1 // SPDX-License-Identifier: GPL-2.0-only
5 * Runtime locking correctness validator
7 * Started by Ingo Molnar:
9 * Copyright (C) 2006,2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
10 * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
12 * this code maps all the lock dependencies as they occur in a live kernel
13 * and will warn about the following classes of locking bugs:
15 * - lock inversion scenarios
16 * - circular lock dependencies
17 * - hardirq/softirq safe/unsafe locking bugs
19 * Bugs are reported even if the current locking scenario does not cause
20 * any deadlock at this point.
22 * I.e. if anytime in the past two locks were taken in a different order,
23 * even if it happened for another task, even if those were different
24 * locks (but of the same class as this lock), this code will detect it.
26 * Thanks to Arjan van de Ven for coming up with the initial idea of
27 * mapping lock dependencies runtime.
29 #define DISABLE_BRANCH_PROFILING
30 #include <linux/mutex.h>
31 #include <linux/sched.h>
32 #include <linux/sched/clock.h>
33 #include <linux/sched/task.h>
34 #include <linux/sched/mm.h>
35 #include <linux/delay.h>
36 #include <linux/module.h>
37 #include <linux/proc_fs.h>
38 #include <linux/seq_file.h>
39 #include <linux/spinlock.h>
40 #include <linux/kallsyms.h>
41 #include <linux/interrupt.h>
42 #include <linux/stacktrace.h>
43 #include <linux/debug_locks.h>
44 #include <linux/irqflags.h>
45 #include <linux/utsname.h>
46 #include <linux/hash.h>
47 #include <linux/ftrace.h>
48 #include <linux/stringify.h>
49 #include <linux/bitmap.h>
50 #include <linux/bitops.h>
51 #include <linux/gfp.h>
52 #include <linux/random.h>
53 #include <linux/jhash.h>
54 #include <linux/nmi.h>
55 #include <linux/rcupdate.h>
56 #include <linux/kprobes.h>
58 #include <asm/sections.h>
60 #include "lockdep_internals.h"
62 #define CREATE_TRACE_POINTS
63 #include <trace/events/lock.h>
65 #ifdef CONFIG_PROVE_LOCKING
66 int prove_locking = 1;
67 module_param(prove_locking, int, 0644);
69 #define prove_locking 0
72 #ifdef CONFIG_LOCK_STAT
74 module_param(lock_stat, int, 0644);
79 DEFINE_PER_CPU(unsigned int, lockdep_recursion);
80 EXPORT_PER_CPU_SYMBOL_GPL(lockdep_recursion);
82 static inline bool lockdep_enabled(void)
87 if (this_cpu_read(lockdep_recursion))
90 if (current->lockdep_recursion)
97 * lockdep_lock: protects the lockdep graph, the hashes and the
98 * class/list/hash allocators.
100 * This is one of the rare exceptions where it's justified
101 * to use a raw spinlock - we really dont want the spinlock
102 * code to recurse back into the lockdep code...
104 static arch_spinlock_t __lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
105 static struct task_struct *__owner;
107 static inline void lockdep_lock(void)
109 DEBUG_LOCKS_WARN_ON(!irqs_disabled());
111 arch_spin_lock(&__lock);
113 __this_cpu_inc(lockdep_recursion);
116 static inline void lockdep_unlock(void)
118 if (debug_locks && DEBUG_LOCKS_WARN_ON(__owner != current))
121 __this_cpu_dec(lockdep_recursion);
123 arch_spin_unlock(&__lock);
126 static inline bool lockdep_assert_locked(void)
128 return DEBUG_LOCKS_WARN_ON(__owner != current);
131 static struct task_struct *lockdep_selftest_task_struct;
134 static int graph_lock(void)
138 * Make sure that if another CPU detected a bug while
139 * walking the graph we dont change it (while the other
140 * CPU is busy printing out stuff with the graph lock
150 static inline void graph_unlock(void)
156 * Turn lock debugging off and return with 0 if it was off already,
157 * and also release the graph lock:
159 static inline int debug_locks_off_graph_unlock(void)
161 int ret = debug_locks_off();
168 unsigned long nr_list_entries;
169 static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES];
170 static DECLARE_BITMAP(list_entries_in_use, MAX_LOCKDEP_ENTRIES);
173 * All data structures here are protected by the global debug_lock.
175 * nr_lock_classes is the number of elements of lock_classes[] that is
178 #define KEYHASH_BITS (MAX_LOCKDEP_KEYS_BITS - 1)
179 #define KEYHASH_SIZE (1UL << KEYHASH_BITS)
180 static struct hlist_head lock_keys_hash[KEYHASH_SIZE];
181 unsigned long nr_lock_classes;
182 unsigned long nr_zapped_classes;
183 #ifndef CONFIG_DEBUG_LOCKDEP
186 struct lock_class lock_classes[MAX_LOCKDEP_KEYS];
187 static DECLARE_BITMAP(lock_classes_in_use, MAX_LOCKDEP_KEYS);
189 static inline struct lock_class *hlock_class(struct held_lock *hlock)
191 unsigned int class_idx = hlock->class_idx;
193 /* Don't re-read hlock->class_idx, can't use READ_ONCE() on bitfield */
196 if (!test_bit(class_idx, lock_classes_in_use)) {
198 * Someone passed in garbage, we give up.
200 DEBUG_LOCKS_WARN_ON(1);
205 * At this point, if the passed hlock->class_idx is still garbage,
206 * we just have to live with it
208 return lock_classes + class_idx;
211 #ifdef CONFIG_LOCK_STAT
212 static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS], cpu_lock_stats);
214 static inline u64 lockstat_clock(void)
216 return local_clock();
219 static int lock_point(unsigned long points[], unsigned long ip)
223 for (i = 0; i < LOCKSTAT_POINTS; i++) {
224 if (points[i] == 0) {
235 static void lock_time_inc(struct lock_time *lt, u64 time)
240 if (time < lt->min || !lt->nr)
247 static inline void lock_time_add(struct lock_time *src, struct lock_time *dst)
252 if (src->max > dst->max)
255 if (src->min < dst->min || !dst->nr)
258 dst->total += src->total;
262 struct lock_class_stats lock_stats(struct lock_class *class)
264 struct lock_class_stats stats;
267 memset(&stats, 0, sizeof(struct lock_class_stats));
268 for_each_possible_cpu(cpu) {
269 struct lock_class_stats *pcs =
270 &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
272 for (i = 0; i < ARRAY_SIZE(stats.contention_point); i++)
273 stats.contention_point[i] += pcs->contention_point[i];
275 for (i = 0; i < ARRAY_SIZE(stats.contending_point); i++)
276 stats.contending_point[i] += pcs->contending_point[i];
278 lock_time_add(&pcs->read_waittime, &stats.read_waittime);
279 lock_time_add(&pcs->write_waittime, &stats.write_waittime);
281 lock_time_add(&pcs->read_holdtime, &stats.read_holdtime);
282 lock_time_add(&pcs->write_holdtime, &stats.write_holdtime);
284 for (i = 0; i < ARRAY_SIZE(stats.bounces); i++)
285 stats.bounces[i] += pcs->bounces[i];
291 void clear_lock_stats(struct lock_class *class)
295 for_each_possible_cpu(cpu) {
296 struct lock_class_stats *cpu_stats =
297 &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
299 memset(cpu_stats, 0, sizeof(struct lock_class_stats));
301 memset(class->contention_point, 0, sizeof(class->contention_point));
302 memset(class->contending_point, 0, sizeof(class->contending_point));
305 static struct lock_class_stats *get_lock_stats(struct lock_class *class)
307 return &this_cpu_ptr(cpu_lock_stats)[class - lock_classes];
310 static void lock_release_holdtime(struct held_lock *hlock)
312 struct lock_class_stats *stats;
318 holdtime = lockstat_clock() - hlock->holdtime_stamp;
320 stats = get_lock_stats(hlock_class(hlock));
322 lock_time_inc(&stats->read_holdtime, holdtime);
324 lock_time_inc(&stats->write_holdtime, holdtime);
327 static inline void lock_release_holdtime(struct held_lock *hlock)
333 * We keep a global list of all lock classes. The list is only accessed with
334 * the lockdep spinlock lock held. free_lock_classes is a list with free
335 * elements. These elements are linked together by the lock_entry member in
338 LIST_HEAD(all_lock_classes);
339 static LIST_HEAD(free_lock_classes);
342 * struct pending_free - information about data structures about to be freed
343 * @zapped: Head of a list with struct lock_class elements.
344 * @lock_chains_being_freed: Bitmap that indicates which lock_chains[] elements
345 * are about to be freed.
347 struct pending_free {
348 struct list_head zapped;
349 DECLARE_BITMAP(lock_chains_being_freed, MAX_LOCKDEP_CHAINS);
353 * struct delayed_free - data structures used for delayed freeing
355 * A data structure for delayed freeing of data structures that may be
356 * accessed by RCU readers at the time these were freed.
358 * @rcu_head: Used to schedule an RCU callback for freeing data structures.
359 * @index: Index of @pf to which freed data structures are added.
360 * @scheduled: Whether or not an RCU callback has been scheduled.
361 * @pf: Array with information about data structures about to be freed.
363 static struct delayed_free {
364 struct rcu_head rcu_head;
367 struct pending_free pf[2];
371 * The lockdep classes are in a hash-table as well, for fast lookup:
373 #define CLASSHASH_BITS (MAX_LOCKDEP_KEYS_BITS - 1)
374 #define CLASSHASH_SIZE (1UL << CLASSHASH_BITS)
375 #define __classhashfn(key) hash_long((unsigned long)key, CLASSHASH_BITS)
376 #define classhashentry(key) (classhash_table + __classhashfn((key)))
378 static struct hlist_head classhash_table[CLASSHASH_SIZE];
381 * We put the lock dependency chains into a hash-table as well, to cache
384 #define CHAINHASH_BITS (MAX_LOCKDEP_CHAINS_BITS-1)
385 #define CHAINHASH_SIZE (1UL << CHAINHASH_BITS)
386 #define __chainhashfn(chain) hash_long(chain, CHAINHASH_BITS)
387 #define chainhashentry(chain) (chainhash_table + __chainhashfn((chain)))
389 static struct hlist_head chainhash_table[CHAINHASH_SIZE];
392 * the id of held_lock
394 static inline u16 hlock_id(struct held_lock *hlock)
396 BUILD_BUG_ON(MAX_LOCKDEP_KEYS_BITS + 2 > 16);
398 return (hlock->class_idx | (hlock->read << MAX_LOCKDEP_KEYS_BITS));
401 static inline unsigned int chain_hlock_class_idx(u16 hlock_id)
403 return hlock_id & (MAX_LOCKDEP_KEYS - 1);
407 * The hash key of the lock dependency chains is a hash itself too:
408 * it's a hash of all locks taken up to that lock, including that lock.
409 * It's a 64-bit hash, because it's important for the keys to be
412 static inline u64 iterate_chain_key(u64 key, u32 idx)
414 u32 k0 = key, k1 = key >> 32;
416 __jhash_mix(idx, k0, k1); /* Macro that modifies arguments! */
418 return k0 | (u64)k1 << 32;
421 void lockdep_init_task(struct task_struct *task)
423 task->lockdep_depth = 0; /* no locks held yet */
424 task->curr_chain_key = INITIAL_CHAIN_KEY;
425 task->lockdep_recursion = 0;
428 static __always_inline void lockdep_recursion_inc(void)
430 __this_cpu_inc(lockdep_recursion);
433 static __always_inline void lockdep_recursion_finish(void)
435 if (WARN_ON_ONCE(__this_cpu_dec_return(lockdep_recursion)))
436 __this_cpu_write(lockdep_recursion, 0);
439 void lockdep_set_selftest_task(struct task_struct *task)
441 lockdep_selftest_task_struct = task;
445 * Debugging switches:
449 #define VERY_VERBOSE 0
452 # define HARDIRQ_VERBOSE 1
453 # define SOFTIRQ_VERBOSE 1
455 # define HARDIRQ_VERBOSE 0
456 # define SOFTIRQ_VERBOSE 0
459 #if VERBOSE || HARDIRQ_VERBOSE || SOFTIRQ_VERBOSE
461 * Quick filtering for interesting events:
463 static int class_filter(struct lock_class *class)
467 if (class->name_version == 1 &&
468 !strcmp(class->name, "lockname"))
470 if (class->name_version == 1 &&
471 !strcmp(class->name, "&struct->lockfield"))
474 /* Filter everything else. 1 would be to allow everything else */
479 static int verbose(struct lock_class *class)
482 return class_filter(class);
487 static void print_lockdep_off(const char *bug_msg)
489 printk(KERN_DEBUG "%s\n", bug_msg);
490 printk(KERN_DEBUG "turning off the locking correctness validator.\n");
491 #ifdef CONFIG_LOCK_STAT
492 printk(KERN_DEBUG "Please attach the output of /proc/lock_stat to the bug report\n");
496 unsigned long nr_stack_trace_entries;
498 #ifdef CONFIG_PROVE_LOCKING
500 * struct lock_trace - single stack backtrace
501 * @hash_entry: Entry in a stack_trace_hash[] list.
502 * @hash: jhash() of @entries.
503 * @nr_entries: Number of entries in @entries.
504 * @entries: Actual stack backtrace.
507 struct hlist_node hash_entry;
510 unsigned long entries[] __aligned(sizeof(unsigned long));
512 #define LOCK_TRACE_SIZE_IN_LONGS \
513 (sizeof(struct lock_trace) / sizeof(unsigned long))
515 * Stack-trace: sequence of lock_trace structures. Protected by the graph_lock.
517 static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];
518 static struct hlist_head stack_trace_hash[STACK_TRACE_HASH_SIZE];
520 static bool traces_identical(struct lock_trace *t1, struct lock_trace *t2)
522 return t1->hash == t2->hash && t1->nr_entries == t2->nr_entries &&
523 memcmp(t1->entries, t2->entries,
524 t1->nr_entries * sizeof(t1->entries[0])) == 0;
527 static struct lock_trace *save_trace(void)
529 struct lock_trace *trace, *t2;
530 struct hlist_head *hash_head;
534 BUILD_BUG_ON_NOT_POWER_OF_2(STACK_TRACE_HASH_SIZE);
535 BUILD_BUG_ON(LOCK_TRACE_SIZE_IN_LONGS >= MAX_STACK_TRACE_ENTRIES);
537 trace = (struct lock_trace *)(stack_trace + nr_stack_trace_entries);
538 max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries -
539 LOCK_TRACE_SIZE_IN_LONGS;
541 if (max_entries <= 0) {
542 if (!debug_locks_off_graph_unlock())
545 print_lockdep_off("BUG: MAX_STACK_TRACE_ENTRIES too low!");
550 trace->nr_entries = stack_trace_save(trace->entries, max_entries, 3);
552 hash = jhash(trace->entries, trace->nr_entries *
553 sizeof(trace->entries[0]), 0);
555 hash_head = stack_trace_hash + (hash & (STACK_TRACE_HASH_SIZE - 1));
556 hlist_for_each_entry(t2, hash_head, hash_entry) {
557 if (traces_identical(trace, t2))
560 nr_stack_trace_entries += LOCK_TRACE_SIZE_IN_LONGS + trace->nr_entries;
561 hlist_add_head(&trace->hash_entry, hash_head);
566 /* Return the number of stack traces in the stack_trace[] array. */
567 u64 lockdep_stack_trace_count(void)
569 struct lock_trace *trace;
573 for (i = 0; i < ARRAY_SIZE(stack_trace_hash); i++) {
574 hlist_for_each_entry(trace, &stack_trace_hash[i], hash_entry) {
582 /* Return the number of stack hash chains that have at least one stack trace. */
583 u64 lockdep_stack_hash_count(void)
588 for (i = 0; i < ARRAY_SIZE(stack_trace_hash); i++)
589 if (!hlist_empty(&stack_trace_hash[i]))
596 unsigned int nr_hardirq_chains;
597 unsigned int nr_softirq_chains;
598 unsigned int nr_process_chains;
599 unsigned int max_lockdep_depth;
601 #ifdef CONFIG_DEBUG_LOCKDEP
603 * Various lockdep statistics:
605 DEFINE_PER_CPU(struct lockdep_stats, lockdep_stats);
608 #ifdef CONFIG_PROVE_LOCKING
613 #define __USAGE(__STATE) \
614 [LOCK_USED_IN_##__STATE] = "IN-"__stringify(__STATE)"-W", \
615 [LOCK_ENABLED_##__STATE] = __stringify(__STATE)"-ON-W", \
616 [LOCK_USED_IN_##__STATE##_READ] = "IN-"__stringify(__STATE)"-R",\
617 [LOCK_ENABLED_##__STATE##_READ] = __stringify(__STATE)"-ON-R",
619 static const char *usage_str[] =
621 #define LOCKDEP_STATE(__STATE) __USAGE(__STATE)
622 #include "lockdep_states.h"
624 [LOCK_USED] = "INITIAL USE",
625 [LOCK_USED_READ] = "INITIAL READ USE",
626 /* abused as string storage for verify_lock_unused() */
627 [LOCK_USAGE_STATES] = "IN-NMI",
631 const char *__get_key_name(const struct lockdep_subclass_key *key, char *str)
633 return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str);
636 static inline unsigned long lock_flag(enum lock_usage_bit bit)
641 static char get_usage_char(struct lock_class *class, enum lock_usage_bit bit)
644 * The usage character defaults to '.' (i.e., irqs disabled and not in
645 * irq context), which is the safest usage category.
650 * The order of the following usage checks matters, which will
651 * result in the outcome character as follows:
653 * - '+': irq is enabled and not in irq context
654 * - '-': in irq context and irq is disabled
655 * - '?': in irq context and irq is enabled
657 if (class->usage_mask & lock_flag(bit + LOCK_USAGE_DIR_MASK)) {
659 if (class->usage_mask & lock_flag(bit))
661 } else if (class->usage_mask & lock_flag(bit))
667 void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS])
671 #define LOCKDEP_STATE(__STATE) \
672 usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE); \
673 usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE##_READ);
674 #include "lockdep_states.h"
680 static void __print_lock_name(struct lock_class *class)
682 char str[KSYM_NAME_LEN];
687 name = __get_key_name(class->key, str);
688 printk(KERN_CONT "%s", name);
690 printk(KERN_CONT "%s", name);
691 if (class->name_version > 1)
692 printk(KERN_CONT "#%d", class->name_version);
694 printk(KERN_CONT "/%d", class->subclass);
698 static void print_lock_name(struct lock_class *class)
700 char usage[LOCK_USAGE_CHARS];
702 get_usage_chars(class, usage);
704 printk(KERN_CONT " (");
705 __print_lock_name(class);
706 printk(KERN_CONT "){%s}-{%hd:%hd}", usage,
707 class->wait_type_outer ?: class->wait_type_inner,
708 class->wait_type_inner);
711 static void print_lockdep_cache(struct lockdep_map *lock)
714 char str[KSYM_NAME_LEN];
718 name = __get_key_name(lock->key->subkeys, str);
720 printk(KERN_CONT "%s", name);
723 static void print_lock(struct held_lock *hlock)
726 * We can be called locklessly through debug_show_all_locks() so be
727 * extra careful, the hlock might have been released and cleared.
729 * If this indeed happens, lets pretend it does not hurt to continue
730 * to print the lock unless the hlock class_idx does not point to a
731 * registered class. The rationale here is: since we don't attempt
732 * to distinguish whether we are in this situation, if it just
733 * happened we can't count on class_idx to tell either.
735 struct lock_class *lock = hlock_class(hlock);
738 printk(KERN_CONT "<RELEASED>\n");
742 printk(KERN_CONT "%px", hlock->instance);
743 print_lock_name(lock);
744 printk(KERN_CONT ", at: %pS\n", (void *)hlock->acquire_ip);
747 static void lockdep_print_held_locks(struct task_struct *p)
749 int i, depth = READ_ONCE(p->lockdep_depth);
752 printk("no locks held by %s/%d.\n", p->comm, task_pid_nr(p));
754 printk("%d lock%s held by %s/%d:\n", depth,
755 depth > 1 ? "s" : "", p->comm, task_pid_nr(p));
757 * It's not reliable to print a task's held locks if it's not sleeping
758 * and it's not the current task.
760 if (p->state == TASK_RUNNING && p != current)
762 for (i = 0; i < depth; i++) {
764 print_lock(p->held_locks + i);
768 static void print_kernel_ident(void)
770 printk("%s %.*s %s\n", init_utsname()->release,
771 (int)strcspn(init_utsname()->version, " "),
772 init_utsname()->version,
776 static int very_verbose(struct lock_class *class)
779 return class_filter(class);
785 * Is this the address of a static object:
788 static int static_obj(const void *obj)
790 unsigned long start = (unsigned long) &_stext,
791 end = (unsigned long) &_end,
792 addr = (unsigned long) obj;
794 if (arch_is_kernel_initmem_freed(addr))
800 if ((addr >= start) && (addr < end))
803 if (arch_is_kernel_data(addr))
807 * in-kernel percpu var?
809 if (is_kernel_percpu_address(addr))
813 * module static or percpu var?
815 return is_module_address(addr) || is_module_percpu_address(addr);
820 * To make lock name printouts unique, we calculate a unique
821 * class->name_version generation counter. The caller must hold the graph
824 static int count_matching_names(struct lock_class *new_class)
826 struct lock_class *class;
829 if (!new_class->name)
832 list_for_each_entry(class, &all_lock_classes, lock_entry) {
833 if (new_class->key - new_class->subclass == class->key)
834 return class->name_version;
835 if (class->name && !strcmp(class->name, new_class->name))
836 count = max(count, class->name_version);
842 /* used from NMI context -- must be lockless */
843 static __always_inline struct lock_class *
844 look_up_lock_class(const struct lockdep_map *lock, unsigned int subclass)
846 struct lockdep_subclass_key *key;
847 struct hlist_head *hash_head;
848 struct lock_class *class;
850 if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
853 "BUG: looking up invalid subclass: %u\n", subclass);
855 "turning off the locking correctness validator.\n");
861 * If it is not initialised then it has never been locked,
862 * so it won't be present in the hash table.
