN_ON(nr >= nr_list_entries);
931 lock->parent = parent;
932 lock->class->dep_gen_id = lockdep_dependency_gen_id;
935 static inline unsigned long lock_accessed(struct lock_list *lock)
939 nr = lock - list_entries;
940 WARN_ON(nr >= nr_list_entries);
941 return lock->class->dep_gen_id == lockdep_dependency_gen_id;
944 static inline struct lock_list *get_lock_parent(struct lock_list *child)
946 return child->parent;
949 static inline int get_lock_depth(struct lock_list *child)
952 struct lock_list *parent;
954 while ((parent = get_lock_parent(child))) {
961 static int __bfs(struct lock_list *source_entry,
963 int (*match)(struct lock_list *entry, void *data),
964 struct lock_list **target_entry,
967 struct lock_list *entry;
968 struct list_head *head;
969 struct circular_queue *cq = &lock_cq;
972 if (match(source_entry, data)) {
973 *target_entry = source_entry;
979 head = &source_entry->class->locks_after;
981 head = &source_entry->class->locks_before;
983 if (list_empty(head))
987 __cq_enqueue(cq, (unsigned long)source_entry);
989 while (!__cq_empty(cq)) {
990 struct lock_list *lock;
992 __cq_dequeue(cq, (unsigned long *)&lock);
1000 head = &lock->class->locks_after;
1002 head = &lock->class->locks_before;
1004 list_for_each_entry(entry, head, entry) {
1005 if (!lock_accessed(entry)) {
1006 unsigned int cq_depth;
1007 mark_lock_accessed(entry, lock);
1008 if (match(entry, data)) {
1009 *target_entry = entry;
1014 if (__cq_enqueue(cq, (unsigned long)entry)) {
1018 cq_depth = __cq_get_elem_count(cq);
1019 if (max_bfs_queue_depth < cq_depth)
1020 max_bfs_queue_depth = cq_depth;
1028 static inline int __bfs_forwards(struct lock_list *src_entry,
1030 int (*match)(struct lock_list *entry, void *data),
1031 struct lock_list **target_entry)
1033 return __bfs(src_entry, data, match, target_entry, 1);
1037 static inline int __bfs_backwards(struct lock_list *src_entry,
1039 int (*match)(struct lock_list *entry, void *data),
1040 struct lock_list **target_entry)
1042 return __bfs(src_entry, data, match, target_entry, 0);
1047 * Recursive, forwards-direction lock-dependency checking, used for
1048 * both noncyclic checking and for hardirq-unsafe/softirq-unsafe
1053 * Print a dependency chain entry (this is only done when a deadlock
1054 * has been detected):
1057 print_circular_bug_entry(struct lock_list *target, int depth)
1059 if (debug_locks_silent)
1061 printk("\n-> #%u", depth);
1062 print_lock_name(target->class);
1064 print_stack_trace(&target->trace, 6);
1070 * When a circular dependency is detected, print the
1074 print_circular_bug_header(struct lock_list *entry, unsigned int depth,
1075 struct held_lock *check_src,
1076 struct held_lock *check_tgt)
1078 struct task_struct *curr = current;
1080 if (debug_locks_silent)
1083 printk("\n=======================================================\n");
1084 printk( "[ INFO: possible circular locking dependency detected ]\n");
1085 print_kernel_version();
1086 printk( "-------------------------------------------------------\n");
1087 printk("%s/%d is trying to acquire lock:\n",
1088 curr->comm, task_pid_nr(curr));
1089 print_lock(check_src);
1090 printk("\nbut task is already holding lock:\n");
1091 print_lock(check_tgt);
1092 printk("\nwhich lock already depends on the new lock.\n\n");
1093 printk("\nthe existing dependency chain (in reverse order) is:\n");
1095 print_circular_bug_entry(entry, depth);
1100 static inline int class_equal(struct lock_list *entry, void *data)
1102 return entry->class == data;
1105 static noinline int print_circular_bug(struct lock_list *this,
1106 struct lock_list *target,
1107 struct held_lock *check_src,
1108 struct held_lock *check_tgt)
1110 struct task_struct *curr = current;
1111 struct lock_list *parent;
1114 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1117 if (!save_trace(&this->trace))
1120 depth = get_lock_depth(target);
1122 print_circular_bug_header(target, depth, check_src, check_tgt);
1124 parent = get_lock_parent(target);
1127 print_circular_bug_entry(parent, --depth);
1128 parent = get_lock_parent(parent);
1131 printk("\nother info that might help us debug this:\n\n");
1132 lockdep_print_held_locks(curr);
1134 printk("\nstack backtrace:\n");
1140 static noinline int print_bfs_bug(int ret)
1142 if (!debug_locks_off_graph_unlock())
1145 WARN(1, "lockdep bfs error:%d\n", ret);
1150 static int noop_count(struct lock_list *entry, void *data)
1152 (*(unsigned long *)data)++;
1156 unsigned long __lockdep_count_forward_deps(struct lock_list *this)
1158 unsigned long count = 0;
1159 struct lock_list *uninitialized_var(target_entry);
1161 __bfs_forwards(this, (void *)&count, noop_count, &target_entry);
1165 unsigned long lockdep_count_forward_deps(struct lock_class *class)
1167 unsigned long ret, flags;
1168 struct lock_list this;
1173 local_irq_save(flags);
1174 arch_spin_lock(&lockdep_lock);
1175 ret = __lockdep_count_forward_deps(&this);
1176 arch_spin_unlock(&lockdep_lock);
1177 local_irq_restore(flags);
1182 unsigned long __lockdep_count_backward_deps(struct lock_list *this)
1184 unsigned long count = 0;
1185 struct lock_list *uninitialized_var(target_entry);
1187 __bfs_backwards(this, (void *)&count, noop_count, &target_entry);
1192 unsigned long lockdep_count_backward_deps(struct lock_class *class)
1194 unsigned long ret, flags;
1195 struct lock_list this;
1200 local_irq_save(flags);
1201 arch_spin_lock(&lockdep_lock);
1202 ret = __lockdep_count_backward_deps(&this);
1203 arch_spin_unlock(&lockdep_lock);
1204 local_irq_restore(flags);
1210 * Prove that the dependency graph starting at <entry> can not
1211 * lead to <target>. Print an error and return 0 if it does.
1214 check_noncircular(struct lock_list *root, struct lock_class *target,
1215 struct lock_list **target_entry)
1219 debug_atomic_inc(&nr_cyclic_checks);
1221 result = __bfs_forwards(root, target, class_equal, target_entry);
1226 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
1228 * Forwards and backwards subgraph searching, for the purposes of
1229 * proving that two subgraphs can be connected by a new dependency
1230 * without creating any illegal irq-safe -> irq-unsafe lock dependency.
1233 static inline int usage_match(struct lock_list *entry, void *bit)
1235 return entry->class->usage_mask & (1 << (enum lock_usage_bit)bit);
1241 * Find a node in the forwards-direction dependency sub-graph starting
1242 * at @root->class that matches @bit.
1244 * Return 0 if such a node exists in the subgraph, and put that node
1245 * into *@target_entry.
1247 * Return 1 otherwise and keep *@target_entry unchanged.
1248 * Return <0 on error.
1251 find_usage_forwards(struct lock_list *root, enum lock_usage_bit bit,
1252 struct lock_list **target_entry)
1256 debug_atomic_inc(&nr_find_usage_forwards_checks);
1258 result = __bfs_forwards(root, (void *)bit, usage_match, target_entry);
1264 * Find a node in the backwards-direction dependency sub-graph starting
1265 * at @root->class that matches @bit.
1267 * Return 0 if such a node exists in the subgraph, and put that node
1268 * into *@target_entry.
1270 * Return 1 otherwise and keep *@target_entry unchanged.
1271 * Return <0 on error.
