1 /*
2 * kernel/lockdep.c
3 *
4 * Runtime locking correctness validator
5 *
6 * Started by Ingo Molnar:
7 *
8 * Copyright (C) 2006,2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
9 * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
10 *
11 * this code maps all the lock dependencies as they occur in a live kernel
12 * and will warn about the following classes of locking bugs:
13 *
14 * - lock inversion scenarios
15 * - circular lock dependencies
16 * - hardirq/softirq safe/unsafe locking bugs
17 *
18 * Bugs are reported even if the current locking scenario does not cause
19 * any deadlock at this point.
20 *
21 * I.e. if anytime in the past two locks were taken in a different order,
22 * even if it happened for another task, even if those were different
23 * locks (but of the same class as this lock), this code will detect it.
24 *
25 * Thanks to Arjan van de Ven for coming up with the initial idea of
26 * mapping lock dependencies runtime.
27 */
28 #define DISABLE_BRANCH_PROFILING
29 #include <linux/mutex.h>
30 #include <linux/sched.h>
31 #include <linux/delay.h>
32 #include <linux/module.h>
33 #include <linux/proc_fs.h>
34 #include <linux/seq_file.h>
35 #include <linux/spinlock.h>
36 #include <linux/kallsyms.h>
37 #include <linux/interrupt.h>
38 #include <linux/stacktrace.h>
39 #include <linux/debug_locks.h>
40 #include <linux/irqflags.h>
41 #include <linux/utsname.h>
42 #include <linux/hash.h>
43 #include <linux/ftrace.h>
44 #include <linux/stringify.h>
45 #include <linux/bitops.h>
46 #include <linux/gfp.h>
47 #include <linux/kmemcheck.h>
48
49 #include <asm/sections.h>
50
51 #include "lockdep_internals.h"
52
53 #define CREATE_TRACE_POINTS
54 #include <trace/events/lock.h>
55
56 #ifdef CONFIG_PROVE_LOCKING
57 int prove_locking = 1;
58 module_param(prove_locking, int, 0644);
59 #else
60 #define prove_locking 0
61 #endif
62
63 #ifdef CONFIG_LOCK_STAT
64 int lock_stat = 1;
65 module_param(lock_stat, int, 0644);
66 #else
67 #define lock_stat 0
68 #endif
69
70 /*
71 * lockdep_lock: protects the lockdep graph, the hashes and the
72 * class/list/hash allocators.
73 *
74 * This is one of the rare exceptions where it's justified
75 * to use a raw spinlock - we really dont want the spinlock
76 * code to recurse back into the lockdep code...
77 */
78 static arch_spinlock_t lockdep_lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
79
graph_lock(void)80 static int graph_lock(void)
81 {
82 arch_spin_lock(&lockdep_lock);
83 /*
84 * Make sure that if another CPU detected a bug while
85 * walking the graph we dont change it (while the other
86 * CPU is busy printing out stuff with the graph lock
87 * dropped already)
88 */
89 if (!debug_locks) {
90 arch_spin_unlock(&lockdep_lock);
91 return 0;
92 }
93 /* prevent any recursions within lockdep from causing deadlocks */
94 current->lockdep_recursion++;
95 return 1;
96 }
97
graph_unlock(void)98 static inline int graph_unlock(void)
99 {
100 if (debug_locks && !arch_spin_is_locked(&lockdep_lock)) {
101 /*
102 * The lockdep graph lock isn't locked while we expect it to
103 * be, we're confused now, bye!
104 */
105 return DEBUG_LOCKS_WARN_ON(1);
106 }
107
108 current->lockdep_recursion--;
109 arch_spin_unlock(&lockdep_lock);
110 return 0;
111 }
112
113 /*
114 * Turn lock debugging off and return with 0 if it was off already,
115 * and also release the graph lock:
116 */
debug_locks_off_graph_unlock(void)117 static inline int debug_locks_off_graph_unlock(void)
118 {
119 int ret = debug_locks_off();
120
121 arch_spin_unlock(&lockdep_lock);
122
123 return ret;
124 }
125
126 static int lockdep_initialized;
127
128 unsigned long nr_list_entries;
129 static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES];
130
131 /*
132 * All data structures here are protected by the global debug_lock.
133 *
134 * Mutex key structs only get allocated, once during bootup, and never
135 * get freed - this significantly simplifies the debugging code.
136 */
137 unsigned long nr_lock_classes;
138 static struct lock_class lock_classes[MAX_LOCKDEP_KEYS];
139
hlock_class(struct held_lock * hlock)140 static inline struct lock_class *hlock_class(struct held_lock *hlock)
141 {
142 if (!hlock->class_idx) {
143 /*
144 * Someone passed in garbage, we give up.