864 if (unlikely(!lock->key))
868 * NOTE: the class-key must be unique. For dynamic locks, a static
869 * lock_class_key variable is passed in through the mutex_init()
870 * (or spin_lock_init()) call - which acts as the key. For static
871 * locks we use the lock object itself as the key.
873 BUILD_BUG_ON(sizeof(struct lock_class_key) >
874 sizeof(struct lockdep_map));
876 key = lock->key->subkeys + subclass;
878 hash_head = classhashentry(key);
881 * We do an RCU walk of the hash, see lockdep_free_key_range().
883 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
886 hlist_for_each_entry_rcu(class, hash_head, hash_entry) {
887 if (class->key == key) {
889 * Huh! same key, different name? Did someone trample
890 * on some memory? We're most confused.
892 WARN_ON_ONCE(class->name != lock->name &&
893 lock->key != &__lockdep_no_validate__);
902 * Static locks do not have their class-keys yet - for them the key is
903 * the lock object itself. If the lock is in the per cpu area, the
904 * canonical address of the lock (per cpu offset removed) is used.
906 static bool assign_lock_key(struct lockdep_map *lock)
908 unsigned long can_addr, addr = (unsigned long)lock;
912 * lockdep_free_key_range() assumes that struct lock_class_key
913 * objects do not overlap. Since we use the address of lock
914 * objects as class key for static objects, check whether the
915 * size of lock_class_key objects does not exceed the size of
916 * the smallest lock object.
918 BUILD_BUG_ON(sizeof(struct lock_class_key) > sizeof(raw_spinlock_t));
921 if (__is_kernel_percpu_address(addr, &can_addr))
922 lock->key = (void *)can_addr;
923 else if (__is_module_percpu_address(addr, &can_addr))
924 lock->key = (void *)can_addr;
925 else if (static_obj(lock))
926 lock->key = (void *)lock;
928 /* Debug-check: all keys must be persistent! */
930 pr_err("INFO: trying to register non-static key.\n");
931 pr_err("the code is fine but needs lockdep annotation.\n");
932 pr_err("turning off the locking correctness validator.\n");
940 #ifdef CONFIG_DEBUG_LOCKDEP
942 /* Check whether element @e occurs in list @h */
943 static bool in_list(struct list_head *e, struct list_head *h)
947 list_for_each(f, h) {
956 * Check whether entry @e occurs in any of the locks_after or locks_before
959 static bool in_any_class_list(struct list_head *e)
961 struct lock_class *class;
964 for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
965 class = &lock_classes[i];
966 if (in_list(e, &class->locks_after) ||
967 in_list(e, &class->locks_before))
973 static bool class_lock_list_valid(struct lock_class *c, struct list_head *h)
977 list_for_each_entry(e, h, entry) {
978 if (e->links_to != c) {
979 printk(KERN_INFO "class %s: mismatch for lock entry %ld; class %s <> %s",
981 (unsigned long)(e - list_entries),
982 e->links_to && e->links_to->name ?
983 e->links_to->name : "(?)",
984 e->class && e->class->name ? e->class->name :
992 #ifdef CONFIG_PROVE_LOCKING
993 static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
996 static bool check_lock_chain_key(struct lock_chain *chain)
998 #ifdef CONFIG_PROVE_LOCKING
999 u64 chain_key = INITIAL_CHAIN_KEY;
1002 for (i = chain->base; i < chain->base + chain->depth; i++)
1003 chain_key = iterate_chain_key(chain_key, chain_hlocks[i]);
1005 * The 'unsigned long long' casts avoid that a compiler warning
1006 * is reported when building tools/lib/lockdep.
1008 if (chain->chain_key != chain_key) {
1009 printk(KERN_INFO "chain %lld: key %#llx <> %#llx\n",
1010 (unsigned long long)(chain - lock_chains),
1011 (unsigned long long)chain->chain_key,
1012 (unsigned long long)chain_key);
1019 static bool in_any_zapped_class_list(struct lock_class *class)
1021 struct pending_free *pf;
1024 for (i = 0, pf = delayed_free.pf; i < ARRAY_SIZE(delayed_free.pf); i++, pf++) {
1025 if (in_list(&class->lock_entry, &pf->zapped))
1032 static bool __check_data_structures(void)
1034 struct lock_class *class;
1035 struct lock_chain *chain;
1036 struct hlist_head *head;
1037 struct lock_list *e;
1040 /* Check whether all classes occur in a lock list. */
1041 for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
1042 class = &lock_classes[i];
1043 if (!in_list(&class->lock_entry, &all_lock_classes) &&
1044 !in_list(&class->lock_entry, &free_lock_classes) &&
1045 !in_any_zapped_class_list(class)) {
1046 printk(KERN_INFO "class %px/%s is not in any class list\n",
1047 class, class->name ? : "(?)");
1052 /* Check whether all classes have valid lock lists. */
1053 for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
1054 class = &lock_classes[i];
1055 if (!class_lock_list_valid(class, &class->locks_before))
1057 if (!class_lock_list_valid(class, &class->locks_after))
1061 /* Check the chain_key of all lock chains. */
1062 for (i = 0; i < ARRAY_SIZE(chainhash_table); i++) {
1063 head = chainhash_table + i;
1064 hlist_for_each_entry_rcu(chain, head, entry) {
1065 if (!check_lock_chain_key(chain))
1071 * Check whether all list entries that are in use occur in a class
1074 for_each_set_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
1075 e = list_entries + i;
1076 if (!in_any_class_list(&e->entry)) {
1077 printk(KERN_INFO "list entry %d is not in any class list; class %s <> %s\n",
1078 (unsigned int)(e - list_entries),
1079 e->class->name ? : "(?)",
1080 e->links_to->name ? : "(?)");
1086 * Check whether all list entries that are not in use do not occur in
1087 * a class lock list.
1089 for_each_clear_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
1090 e = list_entries + i;
1091 if (in_any_class_list(&e->entry)) {
1092 printk(KERN_INFO "list entry %d occurs in a class list; class %s <> %s\n",
1093 (unsigned int)(e - list_entries),
1094 e->class && e->class->name ? e->class->name :
1096 e->links_to && e->links_to->name ?
1097 e->links_to->name : "(?)");
1105 int check_consistency = 0;
1106 module_param(check_consistency, int, 0644);
1108 static void check_data_structures(void)
1110 static bool once = false;
1112 if (check_consistency && !once) {
1113 if (!__check_data_structures()) {
1120 #else /* CONFIG_DEBUG_LOCKDEP */
1122 static inline void check_data_structures(void) { }
1124 #endif /* CONFIG_DEBUG_LOCKDEP */
1126 static void init_chain_block_buckets(void);
1129 * Initialize the lock_classes[] array elements, the free_lock_classes list
1130 * and also the delayed_free structure.
1132 static void init_data_structures_once(void)
1134 static bool __read_mostly ds_initialized, rcu_head_initialized;
1137 if (likely(rcu_head_initialized))
1140 if (system_state >= SYSTEM_SCHEDULING) {
1141 init_rcu_head(&delayed_free.rcu_head);
1142 rcu_head_initialized = true;
1148 ds_initialized = true;
1150 INIT_LIST_HEAD(&delayed_free.pf[0].zapped);
1151 INIT_LIST_HEAD(&delayed_free.pf[1].zapped);
1153 for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
1154 list_add_tail(&lock_classes[i].lock_entry, &free_lock_classes);
1155 INIT_LIST_HEAD(&lock_classes[i].locks_after);
1156 INIT_LIST_HEAD(&lock_classes[i].locks_before);
1158 init_chain_block_buckets();
1161 static inline struct hlist_head *keyhashentry(const struct lock_class_key *key)
1163 unsigned long hash = hash_long((uintptr_t)key, KEYHASH_BITS);
1165 return lock_keys_hash + hash;
1168 /* Register a dynamically allocated key. */
1169 void lockdep_register_key(struct lock_class_key *key)
1171 struct hlist_head *hash_head;
1172 struct lock_class_key *k;
1173 unsigned long flags;
1175 if (WARN_ON_ONCE(static_obj(key)))
1177 hash_head = keyhashentry(key);
1179 raw_local_irq_save(flags);
1182 hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
1183 if (WARN_ON_ONCE(k == key))
1186 hlist_add_head_rcu(&key->hash_entry, hash_head);
1190 raw_local_irq_restore(flags);
1192 EXPORT_SYMBOL_GPL(lockdep_register_key);
1194 /* Check whether a key has been registered as a dynamic key. */
1195 static bool is_dynamic_key(const struct lock_class_key *key)
1197 struct hlist_head *hash_head;
1198 struct lock_class_key *k;
1201 if (WARN_ON_ONCE(static_obj(key)))
1205 * If lock debugging is disabled lock_keys_hash[] may contain
1206 * pointers to memory that has already been freed. Avoid triggering
1207 * a use-after-free in that case by returning early.
1212 hash_head = keyhashentry(key);
1215 hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
1227 * Register a lock's class in the hash-table, if the class is not present
1228 * yet. Otherwise we look it up. We cache the result in the lock object
1229 * itself, so actual lookup of the hash should be once per lock object.
1231 static struct lock_class *
1232 register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
1234 struct lockdep_subclass_key *key;
1235 struct hlist_head *hash_head;
1236 struct lock_class *class;
1238 DEBUG_LOCKS_WARN_ON(!irqs_disabled());
1240 class = look_up_lock_class(lock, subclass);
1242 goto out_set_class_cache;
1245 if (!assign_lock_key(lock))
1247 } else if (!static_obj(lock->key) && !is_dynamic_key(lock->key)) {
1251 key = lock->key->subkeys + subclass;
1252 hash_head = classhashentry(key);
1254 if (!graph_lock()) {
1258 * We have to do the hash-walk again, to avoid races
1261 hlist_for_each_entry_rcu(class, hash_head, hash_entry) {
1262 if (class->key == key)
1263 goto out_unlock_set;
1266 init_data_structures_once();
1268 /* Allocate a new lock class and add it to the hash. */
1269 class = list_first_entry_or_null(&free_lock_classes, typeof(*class),
1272 if (!debug_locks_off_graph_unlock()) {
1276 print_lockdep_off("BUG: MAX_LOCKDEP_KEYS too low!");
1281 __set_bit(class - lock_classes, lock_classes_in_use);
1282 debug_atomic_inc(nr_unused_locks);
1284 class->name = lock->name;
1285 class->subclass = subclass;
1286 WARN_ON_ONCE(!list_empty(&class->locks_before));
1287 WARN_ON_ONCE(!list_empty(&class->locks_after));
1288 class->name_version = count_matching_names(class);
1289 class->wait_type_inner = lock->wait_type_inner;
1290 class->wait_type_outer = lock->wait_type_outer;
1292 * We use RCU's safe list-add method to make
1293 * parallel walking of the hash-list safe:
1295 hlist_add_head_rcu(&class->hash_entry, hash_head);
1297 * Remove the class from the free list and add it to the global list
1300 list_move_tail(&class->lock_entry, &all_lock_classes);
1302 if (verbose(class)) {
1305 printk("\nnew class %px: %s", class->key, class->name);
1306 if (class->name_version > 1)
1307 printk(KERN_CONT "#%d", class->name_version);
1308 printk(KERN_CONT "\n");
1311 if (!graph_lock()) {
1318 out_set_class_cache:
1319 if (!subclass || force)
1320 lock->class_cache[0] = class;
1321 else if (subclass < NR_LOCKDEP_CACHING_CLASSES)
1322 lock->class_cache[subclass] = class;
1325 * Hash collision, did we smoke some? We found a class with a matching
1326 * hash but the subclass -- which is hashed in -- didn't match.
1328 if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))
1334 #ifdef CONFIG_PROVE_LOCKING
1336 * Allocate a lockdep entry. (assumes the graph_lock held, returns
1337 * with NULL on failure)
1339 static struct lock_list *alloc_list_entry(void)
1341 int idx = find_first_zero_bit(list_entries_in_use,
1342 ARRAY_SIZE(list_entries));
1344 if (idx >= ARRAY_SIZE(list_entries)) {
1345 if (!debug_locks_off_graph_unlock())
1348 print_lockdep_off("BUG: MAX_LOCKDEP_ENTRIES too low!");
1353 __set_bit(idx, list_entries_in_use);
1354 return list_entries + idx;
1358 * Add a new dependency to the head of the list:
1360 static int add_lock_to_list(struct lock_class *this,
1361 struct lock_class *links_to, struct list_head *head,
1362 unsigned long ip, u16 distance, u8 dep,
1363 const struct lock_trace *trace)
1365 struct lock_list *entry;
1367 * Lock not present yet - get a new dependency struct and
1368 * add it to the list:
1370 entry = alloc_list_entry();
1374 entry->class = this;
1375 entry->links_to = links_to;
1377 entry->distance = distance;
1378 entry->trace = trace;
1380 * Both allocation and removal are done under the graph lock; but
1381 * iteration is under RCU-sched; see look_up_lock_class() and
1382 * lockdep_free_key_range().
1384 list_add_tail_rcu(&entry->entry, head);
1390 * For good efficiency of modular, we use power of 2
1392 #define MAX_CIRCULAR_QUEUE_SIZE 4096UL
1393 #define CQ_MASK (MAX_CIRCULAR_QUEUE_SIZE-1)
1396 * The circular_queue and helpers are used to implement graph
1397 * breadth-first search (BFS) algorithm, by which we can determine
1398 * whether there is a path from a lock to another. In deadlock checks,
1399 * a path from the next lock to be acquired to a previous held lock
1400 * indicates that adding the <prev> -> <next> lock dependency will
1401 * produce a circle in the graph. Breadth-first search instead of
1402 * depth-first search is used in order to find the shortest (circular)
1405 struct circular_queue {
1406 struct lock_list *element[MAX_CIRCULAR_QUEUE_SIZE];
1407 unsigned int front, rear;
1410 static struct circular_queue lock_cq;
1412 unsigned int max_bfs_queue_depth;
1414 static unsigned int lockdep_dependency_gen_id;
1416 static inline void __cq_init(struct circular_queue *cq)
1418 cq->front = cq->rear = 0;
1419 lockdep_dependency_gen_id++;
1422 static inline int __cq_empty(struct circular_queue *cq)
1424 return (cq->front == cq->rear);
1427 static inline int __cq_full(struct circular_queue *cq)
1429 return ((cq->rear + 1) & CQ_MASK) == cq->front;
1432 static inline int __cq_enqueue(struct circular_queue *cq, struct lock_list *elem)
1437 cq->element[cq->rear] = elem;
1438 cq->rear = (cq->rear + 1) & CQ_MASK;
1443 * Dequeue an element from the circular_queue, return a lock_list if
1444 * the queue is not empty, or NULL if otherwise.
1446 static inline struct lock_list * __cq_dequeue(struct circular_queue *cq)
1448 struct lock_list * lock;
1453 lock = cq->element[cq->front];
1454 cq->front = (cq->front + 1) & CQ_MASK;
1459 static inline unsigned int __cq_get_elem_count(struct circular_queue *cq)
1461 return (cq->rear - cq->front) & CQ_MASK;
1464 static inline void mark_lock_accessed(struct lock_list *lock)
1466 lock->class->dep_gen_id = lockdep_dependency_gen_id;
1469 static inline void visit_lock_entry(struct lock_list *lock,
1470 struct lock_list *parent)
1472 lock->parent = parent;
1475 static inline unsigned long lock_accessed(struct lock_list *lock)
1477 return lock->class->dep_gen_id == lockdep_dependency_gen_id;
1480 static inline struct lock_list *get_lock_parent(struct lock_list *child)
1482 return child->parent;
1485 static inline int get_lock_depth(struct lock_list *child)
1488 struct lock_list *parent;
1490 while ((parent = get_lock_parent(child))) {
1498 * Return the forward or backward dependency list.
1500 * @lock: the lock_list to get its class's dependency list
1501 * @offset: the offset to struct lock_class to determine whether it is
1502 * locks_after or locks_before
1504 static inline struct list_head *get_dep_list(struct lock_list *lock, int offset)
1506 void *lock_class = lock->class;
1508 return lock_class + offset;
1511 * Return values of a bfs search:
1513 * BFS_E* indicates an error
1514 * BFS_R* indicates a result (match or not)
1516 * BFS_EINVALIDNODE: Find a invalid node in the graph.
1518 * BFS_EQUEUEFULL: The queue is full while doing the bfs.
1520 * BFS_RMATCH: Find the matched node in the graph, and put that node into
1523 * BFS_RNOMATCH: Haven't found the matched node and keep *@target_entry
1527 BFS_EINVALIDNODE = -2,
1528 BFS_EQUEUEFULL = -1,
1534 * bfs_result < 0 means error
1536 static inline bool bfs_error(enum bfs_result res)
1542 * DEP_*_BIT in lock_list::dep
1544 * For dependency @prev -> @next:
1546 * SR: @prev is shared reader (->read != 0) and @next is recursive reader
1548 * ER: @prev is exclusive locker (->read == 0) and @next is recursive reader
1549 * SN: @prev is shared reader and @next is non-recursive locker (->read != 2)
1550 * EN: @prev is exclusive locker and @next is non-recursive locker
1552 * Note that we define the value of DEP_*_BITs so that:
1553 * bit0 is prev->read == 0
1554 * bit1 is next->read != 2
1556 #define DEP_SR_BIT (0 + (0 << 1)) /* 0 */
1557 #define DEP_ER_BIT (1 + (0 << 1)) /* 1 */
1558 #define DEP_SN_BIT (0 + (1 << 1)) /* 2 */
1559 #define DEP_EN_BIT (1 + (1 << 1)) /* 3 */
1561 #define DEP_SR_MASK (1U << (DEP_SR_BIT))
1562 #define DEP_ER_MASK (1U << (DEP_ER_BIT))
1563 #define DEP_SN_MASK (1U << (DEP_SN_BIT))
1564 #define DEP_EN_MASK (1U << (DEP_EN_BIT))
1566 static inline unsigned int
1567 __calc_dep_bit(struct held_lock *prev, struct held_lock *next)
1569 return (prev->read == 0) + ((next->read != 2) << 1);
1572 static inline u8 calc_dep(struct held_lock *prev, struct held_lock *next)
1574 return 1U << __calc_dep_bit(prev, next);
1578 * calculate the dep_bit for backwards edges. We care about whether @prev is
1579 * shared and whether @next is recursive.
1581 static inline unsigned int
1582 __calc_dep_bitb(struct held_lock *prev, struct held_lock *next)
1584 return (next->read != 2) + ((prev->read == 0) << 1);
1587 static inline u8 calc_depb(struct held_lock *prev, struct held_lock *next)
1589 return 1U << __calc_dep_bitb(prev, next);
1593 * Initialize a lock_list entry @lock belonging to @class as the root for a BFS
1596 static inline void __bfs_init_root(struct lock_list *lock,
1597 struct lock_class *class)
1599 lock->class = class;
1600 lock->parent = NULL;
1605 * Initialize a lock_list entry @lock based on a lock acquisition @hlock as the
1606 * root for a BFS search.
1608 * ->only_xr of the initial lock node is set to @hlock->read == 2, to make sure
1609 * that <prev> -> @hlock and @hlock -> <whatever __bfs() found> is not -(*R)->
1612 static inline void bfs_init_root(struct lock_list *lock,
1613 struct held_lock *hlock)
1615 __bfs_init_root(lock, hlock_class(hlock));
1616 lock->only_xr = (hlock->read == 2);
1620 * Similar to bfs_init_root() but initialize the root for backwards BFS.
1622 * ->only_xr of the initial lock node is set to @hlock->read != 0, to make sure
1623 * that <next> -> @hlock and @hlock -> <whatever backwards BFS found> is not
1624 * -(*S)-> and -(R*)-> (reverse order of -(*R)-> and -(S*)->).
1626 static inline void bfs_init_rootb(struct lock_list *lock,
1627 struct held_lock *hlock)
1629 __bfs_init_root(lock, hlock_class(hlock));
1630 lock->only_xr = (hlock->read != 0);
1633 static inline struct lock_list *__bfs_next(struct lock_list *lock, int offset)
1635 if (!lock || !lock->parent)
1638 return list_next_or_null_rcu(get_dep_list(lock->parent, offset),
1639 &lock->entry, struct lock_list, entry);
1643 * Breadth-First Search to find a strong path in the dependency graph.
1645 * @source_entry: the source of the path we are searching for.
1646 * @data: data used for the second parameter of @match function
1647 * @match: match function for the search
1648 * @target_entry: pointer to the target of a matched path
1649 * @offset: the offset to struct lock_class to determine whether it is
1650 * locks_after or locks_before
1652 * We may have multiple edges (considering different kinds of dependencies,
1653 * e.g. ER and SN) between two nodes in the dependency graph. But
1654 * only the strong dependency path in the graph is relevant to deadlocks. A
1655 * strong dependency path is a dependency path that doesn't have two adjacent
1656 * dependencies as -(*R)-> -(S*)->, please see:
1658 * Documentation/locking/lockdep-design.rst
1660 * for more explanation of the definition of strong dependency paths
1662 * In __bfs(), we only traverse in the strong dependency path:
1664 * In lock_list::only_xr, we record whether the previous dependency only
1665 * has -(*R)-> in the search, and if it does (prev only has -(*R)->), we
1666 * filter out any -(S*)-> in the current dependency and after that, the
1667 * ->only_xr is set according to whether we only have -(*R)-> left.
