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);
643 * Static locks do not have their class-keys yet - for them the key
644 * is the lock object itself:
646 if (unlikely(!lock->key))
647 lock->key = (void *)lock;
650 * NOTE: the class-key must be unique. For dynamic locks, a static
651 * lock_class_key variable is passed in through the mutex_init()
652 * (or spin_lock_init()) call - which acts as the key. For static
653 * locks we use the lock object itself as the key.
655 BUILD_BUG_ON(sizeof(struct lock_class_key) >
656 sizeof(struct lockdep_map));
658 key = lock->key->subkeys + subclass;
660 hash_head = classhashentry(key);
663 * We can walk the hash lockfree, because the hash only
664 * grows, and we are careful when adding entries to the end:
666 list_for_each_entry(class, hash_head, hash_entry) {
667 if (class->key == key) {
668 WARN_ON_ONCE(class->name != lock->name);
677 * Register a lock's class in the hash-table, if the class is not present
678 * yet. Otherwise we look it up. We cache the result in the lock object
679 * itself, so actual lookup of the hash should be once per lock object.
681 static inline struct lock_class *
682 register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
684 struct lockdep_subclass_key *key;
685 struct list_head *hash_head;
686 struct lock_class *class;
689 class = look_up_lock_class(lock, subclass);
694 * Debug-check: all keys must be persistent!
696 if (!static_obj(lock->key)) {
698 printk("INFO: trying to register non-static key.\n");
699 printk("the code is fine but needs lockdep annotation.\n");
700 printk("turning off the locking correctness validator.\n");
706 key = lock->key->subkeys + subclass;
707 hash_head = classhashentry(key);
709 raw_local_irq_save(flags);
711 raw_local_irq_restore(flags);
715 * We have to do the hash-walk again, to avoid races
718 list_for_each_entry(class, hash_head, hash_entry)
719 if (class->key == key)
722 * Allocate a new key from the static array, and add it to
725 if (nr_lock_classes >= MAX_LOCKDEP_KEYS) {
726 if (!debug_locks_off_graph_unlock()) {
727 raw_local_irq_restore(flags);
730 raw_local_irq_restore(flags);
732 printk("BUG: MAX_LOCKDEP_KEYS too low!\n");
733 printk("turning off the locking correctness validator.\n");
737 class = lock_classes + nr_lock_classes++;
738 debug_atomic_inc(nr_unused_locks);
740 class->name = lock->name;
741 class->subclass = subclass;
742 INIT_LIST_HEAD(&class->lock_entry);
743 INIT_LIST_HEAD(&class->locks_before);
744 INIT_LIST_HEAD(&class->locks_after);
745 class->name_version = count_matching_names(class);
747 * We use RCU's safe list-add method to make
748 * parallel walking of the hash-list safe:
750 list_add_tail_rcu(&class->hash_entry, hash_head);
752 * Add it to the global list of classes:
754 list_add_tail_rcu(&class->lock_entry, &all_lock_classes);
756 if (verbose(class)) {
758 raw_local_irq_restore(flags);
760 printk("\nnew class %p: %s", class->key, class->name);
761 if (class->name_version > 1)
762 printk("#%d", class->name_version);
766 raw_local_irq_save(flags);
768 raw_local_irq_restore(flags);
774 raw_local_irq_restore(flags);
776 if (!subclass || force)
777 lock->class_cache = class;
779 if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))
785 #ifdef CONFIG_PROVE_LOCKING
787 * Allocate a lockdep entry. (assumes the graph_lock held, returns
788 * with NULL on failure)
790 static struct lock_list *alloc_list_entry(void)
792 if (nr_list_entries >= MAX_LOCKDEP_ENTRIES) {
793 if (!debug_locks_off_graph_unlock())
796 printk("BUG: MAX_LOCKDEP_ENTRIES too low!\n");
797 printk("turning off the locking correctness validator.\n");
801 return list_entries + nr_list_entries++;
805 * Add a new dependency to the head of the list:
807 static int add_lock_to_list(struct lock_class *class, struct lock_class *this,
808 struct list_head *head, unsigned long ip,
809 int distance, struct stack_trace *trace)
811 struct lock_list *entry;
813 * Lock not present yet - get a new dependency struct and
814 * add it to the list:
816 entry = alloc_list_entry();
821 entry->distance = distance;
822 entry->trace = *trace;
824 * Since we never remove from the dependency list, the list can
825 * be walked lockless by other CPUs, it's only allocation
826 * that must be protected by the spinlock. But this also means
827 * we must make new entries visible only once writes to the
828 * entry become visible - hence the RCU op:
830 list_add_tail_rcu(&entry->entry, head);
836 * For good efficiency of modular, we use power of 2
838 #define MAX_CIRCULAR_QUEUE_SIZE 4096UL
839 #define CQ_MASK (MAX_CIRCULAR_QUEUE_SIZE-1)
842 * The circular_queue and helpers is used to implement the
843 * breadth-first search(BFS)algorithem, by which we can build
844 * the shortest path from the next lock to be acquired to the
845 * previous held lock if there is a circular between them.
847 struct circular_queue {
848 unsigned long element[MAX_CIRCULAR_QUEUE_SIZE];
849 unsigned int front, rear;
852 static struct circular_queue lock_cq;
854 unsigned int max_bfs_queue_depth;
856 static unsigned int lockdep_dependency_gen_id;
858 static inline void __cq_init(struct circular_queue *cq)
860 cq->front = cq->rear = 0;
861 lockdep_dependency_gen_id++;
864 static inline int __cq_empty(struct circular_queue *cq)
866 return (cq->front == cq->rear);
869 static inline int __cq_full(struct circular_queue *cq)
871 return ((cq->rear + 1) & CQ_MASK) == cq->front;
874 static inline int __cq_enqueue(struct circular_queue *cq, unsigned long elem)
879 cq->element[cq->rear] = elem;
880 cq->rear = (cq->rear + 1) & CQ_MASK;
884 static inline int __cq_dequeue(struct circular_queue *cq, unsigned long *elem)
889 *elem = cq->element[cq->front];
890 cq->front = (cq->front + 1) & CQ_MASK;
894 static inline unsigned int __cq_get_elem_count(struct circular_queue *cq)
896 return (cq->rear - cq->front) & CQ_MASK;
899 static inline void mark_lock_accessed(struct lock_list *lock,
900 struct lock_list *parent)
904 nr = lock - list_entries;
905 WARN_ON(nr >= nr_list_entries);
906 lock->parent = parent;
907 lock->class->dep_gen_id = lockdep_dependency_gen_id;
910 static inline unsigned long lock_accessed(struct lock_list *lock)
914 nr = lock - list_entries;
915 WARN_ON(nr >= nr_list_entries);
916 return lock->class->dep_gen_id == lockdep_dependency_gen_id;
919 static inline struct lock_list *get_lock_parent(struct lock_list *child)
921 return child->parent;
924 static inline int get_lock_depth(struct lock_list *child)
927 struct lock_list *parent;
929 while ((parent = get_lock_parent(child))) {
936 static int __bfs(struct lock_list *source_entry,
938 int (*match)(struct lock_list *entry, void *data),
939 struct lock_list **target_entry,
942 struct lock_list *entry;
943 struct list_head *head;
944 struct circular_queue *cq = &lock_cq;
947 if (match(source_entry, data)) {
948 *target_entry = source_entry;
954 head = &source_entry->class->locks_after;
956 head = &source_entry->class->locks_before;
958 if (list_empty(head))
962 __cq_enqueue(cq, (unsigned long)source_entry);
964 while (!__cq_empty(cq)) {
965 struct lock_list *lock;
967 __cq_dequeue(cq, (unsigned long *)&lock);
975 head = &lock->class->locks_after;
977 head = &lock->class->locks_before;
979 list_for_each_entry(entry, head, entry) {
980 if (!lock_accessed(entry)) {
981 unsigned int cq_depth;
982 mark_lock_accessed(entry, lock);
983 if (match(entry, data)) {
984 *target_entry = entry;
989 if (__cq_enqueue(cq, (unsigned long)entry)) {
993 cq_depth = __cq_get_elem_count(cq);
994 if (max_bfs_queue_depth < cq_depth)
995 max_bfs_queue_depth = cq_depth;
1003 static inline int __bfs_forwards(struct lock_list *src_entry,
1005 int (*match)(struct lock_list *entry, void *data),
1006 struct lock_list **target_entry)
1008 return __bfs(src_entry, data, match, target_entry, 1);
1012 static inline int __bfs_backwards(struct lock_list *src_entry,
1014 int (*match)(struct lock_list *entry, void *data),
1015 struct lock_list **target_entry)
1017 return __bfs(src_entry, data, match, target_entry, 0);
1022 * Recursive, forwards-direction lock-dependency checking, used for
1023 * both noncyclic checking and for hardirq-unsafe/softirq-unsafe
1028 * Print a dependency chain entry (this is only done when a deadlock
1029 * has been detected):
1032 print_circular_bug_entry(struct lock_list *target, int depth)
1034 if (debug_locks_silent)
1036 printk("\n-> #%u", depth);
1037 print_lock_name(target->class);
1039 print_stack_trace(&target->trace, 6);
1045 * When a circular dependency is detected, print the
1049 print_circular_bug_header(struct lock_list *entry, unsigned int depth,
1050 struct held_lock *check_src,
1051 struct held_lock *check_tgt)
1053 struct task_struct *curr = current;
1055 if (debug_locks_silent)
1058 printk("\n=======================================================\n");
1059 printk( "[ INFO: possible circular locking dependency detected ]\n");
1060 print_kernel_version();
1061 printk( "-------------------------------------------------------\n");
1062 printk("%s/%d is trying to acquire lock:\n",
1063 curr->comm, task_pid_nr(curr));
1064 print_lock(check_src);
1065 printk("\nbut task is already holding lock:\n");
1066 print_lock(check_tgt);
1067 printk("\nwhich lock already depends on the new lock.\n\n");
1068 printk("\nthe existing dependency chain (in reverse order) is:\n");
1070 print_circular_bug_entry(entry, depth);
1075 static inline int class_equal(struct lock_list *entry, void *data)
1077 return entry->class == data;
1080 static noinline int print_circular_bug(struct lock_list *this,
1081 struct lock_list *target,
1082 struct held_lock *check_src,
1083 struct held_lock *check_tgt)
1085 struct task_struct *curr = current;
1086 struct lock_list *parent;
1089 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1092 if (!save_trace(&this->trace))
1095 depth = get_lock_depth(target);
1097 print_circular_bug_header(target, depth, check_src, check_tgt);
1099 parent = get_lock_parent(target);
1102 print_circular_bug_entry(parent, --depth);
1103 parent = get_lock_parent(parent);
1106 printk("\nother info that might help us debug this:\n\n");
1107 lockdep_print_held_locks(curr);
1109 printk("\nstack backtrace:\n");
1115 static noinline int print_bfs_bug(int ret)
1117 if (!debug_locks_off_graph_unlock())
1120 WARN(1, "lockdep bfs error:%d\n", ret);
1125 static int noop_count(struct lock_list *entry, void *data)
1127 (*(unsigned long *)data)++;
1131 unsigned long __lockdep_count_forward_deps(struct lock_list *this)
1133 unsigned long count = 0;
1134 struct lock_list *uninitialized_var(target_entry);
1136 __bfs_forwards(this, (void *)&count, noop_count, &target_entry);
1140 unsigned long lockdep_count_forward_deps(struct lock_class *class)
1142 unsigned long ret, flags;
1143 struct lock_list this;
1148 local_irq_save(flags);
1149 arch_spin_lock(&lockdep_lock);
1150 ret = __lockdep_count_forward_deps(&this);
1151 arch_spin_unlock(&lockdep_lock);
1152 local_irq_restore(flags);
1157 unsigned long __lockdep_count_backward_deps(struct lock_list *this)
1159 unsigned long count = 0;
1160 struct lock_list *uninitialized_var(target_entry);
1162 __bfs_backwards(this, (void *)&count, noop_count, &target_entry);
1167 unsigned long lockdep_count_backward_deps(struct lock_class *class)
1169 unsigned long ret, flags;
1170 struct lock_list this;
1175 local_irq_save(flags);
1176 arch_spin_lock(&lockdep_lock);
1177 ret = __lockdep_count_backward_deps(&this);
1178 arch_spin_unlock(&lockdep_lock);
1179 local_irq_restore(flags);
1185 * Prove that the dependency graph starting at <entry> can not
1186 * lead to <target>. Print an error and return 0 if it does.
