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 <asm/sections.h>
48 #include "lockdep_internals.h"
50 #define CREATE_TRACE_POINTS
51 #include <trace/events/lockdep.h>
53 #ifdef CONFIG_PROVE_LOCKING
54 int prove_locking = 1;
55 module_param(prove_locking, int, 0644);
57 #define prove_locking 0
60 #ifdef CONFIG_LOCK_STAT
62 module_param(lock_stat, int, 0644);
68 * lockdep_lock: protects the lockdep graph, the hashes and the
69 * class/list/hash allocators.
71 * This is one of the rare exceptions where it's justified
72 * to use a raw spinlock - we really dont want the spinlock
73 * code to recurse back into the lockdep code...
75 static raw_spinlock_t lockdep_lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
77 static int graph_lock(void)
79 __raw_spin_lock(&lockdep_lock);
81 * Make sure that if another CPU detected a bug while
82 * walking the graph we dont change it (while the other
83 * CPU is busy printing out stuff with the graph lock
87 __raw_spin_unlock(&lockdep_lock);
90 /* prevent any recursions within lockdep from causing deadlocks */
91 current->lockdep_recursion++;
95 static inline int graph_unlock(void)
97 if (debug_locks && !__raw_spin_is_locked(&lockdep_lock))
98 return DEBUG_LOCKS_WARN_ON(1);
100 current->lockdep_recursion--;
101 __raw_spin_unlock(&lockdep_lock);
106 * Turn lock debugging off and return with 0 if it was off already,
107 * and also release the graph lock:
109 static inline int debug_locks_off_graph_unlock(void)
111 int ret = debug_locks_off();
113 __raw_spin_unlock(&lockdep_lock);
118 static int lockdep_initialized;
120 unsigned long nr_list_entries;
121 struct lock_list list_entries[MAX_LOCKDEP_ENTRIES];
124 * All data structures here are protected by the global debug_lock.
126 * Mutex key structs only get allocated, once during bootup, and never
127 * get freed - this significantly simplifies the debugging code.
129 unsigned long nr_lock_classes;
130 static struct lock_class lock_classes[MAX_LOCKDEP_KEYS];
132 static inline struct lock_class *hlock_class(struct held_lock *hlock)
134 if (!hlock->class_idx) {
135 DEBUG_LOCKS_WARN_ON(1);
138 return lock_classes + hlock->class_idx - 1;
141 #ifdef CONFIG_LOCK_STAT
142 static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS], lock_stats);
144 static int lock_point(unsigned long points[], unsigned long ip)
148 for (i = 0; i < LOCKSTAT_POINTS; i++) {
149 if (points[i] == 0) {
160 static void lock_time_inc(struct lock_time *lt, s64 time)
165 if (time < lt->min || !lt->min)
172 static inline void lock_time_add(struct lock_time *src, struct lock_time *dst)
174 dst->min += src->min;
175 dst->max += src->max;
176 dst->total += src->total;
180 struct lock_class_stats lock_stats(struct lock_class *class)
182 struct lock_class_stats stats;
185 memset(&stats, 0, sizeof(struct lock_class_stats));
186 for_each_possible_cpu(cpu) {
187 struct lock_class_stats *pcs =
188 &per_cpu(lock_stats, cpu)[class - lock_classes];
190 for (i = 0; i < ARRAY_SIZE(stats.contention_point); i++)
191 stats.contention_point[i] += pcs->contention_point[i];
193 for (i = 0; i < ARRAY_SIZE(stats.contending_point); i++)
194 stats.contending_point[i] += pcs->contending_point[i];
196 lock_time_add(&pcs->read_waittime, &stats.read_waittime);
197 lock_time_add(&pcs->write_waittime, &stats.write_waittime);
199 lock_time_add(&pcs->read_holdtime, &stats.read_holdtime);
200 lock_time_add(&pcs->write_holdtime, &stats.write_holdtime);
202 for (i = 0; i < ARRAY_SIZE(stats.bounces); i++)
203 stats.bounces[i] += pcs->bounces[i];
209 void clear_lock_stats(struct lock_class *class)
213 for_each_possible_cpu(cpu) {
214 struct lock_class_stats *cpu_stats =
215 &per_cpu(lock_stats, cpu)[class - lock_classes];
217 memset(cpu_stats, 0, sizeof(struct lock_class_stats));
219 memset(class->contention_point, 0, sizeof(class->contention_point));
220 memset(class->contending_point, 0, sizeof(class->contending_point));
223 static struct lock_class_stats *get_lock_stats(struct lock_class *class)
225 return &get_cpu_var(lock_stats)[class - lock_classes];
228 static void put_lock_stats(struct lock_class_stats *stats)
230 put_cpu_var(lock_stats);
233 static void lock_release_holdtime(struct held_lock *hlock)
235 struct lock_class_stats *stats;
241 holdtime = sched_clock() - hlock->holdtime_stamp;
243 stats = get_lock_stats(hlock_class(hlock));
245 lock_time_inc(&stats->read_holdtime, holdtime);
247 lock_time_inc(&stats->write_holdtime, holdtime);
248 put_lock_stats(stats);
251 static inline void lock_release_holdtime(struct held_lock *hlock)
257 * We keep a global list of all lock classes. The list only grows,
258 * never shrinks. The list is only accessed with the lockdep
259 * spinlock lock held.
261 LIST_HEAD(all_lock_classes);
264 * The lockdep classes are in a hash-table as well, for fast lookup:
266 #define CLASSHASH_BITS (MAX_LOCKDEP_KEYS_BITS - 1)
267 #define CLASSHASH_SIZE (1UL << CLASSHASH_BITS)
268 #define __classhashfn(key) hash_long((unsigned long)key, CLASSHASH_BITS)
269 #define classhashentry(key) (classhash_table + __classhashfn((key)))
271 static struct list_head classhash_table[CLASSHASH_SIZE];
274 * We put the lock dependency chains into a hash-table as well, to cache
277 #define CHAINHASH_BITS (MAX_LOCKDEP_CHAINS_BITS-1)
278 #define CHAINHASH_SIZE (1UL << CHAINHASH_BITS)
279 #define __chainhashfn(chain) hash_long(chain, CHAINHASH_BITS)
280 #define chainhashentry(chain) (chainhash_table + __chainhashfn((chain)))
282 static struct list_head chainhash_table[CHAINHASH_SIZE];
285 * The hash key of the lock dependency chains is a hash itself too:
286 * it's a hash of all locks taken up to that lock, including that lock.
287 * It's a 64-bit hash, because it's important for the keys to be
290 #define iterate_chain_key(key1, key2) \
291 (((key1) << MAX_LOCKDEP_KEYS_BITS) ^ \
292 ((key1) >> (64-MAX_LOCKDEP_KEYS_BITS)) ^ \
295 void lockdep_off(void)
297 current->lockdep_recursion++;
299 EXPORT_SYMBOL(lockdep_off);
301 void lockdep_on(void)
303 current->lockdep_recursion--;
305 EXPORT_SYMBOL(lockdep_on);
308 * Debugging switches:
312 #define VERY_VERBOSE 0
315 # define HARDIRQ_VERBOSE 1
316 # define SOFTIRQ_VERBOSE 1
317 # define RECLAIM_VERBOSE 1
319 # define HARDIRQ_VERBOSE 0
320 # define SOFTIRQ_VERBOSE 0
321 # define RECLAIM_VERBOSE 0
324 #if VERBOSE || HARDIRQ_VERBOSE || SOFTIRQ_VERBOSE || RECLAIM_VERBOSE
326 * Quick filtering for interesting events:
328 static int class_filter(struct lock_class *class)
332 if (class->name_version == 1 &&
333 !strcmp(class->name, "lockname"))
335 if (class->name_version == 1 &&
336 !strcmp(class->name, "&struct->lockfield"))
339 /* Filter everything else. 1 would be to allow everything else */
344 static int verbose(struct lock_class *class)
347 return class_filter(class);
353 * Stack-trace: tightly packed array of stack backtrace
354 * addresses. Protected by the graph_lock.
356 unsigned long nr_stack_trace_entries;
357 static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];
359 static int save_trace(struct stack_trace *trace)
361 trace->nr_entries = 0;
362 trace->max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries;
363 trace->entries = stack_trace + nr_stack_trace_entries;
367 save_stack_trace(trace);
369 trace->max_entries = trace->nr_entries;
371 nr_stack_trace_entries += trace->nr_entries;
373 if (nr_stack_trace_entries == MAX_STACK_TRACE_ENTRIES) {
374 if (!debug_locks_off_graph_unlock())
377 printk("BUG: MAX_STACK_TRACE_ENTRIES too low!\n");
378 printk("turning off the locking correctness validator.\n");
387 unsigned int nr_hardirq_chains;
388 unsigned int nr_softirq_chains;
389 unsigned int nr_process_chains;
390 unsigned int max_lockdep_depth;
391 unsigned int max_recursion_depth;
393 static unsigned int lockdep_dependency_gen_id;
395 static bool lockdep_dependency_visit(struct lock_class *source,
399 lockdep_dependency_gen_id++;
400 if (source->dep_gen_id == lockdep_dependency_gen_id)
402 source->dep_gen_id = lockdep_dependency_gen_id;
406 #ifdef CONFIG_DEBUG_LOCKDEP
408 * We cannot printk in early bootup code. Not even early_printk()
409 * might work. So we mark any initialization errors and printk
410 * about it later on, in lockdep_info().