1669 static enum bfs_result __bfs(struct lock_list *source_entry,
1671 bool (*match)(struct lock_list *entry, void *data),
1672 struct lock_list **target_entry,
1675 struct circular_queue *cq = &lock_cq;
1676 struct lock_list *lock = NULL;
1677 struct lock_list *entry;
1678 struct list_head *head;
1679 unsigned int cq_depth;
1682 lockdep_assert_locked();
1685 __cq_enqueue(cq, source_entry);
1687 while ((lock = __bfs_next(lock, offset)) || (lock = __cq_dequeue(cq))) {
1689 return BFS_EINVALIDNODE;
1692 * Step 1: check whether we already finish on this one.
1694 * If we have visited all the dependencies from this @lock to
1695 * others (iow, if we have visited all lock_list entries in
1696 * @lock->class->locks_{after,before}) we skip, otherwise go
1697 * and visit all the dependencies in the list and mark this
1700 if (lock_accessed(lock))
1703 mark_lock_accessed(lock);
1706 * Step 2: check whether prev dependency and this form a strong
1709 if (lock->parent) { /* Parent exists, check prev dependency */
1711 bool prev_only_xr = lock->parent->only_xr;
1714 * Mask out all -(S*)-> if we only have *R in previous
1715 * step, because -(*R)-> -(S*)-> don't make up a strong
1719 dep &= ~(DEP_SR_MASK | DEP_SN_MASK);
1721 /* If nothing left, we skip */
1725 /* If there are only -(*R)-> left, set that for the next step */
1726 lock->only_xr = !(dep & (DEP_SN_MASK | DEP_EN_MASK));
1730 * Step 3: we haven't visited this and there is a strong
1731 * dependency path to this, so check with @match.
1733 if (match(lock, data)) {
1734 *target_entry = lock;
1739 * Step 4: if not match, expand the path by adding the
1740 * forward or backwards dependencis in the search
1744 head = get_dep_list(lock, offset);
1745 list_for_each_entry_rcu(entry, head, entry) {
1746 visit_lock_entry(entry, lock);
1749 * Note we only enqueue the first of the list into the
1750 * queue, because we can always find a sibling
1751 * dependency from one (see __bfs_next()), as a result
1752 * the space of queue is saved.
1759 if (__cq_enqueue(cq, entry))
1760 return BFS_EQUEUEFULL;
1762 cq_depth = __cq_get_elem_count(cq);
1763 if (max_bfs_queue_depth < cq_depth)
1764 max_bfs_queue_depth = cq_depth;
1768 return BFS_RNOMATCH;
1771 static inline enum bfs_result
1772 __bfs_forwards(struct lock_list *src_entry,
1774 bool (*match)(struct lock_list *entry, void *data),
1775 struct lock_list **target_entry)
1777 return __bfs(src_entry, data, match, target_entry,
1778 offsetof(struct lock_class, locks_after));
1782 static inline enum bfs_result
1783 __bfs_backwards(struct lock_list *src_entry,
1785 bool (*match)(struct lock_list *entry, void *data),
1786 struct lock_list **target_entry)
1788 return __bfs(src_entry, data, match, target_entry,
1789 offsetof(struct lock_class, locks_before));
1793 static void print_lock_trace(const struct lock_trace *trace,
1794 unsigned int spaces)
1796 stack_trace_print(trace->entries, trace->nr_entries, spaces);
1800 * Print a dependency chain entry (this is only done when a deadlock
1801 * has been detected):
1803 static noinline void
1804 print_circular_bug_entry(struct lock_list *target, int depth)
1806 if (debug_locks_silent)
1808 printk("\n-> #%u", depth);
1809 print_lock_name(target->class);
1810 printk(KERN_CONT ":\n");
1811 print_lock_trace(target->trace, 6);
1815 print_circular_lock_scenario(struct held_lock *src,
1816 struct held_lock *tgt,
1817 struct lock_list *prt)
1819 struct lock_class *source = hlock_class(src);
1820 struct lock_class *target = hlock_class(tgt);
1821 struct lock_class *parent = prt->class;
1824 * A direct locking problem where unsafe_class lock is taken
1825 * directly by safe_class lock, then all we need to show
1826 * is the deadlock scenario, as it is obvious that the
1827 * unsafe lock is taken under the safe lock.
1829 * But if there is a chain instead, where the safe lock takes
1830 * an intermediate lock (middle_class) where this lock is
1831 * not the same as the safe lock, then the lock chain is
1832 * used to describe the problem. Otherwise we would need
1833 * to show a different CPU case for each link in the chain
1834 * from the safe_class lock to the unsafe_class lock.
1836 if (parent != source) {
1837 printk("Chain exists of:\n ");
1838 __print_lock_name(source);
1839 printk(KERN_CONT " --> ");
1840 __print_lock_name(parent);
1841 printk(KERN_CONT " --> ");
1842 __print_lock_name(target);
1843 printk(KERN_CONT "\n\n");
1846 printk(" Possible unsafe locking scenario:\n\n");
1847 printk(" CPU0 CPU1\n");
1848 printk(" ---- ----\n");
1850 __print_lock_name(target);
1851 printk(KERN_CONT ");\n");
1853 __print_lock_name(parent);
1854 printk(KERN_CONT ");\n");
1856 __print_lock_name(target);
1857 printk(KERN_CONT ");\n");
1859 __print_lock_name(source);
1860 printk(KERN_CONT ");\n");
1861 printk("\n *** DEADLOCK ***\n\n");
1865 * When a circular dependency is detected, print the
1868 static noinline void
1869 print_circular_bug_header(struct lock_list *entry, unsigned int depth,
1870 struct held_lock *check_src,
1871 struct held_lock *check_tgt)
1873 struct task_struct *curr = current;
1875 if (debug_locks_silent)
1879 pr_warn("======================================================\n");
1880 pr_warn("WARNING: possible circular locking dependency detected\n");
1881 print_kernel_ident();
1882 pr_warn("------------------------------------------------------\n");
1883 pr_warn("%s/%d is trying to acquire lock:\n",
1884 curr->comm, task_pid_nr(curr));
1885 print_lock(check_src);
1887 pr_warn("\nbut task is already holding lock:\n");
1889 print_lock(check_tgt);
1890 pr_warn("\nwhich lock already depends on the new lock.\n\n");
1891 pr_warn("\nthe existing dependency chain (in reverse order) is:\n");
1893 print_circular_bug_entry(entry, depth);
1897 * We are about to add A -> B into the dependency graph, and in __bfs() a
1898 * strong dependency path A -> .. -> B is found: hlock_class equals
1901 * If A -> .. -> B can replace A -> B in any __bfs() search (means the former
1902 * is _stronger_ than or equal to the latter), we consider A -> B as redundant.
1903 * For example if A -> .. -> B is -(EN)-> (i.e. A -(E*)-> .. -(*N)-> B), and A
1904 * -> B is -(ER)-> or -(EN)->, then we don't need to add A -> B into the
1905 * dependency graph, as any strong path ..-> A -> B ->.. we can get with
1906 * having dependency A -> B, we could already get a equivalent path ..-> A ->
1907 * .. -> B -> .. with A -> .. -> B. Therefore A -> B is reduntant.
1909 * We need to make sure both the start and the end of A -> .. -> B is not
1910 * weaker than A -> B. For the start part, please see the comment in
1911 * check_redundant(). For the end part, we need:
1915 * a) A -> B is -(*R)-> (everything is not weaker than that)
1919 * b) A -> .. -> B is -(*N)-> (nothing is stronger than this)
1922 static inline bool hlock_equal(struct lock_list *entry, void *data)
1924 struct held_lock *hlock = (struct held_lock *)data;
1926 return hlock_class(hlock) == entry->class && /* Found A -> .. -> B */
1927 (hlock->read == 2 || /* A -> B is -(*R)-> */
1928 !entry->only_xr); /* A -> .. -> B is -(*N)-> */
1932 * We are about to add B -> A into the dependency graph, and in __bfs() a
1933 * strong dependency path A -> .. -> B is found: hlock_class equals
1936 * We will have a deadlock case (conflict) if A -> .. -> B -> A is a strong
1937 * dependency cycle, that means:
1941 * a) B -> A is -(E*)->
1945 * b) A -> .. -> B is -(*N)-> (i.e. A -> .. -(*N)-> B)
1947 * as then we don't have -(*R)-> -(S*)-> in the cycle.
1949 static inline bool hlock_conflict(struct lock_list *entry, void *data)
1951 struct held_lock *hlock = (struct held_lock *)data;
1953 return hlock_class(hlock) == entry->class && /* Found A -> .. -> B */
1954 (hlock->read == 0 || /* B -> A is -(E*)-> */
1955 !entry->only_xr); /* A -> .. -> B is -(*N)-> */
1958 static noinline void print_circular_bug(struct lock_list *this,
1959 struct lock_list *target,
1960 struct held_lock *check_src,
1961 struct held_lock *check_tgt)
1963 struct task_struct *curr = current;
1964 struct lock_list *parent;
1965 struct lock_list *first_parent;
1968 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1971 this->trace = save_trace();
1975 depth = get_lock_depth(target);
1977 print_circular_bug_header(target, depth, check_src, check_tgt);
1979 parent = get_lock_parent(target);
1980 first_parent = parent;
1983 print_circular_bug_entry(parent, --depth);
1984 parent = get_lock_parent(parent);
1987 printk("\nother info that might help us debug this:\n\n");
1988 print_circular_lock_scenario(check_src, check_tgt,
1991 lockdep_print_held_locks(curr);
1993 printk("\nstack backtrace:\n");
1997 static noinline void print_bfs_bug(int ret)
1999 if (!debug_locks_off_graph_unlock())
2003 * Breadth-first-search failed, graph got corrupted?
2005 WARN(1, "lockdep bfs error:%d\n", ret);
2008 static bool noop_count(struct lock_list *entry, void *data)
2010 (*(unsigned long *)data)++;
2014 static unsigned long __lockdep_count_forward_deps(struct lock_list *this)
2016 unsigned long count = 0;
2017 struct lock_list *target_entry;
2019 __bfs_forwards(this, (void *)&count, noop_count, &target_entry);
2023 unsigned long lockdep_count_forward_deps(struct lock_class *class)
2025 unsigned long ret, flags;
2026 struct lock_list this;
2028 __bfs_init_root(&this, class);
2030 raw_local_irq_save(flags);
2032 ret = __lockdep_count_forward_deps(&this);
2034 raw_local_irq_restore(flags);
2039 static unsigned long __lockdep_count_backward_deps(struct lock_list *this)
2041 unsigned long count = 0;
2042 struct lock_list *target_entry;
2044 __bfs_backwards(this, (void *)&count, noop_count, &target_entry);
2049 unsigned long lockdep_count_backward_deps(struct lock_class *class)
2051 unsigned long ret, flags;
2052 struct lock_list this;
2054 __bfs_init_root(&this, class);
2056 raw_local_irq_save(flags);
2058 ret = __lockdep_count_backward_deps(&this);
2060 raw_local_irq_restore(flags);
2066 * Check that the dependency graph starting at <src> can lead to
2069 static noinline enum bfs_result
2070 check_path(struct held_lock *target, struct lock_list *src_entry,
2071 bool (*match)(struct lock_list *entry, void *data),
2072 struct lock_list **target_entry)
2074 enum bfs_result ret;
2076 ret = __bfs_forwards(src_entry, target, match, target_entry);
2078 if (unlikely(bfs_error(ret)))
2085 * Prove that the dependency graph starting at <src> can not
2086 * lead to <target>. If it can, there is a circle when adding
2087 * <target> -> <src> dependency.
2089 * Print an error and return BFS_RMATCH if it does.
2091 static noinline enum bfs_result
2092 check_noncircular(struct held_lock *src, struct held_lock *target,
2093 struct lock_trace **const trace)
2095 enum bfs_result ret;
2096 struct lock_list *target_entry;
2097 struct lock_list src_entry;
2099 bfs_init_root(&src_entry, src);
2101 debug_atomic_inc(nr_cyclic_checks);
2103 ret = check_path(target, &src_entry, hlock_conflict, &target_entry);
2105 if (unlikely(ret == BFS_RMATCH)) {
2108 * If save_trace fails here, the printing might
2109 * trigger a WARN but because of the !nr_entries it
2110 * should not do bad things.
2112 *trace = save_trace();
2115 print_circular_bug(&src_entry, target_entry, src, target);
2121 #ifdef CONFIG_LOCKDEP_SMALL
2123 * Check that the dependency graph starting at <src> can lead to
2124 * <target> or not. If it can, <src> -> <target> dependency is already
2127 * Return BFS_RMATCH if it does, or BFS_RMATCH if it does not, return BFS_E* if
2128 * any error appears in the bfs search.
2130 static noinline enum bfs_result
2131 check_redundant(struct held_lock *src, struct held_lock *target)
2133 enum bfs_result ret;
2134 struct lock_list *target_entry;
2135 struct lock_list src_entry;
2137 bfs_init_root(&src_entry, src);
2139 * Special setup for check_redundant().
2141 * To report redundant, we need to find a strong dependency path that
2142 * is equal to or stronger than <src> -> <target>. So if <src> is E,
2143 * we need to let __bfs() only search for a path starting at a -(E*)->,
2144 * we achieve this by setting the initial node's ->only_xr to true in
2145 * that case. And if <prev> is S, we set initial ->only_xr to false
2146 * because both -(S*)-> (equal) and -(E*)-> (stronger) are redundant.
2148 src_entry.only_xr = src->read == 0;
2150 debug_atomic_inc(nr_redundant_checks);
2152 ret = check_path(target, &src_entry, hlock_equal, &target_entry);
2154 if (ret == BFS_RMATCH)
2155 debug_atomic_inc(nr_redundant);
2161 #ifdef CONFIG_TRACE_IRQFLAGS
2164 * Forwards and backwards subgraph searching, for the purposes of
2165 * proving that two subgraphs can be connected by a new dependency
2166 * without creating any illegal irq-safe -> irq-unsafe lock dependency.
2168 * A irq safe->unsafe deadlock happens with the following conditions:
2170 * 1) We have a strong dependency path A -> ... -> B
2172 * 2) and we have ENABLED_IRQ usage of B and USED_IN_IRQ usage of A, therefore
2173 * irq can create a new dependency B -> A (consider the case that a holder
2174 * of B gets interrupted by an irq whose handler will try to acquire A).
2176 * 3) the dependency circle A -> ... -> B -> A we get from 1) and 2) is a
2179 * For the usage bits of B:
2180 * a) if A -> B is -(*N)->, then B -> A could be any type, so any
2181 * ENABLED_IRQ usage suffices.
2182 * b) if A -> B is -(*R)->, then B -> A must be -(E*)->, so only
2183 * ENABLED_IRQ_*_READ usage suffices.
2185 * For the usage bits of A:
2186 * c) if A -> B is -(E*)->, then B -> A could be any type, so any
2187 * USED_IN_IRQ usage suffices.
2188 * d) if A -> B is -(S*)->, then B -> A must be -(*N)->, so only
2189 * USED_IN_IRQ_*_READ usage suffices.
2193 * There is a strong dependency path in the dependency graph: A -> B, and now
2194 * we need to decide which usage bit of A should be accumulated to detect
2195 * safe->unsafe bugs.
2197 * Note that usage_accumulate() is used in backwards search, so ->only_xr
2198 * stands for whether A -> B only has -(S*)-> (in this case ->only_xr is true).
2200 * As above, if only_xr is false, which means A -> B has -(E*)-> dependency
2201 * path, any usage of A should be considered. Otherwise, we should only
2202 * consider _READ usage.
2204 static inline bool usage_accumulate(struct lock_list *entry, void *mask)
2206 if (!entry->only_xr)
2207 *(unsigned long *)mask |= entry->class->usage_mask;
2208 else /* Mask out _READ usage bits */
2209 *(unsigned long *)mask |= (entry->class->usage_mask & LOCKF_IRQ);
2215 * There is a strong dependency path in the dependency graph: A -> B, and now
2216 * we need to decide which usage bit of B conflicts with the usage bits of A,
2217 * i.e. which usage bit of B may introduce safe->unsafe deadlocks.
2219 * As above, if only_xr is false, which means A -> B has -(*N)-> dependency
2220 * path, any usage of B should be considered. Otherwise, we should only
2221 * consider _READ usage.
2223 static inline bool usage_match(struct lock_list *entry, void *mask)
2225 if (!entry->only_xr)
2226 return !!(entry->class->usage_mask & *(unsigned long *)mask);
2227 else /* Mask out _READ usage bits */
2228 return !!((entry->class->usage_mask & LOCKF_IRQ) & *(unsigned long *)mask);
2232 * Find a node in the forwards-direction dependency sub-graph starting
2233 * at @root->class that matches @bit.
2235 * Return BFS_MATCH if such a node exists in the subgraph, and put that node
2236 * into *@target_entry.
2238 static enum bfs_result
2239 find_usage_forwards(struct lock_list *root, unsigned long usage_mask,
2240 struct lock_list **target_entry)
2242 enum bfs_result result;
2244 debug_atomic_inc(nr_find_usage_forwards_checks);
2246 result = __bfs_forwards(root, &usage_mask, usage_match, target_entry);
2252 * Find a node in the backwards-direction dependency sub-graph starting
2253 * at @root->class that matches @bit.
2255 static enum bfs_result
2256 find_usage_backwards(struct lock_list *root, unsigned long usage_mask,
2257 struct lock_list **target_entry)
2259 enum bfs_result result;
2261 debug_atomic_inc(nr_find_usage_backwards_checks);
2263 result = __bfs_backwards(root, &usage_mask, usage_match, target_entry);
2268 static void print_lock_class_header(struct lock_class *class, int depth)
2272 printk("%*s->", depth, "");
2273 print_lock_name(class);
2274 #ifdef CONFIG_DEBUG_LOCKDEP
2275 printk(KERN_CONT " ops: %lu", debug_class_ops_read(class));
2277 printk(KERN_CONT " {\n");
2279 for (bit = 0; bit < LOCK_TRACE_STATES; bit++) {
2280 if (class->usage_mask & (1 << bit)) {
2283 len += printk("%*s %s", depth, "", usage_str[bit]);
2284 len += printk(KERN_CONT " at:\n");
2285 print_lock_trace(class->usage_traces[bit], len);
2288 printk("%*s }\n", depth, "");
2290 printk("%*s ... key at: [<%px>] %pS\n",
2291 depth, "", class->key, class->key);
2295 * printk the shortest lock dependencies from @start to @end in reverse order:
2298 print_shortest_lock_dependencies(struct lock_list *leaf,
2299 struct lock_list *root)
2301 struct lock_list *entry = leaf;
2304 /*compute depth from generated tree by BFS*/
2305 depth = get_lock_depth(leaf);
2308 print_lock_class_header(entry->class, depth);
2309 printk("%*s ... acquired at:\n", depth, "");
2310 print_lock_trace(entry->trace, 2);
2313 if (depth == 0 && (entry != root)) {
2314 printk("lockdep:%s bad path found in chain graph\n", __func__);
2318 entry = get_lock_parent(entry);
2320 } while (entry && (depth >= 0));
2324 print_irq_lock_scenario(struct lock_list *safe_entry,
2325 struct lock_list *unsafe_entry,
2326 struct lock_class *prev_class,
2327 struct lock_class *next_class)
2329 struct lock_class *safe_class = safe_entry->class;
2330 struct lock_class *unsafe_class = unsafe_entry->class;
2331 struct lock_class *middle_class = prev_class;
2333 if (middle_class == safe_class)
2334 middle_class = next_class;
2337 * A direct locking problem where unsafe_class lock is taken
2338 * directly by safe_class lock, then all we need to show
2339 * is the deadlock scenario, as it is obvious that the
2340 * unsafe lock is taken under the safe lock.
2342 * But if there is a chain instead, where the safe lock takes
2343 * an intermediate lock (middle_class) where this lock is
2344 * not the same as the safe lock, then the lock chain is
2345 * used to describe the problem. Otherwise we would need
2346 * to show a different CPU case for each link in the chain
2347 * from the safe_class lock to the unsafe_class lock.
