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 local_clock();
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 DEFINE_PER_CPU(struct lockdep_stats, lockdep_stats);
441 #define __USAGE(__STATE) \
442 [LOCK_USED_IN_##__STATE] = "IN-"__stringify(__STATE)"-W", \
443 [LOCK_ENABLED_##__STATE] = __stringify(__STATE)"-ON-W", \
444 [LOCK_USED_IN_##__STATE##_READ] = "IN-"__stringify(__STATE)"-R",\
445 [LOCK_ENABLED_##__STATE##_READ] = __stringify(__STATE)"-ON-R",
447 static const char *usage_str[] =
449 #define LOCKDEP_STATE(__STATE) __USAGE(__STATE)
450 #include "lockdep_states.h"
452 [LOCK_USED] = "INITIAL USE",
455 const char * __get_key_name(struct lockdep_subclass_key *key, char *str)
457 return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str);
460 static inline unsigned long lock_flag(enum lock_usage_bit bit)
465 static char get_usage_char(struct lock_class *class, enum lock_usage_bit bit)
469 if (class->usage_mask & lock_flag(bit + 2))
471 if (class->usage_mask & lock_flag(bit)) {
473 if (class->usage_mask & lock_flag(bit + 2))
480 void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS])
484 #define LOCKDEP_STATE(__STATE) \
485 usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE); \
486 usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE##_READ);
487 #include "lockdep_states.h"
493 static void print_lock_name(struct lock_class *class)
495 char str[KSYM_NAME_LEN], usage[LOCK_USAGE_CHARS];
498 get_usage_chars(class, usage);
502 name = __get_key_name(class->key, str);
503 printk(" (%s", name);
505 printk(" (%s", name);
506 if (class->name_version > 1)
507 printk("#%d", class->name_version);
509 printk("/%d", class->subclass);
511 printk("){%s}", usage);
514 static void print_lockdep_cache(struct lockdep_map *lock)
517 char str[KSYM_NAME_LEN];
521 name = __get_key_name(lock->key->subkeys, str);
526 static void print_lock(struct held_lock *hlock)
528 print_lock_name(hlock_class(hlock));
530 print_ip_sym(hlock->acquire_ip);
533 static void lockdep_print_held_locks(struct task_struct *curr)
535 int i, depth = curr->lockdep_depth;
538 printk("no locks held by %s/%d.\n", curr->comm, task_pid_nr(curr));
541 printk("%d lock%s held by %s/%d:\n",
542 depth, depth > 1 ? "s" : "", curr->comm, task_pid_nr(curr));
544 for (i = 0; i < depth; i++) {
546 print_lock(curr->held_locks + i);
550 static void print_kernel_version(void)
552 printk("%s %.*s\n", init_utsname()->release,
553 (int)strcspn(init_utsname()->version, " "),
554 init_utsname()->version);
557 static int very_verbose(struct lock_class *class)
560 return class_filter(class);
566 * Is this the address of a static object:
568 static int static_obj(void *obj)
570 unsigned long start = (unsigned long) &_stext,
571 end = (unsigned long) &_end,
572 addr = (unsigned long) obj;
577 if ((addr >= start) && (addr < end))
580 if (arch_is_kernel_data(addr))
584 * in-kernel percpu var?
586 if (is_kernel_percpu_address(addr))
590 * module static or percpu var?
592 return is_module_address(addr) || is_module_percpu_address(addr);
596 * To make lock name printouts unique, we calculate a unique
597 * class->name_version generation counter:
599 static int count_matching_names(struct lock_class *new_class)
601 struct lock_class *class;
604 if (!new_class->name)
607 list_for_each_entry(class, &all_lock_classes, lock_entry) {
608 if (new_class->key - new_class->subclass == class->key)
609 return class->name_version;
610 if (class->name && !strcmp(class->name, new_class->name))
611 count = max(count, class->name_version);
618 * Register a lock's class in the hash-table, if the class is not present
619 * yet. Otherwise we look it up. We cache the result in the lock object
620 * itself, so actual lookup of the hash should be once per lock object.
622 static inline struct lock_class *
623 look_up_lock_class(struct lockdep_map *lock, unsigned int subclass)
625 struct lockdep_subclass_key *key;
626 struct list_head *hash_head;
627 struct lock_class *class;
629 #ifdef CONFIG_DEBUG_LOCKDEP
631 * If the architecture calls into lockdep before initializing
632 * the hashes then we'll warn about it later. (we cannot printk
635 if (unlikely(!lockdep_initialized)) {
637 lockdep_init_error = 1;
638 save_stack_trace(&lockdep_init_trace);
642 if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
645 "BUG: looking up invalid subclass: %u\n", subclass);
647 "turning off the locking correctness validator.\n");
653 * Static locks do not have their class-keys yet - for them the key
654 * is the lock object itself:
656 if (unlikely(!lock->key))
657 lock->key = (void *)lock;
660 * NOTE: the class-key must be unique. For dynamic locks, a static
661 * lock_class_key variable is passed in through the mutex_init()
662 * (or spin_lock_init()) call - which acts as the key. For static
663 * locks we use the lock object itself as the key.
665 BUILD_BUG_ON(sizeof(struct lock_class_key) >
666 sizeof(struct lockdep_map));
668 key = lock->key->subkeys + subclass;
670 hash_head = classhashentry(key);
673 * We can walk the hash lockfree, because the hash only
674 * grows, and we are careful when adding entries to the end:
676 list_for_each_entry(class, hash_head, hash_entry) {
677 if (class->key == key) {
678 WARN_ON_ONCE(class->name != lock->name);
687 * Register a lock's class in the hash-table, if the class is not present
688 * yet. Otherwise we look it up. We cache the result in the lock object
689 * itself, so actual lookup of the hash should be once per lock object.
691 static inline struct lock_class *
692 register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
694 struct lockdep_subclass_key *key;
695 struct list_head *hash_head;
696 struct lock_class *class;
699 class = look_up_lock_class(lock, subclass);
704 * Debug-check: all keys must be persistent!
706 if (!static_obj(lock->key)) {
708 printk("INFO: trying to register non-static key.\n");
709 printk("the code is fine but needs lockdep annotation.\n");
710 printk("turning off the locking correctness validator.\n");
716 key = lock->key->subkeys + subclass;
717 hash_head = classhashentry(key);
719 raw_local_irq_save(flags);
721 raw_local_irq_restore(flags);
725 * We have to do the hash-walk again, to avoid races
728 list_for_each_entry(class, hash_head, hash_entry)
729 if (class->key == key)
732 * Allocate a new key from the static array, and add it to
735 if (nr_lock_classes >= MAX_LOCKDEP_KEYS) {
736 if (!debug_locks_off_graph_unlock()) {
737 raw_local_irq_restore(flags);
740 raw_local_irq_restore(flags);
742 printk("BUG: MAX_LOCKDEP_KEYS too low!\n");
743 printk("turning off the locking correctness validator.\n");
747 class = lock_classes + nr_lock_classes++;
748 debug_atomic_inc(nr_unused_locks);
750 class->name = lock->name;
751 class->subclass = subclass;
752 INIT_LIST_HEAD(&class->lock_entry);
753 INIT_LIST_HEAD(&class->locks_before);
754 INIT_LIST_HEAD(&class->locks_after);
755 class->name_version = count_matching_names(class);
757 * We use RCU's safe list-add method to make
758 * parallel walking of the hash-list safe:
760 list_add_tail_rcu(&class->hash_entry, hash_head);
762 * Add it to the global list of classes:
764 list_add_tail_rcu(&class->lock_entry, &all_lock_classes);
766 if (verbose(class)) {
768 raw_local_irq_restore(flags);
770 printk("\nnew class %p: %s", class->key, class->name);
771 if (class->name_version > 1)
772 printk("#%d", class->name_version);
776 raw_local_irq_save(flags);
778 raw_local_irq_restore(flags);
784 raw_local_irq_restore(flags);
786 if (!subclass || force)
787 lock->class_cache[0] = class;
788 else if (subclass < NR_LOCKDEP_CACHING_CLASSES)
789 lock->class_cache[subclass] = 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,
821 int distance, struct stack_trace *trace)
823 struct lock_list *entry;
825 * Lock not present yet - get a new dependency struct and
826 * add it to the list:
828 entry = alloc_list_entry();
833 entry->distance = distance;
834 entry->trace = *trace;
836 * Since we never remove from the dependency list, the list can
837 * be walked lockless by other CPUs, it's only allocation
838 * that must be protected by the spinlock. But this also means
839 * we must make new entries visible only once writes to the
840 * entry become visible - hence the RCU op:
842 list_add_tail_rcu(&entry->entry, head);
848 * For good efficiency of modular, we use power of 2
850 #define MAX_CIRCULAR_QUEUE_SIZE 4096UL
851 #define CQ_MASK (MAX_CIRCULAR_QUEUE_SIZE-1)
854 * The circular_queue and helpers is used to implement the
855 * breadth-first search(BFS)algorithem, by which we can build
856 * the shortest path from the next lock to be acquired to the
857 * previous held lock if there is a circular between them.