412 static int lockdep_init_error;
413 static unsigned long lockdep_init_trace_data[20];
414 static struct stack_trace lockdep_init_trace = {
415 .max_entries = ARRAY_SIZE(lockdep_init_trace_data),
416 .entries = lockdep_init_trace_data,
420 * Various lockdep statistics:
422 atomic_t chain_lookup_hits;
423 atomic_t chain_lookup_misses;
424 atomic_t hardirqs_on_events;
425 atomic_t hardirqs_off_events;
426 atomic_t redundant_hardirqs_on;
427 atomic_t redundant_hardirqs_off;
428 atomic_t softirqs_on_events;
429 atomic_t softirqs_off_events;
430 atomic_t redundant_softirqs_on;
431 atomic_t redundant_softirqs_off;
432 atomic_t nr_unused_locks;
433 atomic_t nr_cyclic_checks;
434 atomic_t nr_cyclic_check_recursions;
435 atomic_t nr_find_usage_forwards_checks;
436 atomic_t nr_find_usage_forwards_recursions;
437 atomic_t nr_find_usage_backwards_checks;
438 atomic_t nr_find_usage_backwards_recursions;
445 #define __USAGE(__STATE) \
446 [LOCK_USED_IN_##__STATE] = "IN-"__stringify(__STATE)"-W", \
447 [LOCK_ENABLED_##__STATE] = __stringify(__STATE)"-ON-W", \
448 [LOCK_USED_IN_##__STATE##_READ] = "IN-"__stringify(__STATE)"-R",\
449 [LOCK_ENABLED_##__STATE##_READ] = __stringify(__STATE)"-ON-R",
451 static const char *usage_str[] =
453 #define LOCKDEP_STATE(__STATE) __USAGE(__STATE)
454 #include "lockdep_states.h"
456 [LOCK_USED] = "INITIAL USE",
459 const char * __get_key_name(struct lockdep_subclass_key *key, char *str)
461 return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str);
464 static inline unsigned long lock_flag(enum lock_usage_bit bit)
469 static char get_usage_char(struct lock_class *class, enum lock_usage_bit bit)
473 if (class->usage_mask & lock_flag(bit + 2))
475 if (class->usage_mask & lock_flag(bit)) {
477 if (class->usage_mask & lock_flag(bit + 2))
484 void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS])
488 #define LOCKDEP_STATE(__STATE) \
489 usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE); \
490 usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE##_READ);
491 #include "lockdep_states.h"
497 static void print_lock_name(struct lock_class *class)
499 char str[KSYM_NAME_LEN], usage[LOCK_USAGE_CHARS];
502 get_usage_chars(class, usage);
506 name = __get_key_name(class->key, str);
507 printk(" (%s", name);
509 printk(" (%s", name);
510 if (class->name_version > 1)
511 printk("#%d", class->name_version);
513 printk("/%d", class->subclass);
515 printk("){%s}", usage);
518 static void print_lockdep_cache(struct lockdep_map *lock)
521 char str[KSYM_NAME_LEN];
525 name = __get_key_name(lock->key->subkeys, str);
530 static void print_lock(struct held_lock *hlock)
532 print_lock_name(hlock_class(hlock));
534 print_ip_sym(hlock->acquire_ip);
537 static void lockdep_print_held_locks(struct task_struct *curr)
539 int i, depth = curr->lockdep_depth;
542 printk("no locks held by %s/%d.\n", curr->comm, task_pid_nr(curr));
545 printk("%d lock%s held by %s/%d:\n",
546 depth, depth > 1 ? "s" : "", curr->comm, task_pid_nr(curr));
548 for (i = 0; i < depth; i++) {
550 print_lock(curr->held_locks + i);
554 static void print_lock_class_header(struct lock_class *class, int depth)
558 printk("%*s->", depth, "");
559 print_lock_name(class);
560 printk(" ops: %lu", class->ops);
563 for (bit = 0; bit < LOCK_USAGE_STATES; bit++) {
564 if (class->usage_mask & (1 << bit)) {
567 len += printk("%*s %s", depth, "", usage_str[bit]);
568 len += printk(" at:\n");
569 print_stack_trace(class->usage_traces + bit, len);
572 printk("%*s }\n", depth, "");
574 printk("%*s ... key at: ",depth,"");
575 print_ip_sym((unsigned long)class->key);
579 * printk all lock dependencies starting at <entry>:
582 print_lock_dependencies(struct lock_class *class, int depth)
584 struct lock_list *entry;
586 if (lockdep_dependency_visit(class, depth))
589 if (DEBUG_LOCKS_WARN_ON(depth >= 20))
592 print_lock_class_header(class, depth);
594 list_for_each_entry(entry, &class->locks_after, entry) {
595 if (DEBUG_LOCKS_WARN_ON(!entry->class))
598 print_lock_dependencies(entry->class, depth + 1);
600 printk("%*s ... acquired at:\n",depth,"");
601 print_stack_trace(&entry->trace, 2);
606 static void print_kernel_version(void)
608 printk("%s %.*s\n", init_utsname()->release,
609 (int)strcspn(init_utsname()->version, " "),
610 init_utsname()->version);
613 static int very_verbose(struct lock_class *class)
616 return class_filter(class);
622 * Is this the address of a static object:
624 static int static_obj(void *obj)
626 unsigned long start = (unsigned long) &_stext,
627 end = (unsigned long) &_end,
628 addr = (unsigned long) obj;
636 if ((addr >= start) && (addr < end))
643 for_each_possible_cpu(i) {
644 start = (unsigned long) &__per_cpu_start + per_cpu_offset(i);
645 end = (unsigned long) &__per_cpu_start + PERCPU_ENOUGH_ROOM
648 if ((addr >= start) && (addr < end))
656 return is_module_address(addr);
660 * To make lock name printouts unique, we calculate a unique
661 * class->name_version generation counter:
663 static int count_matching_names(struct lock_class *new_class)
665 struct lock_class *class;
668 if (!new_class->name)
671 list_for_each_entry(class, &all_lock_classes, lock_entry) {
672 if (new_class->key - new_class->subclass == class->key)
673 return class->name_version;
674 if (class->name && !strcmp(class->name, new_class->name))
675 count = max(count, class->name_version);
682 * Register a lock's class in the hash-table, if the class is not present
683 * yet. Otherwise we look it up. We cache the result in the lock object
684 * itself, so actual lookup of the hash should be once per lock object.
686 static inline struct lock_class *
687 look_up_lock_class(struct lockdep_map *lock, unsigned int subclass)
689 struct lockdep_subclass_key *key;
690 struct list_head *hash_head;
691 struct lock_class *class;
693 #ifdef CONFIG_DEBUG_LOCKDEP
695 * If the architecture calls into lockdep before initializing
696 * the hashes then we'll warn about it later. (we cannot printk
699 if (unlikely(!lockdep_initialized)) {
701 lockdep_init_error = 1;
702 save_stack_trace(&lockdep_init_trace);
707 * Static locks do not have their class-keys yet - for them the key
708 * is the lock object itself:
710 if (unlikely(!lock->key))
711 lock->key = (void *)lock;
714 * NOTE: the class-key must be unique. For dynamic locks, a static
715 * lock_class_key variable is passed in through the mutex_init()
716 * (or spin_lock_init()) call - which acts as the key. For static
717 * locks we use the lock object itself as the key.
719 BUILD_BUG_ON(sizeof(struct lock_class_key) >
720 sizeof(struct lockdep_map));
722 key = lock->key->subkeys + subclass;
724 hash_head = classhashentry(key);
727 * We can walk the hash lockfree, because the hash only
728 * grows, and we are careful when adding entries to the end:
730 list_for_each_entry(class, hash_head, hash_entry) {
731 if (class->key == key) {
732 WARN_ON_ONCE(class->name != lock->name);
741 * Register a lock's class in the hash-table, if the class is not present
742 * yet. Otherwise we look it up. We cache the result in the lock object
743 * itself, so actual lookup of the hash should be once per lock object.
745 static inline struct lock_class *
746 register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
748 struct lockdep_subclass_key *key;
749 struct list_head *hash_head;
750 struct lock_class *class;
753 class = look_up_lock_class(lock, subclass);
758 * Debug-check: all keys must be persistent!
760 if (!static_obj(lock->key)) {
762 printk("INFO: trying to register non-static key.\n");
763 printk("the code is fine but needs lockdep annotation.\n");
764 printk("turning off the locking correctness validator.\n");
770 key = lock->key->subkeys + subclass;
771 hash_head = classhashentry(key);
773 raw_local_irq_save(flags);
775 raw_local_irq_restore(flags);
779 * We have to do the hash-walk again, to avoid races
782 list_for_each_entry(class, hash_head, hash_entry)
783 if (class->key == key)
786 * Allocate a new key from the static array, and add it to
789 if (nr_lock_classes >= MAX_LOCKDEP_KEYS) {
790 if (!debug_locks_off_graph_unlock()) {
791 raw_local_irq_restore(flags);
794 raw_local_irq_restore(flags);
796 printk("BUG: MAX_LOCKDEP_KEYS too low!\n");
797 printk("turning off the locking correctness validator.\n");
801 class = lock_classes + nr_lock_classes++;
802 debug_atomic_inc(&nr_unused_locks);
804 class->name = lock->name;
805 class->subclass = subclass;
806 INIT_LIST_HEAD(&class->lock_entry);
807 INIT_LIST_HEAD(&class->locks_before);
808 INIT_LIST_HEAD(&class->locks_after);
809 class->name_version = count_matching_names(class);
811 * We use RCU's safe list-add method to make
812 * parallel walking of the hash-list safe:
814 list_add_tail_rcu(&class->hash_entry, hash_head);
816 * Add it to the global list of classes:
818 list_add_tail_rcu(&class->lock_entry, &all_lock_classes);
820 if (verbose(class)) {
822 raw_local_irq_restore(flags);
824 printk("\nnew class %p: %s", class->key, class->name);
825 if (class->name_version > 1)
826 printk("#%d", class->name_version);
830 raw_local_irq_save(flags);
832 raw_local_irq_restore(flags);
838 raw_local_irq_restore(flags);
840 if (!subclass || force)
841 lock->class_cache = class;
843 if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))
849 #ifdef CONFIG_PROVE_LOCKING
851 * Allocate a lockdep entry. (assumes the graph_lock held, returns
852 * with NULL on failure)
854 static struct lock_list *alloc_list_entry(void)
856 if (nr_list_entries >= MAX_LOCKDEP_ENTRIES) {
857 if (!debug_locks_off_graph_unlock())
860 printk("BUG: MAX_LOCKDEP_ENTRIES too low!\n");
861 printk("turning off the locking correctness validator.\n");
865 return list_entries + nr_list_entries++;
869 * Add a new dependency to the head of the list:
871 static int add_lock_to_list(struct lock_class *class, struct lock_class *this,
872 struct list_head *head, unsigned long ip, int distance)
874 struct lock_list *entry;
876 * Lock not present yet - get a new dependency struct and
877 * add it to the list:
879 entry = alloc_list_entry();
883 if (!save_trace(&entry->trace))
887 entry->distance = distance;
889 * Since we never remove from the dependency list, the list can
890 * be walked lockless by other CPUs, it's only allocation
891 * that must be protected by the spinlock. But this also means
892 * we must make new entries visible only once writes to the
893 * entry become visible - hence the RCU op:
895 list_add_tail_rcu(&entry->entry, head);
900 unsigned long bfs_accessed[BITS_TO_LONGS(MAX_LOCKDEP_ENTRIES)];
901 static struct circular_queue lock_cq;
903 static int __search_shortest_path(struct lock_list *source_entry,
904 struct lock_class *target,
905 struct lock_list **target_entry,
908 struct lock_list *entry;
909 struct list_head *head;
910 struct circular_queue *cq = &lock_cq;
913 if (source_entry->class == target) {
914 *target_entry = source_entry;
920 head = &source_entry->class->locks_after;
922 head = &source_entry->class->locks_before;
924 if (list_empty(head))
928 __cq_enqueue(cq, (unsigned long)source_entry);
930 while (!__cq_empty(cq)) {
931 struct lock_list *lock;
933 __cq_dequeue(cq, (unsigned long *)&lock);
941 head = &lock->class->locks_after;
943 head = &lock->class->locks_before;
945 list_for_each_entry(entry, head, entry) {
946 if (!lock_accessed(entry)) {
947 mark_lock_accessed(entry, lock);
948 if (entry->class == target) {
949 *target_entry = entry;
954 if (__cq_enqueue(cq, (unsigned long)entry)) {
965 static inline int __search_forward_shortest_path(struct lock_list *src_entry,
966 struct lock_class *target,
967 struct lock_list **target_entry)
969 return __search_shortest_path(src_entry, target, target_entry, 1);
973 static inline int __search_backward_shortest_path(struct lock_list *src_entry,
974 struct lock_class *target,
975 struct lock_list **target_entry)
977 return __search_shortest_path(src_entry, target, target_entry, 0);
982 * Recursive, forwards-direction lock-dependency checking, used for
983 * both noncyclic checking and for hardirq-unsafe/softirq-unsafe
986 * (to keep the stackframe of the recursive functions small we
987 * use these global variables, and we also mark various helper
988 * functions as noinline.)