2349 if (middle_class != unsafe_class) {
2350 printk("Chain exists of:\n ");
2351 __print_lock_name(safe_class);
2352 printk(KERN_CONT " --> ");
2353 __print_lock_name(middle_class);
2354 printk(KERN_CONT " --> ");
2355 __print_lock_name(unsafe_class);
2356 printk(KERN_CONT "\n\n");
2359 printk(" Possible interrupt unsafe locking scenario:\n\n");
2360 printk(" CPU0 CPU1\n");
2361 printk(" ---- ----\n");
2363 __print_lock_name(unsafe_class);
2364 printk(KERN_CONT ");\n");
2365 printk(" local_irq_disable();\n");
2367 __print_lock_name(safe_class);
2368 printk(KERN_CONT ");\n");
2370 __print_lock_name(middle_class);
2371 printk(KERN_CONT ");\n");
2372 printk(" <Interrupt>\n");
2374 __print_lock_name(safe_class);
2375 printk(KERN_CONT ");\n");
2376 printk("\n *** DEADLOCK ***\n\n");
2380 print_bad_irq_dependency(struct task_struct *curr,
2381 struct lock_list *prev_root,
2382 struct lock_list *next_root,
2383 struct lock_list *backwards_entry,
2384 struct lock_list *forwards_entry,
2385 struct held_lock *prev,
2386 struct held_lock *next,
2387 enum lock_usage_bit bit1,
2388 enum lock_usage_bit bit2,
2389 const char *irqclass)
2391 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2395 pr_warn("=====================================================\n");
2396 pr_warn("WARNING: %s-safe -> %s-unsafe lock order detected\n",
2397 irqclass, irqclass);
2398 print_kernel_ident();
2399 pr_warn("-----------------------------------------------------\n");
2400 pr_warn("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
2401 curr->comm, task_pid_nr(curr),
2402 lockdep_hardirq_context(), hardirq_count() >> HARDIRQ_SHIFT,
2403 curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT,
2404 lockdep_hardirqs_enabled(),
2405 curr->softirqs_enabled);
2408 pr_warn("\nand this task is already holding:\n");
2410 pr_warn("which would create a new lock dependency:\n");
2411 print_lock_name(hlock_class(prev));
2413 print_lock_name(hlock_class(next));
2416 pr_warn("\nbut this new dependency connects a %s-irq-safe lock:\n",
2418 print_lock_name(backwards_entry->class);
2419 pr_warn("\n... which became %s-irq-safe at:\n", irqclass);
2421 print_lock_trace(backwards_entry->class->usage_traces[bit1], 1);
2423 pr_warn("\nto a %s-irq-unsafe lock:\n", irqclass);
2424 print_lock_name(forwards_entry->class);
2425 pr_warn("\n... which became %s-irq-unsafe at:\n", irqclass);
2428 print_lock_trace(forwards_entry->class->usage_traces[bit2], 1);
2430 pr_warn("\nother info that might help us debug this:\n\n");
2431 print_irq_lock_scenario(backwards_entry, forwards_entry,
2432 hlock_class(prev), hlock_class(next));
2434 lockdep_print_held_locks(curr);
2436 pr_warn("\nthe dependencies between %s-irq-safe lock and the holding lock:\n", irqclass);
2437 prev_root->trace = save_trace();
2438 if (!prev_root->trace)
2440 print_shortest_lock_dependencies(backwards_entry, prev_root);
2442 pr_warn("\nthe dependencies between the lock to be acquired");
2443 pr_warn(" and %s-irq-unsafe lock:\n", irqclass);
2444 next_root->trace = save_trace();
2445 if (!next_root->trace)
2447 print_shortest_lock_dependencies(forwards_entry, next_root);
2449 pr_warn("\nstack backtrace:\n");
2453 static const char *state_names[] = {
2454 #define LOCKDEP_STATE(__STATE) \
2455 __stringify(__STATE),
2456 #include "lockdep_states.h"
2457 #undef LOCKDEP_STATE
2460 static const char *state_rnames[] = {
2461 #define LOCKDEP_STATE(__STATE) \
2462 __stringify(__STATE)"-READ",
2463 #include "lockdep_states.h"
2464 #undef LOCKDEP_STATE
2467 static inline const char *state_name(enum lock_usage_bit bit)
2469 if (bit & LOCK_USAGE_READ_MASK)
2470 return state_rnames[bit >> LOCK_USAGE_DIR_MASK];
2472 return state_names[bit >> LOCK_USAGE_DIR_MASK];
2476 * The bit number is encoded like:
2478 * bit0: 0 exclusive, 1 read lock
2479 * bit1: 0 used in irq, 1 irq enabled
2482 static int exclusive_bit(int new_bit)
2484 int state = new_bit & LOCK_USAGE_STATE_MASK;
2485 int dir = new_bit & LOCK_USAGE_DIR_MASK;
2488 * keep state, bit flip the direction and strip read.
2490 return state | (dir ^ LOCK_USAGE_DIR_MASK);
2494 * Observe that when given a bitmask where each bitnr is encoded as above, a
2495 * right shift of the mask transforms the individual bitnrs as -1 and
2496 * conversely, a left shift transforms into +1 for the individual bitnrs.
2498 * So for all bits whose number have LOCK_ENABLED_* set (bitnr1 == 1), we can
2499 * create the mask with those bit numbers using LOCK_USED_IN_* (bitnr1 == 0)
2500 * instead by subtracting the bit number by 2, or shifting the mask right by 2.
2502 * Similarly, bitnr1 == 0 becomes bitnr1 == 1 by adding 2, or shifting left 2.
2504 * So split the mask (note that LOCKF_ENABLED_IRQ_ALL|LOCKF_USED_IN_IRQ_ALL is
2505 * all bits set) and recompose with bitnr1 flipped.
2507 static unsigned long invert_dir_mask(unsigned long mask)
2509 unsigned long excl = 0;
2512 excl |= (mask & LOCKF_ENABLED_IRQ_ALL) >> LOCK_USAGE_DIR_MASK;
2513 excl |= (mask & LOCKF_USED_IN_IRQ_ALL) << LOCK_USAGE_DIR_MASK;
2519 * Note that a LOCK_ENABLED_IRQ_*_READ usage and a LOCK_USED_IN_IRQ_*_READ
2520 * usage may cause deadlock too, for example:
2524 * write_lock(l1); <irq enabled>
2530 * , in above case, l1 will be marked as LOCK_USED_IN_IRQ_HARDIRQ_READ and l2
2531 * will marked as LOCK_ENABLE_IRQ_HARDIRQ_READ, and this is a possible
2534 * In fact, all of the following cases may cause deadlocks:
2536 * LOCK_USED_IN_IRQ_* -> LOCK_ENABLED_IRQ_*
2537 * LOCK_USED_IN_IRQ_*_READ -> LOCK_ENABLED_IRQ_*
2538 * LOCK_USED_IN_IRQ_* -> LOCK_ENABLED_IRQ_*_READ
2539 * LOCK_USED_IN_IRQ_*_READ -> LOCK_ENABLED_IRQ_*_READ
2541 * As a result, to calculate the "exclusive mask", first we invert the
2542 * direction (USED_IN/ENABLED) of the original mask, and 1) for all bits with
2543 * bitnr0 set (LOCK_*_READ), add those with bitnr0 cleared (LOCK_*). 2) for all
2544 * bits with bitnr0 cleared (LOCK_*_READ), add those with bitnr0 set (LOCK_*).
2546 static unsigned long exclusive_mask(unsigned long mask)
2548 unsigned long excl = invert_dir_mask(mask);
2550 excl |= (excl & LOCKF_IRQ_READ) >> LOCK_USAGE_READ_MASK;
2551 excl |= (excl & LOCKF_IRQ) << LOCK_USAGE_READ_MASK;
2557 * Retrieve the _possible_ original mask to which @mask is
2558 * exclusive. Ie: this is the opposite of exclusive_mask().
2559 * Note that 2 possible original bits can match an exclusive
2560 * bit: one has LOCK_USAGE_READ_MASK set, the other has it
2561 * cleared. So both are returned for each exclusive bit.
2563 static unsigned long original_mask(unsigned long mask)
2565 unsigned long excl = invert_dir_mask(mask);
2567 /* Include read in existing usages */
2568 excl |= (excl & LOCKF_IRQ_READ) >> LOCK_USAGE_READ_MASK;
2569 excl |= (excl & LOCKF_IRQ) << LOCK_USAGE_READ_MASK;
2575 * Find the first pair of bit match between an original
2576 * usage mask and an exclusive usage mask.
2578 static int find_exclusive_match(unsigned long mask,
2579 unsigned long excl_mask,
2580 enum lock_usage_bit *bitp,
2581 enum lock_usage_bit *excl_bitp)
2583 int bit, excl, excl_read;
2585 for_each_set_bit(bit, &mask, LOCK_USED) {
2587 * exclusive_bit() strips the read bit, however,
2588 * LOCK_ENABLED_IRQ_*_READ may cause deadlocks too, so we need
2589 * to search excl | LOCK_USAGE_READ_MASK as well.
2591 excl = exclusive_bit(bit);
2592 excl_read = excl | LOCK_USAGE_READ_MASK;
2593 if (excl_mask & lock_flag(excl)) {
2597 } else if (excl_mask & lock_flag(excl_read)) {
2599 *excl_bitp = excl_read;
2607 * Prove that the new dependency does not connect a hardirq-safe(-read)
2608 * lock with a hardirq-unsafe lock - to achieve this we search
2609 * the backwards-subgraph starting at <prev>, and the
2610 * forwards-subgraph starting at <next>:
2612 static int check_irq_usage(struct task_struct *curr, struct held_lock *prev,
2613 struct held_lock *next)
2615 unsigned long usage_mask = 0, forward_mask, backward_mask;
2616 enum lock_usage_bit forward_bit = 0, backward_bit = 0;
2617 struct lock_list *target_entry1;
2618 struct lock_list *target_entry;
2619 struct lock_list this, that;
2620 enum bfs_result ret;
2623 * Step 1: gather all hard/soft IRQs usages backward in an
2624 * accumulated usage mask.
2626 bfs_init_rootb(&this, prev);
2628 ret = __bfs_backwards(&this, &usage_mask, usage_accumulate, NULL);
2629 if (bfs_error(ret)) {
2634 usage_mask &= LOCKF_USED_IN_IRQ_ALL;
2639 * Step 2: find exclusive uses forward that match the previous
2640 * backward accumulated mask.
2642 forward_mask = exclusive_mask(usage_mask);
2644 bfs_init_root(&that, next);
2646 ret = find_usage_forwards(&that, forward_mask, &target_entry1);
2647 if (bfs_error(ret)) {
2651 if (ret == BFS_RNOMATCH)
2655 * Step 3: we found a bad match! Now retrieve a lock from the backward
2656 * list whose usage mask matches the exclusive usage mask from the
2657 * lock found on the forward list.
2659 backward_mask = original_mask(target_entry1->class->usage_mask);
2661 ret = find_usage_backwards(&this, backward_mask, &target_entry);
2662 if (bfs_error(ret)) {
2666 if (DEBUG_LOCKS_WARN_ON(ret == BFS_RNOMATCH))
2670 * Step 4: narrow down to a pair of incompatible usage bits
2673 ret = find_exclusive_match(target_entry->class->usage_mask,
2674 target_entry1->class->usage_mask,
2675 &backward_bit, &forward_bit);
2676 if (DEBUG_LOCKS_WARN_ON(ret == -1))
2679 print_bad_irq_dependency(curr, &this, &that,
2680 target_entry, target_entry1,
2682 backward_bit, forward_bit,
2683 state_name(backward_bit));
2690 static inline int check_irq_usage(struct task_struct *curr,
2691 struct held_lock *prev, struct held_lock *next)
2695 #endif /* CONFIG_TRACE_IRQFLAGS */
2697 static void inc_chains(int irq_context)
2699 if (irq_context & LOCK_CHAIN_HARDIRQ_CONTEXT)
2700 nr_hardirq_chains++;
2701 else if (irq_context & LOCK_CHAIN_SOFTIRQ_CONTEXT)
2702 nr_softirq_chains++;
2704 nr_process_chains++;
2707 static void dec_chains(int irq_context)
2709 if (irq_context & LOCK_CHAIN_HARDIRQ_CONTEXT)
2710 nr_hardirq_chains--;
2711 else if (irq_context & LOCK_CHAIN_SOFTIRQ_CONTEXT)
2712 nr_softirq_chains--;
2714 nr_process_chains--;
2718 print_deadlock_scenario(struct held_lock *nxt, struct held_lock *prv)
2720 struct lock_class *next = hlock_class(nxt);
2721 struct lock_class *prev = hlock_class(prv);
2723 printk(" Possible unsafe locking scenario:\n\n");
2727 __print_lock_name(prev);
2728 printk(KERN_CONT ");\n");
2730 __print_lock_name(next);
2731 printk(KERN_CONT ");\n");
2732 printk("\n *** DEADLOCK ***\n\n");
2733 printk(" May be due to missing lock nesting notation\n\n");
2737 print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
2738 struct held_lock *next)
2740 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2744 pr_warn("============================================\n");
2745 pr_warn("WARNING: possible recursive locking detected\n");
2746 print_kernel_ident();
2747 pr_warn("--------------------------------------------\n");
2748 pr_warn("%s/%d is trying to acquire lock:\n",
2749 curr->comm, task_pid_nr(curr));
2751 pr_warn("\nbut task is already holding lock:\n");
2754 pr_warn("\nother info that might help us debug this:\n");
2755 print_deadlock_scenario(next, prev);
2756 lockdep_print_held_locks(curr);
2758 pr_warn("\nstack backtrace:\n");
2763 * Check whether we are holding such a class already.
2765 * (Note that this has to be done separately, because the graph cannot
2766 * detect such classes of deadlocks.)
2768 * Returns: 0 on deadlock detected, 1 on OK, 2 if another lock with the same
2769 * lock class is held but nest_lock is also held, i.e. we rely on the
2770 * nest_lock to avoid the deadlock.
2773 check_deadlock(struct task_struct *curr, struct held_lock *next)
2775 struct held_lock *prev;
2776 struct held_lock *nest = NULL;
2779 for (i = 0; i < curr->lockdep_depth; i++) {
2780 prev = curr->held_locks + i;
2782 if (prev->instance == next->nest_lock)
2785 if (hlock_class(prev) != hlock_class(next))
2789 * Allow read-after-read recursion of the same
2790 * lock class (i.e. read_lock(lock)+read_lock(lock)):
2792 if ((next->read == 2) && prev->read)
2796 * We're holding the nest_lock, which serializes this lock's
2797 * nesting behaviour.
2802 print_deadlock_bug(curr, prev, next);
2809 * There was a chain-cache miss, and we are about to add a new dependency
2810 * to a previous lock. We validate the following rules:
2812 * - would the adding of the <prev> -> <next> dependency create a
2813 * circular dependency in the graph? [== circular deadlock]
2815 * - does the new prev->next dependency connect any hardirq-safe lock
2816 * (in the full backwards-subgraph starting at <prev>) with any
2817 * hardirq-unsafe lock (in the full forwards-subgraph starting at
2818 * <next>)? [== illegal lock inversion with hardirq contexts]
2820 * - does the new prev->next dependency connect any softirq-safe lock
2821 * (in the full backwards-subgraph starting at <prev>) with any
2822 * softirq-unsafe lock (in the full forwards-subgraph starting at
2823 * <next>)? [== illegal lock inversion with softirq contexts]
2825 * any of these scenarios could lead to a deadlock.
2827 * Then if all the validations pass, we add the forwards and backwards
2831 check_prev_add(struct task_struct *curr, struct held_lock *prev,
2832 struct held_lock *next, u16 distance,
2833 struct lock_trace **const trace)
2835 struct lock_list *entry;
2836 enum bfs_result ret;
2838 if (!hlock_class(prev)->key || !hlock_class(next)->key) {
2840 * The warning statements below may trigger a use-after-free
2841 * of the class name. It is better to trigger a use-after free
2842 * and to have the class name most of the time instead of not
2843 * having the class name available.
2845 WARN_ONCE(!debug_locks_silent && !hlock_class(prev)->key,
2846 "Detected use-after-free of lock class %px/%s\n",
2848 hlock_class(prev)->name);
2849 WARN_ONCE(!debug_locks_silent && !hlock_class(next)->key,
2850 "Detected use-after-free of lock class %px/%s\n",
2852 hlock_class(next)->name);
2857 * Prove that the new <prev> -> <next> dependency would not
2858 * create a circular dependency in the graph. (We do this by
2859 * a breadth-first search into the graph starting at <next>,
2860 * and check whether we can reach <prev>.)
2862 * The search is limited by the size of the circular queue (i.e.,
2863 * MAX_CIRCULAR_QUEUE_SIZE) which keeps track of a breadth of nodes
2864 * in the graph whose neighbours are to be checked.
2866 ret = check_noncircular(next, prev, trace);
2867 if (unlikely(bfs_error(ret) || ret == BFS_RMATCH))
2870 if (!check_irq_usage(curr, prev, next))
2874 * Is the <prev> -> <next> dependency already present?
2876 * (this may occur even though this is a new chain: consider
2877 * e.g. the L1 -> L2 -> L3 -> L4 and the L5 -> L1 -> L2 -> L3
2878 * chains - the second one will be new, but L1 already has
2879 * L2 added to its dependency list, due to the first chain.)
2881 list_for_each_entry(entry, &hlock_class(prev)->locks_after, entry) {
2882 if (entry->class == hlock_class(next)) {
2884 entry->distance = 1;
2885 entry->dep |= calc_dep(prev, next);
2888 * Also, update the reverse dependency in @next's
2889 * ->locks_before list.
2891 * Here we reuse @entry as the cursor, which is fine
2892 * because we won't go to the next iteration of the
2895 * For normal cases, we return in the inner loop.
2897 * If we fail to return, we have inconsistency, i.e.
2898 * <prev>::locks_after contains <next> while
2899 * <next>::locks_before doesn't contain <prev>. In
2900 * that case, we return after the inner and indicate
2901 * something is wrong.
2903 list_for_each_entry(entry, &hlock_class(next)->locks_before, entry) {
2904 if (entry->class == hlock_class(prev)) {
2906 entry->distance = 1;
2907 entry->dep |= calc_depb(prev, next);
2912 /* <prev> is not found in <next>::locks_before */
2917 #ifdef CONFIG_LOCKDEP_SMALL
2919 * Is the <prev> -> <next> link redundant?
2921 ret = check_redundant(prev, next);
2924 else if (ret == BFS_RMATCH)
2929 *trace = save_trace();
2935 * Ok, all validations passed, add the new lock
2936 * to the previous lock's dependency list:
2938 ret = add_lock_to_list(hlock_class(next), hlock_class(prev),
2939 &hlock_class(prev)->locks_after,
2940 next->acquire_ip, distance,
2941 calc_dep(prev, next),
2947 ret = add_lock_to_list(hlock_class(prev), hlock_class(next),
2948 &hlock_class(next)->locks_before,
2949 next->acquire_ip, distance,
2950 calc_depb(prev, next),
2959 * Add the dependency to all directly-previous locks that are 'relevant'.
2960 * The ones that are relevant are (in increasing distance from curr):
2961 * all consecutive trylock entries and the final non-trylock entry - or
2962 * the end of this context's lock-chain - whichever comes first.
2965 check_prevs_add(struct task_struct *curr, struct held_lock *next)
2967 struct lock_trace *trace = NULL;
2968 int depth = curr->lockdep_depth;
2969 struct held_lock *hlock;
2974 * Depth must not be zero for a non-head lock:
2979 * At least two relevant locks must exist for this
2982 if (curr->held_locks[depth].irq_context !=
2983 curr->held_locks[depth-1].irq_context)
2987 u16 distance = curr->lockdep_depth - depth + 1;
2988 hlock = curr->held_locks + depth - 1;
2991 int ret = check_prev_add(curr, hlock, next, distance, &trace);
2996 * Stop after the first non-trylock entry,
2997 * as non-trylock entries have added their
2998 * own direct dependencies already, so this
2999 * lock is connected to them indirectly:
3001 if (!hlock->trylock)
3007 * End of lock-stack?
3012 * Stop the search if we cross into another context:
3014 if (curr->held_locks[depth].irq_context !=
3015 curr->held_locks[depth-1].irq_context)
3020 if (!debug_locks_off_graph_unlock())
3024 * Clearly we all shouldn't be here, but since we made it we
3025 * can reliable say we messed up our state. See the above two
3026 * gotos for reasons why we could possibly end up here.
3033 struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
3034 static DECLARE_BITMAP(lock_chains_in_use, MAX_LOCKDEP_CHAINS);
3035 static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
3036 unsigned long nr_zapped_lock_chains;
3037 unsigned int nr_free_chain_hlocks; /* Free chain_hlocks in buckets */
3038 unsigned int nr_lost_chain_hlocks; /* Lost chain_hlocks */
3039 unsigned int nr_large_chain_blocks; /* size > MAX_CHAIN_BUCKETS */
3042 * The first 2 chain_hlocks entries in the chain block in the bucket
3043 * list contains the following meta data:
3046 * Bit 15 - always set to 1 (it is not a class index)
3047 * Bits 0-14 - upper 15 bits of the next block index
3048 * entry[1] - lower 16 bits of next block index
3050 * A next block index of all 1 bits means it is the end of the list.
3052 * On the unsized bucket (bucket-0), the 3rd and 4th entries contain
3053 * the chain block size:
3055 * entry[2] - upper 16 bits of the chain block size
3056 * entry[3] - lower 16 bits of the chain block size
3058 #define MAX_CHAIN_BUCKETS 16
3059 #define CHAIN_BLK_FLAG (1U << 15)
3060 #define CHAIN_BLK_LIST_END 0xFFFFU
3062 static int chain_block_buckets[MAX_CHAIN_BUCKETS];
3064 static inline int size_to_bucket(int size)
3066 if (size > MAX_CHAIN_BUCKETS)
3073 * Iterate all the chain blocks in a bucket.
3075 #define for_each_chain_block(bucket, prev, curr) \
3076 for ((prev) = -1, (curr) = chain_block_buckets[bucket]; \
3078 (prev) = (curr), (curr) = chain_block_next(curr))
3083 static inline int chain_block_next(int offset)
3085 int next = chain_hlocks[offset];
3087 WARN_ON_ONCE(!(next & CHAIN_BLK_FLAG));
3089 if (next == CHAIN_BLK_LIST_END)
3092 next &= ~CHAIN_BLK_FLAG;
3094 next |= chain_hlocks[offset + 1];
3102 static inline int chain_block_size(int offset)
3104 return (chain_hlocks[offset + 2] << 16) | chain_hlocks[offset + 3];
3107 static inline void init_chain_block(int offset, int next, int bucket, int size)
3109 chain_hlocks[offset] = (next >> 16) | CHAIN_BLK_FLAG;
3110 chain_hlocks[offset + 1] = (u16)next;
3112 if (size && !bucket) {
3113 chain_hlocks[offset + 2] = size >> 16;
3114 chain_hlocks[offset + 3] = (u16)size;
3118 static inline void add_chain_block(int offset, int size)
3120 int bucket = size_to_bucket(size);
3121 int next = chain_block_buckets[bucket];
3124 if (unlikely(size < 2)) {
3126 * We can't store single entries on the freelist. Leak them.