145 */
146 DEBUG_LOCKS_WARN_ON(1);
147 return NULL;
148 }
149 return lock_classes + hlock->class_idx - 1;
150 }
151
152 #ifdef CONFIG_LOCK_STAT
153 static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS],
154 cpu_lock_stats);
155
lockstat_clock(void)156 static inline u64 lockstat_clock(void)
157 {
158 return local_clock();
159 }
160
lock_point(unsigned long points[],unsigned long ip)161 static int lock_point(unsigned long points[], unsigned long ip)
162 {
163 int i;
164
165 for (i = 0; i < LOCKSTAT_POINTS; i++) {
166 if (points[i] == 0) {
167 points[i] = ip;
168 break;
169 }
170 if (points[i] == ip)
171 break;
172 }
173
174 return i;
175 }
176
lock_time_inc(struct lock_time * lt,u64 time)177 static void lock_time_inc(struct lock_time *lt, u64 time)
178 {
179 if (time > lt->max)
180 lt->max = time;
181
182 if (time < lt->min || !lt->nr)
183 lt->min = time;
184
185 lt->total += time;
186 lt->nr++;
187 }
188
lock_time_add(struct lock_time * src,struct lock_time * dst)189 static inline void lock_time_add(struct lock_time *src, struct lock_time *dst)
190 {
191 if (!src->nr)
192 return;
193
194 if (src->max > dst->max)
195 dst->max = src->max;
196
197 if (src->min < dst->min || !dst->nr)
198 dst->min = src->min;
199
200 dst->total += src->total;
201 dst->nr += src->nr;
202 }
203
lock_stats(struct lock_class * class)204 struct lock_class_stats lock_stats(struct lock_class *class)
205 {
206 struct lock_class_stats stats;
207 int cpu, i;
208
209 memset(&stats, 0, sizeof(struct lock_class_stats));
210 for_each_possible_cpu(cpu) {
211 struct lock_class_stats *pcs =
212 &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
213
214 for (i = 0; i < ARRAY_SIZE(stats.contention_point); i++)
215 stats.contention_point[i] += pcs->contention_point[i];
216
217 for (i = 0; i < ARRAY_SIZE(stats.contending_point); i++)
218 stats.contending_point[i] += pcs->contending_point[i];
219
220 lock_time_add(&pcs->read_waittime, &stats.read_waittime);
221 lock_time_add(&pcs->write_waittime, &stats.write_waittime);
222
223 lock_time_add(&pcs->read_holdtime, &stats.read_holdtime);
224 lock_time_add(&pcs->write_holdtime, &stats.write_holdtime);
225
226 for (i = 0; i < ARRAY_SIZE(stats.bounces); i++)
227 stats.bounces[i] += pcs->bounces[i];
228 }
229
230 return stats;
231 }
232
clear_lock_stats(struct lock_class * class)233 void clear_lock_stats(struct lock_class *class)
234 {
235 int cpu;
236
237 for_each_possible_cpu(cpu) {
238 struct lock_class_stats *cpu_stats =
239 &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
240
241 memset(cpu_stats, 0, sizeof(struct lock_class_stats));
242 }
243 memset(class->contention_point, 0, sizeof(class->contention_point));
244 memset(class->contending_point, 0, sizeof(class->contending_point));
245 }
246
get_lock_stats(struct lock_class * class)247 static struct lock_class_stats *get_lock_stats(struct lock_class *class)
248 {
249 return &get_cpu_var(cpu_lock_stats)[class - lock_classes];
250 }
251
put_lock_stats(struct lock_class_stats * stats)252 static void put_lock_stats(struct lock_class_stats *stats)
253 {
254 put_cpu_var(cpu_lock_stats);
255 }
256
lock_release_holdtime(struct held_lock * hlock)257 static void lock_release_holdtime(struct held_lock *hlock)
258 {
259 struct lock_class_stats *stats;
260 u64 holdtime;
261
262 if (!lock_stat)
263 return;
264
265 holdtime = lockstat_clock() - hlock->holdtime_stamp;
266
267 stats = get_lock_stats(hlock_class(hlock));
268 if (hlock->read)
269 lock_time_inc(&stats->read_holdtime, holdtime);
270 else
271 lock_time_inc(&stats->write_holdtime, holdtime);
272 put_lock_stats(stats);
273 }
274 #else
lock_release_holdtime(struct held_lock * hlock)275 static inline void lock_release_holdtime(struct held_lock *hlock)
276 {
277 }
278 #endif
279
280 /*
281 * We keep a global list of all lock classes. The list only grows,
282 * never shrinks. The list is only accessed with the lockdep
283 * spinlock lock held.
284 */
285 LIST_HEAD(all_lock_classes);
286
287 /*
288 * The lockdep classes are in a hash-table as well, for fast lookup:
289 */
290 #define CLASSHASH_BITS (MAX_LOCKDEP_KEYS_BITS - 1)
291 #define CLASSHASH_SIZE (1UL << CLASSHASH_BITS)
292 #define __classhashfn(key) hash_long((unsigned long)key, CLASSHASH_BITS)
293 #define classhashentry(key) (classhash_table + __classhashfn((key)))
294
295 static struct list_head classhash_table[CLASSHASH_SIZE];
296
297 /*
298 * We put the lock dependency chains into a hash-table as well, to cache
299 * their existence:
300 */
301 #define CHAINHASH_BITS (MAX_LOCKDEP_CHAINS_BITS-1)
302 #define CHAINHASH_SIZE (1UL << CHAINHASH_BITS)
303 #define __chainhashfn(chain) hash_long(chain, CHAINHASH_BITS)
304 #define chainhashentry(chain) (chainhash_table + __chainhashfn((chain)))
305
306 static struct list_head chainhash_table[CHAINHASH_SIZE];
307
308 /*
309 * The hash key of the lock dependency chains is a hash itself too:
310 * it's a hash of all locks taken up to that lock, including that lock.
311 * It's a 64-bit hash, because it's important for the keys to be
312 * unique.
313 */
314 #define iterate_chain_key(key1, key2) \
315 (((key1) << MAX_LOCKDEP_KEYS_BITS) ^ \
316 ((key1) >> (64-MAX_LOCKDEP_KEYS_BITS)) ^ \
317 (key2))
318
lockdep_off(void)319 void lockdep_off(void)
320 {
321 current->lockdep_recursion++;
322 }
323 EXPORT_SYMBOL(lockdep_off);
324
lockdep_on(void)325 void lockdep_on(void)
326 {
327 current->lockdep_recursion--;
328 }
329 EXPORT_SYMBOL(lockdep_on);
330
331 /*
332 * Debugging switches:
333 */
334
335 #define VERBOSE 0
336 #define VERY_VERBOSE 0
337
338 #if VERBOSE
339 # define HARDIRQ_VERBOSE 1
340 # define SOFTIRQ_VERBOSE 1
341 # define RECLAIM_VERBOSE 1
342 #else
343 # define HARDIRQ_VERBOSE 0
344 # define SOFTIRQ_VERBOSE 0
345 # define RECLAIM_VERBOSE 0
346 #endif
347
348 #if VERBOSE || HARDIRQ_VERBOSE || SOFTIRQ_VERBOSE || RECLAIM_VERBOSE
349 /*
350 * Quick filtering for interesting events:
351 */
class_filter(struct lock_class * class)352 static int class_filter(struct lock_class *class)
353 {
354 #if 0
355 /* Example */
356 if (class->name_version == 1 &&
357 !strcmp(class->name, "lockname"))
358 return 1;
359 if (class->name_version == 1 &&
360 !strcmp(class->name, "&struct->lockfield"))
361 return 1;
362 #endif
363 /* Filter everything else. 1 would be to allow everything else */
364 return 0;
365 }
366 #endif
367
verbose(struct lock_class * class)368 static int verbose(struct lock_class *class)
369 {
370 #if VERBOSE
371 return class_filter(class);
372 #endif
373 return 0;
374 }
375
376 /*
377 * Stack-trace: tightly packed array of stack backtrace
378 * addresses. Protected by the graph_lock.
379 */
380 unsigned long nr_stack_trace_entries;
381 static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];
382
print_lockdep_off(const char * bug_msg)383 static void print_lockdep_off(const char *bug_msg)
384 {
385 printk(KERN_DEBUG "%s\n", bug_msg);
386 printk(KERN_DEBUG "turning off the locking correctness validator.\n");
387 #ifdef CONFIG_LOCK_STAT
388 printk(KERN_DEBUG "Please attach the output of /proc/lock_stat to the bug report\n");
389 #endif
390 }
391
save_trace(struct stack_trace * trace)392 static int save_trace(struct stack_trace *trace)
393 {
394 trace->nr_entries = 0;
395 trace->max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries;
396 trace->entries = stack_trace + nr_stack_trace_entries;
397
398 trace->skip = 3;
399
400 save_stack_trace(trace);
401
402 /*
403 * Some daft arches put -1 at the end to indicate its a full trace.