990 static struct held_lock *check_source, *check_target;
993 * Print a dependency chain entry (this is only done when a deadlock
994 * has been detected):
997 print_circular_bug_entry(struct lock_list *target, unsigned int depth)
999 if (debug_locks_silent)
1001 printk("\n-> #%u", depth);
1002 print_lock_name(target->class);
1004 print_stack_trace(&target->trace, 6);
1010 * When a circular dependency is detected, print the
1014 print_circular_bug_header(struct lock_list *entry, unsigned int depth)
1016 struct task_struct *curr = current;
1018 if (debug_locks_silent)
1021 printk("\n=======================================================\n");
1022 printk( "[ INFO: possible circular locking dependency detected ]\n");
1023 print_kernel_version();
1024 printk( "-------------------------------------------------------\n");
1025 printk("%s/%d is trying to acquire lock:\n",
1026 curr->comm, task_pid_nr(curr));
1027 print_lock(check_source);
1028 printk("\nbut task is already holding lock:\n");
1029 print_lock(check_target);
1030 printk("\nwhich lock already depends on the new lock.\n\n");
1031 printk("\nthe existing dependency chain (in reverse order) is:\n");
1033 print_circular_bug_entry(entry, depth);
1038 static noinline int print_circular_bug(void)
1040 struct task_struct *curr = current;
1041 struct lock_list this;
1042 struct lock_list *target;
1043 struct lock_list *parent;
1045 unsigned long depth;
1047 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1050 this.class = hlock_class(check_source);
1052 if (!save_trace(&this.trace))
1055 result = __search_forward_shortest_path(&this,
1056 hlock_class(check_target),
1059 printk("\n%s:search shortest path failed:%d\n", __func__,
1064 depth = get_lock_depth(target);
1066 print_circular_bug_header(target, depth);
1068 parent = get_lock_parent(target);
1071 print_circular_bug_entry(parent, --depth);
1072 parent = get_lock_parent(parent);
1075 printk("\nother info that might help us debug this:\n\n");
1076 lockdep_print_held_locks(curr);
1078 printk("\nstack backtrace:\n");
1084 #define RECURSION_LIMIT 40
1086 static int noinline print_infinite_recursion_bug(void)
1088 if (!debug_locks_off_graph_unlock())
1096 unsigned long __lockdep_count_forward_deps(struct lock_class *class,
1099 struct lock_list *entry;
1100 unsigned long ret = 1;
1102 if (lockdep_dependency_visit(class, depth))
1106 * Recurse this class's dependency list:
1108 list_for_each_entry(entry, &class->locks_after, entry)
1109 ret += __lockdep_count_forward_deps(entry->class, depth + 1);
1114 unsigned long lockdep_count_forward_deps(struct lock_class *class)
1116 unsigned long ret, flags;
1118 local_irq_save(flags);
1119 __raw_spin_lock(&lockdep_lock);
1120 ret = __lockdep_count_forward_deps(class, 0);
1121 __raw_spin_unlock(&lockdep_lock);
1122 local_irq_restore(flags);
1127 unsigned long __lockdep_count_backward_deps(struct lock_class *class,
1130 struct lock_list *entry;
1131 unsigned long ret = 1;
1133 if (lockdep_dependency_visit(class, depth))
1136 * Recurse this class's dependency list:
1138 list_for_each_entry(entry, &class->locks_before, entry)
1139 ret += __lockdep_count_backward_deps(entry->class, depth + 1);
1144 unsigned long lockdep_count_backward_deps(struct lock_class *class)
1146 unsigned long ret, flags;
1148 local_irq_save(flags);
1149 __raw_spin_lock(&lockdep_lock);
1150 ret = __lockdep_count_backward_deps(class, 0);
1151 __raw_spin_unlock(&lockdep_lock);
1152 local_irq_restore(flags);
1158 * Prove that the dependency graph starting at <entry> can not
1159 * lead to <target>. Print an error and return 0 if it does.
1162 check_noncircular(struct lock_class *source, unsigned int depth)
1164 struct lock_list *entry;
1166 if (lockdep_dependency_visit(source, depth))
1169 debug_atomic_inc(&nr_cyclic_check_recursions);
1170 if (depth > max_recursion_depth)
1171 max_recursion_depth = depth;
1172 if (depth >= RECURSION_LIMIT)
1173 return print_infinite_recursion_bug();
1175 * Check this lock's dependency list:
1177 list_for_each_entry(entry, &source->locks_after, entry) {
1178 if (entry->class == hlock_class(check_target))
1180 debug_atomic_inc(&nr_cyclic_checks);
1181 if (check_noncircular(entry->class, depth+1) == 2)
1188 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
1190 * Forwards and backwards subgraph searching, for the purposes of
1191 * proving that two subgraphs can be connected by a new dependency
1192 * without creating any illegal irq-safe -> irq-unsafe lock dependency.
1194 static enum lock_usage_bit find_usage_bit;
1195 static struct lock_class *forwards_match, *backwards_match;
1198 * Find a node in the forwards-direction dependency sub-graph starting
1199 * at <source> that matches <find_usage_bit>.
1201 * Return 2 if such a node exists in the subgraph, and put that node
1202 * into <forwards_match>.
1204 * Return 1 otherwise and keep <forwards_match> unchanged.
1205 * Return 0 on error.
1208 find_usage_forwards(struct lock_class *source, unsigned int depth)
1210 struct lock_list *entry;
1213 if (lockdep_dependency_visit(source, depth))
1216 if (depth > max_recursion_depth)
1217 max_recursion_depth = depth;
1218 if (depth >= RECURSION_LIMIT)
1219 return print_infinite_recursion_bug();
1221 debug_atomic_inc(&nr_find_usage_forwards_checks);
1222 if (source->usage_mask & (1 << find_usage_bit)) {
1223 forwards_match = source;
1228 * Check this lock's dependency list:
1230 list_for_each_entry(entry, &source->locks_after, entry) {
1231 debug_atomic_inc(&nr_find_usage_forwards_recursions);
1232 ret = find_usage_forwards(entry->class, depth+1);
1233 if (ret == 2 || ret == 0)
1240 * Find a node in the backwards-direction dependency sub-graph starting
1241 * at <source> that matches <find_usage_bit>.
1243 * Return 2 if such a node exists in the subgraph, and put that node
1244 * into <backwards_match>.
1246 * Return 1 otherwise and keep <backwards_match> unchanged.
1247 * Return 0 on error.
1250 find_usage_backwards(struct lock_class *source, unsigned int depth)
1252 struct lock_list *entry;
1255 if (lockdep_dependency_visit(source, depth))
1258 if (!__raw_spin_is_locked(&lockdep_lock))
1259 return DEBUG_LOCKS_WARN_ON(1);
1261 if (depth > max_recursion_depth)
1262 max_recursion_depth = depth;
1263 if (depth >= RECURSION_LIMIT)
1264 return print_infinite_recursion_bug();
1266 debug_atomic_inc(&nr_find_usage_backwards_checks);
1267 if (source->usage_mask & (1 << find_usage_bit)) {
1268 backwards_match = source;
1272 if (!source && debug_locks_off_graph_unlock()) {
1278 * Check this lock's dependency list:
1280 list_for_each_entry(entry, &source->locks_before, entry) {
1281 debug_atomic_inc(&nr_find_usage_backwards_recursions);
1282 ret = find_usage_backwards(entry->class, depth+1);
1283 if (ret == 2 || ret == 0)
1290 print_bad_irq_dependency(struct task_struct *curr,
1291 struct held_lock *prev,
1292 struct held_lock *next,
1293 enum lock_usage_bit bit1,
1294 enum lock_usage_bit bit2,
1295 const char *irqclass)
1297 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1300 printk("\n======================================================\n");
1301 printk( "[ INFO: %s-safe -> %s-unsafe lock order detected ]\n",
1302 irqclass, irqclass);
1303 print_kernel_version();
1304 printk( "------------------------------------------------------\n");
1305 printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
1306 curr->comm, task_pid_nr(curr),
1307 curr->hardirq_context, hardirq_count() >> HARDIRQ_SHIFT,
1308 curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT,
1309 curr->hardirqs_enabled,
1310 curr->softirqs_enabled);
1313 printk("\nand this task is already holding:\n");
1315 printk("which would create a new lock dependency:\n");
1316 print_lock_name(hlock_class(prev));
1318 print_lock_name(hlock_class(next));
1321 printk("\nbut this new dependency connects a %s-irq-safe lock:\n",
1323 print_lock_name(backwards_match);
1324 printk("\n... which became %s-irq-safe at:\n", irqclass);
1326 print_stack_trace(backwards_match->usage_traces + bit1, 1);
1328 printk("\nto a %s-irq-unsafe lock:\n", irqclass);
1329 print_lock_name(forwards_match);
1330 printk("\n... which became %s-irq-unsafe at:\n", irqclass);
1333 print_stack_trace(forwards_match->usage_traces + bit2, 1);
1335 printk("\nother info that might help us debug this:\n\n");
1336 lockdep_print_held_locks(curr);
1338 printk("\nthe %s-irq-safe lock's dependencies:\n", irqclass);
1339 print_lock_dependencies(backwards_match, 0);
1341 printk("\nthe %s-irq-unsafe lock's dependencies:\n", irqclass);
1342 print_lock_dependencies(forwards_match, 0);
1344 printk("\nstack backtrace:\n");
1351 check_usage(struct task_struct *curr, struct held_lock *prev,
1352 struct held_lock *next, enum lock_usage_bit bit_backwards,
1353 enum lock_usage_bit bit_forwards, const char *irqclass)
1357 find_usage_bit = bit_backwards;
1358 /* fills in <backwards_match> */
1359 ret = find_usage_backwards(hlock_class(prev), 0);
1360 if (!ret || ret == 1)
1363 find_usage_bit = bit_forwards;
1364 ret = find_usage_forwards(hlock_class(next), 0);
1365 if (!ret || ret == 1)
1368 return print_bad_irq_dependency(curr, prev, next,
1369 bit_backwards, bit_forwards, irqclass);
1372 static const char *state_names[] = {
1373 #define LOCKDEP_STATE(__STATE) \
1374 __stringify(__STATE),
1375 #include "lockdep_states.h"
1376 #undef LOCKDEP_STATE
1379 static const char *state_rnames[] = {
1380 #define LOCKDEP_STATE(__STATE) \
1381 __stringify(__STATE)"-READ",
1382 #include "lockdep_states.h"
1383 #undef LOCKDEP_STATE
1386 static inline const char *state_name(enum lock_usage_bit bit)
1388 return (bit & 1) ? state_rnames[bit >> 2] : state_names[bit >> 2];
1391 static int exclusive_bit(int new_bit)
1399 * bit 0 - write/read
1400 * bit 1 - used_in/enabled
1404 int state = new_bit & ~3;
1405 int dir = new_bit & 2;
1408 * keep state, bit flip the direction and strip read.