1274 find_usage_backwards(struct lock_list *root, enum lock_usage_bit bit,
1275 struct lock_list **target_entry)
1279 debug_atomic_inc(&nr_find_usage_backwards_checks);
1281 result = __bfs_backwards(root, (void *)bit, usage_match, target_entry);
1286 static void print_lock_class_header(struct lock_class *class, int depth)
1290 printk("%*s->", depth, "");
1291 print_lock_name(class);
1292 printk(" ops: %lu", class->ops);
1295 for (bit = 0; bit < LOCK_USAGE_STATES; bit++) {
1296 if (class->usage_mask & (1 << bit)) {
1299 len += printk("%*s %s", depth, "", usage_str[bit]);
1300 len += printk(" at:\n");
1301 print_stack_trace(class->usage_traces + bit, len);
1304 printk("%*s }\n", depth, "");
1306 printk("%*s ... key at: ",depth,"");
1307 print_ip_sym((unsigned long)class->key);
1311 * printk the shortest lock dependencies from @start to @end in reverse order:
1314 print_shortest_lock_dependencies(struct lock_list *leaf,
1315 struct lock_list *root)
1317 struct lock_list *entry = leaf;
1320 /*compute depth from generated tree by BFS*/
1321 depth = get_lock_depth(leaf);
1324 print_lock_class_header(entry->class, depth);
1325 printk("%*s ... acquired at:\n", depth, "");
1326 print_stack_trace(&entry->trace, 2);
1329 if (depth == 0 && (entry != root)) {
1330 printk("lockdep:%s bad BFS generated tree\n", __func__);
1334 entry = get_lock_parent(entry);
1336 } while (entry && (depth >= 0));
1342 print_bad_irq_dependency(struct task_struct *curr,
1343 struct lock_list *prev_root,
1344 struct lock_list *next_root,
1345 struct lock_list *backwards_entry,
1346 struct lock_list *forwards_entry,
1347 struct held_lock *prev,
1348 struct held_lock *next,
1349 enum lock_usage_bit bit1,
1350 enum lock_usage_bit bit2,
1351 const char *irqclass)
1353 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1356 printk("\n======================================================\n");
1357 printk( "[ INFO: %s-safe -> %s-unsafe lock order detected ]\n",
1358 irqclass, irqclass);
1359 print_kernel_version();
1360 printk( "------------------------------------------------------\n");
1361 printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
1362 curr->comm, task_pid_nr(curr),
1363 curr->hardirq_context, hardirq_count() >> HARDIRQ_SHIFT,
1364 curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT,
1365 curr->hardirqs_enabled,
1366 curr->softirqs_enabled);
1369 printk("\nand this task is already holding:\n");
1371 printk("which would create a new lock dependency:\n");
1372 print_lock_name(hlock_class(prev));
1374 print_lock_name(hlock_class(next));
1377 printk("\nbut this new dependency connects a %s-irq-safe lock:\n",
1379 print_lock_name(backwards_entry->class);
1380 printk("\n... which became %s-irq-safe at:\n", irqclass);
1382 print_stack_trace(backwards_entry->class->usage_traces + bit1, 1);
1384 printk("\nto a %s-irq-unsafe lock:\n", irqclass);
1385 print_lock_name(forwards_entry->class);
1386 printk("\n... which became %s-irq-unsafe at:\n", irqclass);
1389 print_stack_trace(forwards_entry->class->usage_traces + bit2, 1);
1391 printk("\nother info that might help us debug this:\n\n");
1392 lockdep_print_held_locks(curr);
1394 printk("\nthe dependencies between %s-irq-safe lock", irqclass);
1395 printk(" and the holding lock:\n");
1396 if (!save_trace(&prev_root->trace))
1398 print_shortest_lock_dependencies(backwards_entry, prev_root);
1400 printk("\nthe dependencies between the lock to be acquired");
1401 printk(" and %s-irq-unsafe lock:\n", irqclass);
1402 if (!save_trace(&next_root->trace))
1404 print_shortest_lock_dependencies(forwards_entry, next_root);
1406 printk("\nstack backtrace:\n");
1413 check_usage(struct task_struct *curr, struct held_lock *prev,
1414 struct held_lock *next, enum lock_usage_bit bit_backwards,
1415 enum lock_usage_bit bit_forwards, const char *irqclass)
1418 struct lock_list this, that;
1419 struct lock_list *uninitialized_var(target_entry);
1420 struct lock_list *uninitialized_var(target_entry1);
1424 this.class = hlock_class(prev);
1425 ret = find_usage_backwards(&this, bit_backwards, &target_entry);
1427 return print_bfs_bug(ret);
1432 that.class = hlock_class(next);
1433 ret = find_usage_forwards(&that, bit_forwards, &target_entry1);
1435 return print_bfs_bug(ret);
1439 return print_bad_irq_dependency(curr, &this, &that,
1440 target_entry, target_entry1,
1442 bit_backwards, bit_forwards, irqclass);
1445 static const char *state_names[] = {
1446 #define LOCKDEP_STATE(__STATE) \
1447 __stringify(__STATE),
1448 #include "lockdep_states.h"
1449 #undef LOCKDEP_STATE
1452 static const char *state_rnames[] = {
1453 #define LOCKDEP_STATE(__STATE) \
1454 __stringify(__STATE)"-READ",
1455 #include "lockdep_states.h"
1456 #undef LOCKDEP_STATE
1459 static inline const char *state_name(enum lock_usage_bit bit)
1461 return (bit & 1) ? state_rnames[bit >> 2] : state_names[bit >> 2];
1464 static int exclusive_bit(int new_bit)
1472 * bit 0 - write/read
1473 * bit 1 - used_in/enabled
1477 int state = new_bit & ~3;
1478 int dir = new_bit & 2;
1481 * keep state, bit flip the direction and strip read.
1483 return state | (dir ^ 2);
1486 static int check_irq_usage(struct task_struct *curr, struct held_lock *prev,
1487 struct held_lock *next, enum lock_usage_bit bit)
1490 * Prove that the new dependency does not connect a hardirq-safe
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)))
1502 * Prove that the new dependency does not connect a hardirq-safe-read
1503 * lock with a hardirq-unsafe lock - to achieve this we search
1504 * the backwards-subgraph starting at <prev>, and the
1505 * forwards-subgraph starting at <next>:
1507 if (!check_usage(curr, prev, next, bit,
1508 exclusive_bit(bit), state_name(bit)))
1515 check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
1516 struct held_lock *next)
1518 #define LOCKDEP_STATE(__STATE) \
1519 if (!check_irq_usage(curr, prev, next, LOCK_USED_IN_##__STATE)) \
1521 #include "lockdep_states.h"
1522 #undef LOCKDEP_STATE
1527 static void inc_chains(void)
1529 if (current->hardirq_context)
1530 nr_hardirq_chains++;
1532 if (current->softirq_context)
1533 nr_softirq_chains++;
1535 nr_process_chains++;
1542 check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
1543 struct held_lock *next)
1548 static inline void inc_chains(void)
1550 nr_process_chains++;
1556 print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
1557 struct held_lock *next)
1559 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1562 printk("\n=============================================\n");
1563 printk( "[ INFO: possible recursive locking detected ]\n");
1564 print_kernel_version();
1565 printk( "---------------------------------------------\n");
1566 printk("%s/%d is trying to acquire lock:\n",
1567 curr->comm, task_pid_nr(curr));
1569 printk("\nbut task is already holding lock:\n");
1572 printk("\nother info that might help us debug this:\n");
1573 lockdep_print_held_locks(curr);
1575 printk("\nstack backtrace:\n");
1582 * Check whether we are holding such a class already.
1584 * (Note that this has to be done separately, because the graph cannot
1585 * detect such classes of deadlocks.)
1587 * Returns: 0 on deadlock detected, 1 on OK, 2 on recursive read
1590 check_deadlock(struct task_struct *curr, struct held_lock *next,
1591 struct lockdep_map *next_instance, int read)
1593 struct held_lock *prev;
1594 struct held_lock *nest = NULL;
1597 for (i = 0; i < curr->lockdep_depth; i++) {
1598 prev = curr->held_locks + i;
1600 if (prev->instance == next->nest_lock)
1603 if (hlock_class(prev) != hlock_class(next))
1607 * Allow read-after-read recursion of the same
1608 * lock class (i.e. read_lock(lock)+read_lock(lock)):
1610 if ((read == 2) && prev->read)
1614 * We're holding the nest_lock, which serializes this lock's
1615 * nesting behaviour.
1620 return print_deadlock_bug(curr, prev, next);
1626 * There was a chain-cache miss, and we are about to add a new dependency
1627 * to a previous lock. We recursively validate the following rules:
1629 * - would the adding of the <prev> -> <next> dependency create a
1630 * circular dependency in the graph? [== circular deadlock]
1632 * - does the new prev->next dependency connect any hardirq-safe lock
1633 * (in the full backwards-subgraph starting at <prev>) with any
1634 * hardirq-unsafe lock (in the full forwards-subgraph starting at
1635 * <next>)? [== illegal lock inversion with hardirq contexts]
1637 * - does the new prev->next dependency connect any softirq-safe lock
1638 * (in the full backwards-subgraph starting at <prev>) with any
1639 * softirq-unsafe lock (in the full forwards-subgraph starting at
1640 * <next>)? [== illegal lock inversion with softirq contexts]
1642 * any of these scenarios could lead to a deadlock.
1644 * Then if all the validations pass, we add the forwards and backwards
1648 check_prev_add(struct task_struct *curr, struct held_lock *prev,
1649 struct held_lock *next, int distance)
1651 struct lock_list *entry;
1653 struct lock_list this;
1654 struct lock_list *uninitialized_var(target_entry);
1657 * Prove that the new <prev> -> <next> dependency would not
1658 * create a circular dependency in the graph. (We do this by
1659 * forward-recursing into the graph starting at <next>, and
1660 * checking whether we can reach <prev>.)
1662 * We are using global variables to control the recursion, to
1663 * keep the stackframe size of the recursive functions low:
1665 this.class = hlock_class(next);
1667 ret = check_noncircular(&this, hlock_class(prev), &target_entry);
1669 return print_circular_bug(&this, target_entry, next, prev);
1670 else if (unlikely(ret < 0))
1671 return print_bfs_bug(ret);
1673 if (!check_prev_add_irq(curr, prev, next))
1677 * For recursive read-locks we do all the dependency checks,
1678 * but we dont store read-triggered dependencies (only
1679 * write-triggered dependencies). This ensures that only the
1680 * write-side dependencies matter, and that if for example a
1681 * write-lock never takes any other locks, then the reads are
1682 * equivalent to a NOP.
