4 * Runtime locking correctness validator
6 * Started by Ingo Molnar:
8 * Copyright (C) 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
10 * this code maps all the lock dependencies as they occur in a live kernel
11 * and will warn about the following classes of locking bugs:
13 * - lock inversion scenarios
14 * - circular lock dependencies
15 * - hardirq/softirq safe/unsafe locking bugs
17 * Bugs are reported even if the current locking scenario does not cause
18 * any deadlock at this point.
20 * I.e. if anytime in the past two locks were taken in a different order,
21 * even if it happened for another task, even if those were different
22 * locks (but of the same class as this lock), this code will detect it.
24 * Thanks to Arjan van de Ven for coming up with the initial idea of
25 * mapping lock dependencies runtime.
27 #include <linux/mutex.h>
28 #include <linux/sched.h>
29 #include <linux/delay.h>
30 #include <linux/module.h>
31 #include <linux/proc_fs.h>
32 #include <linux/seq_file.h>
33 #include <linux/spinlock.h>
34 #include <linux/kallsyms.h>
35 #include <linux/interrupt.h>
36 #include <linux/stacktrace.h>
37 #include <linux/debug_locks.h>
38 #include <linux/irqflags.h>
39 #include <linux/utsname.h>
41 #include <asm/sections.h>
43 #include "lockdep_internals.h"
45 #ifdef CONFIG_PROVE_LOCKING
46 int prove_locking = 1;
47 module_param(prove_locking, int, 0644);
49 #define prove_locking 0
52 #ifdef CONFIG_LOCK_STAT
54 module_param(lock_stat, int, 0644);
60 * lockdep_lock: protects the lockdep graph, the hashes and the
61 * class/list/hash allocators.
63 * This is one of the rare exceptions where it's justified
64 * to use a raw spinlock - we really dont want the spinlock
65 * code to recurse back into the lockdep code...
67 static raw_spinlock_t lockdep_lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
69 static int graph_lock(void)
71 __raw_spin_lock(&lockdep_lock);
73 * Make sure that if another CPU detected a bug while
74 * walking the graph we dont change it (while the other
75 * CPU is busy printing out stuff with the graph lock
79 __raw_spin_unlock(&lockdep_lock);
85 static inline int graph_unlock(void)
87 if (debug_locks && !__raw_spin_is_locked(&lockdep_lock))
88 return DEBUG_LOCKS_WARN_ON(1);
90 __raw_spin_unlock(&lockdep_lock);
95 * Turn lock debugging off and return with 0 if it was off already,
96 * and also release the graph lock:
98 static inline int debug_locks_off_graph_unlock(void)
100 int ret = debug_locks_off();
102 __raw_spin_unlock(&lockdep_lock);
107 static int lockdep_initialized;
109 unsigned long nr_list_entries;
110 static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES];
113 * All data structures here are protected by the global debug_lock.
115 * Mutex key structs only get allocated, once during bootup, and never
116 * get freed - this significantly simplifies the debugging code.
118 unsigned long nr_lock_classes;
119 static struct lock_class lock_classes[MAX_LOCKDEP_KEYS];
121 #ifdef CONFIG_LOCK_STAT
122 static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS], lock_stats);
124 static int lock_contention_point(struct lock_class *class, unsigned long ip)
128 for (i = 0; i < ARRAY_SIZE(class->contention_point); i++) {
129 if (class->contention_point[i] == 0) {
130 class->contention_point[i] = ip;
133 if (class->contention_point[i] == ip)
140 static void lock_time_inc(struct lock_time *lt, s64 time)
145 if (time < lt->min || !lt->min)
152 static inline void lock_time_add(struct lock_time *src, struct lock_time *dst)
154 dst->min += src->min;
155 dst->max += src->max;
156 dst->total += src->total;
160 struct lock_class_stats lock_stats(struct lock_class *class)
162 struct lock_class_stats stats;
165 memset(&stats, 0, sizeof(struct lock_class_stats));
166 for_each_possible_cpu(cpu) {
167 struct lock_class_stats *pcs =
168 &per_cpu(lock_stats, cpu)[class - lock_classes];
170 for (i = 0; i < ARRAY_SIZE(stats.contention_point); i++)
171 stats.contention_point[i] += pcs->contention_point[i];
173 lock_time_add(&pcs->read_waittime, &stats.read_waittime);
174 lock_time_add(&pcs->write_waittime, &stats.write_waittime);
176 lock_time_add(&pcs->read_holdtime, &stats.read_holdtime);
177 lock_time_add(&pcs->write_holdtime, &stats.write_holdtime);
183 void clear_lock_stats(struct lock_class *class)
187 for_each_possible_cpu(cpu) {
188 struct lock_class_stats *cpu_stats =
189 &per_cpu(lock_stats, cpu)[class - lock_classes];
191 memset(cpu_stats, 0, sizeof(struct lock_class_stats));
193 memset(class->contention_point, 0, sizeof(class->contention_point));
196 static struct lock_class_stats *get_lock_stats(struct lock_class *class)
198 return &get_cpu_var(lock_stats)[class - lock_classes];
201 static void put_lock_stats(struct lock_class_stats *stats)
203 put_cpu_var(lock_stats);
206 static void lock_release_holdtime(struct held_lock *hlock)
208 struct lock_class_stats *stats;
214 holdtime = sched_clock() - hlock->holdtime_stamp;
216 stats = get_lock_stats(hlock->class);
218 lock_time_inc(&stats->read_holdtime, holdtime);
220 lock_time_inc(&stats->write_holdtime, holdtime);
221 put_lock_stats(stats);
224 static inline void lock_release_holdtime(struct held_lock *hlock)
230 * We keep a global list of all lock classes. The list only grows,
231 * never shrinks. The list is only accessed with the lockdep
232 * spinlock lock held.
234 LIST_HEAD(all_lock_classes);
237 * The lockdep classes are in a hash-table as well, for fast lookup:
239 #define CLASSHASH_BITS (MAX_LOCKDEP_KEYS_BITS - 1)
240 #define CLASSHASH_SIZE (1UL << CLASSHASH_BITS)
241 #define CLASSHASH_MASK (CLASSHASH_SIZE - 1)
242 #define __classhashfn(key) ((((unsigned long)key >> CLASSHASH_BITS) + (unsigned long)key) & CLASSHASH_MASK)
243 #define classhashentry(key) (classhash_table + __classhashfn((key)))
245 static struct list_head classhash_table[CLASSHASH_SIZE];
248 * We put the lock dependency chains into a hash-table as well, to cache
251 #define CHAINHASH_BITS (MAX_LOCKDEP_CHAINS_BITS-1)
252 #define CHAINHASH_SIZE (1UL << CHAINHASH_BITS)
253 #define CHAINHASH_MASK (CHAINHASH_SIZE - 1)
254 #define __chainhashfn(chain) \
255 (((chain >> CHAINHASH_BITS) + chain) & CHAINHASH_MASK)
256 #define chainhashentry(chain) (chainhash_table + __chainhashfn((chain)))
258 static struct list_head chainhash_table[CHAINHASH_SIZE];
261 * The hash key of the lock dependency chains is a hash itself too:
262 * it's a hash of all locks taken up to that lock, including that lock.
263 * It's a 64-bit hash, because it's important for the keys to be
266 #define iterate_chain_key(key1, key2) \
267 (((key1) << MAX_LOCKDEP_KEYS_BITS) ^ \
268 ((key1) >> (64-MAX_LOCKDEP_KEYS_BITS)) ^ \
271 void lockdep_off(void)
273 current->lockdep_recursion++;
276 EXPORT_SYMBOL(lockdep_off);
278 void lockdep_on(void)
280 current->lockdep_recursion--;
283 EXPORT_SYMBOL(lockdep_on);
286 * Debugging switches:
290 #define VERY_VERBOSE 0
293 # define HARDIRQ_VERBOSE 1
294 # define SOFTIRQ_VERBOSE 1
296 # define HARDIRQ_VERBOSE 0
297 # define SOFTIRQ_VERBOSE 0
300 #if VERBOSE || HARDIRQ_VERBOSE || SOFTIRQ_VERBOSE
302 * Quick filtering for interesting events:
304 static int class_filter(struct lock_class *class)
308 if (class->name_version == 1 &&
309 !strcmp(class->name, "lockname"))
311 if (class->name_version == 1 &&
312 !strcmp(class->name, "&struct->lockfield"))
315 /* Filter everything else. 1 would be to allow everything else */
320 static int verbose(struct lock_class *class)
323 return class_filter(class);
329 * Stack-trace: tightly packed array of stack backtrace
330 * addresses. Protected by the graph_lock.
332 unsigned long nr_stack_trace_entries;
333 static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];
335 static int save_trace(struct stack_trace *trace)
337 trace->nr_entries = 0;
338 trace->max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries;
339 trace->entries = stack_trace + nr_stack_trace_entries;
343 save_stack_trace(trace);
345 trace->max_entries = trace->nr_entries;
347 nr_stack_trace_entries += trace->nr_entries;
349 if (nr_stack_trace_entries == MAX_STACK_TRACE_ENTRIES) {
350 if (!debug_locks_off_graph_unlock())
353 printk("BUG: MAX_STACK_TRACE_ENTRIES too low!\n");
354 printk("turning off the locking correctness validator.\n");
363 unsigned int nr_hardirq_chains;
364 unsigned int nr_softirq_chains;
365 unsigned int nr_process_chains;
366 unsigned int max_lockdep_depth;
367 unsigned int max_recursion_depth;
369 #ifdef CONFIG_DEBUG_LOCKDEP
371 * We cannot printk in early bootup code. Not even early_printk()
372 * might work. So we mark any initialization errors and printk
373 * about it later on, in lockdep_info().