3128 * One possible way out would be to uniquely mark them, other
3129 * than with CHAIN_BLK_FLAG, such that we can recover them when
3130 * the block before it is re-added.
3133 nr_lost_chain_hlocks++;
3137 nr_free_chain_hlocks += size;
3139 nr_large_chain_blocks++;
3142 * Variable sized, sort large to small.
3144 for_each_chain_block(0, prev, curr) {
3145 if (size >= chain_block_size(curr))
3148 init_chain_block(offset, curr, 0, size);
3150 chain_block_buckets[0] = offset;
3152 init_chain_block(prev, offset, 0, 0);
3156 * Fixed size, add to head.
3158 init_chain_block(offset, next, bucket, size);
3159 chain_block_buckets[bucket] = offset;
3163 * Only the first block in the list can be deleted.
3165 * For the variable size bucket[0], the first block (the largest one) is
3166 * returned, broken up and put back into the pool. So if a chain block of
3167 * length > MAX_CHAIN_BUCKETS is ever used and zapped, it will just be
3168 * queued up after the primordial chain block and never be used until the
3169 * hlock entries in the primordial chain block is almost used up. That
3170 * causes fragmentation and reduce allocation efficiency. That can be
3171 * monitored by looking at the "large chain blocks" number in lockdep_stats.
3173 static inline void del_chain_block(int bucket, int size, int next)
3175 nr_free_chain_hlocks -= size;
3176 chain_block_buckets[bucket] = next;
3179 nr_large_chain_blocks--;
3182 static void init_chain_block_buckets(void)
3186 for (i = 0; i < MAX_CHAIN_BUCKETS; i++)
3187 chain_block_buckets[i] = -1;
3189 add_chain_block(0, ARRAY_SIZE(chain_hlocks));
3193 * Return offset of a chain block of the right size or -1 if not found.
3195 * Fairly simple worst-fit allocator with the addition of a number of size
3196 * specific free lists.
3198 static int alloc_chain_hlocks(int req)
3200 int bucket, curr, size;
3203 * We rely on the MSB to act as an escape bit to denote freelist
3204 * pointers. Make sure this bit isn't set in 'normal' class_idx usage.
3206 BUILD_BUG_ON((MAX_LOCKDEP_KEYS-1) & CHAIN_BLK_FLAG);
3208 init_data_structures_once();
3210 if (nr_free_chain_hlocks < req)
3214 * We require a minimum of 2 (u16) entries to encode a freelist
3218 bucket = size_to_bucket(req);
3219 curr = chain_block_buckets[bucket];
3223 del_chain_block(bucket, req, chain_block_next(curr));
3227 curr = chain_block_buckets[0];
3231 * The variable sized freelist is sorted by size; the first entry is
3232 * the largest. Use it if it fits.
3235 size = chain_block_size(curr);
3236 if (likely(size >= req)) {
3237 del_chain_block(0, size, chain_block_next(curr));
3238 add_chain_block(curr + req, size - req);
3244 * Last resort, split a block in a larger sized bucket.
3246 for (size = MAX_CHAIN_BUCKETS; size > req; size--) {
3247 bucket = size_to_bucket(size);
3248 curr = chain_block_buckets[bucket];
3252 del_chain_block(bucket, size, chain_block_next(curr));
3253 add_chain_block(curr + req, size - req);
3260 static inline void free_chain_hlocks(int base, int size)
3262 add_chain_block(base, max(size, 2));
3265 struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
3267 u16 chain_hlock = chain_hlocks[chain->base + i];
3268 unsigned int class_idx = chain_hlock_class_idx(chain_hlock);
3270 return lock_classes + class_idx - 1;
3274 * Returns the index of the first held_lock of the current chain
3276 static inline int get_first_held_lock(struct task_struct *curr,
3277 struct held_lock *hlock)
3280 struct held_lock *hlock_curr;
3282 for (i = curr->lockdep_depth - 1; i >= 0; i--) {
3283 hlock_curr = curr->held_locks + i;
3284 if (hlock_curr->irq_context != hlock->irq_context)
3292 #ifdef CONFIG_DEBUG_LOCKDEP
3294 * Returns the next chain_key iteration
3296 static u64 print_chain_key_iteration(u16 hlock_id, u64 chain_key)
3298 u64 new_chain_key = iterate_chain_key(chain_key, hlock_id);
3300 printk(" hlock_id:%d -> chain_key:%016Lx",
3301 (unsigned int)hlock_id,
3302 (unsigned long long)new_chain_key);
3303 return new_chain_key;
3307 print_chain_keys_held_locks(struct task_struct *curr, struct held_lock *hlock_next)
3309 struct held_lock *hlock;
3310 u64 chain_key = INITIAL_CHAIN_KEY;
3311 int depth = curr->lockdep_depth;
3312 int i = get_first_held_lock(curr, hlock_next);
3314 printk("depth: %u (irq_context %u)\n", depth - i + 1,
3315 hlock_next->irq_context);
3316 for (; i < depth; i++) {
3317 hlock = curr->held_locks + i;
3318 chain_key = print_chain_key_iteration(hlock_id(hlock), chain_key);
3323 print_chain_key_iteration(hlock_id(hlock_next), chain_key);
3324 print_lock(hlock_next);
3327 static void print_chain_keys_chain(struct lock_chain *chain)
3330 u64 chain_key = INITIAL_CHAIN_KEY;
3333 printk("depth: %u\n", chain->depth);
3334 for (i = 0; i < chain->depth; i++) {
3335 hlock_id = chain_hlocks[chain->base + i];
3336 chain_key = print_chain_key_iteration(hlock_id, chain_key);
3338 print_lock_name(lock_classes + chain_hlock_class_idx(hlock_id) - 1);
3343 static void print_collision(struct task_struct *curr,
3344 struct held_lock *hlock_next,
3345 struct lock_chain *chain)
3348 pr_warn("============================\n");
3349 pr_warn("WARNING: chain_key collision\n");
3350 print_kernel_ident();
3351 pr_warn("----------------------------\n");
3352 pr_warn("%s/%d: ", current->comm, task_pid_nr(current));
3353 pr_warn("Hash chain already cached but the contents don't match!\n");
3355 pr_warn("Held locks:");
3356 print_chain_keys_held_locks(curr, hlock_next);
3358 pr_warn("Locks in cached chain:");
3359 print_chain_keys_chain(chain);
3361 pr_warn("\nstack backtrace:\n");
3367 * Checks whether the chain and the current held locks are consistent
3368 * in depth and also in content. If they are not it most likely means
3369 * that there was a collision during the calculation of the chain_key.
3370 * Returns: 0 not passed, 1 passed
3372 static int check_no_collision(struct task_struct *curr,
3373 struct held_lock *hlock,
3374 struct lock_chain *chain)
3376 #ifdef CONFIG_DEBUG_LOCKDEP
3379 i = get_first_held_lock(curr, hlock);
3381 if (DEBUG_LOCKS_WARN_ON(chain->depth != curr->lockdep_depth - (i - 1))) {
3382 print_collision(curr, hlock, chain);
3386 for (j = 0; j < chain->depth - 1; j++, i++) {
3387 id = hlock_id(&curr->held_locks[i]);
3389 if (DEBUG_LOCKS_WARN_ON(chain_hlocks[chain->base + j] != id)) {
3390 print_collision(curr, hlock, chain);
3399 * Given an index that is >= -1, return the index of the next lock chain.
3400 * Return -2 if there is no next lock chain.
3402 long lockdep_next_lockchain(long i)
3404 i = find_next_bit(lock_chains_in_use, ARRAY_SIZE(lock_chains), i + 1);
3405 return i < ARRAY_SIZE(lock_chains) ? i : -2;
3408 unsigned long lock_chain_count(void)
3410 return bitmap_weight(lock_chains_in_use, ARRAY_SIZE(lock_chains));
3413 /* Must be called with the graph lock held. */
3414 static struct lock_chain *alloc_lock_chain(void)
3416 int idx = find_first_zero_bit(lock_chains_in_use,
3417 ARRAY_SIZE(lock_chains));
3419 if (unlikely(idx >= ARRAY_SIZE(lock_chains)))
3421 __set_bit(idx, lock_chains_in_use);
3422 return lock_chains + idx;
3426 * Adds a dependency chain into chain hashtable. And must be called with
3429 * Return 0 if fail, and graph_lock is released.
3430 * Return 1 if succeed, with graph_lock held.
3432 static inline int add_chain_cache(struct task_struct *curr,
3433 struct held_lock *hlock,
3436 struct hlist_head *hash_head = chainhashentry(chain_key);
3437 struct lock_chain *chain;
3441 * The caller must hold the graph lock, ensure we've got IRQs
3442 * disabled to make this an IRQ-safe lock.. for recursion reasons
3443 * lockdep won't complain about its own locking errors.
3445 if (lockdep_assert_locked())
3448 chain = alloc_lock_chain();
3450 if (!debug_locks_off_graph_unlock())
3453 print_lockdep_off("BUG: MAX_LOCKDEP_CHAINS too low!");
3457 chain->chain_key = chain_key;
3458 chain->irq_context = hlock->irq_context;
3459 i = get_first_held_lock(curr, hlock);
3460 chain->depth = curr->lockdep_depth + 1 - i;
3462 BUILD_BUG_ON((1UL << 24) <= ARRAY_SIZE(chain_hlocks));
3463 BUILD_BUG_ON((1UL << 6) <= ARRAY_SIZE(curr->held_locks));
3464 BUILD_BUG_ON((1UL << 8*sizeof(chain_hlocks[0])) <= ARRAY_SIZE(lock_classes));
3466 j = alloc_chain_hlocks(chain->depth);
3468 if (!debug_locks_off_graph_unlock())
3471 print_lockdep_off("BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!");
3477 for (j = 0; j < chain->depth - 1; j++, i++) {
3478 int lock_id = hlock_id(curr->held_locks + i);
3480 chain_hlocks[chain->base + j] = lock_id;
3482 chain_hlocks[chain->base + j] = hlock_id(hlock);
3483 hlist_add_head_rcu(&chain->entry, hash_head);
3484 debug_atomic_inc(chain_lookup_misses);
3485 inc_chains(chain->irq_context);
3491 * Look up a dependency chain. Must be called with either the graph lock or
3492 * the RCU read lock held.
3494 static inline struct lock_chain *lookup_chain_cache(u64 chain_key)
3496 struct hlist_head *hash_head = chainhashentry(chain_key);
3497 struct lock_chain *chain;
3499 hlist_for_each_entry_rcu(chain, hash_head, entry) {
3500 if (READ_ONCE(chain->chain_key) == chain_key) {
3501 debug_atomic_inc(chain_lookup_hits);
3509 * If the key is not present yet in dependency chain cache then
3510 * add it and return 1 - in this case the new dependency chain is
3511 * validated. If the key is already hashed, return 0.
3512 * (On return with 1 graph_lock is held.)
3514 static inline int lookup_chain_cache_add(struct task_struct *curr,
3515 struct held_lock *hlock,
3518 struct lock_class *class = hlock_class(hlock);
3519 struct lock_chain *chain = lookup_chain_cache(chain_key);
3523 if (!check_no_collision(curr, hlock, chain))
3526 if (very_verbose(class)) {
3527 printk("\nhash chain already cached, key: "
3528 "%016Lx tail class: [%px] %s\n",
3529 (unsigned long long)chain_key,
3530 class->key, class->name);
3536 if (very_verbose(class)) {
3537 printk("\nnew hash chain, key: %016Lx tail class: [%px] %s\n",
3538 (unsigned long long)chain_key, class->key, class->name);
3545 * We have to walk the chain again locked - to avoid duplicates:
3547 chain = lookup_chain_cache(chain_key);
3553 if (!add_chain_cache(curr, hlock, chain_key))
3559 static int validate_chain(struct task_struct *curr,
3560 struct held_lock *hlock,
3561 int chain_head, u64 chain_key)
3564 * Trylock needs to maintain the stack of held locks, but it
3565 * does not add new dependencies, because trylock can be done
3568 * We look up the chain_key and do the O(N^2) check and update of
3569 * the dependencies only if this is a new dependency chain.
3570 * (If lookup_chain_cache_add() return with 1 it acquires
3571 * graph_lock for us)
3573 if (!hlock->trylock && hlock->check &&
3574 lookup_chain_cache_add(curr, hlock, chain_key)) {
3576 * Check whether last held lock:
3578 * - is irq-safe, if this lock is irq-unsafe
3579 * - is softirq-safe, if this lock is hardirq-unsafe
3581 * And check whether the new lock's dependency graph
3582 * could lead back to the previous lock:
3584 * - within the current held-lock stack
3585 * - across our accumulated lock dependency records
3587 * any of these scenarios could lead to a deadlock.
3590 * The simple case: does the current hold the same lock
3593 int ret = check_deadlock(curr, hlock);
3598 * Add dependency only if this lock is not the head
3599 * of the chain, and if the new lock introduces no more
3600 * lock dependency (because we already hold a lock with the
3601 * same lock class) nor deadlock (because the nest_lock
3602 * serializes nesting locks), see the comments for
3605 if (!chain_head && ret != 2) {
3606 if (!check_prevs_add(curr, hlock))
3612 /* after lookup_chain_cache_add(): */
3613 if (unlikely(!debug_locks))
3620 static inline int validate_chain(struct task_struct *curr,
3621 struct held_lock *hlock,
3622 int chain_head, u64 chain_key)
3627 static void init_chain_block_buckets(void) { }
3628 #endif /* CONFIG_PROVE_LOCKING */
3631 * We are building curr_chain_key incrementally, so double-check
3632 * it from scratch, to make sure that it's done correctly:
3634 static void check_chain_key(struct task_struct *curr)
3636 #ifdef CONFIG_DEBUG_LOCKDEP
3637 struct held_lock *hlock, *prev_hlock = NULL;
3639 u64 chain_key = INITIAL_CHAIN_KEY;
3641 for (i = 0; i < curr->lockdep_depth; i++) {
3642 hlock = curr->held_locks + i;
3643 if (chain_key != hlock->prev_chain_key) {
3646 * We got mighty confused, our chain keys don't match
3647 * with what we expect, someone trample on our task state?
3649 WARN(1, "hm#1, depth: %u [%u], %016Lx != %016Lx\n",
3650 curr->lockdep_depth, i,
3651 (unsigned long long)chain_key,
3652 (unsigned long long)hlock->prev_chain_key);
3657 * hlock->class_idx can't go beyond MAX_LOCKDEP_KEYS, but is
3658 * it registered lock class index?
3660 if (DEBUG_LOCKS_WARN_ON(!test_bit(hlock->class_idx, lock_classes_in_use)))
3663 if (prev_hlock && (prev_hlock->irq_context !=
3664 hlock->irq_context))
3665 chain_key = INITIAL_CHAIN_KEY;
3666 chain_key = iterate_chain_key(chain_key, hlock_id(hlock));
3669 if (chain_key != curr->curr_chain_key) {
3672 * More smoking hash instead of calculating it, damn see these
3673 * numbers float.. I bet that a pink elephant stepped on my memory.
3675 WARN(1, "hm#2, depth: %u [%u], %016Lx != %016Lx\n",
3676 curr->lockdep_depth, i,
3677 (unsigned long long)chain_key,
3678 (unsigned long long)curr->curr_chain_key);
3683 #ifdef CONFIG_PROVE_LOCKING
3684 static int mark_lock(struct task_struct *curr, struct held_lock *this,
3685 enum lock_usage_bit new_bit);
3687 static void print_usage_bug_scenario(struct held_lock *lock)
3689 struct lock_class *class = hlock_class(lock);
3691 printk(" Possible unsafe locking scenario:\n\n");
3695 __print_lock_name(class);
3696 printk(KERN_CONT ");\n");
3697 printk(" <Interrupt>\n");
3699 __print_lock_name(class);
3700 printk(KERN_CONT ");\n");
3701 printk("\n *** DEADLOCK ***\n\n");
3705 print_usage_bug(struct task_struct *curr, struct held_lock *this,
3706 enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
3708 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
3712 pr_warn("================================\n");
3713 pr_warn("WARNING: inconsistent lock state\n");
3714 print_kernel_ident();
3715 pr_warn("--------------------------------\n");
3717 pr_warn("inconsistent {%s} -> {%s} usage.\n",
3718 usage_str[prev_bit], usage_str[new_bit]);
3720 pr_warn("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] takes:\n",
3721 curr->comm, task_pid_nr(curr),
3722 lockdep_hardirq_context(), hardirq_count() >> HARDIRQ_SHIFT,
3723 lockdep_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT,
3724 lockdep_hardirqs_enabled(),
3725 lockdep_softirqs_enabled(curr));
3728 pr_warn("{%s} state was registered at:\n", usage_str[prev_bit]);
3729 print_lock_trace(hlock_class(this)->usage_traces[prev_bit], 1);
3731 print_irqtrace_events(curr);
3732 pr_warn("\nother info that might help us debug this:\n");
3733 print_usage_bug_scenario(this);
3735 lockdep_print_held_locks(curr);
3737 pr_warn("\nstack backtrace:\n");
3742 * Print out an error if an invalid bit is set:
3745 valid_state(struct task_struct *curr, struct held_lock *this,
3746 enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit)
3748 if (unlikely(hlock_class(this)->usage_mask & (1 << bad_bit))) {
3749 print_usage_bug(curr, this, bad_bit, new_bit);
3757 * print irq inversion bug:
3760 print_irq_inversion_bug(struct task_struct *curr,
3761 struct lock_list *root, struct lock_list *other,
3762 struct held_lock *this, int forwards,
3763 const char *irqclass)
3765 struct lock_list *entry = other;
3766 struct lock_list *middle = NULL;
3769 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
3773 pr_warn("========================================================\n");
3774 pr_warn("WARNING: possible irq lock inversion dependency detected\n");
3775 print_kernel_ident();
3776 pr_warn("--------------------------------------------------------\n");
3777 pr_warn("%s/%d just changed the state of lock:\n",
3778 curr->comm, task_pid_nr(curr));
3781 pr_warn("but this lock took another, %s-unsafe lock in the past:\n", irqclass);
3783 pr_warn("but this lock was taken by another, %s-safe lock in the past:\n", irqclass);
3784 print_lock_name(other->class);
3785 pr_warn("\n\nand interrupts could create inverse lock ordering between them.\n\n");
3787 pr_warn("\nother info that might help us debug this:\n");
3789 /* Find a middle lock (if one exists) */
3790 depth = get_lock_depth(other);
3792 if (depth == 0 && (entry != root)) {
3793 pr_warn("lockdep:%s bad path found in chain graph\n", __func__);
3797 entry = get_lock_parent(entry);
3799 } while (entry && entry != root && (depth >= 0));
3801 print_irq_lock_scenario(root, other,
3802 middle ? middle->class : root->class, other->class);
3804 print_irq_lock_scenario(other, root,
3805 middle ? middle->class : other->class, root->class);
3807 lockdep_print_held_locks(curr);
3809 pr_warn("\nthe shortest dependencies between 2nd lock and 1st lock:\n");
3810 root->trace = save_trace();
3813 print_shortest_lock_dependencies(other, root);
3815 pr_warn("\nstack backtrace:\n");
3820 * Prove that in the forwards-direction subgraph starting at <this>
3821 * there is no lock matching <mask>:
3824 check_usage_forwards(struct task_struct *curr, struct held_lock *this,
3825 enum lock_usage_bit bit)
3827 enum bfs_result ret;
3828 struct lock_list root;
3829 struct lock_list *target_entry;
3830 enum lock_usage_bit read_bit = bit + LOCK_USAGE_READ_MASK;
3831 unsigned usage_mask = lock_flag(bit) | lock_flag(read_bit);
3833 bfs_init_root(&root, this);
3834 ret = find_usage_forwards(&root, usage_mask, &target_entry);
3835 if (bfs_error(ret)) {
3839 if (ret == BFS_RNOMATCH)
3842 /* Check whether write or read usage is the match */
3843 if (target_entry->class->usage_mask & lock_flag(bit)) {
3844 print_irq_inversion_bug(curr, &root, target_entry,
3845 this, 1, state_name(bit));
3847 print_irq_inversion_bug(curr, &root, target_entry,
3848 this, 1, state_name(read_bit));
3855 * Prove that in the backwards-direction subgraph starting at <this>
3856 * there is no lock matching <mask>:
3859 check_usage_backwards(struct task_struct *curr, struct held_lock *this,
3860 enum lock_usage_bit bit)
3862 enum bfs_result ret;
3863 struct lock_list root;
3864 struct lock_list *target_entry;
3865 enum lock_usage_bit read_bit = bit + LOCK_USAGE_READ_MASK;
3866 unsigned usage_mask = lock_flag(bit) | lock_flag(read_bit);
3868 bfs_init_rootb(&root, this);
3869 ret = find_usage_backwards(&root, usage_mask, &target_entry);
3870 if (bfs_error(ret)) {
3874 if (ret == BFS_RNOMATCH)
3877 /* Check whether write or read usage is the match */
3878 if (target_entry->class->usage_mask & lock_flag(bit)) {
3879 print_irq_inversion_bug(curr, &root, target_entry,
3880 this, 0, state_name(bit));
3882 print_irq_inversion_bug(curr, &root, target_entry,
3883 this, 0, state_name(read_bit));
3889 void print_irqtrace_events(struct task_struct *curr)
3891 const struct irqtrace_events *trace = &curr->irqtrace;
3893 printk("irq event stamp: %u\n", trace->irq_events);
3894 printk("hardirqs last enabled at (%u): [<%px>] %pS\n",
3895 trace->hardirq_enable_event, (void *)trace->hardirq_enable_ip,
3896 (void *)trace->hardirq_enable_ip);
3897 printk("hardirqs last disabled at (%u): [<%px>] %pS\n",
3898 trace->hardirq_disable_event, (void *)trace->hardirq_disable_ip,
3899 (void *)trace->hardirq_disable_ip);
3900 printk("softirqs last enabled at (%u): [<%px>] %pS\n",
3901 trace->softirq_enable_event, (void *)trace->softirq_enable_ip,
3902 (void *)trace->softirq_enable_ip);
3903 printk("softirqs last disabled at (%u): [<%px>] %pS\n",
3904 trace->softirq_disable_event, (void *)trace->softirq_disable_ip,
3905 (void *)trace->softirq_disable_ip);
3908 static int HARDIRQ_verbose(struct lock_class *class)
3911 return class_filter(class);
3916 static int SOFTIRQ_verbose(struct lock_class *class)
3919 return class_filter(class);
3924 static int (*state_verbose_f[])(struct lock_class *class) = {
3925 #define LOCKDEP_STATE(__STATE) \
3927 #include "lockdep_states.h"
3928 #undef LOCKDEP_STATE
3931 static inline int state_verbose(enum lock_usage_bit bit,
3932 struct lock_class *class)
3934 return state_verbose_f[bit >> LOCK_USAGE_DIR_MASK](class);
3937 typedef int (*check_usage_f)(struct task_struct *, struct held_lock *,
3938 enum lock_usage_bit bit, const char *name);
3941 mark_lock_irq(struct task_struct *curr, struct held_lock *this,
3942 enum lock_usage_bit new_bit)
3944 int excl_bit = exclusive_bit(new_bit);
3945 int read = new_bit & LOCK_USAGE_READ_MASK;
3946 int dir = new_bit & LOCK_USAGE_DIR_MASK;
3949 * Validate that this particular lock does not have conflicting
3952 if (!valid_state(curr, this, new_bit, excl_bit))
3956 * Check for read in write conflicts
3958 if (!read && !valid_state(curr, this, new_bit,
3959 excl_bit + LOCK_USAGE_READ_MASK))
3964 * Validate that the lock dependencies don't have conflicting usage
3969 * mark ENABLED has to look backwards -- to ensure no dependee
3970 * has USED_IN state, which, again, would allow recursion deadlocks.