1410 return state | (dir ^ 2);
1413 static int check_irq_usage(struct task_struct *curr, struct held_lock *prev,
1414 struct held_lock *next, enum lock_usage_bit bit)
1417 * Prove that the new dependency does not connect a hardirq-safe
1418 * lock with a hardirq-unsafe lock - to achieve this we search
1419 * the backwards-subgraph starting at <prev>, and the
1420 * forwards-subgraph starting at <next>:
1422 if (!check_usage(curr, prev, next, bit,
1423 exclusive_bit(bit), state_name(bit)))
1429 * Prove that the new dependency does not connect a hardirq-safe-read
1430 * lock with a hardirq-unsafe lock - to achieve this we search
1431 * the backwards-subgraph starting at <prev>, and the
1432 * forwards-subgraph starting at <next>:
1434 if (!check_usage(curr, prev, next, bit,
1435 exclusive_bit(bit), state_name(bit)))
1442 check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
1443 struct held_lock *next)
1445 #define LOCKDEP_STATE(__STATE) \
1446 if (!check_irq_usage(curr, prev, next, LOCK_USED_IN_##__STATE)) \
1448 #include "lockdep_states.h"
1449 #undef LOCKDEP_STATE
1454 static void inc_chains(void)
1456 if (current->hardirq_context)
1457 nr_hardirq_chains++;
1459 if (current->softirq_context)
1460 nr_softirq_chains++;
1462 nr_process_chains++;
1469 check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
1470 struct held_lock *next)
1475 static inline void inc_chains(void)
1477 nr_process_chains++;
1483 print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
1484 struct held_lock *next)
1486 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1489 printk("\n=============================================\n");
1490 printk( "[ INFO: possible recursive locking detected ]\n");
1491 print_kernel_version();
1492 printk( "---------------------------------------------\n");
1493 printk("%s/%d is trying to acquire lock:\n",
1494 curr->comm, task_pid_nr(curr));
1496 printk("\nbut task is already holding lock:\n");
1499 printk("\nother info that might help us debug this:\n");
1500 lockdep_print_held_locks(curr);
1502 printk("\nstack backtrace:\n");
1509 * Check whether we are holding such a class already.
1511 * (Note that this has to be done separately, because the graph cannot
1512 * detect such classes of deadlocks.)
1514 * Returns: 0 on deadlock detected, 1 on OK, 2 on recursive read
1517 check_deadlock(struct task_struct *curr, struct held_lock *next,
1518 struct lockdep_map *next_instance, int read)
1520 struct held_lock *prev;
1521 struct held_lock *nest = NULL;
1524 for (i = 0; i < curr->lockdep_depth; i++) {
1525 prev = curr->held_locks + i;
1527 if (prev->instance == next->nest_lock)
1530 if (hlock_class(prev) != hlock_class(next))
1534 * Allow read-after-read recursion of the same
1535 * lock class (i.e. read_lock(lock)+read_lock(lock)):
1537 if ((read == 2) && prev->read)
1541 * We're holding the nest_lock, which serializes this lock's
1542 * nesting behaviour.
1547 return print_deadlock_bug(curr, prev, next);
1553 * There was a chain-cache miss, and we are about to add a new dependency
1554 * to a previous lock. We recursively validate the following rules:
1556 * - would the adding of the <prev> -> <next> dependency create a
1557 * circular dependency in the graph? [== circular deadlock]
1559 * - does the new prev->next dependency connect any hardirq-safe lock
1560 * (in the full backwards-subgraph starting at <prev>) with any
1561 * hardirq-unsafe lock (in the full forwards-subgraph starting at
1562 * <next>)? [== illegal lock inversion with hardirq contexts]
1564 * - does the new prev->next dependency connect any softirq-safe lock
1565 * (in the full backwards-subgraph starting at <prev>) with any
1566 * softirq-unsafe lock (in the full forwards-subgraph starting at
1567 * <next>)? [== illegal lock inversion with softirq contexts]
1569 * any of these scenarios could lead to a deadlock.
1571 * Then if all the validations pass, we add the forwards and backwards
1575 check_prev_add(struct task_struct *curr, struct held_lock *prev,
1576 struct held_lock *next, int distance)
1578 struct lock_list *entry;
1582 * Prove that the new <prev> -> <next> dependency would not
1583 * create a circular dependency in the graph. (We do this by
1584 * forward-recursing into the graph starting at <next>, and
1585 * checking whether we can reach <prev>.)
1587 * We are using global variables to control the recursion, to
1588 * keep the stackframe size of the recursive functions low:
1590 check_source = next;
1591 check_target = prev;
1593 if (check_noncircular(hlock_class(next), 0) == 2)
1594 return print_circular_bug();
1596 if (!check_prev_add_irq(curr, prev, next))
1600 * For recursive read-locks we do all the dependency checks,
1601 * but we dont store read-triggered dependencies (only
1602 * write-triggered dependencies). This ensures that only the
1603 * write-side dependencies matter, and that if for example a
1604 * write-lock never takes any other locks, then the reads are
1605 * equivalent to a NOP.
1607 if (next->read == 2 || prev->read == 2)
1610 * Is the <prev> -> <next> dependency already present?
1612 * (this may occur even though this is a new chain: consider
1613 * e.g. the L1 -> L2 -> L3 -> L4 and the L5 -> L1 -> L2 -> L3
1614 * chains - the second one will be new, but L1 already has
1615 * L2 added to its dependency list, due to the first chain.)
1617 list_for_each_entry(entry, &hlock_class(prev)->locks_after, entry) {
1618 if (entry->class == hlock_class(next)) {
1620 entry->distance = 1;
1626 * Ok, all validations passed, add the new lock
1627 * to the previous lock's dependency list:
1629 ret = add_lock_to_list(hlock_class(prev), hlock_class(next),
1630 &hlock_class(prev)->locks_after,
1631 next->acquire_ip, distance);
1636 ret = add_lock_to_list(hlock_class(next), hlock_class(prev),
1637 &hlock_class(next)->locks_before,
1638 next->acquire_ip, distance);
1643 * Debugging printouts:
1645 if (verbose(hlock_class(prev)) || verbose(hlock_class(next))) {
1647 printk("\n new dependency: ");
1648 print_lock_name(hlock_class(prev));
1650 print_lock_name(hlock_class(next));
1653 return graph_lock();
1659 * Add the dependency to all directly-previous locks that are 'relevant'.
1660 * The ones that are relevant are (in increasing distance from curr):
1661 * all consecutive trylock entries and the final non-trylock entry - or
1662 * the end of this context's lock-chain - whichever comes first.
1665 check_prevs_add(struct task_struct *curr, struct held_lock *next)
1667 int depth = curr->lockdep_depth;
1668 struct held_lock *hlock;
1673 * Depth must not be zero for a non-head lock:
1678 * At least two relevant locks must exist for this
1681 if (curr->held_locks[depth].irq_context !=
1682 curr->held_locks[depth-1].irq_context)
1686 int distance = curr->lockdep_depth - depth + 1;
1687 hlock = curr->held_locks + depth-1;
1689 * Only non-recursive-read entries get new dependencies
1692 if (hlock->read != 2) {
1693 if (!check_prev_add(curr, hlock, next, distance))
1696 * Stop after the first non-trylock entry,
1697 * as non-trylock entries have added their
1698 * own direct dependencies already, so this
1699 * lock is connected to them indirectly:
1701 if (!hlock->trylock)
1706 * End of lock-stack?
1711 * Stop the search if we cross into another context:
1713 if (curr->held_locks[depth].irq_context !=
1714 curr->held_locks[depth-1].irq_context)
1719 if (!debug_locks_off_graph_unlock())
1727 unsigned long nr_lock_chains;
1728 struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
1729 int nr_chain_hlocks;
1730 static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
1732 struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
1734 return lock_classes + chain_hlocks[chain->base + i];
1738 * Look up a dependency chain. If the key is not present yet then
1739 * add it and return 1 - in this case the new dependency chain is
1740 * validated. If the key is already hashed, return 0.
1741 * (On return with 1 graph_lock is held.)
1743 static inline int lookup_chain_cache(struct task_struct *curr,
1744 struct held_lock *hlock,
1747 struct lock_class *class = hlock_class(hlock);
1748 struct list_head *hash_head = chainhashentry(chain_key);
1749 struct lock_chain *chain;
1750 struct held_lock *hlock_curr, *hlock_next;
1753 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
1756 * We can walk it lock-free, because entries only get added
1759 list_for_each_entry(chain, hash_head, entry) {
1760 if (chain->chain_key == chain_key) {
1762 debug_atomic_inc(&chain_lookup_hits);
1763 if (very_verbose(class))
1764 printk("\nhash chain already cached, key: "
1765 "%016Lx tail class: [%p] %s\n",
1766 (unsigned long long)chain_key,
1767 class->key, class->name);
1771 if (very_verbose(class))
1772 printk("\nnew hash chain, key: %016Lx tail class: [%p] %s\n",
1773 (unsigned long long)chain_key, class->key, class->name);
1775 * Allocate a new chain entry from the static array, and add
1781 * We have to walk the chain again locked - to avoid duplicates:
1783 list_for_each_entry(chain, hash_head, entry) {
1784 if (chain->chain_key == chain_key) {
1789 if (unlikely(nr_lock_chains >= MAX_LOCKDEP_CHAINS)) {
1790 if (!debug_locks_off_graph_unlock())
1793 printk("BUG: MAX_LOCKDEP_CHAINS too low!\n");
1794 printk("turning off the locking correctness validator.\n");
1798 chain = lock_chains + nr_lock_chains++;
1799 chain->chain_key = chain_key;
1800 chain->irq_context = hlock->irq_context;
1801 /* Find the first held_lock of current chain */
1803 for (i = curr->lockdep_depth - 1; i >= 0; i--) {
1804 hlock_curr = curr->held_locks + i;
1805 if (hlock_curr->irq_context != hlock_next->irq_context)
1810 chain->depth = curr->lockdep_depth + 1 - i;
1811 cn = nr_chain_hlocks;
1812 while (cn + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS) {
1813 n = cmpxchg(&nr_chain_hlocks, cn, cn + chain->depth);
1818 if (likely(cn + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) {
1820 for (j = 0; j < chain->depth - 1; j++, i++) {
1821 int lock_id = curr->held_locks[i].class_idx - 1;
1822 chain_hlocks[chain->base + j] = lock_id;
1824 chain_hlocks[chain->base + j] = class - lock_classes;
1826 list_add_tail_rcu(&chain->entry, hash_head);
1827 debug_atomic_inc(&chain_lookup_misses);
1833 static int validate_chain(struct task_struct *curr, struct lockdep_map *lock,
1834 struct held_lock *hlock, int chain_head, u64 chain_key)
1837 * Trylock needs to maintain the stack of held locks, but it
1838 * does not add new dependencies, because trylock can be done
1841 * We look up the chain_key and do the O(N^2) check and update of
1842 * the dependencies only if this is a new dependency chain.
1843 * (If lookup_chain_cache() returns with 1 it acquires
1844 * graph_lock for us)
1846 if (!hlock->trylock && (hlock->check == 2) &&
1847 lookup_chain_cache(curr, hlock, chain_key)) {
1849 * Check whether last held lock:
1851 * - is irq-safe, if this lock is irq-unsafe
1852 * - is softirq-safe, if this lock is hardirq-unsafe
1854 * And check whether the new lock's dependency graph
1855 * could lead back to the previous lock.