1684 if (next->read == 2 || prev->read == 2)
1687 * Is the <prev> -> <next> dependency already present?
1689 * (this may occur even though this is a new chain: consider
1690 * e.g. the L1 -> L2 -> L3 -> L4 and the L5 -> L1 -> L2 -> L3
1691 * chains - the second one will be new, but L1 already has
1692 * L2 added to its dependency list, due to the first chain.)
1694 list_for_each_entry(entry, &hlock_class(prev)->locks_after, entry) {
1695 if (entry->class == hlock_class(next)) {
1697 entry->distance = 1;
1703 * Ok, all validations passed, add the new lock
1704 * to the previous lock's dependency list:
1706 ret = add_lock_to_list(hlock_class(prev), hlock_class(next),
1707 &hlock_class(prev)->locks_after,
1708 next->acquire_ip, distance);
1713 ret = add_lock_to_list(hlock_class(next), hlock_class(prev),
1714 &hlock_class(next)->locks_before,
1715 next->acquire_ip, distance);
1720 * Debugging printouts:
1722 if (verbose(hlock_class(prev)) || verbose(hlock_class(next))) {
1724 printk("\n new dependency: ");
1725 print_lock_name(hlock_class(prev));
1727 print_lock_name(hlock_class(next));
1730 return graph_lock();
1736 * Add the dependency to all directly-previous locks that are 'relevant'.
1737 * The ones that are relevant are (in increasing distance from curr):
1738 * all consecutive trylock entries and the final non-trylock entry - or
1739 * the end of this context's lock-chain - whichever comes first.
1742 check_prevs_add(struct task_struct *curr, struct held_lock *next)
1744 int depth = curr->lockdep_depth;
1745 struct held_lock *hlock;
1750 * Depth must not be zero for a non-head lock:
1755 * At least two relevant locks must exist for this
1758 if (curr->held_locks[depth].irq_context !=
1759 curr->held_locks[depth-1].irq_context)
1763 int distance = curr->lockdep_depth - depth + 1;
1764 hlock = curr->held_locks + depth-1;
1766 * Only non-recursive-read entries get new dependencies
1769 if (hlock->read != 2) {
1770 if (!check_prev_add(curr, hlock, next, distance))
1773 * Stop after the first non-trylock entry,
1774 * as non-trylock entries have added their
1775 * own direct dependencies already, so this
1776 * lock is connected to them indirectly:
1778 if (!hlock->trylock)
1783 * End of lock-stack?
1788 * Stop the search if we cross into another context:
1790 if (curr->held_locks[depth].irq_context !=
1791 curr->held_locks[depth-1].irq_context)
1796 if (!debug_locks_off_graph_unlock())
1804 unsigned long nr_lock_chains;
1805 struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
1806 int nr_chain_hlocks;
1807 static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
1809 struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
1811 return lock_classes + chain_hlocks[chain->base + i];
1815 * Look up a dependency chain. If the key is not present yet then
1816 * add it and return 1 - in this case the new dependency chain is
1817 * validated. If the key is already hashed, return 0.
1818 * (On return with 1 graph_lock is held.)
1820 static inline int lookup_chain_cache(struct task_struct *curr,
1821 struct held_lock *hlock,
1824 struct lock_class *class = hlock_class(hlock);
1825 struct list_head *hash_head = chainhashentry(chain_key);
1826 struct lock_chain *chain;
1827 struct held_lock *hlock_curr, *hlock_next;
1830 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
1833 * We can walk it lock-free, because entries only get added
1836 list_for_each_entry(chain, hash_head, entry) {
1837 if (chain->chain_key == chain_key) {
1839 debug_atomic_inc(&chain_lookup_hits);
1840 if (very_verbose(class))
1841 printk("\nhash chain already cached, key: "
1842 "%016Lx tail class: [%p] %s\n",
1843 (unsigned long long)chain_key,
1844 class->key, class->name);
1848 if (very_verbose(class))
1849 printk("\nnew hash chain, key: %016Lx tail class: [%p] %s\n",
1850 (unsigned long long)chain_key, class->key, class->name);
1852 * Allocate a new chain entry from the static array, and add
1858 * We have to walk the chain again locked - to avoid duplicates:
1860 list_for_each_entry(chain, hash_head, entry) {
1861 if (chain->chain_key == chain_key) {
1866 if (unlikely(nr_lock_chains >= MAX_LOCKDEP_CHAINS)) {
1867 if (!debug_locks_off_graph_unlock())
1870 printk("BUG: MAX_LOCKDEP_CHAINS too low!\n");
1871 printk("turning off the locking correctness validator.\n");
1875 chain = lock_chains + nr_lock_chains++;
1876 chain->chain_key = chain_key;
1877 chain->irq_context = hlock->irq_context;
1878 /* Find the first held_lock of current chain */
1880 for (i = curr->lockdep_depth - 1; i >= 0; i--) {
1881 hlock_curr = curr->held_locks + i;
1882 if (hlock_curr->irq_context != hlock_next->irq_context)
1887 chain->depth = curr->lockdep_depth + 1 - i;
1888 cn = nr_chain_hlocks;
1889 while (cn + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS) {
1890 n = cmpxchg(&nr_chain_hlocks, cn, cn + chain->depth);
1895 if (likely(cn + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) {
1897 for (j = 0; j < chain->depth - 1; j++, i++) {
1898 int lock_id = curr->held_locks[i].class_idx - 1;
1899 chain_hlocks[chain->base + j] = lock_id;
1901 chain_hlocks[chain->base + j] = class - lock_classes;
1903 list_add_tail_rcu(&chain->entry, hash_head);
1904 debug_atomic_inc(&chain_lookup_misses);
1910 static int validate_chain(struct task_struct *curr, struct lockdep_map *lock,
1911 struct held_lock *hlock, int chain_head, u64 chain_key)
1914 * Trylock needs to maintain the stack of held locks, but it
1915 * does not add new dependencies, because trylock can be done
1918 * We look up the chain_key and do the O(N^2) check and update of
1919 * the dependencies only if this is a new dependency chain.
1920 * (If lookup_chain_cache() returns with 1 it acquires
1921 * graph_lock for us)
1923 if (!hlock->trylock && (hlock->check == 2) &&
1924 lookup_chain_cache(curr, hlock, chain_key)) {
1926 * Check whether last held lock:
1928 * - is irq-safe, if this lock is irq-unsafe
1929 * - is softirq-safe, if this lock is hardirq-unsafe
1931 * And check whether the new lock's dependency graph
1932 * could lead back to the previous lock.