859 struct circular_queue {
860 unsigned long element[MAX_CIRCULAR_QUEUE_SIZE];
861 unsigned int front, rear;
864 static struct circular_queue lock_cq;
866 unsigned int max_bfs_queue_depth;
868 static unsigned int lockdep_dependency_gen_id;
870 static inline void __cq_init(struct circular_queue *cq)
872 cq->front = cq->rear = 0;
873 lockdep_dependency_gen_id++;
876 static inline int __cq_empty(struct circular_queue *cq)
878 return (cq->front == cq->rear);
881 static inline int __cq_full(struct circular_queue *cq)
883 return ((cq->rear + 1) & CQ_MASK) == cq->front;
886 static inline int __cq_enqueue(struct circular_queue *cq, unsigned long elem)
891 cq->element[cq->rear] = elem;
892 cq->rear = (cq->rear + 1) & CQ_MASK;
896 static inline int __cq_dequeue(struct circular_queue *cq, unsigned long *elem)
901 *elem = cq->element[cq->front];
902 cq->front = (cq->front + 1) & CQ_MASK;
906 static inline unsigned int __cq_get_elem_count(struct circular_queue *cq)
908 return (cq->rear - cq->front) & CQ_MASK;
911 static inline void mark_lock_accessed(struct lock_list *lock,
912 struct lock_list *parent)
916 nr = lock - list_entries;
917 WARN_ON(nr >= nr_list_entries);
918 lock->parent = parent;
919 lock->class->dep_gen_id = lockdep_dependency_gen_id;
922 static inline unsigned long lock_accessed(struct lock_list *lock)
926 nr = lock - list_entries;
927 WARN_ON(nr >= nr_list_entries);
928 return lock->class->dep_gen_id == lockdep_dependency_gen_id;
931 static inline struct lock_list *get_lock_parent(struct lock_list *child)
933 return child->parent;
936 static inline int get_lock_depth(struct lock_list *child)
939 struct lock_list *parent;
941 while ((parent = get_lock_parent(child))) {
948 static int __bfs(struct lock_list *source_entry,
950 int (*match)(struct lock_list *entry, void *data),
951 struct lock_list **target_entry,
954 struct lock_list *entry;
955 struct list_head *head;
956 struct circular_queue *cq = &lock_cq;
959 if (match(source_entry, data)) {
960 *target_entry = source_entry;
966 head = &source_entry->class->locks_after;
968 head = &source_entry->class->locks_before;
970 if (list_empty(head))
974 __cq_enqueue(cq, (unsigned long)source_entry);
976 while (!__cq_empty(cq)) {
977 struct lock_list *lock;
979 __cq_dequeue(cq, (unsigned long *)&lock);
987 head = &lock->class->locks_after;
989 head = &lock->class->locks_before;
991 list_for_each_entry(entry, head, entry) {
992 if (!lock_accessed(entry)) {
993 unsigned int cq_depth;
994 mark_lock_accessed(entry, lock);
995 if (match(entry, data)) {
996 *target_entry = entry;
1001 if (__cq_enqueue(cq, (unsigned long)entry)) {
1005 cq_depth = __cq_get_elem_count(cq);
1006 if (max_bfs_queue_depth < cq_depth)
1007 max_bfs_queue_depth = cq_depth;
1015 static inline int __bfs_forwards(struct lock_list *src_entry,
1017 int (*match)(struct lock_list *entry, void *data),
1018 struct lock_list **target_entry)
1020 return __bfs(src_entry, data, match, target_entry, 1);
1024 static inline int __bfs_backwards(struct lock_list *src_entry,
1026 int (*match)(struct lock_list *entry, void *data),
1027 struct lock_list **target_entry)
1029 return __bfs(src_entry, data, match, target_entry, 0);
1034 * Recursive, forwards-direction lock-dependency checking, used for
1035 * both noncyclic checking and for hardirq-unsafe/softirq-unsafe
1040 * Print a dependency chain entry (this is only done when a deadlock
1041 * has been detected):
1044 print_circular_bug_entry(struct lock_list *target, int depth)
1046 if (debug_locks_silent)
1048 printk("\n-> #%u", depth);
1049 print_lock_name(target->class);
1051 print_stack_trace(&target->trace, 6);
1057 * When a circular dependency is detected, print the
1061 print_circular_bug_header(struct lock_list *entry, unsigned int depth,
1062 struct held_lock *check_src,
1063 struct held_lock *check_tgt)
1065 struct task_struct *curr = current;
1067 if (debug_locks_silent)
1070 printk("\n=======================================================\n");
1071 printk( "[ INFO: possible circular locking dependency detected ]\n");
1072 print_kernel_version();
1073 printk( "-------------------------------------------------------\n");
1074 printk("%s/%d is trying to acquire lock:\n",
1075 curr->comm, task_pid_nr(curr));
1076 print_lock(check_src);
1077 printk("\nbut task is already holding lock:\n");
1078 print_lock(check_tgt);
1079 printk("\nwhich lock already depends on the new lock.\n\n");
1080 printk("\nthe existing dependency chain (in reverse order) is:\n");
1082 print_circular_bug_entry(entry, depth);
1087 static inline int class_equal(struct lock_list *entry, void *data)
1089 return entry->class == data;
1092 static noinline int print_circular_bug(struct lock_list *this,
1093 struct lock_list *target,
1094 struct held_lock *check_src,
1095 struct held_lock *check_tgt)
1097 struct task_struct *curr = current;
1098 struct lock_list *parent;
1101 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1104 if (!save_trace(&this->trace))
1107 depth = get_lock_depth(target);
1109 print_circular_bug_header(target, depth, check_src, check_tgt);
1111 parent = get_lock_parent(target);
1114 print_circular_bug_entry(parent, --depth);
1115 parent = get_lock_parent(parent);
1118 printk("\nother info that might help us debug this:\n\n");
1119 lockdep_print_held_locks(curr);
1121 printk("\nstack backtrace:\n");
1127 static noinline int print_bfs_bug(int ret)
1129 if (!debug_locks_off_graph_unlock())
1132 WARN(1, "lockdep bfs error:%d\n", ret);
1137 static int noop_count(struct lock_list *entry, void *data)
1139 (*(unsigned long *)data)++;
1143 unsigned long __lockdep_count_forward_deps(struct lock_list *this)
1145 unsigned long count = 0;
1146 struct lock_list *uninitialized_var(target_entry);
1148 __bfs_forwards(this, (void *)&count, noop_count, &target_entry);
1152 unsigned long lockdep_count_forward_deps(struct lock_class *class)
1154 unsigned long ret, flags;
1155 struct lock_list this;
1160 local_irq_save(flags);
1161 arch_spin_lock(&lockdep_lock);
1162 ret = __lockdep_count_forward_deps(&this);
1163 arch_spin_unlock(&lockdep_lock);
1164 local_irq_restore(flags);
1169 unsigned long __lockdep_count_backward_deps(struct lock_list *this)
1171 unsigned long count = 0;
1172 struct lock_list *uninitialized_var(target_entry);
1174 __bfs_backwards(this, (void *)&count, noop_count, &target_entry);
1179 unsigned long lockdep_count_backward_deps(struct lock_class *class)
1181 unsigned long ret, flags;
1182 struct lock_list this;
1187 local_irq_save(flags);
1188 arch_spin_lock(&lockdep_lock);
1189 ret = __lockdep_count_backward_deps(&this);
1190 arch_spin_unlock(&lockdep_lock);
1191 local_irq_restore(flags);
1197 * Prove that the dependency graph starting at <entry> can not
1198 * lead to <target>. Print an error and return 0 if it does.
1201 check_noncircular(struct lock_list *root, struct lock_class *target,
1202 struct lock_list **target_entry)
1206 debug_atomic_inc(nr_cyclic_checks);
1208 result = __bfs_forwards(root, target, class_equal, target_entry);
1213 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
1215 * Forwards and backwards subgraph searching, for the purposes of
1216 * proving that two subgraphs can be connected by a new dependency
1217 * without creating any illegal irq-safe -> irq-unsafe lock dependency.
1220 static inline int usage_match(struct lock_list *entry, void *bit)
1222 return entry->class->usage_mask & (1 << (enum lock_usage_bit)bit);
1228 * Find a node in the forwards-direction dependency sub-graph starting
1229 * at @root->class that matches @bit.
1231 * Return 0 if such a node exists in the subgraph, and put that node
1232 * into *@target_entry.
1234 * Return 1 otherwise and keep *@target_entry unchanged.
1235 * Return <0 on error.
1238 find_usage_forwards(struct lock_list *root, enum lock_usage_bit bit,
1239 struct lock_list **target_entry)
1243 debug_atomic_inc(nr_find_usage_forwards_checks);
1245 result = __bfs_forwards(root, (void *)bit, usage_match, target_entry);
1251 * Find a node in the backwards-direction dependency sub-graph starting
1252 * at @root->class that matches @bit.
1254 * Return 0 if such a node exists in the subgraph, and put that node
1255 * into *@target_entry.
1257 * Return 1 otherwise and keep *@target_entry unchanged.
1258 * Return <0 on error.
1261 find_usage_backwards(struct lock_list *root, enum lock_usage_bit bit,
1262 struct lock_list **target_entry)
1266 debug_atomic_inc(nr_find_usage_backwards_checks);
1268 result = __bfs_backwards(root, (void *)bit, usage_match, target_entry);
1273 static void print_lock_class_header(struct lock_class *class, int depth)
1277 printk("%*s->", depth, "");
1278 print_lock_name(class);
1279 printk(" ops: %lu", class->ops);
1282 for (bit = 0; bit < LOCK_USAGE_STATES; bit++) {
1283 if (class->usage_mask & (1 << bit)) {
1286 len += printk("%*s %s", depth, "", usage_str[bit]);
1287 len += printk(" at:\n");
1288 print_stack_trace(class->usage_traces + bit, len);
1291 printk("%*s }\n", depth, "");
1293 printk("%*s ... key at: ",depth,"");
1294 print_ip_sym((unsigned long)class->key);
1298 * printk the shortest lock dependencies from @start to @end in reverse order:
1301 print_shortest_lock_dependencies(struct lock_list *leaf,
1302 struct lock_list *root)
1304 struct lock_list *entry = leaf;
1307 /*compute depth from generated tree by BFS*/
1308 depth = get_lock_depth(leaf);
1311 print_lock_class_header(entry->class, depth);
1312 printk("%*s ... acquired at:\n", depth, "");
1313 print_stack_trace(&entry->trace, 2);
1316 if (depth == 0 && (entry != root)) {
1317 printk("lockdep:%s bad BFS generated tree\n", __func__);
1321 entry = get_lock_parent(entry);
1323 } while (entry && (depth >= 0));
1329 print_bad_irq_dependency(struct task_struct *curr,
1330 struct lock_list *prev_root,
1331 struct lock_list *next_root,
1332 struct lock_list *backwards_entry,
1333 struct lock_list *forwards_entry,
1334 struct held_lock *prev,
1335 struct held_lock *next,
1336 enum lock_usage_bit bit1,
1337 enum lock_usage_bit bit2,
1338 const char *irqclass)
1340 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1343 printk("\n======================================================\n");
1344 printk( "[ INFO: %s-safe -> %s-unsafe lock order detected ]\n",
1345 irqclass, irqclass);
1346 print_kernel_version();
1347 printk( "------------------------------------------------------\n");
1348 printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
1349 curr->comm, task_pid_nr(curr),
1350 curr->hardirq_context, hardirq_count() >> HARDIRQ_SHIFT,
1351 curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT,
1352 curr->hardirqs_enabled,
1353 curr->softirqs_enabled);
1356 printk("\nand this task is already holding:\n");
1358 printk("which would create a new lock dependency:\n");
1359 print_lock_name(hlock_class(prev));
1361 print_lock_name(hlock_class(next));
1364 printk("\nbut this new dependency connects a %s-irq-safe lock:\n",
1366 print_lock_name(backwards_entry->class);
1367 printk("\n... which became %s-irq-safe at:\n", irqclass);
1369 print_stack_trace(backwards_entry->class->usage_traces + bit1, 1);
1371 printk("\nto a %s-irq-unsafe lock:\n", irqclass);
1372 print_lock_name(forwards_entry->class);
1373 printk("\n... which became %s-irq-unsafe at:\n", irqclass);
1376 print_stack_trace(forwards_entry->class->usage_traces + bit2, 1);
1378 printk("\nother info that might help us debug this:\n\n");
1379 lockdep_print_held_locks(curr);
1381 printk("\nthe dependencies between %s-irq-safe lock", irqclass);
1382 printk(" and the holding lock:\n");
1383 if (!save_trace(&prev_root->trace))
1385 print_shortest_lock_dependencies(backwards_entry, prev_root);
1387 printk("\nthe dependencies between the lock to be acquired");
1388 printk(" and %s-irq-unsafe lock:\n", irqclass);
1389 if (!save_trace(&next_root->trace))
1391 print_shortest_lock_dependencies(forwards_entry, next_root);
1393 printk("\nstack backtrace:\n");
1400 check_usage(struct task_struct *curr, struct held_lock *prev,
1401 struct held_lock *next, enum lock_usage_bit bit_backwards,
1402 enum lock_usage_bit bit_forwards, const char *irqclass)
1405 struct lock_list this, that;
1406 struct lock_list *uninitialized_var(target_entry);
1407 struct lock_list *uninitialized_var(target_entry1);
1411 this.class = hlock_class(prev);
1412 ret = find_usage_backwards(&this, bit_backwards, &target_entry);
1414 return print_bfs_bug(ret);
1419 that.class = hlock_class(next);
1420 ret = find_usage_forwards(&that, bit_forwards, &target_entry1);
1422 return print_bfs_bug(ret);
1426 return print_bad_irq_dependency(curr, &this, &that,
1427 target_entry, target_entry1,
1429 bit_backwards, bit_forwards, irqclass);
1432 static const char *state_names[] = {
1433 #define LOCKDEP_STATE(__STATE) \
1434 __stringify(__STATE),
1435 #include "lockdep_states.h"
1436 #undef LOCKDEP_STATE
1439 static const char *state_rnames[] = {
1440 #define LOCKDEP_STATE(__STATE) \
1441 __stringify(__STATE)"-READ",
1442 #include "lockdep_states.h"
1443 #undef LOCKDEP_STATE
1446 static inline const char *state_name(enum lock_usage_bit bit)
1448 return (bit & 1) ? state_rnames[bit >> 2] : state_names[bit >> 2];
1451 static int exclusive_bit(int new_bit)
1459 * bit 0 - write/read
1460 * bit 1 - used_in/enabled
1464 int state = new_bit & ~3;
1465 int dir = new_bit & 2;
1468 * keep state, bit flip the direction and strip read.