3972 if (!check_usage_backwards(curr, this, excl_bit))
3976 * mark USED_IN has to look forwards -- to ensure no dependency
3977 * has ENABLED state, which would allow recursion deadlocks.
3979 if (!check_usage_forwards(curr, this, excl_bit))
3983 if (state_verbose(new_bit, hlock_class(this)))
3990 * Mark all held locks with a usage bit:
3993 mark_held_locks(struct task_struct *curr, enum lock_usage_bit base_bit)
3995 struct held_lock *hlock;
3998 for (i = 0; i < curr->lockdep_depth; i++) {
3999 enum lock_usage_bit hlock_bit = base_bit;
4000 hlock = curr->held_locks + i;
4003 hlock_bit += LOCK_USAGE_READ_MASK;
4005 BUG_ON(hlock_bit >= LOCK_USAGE_STATES);
4010 if (!mark_lock(curr, hlock, hlock_bit))
4018 * Hardirqs will be enabled:
4020 static void __trace_hardirqs_on_caller(void)
4022 struct task_struct *curr = current;
4025 * We are going to turn hardirqs on, so set the
4026 * usage bit for all held locks:
4028 if (!mark_held_locks(curr, LOCK_ENABLED_HARDIRQ))
4031 * If we have softirqs enabled, then set the usage
4032 * bit for all held locks. (disabled hardirqs prevented
4033 * this bit from being set before)
4035 if (curr->softirqs_enabled)
4036 mark_held_locks(curr, LOCK_ENABLED_SOFTIRQ);
4040 * lockdep_hardirqs_on_prepare - Prepare for enabling interrupts
4041 * @ip: Caller address
4043 * Invoked before a possible transition to RCU idle from exit to user or
4044 * guest mode. This ensures that all RCU operations are done before RCU
4045 * stops watching. After the RCU transition lockdep_hardirqs_on() has to be
4046 * invoked to set the final state.
4048 void lockdep_hardirqs_on_prepare(unsigned long ip)
4050 if (unlikely(!debug_locks))
4054 * NMIs do not (and cannot) track lock dependencies, nothing to do.
4056 if (unlikely(in_nmi()))
4059 if (unlikely(this_cpu_read(lockdep_recursion)))
4062 if (unlikely(lockdep_hardirqs_enabled())) {
4064 * Neither irq nor preemption are disabled here
4065 * so this is racy by nature but losing one hit
4066 * in a stat is not a big deal.
4068 __debug_atomic_inc(redundant_hardirqs_on);
4073 * We're enabling irqs and according to our state above irqs weren't
4074 * already enabled, yet we find the hardware thinks they are in fact
4075 * enabled.. someone messed up their IRQ state tracing.
4077 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4081 * See the fine text that goes along with this variable definition.
4083 if (DEBUG_LOCKS_WARN_ON(early_boot_irqs_disabled))
4087 * Can't allow enabling interrupts while in an interrupt handler,
4088 * that's general bad form and such. Recursion, limited stack etc..
4090 if (DEBUG_LOCKS_WARN_ON(lockdep_hardirq_context()))
4093 current->hardirq_chain_key = current->curr_chain_key;
4095 lockdep_recursion_inc();
4096 __trace_hardirqs_on_caller();
4097 lockdep_recursion_finish();
4099 EXPORT_SYMBOL_GPL(lockdep_hardirqs_on_prepare);
4101 void noinstr lockdep_hardirqs_on(unsigned long ip)
4103 struct irqtrace_events *trace = ¤t->irqtrace;
4105 if (unlikely(!debug_locks))
4109 * NMIs can happen in the middle of local_irq_{en,dis}able() where the
4110 * tracking state and hardware state are out of sync.
4112 * NMIs must save lockdep_hardirqs_enabled() to restore IRQ state from,
4113 * and not rely on hardware state like normal interrupts.
4115 if (unlikely(in_nmi())) {
4116 if (!IS_ENABLED(CONFIG_TRACE_IRQFLAGS_NMI))
4121 * - recursion check, because NMI can hit lockdep;
4122 * - hardware state check, because above;
4123 * - chain_key check, see lockdep_hardirqs_on_prepare().
4128 if (unlikely(this_cpu_read(lockdep_recursion)))
4131 if (lockdep_hardirqs_enabled()) {
4133 * Neither irq nor preemption are disabled here
4134 * so this is racy by nature but losing one hit
4135 * in a stat is not a big deal.
4137 __debug_atomic_inc(redundant_hardirqs_on);
4142 * We're enabling irqs and according to our state above irqs weren't
4143 * already enabled, yet we find the hardware thinks they are in fact
4144 * enabled.. someone messed up their IRQ state tracing.
4146 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4150 * Ensure the lock stack remained unchanged between
4151 * lockdep_hardirqs_on_prepare() and lockdep_hardirqs_on().
4153 DEBUG_LOCKS_WARN_ON(current->hardirq_chain_key !=
4154 current->curr_chain_key);
4157 /* we'll do an OFF -> ON transition: */
4158 __this_cpu_write(hardirqs_enabled, 1);
4159 trace->hardirq_enable_ip = ip;
4160 trace->hardirq_enable_event = ++trace->irq_events;
4161 debug_atomic_inc(hardirqs_on_events);
4163 EXPORT_SYMBOL_GPL(lockdep_hardirqs_on);
4166 * Hardirqs were disabled:
4168 void noinstr lockdep_hardirqs_off(unsigned long ip)
4170 if (unlikely(!debug_locks))
4174 * Matching lockdep_hardirqs_on(), allow NMIs in the middle of lockdep;
4175 * they will restore the software state. This ensures the software
4176 * state is consistent inside NMIs as well.
4179 if (!IS_ENABLED(CONFIG_TRACE_IRQFLAGS_NMI))
4181 } else if (__this_cpu_read(lockdep_recursion))
4185 * So we're supposed to get called after you mask local IRQs, but for
4186 * some reason the hardware doesn't quite think you did a proper job.
4188 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4191 if (lockdep_hardirqs_enabled()) {
4192 struct irqtrace_events *trace = ¤t->irqtrace;
4195 * We have done an ON -> OFF transition:
4197 __this_cpu_write(hardirqs_enabled, 0);
4198 trace->hardirq_disable_ip = ip;
4199 trace->hardirq_disable_event = ++trace->irq_events;
4200 debug_atomic_inc(hardirqs_off_events);
4202 debug_atomic_inc(redundant_hardirqs_off);
4205 EXPORT_SYMBOL_GPL(lockdep_hardirqs_off);
4208 * Softirqs will be enabled:
4210 void lockdep_softirqs_on(unsigned long ip)
4212 struct irqtrace_events *trace = ¤t->irqtrace;
4214 if (unlikely(!lockdep_enabled()))
4218 * We fancy IRQs being disabled here, see softirq.c, avoids
4219 * funny state and nesting things.
4221 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4224 if (current->softirqs_enabled) {
4225 debug_atomic_inc(redundant_softirqs_on);
4229 lockdep_recursion_inc();
4231 * We'll do an OFF -> ON transition:
4233 current->softirqs_enabled = 1;
4234 trace->softirq_enable_ip = ip;
4235 trace->softirq_enable_event = ++trace->irq_events;
4236 debug_atomic_inc(softirqs_on_events);
4238 * We are going to turn softirqs on, so set the
4239 * usage bit for all held locks, if hardirqs are
4242 if (lockdep_hardirqs_enabled())
4243 mark_held_locks(current, LOCK_ENABLED_SOFTIRQ);
4244 lockdep_recursion_finish();
4248 * Softirqs were disabled:
4250 void lockdep_softirqs_off(unsigned long ip)
4252 if (unlikely(!lockdep_enabled()))
4256 * We fancy IRQs being disabled here, see softirq.c
4258 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4261 if (current->softirqs_enabled) {
4262 struct irqtrace_events *trace = ¤t->irqtrace;
4265 * We have done an ON -> OFF transition:
4267 current->softirqs_enabled = 0;
4268 trace->softirq_disable_ip = ip;
4269 trace->softirq_disable_event = ++trace->irq_events;
4270 debug_atomic_inc(softirqs_off_events);
4272 * Whoops, we wanted softirqs off, so why aren't they?
4274 DEBUG_LOCKS_WARN_ON(!softirq_count());
4276 debug_atomic_inc(redundant_softirqs_off);
4280 mark_usage(struct task_struct *curr, struct held_lock *hlock, int check)
4286 * If non-trylock use in a hardirq or softirq context, then
4287 * mark the lock as used in these contexts:
4289 if (!hlock->trylock) {
4291 if (lockdep_hardirq_context())
4292 if (!mark_lock(curr, hlock,
4293 LOCK_USED_IN_HARDIRQ_READ))
4295 if (curr->softirq_context)
4296 if (!mark_lock(curr, hlock,
4297 LOCK_USED_IN_SOFTIRQ_READ))
4300 if (lockdep_hardirq_context())
4301 if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ))
4303 if (curr->softirq_context)
4304 if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ))
4308 if (!hlock->hardirqs_off) {
4310 if (!mark_lock(curr, hlock,
4311 LOCK_ENABLED_HARDIRQ_READ))
4313 if (curr->softirqs_enabled)
4314 if (!mark_lock(curr, hlock,
4315 LOCK_ENABLED_SOFTIRQ_READ))
4318 if (!mark_lock(curr, hlock,
4319 LOCK_ENABLED_HARDIRQ))
4321 if (curr->softirqs_enabled)
4322 if (!mark_lock(curr, hlock,
4323 LOCK_ENABLED_SOFTIRQ))
4329 /* mark it as used: */
4330 if (!mark_lock(curr, hlock, LOCK_USED))
4336 static inline unsigned int task_irq_context(struct task_struct *task)
4338 return LOCK_CHAIN_HARDIRQ_CONTEXT * !!lockdep_hardirq_context() +
4339 LOCK_CHAIN_SOFTIRQ_CONTEXT * !!task->softirq_context;
4342 static int separate_irq_context(struct task_struct *curr,
4343 struct held_lock *hlock)
4345 unsigned int depth = curr->lockdep_depth;
4348 * Keep track of points where we cross into an interrupt context:
4351 struct held_lock *prev_hlock;
4353 prev_hlock = curr->held_locks + depth-1;
4355 * If we cross into another context, reset the
4356 * hash key (this also prevents the checking and the
4357 * adding of the dependency to 'prev'):
4359 if (prev_hlock->irq_context != hlock->irq_context)
4366 * Mark a lock with a usage bit, and validate the state transition:
4368 static int mark_lock(struct task_struct *curr, struct held_lock *this,
4369 enum lock_usage_bit new_bit)
4371 unsigned int new_mask, ret = 1;
4373 if (new_bit >= LOCK_USAGE_STATES) {
4374 DEBUG_LOCKS_WARN_ON(1);
4378 if (new_bit == LOCK_USED && this->read)
4379 new_bit = LOCK_USED_READ;
4381 new_mask = 1 << new_bit;
4384 * If already set then do not dirty the cacheline,
4385 * nor do any checks:
4387 if (likely(hlock_class(this)->usage_mask & new_mask))
4393 * Make sure we didn't race:
4395 if (unlikely(hlock_class(this)->usage_mask & new_mask))
4398 if (!hlock_class(this)->usage_mask)
4399 debug_atomic_dec(nr_unused_locks);
4401 hlock_class(this)->usage_mask |= new_mask;
4403 if (new_bit < LOCK_TRACE_STATES) {
4404 if (!(hlock_class(this)->usage_traces[new_bit] = save_trace()))
4408 if (new_bit < LOCK_USED) {
4409 ret = mark_lock_irq(curr, this, new_bit);
4418 * We must printk outside of the graph_lock:
4421 printk("\nmarked lock as {%s}:\n", usage_str[new_bit]);
4423 print_irqtrace_events(curr);
4430 static inline short task_wait_context(struct task_struct *curr)
4433 * Set appropriate wait type for the context; for IRQs we have to take
4434 * into account force_irqthread as that is implied by PREEMPT_RT.
4436 if (lockdep_hardirq_context()) {
4438 * Check if force_irqthreads will run us threaded.
4440 if (curr->hardirq_threaded || curr->irq_config)
4441 return LD_WAIT_CONFIG;
4443 return LD_WAIT_SPIN;
4444 } else if (curr->softirq_context) {
4446 * Softirqs are always threaded.
4448 return LD_WAIT_CONFIG;
4455 print_lock_invalid_wait_context(struct task_struct *curr,
4456 struct held_lock *hlock)
4460 if (!debug_locks_off())
4462 if (debug_locks_silent)
4466 pr_warn("=============================\n");
4467 pr_warn("[ BUG: Invalid wait context ]\n");
4468 print_kernel_ident();
4469 pr_warn("-----------------------------\n");
4471 pr_warn("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr));
4474 pr_warn("other info that might help us debug this:\n");
4476 curr_inner = task_wait_context(curr);
4477 pr_warn("context-{%d:%d}\n", curr_inner, curr_inner);
4479 lockdep_print_held_locks(curr);
4481 pr_warn("stack backtrace:\n");
4488 * Verify the wait_type context.
4490 * This check validates we takes locks in the right wait-type order; that is it
4491 * ensures that we do not take mutexes inside spinlocks and do not attempt to
4492 * acquire spinlocks inside raw_spinlocks and the sort.
4494 * The entire thing is slightly more complex because of RCU, RCU is a lock that
4495 * can be taken from (pretty much) any context but also has constraints.
4496 * However when taken in a stricter environment the RCU lock does not loosen
4499 * Therefore we must look for the strictest environment in the lock stack and
4500 * compare that to the lock we're trying to acquire.
4502 static int check_wait_context(struct task_struct *curr, struct held_lock *next)
4504 short next_inner = hlock_class(next)->wait_type_inner;
4505 short next_outer = hlock_class(next)->wait_type_outer;
4509 if (!curr->lockdep_depth || !next_inner || next->trylock)
4513 next_outer = next_inner;
4516 * Find start of current irq_context..
4518 for (depth = curr->lockdep_depth - 1; depth >= 0; depth--) {
4519 struct held_lock *prev = curr->held_locks + depth;
4520 if (prev->irq_context != next->irq_context)
4525 curr_inner = task_wait_context(curr);
4527 for (; depth < curr->lockdep_depth; depth++) {
4528 struct held_lock *prev = curr->held_locks + depth;
4529 short prev_inner = hlock_class(prev)->wait_type_inner;
4533 * We can have a bigger inner than a previous one
4534 * when outer is smaller than inner, as with RCU.
4536 * Also due to trylocks.
4538 curr_inner = min(curr_inner, prev_inner);
4542 if (next_outer > curr_inner)
4543 return print_lock_invalid_wait_context(curr, next);
4548 #else /* CONFIG_PROVE_LOCKING */
4551 mark_usage(struct task_struct *curr, struct held_lock *hlock, int check)
4556 static inline unsigned int task_irq_context(struct task_struct *task)
4561 static inline int separate_irq_context(struct task_struct *curr,
4562 struct held_lock *hlock)
4567 static inline int check_wait_context(struct task_struct *curr,
4568 struct held_lock *next)
4573 #endif /* CONFIG_PROVE_LOCKING */
4576 * Initialize a lock instance's lock-class mapping info:
4578 void lockdep_init_map_waits(struct lockdep_map *lock, const char *name,
4579 struct lock_class_key *key, int subclass,
4580 short inner, short outer)
4584 for (i = 0; i < NR_LOCKDEP_CACHING_CLASSES; i++)
4585 lock->class_cache[i] = NULL;
4587 #ifdef CONFIG_LOCK_STAT
4588 lock->cpu = raw_smp_processor_id();
4592 * Can't be having no nameless bastards around this place!
4594 if (DEBUG_LOCKS_WARN_ON(!name)) {
4595 lock->name = "NULL";
4601 lock->wait_type_outer = outer;
4602 lock->wait_type_inner = inner;
4605 * No key, no joy, we need to hash something.
4607 if (DEBUG_LOCKS_WARN_ON(!key))
4610 * Sanity check, the lock-class key must either have been allocated
4611 * statically or must have been registered as a dynamic key.
4613 if (!static_obj(key) && !is_dynamic_key(key)) {
4615 printk(KERN_ERR "BUG: key %px has not been registered!\n", key);
4616 DEBUG_LOCKS_WARN_ON(1);
4621 if (unlikely(!debug_locks))
4625 unsigned long flags;
4627 if (DEBUG_LOCKS_WARN_ON(!lockdep_enabled()))
4630 raw_local_irq_save(flags);
4631 lockdep_recursion_inc();
4632 register_lock_class(lock, subclass, 1);
4633 lockdep_recursion_finish();
4634 raw_local_irq_restore(flags);
4637 EXPORT_SYMBOL_GPL(lockdep_init_map_waits);
4639 struct lock_class_key __lockdep_no_validate__;
4640 EXPORT_SYMBOL_GPL(__lockdep_no_validate__);
4643 print_lock_nested_lock_not_held(struct task_struct *curr,
4644 struct held_lock *hlock,
4647 if (!debug_locks_off())
4649 if (debug_locks_silent)
4653 pr_warn("==================================\n");
4654 pr_warn("WARNING: Nested lock was not taken\n");
4655 print_kernel_ident();
4656 pr_warn("----------------------------------\n");
4658 pr_warn("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr));
4661 pr_warn("\nbut this task is not holding:\n");
4662 pr_warn("%s\n", hlock->nest_lock->name);
4664 pr_warn("\nstack backtrace:\n");
4667 pr_warn("\nother info that might help us debug this:\n");
4668 lockdep_print_held_locks(curr);
4670 pr_warn("\nstack backtrace:\n");
4674 static int __lock_is_held(const struct lockdep_map *lock, int read);
4677 * This gets called for every mutex_lock*()/spin_lock*() operation.
4678 * We maintain the dependency maps and validate the locking attempt:
4680 * The callers must make sure that IRQs are disabled before calling it,
4681 * otherwise we could get an interrupt which would want to take locks,
4682 * which would end up in lockdep again.
4684 static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
4685 int trylock, int read, int check, int hardirqs_off,
4686 struct lockdep_map *nest_lock, unsigned long ip,
4687 int references, int pin_count)
4689 struct task_struct *curr = current;
4690 struct lock_class *class = NULL;
4691 struct held_lock *hlock;
4697 if (unlikely(!debug_locks))
4700 if (!prove_locking || lock->key == &__lockdep_no_validate__)
4703 if (subclass < NR_LOCKDEP_CACHING_CLASSES)
4704 class = lock->class_cache[subclass];
4708 if (unlikely(!class)) {
4709 class = register_lock_class(lock, subclass, 0);
4714 debug_class_ops_inc(class);
4716 if (very_verbose(class)) {
4717 printk("\nacquire class [%px] %s", class->key, class->name);
4718 if (class->name_version > 1)
4719 printk(KERN_CONT "#%d", class->name_version);
4720 printk(KERN_CONT "\n");
4725 * Add the lock to the list of currently held locks.
4726 * (we dont increase the depth just yet, up until the
4727 * dependency checks are done)
4729 depth = curr->lockdep_depth;
4731 * Ran out of static storage for our per-task lock stack again have we?