1934 * any of these scenarios could lead to a deadlock. If
1937 int ret = check_deadlock(curr, hlock, lock, hlock->read);
1942 * Mark recursive read, as we jump over it when
1943 * building dependencies (just like we jump over
1949 * Add dependency only if this lock is not the head
1950 * of the chain, and if it's not a secondary read-lock:
1952 if (!chain_head && ret != 2)
1953 if (!check_prevs_add(curr, hlock))
1957 /* after lookup_chain_cache(): */
1958 if (unlikely(!debug_locks))
1964 static inline int validate_chain(struct task_struct *curr,
1965 struct lockdep_map *lock, struct held_lock *hlock,
1966 int chain_head, u64 chain_key)
1973 * We are building curr_chain_key incrementally, so double-check
1974 * it from scratch, to make sure that it's done correctly:
1976 static void check_chain_key(struct task_struct *curr)
1978 #ifdef CONFIG_DEBUG_LOCKDEP
1979 struct held_lock *hlock, *prev_hlock = NULL;
1983 for (i = 0; i < curr->lockdep_depth; i++) {
1984 hlock = curr->held_locks + i;
1985 if (chain_key != hlock->prev_chain_key) {
1987 WARN(1, "hm#1, depth: %u [%u], %016Lx != %016Lx\n",
1988 curr->lockdep_depth, i,
1989 (unsigned long long)chain_key,
1990 (unsigned long long)hlock->prev_chain_key);
1993 id = hlock->class_idx - 1;
1994 if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
1997 if (prev_hlock && (prev_hlock->irq_context !=
1998 hlock->irq_context))
2000 chain_key = iterate_chain_key(chain_key, id);
2003 if (chain_key != curr->curr_chain_key) {
2005 WARN(1, "hm#2, depth: %u [%u], %016Lx != %016Lx\n",
2006 curr->lockdep_depth, i,
2007 (unsigned long long)chain_key,
2008 (unsigned long long)curr->curr_chain_key);
2014 print_usage_bug(struct task_struct *curr, struct held_lock *this,
2015 enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
2017 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2020 printk("\n=================================\n");
2021 printk( "[ INFO: inconsistent lock state ]\n");
2022 print_kernel_version();
2023 printk( "---------------------------------\n");
2025 printk("inconsistent {%s} -> {%s} usage.\n",
2026 usage_str[prev_bit], usage_str[new_bit]);
2028 printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] takes:\n",
2029 curr->comm, task_pid_nr(curr),
2030 trace_hardirq_context(curr), hardirq_count() >> HARDIRQ_SHIFT,
2031 trace_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT,
2032 trace_hardirqs_enabled(curr),
2033 trace_softirqs_enabled(curr));
2036 printk("{%s} state was registered at:\n", usage_str[prev_bit]);
2037 print_stack_trace(hlock_class(this)->usage_traces + prev_bit, 1);
2039 print_irqtrace_events(curr);
2040 printk("\nother info that might help us debug this:\n");
2041 lockdep_print_held_locks(curr);
2043 printk("\nstack backtrace:\n");
2050 * Print out an error if an invalid bit is set:
2053 valid_state(struct task_struct *curr, struct held_lock *this,
2054 enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit)
2056 if (unlikely(hlock_class(this)->usage_mask & (1 << bad_bit)))
2057 return print_usage_bug(curr, this, bad_bit, new_bit);
2061 static int mark_lock(struct task_struct *curr, struct held_lock *this,
2062 enum lock_usage_bit new_bit);
2064 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
2067 * print irq inversion bug:
2070 print_irq_inversion_bug(struct task_struct *curr,
2071 struct lock_list *root, struct lock_list *other,
2072 struct held_lock *this, int forwards,
2073 const char *irqclass)
2075 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2078 printk("\n=========================================================\n");
2079 printk( "[ INFO: possible irq lock inversion dependency detected ]\n");
2080 print_kernel_version();
2081 printk( "---------------------------------------------------------\n");
2082 printk("%s/%d just changed the state of lock:\n",
2083 curr->comm, task_pid_nr(curr));
2086 printk("but this lock took another, %s-unsafe lock in the past:\n", irqclass);
2088 printk("but this lock was taken by another, %s-safe lock in the past:\n", irqclass);
2089 print_lock_name(other->class);
2090 printk("\n\nand interrupts could create inverse lock ordering between them.\n\n");
2092 printk("\nother info that might help us debug this:\n");
2093 lockdep_print_held_locks(curr);
2095 printk("\nthe shortest dependencies between 2nd lock and 1st lock:\n");
2096 if (!save_trace(&root->trace))
2098 print_shortest_lock_dependencies(other, root);
2100 printk("\nstack backtrace:\n");
2107 * Prove that in the forwards-direction subgraph starting at <this>
2108 * there is no lock matching <mask>:
2111 check_usage_forwards(struct task_struct *curr, struct held_lock *this,
2112 enum lock_usage_bit bit, const char *irqclass)
2115 struct lock_list root;
2116 struct lock_list *uninitialized_var(target_entry);
2119 root.class = hlock_class(this);
2120 ret = find_usage_forwards(&root, bit, &target_entry);
2122 return print_bfs_bug(ret);
2126 return print_irq_inversion_bug(curr, &root, target_entry,
2131 * Prove that in the backwards-direction subgraph starting at <this>
2132 * there is no lock matching <mask>:
2135 check_usage_backwards(struct task_struct *curr, struct held_lock *this,
2136 enum lock_usage_bit bit, const char *irqclass)
2139 struct lock_list root;
2140 struct lock_list *uninitialized_var(target_entry);
2143 root.class = hlock_class(this);
2144 ret = find_usage_backwards(&root, bit, &target_entry);
2146 return print_bfs_bug(ret);
2150 return print_irq_inversion_bug(curr, &root, target_entry,
2154 void print_irqtrace_events(struct task_struct *curr)
2156 printk("irq event stamp: %u\n", curr->irq_events);
2157 printk("hardirqs last enabled at (%u): ", curr->hardirq_enable_event);
2158 print_ip_sym(curr->hardirq_enable_ip);
2159 printk("hardirqs last disabled at (%u): ", curr->hardirq_disable_event);
2160 print_ip_sym(curr->hardirq_disable_ip);
2161 printk("softirqs last enabled at (%u): ", curr->softirq_enable_event);
2162 print_ip_sym(curr->softirq_enable_ip);
2163 printk("softirqs last disabled at (%u): ", curr->softirq_disable_event);
2164 print_ip_sym(curr->softirq_disable_ip);
2167 static int HARDIRQ_verbose(struct lock_class *class)
2170 return class_filter(class);
2175 static int SOFTIRQ_verbose(struct lock_class *class)
2178 return class_filter(class);
2183 static int RECLAIM_FS_verbose(struct lock_class *class)
2186 return class_filter(class);
2191 #define STRICT_READ_CHECKS 1
2193 static int (*state_verbose_f[])(struct lock_class *class) = {
2194 #define LOCKDEP_STATE(__STATE) \
2196 #include "lockdep_states.h"
2197 #undef LOCKDEP_STATE
2200 static inline int state_verbose(enum lock_usage_bit bit,
2201 struct lock_class *class)
2203 return state_verbose_f[bit >> 2](class);
2206 typedef int (*check_usage_f)(struct task_struct *, struct held_lock *,
2207 enum lock_usage_bit bit, const char *name);
2210 mark_lock_irq(struct task_struct *curr, struct held_lock *this,
2211 enum lock_usage_bit new_bit)
2213 int excl_bit = exclusive_bit(new_bit);
2214 int read = new_bit & 1;
2215 int dir = new_bit & 2;
2218 * mark USED_IN has to look forwards -- to ensure no dependency
2219 * has ENABLED state, which would allow recursion deadlocks.
2221 * mark ENABLED has to look backwards -- to ensure no dependee
2222 * has USED_IN state, which, again, would allow recursion deadlocks.
2224 check_usage_f usage = dir ?
2225 check_usage_backwards : check_usage_forwards;
2228 * Validate that this particular lock does not have conflicting
2231 if (!valid_state(curr, this, new_bit, excl_bit))
2235 * Validate that the lock dependencies don't have conflicting usage
2238 if ((!read || !dir || STRICT_READ_CHECKS) &&
2239 !usage(curr, this, excl_bit, state_name(new_bit & ~1)))
2243 * Check for read in write conflicts
2246 if (!valid_state(curr, this, new_bit, excl_bit + 1))
2249 if (STRICT_READ_CHECKS &&
2250 !usage(curr, this, excl_bit + 1,
2251 state_name(new_bit + 1)))
2255 if (state_verbose(new_bit, hlock_class(this)))
2262 #define LOCKDEP_STATE(__STATE) __STATE,
2263 #include "lockdep_states.h"
2264 #undef LOCKDEP_STATE
2268 * Mark all held locks with a usage bit:
2271 mark_held_locks(struct task_struct *curr, enum mark_type mark)
2273 enum lock_usage_bit usage_bit;
2274 struct held_lock *hlock;
2277 for (i = 0; i < curr->lockdep_depth; i++) {
2278 hlock = curr->held_locks + i;
2280 usage_bit = 2 + (mark << 2); /* ENABLED */
2282 usage_bit += 1; /* READ */
2284 BUG_ON(usage_bit >= LOCK_USAGE_STATES);
2286 if (!mark_lock(curr, hlock, usage_bit))
2294 * Debugging helper: via this flag we know that we are in
2295 * 'early bootup code', and will warn about any invalid irqs-on event:
2297 static int early_boot_irqs_enabled;
2299 void early_boot_irqs_off(void)
2301 early_boot_irqs_enabled = 0;
2304 void early_boot_irqs_on(void)
2306 early_boot_irqs_enabled = 1;
2310 * Hardirqs will be enabled:
2312 void trace_hardirqs_on_caller(unsigned long ip)
2314 struct task_struct *curr = current;
2316 time_hardirqs_on(CALLER_ADDR0, ip);
2318 if (unlikely(!debug_locks || current->lockdep_recursion))
2321 if (DEBUG_LOCKS_WARN_ON(unlikely(!early_boot_irqs_enabled)))