404 *
405 * <rant> this is buggy anyway, since it takes a whole extra entry so a
406 * complete trace that maxes out the entries provided will be reported
407 * as incomplete, friggin useless </rant>
408 */
409 if (trace->nr_entries != 0 &&
410 trace->entries[trace->nr_entries-1] == ULONG_MAX)
411 trace->nr_entries--;
412
413 trace->max_entries = trace->nr_entries;
414
415 nr_stack_trace_entries += trace->nr_entries;
416
417 if (nr_stack_trace_entries >= MAX_STACK_TRACE_ENTRIES-1) {
418 if (!debug_locks_off_graph_unlock())
419 return 0;
420
421 print_lockdep_off("BUG: MAX_STACK_TRACE_ENTRIES too low!");
422 dump_stack();
423
424 return 0;
425 }
426
427 return 1;
428 }
429
430 unsigned int nr_hardirq_chains;
431 unsigned int nr_softirq_chains;
432 unsigned int nr_process_chains;
433 unsigned int max_lockdep_depth;
434
435 #ifdef CONFIG_DEBUG_LOCKDEP
436 /*
437 * We cannot printk in early bootup code. Not even early_printk()
438 * might work. So we mark any initialization errors and printk
439 * about it later on, in lockdep_info().
440 */
441 static int lockdep_init_error;
442 static const char *lock_init_error;
443 static unsigned long lockdep_init_trace_data[20];
444 static struct stack_trace lockdep_init_trace = {
445 .max_entries = ARRAY_SIZE(lockdep_init_trace_data),
446 .entries = lockdep_init_trace_data,
447 };
448
449 /*
450 * Various lockdep statistics:
451 */
452 DEFINE_PER_CPU(struct lockdep_stats, lockdep_stats);
453 #endif
454
455 /*
456 * Locking printouts:
457 */
458
459 #define __USAGE(__STATE) \
460 [LOCK_USED_IN_##__STATE] = "IN-"__stringify(__STATE)"-W", \
461 [LOCK_ENABLED_##__STATE] = __stringify(__STATE)"-ON-W", \
462 [LOCK_USED_IN_##__STATE##_READ] = "IN-"__stringify(__STATE)"-R",\
463 [LOCK_ENABLED_##__STATE##_READ] = __stringify(__STATE)"-ON-R",
464
465 static const char *usage_str[] =
466 {
467 #define LOCKDEP_STATE(__STATE) __USAGE(__STATE)
468 #include "lockdep_states.h"
469 #undef LOCKDEP_STATE
470 [LOCK_USED] = "INITIAL USE",
471 };
472
__get_key_name(struct lockdep_subclass_key * key,char * str)473 const char * __get_key_name(struct lockdep_subclass_key *key, char *str)
474 {
475 return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str);
476 }
477
lock_flag(enum lock_usage_bit bit)478 static inline unsigned long lock_flag(enum lock_usage_bit bit)
479 {
480 return 1UL << bit;
481 }
482
get_usage_char(struct lock_class * class,enum lock_usage_bit bit)483 static char get_usage_char(struct lock_class *class, enum lock_usage_bit bit)
484 {
485 char c = '.';
486
487 if (class->usage_mask & lock_flag(bit + 2))
488 c = '+';
489 if (class->usage_mask & lock_flag(bit)) {
490 c = '-';
491 if (class->usage_mask & lock_flag(bit + 2))
492 c = '?';
493 }
494
495 return c;
496 }
497
get_usage_chars(struct lock_class * class,char usage[LOCK_USAGE_CHARS])498 void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS])
499 {
500 int i = 0;
501
502 #define LOCKDEP_STATE(__STATE) \
503 usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE); \
504 usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE##_READ);
505 #include "lockdep_states.h"
506 #undef LOCKDEP_STATE
507
508 usage[i] = '\0';
509 }
510
__print_lock_name(struct lock_class * class)511 static void __print_lock_name(struct lock_class *class)
512 {
513 char str[KSYM_NAME_LEN];
514 const char *name;
515
516 name = class->name;
517 if (!name) {
518 name = __get_key_name(class->key, str);
519 printk("%s", name);
520 } else {
521 printk("%s", name);
522 if (class->name_version > 1)
523 printk("#%d", class->name_version);
524 if (class->subclass)
525 printk("/%d", class->subclass);
526 }
527 }
528
print_lock_name(struct lock_class * class)529 static void print_lock_name(struct lock_class *class)
530 {
531 char usage[LOCK_USAGE_CHARS];
532
533 get_usage_chars(class, usage);
534
535 printk(" (");
536 __print_lock_name(class);
537 printk("){%s}", usage);
538 }
539
print_lockdep_cache(struct lockdep_map * lock)540 static void print_lockdep_cache(struct lockdep_map *lock)
541 {
542 const char *name;
543 char str[KSYM_NAME_LEN];
544
545 name = lock->name;
546 if (!name)
547 name = __get_key_name(lock->key->subkeys, str);
548
549 printk("%s", name);
550 }
551
print_lock(struct held_lock * hlock)552 static void print_lock(struct held_lock *hlock)
553 {
554 /*
555 * We can be called locklessly through debug_show_all_locks() so be
556 * extra careful, the hlock might have been released and cleared.
557 */
558 unsigned int class_idx = hlock->class_idx;
559
560 /* Don't re-read hlock->class_idx, can't use READ_ONCE() on bitfields: */
561 barrier();
562
563 if (!class_idx || (class_idx - 1) >= MAX_LOCKDEP_KEYS) {
564 printk("<RELEASED>\n");
565 return;
566 }
567
568 print_lock_name(lock_classes + class_idx - 1);
569 printk(", at: ");
570 print_ip_sym(hlock->acquire_ip);
571 }
572
lockdep_print_held_locks(struct task_struct * curr)573 static void lockdep_print_held_locks(struct task_struct *curr)
574 {
575 int i, depth = curr->lockdep_depth;
576
577 if (!depth) {
578 printk("no locks held by %s/%d.\n", curr->comm, task_pid_nr(curr));
579 return;
580 }
581 printk("%d lock%s held by %s/%d:\n",
582 depth, depth > 1 ? "s" : "", curr->comm, task_pid_nr(curr));
583
584 for (i = 0; i < depth; i++) {
585 printk(" #%d: ", i);
586 print_lock(curr->held_locks + i);
587 }
588 }
589
print_kernel_ident(void)590 static void print_kernel_ident(void)
591 {
592 printk("%s %.*s %s\n", init_utsname()->release,
593 (int)strcspn(init_utsname()->version, " "),
594 init_utsname()->version,
595 print_tainted());
596 }
597
very_verbose(struct lock_class * class)598 static int very_verbose(struct lock_class *class)
599 {
600 #if VERY_VERBOSE
601 return class_filter(class);
602 #endif
603 return 0;
604 }
605
606 /*
607 * Is this the address of a static object:
608 */
609 #ifdef __KERNEL__
static_obj(void * obj)610 static int static_obj(void *obj)
611 {
612 unsigned long start = (unsigned long) &_stext,
613 end = (unsigned long) &_end,
614 addr = (unsigned long) obj;
615
616 /*
617 * static variable?