1189 check_noncircular(struct lock_list *root, struct lock_class *target,
1190 struct lock_list **target_entry)
1194 debug_atomic_inc(nr_cyclic_checks);
1196 result = __bfs_forwards(root, target, class_equal, target_entry);
1201 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
1203 * Forwards and backwards subgraph searching, for the purposes of
1204 * proving that two subgraphs can be connected by a new dependency
1205 * without creating any illegal irq-safe -> irq-unsafe lock dependency.
1208 static inline int usage_match(struct lock_list *entry, void *bit)
1210 return entry->class->usage_mask & (1 << (enum lock_usage_bit)bit);
1216 * Find a node in the forwards-direction dependency sub-graph starting
1217 * at @root->class that matches @bit.
1219 * Return 0 if such a node exists in the subgraph, and put that node
1220 * into *@target_entry.
1222 * Return 1 otherwise and keep *@target_entry unchanged.
1223 * Return <0 on error.
1226 find_usage_forwards(struct lock_list *root, enum lock_usage_bit bit,
1227 struct lock_list **target_entry)
1231 debug_atomic_inc(nr_find_usage_forwards_checks);
1233 result = __bfs_forwards(root, (void *)bit, usage_match, target_entry);
1239 * Find a node in the backwards-direction dependency sub-graph starting
1240 * at @root->class that matches @bit.
1242 * Return 0 if such a node exists in the subgraph, and put that node
1243 * into *@target_entry.
1245 * Return 1 otherwise and keep *@target_entry unchanged.
1246 * Return <0 on error.
1249 find_usage_backwards(struct lock_list *root, enum lock_usage_bit bit,
1250 struct lock_list **target_entry)
1254 debug_atomic_inc(nr_find_usage_backwards_checks);
1256 result = __bfs_backwards(root, (void *)bit, usage_match, target_entry);
1261 static void print_lock_class_header(struct lock_class *class, int depth)
1265 printk("%*s->", depth, "");
1266 print_lock_name(class);
1267 printk(" ops: %lu", class->ops);
1270 for (bit = 0; bit < LOCK_USAGE_STATES; bit++) {
1271 if (class->usage_mask & (1 << bit)) {
1274 len += printk("%*s %s", depth, "", usage_str[bit]);
1275 len += printk(" at:\n");
1276 print_stack_trace(class->usage_traces + bit, len);
1279 printk("%*s }\n", depth, "");
1281 printk("%*s ... key at: ",depth,"");
1282 print_ip_sym((unsigned long)class->key);
1286 * printk the shortest lock dependencies from @start to @end in reverse order:
1289 print_shortest_lock_dependencies(struct lock_list *leaf,
1290 struct lock_list *root)
1292 struct lock_list *entry = leaf;
1295 /*compute depth from generated tree by BFS*/
1296 depth = get_lock_depth(leaf);
1299 print_lock_class_header(entry->class, depth);
1300 printk("%*s ... acquired at:\n", depth, "");
1301 print_stack_trace(&entry->trace, 2);
1304 if (depth == 0 && (entry != root)) {
1305 printk("lockdep:%s bad BFS generated tree\n", __func__);
1309 entry = get_lock_parent(entry);
1311 } while (entry && (depth >= 0));
1317 print_bad_irq_dependency(struct task_struct *curr,
1318 struct lock_list *prev_root,
1319 struct lock_list *next_root,
1320 struct lock_list *backwards_entry,
1321 struct lock_list *forwards_entry,
1322 struct held_lock *prev,
1323 struct held_lock *next,
1324 enum lock_usage_bit bit1,
1325 enum lock_usage_bit bit2,
1326 const char *irqclass)
1328 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1331 printk("\n======================================================\n");
1332 printk( "[ INFO: %s-safe -> %s-unsafe lock order detected ]\n",
1333 irqclass, irqclass);
1334 print_kernel_version();
1335 printk( "------------------------------------------------------\n");
1336 printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
1337 curr->comm, task_pid_nr(curr),
1338 curr->hardirq_context, hardirq_count() >> HARDIRQ_SHIFT,
1339 curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT,
1340 curr->hardirqs_enabled,
1341 curr->softirqs_enabled);
1344 printk("\nand this task is already holding:\n");
1346 printk("which would create a new lock dependency:\n");
1347 print_lock_name(hlock_class(prev));
1349 print_lock_name(hlock_class(next));
1352 printk("\nbut this new dependency connects a %s-irq-safe lock:\n",
1354 print_lock_name(backwards_entry->class);
1355 printk("\n... which became %s-irq-safe at:\n", irqclass);
1357 print_stack_trace(backwards_entry->class->usage_traces + bit1, 1);
1359 printk("\nto a %s-irq-unsafe lock:\n", irqclass);
1360 print_lock_name(forwards_entry->class);
1361 printk("\n... which became %s-irq-unsafe at:\n", irqclass);
1364 print_stack_trace(forwards_entry->class->usage_traces + bit2, 1);
1366 printk("\nother info that might help us debug this:\n\n");
1367 lockdep_print_held_locks(curr);
1369 printk("\nthe dependencies between %s-irq-safe lock", irqclass);
1370 printk(" and the holding lock:\n");
1371 if (!save_trace(&prev_root->trace))
1373 print_shortest_lock_dependencies(backwards_entry, prev_root);
1375 printk("\nthe dependencies between the lock to be acquired");
1376 printk(" and %s-irq-unsafe lock:\n", irqclass);
1377 if (!save_trace(&next_root->trace))
1379 print_shortest_lock_dependencies(forwards_entry, next_root);
1381 printk("\nstack backtrace:\n");
1388 check_usage(struct task_struct *curr, struct held_lock *prev,
1389 struct held_lock *next, enum lock_usage_bit bit_backwards,
1390 enum lock_usage_bit bit_forwards, const char *irqclass)
1393 struct lock_list this, that;
1394 struct lock_list *uninitialized_var(target_entry);
1395 struct lock_list *uninitialized_var(target_entry1);
1399 this.class = hlock_class(prev);
1400 ret = find_usage_backwards(&this, bit_backwards, &target_entry);
1402 return print_bfs_bug(ret);
1407 that.class = hlock_class(next);
1408 ret = find_usage_forwards(&that, bit_forwards, &target_entry1);
1410 return print_bfs_bug(ret);
1414 return print_bad_irq_dependency(curr, &this, &that,
1415 target_entry, target_entry1,
1417 bit_backwards, bit_forwards, irqclass);
1420 static const char *state_names[] = {
1421 #define LOCKDEP_STATE(__STATE) \
1422 __stringify(__STATE),
1423 #include "lockdep_states.h"
1424 #undef LOCKDEP_STATE
1427 static const char *state_rnames[] = {
1428 #define LOCKDEP_STATE(__STATE) \
1429 __stringify(__STATE)"-READ",
1430 #include "lockdep_states.h"
1431 #undef LOCKDEP_STATE
1434 static inline const char *state_name(enum lock_usage_bit bit)
1436 return (bit & 1) ? state_rnames[bit >> 2] : state_names[bit >> 2];
1439 static int exclusive_bit(int new_bit)
1447 * bit 0 - write/read
1448 * bit 1 - used_in/enabled
1452 int state = new_bit & ~3;
1453 int dir = new_bit & 2;
1456 * keep state, bit flip the direction and strip read.