2324 if (unlikely(curr->hardirqs_enabled)) {
2325 debug_atomic_inc(&redundant_hardirqs_on);
2328 /* we'll do an OFF -> ON transition: */
2329 curr->hardirqs_enabled = 1;
2331 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2333 if (DEBUG_LOCKS_WARN_ON(current->hardirq_context))
2336 * We are going to turn hardirqs on, so set the
2337 * usage bit for all held locks:
2339 if (!mark_held_locks(curr, HARDIRQ))
2342 * If we have softirqs enabled, then set the usage
2343 * bit for all held locks. (disabled hardirqs prevented
2344 * this bit from being set before)
2346 if (curr->softirqs_enabled)
2347 if (!mark_held_locks(curr, SOFTIRQ))
2350 curr->hardirq_enable_ip = ip;
2351 curr->hardirq_enable_event = ++curr->irq_events;
2352 debug_atomic_inc(&hardirqs_on_events);
2354 EXPORT_SYMBOL(trace_hardirqs_on_caller);
2356 void trace_hardirqs_on(void)
2358 trace_hardirqs_on_caller(CALLER_ADDR0);
2360 EXPORT_SYMBOL(trace_hardirqs_on);
2363 * Hardirqs were disabled:
2365 void trace_hardirqs_off_caller(unsigned long ip)
2367 struct task_struct *curr = current;
2369 time_hardirqs_off(CALLER_ADDR0, ip);
2371 if (unlikely(!debug_locks || current->lockdep_recursion))
2374 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2377 if (curr->hardirqs_enabled) {
2379 * We have done an ON -> OFF transition:
2381 curr->hardirqs_enabled = 0;
2382 curr->hardirq_disable_ip = ip;
2383 curr->hardirq_disable_event = ++curr->irq_events;
2384 debug_atomic_inc(&hardirqs_off_events);
2386 debug_atomic_inc(&redundant_hardirqs_off);
2388 EXPORT_SYMBOL(trace_hardirqs_off_caller);
2390 void trace_hardirqs_off(void)
2392 trace_hardirqs_off_caller(CALLER_ADDR0);
2394 EXPORT_SYMBOL(trace_hardirqs_off);
2397 * Softirqs will be enabled:
2399 void trace_softirqs_on(unsigned long ip)
2401 struct task_struct *curr = current;
2403 if (unlikely(!debug_locks))
2406 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2409 if (curr->softirqs_enabled) {
2410 debug_atomic_inc(&redundant_softirqs_on);
2415 * We'll do an OFF -> ON transition:
2417 curr->softirqs_enabled = 1;
2418 curr->softirq_enable_ip = ip;
2419 curr->softirq_enable_event = ++curr->irq_events;
2420 debug_atomic_inc(&softirqs_on_events);
2422 * We are going to turn softirqs on, so set the
2423 * usage bit for all held locks, if hardirqs are
2426 if (curr->hardirqs_enabled)
2427 mark_held_locks(curr, SOFTIRQ);
2431 * Softirqs were disabled:
2433 void trace_softirqs_off(unsigned long ip)
2435 struct task_struct *curr = current;
2437 if (unlikely(!debug_locks))
2440 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2443 if (curr->softirqs_enabled) {
2445 * We have done an ON -> OFF transition:
2447 curr->softirqs_enabled = 0;
2448 curr->softirq_disable_ip = ip;
2449 curr->softirq_disable_event = ++curr->irq_events;
2450 debug_atomic_inc(&softirqs_off_events);
2451 DEBUG_LOCKS_WARN_ON(!softirq_count());
2453 debug_atomic_inc(&redundant_softirqs_off);
2456 static void __lockdep_trace_alloc(gfp_t gfp_mask, unsigned long flags)
2458 struct task_struct *curr = current;
2460 if (unlikely(!debug_locks))
2463 /* no reclaim without waiting on it */
2464 if (!(gfp_mask & __GFP_WAIT))
2467 /* this guy won't enter reclaim */
2468 if ((curr->flags & PF_MEMALLOC) && !(gfp_mask & __GFP_NOMEMALLOC))
2471 /* We're only interested __GFP_FS allocations for now */
2472 if (!(gfp_mask & __GFP_FS))
2475 if (DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags)))
2478 mark_held_locks(curr, RECLAIM_FS);
2481 static void check_flags(unsigned long flags);
2483 void lockdep_trace_alloc(gfp_t gfp_mask)
2485 unsigned long flags;
2487 if (unlikely(current->lockdep_recursion))
2490 raw_local_irq_save(flags);
2492 current->lockdep_recursion = 1;
2493 __lockdep_trace_alloc(gfp_mask, flags);
2494 current->lockdep_recursion = 0;
2495 raw_local_irq_restore(flags);
2498 static int mark_irqflags(struct task_struct *curr, struct held_lock *hlock)
2501 * If non-trylock use in a hardirq or softirq context, then
2502 * mark the lock as used in these contexts:
2504 if (!hlock->trylock) {
2506 if (curr->hardirq_context)
2507 if (!mark_lock(curr, hlock,
2508 LOCK_USED_IN_HARDIRQ_READ))
2510 if (curr->softirq_context)
2511 if (!mark_lock(curr, hlock,
2512 LOCK_USED_IN_SOFTIRQ_READ))
2515 if (curr->hardirq_context)
2516 if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ))
2518 if (curr->softirq_context)
2519 if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ))
2523 if (!hlock->hardirqs_off) {
2525 if (!mark_lock(curr, hlock,
2526 LOCK_ENABLED_HARDIRQ_READ))
2528 if (curr->softirqs_enabled)
2529 if (!mark_lock(curr, hlock,
2530 LOCK_ENABLED_SOFTIRQ_READ))
2533 if (!mark_lock(curr, hlock,
2534 LOCK_ENABLED_HARDIRQ))
2536 if (curr->softirqs_enabled)
2537 if (!mark_lock(curr, hlock,
2538 LOCK_ENABLED_SOFTIRQ))
2544 * We reuse the irq context infrastructure more broadly as a general
2545 * context checking code. This tests GFP_FS recursion (a lock taken
2546 * during reclaim for a GFP_FS allocation is held over a GFP_FS
2549 if (!hlock->trylock && (curr->lockdep_reclaim_gfp & __GFP_FS)) {
2551 if (!mark_lock(curr, hlock, LOCK_USED_IN_RECLAIM_FS_READ))
2554 if (!mark_lock(curr, hlock, LOCK_USED_IN_RECLAIM_FS))
2562 static int separate_irq_context(struct task_struct *curr,
2563 struct held_lock *hlock)
2565 unsigned int depth = curr->lockdep_depth;
2568 * Keep track of points where we cross into an interrupt context:
2570 hlock->irq_context = 2*(curr->hardirq_context ? 1 : 0) +
2571 curr->softirq_context;
2573 struct held_lock *prev_hlock;
2575 prev_hlock = curr->held_locks + depth-1;
2577 * If we cross into another context, reset the
2578 * hash key (this also prevents the checking and the
2579 * adding of the dependency to 'prev'):
2581 if (prev_hlock->irq_context != hlock->irq_context)
2590 int mark_lock_irq(struct task_struct *curr, struct held_lock *this,
2591 enum lock_usage_bit new_bit)
2597 static inline int mark_irqflags(struct task_struct *curr,
2598 struct held_lock *hlock)
2603 static inline int separate_irq_context(struct task_struct *curr,
2604 struct held_lock *hlock)
2609 void lockdep_trace_alloc(gfp_t gfp_mask)
2616 * Mark a lock with a usage bit, and validate the state transition:
2618 static int mark_lock(struct task_struct *curr, struct held_lock *this,
2619 enum lock_usage_bit new_bit)
2621 unsigned int new_mask = 1 << new_bit, ret = 1;
2624 * If already set then do not dirty the cacheline,
2625 * nor do any checks:
2627 if (likely(hlock_class(this)->usage_mask & new_mask))
2633 * Make sure we didnt race:
2635 if (unlikely(hlock_class(this)->usage_mask & new_mask)) {
2640 hlock_class(this)->usage_mask |= new_mask;
2642 if (!save_trace(hlock_class(this)->usage_traces + new_bit))
2646 #define LOCKDEP_STATE(__STATE) \
2647 case LOCK_USED_IN_##__STATE: \
2648 case LOCK_USED_IN_##__STATE##_READ: \
2649 case LOCK_ENABLED_##__STATE: \
2650 case LOCK_ENABLED_##__STATE##_READ:
2651 #include "lockdep_states.h"
2652 #undef LOCKDEP_STATE
2653 ret = mark_lock_irq(curr, this, new_bit);
2658 debug_atomic_dec(&nr_unused_locks);
2661 if (!debug_locks_off_graph_unlock())
2670 * We must printk outside of the graph_lock:
2673 printk("\nmarked lock as {%s}:\n", usage_str[new_bit]);
2675 print_irqtrace_events(curr);
2683 * Initialize a lock instance's lock-class mapping info:
2685 void lockdep_init_map(struct lockdep_map *lock, const char *name,
2686 struct lock_class_key *key, int subclass)
2688 lock->class_cache = NULL;
2689 #ifdef CONFIG_LOCK_STAT
2690 lock->cpu = raw_smp_processor_id();
2693 if (DEBUG_LOCKS_WARN_ON(!name)) {
2694 lock->name = "NULL";
2700 if (DEBUG_LOCKS_WARN_ON(!key))
2703 * Sanity check, the lock-class key must be persistent:
2705 if (!static_obj(key)) {
2706 printk("BUG: key %p not in .data!\n", key);
2707 DEBUG_LOCKS_WARN_ON(1);
2712 if (unlikely(!debug_locks))
2716 register_lock_class(lock, subclass, 1);
2718 EXPORT_SYMBOL_GPL(lockdep_init_map);
2721 * This gets called for every mutex_lock*()/spin_lock*() operation.
2722 * We maintain the dependency maps and validate the locking attempt:
2724 static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
2725 int trylock, int read, int check, int hardirqs_off,
2726 struct lockdep_map *nest_lock, unsigned long ip,
2729 struct task_struct *curr = current;
2730 struct lock_class *class = NULL;
2731 struct held_lock *hlock;
2732 unsigned int depth, id;
2740 if (unlikely(!debug_locks))
2743 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2746 if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
2748 printk("BUG: MAX_LOCKDEP_SUBCLASSES too low!\n");
2749 printk("turning off the locking correctness validator.\n");
2755 class = lock->class_cache;
2757 * Not cached yet or subclass?
2759 if (unlikely(!class)) {
2760 class = register_lock_class(lock, subclass, 0);
2764 debug_atomic_inc((atomic_t *)&class->ops);
2765 if (very_verbose(class)) {
2766 printk("\nacquire class [%p] %s", class->key, class->name);
2767 if (class->name_version > 1)
2768 printk("#%d", class->name_version);
2774 * Add the lock to the list of currently held locks.