375 static int lockdep_init_error;
378 * Various lockdep statistics:
380 atomic_t chain_lookup_hits;
381 atomic_t chain_lookup_misses;
382 atomic_t hardirqs_on_events;
383 atomic_t hardirqs_off_events;
384 atomic_t redundant_hardirqs_on;
385 atomic_t redundant_hardirqs_off;
386 atomic_t softirqs_on_events;
387 atomic_t softirqs_off_events;
388 atomic_t redundant_softirqs_on;
389 atomic_t redundant_softirqs_off;
390 atomic_t nr_unused_locks;
391 atomic_t nr_cyclic_checks;
392 atomic_t nr_cyclic_check_recursions;
393 atomic_t nr_find_usage_forwards_checks;
394 atomic_t nr_find_usage_forwards_recursions;
395 atomic_t nr_find_usage_backwards_checks;
396 atomic_t nr_find_usage_backwards_recursions;
397 # define debug_atomic_inc(ptr) atomic_inc(ptr)
398 # define debug_atomic_dec(ptr) atomic_dec(ptr)
399 # define debug_atomic_read(ptr) atomic_read(ptr)
401 # define debug_atomic_inc(ptr) do { } while (0)
402 # define debug_atomic_dec(ptr) do { } while (0)
403 # define debug_atomic_read(ptr) 0
410 static const char *usage_str[] =
412 [LOCK_USED] = "initial-use ",
413 [LOCK_USED_IN_HARDIRQ] = "in-hardirq-W",
414 [LOCK_USED_IN_SOFTIRQ] = "in-softirq-W",
415 [LOCK_ENABLED_SOFTIRQS] = "softirq-on-W",
416 [LOCK_ENABLED_HARDIRQS] = "hardirq-on-W",
417 [LOCK_USED_IN_HARDIRQ_READ] = "in-hardirq-R",
418 [LOCK_USED_IN_SOFTIRQ_READ] = "in-softirq-R",
419 [LOCK_ENABLED_SOFTIRQS_READ] = "softirq-on-R",
420 [LOCK_ENABLED_HARDIRQS_READ] = "hardirq-on-R",
423 const char * __get_key_name(struct lockdep_subclass_key *key, char *str)
425 return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str);
429 get_usage_chars(struct lock_class *class, char *c1, char *c2, char *c3, char *c4)
431 *c1 = '.', *c2 = '.', *c3 = '.', *c4 = '.';
433 if (class->usage_mask & LOCKF_USED_IN_HARDIRQ)
436 if (class->usage_mask & LOCKF_ENABLED_HARDIRQS)
439 if (class->usage_mask & LOCKF_USED_IN_SOFTIRQ)
442 if (class->usage_mask & LOCKF_ENABLED_SOFTIRQS)
445 if (class->usage_mask & LOCKF_ENABLED_HARDIRQS_READ)
447 if (class->usage_mask & LOCKF_USED_IN_HARDIRQ_READ) {
449 if (class->usage_mask & LOCKF_ENABLED_HARDIRQS_READ)
453 if (class->usage_mask & LOCKF_ENABLED_SOFTIRQS_READ)
455 if (class->usage_mask & LOCKF_USED_IN_SOFTIRQ_READ) {
457 if (class->usage_mask & LOCKF_ENABLED_SOFTIRQS_READ)
462 static void print_lock_name(struct lock_class *class)
464 char str[KSYM_NAME_LEN], c1, c2, c3, c4;
467 get_usage_chars(class, &c1, &c2, &c3, &c4);
471 name = __get_key_name(class->key, str);
472 printk(" (%s", name);
474 printk(" (%s", name);
475 if (class->name_version > 1)
476 printk("#%d", class->name_version);
478 printk("/%d", class->subclass);
480 printk("){%c%c%c%c}", c1, c2, c3, c4);
483 static void print_lockdep_cache(struct lockdep_map *lock)
486 char str[KSYM_NAME_LEN];
490 name = __get_key_name(lock->key->subkeys, str);
495 static void print_lock(struct held_lock *hlock)
497 print_lock_name(hlock->class);
499 print_ip_sym(hlock->acquire_ip);
502 static void lockdep_print_held_locks(struct task_struct *curr)
504 int i, depth = curr->lockdep_depth;
507 printk("no locks held by %s/%d.\n", curr->comm, curr->pid);
510 printk("%d lock%s held by %s/%d:\n",
511 depth, depth > 1 ? "s" : "", curr->comm, curr->pid);
513 for (i = 0; i < depth; i++) {
515 print_lock(curr->held_locks + i);
519 static void print_lock_class_header(struct lock_class *class, int depth)
523 printk("%*s->", depth, "");
524 print_lock_name(class);
525 printk(" ops: %lu", class->ops);
528 for (bit = 0; bit < LOCK_USAGE_STATES; bit++) {
529 if (class->usage_mask & (1 << bit)) {
532 len += printk("%*s %s", depth, "", usage_str[bit]);
533 len += printk(" at:\n");
534 print_stack_trace(class->usage_traces + bit, len);
537 printk("%*s }\n", depth, "");
539 printk("%*s ... key at: ",depth,"");
540 print_ip_sym((unsigned long)class->key);
544 * printk all lock dependencies starting at <entry>:
546 static void print_lock_dependencies(struct lock_class *class, int depth)
548 struct lock_list *entry;
550 if (DEBUG_LOCKS_WARN_ON(depth >= 20))
553 print_lock_class_header(class, depth);
555 list_for_each_entry(entry, &class->locks_after, entry) {
556 if (DEBUG_LOCKS_WARN_ON(!entry->class))
559 print_lock_dependencies(entry->class, depth + 1);
561 printk("%*s ... acquired at:\n",depth,"");
562 print_stack_trace(&entry->trace, 2);
567 static void print_kernel_version(void)
569 printk("%s %.*s\n", init_utsname()->release,
570 (int)strcspn(init_utsname()->version, " "),
571 init_utsname()->version);
574 static int very_verbose(struct lock_class *class)
577 return class_filter(class);
583 * Is this the address of a static object:
585 static int static_obj(void *obj)
587 unsigned long start = (unsigned long) &_stext,
588 end = (unsigned long) &_end,
589 addr = (unsigned long) obj;
597 if ((addr >= start) && (addr < end))
604 for_each_possible_cpu(i) {
605 start = (unsigned long) &__per_cpu_start + per_cpu_offset(i);
606 end = (unsigned long) &__per_cpu_start + PERCPU_ENOUGH_ROOM
609 if ((addr >= start) && (addr < end))
617 return is_module_address(addr);
621 * To make lock name printouts unique, we calculate a unique
622 * class->name_version generation counter:
624 static int count_matching_names(struct lock_class *new_class)
626 struct lock_class *class;
629 if (!new_class->name)
632 list_for_each_entry(class, &all_lock_classes, lock_entry) {
633 if (new_class->key - new_class->subclass == class->key)
634 return class->name_version;
635 if (class->name && !strcmp(class->name, new_class->name))
636 count = max(count, class->name_version);
643 * Register a lock's class in the hash-table, if the class is not present
644 * yet. Otherwise we look it up. We cache the result in the lock object
645 * itself, so actual lookup of the hash should be once per lock object.
647 static inline struct lock_class *
648 look_up_lock_class(struct lockdep_map *lock, unsigned int subclass)
650 struct lockdep_subclass_key *key;
651 struct list_head *hash_head;
652 struct lock_class *class;
654 #ifdef CONFIG_DEBUG_LOCKDEP
656 * If the architecture calls into lockdep before initializing
657 * the hashes then we'll warn about it later. (we cannot printk
660 if (unlikely(!lockdep_initialized)) {
662 lockdep_init_error = 1;
667 * Static locks do not have their class-keys yet - for them the key
668 * is the lock object itself:
670 if (unlikely(!lock->key))
671 lock->key = (void *)lock;
674 * NOTE: the class-key must be unique. For dynamic locks, a static
675 * lock_class_key variable is passed in through the mutex_init()
676 * (or spin_lock_init()) call - which acts as the key. For static
677 * locks we use the lock object itself as the key.
679 BUILD_BUG_ON(sizeof(struct lock_class_key) > sizeof(struct lock_class));
681 key = lock->key->subkeys + subclass;
683 hash_head = classhashentry(key);
686 * We can walk the hash lockfree, because the hash only
687 * grows, and we are careful when adding entries to the end:
689 list_for_each_entry(class, hash_head, hash_entry)
690 if (class->key == key)
697 * Register a lock's class in the hash-table, if the class is not present
698 * yet. Otherwise we look it up. We cache the result in the lock object
699 * itself, so actual lookup of the hash should be once per lock object.
701 static inline struct lock_class *
702 register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
704 struct lockdep_subclass_key *key;
705 struct list_head *hash_head;
706 struct lock_class *class;
709 class = look_up_lock_class(lock, subclass);
714 * Debug-check: all keys must be persistent!
716 if (!static_obj(lock->key)) {
718 printk("INFO: trying to register non-static key.\n");
719 printk("the code is fine but needs lockdep annotation.\n");
720 printk("turning off the locking correctness validator.\n");
726 key = lock->key->subkeys + subclass;
727 hash_head = classhashentry(key);
729 raw_local_irq_save(flags);
731 raw_local_irq_restore(flags);
735 * We have to do the hash-walk again, to avoid races
738 list_for_each_entry(class, hash_head, hash_entry)
739 if (class->key == key)
742 * Allocate a new key from the static array, and add it to
745 if (nr_lock_classes >= MAX_LOCKDEP_KEYS) {
746 if (!debug_locks_off_graph_unlock()) {
747 raw_local_irq_restore(flags);
750 raw_local_irq_restore(flags);
752 printk("BUG: MAX_LOCKDEP_KEYS too low!\n");
753 printk("turning off the locking correctness validator.\n");
756 class = lock_classes + nr_lock_classes++;
757 debug_atomic_inc(&nr_unused_locks);
759 class->name = lock->name;
760 class->subclass = subclass;
761 INIT_LIST_HEAD(&class->lock_entry);
762 INIT_LIST_HEAD(&class->locks_before);
763 INIT_LIST_HEAD(&class->locks_after);
764 class->name_version = count_matching_names(class);
766 * We use RCU's safe list-add method to make
767 * parallel walking of the hash-list safe:
769 list_add_tail_rcu(&class->hash_entry, hash_head);
771 if (verbose(class)) {
773 raw_local_irq_restore(flags);
775 printk("\nnew class %p: %s", class->key, class->name);
776 if (class->name_version > 1)
777 printk("#%d", class->name_version);
781 raw_local_irq_save(flags);
783 raw_local_irq_restore(flags);
789 raw_local_irq_restore(flags);
791 if (!subclass || force)
792 lock->class_cache = class;
794 if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))
800 #ifdef CONFIG_PROVE_LOCKING
802 * Allocate a lockdep entry. (assumes the graph_lock held, returns
803 * with NULL on failure)
805 static struct lock_list *alloc_list_entry(void)
807 if (nr_list_entries >= MAX_LOCKDEP_ENTRIES) {
808 if (!debug_locks_off_graph_unlock())
811 printk("BUG: MAX_LOCKDEP_ENTRIES too low!\n");
812 printk("turning off the locking correctness validator.\n");
815 return list_entries + nr_list_entries++;
819 * Add a new dependency to the head of the list:
821 static int add_lock_to_list(struct lock_class *class, struct lock_class *this,
822 struct list_head *head, unsigned long ip, int distance)
824 struct lock_list *entry;
826 * Lock not present yet - get a new dependency struct and
827 * add it to the list:
829 entry = alloc_list_entry();
834 entry->distance = distance;
835 if (!save_trace(&entry->trace))
839 * Since we never remove from the dependency list, the list can
840 * be walked lockless by other CPUs, it's only allocation
841 * that must be protected by the spinlock. But this also means
842 * we must make new entries visible only once writes to the
843 * entry become visible - hence the RCU op:
845 list_add_tail_rcu(&entry->entry, head);
851 * Recursive, forwards-direction lock-dependency checking, used for
852 * both noncyclic checking and for hardirq-unsafe/softirq-unsafe
855 * (to keep the stackframe of the recursive functions small we
856 * use these global variables, and we also mark various helper
857 * functions as noinline.)