1857 * any of these scenarios could lead to a deadlock. If
1860 int ret = check_deadlock(curr, hlock, lock, hlock->read);
1865 * Mark recursive read, as we jump over it when
1866 * building dependencies (just like we jump over
1872 * Add dependency only if this lock is not the head
1873 * of the chain, and if it's not a secondary read-lock:
1875 if (!chain_head && ret != 2)
1876 if (!check_prevs_add(curr, hlock))
1880 /* after lookup_chain_cache(): */
1881 if (unlikely(!debug_locks))
1887 static inline int validate_chain(struct task_struct *curr,
1888 struct lockdep_map *lock, struct held_lock *hlock,
1889 int chain_head, u64 chain_key)
1896 * We are building curr_chain_key incrementally, so double-check
1897 * it from scratch, to make sure that it's done correctly:
1899 static void check_chain_key(struct task_struct *curr)
1901 #ifdef CONFIG_DEBUG_LOCKDEP
1902 struct held_lock *hlock, *prev_hlock = NULL;
1906 for (i = 0; i < curr->lockdep_depth; i++) {
1907 hlock = curr->held_locks + i;
1908 if (chain_key != hlock->prev_chain_key) {
1910 WARN(1, "hm#1, depth: %u [%u], %016Lx != %016Lx\n",
1911 curr->lockdep_depth, i,
1912 (unsigned long long)chain_key,
1913 (unsigned long long)hlock->prev_chain_key);
1916 id = hlock->class_idx - 1;
1917 if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
1920 if (prev_hlock && (prev_hlock->irq_context !=
1921 hlock->irq_context))
1923 chain_key = iterate_chain_key(chain_key, id);
1926 if (chain_key != curr->curr_chain_key) {
1928 WARN(1, "hm#2, depth: %u [%u], %016Lx != %016Lx\n",
1929 curr->lockdep_depth, i,
1930 (unsigned long long)chain_key,
1931 (unsigned long long)curr->curr_chain_key);
1937 print_usage_bug(struct task_struct *curr, struct held_lock *this,
1938 enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
1940 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1943 printk("\n=================================\n");
1944 printk( "[ INFO: inconsistent lock state ]\n");
1945 print_kernel_version();
1946 printk( "---------------------------------\n");
1948 printk("inconsistent {%s} -> {%s} usage.\n",
1949 usage_str[prev_bit], usage_str[new_bit]);
1951 printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] takes:\n",
1952 curr->comm, task_pid_nr(curr),
1953 trace_hardirq_context(curr), hardirq_count() >> HARDIRQ_SHIFT,
1954 trace_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT,
1955 trace_hardirqs_enabled(curr),
1956 trace_softirqs_enabled(curr));
1959 printk("{%s} state was registered at:\n", usage_str[prev_bit]);
1960 print_stack_trace(hlock_class(this)->usage_traces + prev_bit, 1);
1962 print_irqtrace_events(curr);
1963 printk("\nother info that might help us debug this:\n");
1964 lockdep_print_held_locks(curr);
1966 printk("\nstack backtrace:\n");
1973 * Print out an error if an invalid bit is set:
1976 valid_state(struct task_struct *curr, struct held_lock *this,
1977 enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit)
1979 if (unlikely(hlock_class(this)->usage_mask & (1 << bad_bit)))
1980 return print_usage_bug(curr, this, bad_bit, new_bit);
1984 static int mark_lock(struct task_struct *curr, struct held_lock *this,
1985 enum lock_usage_bit new_bit);
1987 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
1990 * print irq inversion bug:
1993 print_irq_inversion_bug(struct task_struct *curr, struct lock_class *other,
1994 struct held_lock *this, int forwards,
1995 const char *irqclass)
1997 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2000 printk("\n=========================================================\n");
2001 printk( "[ INFO: possible irq lock inversion dependency detected ]\n");
2002 print_kernel_version();
2003 printk( "---------------------------------------------------------\n");
2004 printk("%s/%d just changed the state of lock:\n",
2005 curr->comm, task_pid_nr(curr));
2008 printk("but this lock took another, %s-unsafe lock in the past:\n", irqclass);
2010 printk("but this lock was taken by another, %s-safe lock in the past:\n", irqclass);
2011 print_lock_name(other);
2012 printk("\n\nand interrupts could create inverse lock ordering between them.\n\n");
2014 printk("\nother info that might help us debug this:\n");
2015 lockdep_print_held_locks(curr);
2017 printk("\nthe first lock's dependencies:\n");
2018 print_lock_dependencies(hlock_class(this), 0);
2020 printk("\nthe second lock's dependencies:\n");
2021 print_lock_dependencies(other, 0);
2023 printk("\nstack backtrace:\n");
2030 * Prove that in the forwards-direction subgraph starting at <this>
2031 * there is no lock matching <mask>:
2034 check_usage_forwards(struct task_struct *curr, struct held_lock *this,
2035 enum lock_usage_bit bit, const char *irqclass)
2039 find_usage_bit = bit;
2040 /* fills in <forwards_match> */
2041 ret = find_usage_forwards(hlock_class(this), 0);
2042 if (!ret || ret == 1)
2045 return print_irq_inversion_bug(curr, forwards_match, this, 1, irqclass);
2049 * Prove that in the backwards-direction subgraph starting at <this>
2050 * there is no lock matching <mask>:
2053 check_usage_backwards(struct task_struct *curr, struct held_lock *this,
2054 enum lock_usage_bit bit, const char *irqclass)
2058 find_usage_bit = bit;
2059 /* fills in <backwards_match> */
2060 ret = find_usage_backwards(hlock_class(this), 0);
2061 if (!ret || ret == 1)
2064 return print_irq_inversion_bug(curr, backwards_match, this, 0, irqclass);
2067 void print_irqtrace_events(struct task_struct *curr)
2069 printk("irq event stamp: %u\n", curr->irq_events);
2070 printk("hardirqs last enabled at (%u): ", curr->hardirq_enable_event);
2071 print_ip_sym(curr->hardirq_enable_ip);
2072 printk("hardirqs last disabled at (%u): ", curr->hardirq_disable_event);
2073 print_ip_sym(curr->hardirq_disable_ip);
2074 printk("softirqs last enabled at (%u): ", curr->softirq_enable_event);
2075 print_ip_sym(curr->softirq_enable_ip);
2076 printk("softirqs last disabled at (%u): ", curr->softirq_disable_event);
2077 print_ip_sym(curr->softirq_disable_ip);
2080 static int HARDIRQ_verbose(struct lock_class *class)
2083 return class_filter(class);
2088 static int SOFTIRQ_verbose(struct lock_class *class)
2091 return class_filter(class);
2096 static int RECLAIM_FS_verbose(struct lock_class *class)
2099 return class_filter(class);
2104 #define STRICT_READ_CHECKS 1
2106 static int (*state_verbose_f[])(struct lock_class *class) = {
2107 #define LOCKDEP_STATE(__STATE) \
2109 #include "lockdep_states.h"
2110 #undef LOCKDEP_STATE
2113 static inline int state_verbose(enum lock_usage_bit bit,
2114 struct lock_class *class)
2116 return state_verbose_f[bit >> 2](class);
2119 typedef int (*check_usage_f)(struct task_struct *, struct held_lock *,
2120 enum lock_usage_bit bit, const char *name);
2123 mark_lock_irq(struct task_struct *curr, struct held_lock *this,
2124 enum lock_usage_bit new_bit)
2126 int excl_bit = exclusive_bit(new_bit);
2127 int read = new_bit & 1;
2128 int dir = new_bit & 2;
2131 * mark USED_IN has to look forwards -- to ensure no dependency
2132 * has ENABLED state, which would allow recursion deadlocks.
2134 * mark ENABLED has to look backwards -- to ensure no dependee
2135 * has USED_IN state, which, again, would allow recursion deadlocks.
2137 check_usage_f usage = dir ?
2138 check_usage_backwards : check_usage_forwards;
2141 * Validate that this particular lock does not have conflicting
2144 if (!valid_state(curr, this, new_bit, excl_bit))
2148 * Validate that the lock dependencies don't have conflicting usage
2151 if ((!read || !dir || STRICT_READ_CHECKS) &&
2152 !usage(curr, this, excl_bit, state_name(new_bit & ~1)))
2156 * Check for read in write conflicts
2159 if (!valid_state(curr, this, new_bit, excl_bit + 1))
2162 if (STRICT_READ_CHECKS &&
2163 !usage(curr, this, excl_bit + 1,
2164 state_name(new_bit + 1)))
2168 if (state_verbose(new_bit, hlock_class(this)))
2175 #define LOCKDEP_STATE(__STATE) __STATE,
2176 #include "lockdep_states.h"
2177 #undef LOCKDEP_STATE
2181 * Mark all held locks with a usage bit:
2184 mark_held_locks(struct task_struct *curr, enum mark_type mark)
2186 enum lock_usage_bit usage_bit;
2187 struct held_lock *hlock;
2190 for (i = 0; i < curr->lockdep_depth; i++) {
2191 hlock = curr->held_locks + i;
2193 usage_bit = 2 + (mark << 2); /* ENABLED */
2195 usage_bit += 1; /* READ */
2197 BUG_ON(usage_bit >= LOCK_USAGE_STATES);
2199 if (!mark_lock(curr, hlock, usage_bit))
2207 * Debugging helper: via this flag we know that we are in
2208 * 'early bootup code', and will warn about any invalid irqs-on event:
2210 static int early_boot_irqs_enabled;
2212 void early_boot_irqs_off(void)
2214 early_boot_irqs_enabled = 0;
2217 void early_boot_irqs_on(void)
2219 early_boot_irqs_enabled = 1;
2223 * Hardirqs will be enabled:
2225 void trace_hardirqs_on_caller(unsigned long ip)
2227 struct task_struct *curr = current;
2229 time_hardirqs_on(CALLER_ADDR0, ip);
2231 if (unlikely(!debug_locks || current->lockdep_recursion))
2234 if (DEBUG_LOCKS_WARN_ON(unlikely(!early_boot_irqs_enabled)))
2237 if (unlikely(curr->hardirqs_enabled)) {
2238 debug_atomic_inc(&redundant_hardirqs_on);
2241 /* we'll do an OFF -> ON transition: */
2242 curr->hardirqs_enabled = 1;
2244 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2246 if (DEBUG_LOCKS_WARN_ON(current->hardirq_context))
2249 * We are going to turn hardirqs on, so set the
2250 * usage bit for all held locks:
2252 if (!mark_held_locks(curr, HARDIRQ))
2255 * If we have softirqs enabled, then set the usage
2256 * bit for all held locks. (disabled hardirqs prevented
2257 * this bit from being set before)
2259 if (curr->softirqs_enabled)