618 */
619 if ((addr >= start) && (addr < end))
620 return 1;
621
622 if (arch_is_kernel_data(addr))
623 return 1;
624
625 /*
626 * in-kernel percpu var?
627 */
628 if (is_kernel_percpu_address(addr))
629 return 1;
630
631 /*
632 * module static or percpu var?
633 */
634 return is_module_address(addr) || is_module_percpu_address(addr);
635 }
636 #endif
637
638 /*
639 * To make lock name printouts unique, we calculate a unique
640 * class->name_version generation counter:
641 */
count_matching_names(struct lock_class * new_class)642 static int count_matching_names(struct lock_class *new_class)
643 {
644 struct lock_class *class;
645 int count = 0;
646
647 if (!new_class->name)
648 return 0;
649
650 list_for_each_entry_rcu(class, &all_lock_classes, lock_entry) {
651 if (new_class->key - new_class->subclass == class->key)
652 return class->name_version;
653 if (class->name && !strcmp(class->name, new_class->name))
654 count = max(count, class->name_version);
655 }
656
657 return count + 1;
658 }
659
660 /*
661 * Register a lock's class in the hash-table, if the class is not present
662 * yet. Otherwise we look it up. We cache the result in the lock object
663 * itself, so actual lookup of the hash should be once per lock object.
664 */
665 static inline struct lock_class *
look_up_lock_class(struct lockdep_map * lock,unsigned int subclass)666 look_up_lock_class(struct lockdep_map *lock, unsigned int subclass)
667 {
668 struct lockdep_subclass_key *key;
669 struct list_head *hash_head;
670 struct lock_class *class;
671
672 #ifdef CONFIG_DEBUG_LOCKDEP
673 /*
674 * If the architecture calls into lockdep before initializing
675 * the hashes then we'll warn about it later. (we cannot printk
676 * right now)
677 */
678 if (unlikely(!lockdep_initialized)) {
679 lockdep_init();
680 lockdep_init_error = 1;
681 lock_init_error = lock->name;
682 save_stack_trace(&lockdep_init_trace);
683 }
684 #endif
685
686 if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
687 debug_locks_off();
688 printk(KERN_ERR
689 "BUG: looking up invalid subclass: %u\n", subclass);
690 printk(KERN_ERR
691 "turning off the locking correctness validator.\n");
692 dump_stack();
693 return NULL;
694 }
695
696 /*
697 * Static locks do not have their class-keys yet - for them the key
698 * is the lock object itself:
699 */
700 if (unlikely(!lock->key))
701 lock->key = (void *)lock;
702
703 /*
704 * NOTE: the class-key must be unique. For dynamic locks, a static
705 * lock_class_key variable is passed in through the mutex_init()
706 * (or spin_lock_init()) call - which acts as the key. For static
707 * locks we use the lock object itself as the key.
708 */
709 BUILD_BUG_ON(sizeof(struct lock_class_key) >
710 sizeof(struct lockdep_map));
711
712 key = lock->key->subkeys + subclass;
713
714 hash_head = classhashentry(key);
715
716 /*
717 * We do an RCU walk of the hash, see lockdep_free_key_range().
718 */
719 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
720 return NULL;
721
722 list_for_each_entry_rcu(class, hash_head, hash_entry) {
723 if (class->key == key) {
724 /*
725 * Huh! same key, different name? Did someone trample
726 * on some memory? We're most confused.
727 */
728 WARN_ON_ONCE(class->name != lock->name);
729 return class;
730 }
731 }
732
733 return NULL;
734 }
735
736 /*
737 * Register a lock's class in the hash-table, if the class is not present
738 * yet. Otherwise we look it up. We cache the result in the lock object
739 * itself, so actual lookup of the hash should be once per lock object.
740 */
741 static inline struct lock_class *
register_lock_class(struct lockdep_map * lock,unsigned int subclass,int force)742 register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
743 {
744 struct lockdep_subclass_key *key;
745 struct list_head *hash_head;
746 struct lock_class *class;
747
748 DEBUG_LOCKS_WARN_ON(!irqs_disabled());
749
750 class = look_up_lock_class(lock, subclass);
751 if (likely(class))
752 goto out_set_class_cache;
753
754 /*
755 * Debug-check: all keys must be persistent!
756 */
757 if (!static_obj(lock->key)) {
758 debug_locks_off();
759 printk("INFO: trying to register non-static key.\n");
760 printk("the code is fine but needs lockdep annotation.\n");
761 printk("turning off the locking correctness validator.\n");
762 dump_stack();
763
764 return NULL;
765 }
766
767 key = lock->key->subkeys + subclass;
768 hash_head = classhashentry(key);
769
770 if (!graph_lock()) {
771 return NULL;
772 }
773 /*
774 * We have to do the hash-walk again, to avoid races
775 * with another CPU:
776 */
777 list_for_each_entry_rcu(class, hash_head, hash_entry) {
778 if (class->key == key)
779 goto out_unlock_set;
780 }
781
782 /*
783 * Allocate a new key from the static array, and add it to
784 * the hash:
785 */
786 if (nr_lock_classes >= MAX_LOCKDEP_KEYS) {
787 if (!debug_locks_off_graph_unlock()) {
788 return NULL;
789 }
790
791 print_lockdep_off("BUG: MAX_LOCKDEP_KEYS too low!");
792 dump_stack();
793 return NULL;
794 }
795 class = lock_classes + nr_lock_classes++;
796 debug_atomic_inc(nr_unused_locks);
797 class->key = key;
798 class->name = lock->name;
799 class->subclass = subclass;
800 INIT_LIST_HEAD(&class->lock_entry);
801 INIT_LIST_HEAD(&class->locks_before);
802 INIT_LIST_HEAD(&class->locks_after);
803 class->name_version = count_matching_names(class);
804 /*
805 * We use RCU's safe list-add method to make
806 * parallel walking of the hash-list safe:
807 */
808 list_add_tail_rcu(&class->hash_entry, hash_head);
809 /*
810 * Add it to the global list of classes:
811 */
812 list_add_tail_rcu(&class->lock_entry, &all_lock_classes);
813
814 if (verbose(class)) {
815 graph_unlock();
816
817 printk("\nnew class %p: %s", class->key, class->name);
818 if (class->name_version > 1)
819 printk("#%d", class->name_version);
820 printk("\n");
821 dump_stack();
822
823 if (!graph_lock()) {
824 return NULL;
825 }
826 }
827 out_unlock_set:
828 graph_unlock();
829
830 out_set_class_cache:
831 if (!subclass || force)
832 lock->class_cache[0] = class;
833 else if (subclass < NR_LOCKDEP_CACHING_CLASSES)
834 lock->class_cache[subclass] = class;
835
836 /*
837 * Hash collision, did we smoke some? We found a class with a matching
838 * hash but the subclass -- which is hashed in -- didn't match.