1458 return state | (dir ^ 2);
1461 static int check_irq_usage(struct task_struct *curr, struct held_lock *prev,
1462 struct held_lock *next, enum lock_usage_bit bit)
1465 * Prove that the new dependency does not connect a hardirq-safe
1466 * lock with a hardirq-unsafe lock - to achieve this we search
1467 * the backwards-subgraph starting at <prev>, and the
1468 * forwards-subgraph starting at <next>:
1470 if (!check_usage(curr, prev, next, bit,
1471 exclusive_bit(bit), state_name(bit)))
1477 * Prove that the new dependency does not connect a hardirq-safe-read
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)))
1490 check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
1491 struct held_lock *next)
1493 #define LOCKDEP_STATE(__STATE) \
1494 if (!check_irq_usage(curr, prev, next, LOCK_USED_IN_##__STATE)) \
1496 #include "lockdep_states.h"
1497 #undef LOCKDEP_STATE
1502 static void inc_chains(void)
1504 if (current->hardirq_context)
1505 nr_hardirq_chains++;
1507 if (current->softirq_context)
1508 nr_softirq_chains++;
1510 nr_process_chains++;
1517 check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
1518 struct held_lock *next)
1523 static inline void inc_chains(void)
1525 nr_process_chains++;
1531 print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
1532 struct held_lock *next)
1534 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1537 printk("\n=============================================\n");
1538 printk( "[ INFO: possible recursive locking detected ]\n");
1539 print_kernel_version();
1540 printk( "---------------------------------------------\n");
1541 printk("%s/%d is trying to acquire lock:\n",
1542 curr->comm, task_pid_nr(curr));
1544 printk("\nbut task is already holding lock:\n");
1547 printk("\nother info that might help us debug this:\n");
1548 lockdep_print_held_locks(curr);
1550 printk("\nstack backtrace:\n");
1557 * Check whether we are holding such a class already.
1559 * (Note that this has to be done separately, because the graph cannot
1560 * detect such classes of deadlocks.)
1562 * Returns: 0 on deadlock detected, 1 on OK, 2 on recursive read
1565 check_deadlock(struct task_struct *curr, struct held_lock *next,
1566 struct lockdep_map *next_instance, int read)
1568 struct held_lock *prev;
1569 struct held_lock *nest = NULL;
1572 for (i = 0; i < curr->lockdep_depth; i++) {
1573 prev = curr->held_locks + i;
1575 if (prev->instance == next->nest_lock)
1578 if (hlock_class(prev) != hlock_class(next))
1582 * Allow read-after-read recursion of the same
1583 * lock class (i.e. read_lock(lock)+read_lock(lock)):
1585 if ((read == 2) && prev->read)
1589 * We're holding the nest_lock, which serializes this lock's
1590 * nesting behaviour.
1595 return print_deadlock_bug(curr, prev, next);
1601 * There was a chain-cache miss, and we are about to add a new dependency
1602 * to a previous lock. We recursively validate the following rules:
1604 * - would the adding of the <prev> -> <next> dependency create a
1605 * circular dependency in the graph? [== circular deadlock]
1607 * - does the new prev->next dependency connect any hardirq-safe lock
1608 * (in the full backwards-subgraph starting at <prev>) with any
1609 * hardirq-unsafe lock (in the full forwards-subgraph starting at
1610 * <next>)? [== illegal lock inversion with hardirq contexts]
1612 * - does the new prev->next dependency connect any softirq-safe lock
1613 * (in the full backwards-subgraph starting at <prev>) with any
1614 * softirq-unsafe lock (in the full forwards-subgraph starting at
1615 * <next>)? [== illegal lock inversion with softirq contexts]
1617 * any of these scenarios could lead to a deadlock.
1619 * Then if all the validations pass, we add the forwards and backwards
1623 check_prev_add(struct task_struct *curr, struct held_lock *prev,
1624 struct held_lock *next, int distance, int trylock_loop)
1626 struct lock_list *entry;
1628 struct lock_list this;
1629 struct lock_list *uninitialized_var(target_entry);
1631 * Static variable, serialized by the graph_lock().
1633 * We use this static variable to save the stack trace in case
1634 * we call into this function multiple times due to encountering
1635 * trylocks in the held lock stack.
1637 static struct stack_trace trace;
1640 * Prove that the new <prev> -> <next> dependency would not
1641 * create a circular dependency in the graph. (We do this by
1642 * forward-recursing into the graph starting at <next>, and
1643 * checking whether we can reach <prev>.)
1645 * We are using global variables to control the recursion, to
1646 * keep the stackframe size of the recursive functions low:
1648 this.class = hlock_class(next);
1650 ret = check_noncircular(&this, hlock_class(prev), &target_entry);
1652 return print_circular_bug(&this, target_entry, next, prev);
1653 else if (unlikely(ret < 0))
1654 return print_bfs_bug(ret);
1656 if (!check_prev_add_irq(curr, prev, next))
1660 * For recursive read-locks we do all the dependency checks,
1661 * but we dont store read-triggered dependencies (only
1662 * write-triggered dependencies). This ensures that only the
1663 * write-side dependencies matter, and that if for example a
1664 * write-lock never takes any other locks, then the reads are
1665 * equivalent to a NOP.
1667 if (next->read == 2 || prev->read == 2)
1670 * Is the <prev> -> <next> dependency already present?
1672 * (this may occur even though this is a new chain: consider
1673 * e.g. the L1 -> L2 -> L3 -> L4 and the L5 -> L1 -> L2 -> L3
1674 * chains - the second one will be new, but L1 already has
1675 * L2 added to its dependency list, due to the first chain.)
1677 list_for_each_entry(entry, &hlock_class(prev)->locks_after, entry) {
1678 if (entry->class == hlock_class(next)) {
1680 entry->distance = 1;
1685 if (!trylock_loop && !save_trace(&trace))
1689 * Ok, all validations passed, add the new lock
1690 * to the previous lock's dependency list:
1692 ret = add_lock_to_list(hlock_class(prev), hlock_class(next),
1693 &hlock_class(prev)->locks_after,
1694 next->acquire_ip, distance, &trace);
1699 ret = add_lock_to_list(hlock_class(next), hlock_class(prev),
1700 &hlock_class(next)->locks_before,
1701 next->acquire_ip, distance, &trace);
1706 * Debugging printouts:
1708 if (verbose(hlock_class(prev)) || verbose(hlock_class(next))) {
1710 printk("\n new dependency: ");
1711 print_lock_name(hlock_class(prev));
1713 print_lock_name(hlock_class(next));
1716 return graph_lock();
1722 * Add the dependency to all directly-previous locks that are 'relevant'.
1723 * The ones that are relevant are (in increasing distance from curr):
1724 * all consecutive trylock entries and the final non-trylock entry - or
1725 * the end of this context's lock-chain - whichever comes first.
1728 check_prevs_add(struct task_struct *curr, struct held_lock *next)
1730 int depth = curr->lockdep_depth;
1731 int trylock_loop = 0;
1732 struct held_lock *hlock;
1737 * Depth must not be zero for a non-head lock:
1742 * At least two relevant locks must exist for this
1745 if (curr->held_locks[depth].irq_context !=
1746 curr->held_locks[depth-1].irq_context)
1750 int distance = curr->lockdep_depth - depth + 1;
1751 hlock = curr->held_locks + depth-1;
1753 * Only non-recursive-read entries get new dependencies
1756 if (hlock->read != 2) {
1757 if (!check_prev_add(curr, hlock, next,
1758 distance, trylock_loop))
1761 * Stop after the first non-trylock entry,
1762 * as non-trylock entries have added their
1763 * own direct dependencies already, so this
1764 * lock is connected to them indirectly:
1766 if (!hlock->trylock)
1771 * End of lock-stack?
1776 * Stop the search if we cross into another context:
1778 if (curr->held_locks[depth].irq_context !=
1779 curr->held_locks[depth-1].irq_context)
1785 if (!debug_locks_off_graph_unlock())
1793 unsigned long nr_lock_chains;
1794 struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
1795 int nr_chain_hlocks;
1796 static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
1798 struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
1800 return lock_classes + chain_hlocks[chain->base + i];
1804 * Look up a dependency chain. If the key is not present yet then
1805 * add it and return 1 - in this case the new dependency chain is
1806 * validated. If the key is already hashed, return 0.
1807 * (On return with 1 graph_lock is held.)
1809 static inline int lookup_chain_cache(struct task_struct *curr,
1810 struct held_lock *hlock,
1813 struct lock_class *class = hlock_class(hlock);
1814 struct list_head *hash_head = chainhashentry(chain_key);
1815 struct lock_chain *chain;
1816 struct held_lock *hlock_curr, *hlock_next;
1819 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
1822 * We can walk it lock-free, because entries only get added
1825 list_for_each_entry(chain, hash_head, entry) {
1826 if (chain->chain_key == chain_key) {
1828 debug_atomic_inc(chain_lookup_hits);
1829 if (very_verbose(class))
1830 printk("\nhash chain already cached, key: "
1831 "%016Lx tail class: [%p] %s\n",
1832 (unsigned long long)chain_key,
1833 class->key, class->name);
1837 if (very_verbose(class))
1838 printk("\nnew hash chain, key: %016Lx tail class: [%p] %s\n",
1839 (unsigned long long)chain_key, class->key, class->name);
1841 * Allocate a new chain entry from the static array, and add
1847 * We have to walk the chain again locked - to avoid duplicates:
1849 list_for_each_entry(chain, hash_head, entry) {
1850 if (chain->chain_key == chain_key) {
1855 if (unlikely(nr_lock_chains >= MAX_LOCKDEP_CHAINS)) {
1856 if (!debug_locks_off_graph_unlock())
1859 printk("BUG: MAX_LOCKDEP_CHAINS too low!\n");
1860 printk("turning off the locking correctness validator.\n");
1864 chain = lock_chains + nr_lock_chains++;
1865 chain->chain_key = chain_key;
1866 chain->irq_context = hlock->irq_context;
1867 /* Find the first held_lock of current chain */
1869 for (i = curr->lockdep_depth - 1; i >= 0; i--) {
1870 hlock_curr = curr->held_locks + i;
1871 if (hlock_curr->irq_context != hlock_next->irq_context)
1876 chain->depth = curr->lockdep_depth + 1 - i;
1877 cn = nr_chain_hlocks;
1878 while (cn + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS) {
1879 n = cmpxchg(&nr_chain_hlocks, cn, cn + chain->depth);
1884 if (likely(cn + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) {
1886 for (j = 0; j < chain->depth - 1; j++, i++) {
1887 int lock_id = curr->held_locks[i].class_idx - 1;
1888 chain_hlocks[chain->base + j] = lock_id;
1890 chain_hlocks[chain->base + j] = class - lock_classes;
1892 list_add_tail_rcu(&chain->entry, hash_head);
1893 debug_atomic_inc(chain_lookup_misses);
1899 static int validate_chain(struct task_struct *curr, struct lockdep_map *lock,
1900 struct held_lock *hlock, int chain_head, u64 chain_key)
1903 * Trylock needs to maintain the stack of held locks, but it
1904 * does not add new dependencies, because trylock can be done
1907 * We look up the chain_key and do the O(N^2) check and update of
1908 * the dependencies only if this is a new dependency chain.