2260 if (!mark_held_locks(curr, SOFTIRQ))
2263 curr->hardirq_enable_ip = ip;
2264 curr->hardirq_enable_event = ++curr->irq_events;
2265 debug_atomic_inc(&hardirqs_on_events);
2267 EXPORT_SYMBOL(trace_hardirqs_on_caller);
2269 void trace_hardirqs_on(void)
2271 trace_hardirqs_on_caller(CALLER_ADDR0);
2273 EXPORT_SYMBOL(trace_hardirqs_on);
2276 * Hardirqs were disabled:
2278 void trace_hardirqs_off_caller(unsigned long ip)
2280 struct task_struct *curr = current;
2282 time_hardirqs_off(CALLER_ADDR0, ip);
2284 if (unlikely(!debug_locks || current->lockdep_recursion))
2287 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2290 if (curr->hardirqs_enabled) {
2292 * We have done an ON -> OFF transition:
2294 curr->hardirqs_enabled = 0;
2295 curr->hardirq_disable_ip = ip;
2296 curr->hardirq_disable_event = ++curr->irq_events;
2297 debug_atomic_inc(&hardirqs_off_events);
2299 debug_atomic_inc(&redundant_hardirqs_off);
2301 EXPORT_SYMBOL(trace_hardirqs_off_caller);
2303 void trace_hardirqs_off(void)
2305 trace_hardirqs_off_caller(CALLER_ADDR0);
2307 EXPORT_SYMBOL(trace_hardirqs_off);
2310 * Softirqs will be enabled:
2312 void trace_softirqs_on(unsigned long ip)
2314 struct task_struct *curr = current;
2316 if (unlikely(!debug_locks))
2319 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2322 if (curr->softirqs_enabled) {
2323 debug_atomic_inc(&redundant_softirqs_on);
2328 * We'll do an OFF -> ON transition:
2330 curr->softirqs_enabled = 1;
2331 curr->softirq_enable_ip = ip;
2332 curr->softirq_enable_event = ++curr->irq_events;
2333 debug_atomic_inc(&softirqs_on_events);
2335 * We are going to turn softirqs on, so set the
2336 * usage bit for all held locks, if hardirqs are
2339 if (curr->hardirqs_enabled)
2340 mark_held_locks(curr, SOFTIRQ);
2344 * Softirqs were disabled:
2346 void trace_softirqs_off(unsigned long ip)
2348 struct task_struct *curr = current;
2350 if (unlikely(!debug_locks))
2353 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2356 if (curr->softirqs_enabled) {
2358 * We have done an ON -> OFF transition:
2360 curr->softirqs_enabled = 0;
2361 curr->softirq_disable_ip = ip;
2362 curr->softirq_disable_event = ++curr->irq_events;
2363 debug_atomic_inc(&softirqs_off_events);
2364 DEBUG_LOCKS_WARN_ON(!softirq_count());
2366 debug_atomic_inc(&redundant_softirqs_off);
2369 static void __lockdep_trace_alloc(gfp_t gfp_mask, unsigned long flags)
2371 struct task_struct *curr = current;
2373 if (unlikely(!debug_locks))
2376 /* no reclaim without waiting on it */
2377 if (!(gfp_mask & __GFP_WAIT))
2380 /* this guy won't enter reclaim */
2381 if ((curr->flags & PF_MEMALLOC) && !(gfp_mask & __GFP_NOMEMALLOC))
2384 /* We're only interested __GFP_FS allocations for now */
2385 if (!(gfp_mask & __GFP_FS))
2388 if (DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags)))
2391 mark_held_locks(curr, RECLAIM_FS);
2394 static void check_flags(unsigned long flags);
2396 void lockdep_trace_alloc(gfp_t gfp_mask)
2398 unsigned long flags;
2400 if (unlikely(current->lockdep_recursion))
2403 raw_local_irq_save(flags);
2405 current->lockdep_recursion = 1;
2406 __lockdep_trace_alloc(gfp_mask, flags);
2407 current->lockdep_recursion = 0;
2408 raw_local_irq_restore(flags);
2411 static int mark_irqflags(struct task_struct *curr, struct held_lock *hlock)
2414 * If non-trylock use in a hardirq or softirq context, then
2415 * mark the lock as used in these contexts:
2417 if (!hlock->trylock) {
2419 if (curr->hardirq_context)
2420 if (!mark_lock(curr, hlock,
2421 LOCK_USED_IN_HARDIRQ_READ))
2423 if (curr->softirq_context)
2424 if (!mark_lock(curr, hlock,
2425 LOCK_USED_IN_SOFTIRQ_READ))
2428 if (curr->hardirq_context)
2429 if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ))
2431 if (curr->softirq_context)
2432 if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ))
2436 if (!hlock->hardirqs_off) {
2438 if (!mark_lock(curr, hlock,
2439 LOCK_ENABLED_HARDIRQ_READ))
2441 if (curr->softirqs_enabled)
2442 if (!mark_lock(curr, hlock,
2443 LOCK_ENABLED_SOFTIRQ_READ))
2446 if (!mark_lock(curr, hlock,
2447 LOCK_ENABLED_HARDIRQ))
2449 if (curr->softirqs_enabled)
2450 if (!mark_lock(curr, hlock,
2451 LOCK_ENABLED_SOFTIRQ))
2457 * We reuse the irq context infrastructure more broadly as a general
2458 * context checking code. This tests GFP_FS recursion (a lock taken
2459 * during reclaim for a GFP_FS allocation is held over a GFP_FS
2462 if (!hlock->trylock && (curr->lockdep_reclaim_gfp & __GFP_FS)) {
2464 if (!mark_lock(curr, hlock, LOCK_USED_IN_RECLAIM_FS_READ))
2467 if (!mark_lock(curr, hlock, LOCK_USED_IN_RECLAIM_FS))
2475 static int separate_irq_context(struct task_struct *curr,
2476 struct held_lock *hlock)
2478 unsigned int depth = curr->lockdep_depth;
2481 * Keep track of points where we cross into an interrupt context:
2483 hlock->irq_context = 2*(curr->hardirq_context ? 1 : 0) +
2484 curr->softirq_context;
2486 struct held_lock *prev_hlock;
2488 prev_hlock = curr->held_locks + depth-1;
2490 * If we cross into another context, reset the
2491 * hash key (this also prevents the checking and the
2492 * adding of the dependency to 'prev'):
2494 if (prev_hlock->irq_context != hlock->irq_context)
2503 int mark_lock_irq(struct task_struct *curr, struct held_lock *this,
2504 enum lock_usage_bit new_bit)
2510 static inline int mark_irqflags(struct task_struct *curr,
2511 struct held_lock *hlock)
2516 static inline int separate_irq_context(struct task_struct *curr,
2517 struct held_lock *hlock)
2522 void lockdep_trace_alloc(gfp_t gfp_mask)
2529 * Mark a lock with a usage bit, and validate the state transition:
2531 static int mark_lock(struct task_struct *curr, struct held_lock *this,
2532 enum lock_usage_bit new_bit)
2534 unsigned int new_mask = 1 << new_bit, ret = 1;
2537 * If already set then do not dirty the cacheline,
2538 * nor do any checks:
2540 if (likely(hlock_class(this)->usage_mask & new_mask))
2546 * Make sure we didnt race:
2548 if (unlikely(hlock_class(this)->usage_mask & new_mask)) {
2553 hlock_class(this)->usage_mask |= new_mask;
2555 if (!save_trace(hlock_class(this)->usage_traces + new_bit))
2559 #define LOCKDEP_STATE(__STATE) \
2560 case LOCK_USED_IN_##__STATE: \
2561 case LOCK_USED_IN_##__STATE##_READ: \
2562 case LOCK_ENABLED_##__STATE: \
2563 case LOCK_ENABLED_##__STATE##_READ:
2564 #include "lockdep_states.h"
2565 #undef LOCKDEP_STATE
2566 ret = mark_lock_irq(curr, this, new_bit);
2571 debug_atomic_dec(&nr_unused_locks);
2574 if (!debug_locks_off_graph_unlock())
2583 * We must printk outside of the graph_lock:
2586 printk("\nmarked lock as {%s}:\n", usage_str[new_bit]);
2588 print_irqtrace_events(curr);
2596 * Initialize a lock instance's lock-class mapping info:
2598 void lockdep_init_map(struct lockdep_map *lock, const char *name,
2599 struct lock_class_key *key, int subclass)
2601 lock->class_cache = NULL;
2602 #ifdef CONFIG_LOCK_STAT
2603 lock->cpu = raw_smp_processor_id();
2606 if (DEBUG_LOCKS_WARN_ON(!name)) {
2607 lock->name = "NULL";
2613 if (DEBUG_LOCKS_WARN_ON(!key))
2616 * Sanity check, the lock-class key must be persistent:
2618 if (!static_obj(key)) {
2619 printk("BUG: key %p not in .data!\n", key);
2620 DEBUG_LOCKS_WARN_ON(1);
2625 if (unlikely(!debug_locks))
2629 register_lock_class(lock, subclass, 1);
2631 EXPORT_SYMBOL_GPL(lockdep_init_map);
2634 * This gets called for every mutex_lock*()/spin_lock*() operation.
2635 * We maintain the dependency maps and validate the locking attempt:
2637 static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
2638 int trylock, int read, int check, int hardirqs_off,
2639 struct lockdep_map *nest_lock, unsigned long ip)
2641 struct task_struct *curr = current;
2642 struct lock_class *class = NULL;
2643 struct held_lock *hlock;
2644 unsigned int depth, id;
2651 if (unlikely(!debug_locks))
2654 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2657 if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
2659 printk("BUG: MAX_LOCKDEP_SUBCLASSES too low!\n");
2660 printk("turning off the locking correctness validator.\n");
2666 class = lock->class_cache;
2668 * Not cached yet or subclass?
2670 if (unlikely(!class)) {
2671 class = register_lock_class(lock, subclass, 0);
2675 debug_atomic_inc((atomic_t *)&class->ops);
2676 if (very_verbose(class)) {
2677 printk("\nacquire class [%p] %s", class->key, class->name);
2678 if (class->name_version > 1)
2679 printk("#%d", class->name_version);
2685 * Add the lock to the list of currently held locks.
2686 * (we dont increase the depth just yet, up until the
2687 * dependency checks are done)
2689 depth = curr->lockdep_depth;
2690 if (DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH))
2693 hlock = curr->held_locks + depth;
2694 if (DEBUG_LOCKS_WARN_ON(!class))
2696 hlock->class_idx = class - lock_classes + 1;
2697 hlock->acquire_ip = ip;
2698 hlock->instance = lock;
2699 hlock->nest_lock = nest_lock;
2700 hlock->trylock = trylock;
2702 hlock->check = check;
2703 hlock->hardirqs_off = !!hardirqs_off;
2704 #ifdef CONFIG_LOCK_STAT
2705 hlock->waittime_stamp = 0;
2706 hlock->holdtime_stamp = sched_clock();
2709 if (check == 2 && !mark_irqflags(curr, hlock))
2712 /* mark it as used: */
2713 if (!mark_lock(curr, hlock, LOCK_USED))
2717 * Calculate the chain hash: it's the combined hash of all the
2718 * lock keys along the dependency chain. We save the hash value
2719 * at every step so that we can get the current hash easily
2720 * after unlock. The chain hash is then used to cache dependency
2723 * The 'key ID' is what is the most compact key value to drive
2724 * the hash, not class->key.