2775 * (we dont increase the depth just yet, up until the
2776 * dependency checks are done)
2778 depth = curr->lockdep_depth;
2779 if (DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH))
2782 class_idx = class - lock_classes + 1;
2785 hlock = curr->held_locks + depth - 1;
2786 if (hlock->class_idx == class_idx && nest_lock) {
2787 if (hlock->references)
2788 hlock->references++;
2790 hlock->references = 2;
2796 hlock = curr->held_locks + depth;
2797 if (DEBUG_LOCKS_WARN_ON(!class))
2799 hlock->class_idx = class_idx;
2800 hlock->acquire_ip = ip;
2801 hlock->instance = lock;
2802 hlock->nest_lock = nest_lock;
2803 hlock->trylock = trylock;
2805 hlock->check = check;
2806 hlock->hardirqs_off = !!hardirqs_off;
2807 hlock->references = references;
2808 #ifdef CONFIG_LOCK_STAT
2809 hlock->waittime_stamp = 0;
2810 hlock->holdtime_stamp = lockstat_clock();
2813 if (check == 2 && !mark_irqflags(curr, hlock))
2816 /* mark it as used: */
2817 if (!mark_lock(curr, hlock, LOCK_USED))
2821 * Calculate the chain hash: it's the combined hash of all the
2822 * lock keys along the dependency chain. We save the hash value
2823 * at every step so that we can get the current hash easily
2824 * after unlock. The chain hash is then used to cache dependency
2827 * The 'key ID' is what is the most compact key value to drive
2828 * the hash, not class->key.
2830 id = class - lock_classes;
2831 if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
2834 chain_key = curr->curr_chain_key;
2836 if (DEBUG_LOCKS_WARN_ON(chain_key != 0))
2841 hlock->prev_chain_key = chain_key;
2842 if (separate_irq_context(curr, hlock)) {
2846 chain_key = iterate_chain_key(chain_key, id);
2848 if (!validate_chain(curr, lock, hlock, chain_head, chain_key))
2851 curr->curr_chain_key = chain_key;
2852 curr->lockdep_depth++;
2853 check_chain_key(curr);
2854 #ifdef CONFIG_DEBUG_LOCKDEP
2855 if (unlikely(!debug_locks))
2858 if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
2860 printk("BUG: MAX_LOCK_DEPTH too low!\n");
2861 printk("turning off the locking correctness validator.\n");
2866 if (unlikely(curr->lockdep_depth > max_lockdep_depth))
2867 max_lockdep_depth = curr->lockdep_depth;
2873 print_unlock_inbalance_bug(struct task_struct *curr, struct lockdep_map *lock,
2876 if (!debug_locks_off())
2878 if (debug_locks_silent)
2881 printk("\n=====================================\n");
2882 printk( "[ BUG: bad unlock balance detected! ]\n");
2883 printk( "-------------------------------------\n");
2884 printk("%s/%d is trying to release lock (",
2885 curr->comm, task_pid_nr(curr));
2886 print_lockdep_cache(lock);
2889 printk("but there are no more locks to release!\n");
2890 printk("\nother info that might help us debug this:\n");
2891 lockdep_print_held_locks(curr);
2893 printk("\nstack backtrace:\n");
2900 * Common debugging checks for both nested and non-nested unlock:
2902 static int check_unlock(struct task_struct *curr, struct lockdep_map *lock,
2905 if (unlikely(!debug_locks))
2907 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2910 if (curr->lockdep_depth <= 0)
2911 return print_unlock_inbalance_bug(curr, lock, ip);
2916 static int match_held_lock(struct held_lock *hlock, struct lockdep_map *lock)
2918 if (hlock->instance == lock)
2921 if (hlock->references) {
2922 struct lock_class *class = lock->class_cache;
2925 class = look_up_lock_class(lock, 0);
2927 if (DEBUG_LOCKS_WARN_ON(!class))
2930 if (DEBUG_LOCKS_WARN_ON(!hlock->nest_lock))
2933 if (hlock->class_idx == class - lock_classes + 1)
2941 __lock_set_class(struct lockdep_map *lock, const char *name,
2942 struct lock_class_key *key, unsigned int subclass,
2945 struct task_struct *curr = current;
2946 struct held_lock *hlock, *prev_hlock;
2947 struct lock_class *class;
2951 depth = curr->lockdep_depth;
2952 if (DEBUG_LOCKS_WARN_ON(!depth))
2956 for (i = depth-1; i >= 0; i--) {
2957 hlock = curr->held_locks + i;
2959 * We must not cross into another context:
2961 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
2963 if (match_held_lock(hlock, lock))
2967 return print_unlock_inbalance_bug(curr, lock, ip);
2970 lockdep_init_map(lock, name, key, 0);
2971 class = register_lock_class(lock, subclass, 0);
2972 hlock->class_idx = class - lock_classes + 1;
2974 curr->lockdep_depth = i;
2975 curr->curr_chain_key = hlock->prev_chain_key;
2977 for (; i < depth; i++) {
2978 hlock = curr->held_locks + i;
2979 if (!__lock_acquire(hlock->instance,
2980 hlock_class(hlock)->subclass, hlock->trylock,
2981 hlock->read, hlock->check, hlock->hardirqs_off,
2982 hlock->nest_lock, hlock->acquire_ip,
2987 if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth))
2993 * Remove the lock to the list of currently held locks in a
2994 * potentially non-nested (out of order) manner. This is a
2995 * relatively rare operation, as all the unlock APIs default
2996 * to nested mode (which uses lock_release()):
2999 lock_release_non_nested(struct task_struct *curr,
3000 struct lockdep_map *lock, unsigned long ip)
3002 struct held_lock *hlock, *prev_hlock;
3007 * Check whether the lock exists in the current stack
3010 depth = curr->lockdep_depth;
3011 if (DEBUG_LOCKS_WARN_ON(!depth))
3015 for (i = depth-1; i >= 0; i--) {
3016 hlock = curr->held_locks + i;
3018 * We must not cross into another context:
3020 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3022 if (match_held_lock(hlock, lock))
3026 return print_unlock_inbalance_bug(curr, lock, ip);
3029 if (hlock->instance == lock)
3030 lock_release_holdtime(hlock);
3032 if (hlock->references) {
3033 hlock->references--;
3034 if (hlock->references) {
3036 * We had, and after removing one, still have
3037 * references, the current lock stack is still
3038 * valid. We're done!
3045 * We have the right lock to unlock, 'hlock' points to it.
3046 * Now we remove it from the stack, and add back the other
3047 * entries (if any), recalculating the hash along the way:
3050 curr->lockdep_depth = i;
3051 curr->curr_chain_key = hlock->prev_chain_key;
3053 for (i++; i < depth; i++) {
3054 hlock = curr->held_locks + i;
3055 if (!__lock_acquire(hlock->instance,
3056 hlock_class(hlock)->subclass, hlock->trylock,
3057 hlock->read, hlock->check, hlock->hardirqs_off,
3058 hlock->nest_lock, hlock->acquire_ip,
3063 if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - 1))
3069 * Remove the lock to the list of currently held locks - this gets
3070 * called on mutex_unlock()/spin_unlock*() (or on a failed
3071 * mutex_lock_interruptible()). This is done for unlocks that nest
3072 * perfectly. (i.e. the current top of the lock-stack is unlocked)
3074 static int lock_release_nested(struct task_struct *curr,
3075 struct lockdep_map *lock, unsigned long ip)
3077 struct held_lock *hlock;
3081 * Pop off the top of the lock stack:
3083 depth = curr->lockdep_depth - 1;
3084 hlock = curr->held_locks + depth;
3087 * Is the unlock non-nested:
3089 if (hlock->instance != lock || hlock->references)
3090 return lock_release_non_nested(curr, lock, ip);
3091 curr->lockdep_depth--;
3093 if (DEBUG_LOCKS_WARN_ON(!depth && (hlock->prev_chain_key != 0)))
3096 curr->curr_chain_key = hlock->prev_chain_key;
3098 lock_release_holdtime(hlock);
3100 #ifdef CONFIG_DEBUG_LOCKDEP
3101 hlock->prev_chain_key = 0;
3102 hlock->class_idx = 0;
3103 hlock->acquire_ip = 0;
3104 hlock->irq_context = 0;
3110 * Remove the lock to the list of currently held locks - this gets
3111 * called on mutex_unlock()/spin_unlock*() (or on a failed
3112 * mutex_lock_interruptible()). This is done for unlocks that nest
3113 * perfectly. (i.e. the current top of the lock-stack is unlocked)
3116 __lock_release(struct lockdep_map *lock, int nested, unsigned long ip)
3118 struct task_struct *curr = current;
3120 if (!check_unlock(curr, lock, ip))
3124 if (!lock_release_nested(curr, lock, ip))
3127 if (!lock_release_non_nested(curr, lock, ip))
3131 check_chain_key(curr);
3134 static int __lock_is_held(struct lockdep_map *lock)
3136 struct task_struct *curr = current;
3139 for (i = 0; i < curr->lockdep_depth; i++) {
3140 struct held_lock *hlock = curr->held_locks + i;
3142 if (match_held_lock(hlock, lock))
3150 * Check whether we follow the irq-flags state precisely:
3152 static void check_flags(unsigned long flags)
3154 #if defined(CONFIG_PROVE_LOCKING) && defined(CONFIG_DEBUG_LOCKDEP) && \
3155 defined(CONFIG_TRACE_IRQFLAGS)
3159 if (irqs_disabled_flags(flags)) {
3160 if (DEBUG_LOCKS_WARN_ON(current->hardirqs_enabled)) {
3161 printk("possible reason: unannotated irqs-off.\n");
3164 if (DEBUG_LOCKS_WARN_ON(!current->hardirqs_enabled)) {
3165 printk("possible reason: unannotated irqs-on.\n");
3170 * We dont accurately track softirq state in e.g.