859 static struct held_lock *check_source, *check_target;
862 * Print a dependency chain entry (this is only done when a deadlock
863 * has been detected):
866 print_circular_bug_entry(struct lock_list *target, unsigned int depth)
868 if (debug_locks_silent)
870 printk("\n-> #%u", depth);
871 print_lock_name(target->class);
873 print_stack_trace(&target->trace, 6);
879 * When a circular dependency is detected, print the
883 print_circular_bug_header(struct lock_list *entry, unsigned int depth)
885 struct task_struct *curr = current;
887 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
890 printk("\n=======================================================\n");
891 printk( "[ INFO: possible circular locking dependency detected ]\n");
892 print_kernel_version();
893 printk( "-------------------------------------------------------\n");
894 printk("%s/%d is trying to acquire lock:\n",
895 curr->comm, curr->pid);
896 print_lock(check_source);
897 printk("\nbut task is already holding lock:\n");
898 print_lock(check_target);
899 printk("\nwhich lock already depends on the new lock.\n\n");
900 printk("\nthe existing dependency chain (in reverse order) is:\n");
902 print_circular_bug_entry(entry, depth);
907 static noinline int print_circular_bug_tail(void)
909 struct task_struct *curr = current;
910 struct lock_list this;
912 if (debug_locks_silent)
915 this.class = check_source->class;
916 if (!save_trace(&this.trace))
919 print_circular_bug_entry(&this, 0);
921 printk("\nother info that might help us debug this:\n\n");
922 lockdep_print_held_locks(curr);
924 printk("\nstack backtrace:\n");
930 #define RECURSION_LIMIT 40
932 static int noinline print_infinite_recursion_bug(void)
934 if (!debug_locks_off_graph_unlock())
943 * Prove that the dependency graph starting at <entry> can not
944 * lead to <target>. Print an error and return 0 if it does.
947 check_noncircular(struct lock_class *source, unsigned int depth)
949 struct lock_list *entry;
951 debug_atomic_inc(&nr_cyclic_check_recursions);
952 if (depth > max_recursion_depth)
953 max_recursion_depth = depth;
954 if (depth >= RECURSION_LIMIT)
955 return print_infinite_recursion_bug();
957 * Check this lock's dependency list:
959 list_for_each_entry(entry, &source->locks_after, entry) {
960 if (entry->class == check_target->class)
961 return print_circular_bug_header(entry, depth+1);
962 debug_atomic_inc(&nr_cyclic_checks);
963 if (!check_noncircular(entry->class, depth+1))
964 return print_circular_bug_entry(entry, depth+1);
969 #ifdef CONFIG_TRACE_IRQFLAGS
971 * Forwards and backwards subgraph searching, for the purposes of
972 * proving that two subgraphs can be connected by a new dependency
973 * without creating any illegal irq-safe -> irq-unsafe lock dependency.
975 static enum lock_usage_bit find_usage_bit;
976 static struct lock_class *forwards_match, *backwards_match;
979 * Find a node in the forwards-direction dependency sub-graph starting
980 * at <source> that matches <find_usage_bit>.
982 * Return 2 if such a node exists in the subgraph, and put that node
983 * into <forwards_match>.
985 * Return 1 otherwise and keep <forwards_match> unchanged.
989 find_usage_forwards(struct lock_class *source, unsigned int depth)
991 struct lock_list *entry;
994 if (depth > max_recursion_depth)
995 max_recursion_depth = depth;
996 if (depth >= RECURSION_LIMIT)
997 return print_infinite_recursion_bug();
999 debug_atomic_inc(&nr_find_usage_forwards_checks);
1000 if (source->usage_mask & (1 << find_usage_bit)) {
1001 forwards_match = source;
1006 * Check this lock's dependency list:
1008 list_for_each_entry(entry, &source->locks_after, entry) {
1009 debug_atomic_inc(&nr_find_usage_forwards_recursions);
1010 ret = find_usage_forwards(entry->class, depth+1);
1011 if (ret == 2 || ret == 0)
1018 * Find a node in the backwards-direction dependency sub-graph starting
1019 * at <source> that matches <find_usage_bit>.
1021 * Return 2 if such a node exists in the subgraph, and put that node
1022 * into <backwards_match>.
1024 * Return 1 otherwise and keep <backwards_match> unchanged.
1025 * Return 0 on error.
1028 find_usage_backwards(struct lock_class *source, unsigned int depth)
1030 struct lock_list *entry;
1033 if (!__raw_spin_is_locked(&lockdep_lock))
1034 return DEBUG_LOCKS_WARN_ON(1);
1036 if (depth > max_recursion_depth)
1037 max_recursion_depth = depth;
1038 if (depth >= RECURSION_LIMIT)
1039 return print_infinite_recursion_bug();
1041 debug_atomic_inc(&nr_find_usage_backwards_checks);
1042 if (source->usage_mask & (1 << find_usage_bit)) {
1043 backwards_match = source;
1048 * Check this lock's dependency list:
1050 list_for_each_entry(entry, &source->locks_before, entry) {
1051 debug_atomic_inc(&nr_find_usage_backwards_recursions);
1052 ret = find_usage_backwards(entry->class, depth+1);
1053 if (ret == 2 || ret == 0)
1060 print_bad_irq_dependency(struct task_struct *curr,
1061 struct held_lock *prev,
1062 struct held_lock *next,
1063 enum lock_usage_bit bit1,
1064 enum lock_usage_bit bit2,
1065 const char *irqclass)
1067 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1070 printk("\n======================================================\n");
1071 printk( "[ INFO: %s-safe -> %s-unsafe lock order detected ]\n",
1072 irqclass, irqclass);
1073 print_kernel_version();
1074 printk( "------------------------------------------------------\n");
1075 printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
1076 curr->comm, curr->pid,
1077 curr->hardirq_context, hardirq_count() >> HARDIRQ_SHIFT,
1078 curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT,
1079 curr->hardirqs_enabled,
1080 curr->softirqs_enabled);
1083 printk("\nand this task is already holding:\n");
1085 printk("which would create a new lock dependency:\n");
1086 print_lock_name(prev->class);
1088 print_lock_name(next->class);
1091 printk("\nbut this new dependency connects a %s-irq-safe lock:\n",
1093 print_lock_name(backwards_match);
1094 printk("\n... which became %s-irq-safe at:\n", irqclass);
1096 print_stack_trace(backwards_match->usage_traces + bit1, 1);
1098 printk("\nto a %s-irq-unsafe lock:\n", irqclass);
1099 print_lock_name(forwards_match);
1100 printk("\n... which became %s-irq-unsafe at:\n", irqclass);
1103 print_stack_trace(forwards_match->usage_traces + bit2, 1);
1105 printk("\nother info that might help us debug this:\n\n");
1106 lockdep_print_held_locks(curr);
1108 printk("\nthe %s-irq-safe lock's dependencies:\n", irqclass);
1109 print_lock_dependencies(backwards_match, 0);
1111 printk("\nthe %s-irq-unsafe lock's dependencies:\n", irqclass);
1112 print_lock_dependencies(forwards_match, 0);
1114 printk("\nstack backtrace:\n");
1121 check_usage(struct task_struct *curr, struct held_lock *prev,
1122 struct held_lock *next, enum lock_usage_bit bit_backwards,
1123 enum lock_usage_bit bit_forwards, const char *irqclass)
1127 find_usage_bit = bit_backwards;
1128 /* fills in <backwards_match> */
1129 ret = find_usage_backwards(prev->class, 0);
1130 if (!ret || ret == 1)
1133 find_usage_bit = bit_forwards;
1134 ret = find_usage_forwards(next->class, 0);
1135 if (!ret || ret == 1)
1138 return print_bad_irq_dependency(curr, prev, next,
1139 bit_backwards, bit_forwards, irqclass);
1143 check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
1144 struct held_lock *next)
1147 * Prove that the new dependency does not connect a hardirq-safe
1148 * lock with a hardirq-unsafe lock - to achieve this we search
1149 * the backwards-subgraph starting at <prev>, and the
1150 * forwards-subgraph starting at <next>:
1152 if (!check_usage(curr, prev, next, LOCK_USED_IN_HARDIRQ,
1153 LOCK_ENABLED_HARDIRQS, "hard"))
1157 * Prove that the new dependency does not connect a hardirq-safe-read
1158 * lock with a hardirq-unsafe lock - to achieve this we search
1159 * the backwards-subgraph starting at <prev>, and the
1160 * forwards-subgraph starting at <next>:
1162 if (!check_usage(curr, prev, next, LOCK_USED_IN_HARDIRQ_READ,
1163 LOCK_ENABLED_HARDIRQS, "hard-read"))
1167 * Prove that the new dependency does not connect a softirq-safe
1168 * lock with a softirq-unsafe lock - to achieve this we search
1169 * the backwards-subgraph starting at <prev>, and the
1170 * forwards-subgraph starting at <next>:
1172 if (!check_usage(curr, prev, next, LOCK_USED_IN_SOFTIRQ,
1173 LOCK_ENABLED_SOFTIRQS, "soft"))
1176 * Prove that the new dependency does not connect a softirq-safe-read
1177 * lock with a softirq-unsafe lock - to achieve this we search
1178 * the backwards-subgraph starting at <prev>, and the
1179 * forwards-subgraph starting at <next>:
1181 if (!check_usage(curr, prev, next, LOCK_USED_IN_SOFTIRQ_READ,
1182 LOCK_ENABLED_SOFTIRQS, "soft"))
1188 static void inc_chains(void)
1190 if (current->hardirq_context)
1191 nr_hardirq_chains++;
1193 if (current->softirq_context)
1194 nr_softirq_chains++;
1196 nr_process_chains++;
1203 check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
1204 struct held_lock *next)
1209 static inline void inc_chains(void)
1211 nr_process_chains++;
1217 print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
1218 struct held_lock *next)
1220 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1223 printk("\n=============================================\n");
1224 printk( "[ INFO: possible recursive locking detected ]\n");
1225 print_kernel_version();
1226 printk( "---------------------------------------------\n");
1227 printk("%s/%d is trying to acquire lock:\n",
1228 curr->comm, curr->pid);
1230 printk("\nbut task is already holding lock:\n");
1233 printk("\nother info that might help us debug this:\n");
1234 lockdep_print_held_locks(curr);
1236 printk("\nstack backtrace:\n");
1243 * Check whether we are holding such a class already.