1470 return state | (dir ^ 2);
1473 static int check_irq_usage(struct task_struct *curr, struct held_lock *prev,
1474 struct held_lock *next, enum lock_usage_bit bit)
1477 * Prove that the new dependency does not connect a hardirq-safe
1478 * lock with a hardirq-unsafe lock - to achieve this we search
1479 * the backwards-subgraph starting at <prev>, and the
1480 * forwards-subgraph starting at <next>:
1482 if (!check_usage(curr, prev, next, bit,
1483 exclusive_bit(bit), state_name(bit)))
1489 * Prove that the new dependency does not connect a hardirq-safe-read
1490 * lock with a hardirq-unsafe lock - to achieve this we search
1491 * the backwards-subgraph starting at <prev>, and the
1492 * forwards-subgraph starting at <next>:
1494 if (!check_usage(curr, prev, next, bit,
1495 exclusive_bit(bit), state_name(bit)))
1502 check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
1503 struct held_lock *next)
1505 #define LOCKDEP_STATE(__STATE) \
1506 if (!check_irq_usage(curr, prev, next, LOCK_USED_IN_##__STATE)) \
1508 #include "lockdep_states.h"
1509 #undef LOCKDEP_STATE
1514 static void inc_chains(void)
1516 if (current->hardirq_context)
1517 nr_hardirq_chains++;
1519 if (current->softirq_context)
1520 nr_softirq_chains++;
1522 nr_process_chains++;
1529 check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
1530 struct held_lock *next)
1535 static inline void inc_chains(void)
1537 nr_process_chains++;
1543 print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
1544 struct held_lock *next)
1546 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1549 printk("\n=============================================\n");
1550 printk( "[ INFO: possible recursive locking detected ]\n");
1551 print_kernel_version();
1552 printk( "---------------------------------------------\n");
1553 printk("%s/%d is trying to acquire lock:\n",
1554 curr->comm, task_pid_nr(curr));
1556 printk("\nbut task is already holding lock:\n");
1559 printk("\nother info that might help us debug this:\n");
1560 lockdep_print_held_locks(curr);
1562 printk("\nstack backtrace:\n");
1569 * Check whether we are holding such a class already.
1571 * (Note that this has to be done separately, because the graph cannot
1572 * detect such classes of deadlocks.)
1574 * Returns: 0 on deadlock detected, 1 on OK, 2 on recursive read
1577 check_deadlock(struct task_struct *curr, struct held_lock *next,
1578 struct lockdep_map *next_instance, int read)
1580 struct held_lock *prev;
1581 struct held_lock *nest = NULL;
1584 for (i = 0; i < curr->lockdep_depth; i++) {
1585 prev = curr->held_locks + i;
1587 if (prev->instance == next->nest_lock)
1590 if (hlock_class(prev) != hlock_class(next))
1594 * Allow read-after-read recursion of the same
1595 * lock class (i.e. read_lock(lock)+read_lock(lock)):
1597 if ((read == 2) && prev->read)
1601 * We're holding the nest_lock, which serializes this lock's
1602 * nesting behaviour.
1607 return print_deadlock_bug(curr, prev, next);
1613 * There was a chain-cache miss, and we are about to add a new dependency
1614 * to a previous lock. We recursively validate the following rules:
1616 * - would the adding of the <prev> -> <next> dependency create a
1617 * circular dependency in the graph? [== circular deadlock]
1619 * - does the new prev->next dependency connect any hardirq-safe lock
1620 * (in the full backwards-subgraph starting at <prev>) with any
1621 * hardirq-unsafe lock (in the full forwards-subgraph starting at
1622 * <next>)? [== illegal lock inversion with hardirq contexts]
1624 * - does the new prev->next dependency connect any softirq-safe lock
1625 * (in the full backwards-subgraph starting at <prev>) with any
1626 * softirq-unsafe lock (in the full forwards-subgraph starting at
1627 * <next>)? [== illegal lock inversion with softirq contexts]
1629 * any of these scenarios could lead to a deadlock.
1631 * Then if all the validations pass, we add the forwards and backwards
1635 check_prev_add(struct task_struct *curr, struct held_lock *prev,
1636 struct held_lock *next, int distance, int trylock_loop)
1638 struct lock_list *entry;
1640 struct lock_list this;
1641 struct lock_list *uninitialized_var(target_entry);
1643 * Static variable, serialized by the graph_lock().
1645 * We use this static variable to save the stack trace in case
1646 * we call into this function multiple times due to encountering
1647 * trylocks in the held lock stack.
1649 static struct stack_trace trace;
1652 * Prove that the new <prev> -> <next> dependency would not
1653 * create a circular dependency in the graph. (We do this by
1654 * forward-recursing into the graph starting at <next>, and
1655 * checking whether we can reach <prev>.)
1657 * We are using global variables to control the recursion, to
1658 * keep the stackframe size of the recursive functions low:
1660 this.class = hlock_class(next);
1662 ret = check_noncircular(&this, hlock_class(prev), &target_entry);
1664 return print_circular_bug(&this, target_entry, next, prev);
1665 else if (unlikely(ret < 0))
1666 return print_bfs_bug(ret);
1668 if (!check_prev_add_irq(curr, prev, next))
1672 * For recursive read-locks we do all the dependency checks,
1673 * but we dont store read-triggered dependencies (only
1674 * write-triggered dependencies). This ensures that only the
1675 * write-side dependencies matter, and that if for example a
1676 * write-lock never takes any other locks, then the reads are
1677 * equivalent to a NOP.
1679 if (next->read == 2 || prev->read == 2)
1682 * Is the <prev> -> <next> dependency already present?
1684 * (this may occur even though this is a new chain: consider
1685 * e.g. the L1 -> L2 -> L3 -> L4 and the L5 -> L1 -> L2 -> L3
1686 * chains - the second one will be new, but L1 already has
1687 * L2 added to its dependency list, due to the first chain.)
1689 list_for_each_entry(entry, &hlock_class(prev)->locks_after, entry) {
1690 if (entry->class == hlock_class(next)) {
1692 entry->distance = 1;
1697 if (!trylock_loop && !save_trace(&trace))
1701 * Ok, all validations passed, add the new lock
1702 * to the previous lock's dependency list:
1704 ret = add_lock_to_list(hlock_class(prev), hlock_class(next),
1705 &hlock_class(prev)->locks_after,
1706 next->acquire_ip, distance, &trace);
1711 ret = add_lock_to_list(hlock_class(next), hlock_class(prev),
1712 &hlock_class(next)->locks_before,
1713 next->acquire_ip, distance, &trace);
1718 * Debugging printouts:
1720 if (verbose(hlock_class(prev)) || verbose(hlock_class(next))) {
1722 printk("\n new dependency: ");
1723 print_lock_name(hlock_class(prev));
1725 print_lock_name(hlock_class(next));
1728 return graph_lock();
1734 * Add the dependency to all directly-previous locks that are 'relevant'.
1735 * The ones that are relevant are (in increasing distance from curr):
1736 * all consecutive trylock entries and the final non-trylock entry - or
1737 * the end of this context's lock-chain - whichever comes first.
1740 check_prevs_add(struct task_struct *curr, struct held_lock *next)
1742 int depth = curr->lockdep_depth;
1743 int trylock_loop = 0;
1744 struct held_lock *hlock;
1749 * Depth must not be zero for a non-head lock:
1754 * At least two relevant locks must exist for this
1757 if (curr->held_locks[depth].irq_context !=
1758 curr->held_locks[depth-1].irq_context)
1762 int distance = curr->lockdep_depth - depth + 1;
1763 hlock = curr->held_locks + depth-1;
1765 * Only non-recursive-read entries get new dependencies
1768 if (hlock->read != 2) {
1769 if (!check_prev_add(curr, hlock, next,
1770 distance, trylock_loop))
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)
1797 if (!debug_locks_off_graph_unlock())
1805 unsigned long nr_lock_chains;
1806 struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
1807 int nr_chain_hlocks;
1808 static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
1810 struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
1812 return lock_classes + chain_hlocks[chain->base + i];
1816 * Look up a dependency chain. If the key is not present yet then
1817 * add it and return 1 - in this case the new dependency chain is
1818 * validated. If the key is already hashed, return 0.