1909 * (If lookup_chain_cache() returns with 1 it acquires
1910 * graph_lock for us)
1912 if (!hlock->trylock && (hlock->check == 2) &&
1913 lookup_chain_cache(curr, hlock, chain_key)) {
1915 * Check whether last held lock:
1917 * - is irq-safe, if this lock is irq-unsafe
1918 * - is softirq-safe, if this lock is hardirq-unsafe
1920 * And check whether the new lock's dependency graph
1921 * could lead back to the previous lock.
1923 * any of these scenarios could lead to a deadlock. If
1926 int ret = check_deadlock(curr, hlock, lock, hlock->read);
1931 * Mark recursive read, as we jump over it when
1932 * building dependencies (just like we jump over
1938 * Add dependency only if this lock is not the head
1939 * of the chain, and if it's not a secondary read-lock:
1941 if (!chain_head && ret != 2)
1942 if (!check_prevs_add(curr, hlock))
1946 /* after lookup_chain_cache(): */
1947 if (unlikely(!debug_locks))
1953 static inline int validate_chain(struct task_struct *curr,
1954 struct lockdep_map *lock, struct held_lock *hlock,
1955 int chain_head, u64 chain_key)
1962 * We are building curr_chain_key incrementally, so double-check
1963 * it from scratch, to make sure that it's done correctly:
1965 static void check_chain_key(struct task_struct *curr)
1967 #ifdef CONFIG_DEBUG_LOCKDEP
1968 struct held_lock *hlock, *prev_hlock = NULL;
1972 for (i = 0; i < curr->lockdep_depth; i++) {
1973 hlock = curr->held_locks + i;
1974 if (chain_key != hlock->prev_chain_key) {
1976 WARN(1, "hm#1, depth: %u [%u], %016Lx != %016Lx\n",
1977 curr->lockdep_depth, i,
1978 (unsigned long long)chain_key,
1979 (unsigned long long)hlock->prev_chain_key);
1982 id = hlock->class_idx - 1;
1983 if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
1986 if (prev_hlock && (prev_hlock->irq_context !=
1987 hlock->irq_context))
1989 chain_key = iterate_chain_key(chain_key, id);
1992 if (chain_key != curr->curr_chain_key) {
1994 WARN(1, "hm#2, depth: %u [%u], %016Lx != %016Lx\n",
1995 curr->lockdep_depth, i,
1996 (unsigned long long)chain_key,
1997 (unsigned long long)curr->curr_chain_key);
2003 print_usage_bug(struct task_struct *curr, struct held_lock *this,
2004 enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
2006 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2009 printk("\n=================================\n");
2010 printk( "[ INFO: inconsistent lock state ]\n");
2011 print_kernel_version();
2012 printk( "---------------------------------\n");
2014 printk("inconsistent {%s} -> {%s} usage.\n",
2015 usage_str[prev_bit], usage_str[new_bit]);
2017 printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] takes:\n",
2018 curr->comm, task_pid_nr(curr),
2019 trace_hardirq_context(curr), hardirq_count() >> HARDIRQ_SHIFT,
2020 trace_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT,
2021 trace_hardirqs_enabled(curr),
2022 trace_softirqs_enabled(curr));
2025 printk("{%s} state was registered at:\n", usage_str[prev_bit]);
2026 print_stack_trace(hlock_class(this)->usage_traces + prev_bit, 1);
2028 print_irqtrace_events(curr);
2029 printk("\nother info that might help us debug this:\n");
2030 lockdep_print_held_locks(curr);
2032 printk("\nstack backtrace:\n");
2039 * Print out an error if an invalid bit is set:
2042 valid_state(struct task_struct *curr, struct held_lock *this,
2043 enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit)
2045 if (unlikely(hlock_class(this)->usage_mask & (1 << bad_bit)))
2046 return print_usage_bug(curr, this, bad_bit, new_bit);
2050 static int mark_lock(struct task_struct *curr, struct held_lock *this,
2051 enum lock_usage_bit new_bit);
2053 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
2056 * print irq inversion bug:
2059 print_irq_inversion_bug(struct task_struct *curr,
2060 struct lock_list *root, struct lock_list *other,
2061 struct held_lock *this, int forwards,
2062 const char *irqclass)
2064 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2067 printk("\n=========================================================\n");
2068 printk( "[ INFO: possible irq lock inversion dependency detected ]\n");
2069 print_kernel_version();
2070 printk( "---------------------------------------------------------\n");
2071 printk("%s/%d just changed the state of lock:\n",
2072 curr->comm, task_pid_nr(curr));
2075 printk("but this lock took another, %s-unsafe lock in the past:\n", irqclass);
2077 printk("but this lock was taken by another, %s-safe lock in the past:\n", irqclass);
2078 print_lock_name(other->class);
2079 printk("\n\nand interrupts could create inverse lock ordering between them.\n\n");
2081 printk("\nother info that might help us debug this:\n");
2082 lockdep_print_held_locks(curr);
2084 printk("\nthe shortest dependencies between 2nd lock and 1st lock:\n");
2085 if (!save_trace(&root->trace))
2087 print_shortest_lock_dependencies(other, root);
2089 printk("\nstack backtrace:\n");
2096 * Prove that in the forwards-direction subgraph starting at <this>
2097 * there is no lock matching <mask>:
2100 check_usage_forwards(struct task_struct *curr, struct held_lock *this,
2101 enum lock_usage_bit bit, const char *irqclass)
2104 struct lock_list root;
2105 struct lock_list *uninitialized_var(target_entry);
2108 root.class = hlock_class(this);
2109 ret = find_usage_forwards(&root, bit, &target_entry);
2111 return print_bfs_bug(ret);
2115 return print_irq_inversion_bug(curr, &root, target_entry,
2120 * Prove that in the backwards-direction subgraph starting at <this>
2121 * there is no lock matching <mask>:
2124 check_usage_backwards(struct task_struct *curr, struct held_lock *this,
2125 enum lock_usage_bit bit, const char *irqclass)
2128 struct lock_list root;
2129 struct lock_list *uninitialized_var(target_entry);
2132 root.class = hlock_class(this);
2133 ret = find_usage_backwards(&root, bit, &target_entry);
2135 return print_bfs_bug(ret);
2139 return print_irq_inversion_bug(curr, &root, target_entry,
2143 void print_irqtrace_events(struct task_struct *curr)
2145 printk("irq event stamp: %u\n", curr->irq_events);
2146 printk("hardirqs last enabled at (%u): ", curr->hardirq_enable_event);
2147 print_ip_sym(curr->hardirq_enable_ip);
2148 printk("hardirqs last disabled at (%u): ", curr->hardirq_disable_event);
2149 print_ip_sym(curr->hardirq_disable_ip);
2150 printk("softirqs last enabled at (%u): ", curr->softirq_enable_event);
2151 print_ip_sym(curr->softirq_enable_ip);
2152 printk("softirqs last disabled at (%u): ", curr->softirq_disable_event);
2153 print_ip_sym(curr->softirq_disable_ip);
2156 static int HARDIRQ_verbose(struct lock_class *class)
2159 return class_filter(class);
2164 static int SOFTIRQ_verbose(struct lock_class *class)
2167 return class_filter(class);
2172 static int RECLAIM_FS_verbose(struct lock_class *class)
2175 return class_filter(class);
2180 #define STRICT_READ_CHECKS 1
2182 static int (*state_verbose_f[])(struct lock_class *class) = {
2183 #define LOCKDEP_STATE(__STATE) \
2185 #include "lockdep_states.h"
2186 #undef LOCKDEP_STATE
2189 static inline int state_verbose(enum lock_usage_bit bit,
2190 struct lock_class *class)
2192 return state_verbose_f[bit >> 2](class);
2195 typedef int (*check_usage_f)(struct task_struct *, struct held_lock *,
2196 enum lock_usage_bit bit, const char *name);
2199 mark_lock_irq(struct task_struct *curr, struct held_lock *this,
2200 enum lock_usage_bit new_bit)
2202 int excl_bit = exclusive_bit(new_bit);
2203 int read = new_bit & 1;
2204 int dir = new_bit & 2;
2207 * mark USED_IN has to look forwards -- to ensure no dependency
2208 * has ENABLED state, which would allow recursion deadlocks.
2210 * mark ENABLED has to look backwards -- to ensure no dependee
2211 * has USED_IN state, which, again, would allow recursion deadlocks.
2213 check_usage_f usage = dir ?