1245 * (Note that this has to be done separately, because the graph cannot
1246 * detect such classes of deadlocks.)
1248 * Returns: 0 on deadlock detected, 1 on OK, 2 on recursive read
1251 check_deadlock(struct task_struct *curr, struct held_lock *next,
1252 struct lockdep_map *next_instance, int read)
1254 struct held_lock *prev;
1257 for (i = 0; i < curr->lockdep_depth; i++) {
1258 prev = curr->held_locks + i;
1259 if (prev->class != next->class)
1262 * Allow read-after-read recursion of the same
1263 * lock class (i.e. read_lock(lock)+read_lock(lock)):
1265 if ((read == 2) && prev->read)
1267 return print_deadlock_bug(curr, prev, next);
1273 * There was a chain-cache miss, and we are about to add a new dependency
1274 * to a previous lock. We recursively validate the following rules:
1276 * - would the adding of the <prev> -> <next> dependency create a
1277 * circular dependency in the graph? [== circular deadlock]
1279 * - does the new prev->next dependency connect any hardirq-safe lock
1280 * (in the full backwards-subgraph starting at <prev>) with any
1281 * hardirq-unsafe lock (in the full forwards-subgraph starting at
1282 * <next>)? [== illegal lock inversion with hardirq contexts]
1284 * - does the new prev->next dependency connect any softirq-safe lock
1285 * (in the full backwards-subgraph starting at <prev>) with any
1286 * softirq-unsafe lock (in the full forwards-subgraph starting at
1287 * <next>)? [== illegal lock inversion with softirq contexts]
1289 * any of these scenarios could lead to a deadlock.
1291 * Then if all the validations pass, we add the forwards and backwards
1295 check_prev_add(struct task_struct *curr, struct held_lock *prev,
1296 struct held_lock *next, int distance)
1298 struct lock_list *entry;
1302 * Prove that the new <prev> -> <next> dependency would not
1303 * create a circular dependency in the graph. (We do this by
1304 * forward-recursing into the graph starting at <next>, and
1305 * checking whether we can reach <prev>.)
1307 * We are using global variables to control the recursion, to
1308 * keep the stackframe size of the recursive functions low:
1310 check_source = next;
1311 check_target = prev;
1312 if (!(check_noncircular(next->class, 0)))
1313 return print_circular_bug_tail();
1315 if (!check_prev_add_irq(curr, prev, next))
1319 * For recursive read-locks we do all the dependency checks,
1320 * but we dont store read-triggered dependencies (only
1321 * write-triggered dependencies). This ensures that only the
1322 * write-side dependencies matter, and that if for example a
1323 * write-lock never takes any other locks, then the reads are
1324 * equivalent to a NOP.
1326 if (next->read == 2 || prev->read == 2)
1329 * Is the <prev> -> <next> dependency already present?
1331 * (this may occur even though this is a new chain: consider
1332 * e.g. the L1 -> L2 -> L3 -> L4 and the L5 -> L1 -> L2 -> L3
1333 * chains - the second one will be new, but L1 already has
1334 * L2 added to its dependency list, due to the first chain.)
1336 list_for_each_entry(entry, &prev->class->locks_after, entry) {
1337 if (entry->class == next->class) {
1339 entry->distance = 1;
1345 * Ok, all validations passed, add the new lock
1346 * to the previous lock's dependency list:
1348 ret = add_lock_to_list(prev->class, next->class,
1349 &prev->class->locks_after, next->acquire_ip, distance);
1354 ret = add_lock_to_list(next->class, prev->class,
1355 &next->class->locks_before, next->acquire_ip, distance);
1360 * Debugging printouts:
1362 if (verbose(prev->class) || verbose(next->class)) {
1364 printk("\n new dependency: ");
1365 print_lock_name(prev->class);
1367 print_lock_name(next->class);
1370 return graph_lock();
1376 * Add the dependency to all directly-previous locks that are 'relevant'.
1377 * The ones that are relevant are (in increasing distance from curr):
1378 * all consecutive trylock entries and the final non-trylock entry - or
1379 * the end of this context's lock-chain - whichever comes first.
1382 check_prevs_add(struct task_struct *curr, struct held_lock *next)
1384 int depth = curr->lockdep_depth;
1385 struct held_lock *hlock;
1390 * Depth must not be zero for a non-head lock:
1395 * At least two relevant locks must exist for this
1398 if (curr->held_locks[depth].irq_context !=
1399 curr->held_locks[depth-1].irq_context)
1403 int distance = curr->lockdep_depth - depth + 1;
1404 hlock = curr->held_locks + depth-1;
1406 * Only non-recursive-read entries get new dependencies
1409 if (hlock->read != 2) {
1410 if (!check_prev_add(curr, hlock, next, distance))
1413 * Stop after the first non-trylock entry,
1414 * as non-trylock entries have added their
1415 * own direct dependencies already, so this
1416 * lock is connected to them indirectly:
1418 if (!hlock->trylock)
1423 * End of lock-stack?
1428 * Stop the search if we cross into another context:
1430 if (curr->held_locks[depth].irq_context !=
1431 curr->held_locks[depth-1].irq_context)
1436 if (!debug_locks_off_graph_unlock())
1444 unsigned long nr_lock_chains;
1445 static struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
1448 * Look up a dependency chain. If the key is not present yet then
1449 * add it and return 1 - in this case the new dependency chain is
1450 * validated. If the key is already hashed, return 0.
1451 * (On return with 1 graph_lock is held.)
1453 static inline int lookup_chain_cache(u64 chain_key, struct lock_class *class)
1455 struct list_head *hash_head = chainhashentry(chain_key);
1456 struct lock_chain *chain;
1458 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
1461 * We can walk it lock-free, because entries only get added
1464 list_for_each_entry(chain, hash_head, entry) {
1465 if (chain->chain_key == chain_key) {
1467 debug_atomic_inc(&chain_lookup_hits);
1468 if (very_verbose(class))
1469 printk("\nhash chain already cached, key: "
1470 "%016Lx tail class: [%p] %s\n",
1471 (unsigned long long)chain_key,
1472 class->key, class->name);
1476 if (very_verbose(class))
1477 printk("\nnew hash chain, key: %016Lx tail class: [%p] %s\n",
1478 (unsigned long long)chain_key, class->key, class->name);
1480 * Allocate a new chain entry from the static array, and add
1486 * We have to walk the chain again locked - to avoid duplicates:
1488 list_for_each_entry(chain, hash_head, entry) {
1489 if (chain->chain_key == chain_key) {
1494 if (unlikely(nr_lock_chains >= MAX_LOCKDEP_CHAINS)) {
1495 if (!debug_locks_off_graph_unlock())
1498 printk("BUG: MAX_LOCKDEP_CHAINS too low!\n");
1499 printk("turning off the locking correctness validator.\n");
1502 chain = lock_chains + nr_lock_chains++;
1503 chain->chain_key = chain_key;
1504 list_add_tail_rcu(&chain->entry, hash_head);
1505 debug_atomic_inc(&chain_lookup_misses);
1511 static int validate_chain(struct task_struct *curr, struct lockdep_map *lock,
1512 struct held_lock *hlock, int chain_head)
1515 * Trylock needs to maintain the stack of held locks, but it
1516 * does not add new dependencies, because trylock can be done
1519 * We look up the chain_key and do the O(N^2) check and update of
1520 * the dependencies only if this is a new dependency chain.
1521 * (If lookup_chain_cache() returns with 1 it acquires
1522 * graph_lock for us)
1524 if (!hlock->trylock && (hlock->check == 2) &&
1525 lookup_chain_cache(curr->curr_chain_key, hlock->class)) {
1527 * Check whether last held lock:
1529 * - is irq-safe, if this lock is irq-unsafe
1530 * - is softirq-safe, if this lock is hardirq-unsafe
1532 * And check whether the new lock's dependency graph
1533 * could lead back to the previous lock.