1819 * (On return with 1 graph_lock is held.)
1821 static inline int lookup_chain_cache(struct task_struct *curr,
1822 struct held_lock *hlock,
1825 struct lock_class *class = hlock_class(hlock);
1826 struct list_head *hash_head = chainhashentry(chain_key);
1827 struct lock_chain *chain;
1828 struct held_lock *hlock_curr, *hlock_next;
1831 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
1834 * We can walk it lock-free, because entries only get added
1837 list_for_each_entry(chain, hash_head, entry) {
1838 if (chain->chain_key == chain_key) {
1840 debug_atomic_inc(chain_lookup_hits);
1841 if (very_verbose(class))
1842 printk("\nhash chain already cached, key: "
1843 "%016Lx tail class: [%p] %s\n",
1844 (unsigned long long)chain_key,
1845 class->key, class->name);
1849 if (very_verbose(class))
1850 printk("\nnew hash chain, key: %016Lx tail class: [%p] %s\n",
1851 (unsigned long long)chain_key, class->key, class->name);
1853 * Allocate a new chain entry from the static array, and add
1859 * We have to walk the chain again locked - to avoid duplicates:
1861 list_for_each_entry(chain, hash_head, entry) {
1862 if (chain->chain_key == chain_key) {
1867 if (unlikely(nr_lock_chains >= MAX_LOCKDEP_CHAINS)) {
1868 if (!debug_locks_off_graph_unlock())
1871 printk("BUG: MAX_LOCKDEP_CHAINS too low!\n");
1872 printk("turning off the locking correctness validator.\n");
1876 chain = lock_chains + nr_lock_chains++;
1877 chain->chain_key = chain_key;
1878 chain->irq_context = hlock->irq_context;
1879 /* Find the first held_lock of current chain */
1881 for (i = curr->lockdep_depth - 1; i >= 0; i--) {
1882 hlock_curr = curr->held_locks + i;
1883 if (hlock_curr->irq_context != hlock_next->irq_context)
1888 chain->depth = curr->lockdep_depth + 1 - i;
1889 cn = nr_chain_hlocks;
1890 while (cn + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS) {
1891 n = cmpxchg(&nr_chain_hlocks, cn, cn + chain->depth);
1896 if (likely(cn + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) {
1898 for (j = 0; j < chain->depth - 1; j++, i++) {
1899 int lock_id = curr->held_locks[i].class_idx - 1;
1900 chain_hlocks[chain->base + j] = lock_id;
1902 chain_hlocks[chain->base + j] = class - lock_classes;
1904 list_add_tail_rcu(&chain->entry, hash_head);
1905 debug_atomic_inc(chain_lookup_misses);
1911 static int validate_chain(struct task_struct *curr, struct lockdep_map *lock,
1912 struct held_lock *hlock, int chain_head, u64 chain_key)
1915 * Trylock needs to maintain the stack of held locks, but it
1916 * does not add new dependencies, because trylock can be done
1919 * We look up the chain_key and do the O(N^2) check and update of
1920 * the dependencies only if this is a new dependency chain.
1921 * (If lookup_chain_cache() returns with 1 it acquires
1922 * graph_lock for us)
1924 if (!hlock->trylock && (hlock->check == 2) &&
1925 lookup_chain_cache(curr, hlock, chain_key)) {
1927 * Check whether last held lock:
1929 * - is irq-safe, if this lock is irq-unsafe
1930 * - is softirq-safe, if this lock is hardirq-unsafe
1932 * And check whether the new lock's dependency graph
1933 * could lead back to the previous lock.
1935 * any of these scenarios could lead to a deadlock. If
1938 int ret = check_deadlock(curr, hlock, lock, hlock->read);
1943 * Mark recursive read, as we jump over it when
1944 * building dependencies (just like we jump over
1950 * Add dependency only if this lock is not the head
1951 * of the chain, and if it's not a secondary read-lock:
1953 if (!chain_head && ret != 2)
1954 if (!check_prevs_add(curr, hlock))
1958 /* after lookup_chain_cache(): */
1959 if (unlikely(!debug_locks))
1965 static inline int validate_chain(struct task_struct *curr,
1966 struct lockdep_map *lock, struct held_lock *hlock,
1967 int chain_head, u64 chain_key)
1974 * We are building curr_chain_key incrementally, so double-check
1975 * it from scratch, to make sure that it's done correctly:
1977 static void check_chain_key(struct task_struct *curr)
1979 #ifdef CONFIG_DEBUG_LOCKDEP
1980 struct held_lock *hlock, *prev_hlock = NULL;
1984 for (i = 0; i < curr->lockdep_depth; i++) {
1985 hlock = curr->held_locks + i;
1986 if (chain_key != hlock->prev_chain_key) {
1988 WARN(1, "hm#1, depth: %u [%u], %016Lx != %016Lx\n",
1989 curr->lockdep_depth, i,
1990 (unsigned long long)chain_key,
1991 (unsigned long long)hlock->prev_chain_key);
1994 id = hlock->class_idx - 1;
1995 if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
1998 if (prev_hlock && (prev_hlock->irq_context !=
1999 hlock->irq_context))
2001 chain_key = iterate_chain_key(chain_key, id);
2004 if (chain_key != curr->curr_chain_key) {
2006 WARN(1, "hm#2, depth: %u [%u], %016Lx != %016Lx\n",
2007 curr->lockdep_depth, i,
2008 (unsigned long long)chain_key,
2009 (unsigned long long)curr->curr_chain_key);
2015 print_usage_bug(struct task_struct *curr, struct held_lock *this,
2016 enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
2018 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2021 printk("\n=================================\n");
2022 printk( "[ INFO: inconsistent lock state ]\n");
2023 print_kernel_version();
2024 printk( "---------------------------------\n");
2026 printk("inconsistent {%s} -> {%s} usage.\n",
2027 usage_str[prev_bit], usage_str[new_bit]);
2029 printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] takes:\n",
2030 curr->comm, task_pid_nr(curr),
2031 trace_hardirq_context(curr), hardirq_count() >> HARDIRQ_SHIFT,
2032 trace_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT,
2033 trace_hardirqs_enabled(curr),
2034 trace_softirqs_enabled(curr));
2037 printk("{%s} state was registered at:\n", usage_str[prev_bit]);
2038 print_stack_trace(hlock_class(this)->usage_traces + prev_bit, 1);
2040 print_irqtrace_events(curr);
2041 printk("\nother info that might help us debug this:\n");
2042 lockdep_print_held_locks(curr);
2044 printk("\nstack backtrace:\n");
2051 * Print out an error if an invalid bit is set:
2054 valid_state(struct task_struct *curr, struct held_lock *this,
2055 enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit)
2057 if (unlikely(hlock_class(this)->usage_mask & (1 << bad_bit)))
2058 return print_usage_bug(curr, this, bad_bit, new_bit);
2062 static int mark_lock(struct task_struct *curr, struct held_lock *this,
2063 enum lock_usage_bit new_bit);
2065 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
2068 * print irq inversion bug:
2071 print_irq_inversion_bug(struct task_struct *curr,
2072 struct lock_list *root, struct lock_list *other,
2073 struct held_lock *this, int forwards,
2074 const char *irqclass)
2076 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2079 printk("\n=========================================================\n");
2080 printk( "[ INFO: possible irq lock inversion dependency detected ]\n");
2081 print_kernel_version();
2082 printk( "---------------------------------------------------------\n");
2083 printk("%s/%d just changed the state of lock:\n",
2084 curr->comm, task_pid_nr(curr));
2087 printk("but this lock took another, %s-unsafe lock in the past:\n", irqclass);
2089 printk("but this lock was taken by another, %s-safe lock in the past:\n", irqclass);
2090 print_lock_name(other->class);
2091 printk("\n\nand interrupts could create inverse lock ordering between them.\n\n");
2093 printk("\nother info that might help us debug this:\n");
2094 lockdep_print_held_locks(curr);
2096 printk("\nthe shortest dependencies between 2nd lock and 1st lock:\n");
2097 if (!save_trace(&root->trace))
2099 print_shortest_lock_dependencies(other, root);
2101 printk("\nstack backtrace:\n");
2108 * Prove that in the forwards-direction subgraph starting at <this>
2109 * there is no lock matching <mask>:
2112 check_usage_forwards(struct task_struct *curr, struct held_lock *this,
2113 enum lock_usage_bit bit, const char *irqclass)
2116 struct lock_list root;
2117 struct lock_list *uninitialized_var(target_entry);
2120 root.class = hlock_class(this);
2121 ret = find_usage_forwards(&root, bit, &target_entry);
2123 return print_bfs_bug(ret);
2127 return print_irq_inversion_bug(curr, &root, target_entry,
2132 * Prove that in the backwards-direction subgraph starting at <this>
2133 * there is no lock matching <mask>:
2136 check_usage_backwards(struct task_struct *curr, struct held_lock *this,
2137 enum lock_usage_bit bit, const char *irqclass)
2140 struct lock_list root;
2141 struct lock_list *uninitialized_var(target_entry);
2144 root.class = hlock_class(this);
2145 ret = find_usage_backwards(&root, bit, &target_entry);
2147 return print_bfs_bug(ret);
2151 return print_irq_inversion_bug(curr, &root, target_entry,
2155 void print_irqtrace_events(struct task_struct *curr)
2157 printk("irq event stamp: %u\n", curr->irq_events);
2158 printk("hardirqs last enabled at (%u): ", curr->hardirq_enable_event);
2159 print_ip_sym(curr->hardirq_enable_ip);
2160 printk("hardirqs last disabled at (%u): ", curr->hardirq_disable_event);
2161 print_ip_sym(curr->hardirq_disable_ip);
2162 printk("softirqs last enabled at (%u): ", curr->softirq_enable_event);
2163 print_ip_sym(curr->softirq_enable_ip);
2164 printk("softirqs last disabled at (%u): ", curr->softirq_disable_event);
2165 print_ip_sym(curr->softirq_disable_ip);
2168 static int HARDIRQ_verbose(struct lock_class *class)
2171 return class_filter(class);
2176 static int SOFTIRQ_verbose(struct lock_class *class)
2179 return class_filter(class);
2184 static int RECLAIM_FS_verbose(struct lock_class *class)
2187 return class_filter(class);
2192 #define STRICT_READ_CHECKS 1
2194 static int (*state_verbose_f[])(struct lock_class *class) = {
2195 #define LOCKDEP_STATE(__STATE) \
2197 #include "lockdep_states.h"
2198 #undef LOCKDEP_STATE
2201 static inline int state_verbose(enum lock_usage_bit bit,
2202 struct lock_class *class)
2204 return state_verbose_f[bit >> 2](class);
2207 typedef int (*check_usage_f)(struct task_struct *, struct held_lock *,
2208 enum lock_usage_bit bit, const char *name);
2211 mark_lock_irq(struct task_struct *curr, struct held_lock *this,
2212 enum lock_usage_bit new_bit)
2214 int excl_bit = exclusive_bit(new_bit);
2215 int read = new_bit & 1;
2216 int dir = new_bit & 2;
2219 * mark USED_IN has to look forwards -- to ensure no dependency
2220 * has ENABLED state, which would allow recursion deadlocks.