2214 check_usage_backwards : check_usage_forwards;
2217 * Validate that this particular lock does not have conflicting
2220 if (!valid_state(curr, this, new_bit, excl_bit))
2224 * Validate that the lock dependencies don't have conflicting usage
2227 if ((!read || !dir || STRICT_READ_CHECKS) &&
2228 !usage(curr, this, excl_bit, state_name(new_bit & ~1)))
2232 * Check for read in write conflicts
2235 if (!valid_state(curr, this, new_bit, excl_bit + 1))
2238 if (STRICT_READ_CHECKS &&
2239 !usage(curr, this, excl_bit + 1,
2240 state_name(new_bit + 1)))
2244 if (state_verbose(new_bit, hlock_class(this)))
2251 #define LOCKDEP_STATE(__STATE) __STATE,
2252 #include "lockdep_states.h"
2253 #undef LOCKDEP_STATE
2257 * Mark all held locks with a usage bit:
2260 mark_held_locks(struct task_struct *curr, enum mark_type mark)
2262 enum lock_usage_bit usage_bit;
2263 struct held_lock *hlock;
2266 for (i = 0; i < curr->lockdep_depth; i++) {
2267 hlock = curr->held_locks + i;
2269 usage_bit = 2 + (mark << 2); /* ENABLED */
2271 usage_bit += 1; /* READ */
2273 BUG_ON(usage_bit >= LOCK_USAGE_STATES);
2275 if (!mark_lock(curr, hlock, usage_bit))
2283 * Debugging helper: via this flag we know that we are in
2284 * 'early bootup code', and will warn about any invalid irqs-on event:
2286 static int early_boot_irqs_enabled;
2288 void early_boot_irqs_off(void)
2290 early_boot_irqs_enabled = 0;
2293 void early_boot_irqs_on(void)
2295 early_boot_irqs_enabled = 1;
2299 * Hardirqs will be enabled:
2301 void trace_hardirqs_on_caller(unsigned long ip)
2303 struct task_struct *curr = current;
2305 time_hardirqs_on(CALLER_ADDR0, ip);
2307 if (unlikely(!debug_locks || current->lockdep_recursion))
2310 if (DEBUG_LOCKS_WARN_ON(unlikely(!early_boot_irqs_enabled)))
2313 if (unlikely(curr->hardirqs_enabled)) {
2315 * Neither irq nor preemption are disabled here
2316 * so this is racy by nature but loosing one hit
2317 * in a stat is not a big deal.
2319 __debug_atomic_inc(redundant_hardirqs_on);
2322 /* we'll do an OFF -> ON transition: */
2323 curr->hardirqs_enabled = 1;
2325 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2327 if (DEBUG_LOCKS_WARN_ON(current->hardirq_context))
2330 * We are going to turn hardirqs on, so set the
2331 * usage bit for all held locks:
2333 if (!mark_held_locks(curr, HARDIRQ))
2336 * If we have softirqs enabled, then set the usage
2337 * bit for all held locks. (disabled hardirqs prevented
2338 * this bit from being set before)
2340 if (curr->softirqs_enabled)
2341 if (!mark_held_locks(curr, SOFTIRQ))
2344 curr->hardirq_enable_ip = ip;
2345 curr->hardirq_enable_event = ++curr->irq_events;
2346 debug_atomic_inc(hardirqs_on_events);
2348 EXPORT_SYMBOL(trace_hardirqs_on_caller);
2350 void trace_hardirqs_on(void)
2352 trace_hardirqs_on_caller(CALLER_ADDR0);
2354 EXPORT_SYMBOL(trace_hardirqs_on);
2357 * Hardirqs were disabled:
2359 void trace_hardirqs_off_caller(unsigned long ip)
2361 struct task_struct *curr = current;
2363 time_hardirqs_off(CALLER_ADDR0, ip);
2365 if (unlikely(!debug_locks || current->lockdep_recursion))
2368 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2371 if (curr->hardirqs_enabled) {
2373 * We have done an ON -> OFF transition:
2375 curr->hardirqs_enabled = 0;
2376 curr->hardirq_disable_ip = ip;
2377 curr->hardirq_disable_event = ++curr->irq_events;
2378 debug_atomic_inc(hardirqs_off_events);
2380 debug_atomic_inc(redundant_hardirqs_off);
2382 EXPORT_SYMBOL(trace_hardirqs_off_caller);
2384 void trace_hardirqs_off(void)
2386 trace_hardirqs_off_caller(CALLER_ADDR0);
2388 EXPORT_SYMBOL(trace_hardirqs_off);
2391 * Softirqs will be enabled:
2393 void trace_softirqs_on(unsigned long ip)
2395 struct task_struct *curr = current;
2397 if (unlikely(!debug_locks))
2400 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2403 if (curr->softirqs_enabled) {
2404 debug_atomic_inc(redundant_softirqs_on);
2409 * We'll do an OFF -> ON transition:
2411 curr->softirqs_enabled = 1;
2412 curr->softirq_enable_ip = ip;
2413 curr->softirq_enable_event = ++curr->irq_events;
2414 debug_atomic_inc(softirqs_on_events);
2416 * We are going to turn softirqs on, so set the
2417 * usage bit for all held locks, if hardirqs are
2420 if (curr->hardirqs_enabled)
2421 mark_held_locks(curr, SOFTIRQ);
2425 * Softirqs were disabled:
2427 void trace_softirqs_off(unsigned long ip)
2429 struct task_struct *curr = current;
2431 if (unlikely(!debug_locks))
2434 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2437 if (curr->softirqs_enabled) {
2439 * We have done an ON -> OFF transition:
2441 curr->softirqs_enabled = 0;
2442 curr->softirq_disable_ip = ip;
2443 curr->softirq_disable_event = ++curr->irq_events;
2444 debug_atomic_inc(softirqs_off_events);
2445 DEBUG_LOCKS_WARN_ON(!softirq_count());
2447 debug_atomic_inc(redundant_softirqs_off);
2450 static void __lockdep_trace_alloc(gfp_t gfp_mask, unsigned long flags)
2452 struct task_struct *curr = current;
2454 if (unlikely(!debug_locks))
2457 /* no reclaim without waiting on it */
2458 if (!(gfp_mask & __GFP_WAIT))
2461 /* this guy won't enter reclaim */
2462 if ((curr->flags & PF_MEMALLOC) && !(gfp_mask & __GFP_NOMEMALLOC))
2465 /* We're only interested __GFP_FS allocations for now */
2466 if (!(gfp_mask & __GFP_FS))
2469 if (DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags)))
2472 mark_held_locks(curr, RECLAIM_FS);
2475 static void check_flags(unsigned long flags);
2477 void lockdep_trace_alloc(gfp_t gfp_mask)
2479 unsigned long flags;
2481 if (unlikely(current->lockdep_recursion))
2484 raw_local_irq_save(flags);
2486 current->lockdep_recursion = 1;
2487 __lockdep_trace_alloc(gfp_mask, flags);
2488 current->lockdep_recursion = 0;
2489 raw_local_irq_restore(flags);
2492 static int mark_irqflags(struct task_struct *curr, struct held_lock *hlock)
2495 * If non-trylock use in a hardirq or softirq context, then
2496 * mark the lock as used in these contexts:
2498 if (!hlock->trylock) {
2500 if (curr->hardirq_context)
2501 if (!mark_lock(curr, hlock,
2502 LOCK_USED_IN_HARDIRQ_READ))
2504 if (curr->softirq_context)
2505 if (!mark_lock(curr, hlock,
2506 LOCK_USED_IN_SOFTIRQ_READ))
2509 if (curr->hardirq_context)
2510 if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ))
2512 if (curr->softirq_context)
2513 if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ))
2517 if (!hlock->hardirqs_off) {
2519 if (!mark_lock(curr, hlock,
2520 LOCK_ENABLED_HARDIRQ_READ))
2522 if (curr->softirqs_enabled)
2523 if (!mark_lock(curr, hlock,
2524 LOCK_ENABLED_SOFTIRQ_READ))
2527 if (!mark_lock(curr, hlock,
2528 LOCK_ENABLED_HARDIRQ))
2530 if (curr->softirqs_enabled)
2531 if (!mark_lock(curr, hlock,
2532 LOCK_ENABLED_SOFTIRQ))
2538 * We reuse the irq context infrastructure more broadly as a general
2539 * context checking code. This tests GFP_FS recursion (a lock taken
2540 * during reclaim for a GFP_FS allocation is held over a GFP_FS
2543 if (!hlock->trylock && (curr->lockdep_reclaim_gfp & __GFP_FS)) {
2545 if (!mark_lock(curr, hlock, LOCK_USED_IN_RECLAIM_FS_READ))
2548 if (!mark_lock(curr, hlock, LOCK_USED_IN_RECLAIM_FS))
2556 static int separate_irq_context(struct task_struct *curr,
2557 struct held_lock *hlock)
2559 unsigned int depth = curr->lockdep_depth;
2562 * Keep track of points where we cross into an interrupt context:
2564 hlock->irq_context = 2*(curr->hardirq_context ? 1 : 0) +
2565 curr->softirq_context;
2567 struct held_lock *prev_hlock;
2569 prev_hlock = curr->held_locks + depth-1;
2571 * If we cross into another context, reset the
2572 * hash key (this also prevents the checking and the
2573 * adding of the dependency to 'prev'):
2575 if (prev_hlock->irq_context != hlock->irq_context)
2584 int mark_lock_irq(struct task_struct *curr, struct held_lock *this,
2585 enum lock_usage_bit new_bit)
2591 static inline int mark_irqflags(struct task_struct *curr,
2592 struct held_lock *hlock)
2597 static inline int separate_irq_context(struct task_struct *curr,
2598 struct held_lock *hlock)
2603 void lockdep_trace_alloc(gfp_t gfp_mask)
2610 * Mark a lock with a usage bit, and validate the state transition:
2612 static int mark_lock(struct task_struct *curr, struct held_lock *this,
2613 enum lock_usage_bit new_bit)
2615 unsigned int new_mask = 1 << new_bit, ret = 1;
2618 * If already set then do not dirty the cacheline,
2619 * nor do any checks:
2621 if (likely(hlock_class(this)->usage_mask & new_mask))
2627 * Make sure we didnt race:
2629 if (unlikely(hlock_class(this)->usage_mask & new_mask)) {
2634 hlock_class(this)->usage_mask |= new_mask;
2636 if (!save_trace(hlock_class(this)->usage_traces + new_bit))
2640 #define LOCKDEP_STATE(__STATE) \
2641 case LOCK_USED_IN_##__STATE: \
2642 case LOCK_USED_IN_##__STATE##_READ: \
2643 case LOCK_ENABLED_##__STATE: \
2644 case LOCK_ENABLED_##__STATE##_READ:
2645 #include "lockdep_states.h"
2646 #undef LOCKDEP_STATE
2647 ret = mark_lock_irq(curr, this, new_bit);
2652 debug_atomic_dec(nr_unused_locks);
2655 if (!debug_locks_off_graph_unlock())
2664 * We must printk outside of the graph_lock:
2667 printk("\nmarked lock as {%s}:\n", usage_str[new_bit]);
2669 print_irqtrace_events(curr);
2677 * Initialize a lock instance's lock-class mapping info:
2679 void lockdep_init_map(struct lockdep_map *lock, const char *name,
2680 struct lock_class_key *key, int subclass)
2682 lock->class_cache = NULL;
2683 #ifdef CONFIG_LOCK_STAT
2684 lock->cpu = raw_smp_processor_id();
2687 if (DEBUG_LOCKS_WARN_ON(!name)) {
2688 lock->name = "NULL";
2694 if (DEBUG_LOCKS_WARN_ON(!key))
2697 * Sanity check, the lock-class key must be persistent:
2699 if (!static_obj(key)) {
2700 printk("BUG: key %p not in .data!\n", key);
2701 DEBUG_LOCKS_WARN_ON(1);
2706 if (unlikely(!debug_locks))
2710 register_lock_class(lock, subclass, 1);
2712 EXPORT_SYMBOL_GPL(lockdep_init_map);
2714 struct lock_class_key __lockdep_no_validate__;
2717 * This gets called for every mutex_lock*()/spin_lock*() operation.