839 */
840 if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))
841 return NULL;
842
843 return class;
844 }
845
846 #ifdef CONFIG_PROVE_LOCKING
847 /*
848 * Allocate a lockdep entry. (assumes the graph_lock held, returns
849 * with NULL on failure)
850 */
alloc_list_entry(void)851 static struct lock_list *alloc_list_entry(void)
852 {
853 if (nr_list_entries >= MAX_LOCKDEP_ENTRIES) {
854 if (!debug_locks_off_graph_unlock())
855 return NULL;
856
857 print_lockdep_off("BUG: MAX_LOCKDEP_ENTRIES too low!");
858 dump_stack();
859 return NULL;
860 }
861 return list_entries + nr_list_entries++;
862 }
863
864 /*
865 * Add a new dependency to the head of the list:
866 */
add_lock_to_list(struct lock_class * class,struct lock_class * this,struct list_head * head,unsigned long ip,int distance,struct stack_trace * trace)867 static int add_lock_to_list(struct lock_class *class, struct lock_class *this,
868 struct list_head *head, unsigned long ip,
869 int distance, struct stack_trace *trace)
870 {
871 struct lock_list *entry;
872 /*
873 * Lock not present yet - get a new dependency struct and
874 * add it to the list:
875 */
876 entry = alloc_list_entry();
877 if (!entry)
878 return 0;
879
880 entry->class = this;
881 entry->distance = distance;
882 entry->trace = *trace;
883 /*
884 * Both allocation and removal are done under the graph lock; but
885 * iteration is under RCU-sched; see look_up_lock_class() and
886 * lockdep_free_key_range().
887 */
888 list_add_tail_rcu(&entry->entry, head);
889
890 return 1;
891 }
892
893 /*
894 * For good efficiency of modular, we use power of 2
895 */
896 #define MAX_CIRCULAR_QUEUE_SIZE 4096UL
897 #define CQ_MASK (MAX_CIRCULAR_QUEUE_SIZE-1)
898
899 /*
900 * The circular_queue and helpers is used to implement the
901 * breadth-first search(BFS)algorithem, by which we can build
902 * the shortest path from the next lock to be acquired to the
903 * previous held lock if there is a circular between them.
904 */
905 struct circular_queue {
906 unsigned long element[MAX_CIRCULAR_QUEUE_SIZE];
907 unsigned int front, rear;
908 };
909
910 static struct circular_queue lock_cq;
911
912 unsigned int max_bfs_queue_depth;
913
914 static unsigned int lockdep_dependency_gen_id;
915
__cq_init(struct circular_queue * cq)916 static inline void __cq_init(struct circular_queue *cq)
917 {
918 cq->front = cq->rear = 0;
919 lockdep_dependency_gen_id++;
920 }
921
__cq_empty(struct circular_queue * cq)922 static inline int __cq_empty(struct circular_queue *cq)
923 {
924 return (cq->front == cq->rear);
925 }
926
__cq_full(struct circular_queue * cq)927 static inline int __cq_full(struct circular_queue *cq)
928 {
929 return ((cq->rear + 1) & CQ_MASK) == cq->front;
930 }
931
__cq_enqueue(struct circular_queue * cq,unsigned long elem)932 static inline int __cq_enqueue(struct circular_queue *cq, unsigned long elem)
933 {
934 if (__cq_full(cq))
935 return -1;
936
937 cq->element[cq->rear] = elem;
938 cq->rear = (cq->rear + 1) & CQ_MASK;
939 return 0;
940 }
941
__cq_dequeue(struct circular_queue * cq,unsigned long * elem)942 static inline int __cq_dequeue(struct circular_queue *cq, unsigned long *elem)
943 {
944 if (__cq_empty(cq))
945 return -1;
946
947 *elem = cq->element[cq->front];
948 cq->front = (cq->front + 1) & CQ_MASK;
949 return 0;
950 }
951
__cq_get_elem_count(struct circular_queue * cq)952 static inline unsigned int __cq_get_elem_count(struct circular_queue *cq)
953 {
954 return (cq->rear - cq->front) & CQ_MASK;
955 }
956
mark_lock_accessed(struct lock_list * lock,struct lock_list * parent)957 static inline void mark_lock_accessed(struct lock_list *lock,
958 struct lock_list *parent)
959 {
960 unsigned long nr;
961
962 nr = lock - list_entries;
963 WARN_ON(nr >= nr_list_entries); /* Out-of-bounds, input fail */
964 lock->parent = parent;
965 lock->class->dep_gen_id = lockdep_dependency_gen_id;
966 }
967
lock_accessed(struct lock_list * lock)968 static inline unsigned long lock_accessed(struct lock_list *lock)
969 {
970 unsigned long nr;
971
972 nr = lock - list_entries;
973 WARN_ON(nr >= nr_list_entries); /* Out-of-bounds, input fail */
974 return lock->class->dep_gen_id == lockdep_dependency_gen_id;
975 }
976
get_lock_parent(struct lock_list * child)977 static inline struct lock_list *get_lock_parent(struct lock_list *child)
978 {
979 return child->parent;
980 }
981
get_lock_depth(struct lock_list * child)982 static inline int get_lock_depth(struct lock_list *child)
983 {
984 int depth = 0;
985 struct lock_list *parent;
986
987 while ((parent = get_lock_parent(child))) {
988 child = parent;
989 depth++;
990 }
991 return depth;
992 }
993
__bfs(struct lock_list * source_entry,void * data,int (* match)(struct lock_list * entry,void * data),struct lock_list ** target_entry,int forward)994 static int __bfs(struct lock_list *source_entry,
995 void *data,
996 int (*match)(struct lock_list *entry, void *data),
997 struct lock_list **target_entry,
998 int forward)
999 {
1000 struct lock_list *entry;
1001 struct list_head *head;
1002 struct circular_queue *cq = &lock_cq;
1003 int ret = 1;
1004
1005 if (match(source_entry, data)) {
1006 *target_entry = source_entry;
1007 ret = 0;
1008 goto exit;
1009 }
1010
1011 if (forward)
1012 head = &source_entry->class->locks_after;
1013 else
1014 head = &source_entry->class->locks_before;
1015
1016 if (list_empty(head))
1017 goto exit;
1018
1019 __cq_init(cq);
1020 __cq_enqueue(cq, (unsigned long)source_entry);
1021
1022 while (!__cq_empty(cq)) {
1023 struct lock_list *lock;
1024
1025 __cq_dequeue(cq, (unsigned long *)&lock);
1026
1027 if (!lock->class) {
1028 ret = -2;
1029 goto exit;
1030 }
1031
1032 if (forward)
1033 head = &lock->class->locks_after;
1034 else
1035 head = &lock->class->locks_before;
1036
1037 DEBUG_LOCKS_WARN_ON(!irqs_disabled());
1038
1039 list_for_each_entry_rcu(entry, head, entry) {
1040 if (!lock_accessed(entry)) {
1041 unsigned int cq_depth;
1042 mark_lock_accessed(entry, lock);
1043 if (match(entry, data)) {
1044 *target_entry = entry;
1045 ret = 0;
1046 goto exit;
1047 }
1048
1049 if (__cq_enqueue(cq, (unsigned long)entry)) {