2726 id = class - lock_classes;
2727 if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
2730 chain_key = curr->curr_chain_key;
2732 if (DEBUG_LOCKS_WARN_ON(chain_key != 0))
2737 hlock->prev_chain_key = chain_key;
2738 if (separate_irq_context(curr, hlock)) {
2742 chain_key = iterate_chain_key(chain_key, id);
2744 if (!validate_chain(curr, lock, hlock, chain_head, chain_key))
2747 curr->curr_chain_key = chain_key;
2748 curr->lockdep_depth++;
2749 check_chain_key(curr);
2750 #ifdef CONFIG_DEBUG_LOCKDEP
2751 if (unlikely(!debug_locks))
2754 if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
2756 printk("BUG: MAX_LOCK_DEPTH too low!\n");
2757 printk("turning off the locking correctness validator.\n");
2762 if (unlikely(curr->lockdep_depth > max_lockdep_depth))
2763 max_lockdep_depth = curr->lockdep_depth;
2769 print_unlock_inbalance_bug(struct task_struct *curr, struct lockdep_map *lock,
2772 if (!debug_locks_off())
2774 if (debug_locks_silent)
2777 printk("\n=====================================\n");
2778 printk( "[ BUG: bad unlock balance detected! ]\n");
2779 printk( "-------------------------------------\n");
2780 printk("%s/%d is trying to release lock (",
2781 curr->comm, task_pid_nr(curr));
2782 print_lockdep_cache(lock);
2785 printk("but there are no more locks to release!\n");
2786 printk("\nother info that might help us debug this:\n");
2787 lockdep_print_held_locks(curr);
2789 printk("\nstack backtrace:\n");
2796 * Common debugging checks for both nested and non-nested unlock:
2798 static int check_unlock(struct task_struct *curr, struct lockdep_map *lock,
2801 if (unlikely(!debug_locks))
2803 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2806 if (curr->lockdep_depth <= 0)
2807 return print_unlock_inbalance_bug(curr, lock, ip);
2813 __lock_set_class(struct lockdep_map *lock, const char *name,
2814 struct lock_class_key *key, unsigned int subclass,
2817 struct task_struct *curr = current;
2818 struct held_lock *hlock, *prev_hlock;
2819 struct lock_class *class;
2823 depth = curr->lockdep_depth;
2824 if (DEBUG_LOCKS_WARN_ON(!depth))
2828 for (i = depth-1; i >= 0; i--) {
2829 hlock = curr->held_locks + i;
2831 * We must not cross into another context:
2833 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
2835 if (hlock->instance == lock)
2839 return print_unlock_inbalance_bug(curr, lock, ip);
2842 lockdep_init_map(lock, name, key, 0);
2843 class = register_lock_class(lock, subclass, 0);
2844 hlock->class_idx = class - lock_classes + 1;
2846 curr->lockdep_depth = i;
2847 curr->curr_chain_key = hlock->prev_chain_key;
2849 for (; i < depth; i++) {
2850 hlock = curr->held_locks + i;
2851 if (!__lock_acquire(hlock->instance,
2852 hlock_class(hlock)->subclass, hlock->trylock,
2853 hlock->read, hlock->check, hlock->hardirqs_off,
2854 hlock->nest_lock, hlock->acquire_ip))
2858 if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth))
2864 * Remove the lock to the list of currently held locks in a
2865 * potentially non-nested (out of order) manner. This is a
2866 * relatively rare operation, as all the unlock APIs default
2867 * to nested mode (which uses lock_release()):
2870 lock_release_non_nested(struct task_struct *curr,
2871 struct lockdep_map *lock, unsigned long ip)
2873 struct held_lock *hlock, *prev_hlock;
2878 * Check whether the lock exists in the current stack
2881 depth = curr->lockdep_depth;
2882 if (DEBUG_LOCKS_WARN_ON(!depth))
2886 for (i = depth-1; i >= 0; i--) {
2887 hlock = curr->held_locks + i;
2889 * We must not cross into another context:
2891 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
2893 if (hlock->instance == lock)
2897 return print_unlock_inbalance_bug(curr, lock, ip);
2900 lock_release_holdtime(hlock);
2903 * We have the right lock to unlock, 'hlock' points to it.
2904 * Now we remove it from the stack, and add back the other
2905 * entries (if any), recalculating the hash along the way:
2907 curr->lockdep_depth = i;
2908 curr->curr_chain_key = hlock->prev_chain_key;
2910 for (i++; i < depth; i++) {
2911 hlock = curr->held_locks + i;
2912 if (!__lock_acquire(hlock->instance,
2913 hlock_class(hlock)->subclass, hlock->trylock,
2914 hlock->read, hlock->check, hlock->hardirqs_off,
2915 hlock->nest_lock, hlock->acquire_ip))
2919 if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - 1))
2925 * Remove the lock to the list of currently held locks - this gets
2926 * called on mutex_unlock()/spin_unlock*() (or on a failed
2927 * mutex_lock_interruptible()). This is done for unlocks that nest
2928 * perfectly. (i.e. the current top of the lock-stack is unlocked)
2930 static int lock_release_nested(struct task_struct *curr,
2931 struct lockdep_map *lock, unsigned long ip)
2933 struct held_lock *hlock;
2937 * Pop off the top of the lock stack:
2939 depth = curr->lockdep_depth - 1;
2940 hlock = curr->held_locks + depth;
2943 * Is the unlock non-nested:
2945 if (hlock->instance != lock)
2946 return lock_release_non_nested(curr, lock, ip);
2947 curr->lockdep_depth--;
2949 if (DEBUG_LOCKS_WARN_ON(!depth && (hlock->prev_chain_key != 0)))
2952 curr->curr_chain_key = hlock->prev_chain_key;
2954 lock_release_holdtime(hlock);
2956 #ifdef CONFIG_DEBUG_LOCKDEP
2957 hlock->prev_chain_key = 0;
2958 hlock->class_idx = 0;
2959 hlock->acquire_ip = 0;
2960 hlock->irq_context = 0;
2966 * Remove the lock to the list of currently held locks - this gets
2967 * called on mutex_unlock()/spin_unlock*() (or on a failed
2968 * mutex_lock_interruptible()). This is done for unlocks that nest
2969 * perfectly. (i.e. the current top of the lock-stack is unlocked)
2972 __lock_release(struct lockdep_map *lock, int nested, unsigned long ip)
2974 struct task_struct *curr = current;
2976 if (!check_unlock(curr, lock, ip))
2980 if (!lock_release_nested(curr, lock, ip))
2983 if (!lock_release_non_nested(curr, lock, ip))
2987 check_chain_key(curr);
2991 * Check whether we follow the irq-flags state precisely:
2993 static void check_flags(unsigned long flags)
2995 #if defined(CONFIG_PROVE_LOCKING) && defined(CONFIG_DEBUG_LOCKDEP) && \
2996 defined(CONFIG_TRACE_IRQFLAGS)
3000 if (irqs_disabled_flags(flags)) {
3001 if (DEBUG_LOCKS_WARN_ON(current->hardirqs_enabled)) {
3002 printk("possible reason: unannotated irqs-off.\n");
3005 if (DEBUG_LOCKS_WARN_ON(!current->hardirqs_enabled)) {
3006 printk("possible reason: unannotated irqs-on.\n");
3011 * We dont accurately track softirq state in e.g.
3012 * hardirq contexts (such as on 4KSTACKS), so only
3013 * check if not in hardirq contexts:
3015 if (!hardirq_count()) {
3016 if (softirq_count())
3017 DEBUG_LOCKS_WARN_ON(current->softirqs_enabled);
3019 DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled);
3023 print_irqtrace_events(current);
3027 void lock_set_class(struct lockdep_map *lock, const char *name,
3028 struct lock_class_key *key, unsigned int subclass,
3031 unsigned long flags;
3033 if (unlikely(current->lockdep_recursion))
3036 raw_local_irq_save(flags);
3037 current->lockdep_recursion = 1;
3039 if (__lock_set_class(lock, name, key, subclass, ip))
3040 check_chain_key(current);
3041 current->lockdep_recursion = 0;
3042 raw_local_irq_restore(flags);
3044 EXPORT_SYMBOL_GPL(lock_set_class);
3047 * We are not always called with irqs disabled - do that here,
3048 * and also avoid lockdep recursion:
3050 void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
3051 int trylock, int read, int check,
3052 struct lockdep_map *nest_lock, unsigned long ip)
3054 unsigned long flags;
3056 trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip);
3058 if (unlikely(current->lockdep_recursion))
3061 raw_local_irq_save(flags);
3064 current->lockdep_recursion = 1;
3065 __lock_acquire(lock, subclass, trylock, read, check,
3066 irqs_disabled_flags(flags), nest_lock, ip);
3067 current->lockdep_recursion = 0;
3068 raw_local_irq_restore(flags);
3070 EXPORT_SYMBOL_GPL(lock_acquire);
3072 void lock_release(struct lockdep_map *lock, int nested,
3075 unsigned long flags;
3077 trace_lock_release(lock, nested, ip);
3079 if (unlikely(current->lockdep_recursion))
3082 raw_local_irq_save(flags);
3084 current->lockdep_recursion = 1;
3085 __lock_release(lock, nested, ip);
3086 current->lockdep_recursion = 0;
3087 raw_local_irq_restore(flags);
3089 EXPORT_SYMBOL_GPL(lock_release);
3091 void lockdep_set_current_reclaim_state(gfp_t gfp_mask)
3093 current->lockdep_reclaim_gfp = gfp_mask;
3096 void lockdep_clear_current_reclaim_state(void)
3098 current->lockdep_reclaim_gfp = 0;
3101 #ifdef CONFIG_LOCK_STAT
3103 print_lock_contention_bug(struct task_struct *curr, struct lockdep_map *lock,
3106 if (!debug_locks_off())
3108 if (debug_locks_silent)
3111 printk("\n=================================\n");
3112 printk( "[ BUG: bad contention detected! ]\n");
3113 printk( "---------------------------------\n");
3114 printk("%s/%d is trying to contend lock (",
3115 curr->comm, task_pid_nr(curr));
3116 print_lockdep_cache(lock);
3119 printk("but there are no locks held!\n");
3120 printk("\nother info that might help us debug this:\n");
3121 lockdep_print_held_locks(curr);
3123 printk("\nstack backtrace:\n");
3130 __lock_contended(struct lockdep_map *lock, unsigned long ip)
3132 struct task_struct *curr = current;
3133 struct held_lock *hlock, *prev_hlock;
3134 struct lock_class_stats *stats;
3136 int i, contention_point, contending_point;
3138 depth = curr->lockdep_depth;
3139 if (DEBUG_LOCKS_WARN_ON(!depth))
3143 for (i = depth-1; i >= 0; i--) {
3144 hlock = curr->held_locks + i;
3146 * We must not cross into another context:
3148 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3150 if (hlock->instance == lock)
3154 print_lock_contention_bug(curr, lock, ip);
3158 hlock->waittime_stamp = sched_clock();
3160 contention_point = lock_point(hlock_class(hlock)->contention_point, ip);
3161 contending_point = lock_point(hlock_class(hlock)->contending_point,
3164 stats = get_lock_stats(hlock_class(hlock));
3165 if (contention_point < LOCKSTAT_POINTS)
3166 stats->contention_point[contention_point]++;
3167 if (contending_point < LOCKSTAT_POINTS)
3168 stats->contending_point[contending_point]++;
3169 if (lock->cpu != smp_processor_id())
3170 stats->bounces[bounce_contended + !!hlock->read]++;