4733 if (DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH))
4736 class_idx = class - lock_classes;
4738 if (depth) { /* we're holding locks */
4739 hlock = curr->held_locks + depth - 1;
4740 if (hlock->class_idx == class_idx && nest_lock) {
4744 if (!hlock->references)
4745 hlock->references++;
4747 hlock->references += references;
4750 if (DEBUG_LOCKS_WARN_ON(hlock->references < references))
4757 hlock = curr->held_locks + depth;
4759 * Plain impossible, we just registered it and checked it weren't no
4760 * NULL like.. I bet this mushroom I ate was good!
4762 if (DEBUG_LOCKS_WARN_ON(!class))
4764 hlock->class_idx = class_idx;
4765 hlock->acquire_ip = ip;
4766 hlock->instance = lock;
4767 hlock->nest_lock = nest_lock;
4768 hlock->irq_context = task_irq_context(curr);
4769 hlock->trylock = trylock;
4771 hlock->check = check;
4772 hlock->hardirqs_off = !!hardirqs_off;
4773 hlock->references = references;
4774 #ifdef CONFIG_LOCK_STAT
4775 hlock->waittime_stamp = 0;
4776 hlock->holdtime_stamp = lockstat_clock();
4778 hlock->pin_count = pin_count;
4780 if (check_wait_context(curr, hlock))
4783 /* Initialize the lock usage bit */
4784 if (!mark_usage(curr, hlock, check))
4788 * Calculate the chain hash: it's the combined hash of all the
4789 * lock keys along the dependency chain. We save the hash value
4790 * at every step so that we can get the current hash easily
4791 * after unlock. The chain hash is then used to cache dependency
4794 * The 'key ID' is what is the most compact key value to drive
4795 * the hash, not class->key.
4798 * Whoops, we did it again.. class_idx is invalid.
4800 if (DEBUG_LOCKS_WARN_ON(!test_bit(class_idx, lock_classes_in_use)))
4803 chain_key = curr->curr_chain_key;
4806 * How can we have a chain hash when we ain't got no keys?!
4808 if (DEBUG_LOCKS_WARN_ON(chain_key != INITIAL_CHAIN_KEY))
4813 hlock->prev_chain_key = chain_key;
4814 if (separate_irq_context(curr, hlock)) {
4815 chain_key = INITIAL_CHAIN_KEY;
4818 chain_key = iterate_chain_key(chain_key, hlock_id(hlock));
4820 if (nest_lock && !__lock_is_held(nest_lock, -1)) {
4821 print_lock_nested_lock_not_held(curr, hlock, ip);
4825 if (!debug_locks_silent) {
4826 WARN_ON_ONCE(depth && !hlock_class(hlock - 1)->key);
4827 WARN_ON_ONCE(!hlock_class(hlock)->key);
4830 if (!validate_chain(curr, hlock, chain_head, chain_key))
4833 curr->curr_chain_key = chain_key;
4834 curr->lockdep_depth++;
4835 check_chain_key(curr);
4836 #ifdef CONFIG_DEBUG_LOCKDEP
4837 if (unlikely(!debug_locks))
4840 if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
4842 print_lockdep_off("BUG: MAX_LOCK_DEPTH too low!");
4843 printk(KERN_DEBUG "depth: %i max: %lu!\n",
4844 curr->lockdep_depth, MAX_LOCK_DEPTH);
4846 lockdep_print_held_locks(current);
4847 debug_show_all_locks();
4853 if (unlikely(curr->lockdep_depth > max_lockdep_depth))
4854 max_lockdep_depth = curr->lockdep_depth;
4859 static void print_unlock_imbalance_bug(struct task_struct *curr,
4860 struct lockdep_map *lock,
4863 if (!debug_locks_off())
4865 if (debug_locks_silent)
4869 pr_warn("=====================================\n");
4870 pr_warn("WARNING: bad unlock balance detected!\n");
4871 print_kernel_ident();
4872 pr_warn("-------------------------------------\n");
4873 pr_warn("%s/%d is trying to release lock (",
4874 curr->comm, task_pid_nr(curr));
4875 print_lockdep_cache(lock);
4877 print_ip_sym(KERN_WARNING, ip);
4878 pr_warn("but there are no more locks to release!\n");
4879 pr_warn("\nother info that might help us debug this:\n");
4880 lockdep_print_held_locks(curr);
4882 pr_warn("\nstack backtrace:\n");
4886 static noinstr int match_held_lock(const struct held_lock *hlock,
4887 const struct lockdep_map *lock)
4889 if (hlock->instance == lock)
4892 if (hlock->references) {
4893 const struct lock_class *class = lock->class_cache[0];
4896 class = look_up_lock_class(lock, 0);
4899 * If look_up_lock_class() failed to find a class, we're trying
4900 * to test if we hold a lock that has never yet been acquired.
4901 * Clearly if the lock hasn't been acquired _ever_, we're not
4902 * holding it either, so report failure.
4908 * References, but not a lock we're actually ref-counting?
4909 * State got messed up, follow the sites that change ->references
4910 * and try to make sense of it.
4912 if (DEBUG_LOCKS_WARN_ON(!hlock->nest_lock))
4915 if (hlock->class_idx == class - lock_classes)
4922 /* @depth must not be zero */
4923 static struct held_lock *find_held_lock(struct task_struct *curr,
4924 struct lockdep_map *lock,
4925 unsigned int depth, int *idx)
4927 struct held_lock *ret, *hlock, *prev_hlock;
4931 hlock = curr->held_locks + i;
4933 if (match_held_lock(hlock, lock))
4937 for (i--, prev_hlock = hlock--;
4939 i--, prev_hlock = hlock--) {
4941 * We must not cross into another context:
4943 if (prev_hlock->irq_context != hlock->irq_context) {
4947 if (match_held_lock(hlock, lock)) {
4958 static int reacquire_held_locks(struct task_struct *curr, unsigned int depth,
4959 int idx, unsigned int *merged)
4961 struct held_lock *hlock;
4962 int first_idx = idx;
4964 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4967 for (hlock = curr->held_locks + idx; idx < depth; idx++, hlock++) {
4968 switch (__lock_acquire(hlock->instance,
4969 hlock_class(hlock)->subclass,
4971 hlock->read, hlock->check,
4972 hlock->hardirqs_off,
4973 hlock->nest_lock, hlock->acquire_ip,
4974 hlock->references, hlock->pin_count)) {
4980 *merged += (idx == first_idx);
4991 __lock_set_class(struct lockdep_map *lock, const char *name,
4992 struct lock_class_key *key, unsigned int subclass,
4995 struct task_struct *curr = current;
4996 unsigned int depth, merged = 0;
4997 struct held_lock *hlock;
4998 struct lock_class *class;
5001 if (unlikely(!debug_locks))
5004 depth = curr->lockdep_depth;
5006 * This function is about (re)setting the class of a held lock,
5007 * yet we're not actually holding any locks. Naughty user!
5009 if (DEBUG_LOCKS_WARN_ON(!depth))
5012 hlock = find_held_lock(curr, lock, depth, &i);
5014 print_unlock_imbalance_bug(curr, lock, ip);
5018 lockdep_init_map_waits(lock, name, key, 0,
5019 lock->wait_type_inner,
5020 lock->wait_type_outer);
5021 class = register_lock_class(lock, subclass, 0);
5022 hlock->class_idx = class - lock_classes;
5024 curr->lockdep_depth = i;
5025 curr->curr_chain_key = hlock->prev_chain_key;
5027 if (reacquire_held_locks(curr, depth, i, &merged))
5031 * I took it apart and put it back together again, except now I have
5032 * these 'spare' parts.. where shall I put them.
5034 if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - merged))
5039 static int __lock_downgrade(struct lockdep_map *lock, unsigned long ip)
5041 struct task_struct *curr = current;
5042 unsigned int depth, merged = 0;
5043 struct held_lock *hlock;
5046 if (unlikely(!debug_locks))
5049 depth = curr->lockdep_depth;
5051 * This function is about (re)setting the class of a held lock,
5052 * yet we're not actually holding any locks. Naughty user!
5054 if (DEBUG_LOCKS_WARN_ON(!depth))
5057 hlock = find_held_lock(curr, lock, depth, &i);
5059 print_unlock_imbalance_bug(curr, lock, ip);
5063 curr->lockdep_depth = i;
5064 curr->curr_chain_key = hlock->prev_chain_key;
5066 WARN(hlock->read, "downgrading a read lock");
5068 hlock->acquire_ip = ip;
5070 if (reacquire_held_locks(curr, depth, i, &merged))
5073 /* Merging can't happen with unchanged classes.. */
5074 if (DEBUG_LOCKS_WARN_ON(merged))
5078 * I took it apart and put it back together again, except now I have
5079 * these 'spare' parts.. where shall I put them.
5081 if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth))
5088 * Remove the lock from the list of currently held locks - this gets
5089 * called on mutex_unlock()/spin_unlock*() (or on a failed
5090 * mutex_lock_interruptible()).
5093 __lock_release(struct lockdep_map *lock, unsigned long ip)
5095 struct task_struct *curr = current;
5096 unsigned int depth, merged = 1;
5097 struct held_lock *hlock;
5100 if (unlikely(!debug_locks))
5103 depth = curr->lockdep_depth;
5105 * So we're all set to release this lock.. wait what lock? We don't
5106 * own any locks, you've been drinking again?
5109 print_unlock_imbalance_bug(curr, lock, ip);
5114 * Check whether the lock exists in the current stack
5117 hlock = find_held_lock(curr, lock, depth, &i);
5119 print_unlock_imbalance_bug(curr, lock, ip);
5123 if (hlock->instance == lock)
5124 lock_release_holdtime(hlock);
5126 WARN(hlock->pin_count, "releasing a pinned lock\n");
5128 if (hlock->references) {
5129 hlock->references--;
5130 if (hlock->references) {
5132 * We had, and after removing one, still have
5133 * references, the current lock stack is still
5134 * valid. We're done!
5141 * We have the right lock to unlock, 'hlock' points to it.
5142 * Now we remove it from the stack, and add back the other
5143 * entries (if any), recalculating the hash along the way:
5146 curr->lockdep_depth = i;
5147 curr->curr_chain_key = hlock->prev_chain_key;
5150 * The most likely case is when the unlock is on the innermost
5151 * lock. In this case, we are done!
5156 if (reacquire_held_locks(curr, depth, i + 1, &merged))
5160 * We had N bottles of beer on the wall, we drank one, but now
5161 * there's not N-1 bottles of beer left on the wall...
5162 * Pouring two of the bottles together is acceptable.
5164 DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - merged);
5167 * Since reacquire_held_locks() would have called check_chain_key()
5168 * indirectly via __lock_acquire(), we don't need to do it again
5174 static __always_inline
5175 int __lock_is_held(const struct lockdep_map *lock, int read)
5177 struct task_struct *curr = current;
5180 for (i = 0; i < curr->lockdep_depth; i++) {
5181 struct held_lock *hlock = curr->held_locks + i;
5183 if (match_held_lock(hlock, lock)) {
5184 if (read == -1 || hlock->read == read)
5194 static struct pin_cookie __lock_pin_lock(struct lockdep_map *lock)
5196 struct pin_cookie cookie = NIL_COOKIE;
5197 struct task_struct *curr = current;
5200 if (unlikely(!debug_locks))
5203 for (i = 0; i < curr->lockdep_depth; i++) {
5204 struct held_lock *hlock = curr->held_locks + i;
5206 if (match_held_lock(hlock, lock)) {
5208 * Grab 16bits of randomness; this is sufficient to not
5209 * be guessable and still allows some pin nesting in
5210 * our u32 pin_count.
5212 cookie.val = 1 + (prandom_u32() >> 16);
5213 hlock->pin_count += cookie.val;
5218 WARN(1, "pinning an unheld lock\n");
5222 static void __lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
5224 struct task_struct *curr = current;
5227 if (unlikely(!debug_locks))
5230 for (i = 0; i < curr->lockdep_depth; i++) {
5231 struct held_lock *hlock = curr->held_locks + i;
5233 if (match_held_lock(hlock, lock)) {
5234 hlock->pin_count += cookie.val;
5239 WARN(1, "pinning an unheld lock\n");
5242 static void __lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
5244 struct task_struct *curr = current;
5247 if (unlikely(!debug_locks))
5250 for (i = 0; i < curr->lockdep_depth; i++) {
5251 struct held_lock *hlock = curr->held_locks + i;
5253 if (match_held_lock(hlock, lock)) {
5254 if (WARN(!hlock->pin_count, "unpinning an unpinned lock\n"))
5257 hlock->pin_count -= cookie.val;
5259 if (WARN((int)hlock->pin_count < 0, "pin count corrupted\n"))
5260 hlock->pin_count = 0;
5266 WARN(1, "unpinning an unheld lock\n");
5270 * Check whether we follow the irq-flags state precisely:
5272 static void check_flags(unsigned long flags)
5274 #if defined(CONFIG_PROVE_LOCKING) && defined(CONFIG_DEBUG_LOCKDEP)
5278 if (irqs_disabled_flags(flags)) {
5279 if (DEBUG_LOCKS_WARN_ON(lockdep_hardirqs_enabled())) {
5280 printk("possible reason: unannotated irqs-off.\n");
5283 if (DEBUG_LOCKS_WARN_ON(!lockdep_hardirqs_enabled())) {
5284 printk("possible reason: unannotated irqs-on.\n");
5289 * We dont accurately track softirq state in e.g.
5290 * hardirq contexts (such as on 4KSTACKS), so only
5291 * check if not in hardirq contexts:
5293 if (!hardirq_count()) {
5294 if (softirq_count()) {
5295 /* like the above, but with softirqs */
5296 DEBUG_LOCKS_WARN_ON(current->softirqs_enabled);
5298 /* lick the above, does it taste good? */
5299 DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled);
5304 print_irqtrace_events(current);
5308 void lock_set_class(struct lockdep_map *lock, const char *name,
5309 struct lock_class_key *key, unsigned int subclass,
5312 unsigned long flags;
5314 if (unlikely(!lockdep_enabled()))
5317 raw_local_irq_save(flags);
5318 lockdep_recursion_inc();
5320 if (__lock_set_class(lock, name, key, subclass, ip))
5321 check_chain_key(current);
5322 lockdep_recursion_finish();
5323 raw_local_irq_restore(flags);
5325 EXPORT_SYMBOL_GPL(lock_set_class);
5327 void lock_downgrade(struct lockdep_map *lock, unsigned long ip)
5329 unsigned long flags;
5331 if (unlikely(!lockdep_enabled()))
5334 raw_local_irq_save(flags);
5335 lockdep_recursion_inc();
5337 if (__lock_downgrade(lock, ip))
5338 check_chain_key(current);
5339 lockdep_recursion_finish();
5340 raw_local_irq_restore(flags);
5342 EXPORT_SYMBOL_GPL(lock_downgrade);
5344 /* NMI context !!! */
5345 static void verify_lock_unused(struct lockdep_map *lock, struct held_lock *hlock, int subclass)
5347 #ifdef CONFIG_PROVE_LOCKING
5348 struct lock_class *class = look_up_lock_class(lock, subclass);
5349 unsigned long mask = LOCKF_USED;
5351 /* if it doesn't have a class (yet), it certainly hasn't been used yet */
5356 * READ locks only conflict with USED, such that if we only ever use
5357 * READ locks, there is no deadlock possible -- RCU.
5360 mask |= LOCKF_USED_READ;
5362 if (!(class->usage_mask & mask))
5365 hlock->class_idx = class - lock_classes;
5367 print_usage_bug(current, hlock, LOCK_USED, LOCK_USAGE_STATES);
5371 static bool lockdep_nmi(void)
5373 if (raw_cpu_read(lockdep_recursion))
5383 * read_lock() is recursive if:
5384 * 1. We force lockdep think this way in selftests or
5385 * 2. The implementation is not queued read/write lock or
5386 * 3. The locker is at an in_interrupt() context.
5388 bool read_lock_is_recursive(void)
5390 return force_read_lock_recursive ||
5391 !IS_ENABLED(CONFIG_QUEUED_RWLOCKS) ||
5394 EXPORT_SYMBOL_GPL(read_lock_is_recursive);
5397 * We are not always called with irqs disabled - do that here,
5398 * and also avoid lockdep recursion:
5400 void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
5401 int trylock, int read, int check,
5402 struct lockdep_map *nest_lock, unsigned long ip)
5404 unsigned long flags;
5406 trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip);
5411 if (unlikely(!lockdep_enabled())) {
5412 /* XXX allow trylock from NMI ?!? */
5413 if (lockdep_nmi() && !trylock) {
5414 struct held_lock hlock;
5416 hlock.acquire_ip = ip;
5417 hlock.instance = lock;
5418 hlock.nest_lock = nest_lock;
5419 hlock.irq_context = 2; // XXX
5420 hlock.trylock = trylock;
5422 hlock.check = check;
5423 hlock.hardirqs_off = true;
5424 hlock.references = 0;
5426 verify_lock_unused(lock, &hlock, subclass);
5431 raw_local_irq_save(flags);
5434 lockdep_recursion_inc();
5435 __lock_acquire(lock, subclass, trylock, read, check,
5436 irqs_disabled_flags(flags), nest_lock, ip, 0, 0);
5437 lockdep_recursion_finish();
5438 raw_local_irq_restore(flags);
5440 EXPORT_SYMBOL_GPL(lock_acquire);
5442 void lock_release(struct lockdep_map *lock, unsigned long ip)
5444 unsigned long flags;
5446 trace_lock_release(lock, ip);
5448 if (unlikely(!lockdep_enabled()))
5451 raw_local_irq_save(flags);
5454 lockdep_recursion_inc();
5455 if (__lock_release(lock, ip))
5456 check_chain_key(current);
5457 lockdep_recursion_finish();
5458 raw_local_irq_restore(flags);
5460 EXPORT_SYMBOL_GPL(lock_release);
5462 noinstr int lock_is_held_type(const struct lockdep_map *lock, int read)
5464 unsigned long flags;
5467 if (unlikely(!lockdep_enabled()))
5468 return 1; /* avoid false negative lockdep_assert_held() */
5470 raw_local_irq_save(flags);
5473 lockdep_recursion_inc();
5474 ret = __lock_is_held(lock, read);
5475 lockdep_recursion_finish();
5476 raw_local_irq_restore(flags);
5480 EXPORT_SYMBOL_GPL(lock_is_held_type);
5481 NOKPROBE_SYMBOL(lock_is_held_type);
5483 struct pin_cookie lock_pin_lock(struct lockdep_map *lock)
5485 struct pin_cookie cookie = NIL_COOKIE;
5486 unsigned long flags;
5488 if (unlikely(!lockdep_enabled()))
5491 raw_local_irq_save(flags);
5494 lockdep_recursion_inc();
5495 cookie = __lock_pin_lock(lock);
5496 lockdep_recursion_finish();
5497 raw_local_irq_restore(flags);
5501 EXPORT_SYMBOL_GPL(lock_pin_lock);
5503 void lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
5505 unsigned long flags;
5507 if (unlikely(!lockdep_enabled()))
5510 raw_local_irq_save(flags);
5513 lockdep_recursion_inc();
5514 __lock_repin_lock(lock, cookie);
5515 lockdep_recursion_finish();
5516 raw_local_irq_restore(flags);
5518 EXPORT_SYMBOL_GPL(lock_repin_lock);
5520 void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
5522 unsigned long flags;
5524 if (unlikely(!lockdep_enabled()))
5527 raw_local_irq_save(flags);
5530 lockdep_recursion_inc();
5531 __lock_unpin_lock(lock, cookie);
5532 lockdep_recursion_finish();
5533 raw_local_irq_restore(flags);
5535 EXPORT_SYMBOL_GPL(lock_unpin_lock);
5537 #ifdef CONFIG_LOCK_STAT
5538 static void print_lock_contention_bug(struct task_struct *curr,
5539 struct lockdep_map *lock,
5542 if (!debug_locks_off())
5544 if (debug_locks_silent)
5548 pr_warn("=================================\n");
5549 pr_warn("WARNING: bad contention detected!\n");
5550 print_kernel_ident();
5551 pr_warn("---------------------------------\n");
5552 pr_warn("%s/%d is trying to contend lock (",
5553 curr->comm, task_pid_nr(curr));
5554 print_lockdep_cache(lock);
5556 print_ip_sym(KERN_WARNING, ip);
5557 pr_warn("but there are no locks held!\n");
5558 pr_warn("\nother info that might help us debug this:\n");
5559 lockdep_print_held_locks(curr);
5561 pr_warn("\nstack backtrace:\n");
5566 __lock_contended(struct lockdep_map *lock, unsigned long ip)
5568 struct task_struct *curr = current;
5569 struct held_lock *hlock;
5570 struct lock_class_stats *stats;
5572 int i, contention_point, contending_point;
5574 depth = curr->lockdep_depth;
5576 * Whee, we contended on this lock, except it seems we're not
5577 * actually trying to acquire anything much at all..
5579 if (DEBUG_LOCKS_WARN_ON(!depth))
5582 hlock = find_held_lock(curr, lock, depth, &i);
5584 print_lock_contention_bug(curr, lock, ip);
5588 if (hlock->instance != lock)
5591 hlock->waittime_stamp = lockstat_clock();
5593 contention_point = lock_point(hlock_class(hlock)->contention_point, ip);
5594 contending_point = lock_point(hlock_class(hlock)->contending_point,
5597 stats = get_lock_stats(hlock_class(hlock));
5598 if (contention_point < LOCKSTAT_POINTS)
5599 stats->contention_point[contention_point]++;
5600 if (contending_point < LOCKSTAT_POINTS)
5601 stats->contending_point[contending_point]++;
5602 if (lock->cpu != smp_processor_id())
5603 stats->bounces[bounce_contended + !!hlock->read]++;
5607 __lock_acquired(struct lockdep_map *lock, unsigned long ip)
5609 struct task_struct *curr = current;
5610 struct held_lock *hlock;
5611 struct lock_class_stats *stats;
5613 u64 now, waittime = 0;
5616 depth = curr->lockdep_depth;
5618 * Yay, we acquired ownership of this lock we didn't try to
5619 * acquire, how the heck did that happen?