2222 * mark ENABLED has to look backwards -- to ensure no dependee
2223 * has USED_IN state, which, again, would allow recursion deadlocks.
2225 check_usage_f usage = dir ?
2226 check_usage_backwards : check_usage_forwards;
2229 * Validate that this particular lock does not have conflicting
2232 if (!valid_state(curr, this, new_bit, excl_bit))
2236 * Validate that the lock dependencies don't have conflicting usage
2239 if ((!read || !dir || STRICT_READ_CHECKS) &&
2240 !usage(curr, this, excl_bit, state_name(new_bit & ~1)))
2244 * Check for read in write conflicts
2247 if (!valid_state(curr, this, new_bit, excl_bit + 1))
2250 if (STRICT_READ_CHECKS &&
2251 !usage(curr, this, excl_bit + 1,
2252 state_name(new_bit + 1)))
2256 if (state_verbose(new_bit, hlock_class(this)))
2263 #define LOCKDEP_STATE(__STATE) __STATE,
2264 #include "lockdep_states.h"
2265 #undef LOCKDEP_STATE
2269 * Mark all held locks with a usage bit:
2272 mark_held_locks(struct task_struct *curr, enum mark_type mark)
2274 enum lock_usage_bit usage_bit;
2275 struct held_lock *hlock;
2278 for (i = 0; i < curr->lockdep_depth; i++) {
2279 hlock = curr->held_locks + i;
2281 usage_bit = 2 + (mark << 2); /* ENABLED */
2283 usage_bit += 1; /* READ */
2285 BUG_ON(usage_bit >= LOCK_USAGE_STATES);
2287 if (!mark_lock(curr, hlock, usage_bit))
2295 * Debugging helper: via this flag we know that we are in
2296 * 'early bootup code', and will warn about any invalid irqs-on event:
2298 static int early_boot_irqs_enabled;
2300 void early_boot_irqs_off(void)
2302 early_boot_irqs_enabled = 0;
2305 void early_boot_irqs_on(void)
2307 early_boot_irqs_enabled = 1;
2311 * Hardirqs will be enabled:
2313 void trace_hardirqs_on_caller(unsigned long ip)
2315 struct task_struct *curr = current;
2317 time_hardirqs_on(CALLER_ADDR0, ip);
2319 if (unlikely(!debug_locks || current->lockdep_recursion))
2322 if (DEBUG_LOCKS_WARN_ON(unlikely(!early_boot_irqs_enabled)))
2325 if (unlikely(curr->hardirqs_enabled)) {
2327 * Neither irq nor preemption are disabled here
2328 * so this is racy by nature but loosing one hit
2329 * in a stat is not a big deal.
2331 __debug_atomic_inc(redundant_hardirqs_on);
2334 /* we'll do an OFF -> ON transition: */
2335 curr->hardirqs_enabled = 1;
2337 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2339 if (DEBUG_LOCKS_WARN_ON(current->hardirq_context))
2342 * We are going to turn hardirqs on, so set the
2343 * usage bit for all held locks:
2345 if (!mark_held_locks(curr, HARDIRQ))
2348 * If we have softirqs enabled, then set the usage
2349 * bit for all held locks. (disabled hardirqs prevented
2350 * this bit from being set before)
2352 if (curr->softirqs_enabled)
2353 if (!mark_held_locks(curr, SOFTIRQ))
2356 curr->hardirq_enable_ip = ip;
2357 curr->hardirq_enable_event = ++curr->irq_events;
2358 debug_atomic_inc(hardirqs_on_events);
2360 EXPORT_SYMBOL(trace_hardirqs_on_caller);
2362 void trace_hardirqs_on(void)
2364 trace_hardirqs_on_caller(CALLER_ADDR0);
2366 EXPORT_SYMBOL(trace_hardirqs_on);
2369 * Hardirqs were disabled:
2371 void trace_hardirqs_off_caller(unsigned long ip)
2373 struct task_struct *curr = current;
2375 time_hardirqs_off(CALLER_ADDR0, ip);
2377 if (unlikely(!debug_locks || current->lockdep_recursion))
2380 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2383 if (curr->hardirqs_enabled) {
2385 * We have done an ON -> OFF transition:
2387 curr->hardirqs_enabled = 0;
2388 curr->hardirq_disable_ip = ip;
2389 curr->hardirq_disable_event = ++curr->irq_events;
2390 debug_atomic_inc(hardirqs_off_events);
2392 debug_atomic_inc(redundant_hardirqs_off);
2394 EXPORT_SYMBOL(trace_hardirqs_off_caller);
2396 void trace_hardirqs_off(void)
2398 trace_hardirqs_off_caller(CALLER_ADDR0);
2400 EXPORT_SYMBOL(trace_hardirqs_off);
2403 * Softirqs will be enabled:
2405 void trace_softirqs_on(unsigned long ip)
2407 struct task_struct *curr = current;
2409 if (unlikely(!debug_locks))
2412 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2415 if (curr->softirqs_enabled) {
2416 debug_atomic_inc(redundant_softirqs_on);
2421 * We'll do an OFF -> ON transition:
2423 curr->softirqs_enabled = 1;
2424 curr->softirq_enable_ip = ip;
2425 curr->softirq_enable_event = ++curr->irq_events;
2426 debug_atomic_inc(softirqs_on_events);
2428 * We are going to turn softirqs on, so set the
2429 * usage bit for all held locks, if hardirqs are
2432 if (curr->hardirqs_enabled)
2433 mark_held_locks(curr, SOFTIRQ);
2437 * Softirqs were disabled:
2439 void trace_softirqs_off(unsigned long ip)
2441 struct task_struct *curr = current;
2443 if (unlikely(!debug_locks))
2446 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2449 if (curr->softirqs_enabled) {
2451 * We have done an ON -> OFF transition:
2453 curr->softirqs_enabled = 0;
2454 curr->softirq_disable_ip = ip;
2455 curr->softirq_disable_event = ++curr->irq_events;
2456 debug_atomic_inc(softirqs_off_events);
2457 DEBUG_LOCKS_WARN_ON(!softirq_count());
2459 debug_atomic_inc(redundant_softirqs_off);
2462 static void __lockdep_trace_alloc(gfp_t gfp_mask, unsigned long flags)
2464 struct task_struct *curr = current;
2466 if (unlikely(!debug_locks))
2469 /* no reclaim without waiting on it */
2470 if (!(gfp_mask & __GFP_WAIT))
2473 /* this guy won't enter reclaim */
2474 if ((curr->flags & PF_MEMALLOC) && !(gfp_mask & __GFP_NOMEMALLOC))
2477 /* We're only interested __GFP_FS allocations for now */
2478 if (!(gfp_mask & __GFP_FS))
2481 if (DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags)))
2484 mark_held_locks(curr, RECLAIM_FS);
2487 static void check_flags(unsigned long flags);
2489 void lockdep_trace_alloc(gfp_t gfp_mask)
2491 unsigned long flags;
2493 if (unlikely(current->lockdep_recursion))
2496 raw_local_irq_save(flags);
2498 current->lockdep_recursion = 1;
2499 __lockdep_trace_alloc(gfp_mask, flags);
2500 current->lockdep_recursion = 0;
2501 raw_local_irq_restore(flags);
2504 static int mark_irqflags(struct task_struct *curr, struct held_lock *hlock)
2507 * If non-trylock use in a hardirq or softirq context, then
2508 * mark the lock as used in these contexts:
2510 if (!hlock->trylock) {
2512 if (curr->hardirq_context)
2513 if (!mark_lock(curr, hlock,
2514 LOCK_USED_IN_HARDIRQ_READ))
2516 if (curr->softirq_context)
2517 if (!mark_lock(curr, hlock,
2518 LOCK_USED_IN_SOFTIRQ_READ))
2521 if (curr->hardirq_context)
2522 if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ))
2524 if (curr->softirq_context)
2525 if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ))
2529 if (!hlock->hardirqs_off) {
2531 if (!mark_lock(curr, hlock,
2532 LOCK_ENABLED_HARDIRQ_READ))
2534 if (curr->softirqs_enabled)
2535 if (!mark_lock(curr, hlock,
2536 LOCK_ENABLED_SOFTIRQ_READ))
2539 if (!mark_lock(curr, hlock,
2540 LOCK_ENABLED_HARDIRQ))
2542 if (curr->softirqs_enabled)
2543 if (!mark_lock(curr, hlock,
2544 LOCK_ENABLED_SOFTIRQ))
2550 * We reuse the irq context infrastructure more broadly as a general
2551 * context checking code. This tests GFP_FS recursion (a lock taken
2552 * during reclaim for a GFP_FS allocation is held over a GFP_FS
2555 if (!hlock->trylock && (curr->lockdep_reclaim_gfp & __GFP_FS)) {
2557 if (!mark_lock(curr, hlock, LOCK_USED_IN_RECLAIM_FS_READ))
2560 if (!mark_lock(curr, hlock, LOCK_USED_IN_RECLAIM_FS))
2568 static int separate_irq_context(struct task_struct *curr,
2569 struct held_lock *hlock)
2571 unsigned int depth = curr->lockdep_depth;
2574 * Keep track of points where we cross into an interrupt context:
2576 hlock->irq_context = 2*(curr->hardirq_context ? 1 : 0) +
2577 curr->softirq_context;
2579 struct held_lock *prev_hlock;
2581 prev_hlock = curr->held_locks + depth-1;
2583 * If we cross into another context, reset the
2584 * hash key (this also prevents the checking and the
2585 * adding of the dependency to 'prev'):
2587 if (prev_hlock->irq_context != hlock->irq_context)
2596 int mark_lock_irq(struct task_struct *curr, struct held_lock *this,
2597 enum lock_usage_bit new_bit)
2603 static inline int mark_irqflags(struct task_struct *curr,
2604 struct held_lock *hlock)
2609 static inline int separate_irq_context(struct task_struct *curr,
2610 struct held_lock *hlock)
2615 void lockdep_trace_alloc(gfp_t gfp_mask)
2622 * Mark a lock with a usage bit, and validate the state transition:
2624 static int mark_lock(struct task_struct *curr, struct held_lock *this,
2625 enum lock_usage_bit new_bit)
2627 unsigned int new_mask = 1 << new_bit, ret = 1;
2630 * If already set then do not dirty the cacheline,
2631 * nor do any checks:
2633 if (likely(hlock_class(this)->usage_mask & new_mask))
2639 * Make sure we didnt race:
2641 if (unlikely(hlock_class(this)->usage_mask & new_mask)) {
2646 hlock_class(this)->usage_mask |= new_mask;
2648 if (!save_trace(hlock_class(this)->usage_traces + new_bit))
2652 #define LOCKDEP_STATE(__STATE) \
2653 case LOCK_USED_IN_##__STATE: \
2654 case LOCK_USED_IN_##__STATE##_READ: \
2655 case LOCK_ENABLED_##__STATE: \
2656 case LOCK_ENABLED_##__STATE##_READ:
2657 #include "lockdep_states.h"
2658 #undef LOCKDEP_STATE
2659 ret = mark_lock_irq(curr, this, new_bit);
2664 debug_atomic_dec(nr_unused_locks);
2667 if (!debug_locks_off_graph_unlock())
2676 * We must printk outside of the graph_lock:
2679 printk("\nmarked lock as {%s}:\n", usage_str[new_bit]);
2681 print_irqtrace_events(curr);
2689 * Initialize a lock instance's lock-class mapping info:
2691 void lockdep_init_map(struct lockdep_map *lock, const char *name,
2692 struct lock_class_key *key, int subclass)
2696 for (i = 0; i < NR_LOCKDEP_CACHING_CLASSES; i++)
2697 lock->class_cache[i] = NULL;
2699 #ifdef CONFIG_LOCK_STAT
2700 lock->cpu = raw_smp_processor_id();
2703 if (DEBUG_LOCKS_WARN_ON(!name)) {
2704 lock->name = "NULL";
2710 if (DEBUG_LOCKS_WARN_ON(!key))
2713 * Sanity check, the lock-class key must be persistent:
2715 if (!static_obj(key)) {
2716 printk("BUG: key %p not in .data!\n", key);
2717 DEBUG_LOCKS_WARN_ON(1);
2722 if (unlikely(!debug_locks))
2726 register_lock_class(lock, subclass, 1);
2728 EXPORT_SYMBOL_GPL(lockdep_init_map);
2730 struct lock_class_key __lockdep_no_validate__;
2733 * This gets called for every mutex_lock*()/spin_lock*() operation.