3171 * hardirq contexts (such as on 4KSTACKS), so only
3172 * check if not in hardirq contexts:
3174 if (!hardirq_count()) {
3175 if (softirq_count())
3176 DEBUG_LOCKS_WARN_ON(current->softirqs_enabled);
3178 DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled);
3182 print_irqtrace_events(current);
3186 void lock_set_class(struct lockdep_map *lock, const char *name,
3187 struct lock_class_key *key, unsigned int subclass,
3190 unsigned long flags;
3192 if (unlikely(current->lockdep_recursion))
3195 raw_local_irq_save(flags);
3196 current->lockdep_recursion = 1;
3198 if (__lock_set_class(lock, name, key, subclass, ip))
3199 check_chain_key(current);
3200 current->lockdep_recursion = 0;
3201 raw_local_irq_restore(flags);
3203 EXPORT_SYMBOL_GPL(lock_set_class);
3206 * We are not always called with irqs disabled - do that here,
3207 * and also avoid lockdep recursion:
3209 void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
3210 int trylock, int read, int check,
3211 struct lockdep_map *nest_lock, unsigned long ip)
3213 unsigned long flags;
3215 if (unlikely(current->lockdep_recursion))
3218 raw_local_irq_save(flags);
3221 current->lockdep_recursion = 1;
3222 trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip);
3223 __lock_acquire(lock, subclass, trylock, read, check,
3224 irqs_disabled_flags(flags), nest_lock, ip, 0);
3225 current->lockdep_recursion = 0;
3226 raw_local_irq_restore(flags);
3228 EXPORT_SYMBOL_GPL(lock_acquire);
3230 void lock_release(struct lockdep_map *lock, int nested,
3233 unsigned long flags;
3235 if (unlikely(current->lockdep_recursion))
3238 raw_local_irq_save(flags);
3240 current->lockdep_recursion = 1;
3241 trace_lock_release(lock, nested, ip);
3242 __lock_release(lock, nested, ip);
3243 current->lockdep_recursion = 0;
3244 raw_local_irq_restore(flags);
3246 EXPORT_SYMBOL_GPL(lock_release);
3248 int lock_is_held(struct lockdep_map *lock)
3250 unsigned long flags;
3253 if (unlikely(current->lockdep_recursion))
3256 raw_local_irq_save(flags);
3259 current->lockdep_recursion = 1;
3260 ret = __lock_is_held(lock);
3261 current->lockdep_recursion = 0;
3262 raw_local_irq_restore(flags);
3266 EXPORT_SYMBOL_GPL(lock_is_held);
3268 void lockdep_set_current_reclaim_state(gfp_t gfp_mask)
3270 current->lockdep_reclaim_gfp = gfp_mask;
3273 void lockdep_clear_current_reclaim_state(void)
3275 current->lockdep_reclaim_gfp = 0;
3278 #ifdef CONFIG_LOCK_STAT
3280 print_lock_contention_bug(struct task_struct *curr, struct lockdep_map *lock,
3283 if (!debug_locks_off())
3285 if (debug_locks_silent)
3288 printk("\n=================================\n");
3289 printk( "[ BUG: bad contention detected! ]\n");
3290 printk( "---------------------------------\n");
3291 printk("%s/%d is trying to contend lock (",
3292 curr->comm, task_pid_nr(curr));
3293 print_lockdep_cache(lock);
3296 printk("but there are no locks held!\n");
3297 printk("\nother info that might help us debug this:\n");
3298 lockdep_print_held_locks(curr);
3300 printk("\nstack backtrace:\n");
3307 __lock_contended(struct lockdep_map *lock, unsigned long ip)
3309 struct task_struct *curr = current;
3310 struct held_lock *hlock, *prev_hlock;
3311 struct lock_class_stats *stats;
3313 int i, contention_point, contending_point;
3315 depth = curr->lockdep_depth;
3316 if (DEBUG_LOCKS_WARN_ON(!depth))
3320 for (i = depth-1; i >= 0; i--) {
3321 hlock = curr->held_locks + i;
3323 * We must not cross into another context:
3325 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3327 if (match_held_lock(hlock, lock))
3331 print_lock_contention_bug(curr, lock, ip);
3335 if (hlock->instance != lock)
3338 hlock->waittime_stamp = lockstat_clock();
3340 contention_point = lock_point(hlock_class(hlock)->contention_point, ip);
3341 contending_point = lock_point(hlock_class(hlock)->contending_point,
3344 stats = get_lock_stats(hlock_class(hlock));
3345 if (contention_point < LOCKSTAT_POINTS)
3346 stats->contention_point[contention_point]++;
3347 if (contending_point < LOCKSTAT_POINTS)
3348 stats->contending_point[contending_point]++;
3349 if (lock->cpu != smp_processor_id())
3350 stats->bounces[bounce_contended + !!hlock->read]++;
3351 put_lock_stats(stats);
3355 __lock_acquired(struct lockdep_map *lock, unsigned long ip)
3357 struct task_struct *curr = current;
3358 struct held_lock *hlock, *prev_hlock;
3359 struct lock_class_stats *stats;
3361 u64 now, waittime = 0;
3364 depth = curr->lockdep_depth;
3365 if (DEBUG_LOCKS_WARN_ON(!depth))
3369 for (i = depth-1; i >= 0; i--) {
3370 hlock = curr->held_locks + i;
3372 * We must not cross into another context:
3374 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3376 if (match_held_lock(hlock, lock))
3380 print_lock_contention_bug(curr, lock, _RET_IP_);
3384 if (hlock->instance != lock)
3387 cpu = smp_processor_id();
3388 if (hlock->waittime_stamp) {
3389 now = lockstat_clock();
3390 waittime = now - hlock->waittime_stamp;
3391 hlock->holdtime_stamp = now;
3394 trace_lock_acquired(lock, ip, waittime);
3396 stats = get_lock_stats(hlock_class(hlock));
3399 lock_time_inc(&stats->read_waittime, waittime);
3401 lock_time_inc(&stats->write_waittime, waittime);
3403 if (lock->cpu != cpu)
3404 stats->bounces[bounce_acquired + !!hlock->read]++;
3405 put_lock_stats(stats);
3411 void lock_contended(struct lockdep_map *lock, unsigned long ip)
3413 unsigned long flags;
3415 if (unlikely(!lock_stat))
3418 if (unlikely(current->lockdep_recursion))
3421 raw_local_irq_save(flags);
3423 current->lockdep_recursion = 1;
3424 trace_lock_contended(lock, ip);
3425 __lock_contended(lock, ip);
3426 current->lockdep_recursion = 0;
3427 raw_local_irq_restore(flags);
3429 EXPORT_SYMBOL_GPL(lock_contended);
3431 void lock_acquired(struct lockdep_map *lock, unsigned long ip)
3433 unsigned long flags;
3435 if (unlikely(!lock_stat))
3438 if (unlikely(current->lockdep_recursion))
3441 raw_local_irq_save(flags);
3443 current->lockdep_recursion = 1;
3444 __lock_acquired(lock, ip);
3445 current->lockdep_recursion = 0;
3446 raw_local_irq_restore(flags);
3448 EXPORT_SYMBOL_GPL(lock_acquired);
3452 * Used by the testsuite, sanitize the validator state
3453 * after a simulated failure:
3456 void lockdep_reset(void)
3458 unsigned long flags;
3461 raw_local_irq_save(flags);
3462 current->curr_chain_key = 0;
3463 current->lockdep_depth = 0;
3464 current->lockdep_recursion = 0;
3465 memset(current->held_locks, 0, MAX_LOCK_DEPTH*sizeof(struct held_lock));
3466 nr_hardirq_chains = 0;
3467 nr_softirq_chains = 0;
3468 nr_process_chains = 0;
3470 for (i = 0; i < CHAINHASH_SIZE; i++)
3471 INIT_LIST_HEAD(chainhash_table + i);
3472 raw_local_irq_restore(flags);
3475 static void zap_class(struct lock_class *class)
3480 * Remove all dependencies this lock is
3483 for (i = 0; i < nr_list_entries; i++) {
3484 if (list_entries[i].class == class)
3485 list_del_rcu(&list_entries[i].entry);
3488 * Unhash the class and remove it from the all_lock_classes list:
3490 list_del_rcu(&class->hash_entry);
3491 list_del_rcu(&class->lock_entry);
3496 static inline int within(const void *addr, void *start, unsigned long size)
3498 return addr >= start && addr < start + size;
3501 void lockdep_free_key_range(void *start, unsigned long size)
3503 struct lock_class *class, *next;
3504 struct list_head *head;
3505 unsigned long flags;
3509 raw_local_irq_save(flags);
3510 locked = graph_lock();
3513 * Unhash all classes that were created by this module:
3515 for (i = 0; i < CLASSHASH_SIZE; i++) {
3516 head = classhash_table + i;
3517 if (list_empty(head))
3519 list_for_each_entry_safe(class, next, head, hash_entry) {