2718 * We maintain the dependency maps and validate the locking attempt:
2720 static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
2721 int trylock, int read, int check, int hardirqs_off,
2722 struct lockdep_map *nest_lock, unsigned long ip,
2725 struct task_struct *curr = current;
2726 struct lock_class *class = NULL;
2727 struct held_lock *hlock;
2728 unsigned int depth, id;
2736 if (unlikely(!debug_locks))
2739 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2742 if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
2744 printk("BUG: MAX_LOCKDEP_SUBCLASSES too low!\n");
2745 printk("turning off the locking correctness validator.\n");
2750 if (lock->key == &__lockdep_no_validate__)
2754 class = lock->class_cache;
2756 * Not cached yet or subclass?
2758 if (unlikely(!class)) {
2759 class = register_lock_class(lock, subclass, 0);
2763 atomic_inc((atomic_t *)&class->ops);
2764 if (very_verbose(class)) {
2765 printk("\nacquire class [%p] %s", class->key, class->name);
2766 if (class->name_version > 1)
2767 printk("#%d", class->name_version);
2773 * Add the lock to the list of currently held locks.
2774 * (we dont increase the depth just yet, up until the
2775 * dependency checks are done)
2777 depth = curr->lockdep_depth;
2778 if (DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH))
2781 class_idx = class - lock_classes + 1;
2784 hlock = curr->held_locks + depth - 1;
2785 if (hlock->class_idx == class_idx && nest_lock) {
2786 if (hlock->references)
2787 hlock->references++;
2789 hlock->references = 2;
2795 hlock = curr->held_locks + depth;
2796 if (DEBUG_LOCKS_WARN_ON(!class))
2798 hlock->class_idx = class_idx;
2799 hlock->acquire_ip = ip;
2800 hlock->instance = lock;
2801 hlock->nest_lock = nest_lock;
2802 hlock->trylock = trylock;
2804 hlock->check = check;
2805 hlock->hardirqs_off = !!hardirqs_off;
2806 hlock->references = references;
2807 #ifdef CONFIG_LOCK_STAT
2808 hlock->waittime_stamp = 0;
2809 hlock->holdtime_stamp = lockstat_clock();
2812 if (check == 2 && !mark_irqflags(curr, hlock))
2815 /* mark it as used: */
2816 if (!mark_lock(curr, hlock, LOCK_USED))
2820 * Calculate the chain hash: it's the combined hash of all the
2821 * lock keys along the dependency chain. We save the hash value
2822 * at every step so that we can get the current hash easily
2823 * after unlock. The chain hash is then used to cache dependency
2826 * The 'key ID' is what is the most compact key value to drive
2827 * the hash, not class->key.
2829 id = class - lock_classes;
2830 if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
2833 chain_key = curr->curr_chain_key;
2835 if (DEBUG_LOCKS_WARN_ON(chain_key != 0))
2840 hlock->prev_chain_key = chain_key;
2841 if (separate_irq_context(curr, hlock)) {
2845 chain_key = iterate_chain_key(chain_key, id);
2847 if (!validate_chain(curr, lock, hlock, chain_head, chain_key))
2850 curr->curr_chain_key = chain_key;
2851 curr->lockdep_depth++;
2852 check_chain_key(curr);
2853 #ifdef CONFIG_DEBUG_LOCKDEP
2854 if (unlikely(!debug_locks))
2857 if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
2859 printk("BUG: MAX_LOCK_DEPTH too low!\n");
2860 printk("turning off the locking correctness validator.\n");
2865 if (unlikely(curr->lockdep_depth > max_lockdep_depth))
2866 max_lockdep_depth = curr->lockdep_depth;
2872 print_unlock_inbalance_bug(struct task_struct *curr, struct lockdep_map *lock,
2875 if (!debug_locks_off())
2877 if (debug_locks_silent)
2880 printk("\n=====================================\n");
2881 printk( "[ BUG: bad unlock balance detected! ]\n");
2882 printk( "-------------------------------------\n");
2883 printk("%s/%d is trying to release lock (",
2884 curr->comm, task_pid_nr(curr));
2885 print_lockdep_cache(lock);
2888 printk("but there are no more locks to release!\n");
2889 printk("\nother info that might help us debug this:\n");
2890 lockdep_print_held_locks(curr);
2892 printk("\nstack backtrace:\n");
2899 * Common debugging checks for both nested and non-nested unlock:
2901 static int check_unlock(struct task_struct *curr, struct lockdep_map *lock,
2904 if (unlikely(!debug_locks))
2906 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2909 if (curr->lockdep_depth <= 0)
2910 return print_unlock_inbalance_bug(curr, lock, ip);
2915 static int match_held_lock(struct held_lock *hlock, struct lockdep_map *lock)
2917 if (hlock->instance == lock)
2920 if (hlock->references) {
2921 struct lock_class *class = lock->class_cache;
2924 class = look_up_lock_class(lock, 0);
2926 if (DEBUG_LOCKS_WARN_ON(!class))
2929 if (DEBUG_LOCKS_WARN_ON(!hlock->nest_lock))
2932 if (hlock->class_idx == class - lock_classes + 1)
2940 __lock_set_class(struct lockdep_map *lock, const char *name,
2941 struct lock_class_key *key, unsigned int subclass,
2944 struct task_struct *curr = current;
2945 struct held_lock *hlock, *prev_hlock;
2946 struct lock_class *class;
2950 depth = curr->lockdep_depth;
2951 if (DEBUG_LOCKS_WARN_ON(!depth))
2955 for (i = depth-1; i >= 0; i--) {
2956 hlock = curr->held_locks + i;
2958 * We must not cross into another context:
2960 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
2962 if (match_held_lock(hlock, lock))
2966 return print_unlock_inbalance_bug(curr, lock, ip);
2969 lockdep_init_map(lock, name, key, 0);
2970 class = register_lock_class(lock, subclass, 0);
2971 hlock->class_idx = class - lock_classes + 1;
2973 curr->lockdep_depth = i;
2974 curr->curr_chain_key = hlock->prev_chain_key;
2976 for (; i < depth; i++) {
2977 hlock = curr->held_locks + i;
2978 if (!__lock_acquire(hlock->instance,
2979 hlock_class(hlock)->subclass, hlock->trylock,
2980 hlock->read, hlock->check, hlock->hardirqs_off,
2981 hlock->nest_lock, hlock->acquire_ip,
2986 if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth))
2992 * Remove the lock to the list of currently held locks in a
2993 * potentially non-nested (out of order) manner. This is a
2994 * relatively rare operation, as all the unlock APIs default
2995 * to nested mode (which uses lock_release()):
2998 lock_release_non_nested(struct task_struct *curr,
2999 struct lockdep_map *lock, unsigned long ip)
3001 struct held_lock *hlock, *prev_hlock;
3006 * Check whether the lock exists in the current stack
3009 depth = curr->lockdep_depth;
3010 if (DEBUG_LOCKS_WARN_ON(!depth))
3014 for (i = depth-1; i >= 0; i--) {
3015 hlock = curr->held_locks + i;
3017 * We must not cross into another context:
3019 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3021 if (match_held_lock(hlock, lock))
3025 return print_unlock_inbalance_bug(curr, lock, ip);
3028 if (hlock->instance == lock)
3029 lock_release_holdtime(hlock);
3031 if (hlock->references) {
3032 hlock->references--;
3033 if (hlock->references) {
3035 * We had, and after removing one, still have
3036 * references, the current lock stack is still
3037 * valid. We're done!
3044 * We have the right lock to unlock, 'hlock' points to it.