2734 * We maintain the dependency maps and validate the locking attempt:
2736 static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
2737 int trylock, int read, int check, int hardirqs_off,
2738 struct lockdep_map *nest_lock, unsigned long ip,
2741 struct task_struct *curr = current;
2742 struct lock_class *class = NULL;
2743 struct held_lock *hlock;
2744 unsigned int depth, id;
2752 if (unlikely(!debug_locks))
2755 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2758 if (lock->key == &__lockdep_no_validate__)
2761 if (subclass < NR_LOCKDEP_CACHING_CLASSES)
2762 class = lock->class_cache[subclass];
2766 if (unlikely(!class)) {
2767 class = register_lock_class(lock, subclass, 0);
2771 atomic_inc((atomic_t *)&class->ops);
2772 if (very_verbose(class)) {
2773 printk("\nacquire class [%p] %s", class->key, class->name);
2774 if (class->name_version > 1)
2775 printk("#%d", class->name_version);
2781 * Add the lock to the list of currently held locks.
2782 * (we dont increase the depth just yet, up until the
2783 * dependency checks are done)
2785 depth = curr->lockdep_depth;
2786 if (DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH))
2789 class_idx = class - lock_classes + 1;
2792 hlock = curr->held_locks + depth - 1;
2793 if (hlock->class_idx == class_idx && nest_lock) {
2794 if (hlock->references)
2795 hlock->references++;
2797 hlock->references = 2;
2803 hlock = curr->held_locks + depth;
2804 if (DEBUG_LOCKS_WARN_ON(!class))
2806 hlock->class_idx = class_idx;
2807 hlock->acquire_ip = ip;
2808 hlock->instance = lock;
2809 hlock->nest_lock = nest_lock;
2810 hlock->trylock = trylock;
2812 hlock->check = check;
2813 hlock->hardirqs_off = !!hardirqs_off;
2814 hlock->references = references;
2815 #ifdef CONFIG_LOCK_STAT
2816 hlock->waittime_stamp = 0;
2817 hlock->holdtime_stamp = lockstat_clock();
2820 if (check == 2 && !mark_irqflags(curr, hlock))
2823 /* mark it as used: */
2824 if (!mark_lock(curr, hlock, LOCK_USED))
2828 * Calculate the chain hash: it's the combined hash of all the
2829 * lock keys along the dependency chain. We save the hash value
2830 * at every step so that we can get the current hash easily
2831 * after unlock. The chain hash is then used to cache dependency
2834 * The 'key ID' is what is the most compact key value to drive
2835 * the hash, not class->key.
2837 id = class - lock_classes;
2838 if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
2841 chain_key = curr->curr_chain_key;
2843 if (DEBUG_LOCKS_WARN_ON(chain_key != 0))
2848 hlock->prev_chain_key = chain_key;
2849 if (separate_irq_context(curr, hlock)) {
2853 chain_key = iterate_chain_key(chain_key, id);
2855 if (!validate_chain(curr, lock, hlock, chain_head, chain_key))
2858 curr->curr_chain_key = chain_key;
2859 curr->lockdep_depth++;
2860 check_chain_key(curr);
2861 #ifdef CONFIG_DEBUG_LOCKDEP
2862 if (unlikely(!debug_locks))
2865 if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
2867 printk("BUG: MAX_LOCK_DEPTH too low!\n");
2868 printk("turning off the locking correctness validator.\n");
2873 if (unlikely(curr->lockdep_depth > max_lockdep_depth))
2874 max_lockdep_depth = curr->lockdep_depth;
2880 print_unlock_inbalance_bug(struct task_struct *curr, struct lockdep_map *lock,
2883 if (!debug_locks_off())
2885 if (debug_locks_silent)
2888 printk("\n=====================================\n");
2889 printk( "[ BUG: bad unlock balance detected! ]\n");
2890 printk( "-------------------------------------\n");
2891 printk("%s/%d is trying to release lock (",
2892 curr->comm, task_pid_nr(curr));
2893 print_lockdep_cache(lock);
2896 printk("but there are no more locks to release!\n");
2897 printk("\nother info that might help us debug this:\n");
2898 lockdep_print_held_locks(curr);
2900 printk("\nstack backtrace:\n");
2907 * Common debugging checks for both nested and non-nested unlock:
2909 static int check_unlock(struct task_struct *curr, struct lockdep_map *lock,
2912 if (unlikely(!debug_locks))
2914 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2917 if (curr->lockdep_depth <= 0)
2918 return print_unlock_inbalance_bug(curr, lock, ip);
2923 static int match_held_lock(struct held_lock *hlock, struct lockdep_map *lock)
2925 if (hlock->instance == lock)
2928 if (hlock->references) {
2929 struct lock_class *class = lock->class_cache[0];
2932 class = look_up_lock_class(lock, 0);
2934 if (DEBUG_LOCKS_WARN_ON(!class))
2937 if (DEBUG_LOCKS_WARN_ON(!hlock->nest_lock))
2940 if (hlock->class_idx == class - lock_classes + 1)
2948 __lock_set_class(struct lockdep_map *lock, const char *name,
2949 struct lock_class_key *key, unsigned int subclass,
2952 struct task_struct *curr = current;
2953 struct held_lock *hlock, *prev_hlock;
2954 struct lock_class *class;
2958 depth = curr->lockdep_depth;
2959 if (DEBUG_LOCKS_WARN_ON(!depth))
2963 for (i = depth-1; i >= 0; i--) {
2964 hlock = curr->held_locks + i;
2966 * We must not cross into another context:
2968 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
2970 if (match_held_lock(hlock, lock))
2974 return print_unlock_inbalance_bug(curr, lock, ip);
2977 lockdep_init_map(lock, name, key, 0);
2978 class = register_lock_class(lock, subclass, 0);
2979 hlock->class_idx = class - lock_classes + 1;
2981 curr->lockdep_depth = i;
2982 curr->curr_chain_key = hlock->prev_chain_key;
2984 for (; i < depth; i++) {
2985 hlock = curr->held_locks + i;
2986 if (!__lock_acquire(hlock->instance,
2987 hlock_class(hlock)->subclass, hlock->trylock,
2988 hlock->read, hlock->check, hlock->hardirqs_off,
2989 hlock->nest_lock, hlock->acquire_ip,
2994 if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth))
3000 * Remove the lock to the list of currently held locks in a
3001 * potentially non-nested (out of order) manner. This is a
3002 * relatively rare operation, as all the unlock APIs default
3003 * to nested mode (which uses lock_release()):
3006 lock_release_non_nested(struct task_struct *curr,
3007 struct lockdep_map *lock, unsigned long ip)
3009 struct held_lock *hlock, *prev_hlock;
3014 * Check whether the lock exists in the current stack
3017 depth = curr->lockdep_depth;
3018 if (DEBUG_LOCKS_WARN_ON(!depth))
3022 for (i = depth-1; i >= 0; i--) {
3023 hlock = curr->held_locks + i;
3025 * We must not cross into another context:
3027 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3029 if (match_held_lock(hlock, lock))
3033 return print_unlock_inbalance_bug(curr, lock, ip);
3036 if (hlock->instance == lock)
3037 lock_release_holdtime(hlock);
3039 if (hlock->references) {
3040 hlock->references--;
3041 if (hlock->references) {
3043 * We had, and after removing one, still have
3044 * references, the current lock stack is still
3045 * valid. We're done!
3052 * We have the right lock to unlock, 'hlock' points to it.