1535 * any of these scenarios could lead to a deadlock. If
1538 int ret = check_deadlock(curr, hlock, lock, hlock->read);
1543 * Mark recursive read, as we jump over it when
1544 * building dependencies (just like we jump over
1550 * Add dependency only if this lock is not the head
1551 * of the chain, and if it's not a secondary read-lock:
1553 if (!chain_head && ret != 2)
1554 if (!check_prevs_add(curr, hlock))
1558 /* after lookup_chain_cache(): */
1559 if (unlikely(!debug_locks))
1565 static inline int validate_chain(struct task_struct *curr,
1566 struct lockdep_map *lock, struct held_lock *hlock,
1574 * We are building curr_chain_key incrementally, so double-check
1575 * it from scratch, to make sure that it's done correctly:
1577 static void check_chain_key(struct task_struct *curr)
1579 #ifdef CONFIG_DEBUG_LOCKDEP
1580 struct held_lock *hlock, *prev_hlock = NULL;
1584 for (i = 0; i < curr->lockdep_depth; i++) {
1585 hlock = curr->held_locks + i;
1586 if (chain_key != hlock->prev_chain_key) {
1588 printk("hm#1, depth: %u [%u], %016Lx != %016Lx\n",
1589 curr->lockdep_depth, i,
1590 (unsigned long long)chain_key,
1591 (unsigned long long)hlock->prev_chain_key);
1595 id = hlock->class - lock_classes;
1596 if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
1599 if (prev_hlock && (prev_hlock->irq_context !=
1600 hlock->irq_context))
1602 chain_key = iterate_chain_key(chain_key, id);
1605 if (chain_key != curr->curr_chain_key) {
1607 printk("hm#2, depth: %u [%u], %016Lx != %016Lx\n",
1608 curr->lockdep_depth, i,
1609 (unsigned long long)chain_key,
1610 (unsigned long long)curr->curr_chain_key);
1617 print_usage_bug(struct task_struct *curr, struct held_lock *this,
1618 enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
1620 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1623 printk("\n=================================\n");
1624 printk( "[ INFO: inconsistent lock state ]\n");
1625 print_kernel_version();
1626 printk( "---------------------------------\n");
1628 printk("inconsistent {%s} -> {%s} usage.\n",
1629 usage_str[prev_bit], usage_str[new_bit]);
1631 printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] takes:\n",
1632 curr->comm, curr->pid,
1633 trace_hardirq_context(curr), hardirq_count() >> HARDIRQ_SHIFT,
1634 trace_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT,
1635 trace_hardirqs_enabled(curr),
1636 trace_softirqs_enabled(curr));
1639 printk("{%s} state was registered at:\n", usage_str[prev_bit]);
1640 print_stack_trace(this->class->usage_traces + prev_bit, 1);
1642 print_irqtrace_events(curr);
1643 printk("\nother info that might help us debug this:\n");
1644 lockdep_print_held_locks(curr);
1646 printk("\nstack backtrace:\n");
1653 * Print out an error if an invalid bit is set:
1656 valid_state(struct task_struct *curr, struct held_lock *this,
1657 enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit)
1659 if (unlikely(this->class->usage_mask & (1 << bad_bit)))
1660 return print_usage_bug(curr, this, bad_bit, new_bit);
1664 static int mark_lock(struct task_struct *curr, struct held_lock *this,
1665 enum lock_usage_bit new_bit);
1667 #ifdef CONFIG_TRACE_IRQFLAGS
1670 * print irq inversion bug:
1673 print_irq_inversion_bug(struct task_struct *curr, struct lock_class *other,
1674 struct held_lock *this, int forwards,
1675 const char *irqclass)
1677 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1680 printk("\n=========================================================\n");
1681 printk( "[ INFO: possible irq lock inversion dependency detected ]\n");
1682 print_kernel_version();
1683 printk( "---------------------------------------------------------\n");
1684 printk("%s/%d just changed the state of lock:\n",
1685 curr->comm, curr->pid);
1688 printk("but this lock took another, %s-irq-unsafe lock in the past:\n", irqclass);
1690 printk("but this lock was taken by another, %s-irq-safe lock in the past:\n", irqclass);
1691 print_lock_name(other);
1692 printk("\n\nand interrupts could create inverse lock ordering between them.\n\n");
1694 printk("\nother info that might help us debug this:\n");
1695 lockdep_print_held_locks(curr);
1697 printk("\nthe first lock's dependencies:\n");
1698 print_lock_dependencies(this->class, 0);
1700 printk("\nthe second lock's dependencies:\n");
1701 print_lock_dependencies(other, 0);
1703 printk("\nstack backtrace:\n");
1710 * Prove that in the forwards-direction subgraph starting at <this>
1711 * there is no lock matching <mask>:
1714 check_usage_forwards(struct task_struct *curr, struct held_lock *this,
1715 enum lock_usage_bit bit, const char *irqclass)
1719 find_usage_bit = bit;
1720 /* fills in <forwards_match> */
1721 ret = find_usage_forwards(this->class, 0);
1722 if (!ret || ret == 1)
1725 return print_irq_inversion_bug(curr, forwards_match, this, 1, irqclass);
1729 * Prove that in the backwards-direction subgraph starting at <this>
1730 * there is no lock matching <mask>:
1733 check_usage_backwards(struct task_struct *curr, struct held_lock *this,
1734 enum lock_usage_bit bit, const char *irqclass)
1738 find_usage_bit = bit;
1739 /* fills in <backwards_match> */
1740 ret = find_usage_backwards(this->class, 0);
1741 if (!ret || ret == 1)
1744 return print_irq_inversion_bug(curr, backwards_match, this, 0, irqclass);
1747 void print_irqtrace_events(struct task_struct *curr)
1749 printk("irq event stamp: %u\n", curr->irq_events);
1750 printk("hardirqs last enabled at (%u): ", curr->hardirq_enable_event);
1751 print_ip_sym(curr->hardirq_enable_ip);
1752 printk("hardirqs last disabled at (%u): ", curr->hardirq_disable_event);
1753 print_ip_sym(curr->hardirq_disable_ip);
1754 printk("softirqs last enabled at (%u): ", curr->softirq_enable_event);
1755 print_ip_sym(curr->softirq_enable_ip);
1756 printk("softirqs last disabled at (%u): ", curr->softirq_disable_event);
1757 print_ip_sym(curr->softirq_disable_ip);
1760 static int hardirq_verbose(struct lock_class *class)
1763 return class_filter(class);
1768 static int softirq_verbose(struct lock_class *class)
1771 return class_filter(class);
1776 #define STRICT_READ_CHECKS 1
1778 static int mark_lock_irq(struct task_struct *curr, struct held_lock *this,
1779 enum lock_usage_bit new_bit)
1784 case LOCK_USED_IN_HARDIRQ:
1785 if (!valid_state(curr, this, new_bit, LOCK_ENABLED_HARDIRQS))
1787 if (!valid_state(curr, this, new_bit,
1788 LOCK_ENABLED_HARDIRQS_READ))
1791 * just marked it hardirq-safe, check that this lock
1792 * took no hardirq-unsafe lock in the past:
1794 if (!check_usage_forwards(curr, this,
1795 LOCK_ENABLED_HARDIRQS, "hard"))
1797 #if STRICT_READ_CHECKS
1799 * just marked it hardirq-safe, check that this lock
1800 * took no hardirq-unsafe-read lock in the past:
1802 if (!check_usage_forwards(curr, this,
1803 LOCK_ENABLED_HARDIRQS_READ, "hard-read"))
1806 if (hardirq_verbose(this->class))
1809 case LOCK_USED_IN_SOFTIRQ:
1810 if (!valid_state(curr, this, new_bit, LOCK_ENABLED_SOFTIRQS))
1812 if (!valid_state(curr, this, new_bit,
1813 LOCK_ENABLED_SOFTIRQS_READ))
1816 * just marked it softirq-safe, check that this lock
1817 * took no softirq-unsafe lock in the past:
1819 if (!check_usage_forwards(curr, this,
1820 LOCK_ENABLED_SOFTIRQS, "soft"))
1822 #if STRICT_READ_CHECKS
1824 * just marked it softirq-safe, check that this lock
1825 * took no softirq-unsafe-read lock in the past:
1827 if (!check_usage_forwards(curr, this,
1828 LOCK_ENABLED_SOFTIRQS_READ, "soft-read"))
1831 if (softirq_verbose(this->class))
1834 case LOCK_USED_IN_HARDIRQ_READ:
1835 if (!valid_state(curr, this, new_bit, LOCK_ENABLED_HARDIRQS))
1838 * just marked it hardirq-read-safe, check that this lock
1839 * took no hardirq-unsafe lock in the past:
1841 if (!check_usage_forwards(curr, this,
1842 LOCK_ENABLED_HARDIRQS, "hard"))
1844 if (hardirq_verbose(this->class))
1847 case LOCK_USED_IN_SOFTIRQ_READ:
1848 if (!valid_state(curr, this, new_bit, LOCK_ENABLED_SOFTIRQS))
1851 * just marked it softirq-read-safe, check that this lock
1852 * took no softirq-unsafe lock in the past:
1854 if (!check_usage_forwards(curr, this,
1855 LOCK_ENABLED_SOFTIRQS, "soft"))
1857 if (softirq_verbose(this->class))
1860 case LOCK_ENABLED_HARDIRQS:
1861 if (!valid_state(curr, this, new_bit, LOCK_USED_IN_HARDIRQ))
1863 if (!valid_state(curr, this, new_bit,
1864 LOCK_USED_IN_HARDIRQ_READ))
1867 * just marked it hardirq-unsafe, check that no hardirq-safe
1868 * lock in the system ever took it in the past:
1870 if (!check_usage_backwards(curr, this,
1871 LOCK_USED_IN_HARDIRQ, "hard"))
1873 #if STRICT_READ_CHECKS
1875 * just marked it hardirq-unsafe, check that no
1876 * hardirq-safe-read lock in the system ever took
1879 if (!check_usage_backwards(curr, this,
1880 LOCK_USED_IN_HARDIRQ_READ, "hard-read"))
1883 if (hardirq_verbose(this->class))
1886 case LOCK_ENABLED_SOFTIRQS:
1887 if (!valid_state(curr, this, new_bit, LOCK_USED_IN_SOFTIRQ))
1889 if (!valid_state(curr, this, new_bit,
1890 LOCK_USED_IN_SOFTIRQ_READ))
1893 * just marked it softirq-unsafe, check that no softirq-safe
1894 * lock in the system ever took it in the past:
1896 if (!check_usage_backwards(curr, this,
1897 LOCK_USED_IN_SOFTIRQ, "soft"))
1899 #if STRICT_READ_CHECKS
1901 * just marked it softirq-unsafe, check that no
1902 * softirq-safe-read lock in the system ever took