3045 * Now we remove it from the stack, and add back the other
3046 * entries (if any), recalculating the hash along the way:
3049 curr->lockdep_depth = i;
3050 curr->curr_chain_key = hlock->prev_chain_key;
3052 for (i++; i < depth; i++) {
3053 hlock = curr->held_locks + i;
3054 if (!__lock_acquire(hlock->instance,
3055 hlock_class(hlock)->subclass, hlock->trylock,
3056 hlock->read, hlock->check, hlock->hardirqs_off,
3057 hlock->nest_lock, hlock->acquire_ip,
3062 if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - 1))
3068 * Remove the lock to the list of currently held locks - this gets
3069 * called on mutex_unlock()/spin_unlock*() (or on a failed
3070 * mutex_lock_interruptible()). This is done for unlocks that nest
3071 * perfectly. (i.e. the current top of the lock-stack is unlocked)
3073 static int lock_release_nested(struct task_struct *curr,
3074 struct lockdep_map *lock, unsigned long ip)
3076 struct held_lock *hlock;
3080 * Pop off the top of the lock stack:
3082 depth = curr->lockdep_depth - 1;
3083 hlock = curr->held_locks + depth;
3086 * Is the unlock non-nested:
3088 if (hlock->instance != lock || hlock->references)
3089 return lock_release_non_nested(curr, lock, ip);
3090 curr->lockdep_depth--;
3092 if (DEBUG_LOCKS_WARN_ON(!depth && (hlock->prev_chain_key != 0)))
3095 curr->curr_chain_key = hlock->prev_chain_key;
3097 lock_release_holdtime(hlock);
3099 #ifdef CONFIG_DEBUG_LOCKDEP
3100 hlock->prev_chain_key = 0;
3101 hlock->class_idx = 0;
3102 hlock->acquire_ip = 0;
3103 hlock->irq_context = 0;
3109 * Remove the lock to the list of currently held locks - this gets
3110 * called on mutex_unlock()/spin_unlock*() (or on a failed
3111 * mutex_lock_interruptible()). This is done for unlocks that nest
3112 * perfectly. (i.e. the current top of the lock-stack is unlocked)
3115 __lock_release(struct lockdep_map *lock, int nested, unsigned long ip)
3117 struct task_struct *curr = current;
3119 if (!check_unlock(curr, lock, ip))
3123 if (!lock_release_nested(curr, lock, ip))
3126 if (!lock_release_non_nested(curr, lock, ip))
3130 check_chain_key(curr);
3133 static int __lock_is_held(struct lockdep_map *lock)
3135 struct task_struct *curr = current;
3138 for (i = 0; i < curr->lockdep_depth; i++) {
3139 struct held_lock *hlock = curr->held_locks + i;
3141 if (match_held_lock(hlock, lock))
3149 * Check whether we follow the irq-flags state precisely:
3151 static void check_flags(unsigned long flags)
3153 #if defined(CONFIG_PROVE_LOCKING) && defined(CONFIG_DEBUG_LOCKDEP) && \
3154 defined(CONFIG_TRACE_IRQFLAGS)
3158 if (irqs_disabled_flags(flags)) {
3159 if (DEBUG_LOCKS_WARN_ON(current->hardirqs_enabled)) {
3160 printk("possible reason: unannotated irqs-off.\n");
3163 if (DEBUG_LOCKS_WARN_ON(!current->hardirqs_enabled)) {
3164 printk("possible reason: unannotated irqs-on.\n");
3169 * We dont accurately track softirq state in e.g.
3170 * hardirq contexts (such as on 4KSTACKS), so only
3171 * check if not in hardirq contexts:
3173 if (!hardirq_count()) {
3174 if (softirq_count())
3175 DEBUG_LOCKS_WARN_ON(current->softirqs_enabled);
3177 DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled);
3181 print_irqtrace_events(current);
3185 void lock_set_class(struct lockdep_map *lock, const char *name,
3186 struct lock_class_key *key, unsigned int subclass,
3189 unsigned long flags;
3191 if (unlikely(current->lockdep_recursion))
3194 raw_local_irq_save(flags);
3195 current->lockdep_recursion = 1;
3197 if (__lock_set_class(lock, name, key, subclass, ip))
3198 check_chain_key(current);
3199 current->lockdep_recursion = 0;
3200 raw_local_irq_restore(flags);
3202 EXPORT_SYMBOL_GPL(lock_set_class);
3205 * We are not always called with irqs disabled - do that here,
3206 * and also avoid lockdep recursion:
3208 void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
3209 int trylock, int read, int check,
3210 struct lockdep_map *nest_lock, unsigned long ip)
3212 unsigned long flags;
3214 if (unlikely(current->lockdep_recursion))
3217 raw_local_irq_save(flags);
3220 current->lockdep_recursion = 1;
3221 trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip);
3222 __lock_acquire(lock, subclass, trylock, read, check,
3223 irqs_disabled_flags(flags), nest_lock, ip, 0);
3224 current->lockdep_recursion = 0;
3225 raw_local_irq_restore(flags);
3227 EXPORT_SYMBOL_GPL(lock_acquire);
3229 void lock_release(struct lockdep_map *lock, int nested,
3232 unsigned long flags;
3234 if (unlikely(current->lockdep_recursion))
3237 raw_local_irq_save(flags);
3239 current->lockdep_recursion = 1;
3240 trace_lock_release(lock, ip);
3241 __lock_release(lock, nested, ip);
3242 current->lockdep_recursion = 0;
3243 raw_local_irq_restore(flags);
3245 EXPORT_SYMBOL_GPL(lock_release);
3247 int lock_is_held(struct lockdep_map *lock)
3249 unsigned long flags;
3252 if (unlikely(current->lockdep_recursion))
3255 raw_local_irq_save(flags);
3258 current->lockdep_recursion = 1;
3259 ret = __lock_is_held(lock);
3260 current->lockdep_recursion = 0;
3261 raw_local_irq_restore(flags);
3265 EXPORT_SYMBOL_GPL(lock_is_held);
3267 void lockdep_set_current_reclaim_state(gfp_t gfp_mask)
3269 current->lockdep_reclaim_gfp = gfp_mask;
3272 void lockdep_clear_current_reclaim_state(void)
3274 current->lockdep_reclaim_gfp = 0;
3277 #ifdef CONFIG_LOCK_STAT
3279 print_lock_contention_bug(struct task_struct *curr, struct lockdep_map *lock,
3282 if (!debug_locks_off())
3284 if (debug_locks_silent)
3287 printk("\n=================================\n");
3288 printk( "[ BUG: bad contention detected! ]\n");
3289 printk( "---------------------------------\n");
3290 printk("%s/%d is trying to contend lock (",
3291 curr->comm, task_pid_nr(curr));
3292 print_lockdep_cache(lock);
3295 printk("but there are no locks held!\n");
3296 printk("\nother info that might help us debug this:\n");
3297 lockdep_print_held_locks(curr);
3299 printk("\nstack backtrace:\n");
3306 __lock_contended(struct lockdep_map *lock, unsigned long ip)
3308 struct task_struct *curr = current;
3309 struct held_lock *hlock, *prev_hlock;
3310 struct lock_class_stats *stats;
3312 int i, contention_point, contending_point;
3314 depth = curr->lockdep_depth;
3315 if (DEBUG_LOCKS_WARN_ON(!depth))
3319 for (i = depth-1; i >= 0; i--) {
3320 hlock = curr->held_locks + i;
3322 * We must not cross into another context:
3324 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3326 if (match_held_lock(hlock, lock))
3330 print_lock_contention_bug(curr, lock, ip);
3334 if (hlock->instance != lock)
3337 hlock->waittime_stamp = lockstat_clock();
3339 contention_point = lock_point(hlock_class(hlock)->contention_point, ip);
3340 contending_point = lock_point(hlock_class(hlock)->contending_point,
3343 stats = get_lock_stats(hlock_class(hlock));
3344 if (contention_point < LOCKSTAT_POINTS)
3345 stats->contention_point[contention_point]++;
3346 if (contending_point < LOCKSTAT_POINTS)
3347 stats->contending_point[contending_point]++;
3348 if (lock->cpu != smp_processor_id())
3349 stats->bounces[bounce_contended + !!hlock->read]++;
3350 put_lock_stats(stats);
3354 __lock_acquired(struct lockdep_map *lock, unsigned long ip)
3356 struct task_struct *curr = current;
3357 struct held_lock *hlock, *prev_hlock;
3358 struct lock_class_stats *stats;
3360 u64 now, waittime = 0;
3363 depth = curr->lockdep_depth;
3364 if (DEBUG_LOCKS_WARN_ON(!depth))
3368 for (i = depth-1; i >= 0; i--) {
3369 hlock = curr->held_locks + i;
3371 * We must not cross into another context:
3373 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3375 if (match_held_lock(hlock, lock))
3379 print_lock_contention_bug(curr, lock, _RET_IP_);
3383 if (hlock->instance != lock)
3386 cpu = smp_processor_id();
3387 if (hlock->waittime_stamp) {
3388 now = lockstat_clock();
3389 waittime = now - hlock->waittime_stamp;
3390 hlock->holdtime_stamp = now;
3393 trace_lock_acquired(lock, ip);
3395 stats = get_lock_stats(hlock_class(hlock));
3398 lock_time_inc(&stats->read_waittime, waittime);
3400 lock_time_inc(&stats->write_waittime, waittime);
3402 if (lock->cpu != cpu)
3403 stats->bounces[bounce_acquired + !!hlock->read]++;
3404 put_lock_stats(stats);
3410 void lock_contended(struct lockdep_map *lock, unsigned long ip)
3412 unsigned long flags;
3414 if (unlikely(!lock_stat))
3417 if (unlikely(current->lockdep_recursion))
3420 raw_local_irq_save(flags);
3422 current->lockdep_recursion = 1;
3423 trace_lock_contended(lock, ip);
3424 __lock_contended(lock, ip);
3425 current->lockdep_recursion = 0;
3426 raw_local_irq_restore(flags);
3428 EXPORT_SYMBOL_GPL(lock_contended);
3430 void lock_acquired(struct lockdep_map *lock, unsigned long ip)
3432 unsigned long flags;
3434 if (unlikely(!lock_stat))
3437 if (unlikely(current->lockdep_recursion))
3440 raw_local_irq_save(flags);
3442 current->lockdep_recursion = 1;
3443 __lock_acquired(lock, ip);
3444 current->lockdep_recursion = 0;
3445 raw_local_irq_restore(flags);
3447 EXPORT_SYMBOL_GPL(lock_acquired);
3451 * Used by the testsuite, sanitize the validator state
3452 * after a simulated failure:
3455 void lockdep_reset(void)
3457 unsigned long flags;