1050 ret = -1;
1051 goto exit;
1052 }
1053 cq_depth = __cq_get_elem_count(cq);
1054 if (max_bfs_queue_depth < cq_depth)
1055 max_bfs_queue_depth = cq_depth;
1056 }
1057 }
1058 }
1059 exit:
1060 return ret;
1061 }
1062
__bfs_forwards(struct lock_list * src_entry,void * data,int (* match)(struct lock_list * entry,void * data),struct lock_list ** target_entry)1063 static inline int __bfs_forwards(struct lock_list *src_entry,
1064 void *data,
1065 int (*match)(struct lock_list *entry, void *data),
1066 struct lock_list **target_entry)
1067 {
1068 return __bfs(src_entry, data, match, target_entry, 1);
1069
1070 }
1071
__bfs_backwards(struct lock_list * src_entry,void * data,int (* match)(struct lock_list * entry,void * data),struct lock_list ** target_entry)1072 static inline int __bfs_backwards(struct lock_list *src_entry,
1073 void *data,
1074 int (*match)(struct lock_list *entry, void *data),
1075 struct lock_list **target_entry)
1076 {
1077 return __bfs(src_entry, data, match, target_entry, 0);
1078
1079 }
1080
1081 /*
1082 * Recursive, forwards-direction lock-dependency checking, used for
1083 * both noncyclic checking and for hardirq-unsafe/softirq-unsafe
1084 * checking.
1085 */
1086
1087 /*
1088 * Print a dependency chain entry (this is only done when a deadlock
1089 * has been detected):
1090 */
1091 static noinline int
print_circular_bug_entry(struct lock_list * target,int depth)1092 print_circular_bug_entry(struct lock_list *target, int depth)
1093 {
1094 if (debug_locks_silent)
1095 return 0;
1096 printk("\n-> #%u", depth);
1097 print_lock_name(target->class);
1098 printk(":\n");
1099 print_stack_trace(&target->trace, 6);
1100
1101 return 0;
1102 }
1103
1104 static void
print_circular_lock_scenario(struct held_lock * src,struct held_lock * tgt,struct lock_list * prt)1105 print_circular_lock_scenario(struct held_lock *src,
1106 struct held_lock *tgt,
1107 struct lock_list *prt)
1108 {
1109 struct lock_class *source = hlock_class(src);
1110 struct lock_class *target = hlock_class(tgt);
1111 struct lock_class *parent = prt->class;
1112
1113 /*
1114 * A direct locking problem where unsafe_class lock is taken
1115 * directly by safe_class lock, then all we need to show
1116 * is the deadlock scenario, as it is obvious that the
1117 * unsafe lock is taken under the safe lock.
1118 *
1119 * But if there is a chain instead, where the safe lock takes
1120 * an intermediate lock (middle_class) where this lock is
1121 * not the same as the safe lock, then the lock chain is
1122 * used to describe the problem. Otherwise we would need
1123 * to show a different CPU case for each link in the chain
1124 * from the safe_class lock to the unsafe_class lock.
1125 */
1126 if (parent != source) {
1127 printk("Chain exists of:\n ");
1128 __print_lock_name(source);
1129 printk(" --> ");
1130 __print_lock_name(parent);
1131 printk(" --> ");
1132 __print_lock_name(target);
1133 printk("\n\n");
1134 }
1135
1136 printk(" Possible unsafe locking scenario:\n\n");
1137 printk(" CPU0 CPU1\n");
1138 printk(" ---- ----\n");
1139 printk(" lock(");
1140 __print_lock_name(target);
1141 printk(");\n");
1142 printk(" lock(");
1143 __print_lock_name(parent);
1144 printk(");\n");
1145 printk(" lock(");
1146 __print_lock_name(target);
1147 printk(");\n");
1148 printk(" lock(");
1149 __print_lock_name(source);
1150 printk(");\n");
1151 printk("\n *** DEADLOCK ***\n\n");
1152 }
1153
1154 /*
1155 * When a circular dependency is detected, print the
1156 * header first:
1157 */
1158 static noinline int
print_circular_bug_header(struct lock_list * entry,unsigned int depth,struct held_lock * check_src,struct held_lock * check_tgt)1159 print_circular_bug_header(struct lock_list *entry, unsigned int depth,
1160 struct held_lock *check_src,
1161 struct held_lock *check_tgt)
1162 {
1163 struct task_struct *curr = current;
1164
1165 if (debug_locks_silent)
1166 return 0;
1167
1168 printk("\n");
1169 printk("======================================================\n");
1170 printk("[ INFO: possible circular locking dependency detected ]\n");
1171 print_kernel_ident();
1172 printk("-------------------------------------------------------\n");
1173 printk("%s/%d is trying to acquire lock:\n",
1174 curr->comm, task_pid_nr(curr));
1175 print_lock(check_src);
1176 printk("\nbut task is already holding lock:\n");
1177 print_lock(check_tgt);
1178 printk("\nwhich lock already depends on the new lock.\n\n");
1179 printk("\nthe existing dependency chain (in reverse order) is:\n");
1180
1181 print_circular_bug_entry(entry, depth);
1182
1183 return 0;
1184 }
1185
class_equal(struct lock_list * entry,void * data)1186 static inline int class_equal(struct lock_list *entry, void *data)
1187 {
1188 return entry->class == data;
1189 }
1190
print_circular_bug(struct lock_list * this,struct lock_list * target,struct held_lock * check_src,struct held_lock * check_tgt)1191 static noinline int print_circular_bug(struct lock_list *this,
1192 struct lock_list *target,
1193 struct held_lock *check_src,
1194 struct held_lock *check_tgt)
1195 {
1196 struct task_struct *curr = current;
1197 struct lock_list *parent;
1198 struct lock_list *first_parent;
1199 int depth;
1200
1201 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1202 return 0;
1203
1204 if (!save_trace(&this->trace))
1205 return 0;
1206
1207 depth = get_lock_depth(target);
1208
1209 print_circular_bug_header(target, depth, check_src, check_tgt);
1210
1211 parent = get_lock_parent(target);
1212 first_parent = parent;
1213
1214 while (parent) {
1215 print_circular_bug_entry(parent, --depth);
1216 parent = get_lock_parent(parent);
1217 }
1218
1219 printk("\nother info that might help us debug this:\n\n");
1220 print_circular_lock_scenario(check_src, check_tgt,
1221 first_parent);
1222
1223 lockdep_print_held_locks(curr);
1224
1225 printk("\nstack backtrace:\n");
1226 dump_stack();
1227
1228 return 0;
1229 }
1230
print_bfs_bug(int ret)1231 static noinline int print_bfs_bug(int ret)
1232 {
1233 if (!debug_locks_off_graph_unlock())
1234 return 0;
1235
1236 /*
1237 * Breadth-first-search failed, graph got corrupted?