1905 if (!check_usage_backwards(curr, this,
1906 LOCK_USED_IN_SOFTIRQ_READ, "soft-read"))
1909 if (softirq_verbose(this->class))
1912 case LOCK_ENABLED_HARDIRQS_READ:
1913 if (!valid_state(curr, this, new_bit, LOCK_USED_IN_HARDIRQ))
1915 #if STRICT_READ_CHECKS
1917 * just marked it hardirq-read-unsafe, check that no
1918 * hardirq-safe lock in the system ever took it in the past:
1920 if (!check_usage_backwards(curr, this,
1921 LOCK_USED_IN_HARDIRQ, "hard"))
1924 if (hardirq_verbose(this->class))
1927 case LOCK_ENABLED_SOFTIRQS_READ:
1928 if (!valid_state(curr, this, new_bit, LOCK_USED_IN_SOFTIRQ))
1930 #if STRICT_READ_CHECKS
1932 * just marked it softirq-read-unsafe, check that no
1933 * softirq-safe lock in the system ever took it in the past:
1935 if (!check_usage_backwards(curr, this,
1936 LOCK_USED_IN_SOFTIRQ, "soft"))
1939 if (softirq_verbose(this->class))
1951 * Mark all held locks with a usage bit:
1954 mark_held_locks(struct task_struct *curr, int hardirq)
1956 enum lock_usage_bit usage_bit;
1957 struct held_lock *hlock;
1960 for (i = 0; i < curr->lockdep_depth; i++) {
1961 hlock = curr->held_locks + i;
1965 usage_bit = LOCK_ENABLED_HARDIRQS_READ;
1967 usage_bit = LOCK_ENABLED_HARDIRQS;
1970 usage_bit = LOCK_ENABLED_SOFTIRQS_READ;
1972 usage_bit = LOCK_ENABLED_SOFTIRQS;
1974 if (!mark_lock(curr, hlock, usage_bit))
1982 * Debugging helper: via this flag we know that we are in
1983 * 'early bootup code', and will warn about any invalid irqs-on event:
1985 static int early_boot_irqs_enabled;
1987 void early_boot_irqs_off(void)
1989 early_boot_irqs_enabled = 0;
1992 void early_boot_irqs_on(void)
1994 early_boot_irqs_enabled = 1;
1998 * Hardirqs will be enabled:
2000 void trace_hardirqs_on(void)
2002 struct task_struct *curr = current;
2005 if (unlikely(!debug_locks || current->lockdep_recursion))
2008 if (DEBUG_LOCKS_WARN_ON(unlikely(!early_boot_irqs_enabled)))
2011 if (unlikely(curr->hardirqs_enabled)) {
2012 debug_atomic_inc(&redundant_hardirqs_on);
2015 /* we'll do an OFF -> ON transition: */
2016 curr->hardirqs_enabled = 1;
2017 ip = (unsigned long) __builtin_return_address(0);
2019 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2021 if (DEBUG_LOCKS_WARN_ON(current->hardirq_context))
2024 * We are going to turn hardirqs on, so set the
2025 * usage bit for all held locks:
2027 if (!mark_held_locks(curr, 1))
2030 * If we have softirqs enabled, then set the usage
2031 * bit for all held locks. (disabled hardirqs prevented
2032 * this bit from being set before)
2034 if (curr->softirqs_enabled)
2035 if (!mark_held_locks(curr, 0))
2038 curr->hardirq_enable_ip = ip;
2039 curr->hardirq_enable_event = ++curr->irq_events;
2040 debug_atomic_inc(&hardirqs_on_events);
2043 EXPORT_SYMBOL(trace_hardirqs_on);
2046 * Hardirqs were disabled:
2048 void trace_hardirqs_off(void)
2050 struct task_struct *curr = current;
2052 if (unlikely(!debug_locks || current->lockdep_recursion))
2055 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2058 if (curr->hardirqs_enabled) {
2060 * We have done an ON -> OFF transition:
2062 curr->hardirqs_enabled = 0;
2063 curr->hardirq_disable_ip = _RET_IP_;
2064 curr->hardirq_disable_event = ++curr->irq_events;
2065 debug_atomic_inc(&hardirqs_off_events);
2067 debug_atomic_inc(&redundant_hardirqs_off);
2070 EXPORT_SYMBOL(trace_hardirqs_off);
2073 * Softirqs will be enabled:
2075 void trace_softirqs_on(unsigned long ip)
2077 struct task_struct *curr = current;
2079 if (unlikely(!debug_locks))
2082 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2085 if (curr->softirqs_enabled) {
2086 debug_atomic_inc(&redundant_softirqs_on);
2091 * We'll do an OFF -> ON transition:
2093 curr->softirqs_enabled = 1;
2094 curr->softirq_enable_ip = ip;
2095 curr->softirq_enable_event = ++curr->irq_events;
2096 debug_atomic_inc(&softirqs_on_events);
2098 * We are going to turn softirqs on, so set the
2099 * usage bit for all held locks, if hardirqs are
2102 if (curr->hardirqs_enabled)
2103 mark_held_locks(curr, 0);
2107 * Softirqs were disabled:
2109 void trace_softirqs_off(unsigned long ip)
2111 struct task_struct *curr = current;
2113 if (unlikely(!debug_locks))
2116 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2119 if (curr->softirqs_enabled) {
2121 * We have done an ON -> OFF transition:
2123 curr->softirqs_enabled = 0;
2124 curr->softirq_disable_ip = ip;
2125 curr->softirq_disable_event = ++curr->irq_events;
2126 debug_atomic_inc(&softirqs_off_events);
2127 DEBUG_LOCKS_WARN_ON(!softirq_count());
2129 debug_atomic_inc(&redundant_softirqs_off);
2132 static int mark_irqflags(struct task_struct *curr, struct held_lock *hlock)
2135 * If non-trylock use in a hardirq or softirq context, then
2136 * mark the lock as used in these contexts:
2138 if (!hlock->trylock) {
2140 if (curr->hardirq_context)
2141 if (!mark_lock(curr, hlock,
2142 LOCK_USED_IN_HARDIRQ_READ))
2144 if (curr->softirq_context)
2145 if (!mark_lock(curr, hlock,
2146 LOCK_USED_IN_SOFTIRQ_READ))
2149 if (curr->hardirq_context)
2150 if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ))
2152 if (curr->softirq_context)
2153 if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ))
2157 if (!hlock->hardirqs_off) {
2159 if (!mark_lock(curr, hlock,
2160 LOCK_ENABLED_HARDIRQS_READ))
2162 if (curr->softirqs_enabled)
2163 if (!mark_lock(curr, hlock,
2164 LOCK_ENABLED_SOFTIRQS_READ))
2167 if (!mark_lock(curr, hlock,
2168 LOCK_ENABLED_HARDIRQS))
2170 if (curr->softirqs_enabled)
2171 if (!mark_lock(curr, hlock,
2172 LOCK_ENABLED_SOFTIRQS))
2180 static int separate_irq_context(struct task_struct *curr,
2181 struct held_lock *hlock)
2183 unsigned int depth = curr->lockdep_depth;
2186 * Keep track of points where we cross into an interrupt context:
2188 hlock->irq_context = 2*(curr->hardirq_context ? 1 : 0) +
2189 curr->softirq_context;
2191 struct held_lock *prev_hlock;
2193 prev_hlock = curr->held_locks + depth-1;
2195 * If we cross into another context, reset the
2196 * hash key (this also prevents the checking and the
2197 * adding of the dependency to 'prev'):
2199 if (prev_hlock->irq_context != hlock->irq_context)
2208 int mark_lock_irq(struct task_struct *curr, struct held_lock *this,
2209 enum lock_usage_bit new_bit)
2215 static inline int mark_irqflags(struct task_struct *curr,
2216 struct held_lock *hlock)
2221 static inline int separate_irq_context(struct task_struct *curr,
2222 struct held_lock *hlock)
2230 * Mark a lock with a usage bit, and validate the state transition:
2232 static int mark_lock(struct task_struct *curr, struct held_lock *this,
2233 enum lock_usage_bit new_bit)
2235 unsigned int new_mask = 1 << new_bit, ret = 1;
2238 * If already set then do not dirty the cacheline,
2239 * nor do any checks:
2241 if (likely(this->class->usage_mask & new_mask))
2247 * Make sure we didnt race:
2249 if (unlikely(this->class->usage_mask & new_mask)) {
2254 this->class->usage_mask |= new_mask;
2256 if (!save_trace(this->class->usage_traces + new_bit))
2260 case LOCK_USED_IN_HARDIRQ:
2261 case LOCK_USED_IN_SOFTIRQ:
2262 case LOCK_USED_IN_HARDIRQ_READ:
2263 case LOCK_USED_IN_SOFTIRQ_READ:
2264 case LOCK_ENABLED_HARDIRQS:
2265 case LOCK_ENABLED_SOFTIRQS:
2266 case LOCK_ENABLED_HARDIRQS_READ:
2267 case LOCK_ENABLED_SOFTIRQS_READ:
2268 ret = mark_lock_irq(curr, this, new_bit);
2274 * Add it to the global list of classes:
2276 list_add_tail_rcu(&this->class->lock_entry, &all_lock_classes);
2277 debug_atomic_dec(&nr_unused_locks);
2280 if (!debug_locks_off_graph_unlock())
2289 * We must printk outside of the graph_lock:
2292 printk("\nmarked lock as {%s}:\n", usage_str[new_bit]);
2294 print_irqtrace_events(curr);
2302 * Initialize a lock instance's lock-class mapping info:
2304 void lockdep_init_map(struct lockdep_map *lock, const char *name,
2305 struct lock_class_key *key, int subclass)
2307 if (unlikely(!debug_locks))
2310 if (DEBUG_LOCKS_WARN_ON(!key))
2312 if (DEBUG_LOCKS_WARN_ON(!name))
2315 * Sanity check, the lock-class key must be persistent:
2317 if (!static_obj(key)) {
2318 printk("BUG: key %p not in .data!\n", key);
2319 DEBUG_LOCKS_WARN_ON(1);
2324 lock->class_cache = NULL;
2326 register_lock_class(lock, subclass, 1);
2329 EXPORT_SYMBOL_GPL(lockdep_init_map);
2332 * This gets called for every mutex_lock*()/spin_lock*() operation.
2333 * We maintain the dependency maps and validate the locking attempt:
2335 static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
2336 int trylock, int read, int check, int hardirqs_off,
2339 struct task_struct *curr = current;
2340 struct lock_class *class = NULL;
2341 struct held_lock *hlock;
2342 unsigned int depth, id;
2349 if (unlikely(!debug_locks))
2352 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2355 if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
2357 printk("BUG: MAX_LOCKDEP_SUBCLASSES too low!\n");
2358 printk("turning off the locking correctness validator.\n");
2363 class = lock->class_cache;
2365 * Not cached yet or subclass?
2367 if (unlikely(!class)) {
2368 class = register_lock_class(lock, subclass, 0);
2372 debug_atomic_inc((atomic_t *)&class->ops);
2373 if (very_verbose(class)) {
2374 printk("\nacquire class [%p] %s", class->key, class->name);
2375 if (class->name_version > 1)
2376 printk("#%d", class->name_version);
2382 * Add the lock to the list of currently held locks.