3460 raw_local_irq_save(flags);
3461 current->curr_chain_key = 0;
3462 current->lockdep_depth = 0;
3463 current->lockdep_recursion = 0;
3464 memset(current->held_locks, 0, MAX_LOCK_DEPTH*sizeof(struct held_lock));
3465 nr_hardirq_chains = 0;
3466 nr_softirq_chains = 0;
3467 nr_process_chains = 0;
3469 for (i = 0; i < CHAINHASH_SIZE; i++)
3470 INIT_LIST_HEAD(chainhash_table + i);
3471 raw_local_irq_restore(flags);
3474 static void zap_class(struct lock_class *class)
3479 * Remove all dependencies this lock is
3482 for (i = 0; i < nr_list_entries; i++) {
3483 if (list_entries[i].class == class)
3484 list_del_rcu(&list_entries[i].entry);
3487 * Unhash the class and remove it from the all_lock_classes list:
3489 list_del_rcu(&class->hash_entry);
3490 list_del_rcu(&class->lock_entry);
3495 static inline int within(const void *addr, void *start, unsigned long size)
3497 return addr >= start && addr < start + size;
3500 void lockdep_free_key_range(void *start, unsigned long size)
3502 struct lock_class *class, *next;
3503 struct list_head *head;
3504 unsigned long flags;
3508 raw_local_irq_save(flags);
3509 locked = graph_lock();
3512 * Unhash all classes that were created by this module:
3514 for (i = 0; i < CLASSHASH_SIZE; i++) {
3515 head = classhash_table + i;
3516 if (list_empty(head))
3518 list_for_each_entry_safe(class, next, head, hash_entry) {
3519 if (within(class->key, start, size))
3521 else if (within(class->name, start, size))
3528 raw_local_irq_restore(flags);
3531 void lockdep_reset_lock(struct lockdep_map *lock)
3533 struct lock_class *class, *next;
3534 struct list_head *head;
3535 unsigned long flags;
3539 raw_local_irq_save(flags);
3542 * Remove all classes this lock might have:
3544 for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) {
3546 * If the class exists we look it up and zap it:
3548 class = look_up_lock_class(lock, j);
3553 * Debug check: in the end all mapped classes should
3556 locked = graph_lock();
3557 for (i = 0; i < CLASSHASH_SIZE; i++) {
3558 head = classhash_table + i;
3559 if (list_empty(head))
3561 list_for_each_entry_safe(class, next, head, hash_entry) {
3562 if (unlikely(class == lock->class_cache)) {
3563 if (debug_locks_off_graph_unlock())
3573 raw_local_irq_restore(flags);
3576 void lockdep_init(void)
3581 * Some architectures have their own start_kernel()
3582 * code which calls lockdep_init(), while we also
3583 * call lockdep_init() from the start_kernel() itself,
3584 * and we want to initialize the hashes only once:
3586 if (lockdep_initialized)
3589 for (i = 0; i < CLASSHASH_SIZE; i++)
3590 INIT_LIST_HEAD(classhash_table + i);
3592 for (i = 0; i < CHAINHASH_SIZE; i++)
3593 INIT_LIST_HEAD(chainhash_table + i);
3595 lockdep_initialized = 1;
3598 void __init lockdep_info(void)
3600 printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");
3602 printk("... MAX_LOCKDEP_SUBCLASSES: %lu\n", MAX_LOCKDEP_SUBCLASSES);
3603 printk("... MAX_LOCK_DEPTH: %lu\n", MAX_LOCK_DEPTH);
3604 printk("... MAX_LOCKDEP_KEYS: %lu\n", MAX_LOCKDEP_KEYS);
3605 printk("... CLASSHASH_SIZE: %lu\n", CLASSHASH_SIZE);
3606 printk("... MAX_LOCKDEP_ENTRIES: %lu\n", MAX_LOCKDEP_ENTRIES);
3607 printk("... MAX_LOCKDEP_CHAINS: %lu\n", MAX_LOCKDEP_CHAINS);
3608 printk("... CHAINHASH_SIZE: %lu\n", CHAINHASH_SIZE);
3610 printk(" memory used by lock dependency info: %lu kB\n",
3611 (sizeof(struct lock_class) * MAX_LOCKDEP_KEYS +
3612 sizeof(struct list_head) * CLASSHASH_SIZE +
3613 sizeof(struct lock_list) * MAX_LOCKDEP_ENTRIES +
3614 sizeof(struct lock_chain) * MAX_LOCKDEP_CHAINS +
3615 sizeof(struct list_head) * CHAINHASH_SIZE
3616 #ifdef CONFIG_PROVE_LOCKING
3617 + sizeof(struct circular_queue)
3622 printk(" per task-struct memory footprint: %lu bytes\n",
3623 sizeof(struct held_lock) * MAX_LOCK_DEPTH);
3625 #ifdef CONFIG_DEBUG_LOCKDEP
3626 if (lockdep_init_error) {
3627 printk("WARNING: lockdep init error! Arch code didn't call lockdep_init() early enough?\n");
3628 printk("Call stack leading to lockdep invocation was:\n");
3629 print_stack_trace(&lockdep_init_trace, 0);
3635 print_freed_lock_bug(struct task_struct *curr, const void *mem_from,
3636 const void *mem_to, struct held_lock *hlock)
3638 if (!debug_locks_off())
3640 if (debug_locks_silent)
3643 printk("\n=========================\n");
3644 printk( "[ BUG: held lock freed! ]\n");
3645 printk( "-------------------------\n");
3646 printk("%s/%d is freeing memory %p-%p, with a lock still held there!\n",
3647 curr->comm, task_pid_nr(curr), mem_from, mem_to-1);
3649 lockdep_print_held_locks(curr);
3651 printk("\nstack backtrace:\n");
3655 static inline int not_in_range(const void* mem_from, unsigned long mem_len,
3656 const void* lock_from, unsigned long lock_len)
3658 return lock_from + lock_len <= mem_from ||
3659 mem_from + mem_len <= lock_from;
3663 * Called when kernel memory is freed (or unmapped), or if a lock
3664 * is destroyed or reinitialized - this code checks whether there is
3665 * any held lock in the memory range of <from> to <to>:
3667 void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len)
3669 struct task_struct *curr = current;
3670 struct held_lock *hlock;
3671 unsigned long flags;
3674 if (unlikely(!debug_locks))
3677 local_irq_save(flags);
3678 for (i = 0; i < curr->lockdep_depth; i++) {
3679 hlock = curr->held_locks + i;
3681 if (not_in_range(mem_from, mem_len, hlock->instance,
3682 sizeof(*hlock->instance)))
3685 print_freed_lock_bug(curr, mem_from, mem_from + mem_len, hlock);
3688 local_irq_restore(flags);
3690 EXPORT_SYMBOL_GPL(debug_check_no_locks_freed);
3692 static void print_held_locks_bug(struct task_struct *curr)
3694 if (!debug_locks_off())
3696 if (debug_locks_silent)
3699 printk("\n=====================================\n");
3700 printk( "[ BUG: lock held at task exit time! ]\n");
3701 printk( "-------------------------------------\n");
3702 printk("%s/%d is exiting with locks still held!\n",
3703 curr->comm, task_pid_nr(curr));
3704 lockdep_print_held_locks(curr);
3706 printk("\nstack backtrace:\n");
3710 void debug_check_no_locks_held(struct task_struct *task)
3712 if (unlikely(task->lockdep_depth > 0))
3713 print_held_locks_bug(task);
3716 void debug_show_all_locks(void)
3718 struct task_struct *g, *p;
3722 if (unlikely(!debug_locks)) {
3723 printk("INFO: lockdep is turned off.\n");
3726 printk("\nShowing all locks held in the system:\n");
3729 * Here we try to get the tasklist_lock as hard as possible,
3730 * if not successful after 2 seconds we ignore it (but keep
3731 * trying). This is to enable a debug printout even if a
3732 * tasklist_lock-holding task deadlocks or crashes.
3735 if (!read_trylock(&tasklist_lock)) {
3737 printk("hm, tasklist_lock locked, retrying... ");
3740 printk(" #%d", 10-count);
3744 printk(" ignoring it.\n");
3748 printk(KERN_CONT " locked it.\n");
3751 do_each_thread(g, p) {
3753 * It's not reliable to print a task's held locks
3754 * if it's not sleeping (or if it's not the current
3757 if (p->state == TASK_RUNNING && p != current)
3759 if (p->lockdep_depth)
3760 lockdep_print_held_locks(p);
3762 if (read_trylock(&tasklist_lock))
3764 } while_each_thread(g, p);
3767 printk("=============================================\n\n");
3770 read_unlock(&tasklist_lock);
3772 EXPORT_SYMBOL_GPL(debug_show_all_locks);
3775 * Careful: only use this function if you are sure that
3776 * the task cannot run in parallel!
3778 void __debug_show_held_locks(struct task_struct *task)
3780 if (unlikely(!debug_locks)) {
3781 printk("INFO: lockdep is turned off.\n");
3784 lockdep_print_held_locks(task);
3786 EXPORT_SYMBOL_GPL(__debug_show_held_locks);
3788 void debug_show_held_locks(struct task_struct *task)
3790 __debug_show_held_locks(task);
3792 EXPORT_SYMBOL_GPL(debug_show_held_locks);
3794 void lockdep_sys_exit(void)
3796 struct task_struct *curr = current;
3798 if (unlikely(curr->lockdep_depth)) {
3799 if (!debug_locks_off())
3801 printk("\n================================================\n");
3802 printk( "[ BUG: lock held when returning to user space! ]\n");
3803 printk( "------------------------------------------------\n");
3804 printk("%s/%d is leaving the kernel with locks still held!\n",
3805 curr->comm, curr->pid);
3806 lockdep_print_held_locks(curr);
3810 void lockdep_rcu_dereference(const char *file, const int line)
3812 struct task_struct *curr = current;
3814 #ifndef CONFIG_PROVE_RCU_REPEATEDLY
3815 if (!debug_locks_off())
3817 #endif /* #ifdef CONFIG_PROVE_RCU_REPEATEDLY */
3818 /* Note: the following can be executed concurrently, so be careful. */
3819 printk("\n===================================================\n");
3820 printk( "[ INFO: suspicious rcu_dereference_check() usage. ]\n");
3821 printk( "---------------------------------------------------\n");
3822 printk("%s:%d invoked rcu_dereference_check() without protection!\n",
3824 printk("\nother info that might help us debug this:\n\n");
3825 printk("\nrcu_scheduler_active = %d, debug_locks = %d\n", rcu_scheduler_active, debug_locks);
3826 lockdep_print_held_locks(curr);
3827 printk("\nstack backtrace:\n");
3830 EXPORT_SYMBOL_GPL(lockdep_rcu_dereference);