1238 */
1239 WARN(1, "lockdep bfs error:%d\n", ret);
1240
1241 return 0;
1242 }
1243
noop_count(struct lock_list * entry,void * data)1244 static int noop_count(struct lock_list *entry, void *data)
1245 {
1246 (*(unsigned long *)data)++;
1247 return 0;
1248 }
1249
__lockdep_count_forward_deps(struct lock_list * this)1250 static unsigned long __lockdep_count_forward_deps(struct lock_list *this)
1251 {
1252 unsigned long count = 0;
1253 struct lock_list *uninitialized_var(target_entry);
1254
1255 __bfs_forwards(this, (void *)&count, noop_count, &target_entry);
1256
1257 return count;
1258 }
lockdep_count_forward_deps(struct lock_class * class)1259 unsigned long lockdep_count_forward_deps(struct lock_class *class)
1260 {
1261 unsigned long ret, flags;
1262 struct lock_list this;
1263
1264 this.parent = NULL;
1265 this.class = class;
1266
1267 raw_local_irq_save(flags);
1268 current->lockdep_recursion = 1;
1269 arch_spin_lock(&lockdep_lock);
1270 ret = __lockdep_count_forward_deps(&this);
1271 arch_spin_unlock(&lockdep_lock);
1272 current->lockdep_recursion = 0;
1273 raw_local_irq_restore(flags);
1274
1275 return ret;
1276 }
1277
__lockdep_count_backward_deps(struct lock_list * this)1278 static unsigned long __lockdep_count_backward_deps(struct lock_list *this)
1279 {
1280 unsigned long count = 0;
1281 struct lock_list *uninitialized_var(target_entry);
1282
1283 __bfs_backwards(this, (void *)&count, noop_count, &target_entry);
1284
1285 return count;
1286 }
1287
lockdep_count_backward_deps(struct lock_class * class)1288 unsigned long lockdep_count_backward_deps(struct lock_class *class)
1289 {
1290 unsigned long ret, flags;
1291 struct lock_list this;
1292
1293 this.parent = NULL;
1294 this.class = class;
1295
1296 raw_local_irq_save(flags);
1297 current->lockdep_recursion = 1;
1298 arch_spin_lock(&lockdep_lock);
1299 ret = __lockdep_count_backward_deps(&this);
1300 arch_spin_unlock(&lockdep_lock);
1301 current->lockdep_recursion = 0;
1302 raw_local_irq_restore(flags);
1303
1304 return ret;
1305 }
1306
1307 /*
1308 * Prove that the dependency graph starting at <entry> can not
1309 * lead to <target>. Print an error and return 0 if it does.
1310 */
1311 static noinline int
check_noncircular(struct lock_list * root,struct lock_class * target,struct lock_list ** target_entry)1312 check_noncircular(struct lock_list *root, struct lock_class *target,
1313 struct lock_list **target_entry)
1314 {
1315 int result;
1316
1317 debug_atomic_inc(nr_cyclic_checks);
1318
1319 result = __bfs_forwards(root, target, class_equal, target_entry);
1320
1321 return result;
1322 }
1323
1324 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
1325 /*
1326 * Forwards and backwards subgraph searching, for the purposes of
1327 * proving that two subgraphs can be connected by a new dependency
1328 * without creating any illegal irq-safe -> irq-unsafe lock dependency.
1329 */
1330
usage_match(struct lock_list * entry,void * bit)1331 static inline int usage_match(struct lock_list *entry, void *bit)
1332 {
1333 return entry->class->usage_mask & (1 << (enum lock_usage_bit)bit);
1334 }
1335
1336
1337
1338 /*
1339 * Find a node in the forwards-direction dependency sub-graph starting
1340 * at @root->class that matches @bit.
1341 *
1342 * Return 0 if such a node exists in the subgraph, and put that node
1343 * into *@target_entry.
1344 *
1345 * Return 1 otherwise and keep *@target_entry unchanged.
1346 * Return <0 on error.
1347 */
1348 static int
find_usage_forwards(struct lock_list * root,enum lock_usage_bit bit,struct lock_list ** target_entry)1349 find_usage_forwards(struct lock_list *root, enum lock_usage_bit bit,
1350 struct lock_list **target_entry)
1351 {
1352 int result;
1353
1354 debug_atomic_inc(nr_find_usage_forwards_checks);
1355
1356 result = __bfs_forwards(root, (void *)bit, usage_match, target_entry);
1357
1358 return result;
1359 }
1360
1361 /*
1362 * Find a node in the backwards-direction dependency sub-graph starting
1363 * at @root->class that matches @bit.
1364 *
1365 * Return 0 if such a node exists in the subgraph, and put that node
1366 * into *@target_entry.
1367 *
1368 * Return 1 otherwise and keep *@target_entry unchanged.
1369 * Return <0 on error.