2383 * (we dont increase the depth just yet, up until the
2384 * dependency checks are done)
2386 depth = curr->lockdep_depth;
2387 if (DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH))
2390 hlock = curr->held_locks + depth;
2392 hlock->class = class;
2393 hlock->acquire_ip = ip;
2394 hlock->instance = lock;
2395 hlock->trylock = trylock;
2397 hlock->check = check;
2398 hlock->hardirqs_off = hardirqs_off;
2399 #ifdef CONFIG_LOCK_STAT
2400 hlock->waittime_stamp = 0;
2401 hlock->holdtime_stamp = sched_clock();
2404 if (check == 2 && !mark_irqflags(curr, hlock))
2407 /* mark it as used: */
2408 if (!mark_lock(curr, hlock, LOCK_USED))
2412 * Calculate the chain hash: it's the combined has of all the
2413 * lock keys along the dependency chain. We save the hash value
2414 * at every step so that we can get the current hash easily
2415 * after unlock. The chain hash is then used to cache dependency
2418 * The 'key ID' is what is the most compact key value to drive
2419 * the hash, not class->key.
2421 id = class - lock_classes;
2422 if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
2425 chain_key = curr->curr_chain_key;
2427 if (DEBUG_LOCKS_WARN_ON(chain_key != 0))
2432 hlock->prev_chain_key = chain_key;
2433 if (separate_irq_context(curr, hlock)) {
2437 chain_key = iterate_chain_key(chain_key, id);
2438 curr->curr_chain_key = chain_key;
2440 if (!validate_chain(curr, lock, hlock, chain_head))
2443 curr->lockdep_depth++;
2444 check_chain_key(curr);
2445 #ifdef CONFIG_DEBUG_LOCKDEP
2446 if (unlikely(!debug_locks))
2449 if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
2451 printk("BUG: MAX_LOCK_DEPTH too low!\n");
2452 printk("turning off the locking correctness validator.\n");
2456 if (unlikely(curr->lockdep_depth > max_lockdep_depth))
2457 max_lockdep_depth = curr->lockdep_depth;
2463 print_unlock_inbalance_bug(struct task_struct *curr, struct lockdep_map *lock,
2466 if (!debug_locks_off())
2468 if (debug_locks_silent)
2471 printk("\n=====================================\n");
2472 printk( "[ BUG: bad unlock balance detected! ]\n");
2473 printk( "-------------------------------------\n");
2474 printk("%s/%d is trying to release lock (",
2475 curr->comm, curr->pid);
2476 print_lockdep_cache(lock);
2479 printk("but there are no more locks to release!\n");
2480 printk("\nother info that might help us debug this:\n");
2481 lockdep_print_held_locks(curr);
2483 printk("\nstack backtrace:\n");
2490 * Common debugging checks for both nested and non-nested unlock:
2492 static int check_unlock(struct task_struct *curr, struct lockdep_map *lock,
2495 if (unlikely(!debug_locks))
2497 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2500 if (curr->lockdep_depth <= 0)
2501 return print_unlock_inbalance_bug(curr, lock, ip);
2507 * Remove the lock to the list of currently held locks in a
2508 * potentially non-nested (out of order) manner. This is a
2509 * relatively rare operation, as all the unlock APIs default
2510 * to nested mode (which uses lock_release()):
2513 lock_release_non_nested(struct task_struct *curr,
2514 struct lockdep_map *lock, unsigned long ip)
2516 struct held_lock *hlock, *prev_hlock;
2521 * Check whether the lock exists in the current stack
2524 depth = curr->lockdep_depth;
2525 if (DEBUG_LOCKS_WARN_ON(!depth))
2529 for (i = depth-1; i >= 0; i--) {
2530 hlock = curr->held_locks + i;
2532 * We must not cross into another context:
2534 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
2536 if (hlock->instance == lock)
2540 return print_unlock_inbalance_bug(curr, lock, ip);
2543 lock_release_holdtime(hlock);
2546 * We have the right lock to unlock, 'hlock' points to it.
2547 * Now we remove it from the stack, and add back the other
2548 * entries (if any), recalculating the hash along the way:
2550 curr->lockdep_depth = i;
2551 curr->curr_chain_key = hlock->prev_chain_key;
2553 for (i++; i < depth; i++) {
2554 hlock = curr->held_locks + i;
2555 if (!__lock_acquire(hlock->instance,
2556 hlock->class->subclass, hlock->trylock,
2557 hlock->read, hlock->check, hlock->hardirqs_off,
2562 if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - 1))
2568 * Remove the lock to the list of currently held locks - this gets
2569 * called on mutex_unlock()/spin_unlock*() (or on a failed
2570 * mutex_lock_interruptible()). This is done for unlocks that nest
2571 * perfectly. (i.e. the current top of the lock-stack is unlocked)
2573 static int lock_release_nested(struct task_struct *curr,
2574 struct lockdep_map *lock, unsigned long ip)
2576 struct held_lock *hlock;
2580 * Pop off the top of the lock stack:
2582 depth = curr->lockdep_depth - 1;
2583 hlock = curr->held_locks + depth;
2586 * Is the unlock non-nested:
2588 if (hlock->instance != lock)
2589 return lock_release_non_nested(curr, lock, ip);
2590 curr->lockdep_depth--;
2592 if (DEBUG_LOCKS_WARN_ON(!depth && (hlock->prev_chain_key != 0)))
2595 curr->curr_chain_key = hlock->prev_chain_key;
2597 lock_release_holdtime(hlock);
2599 #ifdef CONFIG_DEBUG_LOCKDEP
2600 hlock->prev_chain_key = 0;
2601 hlock->class = NULL;
2602 hlock->acquire_ip = 0;
2603 hlock->irq_context = 0;
2609 * Remove the lock to the list of currently held locks - this gets
2610 * called on mutex_unlock()/spin_unlock*() (or on a failed
2611 * mutex_lock_interruptible()). This is done for unlocks that nest
2612 * perfectly. (i.e. the current top of the lock-stack is unlocked)
2615 __lock_release(struct lockdep_map *lock, int nested, unsigned long ip)
2617 struct task_struct *curr = current;
2619 if (!check_unlock(curr, lock, ip))
2623 if (!lock_release_nested(curr, lock, ip))
2626 if (!lock_release_non_nested(curr, lock, ip))
2630 check_chain_key(curr);
2634 * Check whether we follow the irq-flags state precisely:
2636 static void check_flags(unsigned long flags)
2638 #if defined(CONFIG_DEBUG_LOCKDEP) && defined(CONFIG_TRACE_IRQFLAGS)
2642 if (irqs_disabled_flags(flags))
2643 DEBUG_LOCKS_WARN_ON(current->hardirqs_enabled);
2645 DEBUG_LOCKS_WARN_ON(!current->hardirqs_enabled);
2648 * We dont accurately track softirq state in e.g.
2649 * hardirq contexts (such as on 4KSTACKS), so only
2650 * check if not in hardirq contexts:
2652 if (!hardirq_count()) {
2653 if (softirq_count())
2654 DEBUG_LOCKS_WARN_ON(current->softirqs_enabled);
2656 DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled);
2660 print_irqtrace_events(current);
2665 * We are not always called with irqs disabled - do that here,
2666 * and also avoid lockdep recursion:
2668 void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
2669 int trylock, int read, int check, unsigned long ip)
2671 unsigned long flags;
2673 if (unlikely(!lock_stat && !prove_locking))
2676 if (unlikely(current->lockdep_recursion))
2679 raw_local_irq_save(flags);
2682 current->lockdep_recursion = 1;
2683 __lock_acquire(lock, subclass, trylock, read, check,
2684 irqs_disabled_flags(flags), ip);
2685 current->lockdep_recursion = 0;
2686 raw_local_irq_restore(flags);
2689 EXPORT_SYMBOL_GPL(lock_acquire);
2691 void lock_release(struct lockdep_map *lock, int nested, unsigned long ip)
2693 unsigned long flags;
2695 if (unlikely(!lock_stat && !prove_locking))
2698 if (unlikely(current->lockdep_recursion))
2701 raw_local_irq_save(flags);
2703 current->lockdep_recursion = 1;
2704 __lock_release(lock, nested, ip);
2705 current->lockdep_recursion = 0;
2706 raw_local_irq_restore(flags);
2709 EXPORT_SYMBOL_GPL(lock_release);
2711 #ifdef CONFIG_LOCK_STAT
2713 print_lock_contention_bug(struct task_struct *curr, struct lockdep_map *lock,
2716 if (!debug_locks_off())
2718 if (debug_locks_silent)
2721 printk("\n=================================\n");
2722 printk( "[ BUG: bad contention detected! ]\n");
2723 printk( "---------------------------------\n");
2724 printk("%s/%d is trying to contend lock (",
2725 curr->comm, curr->pid);
2726 print_lockdep_cache(lock);
2729 printk("but there are no locks held!\n");
2730 printk("\nother info that might help us debug this:\n");
2731 lockdep_print_held_locks(curr);
2733 printk("\nstack backtrace:\n");
2740 __lock_contended(struct lockdep_map *lock, unsigned long ip)
2742 struct task_struct *curr = current;
2743 struct held_lock *hlock, *prev_hlock;
2744 struct lock_class_stats *stats;
2748 depth = curr->lockdep_depth;
2749 if (DEBUG_LOCKS_WARN_ON(!depth))
2753 for (i = depth-1; i >= 0; i--) {
2754 hlock = curr->held_locks + i;
2756 * We must not cross into another context:
2758 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
2760 if (hlock->instance == lock)
2764 print_lock_contention_bug(curr, lock, ip);
2768 hlock->waittime_stamp = sched_clock();
2770 point = lock_contention_point(hlock->class, ip);
2772 stats = get_lock_stats(hlock->class);
2773 if (point < ARRAY_SIZE(stats->contention_point))
2774 stats->contention_point[i]++;
2775 put_lock_stats(stats);