3053 * Now we remove it from the stack, and add back the other
3054 * entries (if any), recalculating the hash along the way:
3057 curr->lockdep_depth = i;
3058 curr->curr_chain_key = hlock->prev_chain_key;
3060 for (i++; i < depth; i++) {
3061 hlock = curr->held_locks + i;
3062 if (!__lock_acquire(hlock->instance,
3063 hlock_class(hlock)->subclass, hlock->trylock,
3064 hlock->read, hlock->check, hlock->hardirqs_off,
3065 hlock->nest_lock, hlock->acquire_ip,
3070 if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - 1))
3076 * Remove the lock to the list of currently held locks - this gets
3077 * called on mutex_unlock()/spin_unlock*() (or on a failed
3078 * mutex_lock_interruptible()). This is done for unlocks that nest
3079 * perfectly. (i.e. the current top of the lock-stack is unlocked)
3081 static int lock_release_nested(struct task_struct *curr,
3082 struct lockdep_map *lock, unsigned long ip)
3084 struct held_lock *hlock;
3088 * Pop off the top of the lock stack:
3090 depth = curr->lockdep_depth - 1;
3091 hlock = curr->held_locks + depth;
3094 * Is the unlock non-nested:
3096 if (hlock->instance != lock || hlock->references)
3097 return lock_release_non_nested(curr, lock, ip);
3098 curr->lockdep_depth--;
3100 if (DEBUG_LOCKS_WARN_ON(!depth && (hlock->prev_chain_key != 0)))
3103 curr->curr_chain_key = hlock->prev_chain_key;
3105 lock_release_holdtime(hlock);
3107 #ifdef CONFIG_DEBUG_LOCKDEP
3108 hlock->prev_chain_key = 0;
3109 hlock->class_idx = 0;
3110 hlock->acquire_ip = 0;
3111 hlock->irq_context = 0;
3117 * Remove the lock to the list of currently held locks - this gets
3118 * called on mutex_unlock()/spin_unlock*() (or on a failed
3119 * mutex_lock_interruptible()). This is done for unlocks that nest
3120 * perfectly. (i.e. the current top of the lock-stack is unlocked)
3123 __lock_release(struct lockdep_map *lock, int nested, unsigned long ip)
3125 struct task_struct *curr = current;
3127 if (!check_unlock(curr, lock, ip))
3131 if (!lock_release_nested(curr, lock, ip))
3134 if (!lock_release_non_nested(curr, lock, ip))
3138 check_chain_key(curr);
3141 static int __lock_is_held(struct lockdep_map *lock)
3143 struct task_struct *curr = current;
3146 for (i = 0; i < curr->lockdep_depth; i++) {
3147 struct held_lock *hlock = curr->held_locks + i;
3149 if (match_held_lock(hlock, lock))
3157 * Check whether we follow the irq-flags state precisely:
3159 static void check_flags(unsigned long flags)
3161 #if defined(CONFIG_PROVE_LOCKING) && defined(CONFIG_DEBUG_LOCKDEP) && \
3162 defined(CONFIG_TRACE_IRQFLAGS)
3166 if (irqs_disabled_flags(flags)) {
3167 if (DEBUG_LOCKS_WARN_ON(current->hardirqs_enabled)) {
3168 printk("possible reason: unannotated irqs-off.\n");
3171 if (DEBUG_LOCKS_WARN_ON(!current->hardirqs_enabled)) {
3172 printk("possible reason: unannotated irqs-on.\n");
3177 * We dont accurately track softirq state in e.g.
3178 * hardirq contexts (such as on 4KSTACKS), so only
3179 * check if not in hardirq contexts:
3181 if (!hardirq_count()) {
3182 if (softirq_count())
3183 DEBUG_LOCKS_WARN_ON(current->softirqs_enabled);
3185 DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled);
3189 print_irqtrace_events(current);
3193 void lock_set_class(struct lockdep_map *lock, const char *name,
3194 struct lock_class_key *key, unsigned int subclass,
3197 unsigned long flags;
3199 if (unlikely(current->lockdep_recursion))
3202 raw_local_irq_save(flags);
3203 current->lockdep_recursion = 1;
3205 if (__lock_set_class(lock, name, key, subclass, ip))
3206 check_chain_key(current);
3207 current->lockdep_recursion = 0;
3208 raw_local_irq_restore(flags);
3210 EXPORT_SYMBOL_GPL(lock_set_class);
3213 * We are not always called with irqs disabled - do that here,
3214 * and also avoid lockdep recursion:
3216 void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
3217 int trylock, int read, int check,
3218 struct lockdep_map *nest_lock, unsigned long ip)
3220 unsigned long flags;
3222 if (unlikely(current->lockdep_recursion))
3225 raw_local_irq_save(flags);
3228 current->lockdep_recursion = 1;
3229 trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip);
3230 __lock_acquire(lock, subclass, trylock, read, check,
3231 irqs_disabled_flags(flags), nest_lock, ip, 0);
3232 current->lockdep_recursion = 0;
3233 raw_local_irq_restore(flags);
3235 EXPORT_SYMBOL_GPL(lock_acquire);
3237 void lock_release(struct lockdep_map *lock, int nested,
3240 unsigned long flags;
3242 if (unlikely(current->lockdep_recursion))
3245 raw_local_irq_save(flags);
3247 current->lockdep_recursion = 1;
3248 trace_lock_release(lock, ip);
3249 __lock_release(lock, nested, ip);
3250 current->lockdep_recursion = 0;
3251 raw_local_irq_restore(flags);
3253 EXPORT_SYMBOL_GPL(lock_release);
3255 int lock_is_held(struct lockdep_map *lock)
3257 unsigned long flags;
3260 if (unlikely(current->lockdep_recursion))
3263 raw_local_irq_save(flags);
3266 current->lockdep_recursion = 1;
3267 ret = __lock_is_held(lock);
3268 current->lockdep_recursion = 0;
3269 raw_local_irq_restore(flags);
3273 EXPORT_SYMBOL_GPL(lock_is_held);
3275 void lockdep_set_current_reclaim_state(gfp_t gfp_mask)
3277 current->lockdep_reclaim_gfp = gfp_mask;
3280 void lockdep_clear_current_reclaim_state(void)
3282 current->lockdep_reclaim_gfp = 0;
3285 #ifdef CONFIG_LOCK_STAT
3287 print_lock_contention_bug(struct task_struct *curr, struct lockdep_map *lock,
3290 if (!debug_locks_off())
3292 if (debug_locks_silent)
3295 printk("\n=================================\n");
3296 printk( "[ BUG: bad contention detected! ]\n");
3297 printk( "---------------------------------\n");
3298 printk("%s/%d is trying to contend lock (",
3299 curr->comm, task_pid_nr(curr));
3300 print_lockdep_cache(lock);
3303 printk("but there are no locks held!\n");
3304 printk("\nother info that might help us debug this:\n");
3305 lockdep_print_held_locks(curr);
3307 printk("\nstack backtrace:\n");
3314 __lock_contended(struct lockdep_map *lock, unsigned long ip)
3316 struct task_struct *curr = current;
3317 struct held_lock *hlock, *prev_hlock;
3318 struct lock_class_stats *stats;
3320 int i, contention_point, contending_point;
3322 depth = curr->lockdep_depth;
3323 if (DEBUG_LOCKS_WARN_ON(!depth))
3327 for (i = depth-1; i >= 0; i--) {
3328 hlock = curr->held_locks + i;
3330 * We must not cross into another context:
3332 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3334 if (match_held_lock(hlock, lock))
3338 print_lock_contention_bug(curr, lock, ip);
3342 if (hlock->instance != lock)
3345 hlock->waittime_stamp = lockstat_clock();
3347 contention_point = lock_point(hlock_class(hlock)->contention_point, ip);
3348 contending_point = lock_point(hlock_class(hlock)->contending_point,
3351 stats = get_lock_stats(hlock_class(hlock));
3352 if (contention_point < LOCKSTAT_POINTS)
3353 stats->contention_point[contention_point]++;
3354 if (contending_point < LOCKSTAT_POINTS)
3355 stats->contending_point[contending_point]++;
3356 if (lock->cpu != smp_processor_id())
3357 stats->bounces[bounce_contended + !!hlock->read]++;
3358 put_lock_stats(stats);
3362 __lock_acquired(struct lockdep_map *lock, unsigned long ip)
3364 struct task_struct *curr = current;
3365 struct held_lock *hlock, *prev_hlock;
3366 struct lock_class_stats *stats;
3368 u64 now, waittime = 0;
3371 depth = curr->lockdep_depth;
3372 if (DEBUG_LOCKS_WARN_ON(!depth))
3376 for (i = depth-1; i >= 0; i--) {
3377 hlock = curr->held_locks + i;
3379 * We must not cross into another context:
3381 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3383 if (match_held_lock(hlock, lock))
3387 print_lock_contention_bug(curr, lock, _RET_IP_);
3391 if (hlock->instance != lock)
3394 cpu = smp_processor_id();
3395 if (hlock->waittime_stamp) {
3396 now = lockstat_clock();
3397 waittime = now - hlock->waittime_stamp;
3398 hlock->holdtime_stamp = now;
3401 trace_lock_acquired(lock, ip);
3403 stats = get_lock_stats(hlock_class(hlock));
3406 lock_time_inc(&stats->read_waittime, waittime);
3408 lock_time_inc(&stats->write_waittime, waittime);
3410 if (lock->cpu != cpu)
3411 stats->bounces[bounce_acquired + !!hlock->read]++;
3412 put_lock_stats(stats);
3418 void lock_contended(struct lockdep_map *lock, unsigned long ip)
3420 unsigned long flags;
3422 if (unlikely(!lock_stat))
3425 if (unlikely(current->lockdep_recursion))
3428 raw_local_irq_save(flags);
3430 current->lockdep_recursion = 1;
3431 trace_lock_contended(lock, ip);
3432 __lock_contended(lock, ip);
3433 current->lockdep_recursion = 0;
3434 raw_local_irq_restore(flags);
3436 EXPORT_SYMBOL_GPL(lock_contended);
3438 void lock_acquired(struct lockdep_map *lock, unsigned long ip)
3440 unsigned long flags;
3442 if (unlikely(!lock_stat))
3445 if (unlikely(current->lockdep_recursion))
3448 raw_local_irq_save(flags);
3450 current->lockdep_recursion = 1;
3451 __lock_acquired(lock, ip);
3452 current->lockdep_recursion = 0;
3453 raw_local_irq_restore(flags);
3455 EXPORT_SYMBOL_GPL(lock_acquired);
3459 * Used by the testsuite, sanitize the validator state
3460 * after a simulated failure:
3463 void lockdep_reset(void)