5621 if (DEBUG_LOCKS_WARN_ON(!depth))
5624 hlock = find_held_lock(curr, lock, depth, &i);
5626 print_lock_contention_bug(curr, lock, _RET_IP_);
5630 if (hlock->instance != lock)
5633 cpu = smp_processor_id();
5634 if (hlock->waittime_stamp) {
5635 now = lockstat_clock();
5636 waittime = now - hlock->waittime_stamp;
5637 hlock->holdtime_stamp = now;
5640 stats = get_lock_stats(hlock_class(hlock));
5643 lock_time_inc(&stats->read_waittime, waittime);
5645 lock_time_inc(&stats->write_waittime, waittime);
5647 if (lock->cpu != cpu)
5648 stats->bounces[bounce_acquired + !!hlock->read]++;
5654 void lock_contended(struct lockdep_map *lock, unsigned long ip)
5656 unsigned long flags;
5658 trace_lock_acquired(lock, ip);
5660 if (unlikely(!lock_stat || !lockdep_enabled()))
5663 raw_local_irq_save(flags);
5665 lockdep_recursion_inc();
5666 __lock_contended(lock, ip);
5667 lockdep_recursion_finish();
5668 raw_local_irq_restore(flags);
5670 EXPORT_SYMBOL_GPL(lock_contended);
5672 void lock_acquired(struct lockdep_map *lock, unsigned long ip)
5674 unsigned long flags;
5676 trace_lock_contended(lock, ip);
5678 if (unlikely(!lock_stat || !lockdep_enabled()))
5681 raw_local_irq_save(flags);
5683 lockdep_recursion_inc();
5684 __lock_acquired(lock, ip);
5685 lockdep_recursion_finish();
5686 raw_local_irq_restore(flags);
5688 EXPORT_SYMBOL_GPL(lock_acquired);
5692 * Used by the testsuite, sanitize the validator state
5693 * after a simulated failure:
5696 void lockdep_reset(void)
5698 unsigned long flags;
5701 raw_local_irq_save(flags);
5702 lockdep_init_task(current);
5703 memset(current->held_locks, 0, MAX_LOCK_DEPTH*sizeof(struct held_lock));
5704 nr_hardirq_chains = 0;
5705 nr_softirq_chains = 0;
5706 nr_process_chains = 0;
5708 for (i = 0; i < CHAINHASH_SIZE; i++)
5709 INIT_HLIST_HEAD(chainhash_table + i);
5710 raw_local_irq_restore(flags);
5713 /* Remove a class from a lock chain. Must be called with the graph lock held. */
5714 static void remove_class_from_lock_chain(struct pending_free *pf,
5715 struct lock_chain *chain,
5716 struct lock_class *class)
5718 #ifdef CONFIG_PROVE_LOCKING
5721 for (i = chain->base; i < chain->base + chain->depth; i++) {
5722 if (chain_hlock_class_idx(chain_hlocks[i]) != class - lock_classes)
5725 * Each lock class occurs at most once in a lock chain so once
5726 * we found a match we can break out of this loop.
5728 goto free_lock_chain;
5730 /* Since the chain has not been modified, return. */
5734 free_chain_hlocks(chain->base, chain->depth);
5735 /* Overwrite the chain key for concurrent RCU readers. */
5736 WRITE_ONCE(chain->chain_key, INITIAL_CHAIN_KEY);
5737 dec_chains(chain->irq_context);
5740 * Note: calling hlist_del_rcu() from inside a
5741 * hlist_for_each_entry_rcu() loop is safe.
5743 hlist_del_rcu(&chain->entry);
5744 __set_bit(chain - lock_chains, pf->lock_chains_being_freed);
5745 nr_zapped_lock_chains++;
5749 /* Must be called with the graph lock held. */
5750 static void remove_class_from_lock_chains(struct pending_free *pf,
5751 struct lock_class *class)
5753 struct lock_chain *chain;
5754 struct hlist_head *head;
5757 for (i = 0; i < ARRAY_SIZE(chainhash_table); i++) {
5758 head = chainhash_table + i;
5759 hlist_for_each_entry_rcu(chain, head, entry) {
5760 remove_class_from_lock_chain(pf, chain, class);
5766 * Remove all references to a lock class. The caller must hold the graph lock.
5768 static void zap_class(struct pending_free *pf, struct lock_class *class)
5770 struct lock_list *entry;
5773 WARN_ON_ONCE(!class->key);
5776 * Remove all dependencies this lock is
5779 for_each_set_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
5780 entry = list_entries + i;
5781 if (entry->class != class && entry->links_to != class)
5783 __clear_bit(i, list_entries_in_use);
5785 list_del_rcu(&entry->entry);
5787 if (list_empty(&class->locks_after) &&
5788 list_empty(&class->locks_before)) {
5789 list_move_tail(&class->lock_entry, &pf->zapped);
5790 hlist_del_rcu(&class->hash_entry);
5791 WRITE_ONCE(class->key, NULL);
5792 WRITE_ONCE(class->name, NULL);
5794 __clear_bit(class - lock_classes, lock_classes_in_use);
5796 WARN_ONCE(true, "%s() failed for class %s\n", __func__,
5800 remove_class_from_lock_chains(pf, class);
5801 nr_zapped_classes++;
5804 static void reinit_class(struct lock_class *class)
5806 void *const p = class;
5807 const unsigned int offset = offsetof(struct lock_class, key);
5809 WARN_ON_ONCE(!class->lock_entry.next);
5810 WARN_ON_ONCE(!list_empty(&class->locks_after));
5811 WARN_ON_ONCE(!list_empty(&class->locks_before));
5812 memset(p + offset, 0, sizeof(*class) - offset);
5813 WARN_ON_ONCE(!class->lock_entry.next);
5814 WARN_ON_ONCE(!list_empty(&class->locks_after));
5815 WARN_ON_ONCE(!list_empty(&class->locks_before));
5818 static inline int within(const void *addr, void *start, unsigned long size)
5820 return addr >= start && addr < start + size;
5823 static bool inside_selftest(void)
5825 return current == lockdep_selftest_task_struct;
5828 /* The caller must hold the graph lock. */
5829 static struct pending_free *get_pending_free(void)
5831 return delayed_free.pf + delayed_free.index;
5834 static void free_zapped_rcu(struct rcu_head *cb);
5837 * Schedule an RCU callback if no RCU callback is pending. Must be called with
5838 * the graph lock held.
5840 static void call_rcu_zapped(struct pending_free *pf)
5842 WARN_ON_ONCE(inside_selftest());
5844 if (list_empty(&pf->zapped))
5847 if (delayed_free.scheduled)
5850 delayed_free.scheduled = true;
5852 WARN_ON_ONCE(delayed_free.pf + delayed_free.index != pf);
5853 delayed_free.index ^= 1;
5855 call_rcu(&delayed_free.rcu_head, free_zapped_rcu);
5858 /* The caller must hold the graph lock. May be called from RCU context. */
5859 static void __free_zapped_classes(struct pending_free *pf)
5861 struct lock_class *class;
5863 check_data_structures();
5865 list_for_each_entry(class, &pf->zapped, lock_entry)
5866 reinit_class(class);
5868 list_splice_init(&pf->zapped, &free_lock_classes);
5870 #ifdef CONFIG_PROVE_LOCKING
5871 bitmap_andnot(lock_chains_in_use, lock_chains_in_use,
5872 pf->lock_chains_being_freed, ARRAY_SIZE(lock_chains));
5873 bitmap_clear(pf->lock_chains_being_freed, 0, ARRAY_SIZE(lock_chains));
5877 static void free_zapped_rcu(struct rcu_head *ch)
5879 struct pending_free *pf;
5880 unsigned long flags;
5882 if (WARN_ON_ONCE(ch != &delayed_free.rcu_head))
5885 raw_local_irq_save(flags);
5889 pf = delayed_free.pf + (delayed_free.index ^ 1);
5890 __free_zapped_classes(pf);
5891 delayed_free.scheduled = false;
5894 * If there's anything on the open list, close and start a new callback.
5896 call_rcu_zapped(delayed_free.pf + delayed_free.index);
5899 raw_local_irq_restore(flags);
5903 * Remove all lock classes from the class hash table and from the
5904 * all_lock_classes list whose key or name is in the address range [start,
5905 * start + size). Move these lock classes to the zapped_classes list. Must
5906 * be called with the graph lock held.
5908 static void __lockdep_free_key_range(struct pending_free *pf, void *start,
5911 struct lock_class *class;
5912 struct hlist_head *head;
5915 /* Unhash all classes that were created by a module. */
5916 for (i = 0; i < CLASSHASH_SIZE; i++) {
5917 head = classhash_table + i;
5918 hlist_for_each_entry_rcu(class, head, hash_entry) {
5919 if (!within(class->key, start, size) &&
5920 !within(class->name, start, size))
5922 zap_class(pf, class);
5928 * Used in module.c to remove lock classes from memory that is going to be
5929 * freed; and possibly re-used by other modules.
5931 * We will have had one synchronize_rcu() before getting here, so we're
5932 * guaranteed nobody will look up these exact classes -- they're properly dead
5933 * but still allocated.
5935 static void lockdep_free_key_range_reg(void *start, unsigned long size)
5937 struct pending_free *pf;
5938 unsigned long flags;
5940 init_data_structures_once();
5942 raw_local_irq_save(flags);
5944 pf = get_pending_free();
5945 __lockdep_free_key_range(pf, start, size);
5946 call_rcu_zapped(pf);
5948 raw_local_irq_restore(flags);
5951 * Wait for any possible iterators from look_up_lock_class() to pass
5952 * before continuing to free the memory they refer to.
5958 * Free all lockdep keys in the range [start, start+size). Does not sleep.
5959 * Ignores debug_locks. Must only be used by the lockdep selftests.
5961 static void lockdep_free_key_range_imm(void *start, unsigned long size)
5963 struct pending_free *pf = delayed_free.pf;
5964 unsigned long flags;
5966 init_data_structures_once();
5968 raw_local_irq_save(flags);
5970 __lockdep_free_key_range(pf, start, size);
5971 __free_zapped_classes(pf);
5973 raw_local_irq_restore(flags);
5976 void lockdep_free_key_range(void *start, unsigned long size)
5978 init_data_structures_once();
5980 if (inside_selftest())
5981 lockdep_free_key_range_imm(start, size);
5983 lockdep_free_key_range_reg(start, size);
5987 * Check whether any element of the @lock->class_cache[] array refers to a
5988 * registered lock class. The caller must hold either the graph lock or the
5991 static bool lock_class_cache_is_registered(struct lockdep_map *lock)
5993 struct lock_class *class;
5994 struct hlist_head *head;
5997 for (i = 0; i < CLASSHASH_SIZE; i++) {
5998 head = classhash_table + i;
5999 hlist_for_each_entry_rcu(class, head, hash_entry) {
6000 for (j = 0; j < NR_LOCKDEP_CACHING_CLASSES; j++)
6001 if (lock->class_cache[j] == class)
6008 /* The caller must hold the graph lock. Does not sleep. */
6009 static void __lockdep_reset_lock(struct pending_free *pf,
6010 struct lockdep_map *lock)
6012 struct lock_class *class;
6016 * Remove all classes this lock might have:
6018 for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) {
6020 * If the class exists we look it up and zap it:
6022 class = look_up_lock_class(lock, j);
6024 zap_class(pf, class);
6027 * Debug check: in the end all mapped classes should
6030 if (WARN_ON_ONCE(lock_class_cache_is_registered(lock)))
6035 * Remove all information lockdep has about a lock if debug_locks == 1. Free
6036 * released data structures from RCU context.
6038 static void lockdep_reset_lock_reg(struct lockdep_map *lock)
6040 struct pending_free *pf;
6041 unsigned long flags;
6044 raw_local_irq_save(flags);
6045 locked = graph_lock();
6049 pf = get_pending_free();
6050 __lockdep_reset_lock(pf, lock);
6051 call_rcu_zapped(pf);
6055 raw_local_irq_restore(flags);
6059 * Reset a lock. Does not sleep. Ignores debug_locks. Must only be used by the
6060 * lockdep selftests.
6062 static void lockdep_reset_lock_imm(struct lockdep_map *lock)
6064 struct pending_free *pf = delayed_free.pf;
6065 unsigned long flags;
6067 raw_local_irq_save(flags);
6069 __lockdep_reset_lock(pf, lock);
6070 __free_zapped_classes(pf);
6072 raw_local_irq_restore(flags);
6075 void lockdep_reset_lock(struct lockdep_map *lock)
6077 init_data_structures_once();
6079 if (inside_selftest())
6080 lockdep_reset_lock_imm(lock);
6082 lockdep_reset_lock_reg(lock);
6085 /* Unregister a dynamically allocated key. */
6086 void lockdep_unregister_key(struct lock_class_key *key)
6088 struct hlist_head *hash_head = keyhashentry(key);
6089 struct lock_class_key *k;
6090 struct pending_free *pf;
6091 unsigned long flags;
6096 if (WARN_ON_ONCE(static_obj(key)))
6099 raw_local_irq_save(flags);
6103 pf = get_pending_free();
6104 hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
6106 hlist_del_rcu(&k->hash_entry);
6111 WARN_ON_ONCE(!found);
6112 __lockdep_free_key_range(pf, key, 1);
6113 call_rcu_zapped(pf);
6116 raw_local_irq_restore(flags);
6118 /* Wait until is_dynamic_key() has finished accessing k->hash_entry. */
6121 EXPORT_SYMBOL_GPL(lockdep_unregister_key);
6123 void __init lockdep_init(void)
6125 printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");
6127 printk("... MAX_LOCKDEP_SUBCLASSES: %lu\n", MAX_LOCKDEP_SUBCLASSES);
6128 printk("... MAX_LOCK_DEPTH: %lu\n", MAX_LOCK_DEPTH);
6129 printk("... MAX_LOCKDEP_KEYS: %lu\n", MAX_LOCKDEP_KEYS);
6130 printk("... CLASSHASH_SIZE: %lu\n", CLASSHASH_SIZE);
6131 printk("... MAX_LOCKDEP_ENTRIES: %lu\n", MAX_LOCKDEP_ENTRIES);
6132 printk("... MAX_LOCKDEP_CHAINS: %lu\n", MAX_LOCKDEP_CHAINS);
6133 printk("... CHAINHASH_SIZE: %lu\n", CHAINHASH_SIZE);
6135 printk(" memory used by lock dependency info: %zu kB\n",
6136 (sizeof(lock_classes) +
6137 sizeof(lock_classes_in_use) +
6138 sizeof(classhash_table) +
6139 sizeof(list_entries) +
6140 sizeof(list_entries_in_use) +
6141 sizeof(chainhash_table) +
6142 sizeof(delayed_free)
6143 #ifdef CONFIG_PROVE_LOCKING
6145 + sizeof(lock_chains)
6146 + sizeof(lock_chains_in_use)
6147 + sizeof(chain_hlocks)
6152 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
6153 printk(" memory used for stack traces: %zu kB\n",
6154 (sizeof(stack_trace) + sizeof(stack_trace_hash)) / 1024
6158 printk(" per task-struct memory footprint: %zu bytes\n",
6159 sizeof(((struct task_struct *)NULL)->held_locks));
6163 print_freed_lock_bug(struct task_struct *curr, const void *mem_from,
6164 const void *mem_to, struct held_lock *hlock)
6166 if (!debug_locks_off())
6168 if (debug_locks_silent)
6172 pr_warn("=========================\n");
6173 pr_warn("WARNING: held lock freed!\n");
6174 print_kernel_ident();
6175 pr_warn("-------------------------\n");
6176 pr_warn("%s/%d is freeing memory %px-%px, with a lock still held there!\n",
6177 curr->comm, task_pid_nr(curr), mem_from, mem_to-1);
6179 lockdep_print_held_locks(curr);
6181 pr_warn("\nstack backtrace:\n");
6185 static inline int not_in_range(const void* mem_from, unsigned long mem_len,
6186 const void* lock_from, unsigned long lock_len)
6188 return lock_from + lock_len <= mem_from ||
6189 mem_from + mem_len <= lock_from;
6193 * Called when kernel memory is freed (or unmapped), or if a lock
6194 * is destroyed or reinitialized - this code checks whether there is
6195 * any held lock in the memory range of <from> to <to>:
6197 void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len)
6199 struct task_struct *curr = current;
6200 struct held_lock *hlock;
6201 unsigned long flags;
6204 if (unlikely(!debug_locks))
6207 raw_local_irq_save(flags);
6208 for (i = 0; i < curr->lockdep_depth; i++) {
6209 hlock = curr->held_locks + i;
6211 if (not_in_range(mem_from, mem_len, hlock->instance,
6212 sizeof(*hlock->instance)))
6215 print_freed_lock_bug(curr, mem_from, mem_from + mem_len, hlock);
6218 raw_local_irq_restore(flags);
6220 EXPORT_SYMBOL_GPL(debug_check_no_locks_freed);
6222 static void print_held_locks_bug(void)
6224 if (!debug_locks_off())
6226 if (debug_locks_silent)
6230 pr_warn("====================================\n");
6231 pr_warn("WARNING: %s/%d still has locks held!\n",
6232 current->comm, task_pid_nr(current));
6233 print_kernel_ident();
6234 pr_warn("------------------------------------\n");
6235 lockdep_print_held_locks(current);
6236 pr_warn("\nstack backtrace:\n");
6240 void debug_check_no_locks_held(void)
6242 if (unlikely(current->lockdep_depth > 0))
6243 print_held_locks_bug();
6245 EXPORT_SYMBOL_GPL(debug_check_no_locks_held);
6248 void debug_show_all_locks(void)
6250 struct task_struct *g, *p;
6252 if (unlikely(!debug_locks)) {
6253 pr_warn("INFO: lockdep is turned off.\n");
6256 pr_warn("\nShowing all locks held in the system:\n");
6259 for_each_process_thread(g, p) {
6260 if (!p->lockdep_depth)
6262 lockdep_print_held_locks(p);
6263 touch_nmi_watchdog();
6264 touch_all_softlockup_watchdogs();
6269 pr_warn("=============================================\n\n");
6271 EXPORT_SYMBOL_GPL(debug_show_all_locks);
6275 * Careful: only use this function if you are sure that
6276 * the task cannot run in parallel!
6278 void debug_show_held_locks(struct task_struct *task)
6280 if (unlikely(!debug_locks)) {
6281 printk("INFO: lockdep is turned off.\n");
6284 lockdep_print_held_locks(task);
6286 EXPORT_SYMBOL_GPL(debug_show_held_locks);
6288 asmlinkage __visible void lockdep_sys_exit(void)
6290 struct task_struct *curr = current;
6292 if (unlikely(curr->lockdep_depth)) {
6293 if (!debug_locks_off())
6296 pr_warn("================================================\n");
6297 pr_warn("WARNING: lock held when returning to user space!\n");
6298 print_kernel_ident();
6299 pr_warn("------------------------------------------------\n");
6300 pr_warn("%s/%d is leaving the kernel with locks still held!\n",
6301 curr->comm, curr->pid);
6302 lockdep_print_held_locks(curr);
6306 * The lock history for each syscall should be independent. So wipe the
6307 * slate clean on return to userspace.
6309 lockdep_invariant_state(false);
6312 void lockdep_rcu_suspicious(const char *file, const int line, const char *s)
6314 struct task_struct *curr = current;
6316 /* Note: the following can be executed concurrently, so be careful. */
6318 pr_warn("=============================\n");
6319 pr_warn("WARNING: suspicious RCU usage\n");
6320 print_kernel_ident();
6321 pr_warn("-----------------------------\n");
6322 pr_warn("%s:%d %s!\n", file, line, s);
6323 pr_warn("\nother info that might help us debug this:\n\n");
6324 pr_warn("\n%srcu_scheduler_active = %d, debug_locks = %d\n",
6325 !rcu_lockdep_current_cpu_online()
6326 ? "RCU used illegally from offline CPU!\n"
6328 rcu_scheduler_active, debug_locks);
6331 * If a CPU is in the RCU-free window in idle (ie: in the section
6332 * between rcu_idle_enter() and rcu_idle_exit(), then RCU
6333 * considers that CPU to be in an "extended quiescent state",
6334 * which means that RCU will be completely ignoring that CPU.
6335 * Therefore, rcu_read_lock() and friends have absolutely no
6336 * effect on a CPU running in that state. In other words, even if
6337 * such an RCU-idle CPU has called rcu_read_lock(), RCU might well
6338 * delete data structures out from under it. RCU really has no
6339 * choice here: we need to keep an RCU-free window in idle where
6340 * the CPU may possibly enter into low power mode. This way we can
6341 * notice an extended quiescent state to other CPUs that started a grace
6342 * period. Otherwise we would delay any grace period as long as we run
6345 * So complain bitterly if someone does call rcu_read_lock(),
6346 * rcu_read_lock_bh() and so on from extended quiescent states.
6348 if (!rcu_is_watching())
6349 pr_warn("RCU used illegally from extended quiescent state!\n");
6351 lockdep_print_held_locks(curr);
6352 pr_warn("\nstack backtrace:\n");
6355 EXPORT_SYMBOL_GPL(lockdep_rcu_suspicious);