3171 put_lock_stats(stats);
3175 __lock_acquired(struct lockdep_map *lock, unsigned long ip)
3177 struct task_struct *curr = current;
3178 struct held_lock *hlock, *prev_hlock;
3179 struct lock_class_stats *stats;
3185 depth = curr->lockdep_depth;
3186 if (DEBUG_LOCKS_WARN_ON(!depth))
3190 for (i = depth-1; i >= 0; i--) {
3191 hlock = curr->held_locks + i;
3193 * We must not cross into another context:
3195 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3197 if (hlock->instance == lock)
3201 print_lock_contention_bug(curr, lock, _RET_IP_);
3205 cpu = smp_processor_id();
3206 if (hlock->waittime_stamp) {
3207 now = sched_clock();
3208 waittime = now - hlock->waittime_stamp;
3209 hlock->holdtime_stamp = now;
3212 trace_lock_acquired(lock, ip, waittime);
3214 stats = get_lock_stats(hlock_class(hlock));
3217 lock_time_inc(&stats->read_waittime, waittime);
3219 lock_time_inc(&stats->write_waittime, waittime);
3221 if (lock->cpu != cpu)
3222 stats->bounces[bounce_acquired + !!hlock->read]++;
3223 put_lock_stats(stats);
3229 void lock_contended(struct lockdep_map *lock, unsigned long ip)
3231 unsigned long flags;
3233 trace_lock_contended(lock, ip);
3235 if (unlikely(!lock_stat))
3238 if (unlikely(current->lockdep_recursion))
3241 raw_local_irq_save(flags);
3243 current->lockdep_recursion = 1;
3244 __lock_contended(lock, ip);
3245 current->lockdep_recursion = 0;
3246 raw_local_irq_restore(flags);
3248 EXPORT_SYMBOL_GPL(lock_contended);
3250 void lock_acquired(struct lockdep_map *lock, unsigned long ip)
3252 unsigned long flags;
3254 if (unlikely(!lock_stat))
3257 if (unlikely(current->lockdep_recursion))
3260 raw_local_irq_save(flags);
3262 current->lockdep_recursion = 1;
3263 __lock_acquired(lock, ip);
3264 current->lockdep_recursion = 0;
3265 raw_local_irq_restore(flags);
3267 EXPORT_SYMBOL_GPL(lock_acquired);
3271 * Used by the testsuite, sanitize the validator state
3272 * after a simulated failure:
3275 void lockdep_reset(void)
3277 unsigned long flags;
3280 raw_local_irq_save(flags);
3281 current->curr_chain_key = 0;
3282 current->lockdep_depth = 0;
3283 current->lockdep_recursion = 0;
3284 memset(current->held_locks, 0, MAX_LOCK_DEPTH*sizeof(struct held_lock));
3285 nr_hardirq_chains = 0;
3286 nr_softirq_chains = 0;
3287 nr_process_chains = 0;
3289 for (i = 0; i < CHAINHASH_SIZE; i++)
3290 INIT_LIST_HEAD(chainhash_table + i);
3291 raw_local_irq_restore(flags);
3294 static void zap_class(struct lock_class *class)
3299 * Remove all dependencies this lock is
3302 for (i = 0; i < nr_list_entries; i++) {
3303 if (list_entries[i].class == class)
3304 list_del_rcu(&list_entries[i].entry);
3307 * Unhash the class and remove it from the all_lock_classes list:
3309 list_del_rcu(&class->hash_entry);
3310 list_del_rcu(&class->lock_entry);
3315 static inline int within(const void *addr, void *start, unsigned long size)
3317 return addr >= start && addr < start + size;
3320 void lockdep_free_key_range(void *start, unsigned long size)
3322 struct lock_class *class, *next;
3323 struct list_head *head;
3324 unsigned long flags;
3328 raw_local_irq_save(flags);
3329 locked = graph_lock();
3332 * Unhash all classes that were created by this module:
3334 for (i = 0; i < CLASSHASH_SIZE; i++) {
3335 head = classhash_table + i;
3336 if (list_empty(head))
3338 list_for_each_entry_safe(class, next, head, hash_entry) {
3339 if (within(class->key, start, size))
3341 else if (within(class->name, start, size))
3348 raw_local_irq_restore(flags);
3351 void lockdep_reset_lock(struct lockdep_map *lock)
3353 struct lock_class *class, *next;
3354 struct list_head *head;
3355 unsigned long flags;
3359 raw_local_irq_save(flags);
3362 * Remove all classes this lock might have:
3364 for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) {
3366 * If the class exists we look it up and zap it:
3368 class = look_up_lock_class(lock, j);
3373 * Debug check: in the end all mapped classes should
3376 locked = graph_lock();
3377 for (i = 0; i < CLASSHASH_SIZE; i++) {
3378 head = classhash_table + i;
3379 if (list_empty(head))
3381 list_for_each_entry_safe(class, next, head, hash_entry) {
3382 if (unlikely(class == lock->class_cache)) {
3383 if (debug_locks_off_graph_unlock())
3393 raw_local_irq_restore(flags);
3396 void lockdep_init(void)
3401 * Some architectures have their own start_kernel()
3402 * code which calls lockdep_init(), while we also
3403 * call lockdep_init() from the start_kernel() itself,
3404 * and we want to initialize the hashes only once:
3406 if (lockdep_initialized)
3409 for (i = 0; i < CLASSHASH_SIZE; i++)
3410 INIT_LIST_HEAD(classhash_table + i);
3412 for (i = 0; i < CHAINHASH_SIZE; i++)
3413 INIT_LIST_HEAD(chainhash_table + i);
3415 lockdep_initialized = 1;
3418 void __init lockdep_info(void)
3420 printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");
3422 printk("... MAX_LOCKDEP_SUBCLASSES: %lu\n", MAX_LOCKDEP_SUBCLASSES);
3423 printk("... MAX_LOCK_DEPTH: %lu\n", MAX_LOCK_DEPTH);
3424 printk("... MAX_LOCKDEP_KEYS: %lu\n", MAX_LOCKDEP_KEYS);
3425 printk("... CLASSHASH_SIZE: %lu\n", CLASSHASH_SIZE);
3426 printk("... MAX_LOCKDEP_ENTRIES: %lu\n", MAX_LOCKDEP_ENTRIES);
3427 printk("... MAX_LOCKDEP_CHAINS: %lu\n", MAX_LOCKDEP_CHAINS);
3428 printk("... CHAINHASH_SIZE: %lu\n", CHAINHASH_SIZE);
3430 printk(" memory used by lock dependency info: %lu kB\n",
3431 (sizeof(struct lock_class) * MAX_LOCKDEP_KEYS +
3432 sizeof(struct list_head) * CLASSHASH_SIZE +
3433 sizeof(struct lock_list) * MAX_LOCKDEP_ENTRIES +
3434 sizeof(struct lock_chain) * MAX_LOCKDEP_CHAINS +
3435 sizeof(struct list_head) * CHAINHASH_SIZE) / 1024);
3437 printk(" per task-struct memory footprint: %lu bytes\n",
3438 sizeof(struct held_lock) * MAX_LOCK_DEPTH);
3440 #ifdef CONFIG_DEBUG_LOCKDEP
3441 if (lockdep_init_error) {
3442 printk("WARNING: lockdep init error! Arch code didn't call lockdep_init() early enough?\n");
3443 printk("Call stack leading to lockdep invocation was:\n");
3444 print_stack_trace(&lockdep_init_trace, 0);
3450 print_freed_lock_bug(struct task_struct *curr, const void *mem_from,
3451 const void *mem_to, struct held_lock *hlock)
3453 if (!debug_locks_off())
3455 if (debug_locks_silent)
3458 printk("\n=========================\n");
3459 printk( "[ BUG: held lock freed! ]\n");
3460 printk( "-------------------------\n");
3461 printk("%s/%d is freeing memory %p-%p, with a lock still held there!\n",
3462 curr->comm, task_pid_nr(curr), mem_from, mem_to-1);
3464 lockdep_print_held_locks(curr);
3466 printk("\nstack backtrace:\n");
3470 static inline int not_in_range(const void* mem_from, unsigned long mem_len,
3471 const void* lock_from, unsigned long lock_len)
3473 return lock_from + lock_len <= mem_from ||
3474 mem_from + mem_len <= lock_from;
3478 * Called when kernel memory is freed (or unmapped), or if a lock
3479 * is destroyed or reinitialized - this code checks whether there is
3480 * any held lock in the memory range of <from> to <to>:
3482 void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len)
3484 struct task_struct *curr = current;
3485 struct held_lock *hlock;
3486 unsigned long flags;
3489 if (unlikely(!debug_locks))
3492 local_irq_save(flags);
3493 for (i = 0; i < curr->lockdep_depth; i++) {
3494 hlock = curr->held_locks + i;
3496 if (not_in_range(mem_from, mem_len, hlock->instance,
3497 sizeof(*hlock->instance)))
3500 print_freed_lock_bug(curr, mem_from, mem_from + mem_len, hlock);
3503 local_irq_restore(flags);
3505 EXPORT_SYMBOL_GPL(debug_check_no_locks_freed);
3507 static void print_held_locks_bug(struct task_struct *curr)
3509 if (!debug_locks_off())
3511 if (debug_locks_silent)
3514 printk("\n=====================================\n");
3515 printk( "[ BUG: lock held at task exit time! ]\n");
3516 printk( "-------------------------------------\n");
3517 printk("%s/%d is exiting with locks still held!\n",
3518 curr->comm, task_pid_nr(curr));
3519 lockdep_print_held_locks(curr);
3521 printk("\nstack backtrace:\n");
3525 void debug_check_no_locks_held(struct task_struct *task)
3527 if (unlikely(task->lockdep_depth > 0))
3528 print_held_locks_bug(task);
3531 void debug_show_all_locks(void)
3533 struct task_struct *g, *p;
3537 if (unlikely(!debug_locks)) {
3538 printk("INFO: lockdep is turned off.\n");
3541 printk("\nShowing all locks held in the system:\n");
3544 * Here we try to get the tasklist_lock as hard as possible,
3545 * if not successful after 2 seconds we ignore it (but keep
3546 * trying). This is to enable a debug printout even if a
3547 * tasklist_lock-holding task deadlocks or crashes.
3550 if (!read_trylock(&tasklist_lock)) {
3552 printk("hm, tasklist_lock locked, retrying... ");
3555 printk(" #%d", 10-count);
3559 printk(" ignoring it.\n");
3563 printk(KERN_CONT " locked it.\n");
3566 do_each_thread(g, p) {
3568 * It's not reliable to print a task's held locks
3569 * if it's not sleeping (or if it's not the current
3572 if (p->state == TASK_RUNNING && p != current)
3574 if (p->lockdep_depth)
3575 lockdep_print_held_locks(p);
3577 if (read_trylock(&tasklist_lock))
3579 } while_each_thread(g, p);
3582 printk("=============================================\n\n");
3585 read_unlock(&tasklist_lock);
3587 EXPORT_SYMBOL_GPL(debug_show_all_locks);
3590 * Careful: only use this function if you are sure that
3591 * the task cannot run in parallel!
3593 void __debug_show_held_locks(struct task_struct *task)
3595 if (unlikely(!debug_locks)) {
3596 printk("INFO: lockdep is turned off.\n");
3599 lockdep_print_held_locks(task);
3601 EXPORT_SYMBOL_GPL(__debug_show_held_locks);
3603 void debug_show_held_locks(struct task_struct *task)
3605 __debug_show_held_locks(task);
3607 EXPORT_SYMBOL_GPL(debug_show_held_locks);
3609 void lockdep_sys_exit(void)
3611 struct task_struct *curr = current;
3613 if (unlikely(curr->lockdep_depth)) {
3614 if (!debug_locks_off())
3616 printk("\n================================================\n");
3617 printk( "[ BUG: lock held when returning to user space! ]\n");
3618 printk( "------------------------------------------------\n");
3619 printk("%s/%d is leaving the kernel with locks still held!\n",
3620 curr->comm, curr->pid);
3621 lockdep_print_held_locks(curr);