3465 unsigned long flags;
3468 raw_local_irq_save(flags);
3469 current->curr_chain_key = 0;
3470 current->lockdep_depth = 0;
3471 current->lockdep_recursion = 0;
3472 memset(current->held_locks, 0, MAX_LOCK_DEPTH*sizeof(struct held_lock));
3473 nr_hardirq_chains = 0;
3474 nr_softirq_chains = 0;
3475 nr_process_chains = 0;
3477 for (i = 0; i < CHAINHASH_SIZE; i++)
3478 INIT_LIST_HEAD(chainhash_table + i);
3479 raw_local_irq_restore(flags);
3482 static void zap_class(struct lock_class *class)
3487 * Remove all dependencies this lock is
3490 for (i = 0; i < nr_list_entries; i++) {
3491 if (list_entries[i].class == class)
3492 list_del_rcu(&list_entries[i].entry);
3495 * Unhash the class and remove it from the all_lock_classes list:
3497 list_del_rcu(&class->hash_entry);
3498 list_del_rcu(&class->lock_entry);
3503 static inline int within(const void *addr, void *start, unsigned long size)
3505 return addr >= start && addr < start + size;
3508 void lockdep_free_key_range(void *start, unsigned long size)
3510 struct lock_class *class, *next;
3511 struct list_head *head;
3512 unsigned long flags;
3516 raw_local_irq_save(flags);
3517 locked = graph_lock();
3520 * Unhash all classes that were created by this module:
3522 for (i = 0; i < CLASSHASH_SIZE; i++) {
3523 head = classhash_table + i;
3524 if (list_empty(head))
3526 list_for_each_entry_safe(class, next, head, hash_entry) {
3527 if (within(class->key, start, size))
3529 else if (within(class->name, start, size))
3536 raw_local_irq_restore(flags);
3539 void lockdep_reset_lock(struct lockdep_map *lock)
3541 struct lock_class *class, *next;
3542 struct list_head *head;
3543 unsigned long flags;
3547 raw_local_irq_save(flags);
3550 * Remove all classes this lock might have:
3552 for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) {
3554 * If the class exists we look it up and zap it:
3556 class = look_up_lock_class(lock, j);
3561 * Debug check: in the end all mapped classes should
3564 locked = graph_lock();
3565 for (i = 0; i < CLASSHASH_SIZE; i++) {
3566 head = classhash_table + i;
3567 if (list_empty(head))
3569 list_for_each_entry_safe(class, next, head, hash_entry) {
3572 for (j = 0; j < NR_LOCKDEP_CACHING_CLASSES; j++)
3573 match |= class == lock->class_cache[j];
3575 if (unlikely(match)) {
3576 if (debug_locks_off_graph_unlock())
3586 raw_local_irq_restore(flags);
3589 void lockdep_init(void)
3594 * Some architectures have their own start_kernel()
3595 * code which calls lockdep_init(), while we also
3596 * call lockdep_init() from the start_kernel() itself,
3597 * and we want to initialize the hashes only once:
3599 if (lockdep_initialized)
3602 for (i = 0; i < CLASSHASH_SIZE; i++)
3603 INIT_LIST_HEAD(classhash_table + i);
3605 for (i = 0; i < CHAINHASH_SIZE; i++)
3606 INIT_LIST_HEAD(chainhash_table + i);
3608 lockdep_initialized = 1;
3611 void __init lockdep_info(void)
3613 printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");
3615 printk("... MAX_LOCKDEP_SUBCLASSES: %lu\n", MAX_LOCKDEP_SUBCLASSES);
3616 printk("... MAX_LOCK_DEPTH: %lu\n", MAX_LOCK_DEPTH);
3617 printk("... MAX_LOCKDEP_KEYS: %lu\n", MAX_LOCKDEP_KEYS);
3618 printk("... CLASSHASH_SIZE: %lu\n", CLASSHASH_SIZE);
3619 printk("... MAX_LOCKDEP_ENTRIES: %lu\n", MAX_LOCKDEP_ENTRIES);
3620 printk("... MAX_LOCKDEP_CHAINS: %lu\n", MAX_LOCKDEP_CHAINS);
3621 printk("... CHAINHASH_SIZE: %lu\n", CHAINHASH_SIZE);
3623 printk(" memory used by lock dependency info: %lu kB\n",
3624 (sizeof(struct lock_class) * MAX_LOCKDEP_KEYS +
3625 sizeof(struct list_head) * CLASSHASH_SIZE +
3626 sizeof(struct lock_list) * MAX_LOCKDEP_ENTRIES +
3627 sizeof(struct lock_chain) * MAX_LOCKDEP_CHAINS +
3628 sizeof(struct list_head) * CHAINHASH_SIZE
3629 #ifdef CONFIG_PROVE_LOCKING
3630 + sizeof(struct circular_queue)
3635 printk(" per task-struct memory footprint: %lu bytes\n",
3636 sizeof(struct held_lock) * MAX_LOCK_DEPTH);
3638 #ifdef CONFIG_DEBUG_LOCKDEP
3639 if (lockdep_init_error) {
3640 printk("WARNING: lockdep init error! Arch code didn't call lockdep_init() early enough?\n");
3641 printk("Call stack leading to lockdep invocation was:\n");
3642 print_stack_trace(&lockdep_init_trace, 0);
3648 print_freed_lock_bug(struct task_struct *curr, const void *mem_from,
3649 const void *mem_to, struct held_lock *hlock)
3651 if (!debug_locks_off())
3653 if (debug_locks_silent)
3656 printk("\n=========================\n");
3657 printk( "[ BUG: held lock freed! ]\n");
3658 printk( "-------------------------\n");
3659 printk("%s/%d is freeing memory %p-%p, with a lock still held there!\n",
3660 curr->comm, task_pid_nr(curr), mem_from, mem_to-1);
3662 lockdep_print_held_locks(curr);
3664 printk("\nstack backtrace:\n");
3668 static inline int not_in_range(const void* mem_from, unsigned long mem_len,
3669 const void* lock_from, unsigned long lock_len)
3671 return lock_from + lock_len <= mem_from ||
3672 mem_from + mem_len <= lock_from;
3676 * Called when kernel memory is freed (or unmapped), or if a lock
3677 * is destroyed or reinitialized - this code checks whether there is
3678 * any held lock in the memory range of <from> to <to>:
3680 void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len)
3682 struct task_struct *curr = current;
3683 struct held_lock *hlock;
3684 unsigned long flags;
3687 if (unlikely(!debug_locks))
3690 local_irq_save(flags);
3691 for (i = 0; i < curr->lockdep_depth; i++) {
3692 hlock = curr->held_locks + i;
3694 if (not_in_range(mem_from, mem_len, hlock->instance,
3695 sizeof(*hlock->instance)))
3698 print_freed_lock_bug(curr, mem_from, mem_from + mem_len, hlock);
3701 local_irq_restore(flags);
3703 EXPORT_SYMBOL_GPL(debug_check_no_locks_freed);
3705 static void print_held_locks_bug(struct task_struct *curr)
3707 if (!debug_locks_off())
3709 if (debug_locks_silent)
3712 printk("\n=====================================\n");
3713 printk( "[ BUG: lock held at task exit time! ]\n");
3714 printk( "-------------------------------------\n");
3715 printk("%s/%d is exiting with locks still held!\n",
3716 curr->comm, task_pid_nr(curr));
3717 lockdep_print_held_locks(curr);
3719 printk("\nstack backtrace:\n");
3723 void debug_check_no_locks_held(struct task_struct *task)
3725 if (unlikely(task->lockdep_depth > 0))
3726 print_held_locks_bug(task);
3729 void debug_show_all_locks(void)
3731 struct task_struct *g, *p;
3735 if (unlikely(!debug_locks)) {
3736 printk("INFO: lockdep is turned off.\n");
3739 printk("\nShowing all locks held in the system:\n");
3742 * Here we try to get the tasklist_lock as hard as possible,
3743 * if not successful after 2 seconds we ignore it (but keep
3744 * trying). This is to enable a debug printout even if a
3745 * tasklist_lock-holding task deadlocks or crashes.
3748 if (!read_trylock(&tasklist_lock)) {
3750 printk("hm, tasklist_lock locked, retrying... ");
3753 printk(" #%d", 10-count);
3757 printk(" ignoring it.\n");
3761 printk(KERN_CONT " locked it.\n");
3764 do_each_thread(g, p) {
3766 * It's not reliable to print a task's held locks
3767 * if it's not sleeping (or if it's not the current
3770 if (p->state == TASK_RUNNING && p != current)
3772 if (p->lockdep_depth)
3773 lockdep_print_held_locks(p);
3775 if (read_trylock(&tasklist_lock))
3777 } while_each_thread(g, p);
3780 printk("=============================================\n\n");
3783 read_unlock(&tasklist_lock);
3785 EXPORT_SYMBOL_GPL(debug_show_all_locks);
3788 * Careful: only use this function if you are sure that
3789 * the task cannot run in parallel!
3791 void debug_show_held_locks(struct task_struct *task)
3793 if (unlikely(!debug_locks)) {
3794 printk("INFO: lockdep is turned off.\n");
3797 lockdep_print_held_locks(task);
3799 EXPORT_SYMBOL_GPL(debug_show_held_locks);
3801 void lockdep_sys_exit(void)
3803 struct task_struct *curr = current;
3805 if (unlikely(curr->lockdep_depth)) {
3806 if (!debug_locks_off())
3808 printk("\n================================================\n");
3809 printk( "[ BUG: lock held when returning to user space! ]\n");
3810 printk( "------------------------------------------------\n");
3811 printk("%s/%d is leaving the kernel with locks still held!\n",
3812 curr->comm, curr->pid);
3813 lockdep_print_held_locks(curr);
3817 void lockdep_rcu_dereference(const char *file, const int line)
3819 struct task_struct *curr = current;
3821 #ifndef CONFIG_PROVE_RCU_REPEATEDLY
3822 if (!debug_locks_off())
3824 #endif /* #ifdef CONFIG_PROVE_RCU_REPEATEDLY */
3825 /* Note: the following can be executed concurrently, so be careful. */
3826 printk("\n===================================================\n");
3827 printk( "[ INFO: suspicious rcu_dereference_check() usage. ]\n");
3828 printk( "---------------------------------------------------\n");
3829 printk("%s:%d invoked rcu_dereference_check() without protection!\n",
3831 printk("\nother info that might help us debug this:\n\n");
3832 printk("\nrcu_scheduler_active = %d, debug_locks = %d\n", rcu_scheduler_active, debug_locks);
3833 lockdep_print_held_locks(curr);
3834 printk("\nstack backtrace:\n");
3837 EXPORT_SYMBOL_GPL(lockdep_rcu_dereference);