3520 if (within(class->key, start, size))
3522 else if (within(class->name, start, size))
3529 raw_local_irq_restore(flags);
3532 void lockdep_reset_lock(struct lockdep_map *lock)
3534 struct lock_class *class, *next;
3535 struct list_head *head;
3536 unsigned long flags;
3540 raw_local_irq_save(flags);
3543 * Remove all classes this lock might have:
3545 for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) {
3547 * If the class exists we look it up and zap it:
3549 class = look_up_lock_class(lock, j);
3554 * Debug check: in the end all mapped classes should
3557 locked = graph_lock();
3558 for (i = 0; i < CLASSHASH_SIZE; i++) {
3559 head = classhash_table + i;
3560 if (list_empty(head))
3562 list_for_each_entry_safe(class, next, head, hash_entry) {
3563 if (unlikely(class == lock->class_cache)) {
3564 if (debug_locks_off_graph_unlock())
3574 raw_local_irq_restore(flags);
3577 void lockdep_init(void)
3582 * Some architectures have their own start_kernel()
3583 * code which calls lockdep_init(), while we also
3584 * call lockdep_init() from the start_kernel() itself,
3585 * and we want to initialize the hashes only once:
3587 if (lockdep_initialized)
3590 for (i = 0; i < CLASSHASH_SIZE; i++)
3591 INIT_LIST_HEAD(classhash_table + i);
3593 for (i = 0; i < CHAINHASH_SIZE; i++)
3594 INIT_LIST_HEAD(chainhash_table + i);
3596 lockdep_initialized = 1;
3599 void __init lockdep_info(void)
3601 printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");
3603 printk("... MAX_LOCKDEP_SUBCLASSES: %lu\n", MAX_LOCKDEP_SUBCLASSES);
3604 printk("... MAX_LOCK_DEPTH: %lu\n", MAX_LOCK_DEPTH);
3605 printk("... MAX_LOCKDEP_KEYS: %lu\n", MAX_LOCKDEP_KEYS);
3606 printk("... CLASSHASH_SIZE: %lu\n", CLASSHASH_SIZE);
3607 printk("... MAX_LOCKDEP_ENTRIES: %lu\n", MAX_LOCKDEP_ENTRIES);
3608 printk("... MAX_LOCKDEP_CHAINS: %lu\n", MAX_LOCKDEP_CHAINS);
3609 printk("... CHAINHASH_SIZE: %lu\n", CHAINHASH_SIZE);
3611 printk(" memory used by lock dependency info: %lu kB\n",
3612 (sizeof(struct lock_class) * MAX_LOCKDEP_KEYS +
3613 sizeof(struct list_head) * CLASSHASH_SIZE +
3614 sizeof(struct lock_list) * MAX_LOCKDEP_ENTRIES +
3615 sizeof(struct lock_chain) * MAX_LOCKDEP_CHAINS +
3616 sizeof(struct list_head) * CHAINHASH_SIZE
3617 #ifdef CONFIG_PROVE_LOCKING
3618 + sizeof(struct circular_queue)
3623 printk(" per task-struct memory footprint: %lu bytes\n",
3624 sizeof(struct held_lock) * MAX_LOCK_DEPTH);
3626 #ifdef CONFIG_DEBUG_LOCKDEP
3627 if (lockdep_init_error) {
3628 printk("WARNING: lockdep init error! Arch code didn't call lockdep_init() early enough?\n");
3629 printk("Call stack leading to lockdep invocation was:\n");
3630 print_stack_trace(&lockdep_init_trace, 0);
3636 print_freed_lock_bug(struct task_struct *curr, const void *mem_from,
3637 const void *mem_to, struct held_lock *hlock)
3639 if (!debug_locks_off())
3641 if (debug_locks_silent)
3644 printk("\n=========================\n");
3645 printk( "[ BUG: held lock freed! ]\n");
3646 printk( "-------------------------\n");
3647 printk("%s/%d is freeing memory %p-%p, with a lock still held there!\n",
3648 curr->comm, task_pid_nr(curr), mem_from, mem_to-1);
3650 lockdep_print_held_locks(curr);
3652 printk("\nstack backtrace:\n");
3656 static inline int not_in_range(const void* mem_from, unsigned long mem_len,
3657 const void* lock_from, unsigned long lock_len)
3659 return lock_from + lock_len <= mem_from ||
3660 mem_from + mem_len <= lock_from;
3664 * Called when kernel memory is freed (or unmapped), or if a lock
3665 * is destroyed or reinitialized - this code checks whether there is
3666 * any held lock in the memory range of <from> to <to>:
3668 void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len)
3670 struct task_struct *curr = current;
3671 struct held_lock *hlock;
3672 unsigned long flags;
3675 if (unlikely(!debug_locks))
3678 local_irq_save(flags);
3679 for (i = 0; i < curr->lockdep_depth; i++) {
3680 hlock = curr->held_locks + i;
3682 if (not_in_range(mem_from, mem_len, hlock->instance,
3683 sizeof(*hlock->instance)))
3686 print_freed_lock_bug(curr, mem_from, mem_from + mem_len, hlock);
3689 local_irq_restore(flags);
3691 EXPORT_SYMBOL_GPL(debug_check_no_locks_freed);
3693 static void print_held_locks_bug(struct task_struct *curr)
3695 if (!debug_locks_off())
3697 if (debug_locks_silent)
3700 printk("\n=====================================\n");
3701 printk( "[ BUG: lock held at task exit time! ]\n");
3702 printk( "-------------------------------------\n");
3703 printk("%s/%d is exiting with locks still held!\n",
3704 curr->comm, task_pid_nr(curr));
3705 lockdep_print_held_locks(curr);
3707 printk("\nstack backtrace:\n");
3711 void debug_check_no_locks_held(struct task_struct *task)
3713 if (unlikely(task->lockdep_depth > 0))
3714 print_held_locks_bug(task);
3717 void debug_show_all_locks(void)
3719 struct task_struct *g, *p;
3723 if (unlikely(!debug_locks)) {
3724 printk("INFO: lockdep is turned off.\n");
3727 printk("\nShowing all locks held in the system:\n");
3730 * Here we try to get the tasklist_lock as hard as possible,
3731 * if not successful after 2 seconds we ignore it (but keep
3732 * trying). This is to enable a debug printout even if a
3733 * tasklist_lock-holding task deadlocks or crashes.
3736 if (!read_trylock(&tasklist_lock)) {
3738 printk("hm, tasklist_lock locked, retrying... ");
3741 printk(" #%d", 10-count);
3745 printk(" ignoring it.\n");
3749 printk(KERN_CONT " locked it.\n");
3752 do_each_thread(g, p) {
3754 * It's not reliable to print a task's held locks
3755 * if it's not sleeping (or if it's not the current
3758 if (p->state == TASK_RUNNING && p != current)
3760 if (p->lockdep_depth)
3761 lockdep_print_held_locks(p);
3763 if (read_trylock(&tasklist_lock))
3765 } while_each_thread(g, p);
3768 printk("=============================================\n\n");
3771 read_unlock(&tasklist_lock);
3773 EXPORT_SYMBOL_GPL(debug_show_all_locks);
3776 * Careful: only use this function if you are sure that
3777 * the task cannot run in parallel!
3779 void __debug_show_held_locks(struct task_struct *task)
3781 if (unlikely(!debug_locks)) {
3782 printk("INFO: lockdep is turned off.\n");
3785 lockdep_print_held_locks(task);
3787 EXPORT_SYMBOL_GPL(__debug_show_held_locks);
3789 void debug_show_held_locks(struct task_struct *task)
3791 __debug_show_held_locks(task);
3793 EXPORT_SYMBOL_GPL(debug_show_held_locks);
3795 void lockdep_sys_exit(void)
3797 struct task_struct *curr = current;
3799 if (unlikely(curr->lockdep_depth)) {
3800 if (!debug_locks_off())
3802 printk("\n================================================\n");
3803 printk( "[ BUG: lock held when returning to user space! ]\n");
3804 printk( "------------------------------------------------\n");
3805 printk("%s/%d is leaving the kernel with locks still held!\n",
3806 curr->comm, curr->pid);
3807 lockdep_print_held_locks(curr);
3811 void lockdep_rcu_dereference(const char *file, const int line)
3813 struct task_struct *curr = current;
3815 if (!debug_locks_off())
3817 printk("\n===================================================\n");
3818 printk( "[ INFO: suspicious rcu_dereference_check() usage. ]\n");
3819 printk( "---------------------------------------------------\n");
3820 printk("%s:%d invoked rcu_dereference_check() without protection!\n",
3822 printk("\nother info that might help us debug this:\n\n");
3823 printk("\nrcu_scheduler_active = %d, debug_locks = %d\n", rcu_scheduler_active, debug_locks);
3824 lockdep_print_held_locks(curr);
3825 printk("\nstack backtrace:\n");
3828 EXPORT_SYMBOL_GPL(lockdep_rcu_dereference);