2779 __lock_acquired(struct lockdep_map *lock)
2781 struct task_struct *curr = current;
2782 struct held_lock *hlock, *prev_hlock;
2783 struct lock_class_stats *stats;
2789 depth = curr->lockdep_depth;
2790 if (DEBUG_LOCKS_WARN_ON(!depth))
2794 for (i = depth-1; i >= 0; i--) {
2795 hlock = curr->held_locks + i;
2797 * We must not cross into another context:
2799 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
2801 if (hlock->instance == lock)
2805 print_lock_contention_bug(curr, lock, _RET_IP_);
2809 if (!hlock->waittime_stamp)
2812 now = sched_clock();
2813 waittime = now - hlock->waittime_stamp;
2814 hlock->holdtime_stamp = now;
2816 stats = get_lock_stats(hlock->class);
2818 lock_time_inc(&stats->read_waittime, waittime);
2820 lock_time_inc(&stats->write_waittime, waittime);
2821 put_lock_stats(stats);
2824 void lock_contended(struct lockdep_map *lock, unsigned long ip)
2826 unsigned long flags;
2828 if (unlikely(!lock_stat))
2831 if (unlikely(current->lockdep_recursion))
2834 raw_local_irq_save(flags);
2836 current->lockdep_recursion = 1;
2837 __lock_contended(lock, ip);
2838 current->lockdep_recursion = 0;
2839 raw_local_irq_restore(flags);
2841 EXPORT_SYMBOL_GPL(lock_contended);
2843 void lock_acquired(struct lockdep_map *lock)
2845 unsigned long flags;
2847 if (unlikely(!lock_stat))
2850 if (unlikely(current->lockdep_recursion))
2853 raw_local_irq_save(flags);
2855 current->lockdep_recursion = 1;
2856 __lock_acquired(lock);
2857 current->lockdep_recursion = 0;
2858 raw_local_irq_restore(flags);
2860 EXPORT_SYMBOL_GPL(lock_acquired);
2864 * Used by the testsuite, sanitize the validator state
2865 * after a simulated failure:
2868 void lockdep_reset(void)
2870 unsigned long flags;
2873 raw_local_irq_save(flags);
2874 current->curr_chain_key = 0;
2875 current->lockdep_depth = 0;
2876 current->lockdep_recursion = 0;
2877 memset(current->held_locks, 0, MAX_LOCK_DEPTH*sizeof(struct held_lock));
2878 nr_hardirq_chains = 0;
2879 nr_softirq_chains = 0;
2880 nr_process_chains = 0;
2882 for (i = 0; i < CHAINHASH_SIZE; i++)
2883 INIT_LIST_HEAD(chainhash_table + i);
2884 raw_local_irq_restore(flags);
2887 static void zap_class(struct lock_class *class)
2892 * Remove all dependencies this lock is
2895 for (i = 0; i < nr_list_entries; i++) {
2896 if (list_entries[i].class == class)
2897 list_del_rcu(&list_entries[i].entry);
2900 * Unhash the class and remove it from the all_lock_classes list:
2902 list_del_rcu(&class->hash_entry);
2903 list_del_rcu(&class->lock_entry);
2907 static inline int within(void *addr, void *start, unsigned long size)
2909 return addr >= start && addr < start + size;
2912 void lockdep_free_key_range(void *start, unsigned long size)
2914 struct lock_class *class, *next;
2915 struct list_head *head;
2916 unsigned long flags;
2919 raw_local_irq_save(flags);
2923 * Unhash all classes that were created by this module:
2925 for (i = 0; i < CLASSHASH_SIZE; i++) {
2926 head = classhash_table + i;
2927 if (list_empty(head))
2929 list_for_each_entry_safe(class, next, head, hash_entry)
2930 if (within(class->key, start, size))
2935 raw_local_irq_restore(flags);
2938 void lockdep_reset_lock(struct lockdep_map *lock)
2940 struct lock_class *class, *next;
2941 struct list_head *head;
2942 unsigned long flags;
2945 raw_local_irq_save(flags);
2948 * Remove all classes this lock might have:
2950 for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) {
2952 * If the class exists we look it up and zap it:
2954 class = look_up_lock_class(lock, j);
2959 * Debug check: in the end all mapped classes should
2963 for (i = 0; i < CLASSHASH_SIZE; i++) {
2964 head = classhash_table + i;
2965 if (list_empty(head))
2967 list_for_each_entry_safe(class, next, head, hash_entry) {
2968 if (unlikely(class == lock->class_cache)) {
2969 if (debug_locks_off_graph_unlock())
2978 raw_local_irq_restore(flags);
2981 void lockdep_init(void)
2986 * Some architectures have their own start_kernel()
2987 * code which calls lockdep_init(), while we also
2988 * call lockdep_init() from the start_kernel() itself,
2989 * and we want to initialize the hashes only once:
2991 if (lockdep_initialized)
2994 for (i = 0; i < CLASSHASH_SIZE; i++)
2995 INIT_LIST_HEAD(classhash_table + i);
2997 for (i = 0; i < CHAINHASH_SIZE; i++)
2998 INIT_LIST_HEAD(chainhash_table + i);
3000 lockdep_initialized = 1;
3003 void __init lockdep_info(void)
3005 printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");
3007 printk("... MAX_LOCKDEP_SUBCLASSES: %lu\n", MAX_LOCKDEP_SUBCLASSES);
3008 printk("... MAX_LOCK_DEPTH: %lu\n", MAX_LOCK_DEPTH);
3009 printk("... MAX_LOCKDEP_KEYS: %lu\n", MAX_LOCKDEP_KEYS);
3010 printk("... CLASSHASH_SIZE: %lu\n", CLASSHASH_SIZE);
3011 printk("... MAX_LOCKDEP_ENTRIES: %lu\n", MAX_LOCKDEP_ENTRIES);
3012 printk("... MAX_LOCKDEP_CHAINS: %lu\n", MAX_LOCKDEP_CHAINS);
3013 printk("... CHAINHASH_SIZE: %lu\n", CHAINHASH_SIZE);
3015 printk(" memory used by lock dependency info: %lu kB\n",
3016 (sizeof(struct lock_class) * MAX_LOCKDEP_KEYS +
3017 sizeof(struct list_head) * CLASSHASH_SIZE +
3018 sizeof(struct lock_list) * MAX_LOCKDEP_ENTRIES +
3019 sizeof(struct lock_chain) * MAX_LOCKDEP_CHAINS +
3020 sizeof(struct list_head) * CHAINHASH_SIZE) / 1024);
3022 printk(" per task-struct memory footprint: %lu bytes\n",
3023 sizeof(struct held_lock) * MAX_LOCK_DEPTH);
3025 #ifdef CONFIG_DEBUG_LOCKDEP
3026 if (lockdep_init_error)
3027 printk("WARNING: lockdep init error! Arch code didnt call lockdep_init() early enough?\n");
3031 static inline int in_range(const void *start, const void *addr, const void *end)
3033 return addr >= start && addr <= end;
3037 print_freed_lock_bug(struct task_struct *curr, const void *mem_from,
3038 const void *mem_to, struct held_lock *hlock)
3040 if (!debug_locks_off())
3042 if (debug_locks_silent)
3045 printk("\n=========================\n");
3046 printk( "[ BUG: held lock freed! ]\n");
3047 printk( "-------------------------\n");
3048 printk("%s/%d is freeing memory %p-%p, with a lock still held there!\n",
3049 curr->comm, curr->pid, mem_from, mem_to-1);
3051 lockdep_print_held_locks(curr);
3053 printk("\nstack backtrace:\n");
3058 * Called when kernel memory is freed (or unmapped), or if a lock
3059 * is destroyed or reinitialized - this code checks whether there is
3060 * any held lock in the memory range of <from> to <to>:
3062 void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len)
3064 const void *mem_to = mem_from + mem_len, *lock_from, *lock_to;
3065 struct task_struct *curr = current;
3066 struct held_lock *hlock;
3067 unsigned long flags;
3070 if (unlikely(!debug_locks))
3073 local_irq_save(flags);
3074 for (i = 0; i < curr->lockdep_depth; i++) {
3075 hlock = curr->held_locks + i;
3077 lock_from = (void *)hlock->instance;
3078 lock_to = (void *)(hlock->instance + 1);
3080 if (!in_range(mem_from, lock_from, mem_to) &&
3081 !in_range(mem_from, lock_to, mem_to))
3084 print_freed_lock_bug(curr, mem_from, mem_to, hlock);
3087 local_irq_restore(flags);
3089 EXPORT_SYMBOL_GPL(debug_check_no_locks_freed);
3091 static void print_held_locks_bug(struct task_struct *curr)
3093 if (!debug_locks_off())
3095 if (debug_locks_silent)
3098 printk("\n=====================================\n");
3099 printk( "[ BUG: lock held at task exit time! ]\n");
3100 printk( "-------------------------------------\n");
3101 printk("%s/%d is exiting with locks still held!\n",
3102 curr->comm, curr->pid);
3103 lockdep_print_held_locks(curr);
3105 printk("\nstack backtrace:\n");
3109 void debug_check_no_locks_held(struct task_struct *task)
3111 if (unlikely(task->lockdep_depth > 0))
3112 print_held_locks_bug(task);
3115 void debug_show_all_locks(void)
3117 struct task_struct *g, *p;
3121 if (unlikely(!debug_locks)) {
3122 printk("INFO: lockdep is turned off.\n");
3125 printk("\nShowing all locks held in the system:\n");
3128 * Here we try to get the tasklist_lock as hard as possible,
3129 * if not successful after 2 seconds we ignore it (but keep
3130 * trying). This is to enable a debug printout even if a
3131 * tasklist_lock-holding task deadlocks or crashes.
3134 if (!read_trylock(&tasklist_lock)) {
3136 printk("hm, tasklist_lock locked, retrying... ");
3139 printk(" #%d", 10-count);
3143 printk(" ignoring it.\n");
3147 printk(" locked it.\n");
3149 do_each_thread(g, p) {
3150 if (p->lockdep_depth)
3151 lockdep_print_held_locks(p);
3153 if (read_trylock(&tasklist_lock))
3155 } while_each_thread(g, p);
3158 printk("=============================================\n\n");
3161 read_unlock(&tasklist_lock);
3164 EXPORT_SYMBOL_GPL(debug_show_all_locks);
3166 void debug_show_held_locks(struct task_struct *task)
3168 if (unlikely(!debug_locks)) {
3169 printk("INFO: lockdep is turned off.\n");
3172 lockdep_print_held_locks(task);
3175 EXPORT_SYMBOL_GPL(debug_show_held_locks);