1370 */
1371 static int
find_usage_backwards(struct lock_list * root,enum lock_usage_bit bit,struct lock_list ** target_entry)1372 find_usage_backwards(struct lock_list *root, enum lock_usage_bit bit,
1373 struct lock_list **target_entry)
1374 {
1375 int result;
1376
1377 debug_atomic_inc(nr_find_usage_backwards_checks);
1378
1379 result = __bfs_backwards(root, (void *)bit, usage_match, target_entry);
1380
1381 return result;
1382 }
1383
print_lock_class_header(struct lock_class * class,int depth)1384 static void print_lock_class_header(struct lock_class *class, int depth)
1385 {
1386 int bit;
1387
1388 printk("%*s->", depth, "");
1389 print_lock_name(class);
1390 printk(" ops: %lu", class->ops);
1391 printk(" {\n");
1392
1393 for (bit = 0; bit < LOCK_USAGE_STATES; bit++) {
1394 if (class->usage_mask & (1 << bit)) {
1395 int len = depth;
1396
1397 len += printk("%*s %s", depth, "", usage_str[bit]);
1398 len += printk(" at:\n");
1399 print_stack_trace(class->usage_traces + bit, len);
1400 }
1401 }
1402 printk("%*s }\n", depth, "");
1403
1404 printk("%*s ... key at: ",depth,"");
1405 print_ip_sym((unsigned long)class->key);
1406 }
1407
1408 /*
1409 * printk the shortest lock dependencies from @start to @end in reverse order:
1410 */
1411 static void __used
print_shortest_lock_dependencies(struct lock_list * leaf,struct lock_list * root)1412 print_shortest_lock_dependencies(struct lock_list *leaf,
1413 struct lock_list *root)
1414 {
1415 struct lock_list *entry = leaf;
1416 int depth;
1417
1418 /*compute depth from generated tree by BFS*/
1419 depth = get_lock_depth(leaf);
1420
1421 do {
1422 print_lock_class_header(entry->class, depth);
1423 printk("%*s ... acquired at:\n", depth, "");
1424 print_stack_trace(&entry->trace, 2);
1425 printk("\n");
1426
1427 if (depth == 0 && (entry != root)) {
1428 printk("lockdep:%s bad path found in chain graph\n", __func__);
1429 break;
1430 }
1431
1432 entry = get_lock_parent(entry);
1433 depth--;
1434 } while (entry && (depth >= 0));
1435
1436 return;
1437 }
1438
1439 static void
print_irq_lock_scenario(struct lock_list * safe_entry,struct lock_list * unsafe_entry,struct lock_class * prev_class,struct lock_class * next_class)1440 print_irq_lock_scenario(struct lock_list *safe_entry,
1441 struct lock_list *unsafe_entry,
1442 struct lock_class *prev_class,
1443 struct lock_class *next_class)
1444 {
1445 struct lock_class *safe_class = safe_entry->class;
1446 struct lock_class *unsafe_class = unsafe_entry->class;
1447 struct lock_class *middle_class = prev_class;
1448
1449 if (middle_class == safe_class)
1450 middle_class = next_class;
1451
1452 /*
1453 * A direct locking problem where unsafe_class lock is taken
1454 * directly by safe_class lock, then all we need to show
1455 * is the deadlock scenario, as it is obvious that the
1456 * unsafe lock is taken under the safe lock.
1457 *
1458 * But if there is a chain instead, where the safe lock takes
1459 * an intermediate lock (middle_class) where this lock is
1460 * not the same as the safe lock, then the lock chain is
1461 * used to describe the problem. Otherwise we would need
1462 * to show a different CPU case for each link in the chain
1463 * from the safe_class lock to the unsafe_class lock.
1464 */
1465 if (middle_class != unsafe_class) {
1466 printk("Chain exists of:\n ");
1467 __print_lock_name(safe_class);
1468 printk(" --> ");
1469 __print_lock_name(middle_class);
1470 printk(" --> ");
1471 __print_lock_name(unsafe_class);
1472 printk("\n\n");
1473 }
1474
1475 printk(" Possible interrupt unsafe locking scenario:\n\n");
1476 printk(" CPU0 CPU1\n");
1477 printk(" ---- ----\n");
1478 printk(" lock(");
1479 __print_lock_name(unsafe_class);
1480 printk(");\n");
1481 printk(" local_irq_disable();\n");
1482 printk(" lock(");
1483 __print_lock_name(safe_class);
1484 printk(");\n");
1485 printk(" lock(");
1486 __print_lock_name(middle_class);
1487 printk(");\n");
1488 printk(" <Interrupt>\n");
1489 printk(" lock(");
1490 __print_lock_name(safe_class);
1491 printk(");\n");
1492 printk("\n *** DEADLOCK ***\n\n");
1493 }
1494
1495 static int
print_bad_irq_dependency(struct task_struct * curr,struct lock_list * prev_root,struct lock_list * next_root,struct lock_list * backwards_entry,struct lock_list * forwards_entry,struct held_lock * prev,struct held_lock * next,enum lock_usage_bit bit1,enum lock_usage_bit bit2,const char * irqclass)1496 print_bad_irq_dependency(struct task_struct *curr,
1497 struct lock_list *prev_root,
1498 struct lock_list *next_root,
1499 struct lock_list *backwards_entry,
1500 struct lock_list *forwards_entry,
1501 struct held_lock *prev,
1502 struct held_lock *next,
1503 enum lock_usage_bit bit1,
1504 enum lock_usage_bit bit2,
1505 const char *irqclass)
1506 {
1507 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1508 return 0;
1509
1510 printk("\n");
1511 printk("======================================================\n");
1512 printk("[ INFO: %s-safe -> %s-unsafe lock order detected ]\n",
1513 irqclass, irqclass);
1514 print_kernel_ident();
1515 printk("------------------------------------------------------\n");
1516 printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
1517 curr->comm, task_pid_nr(curr),
1518 curr->hardirq_context, hardirq_count() >> HARDIRQ_SHIFT,
1519 curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT,
1520 curr->hardirqs_enabled,
1521 curr->softirqs_enabled);
1522 print_lock(next);
1523
1524 printk("\nand this task is already holding:\n");
1525 print_lock(prev);
1526 printk("which would create a new lock dependency:\n");
1527 print_lock_name(hlock_class(prev));
1528 printk(" ->");
1529 print_lock_name(hlock_class(next));
1530 printk("\n");
1531
1532 printk("\nbut this new dependency connects a %s-irq-safe lock:\n",
1533 irqclass);
1534 print_lock_name(backwards_entry->class);
1535 printk("\n... which became %s-irq-safe at:\n", irqclass);
1536
1537 print_stack_trace(backwards_entry->class->usage_traces + bit1, 1);
1538
1539 printk("\nto a %s-irq-unsafe lock:\n", irqclass);
1540 print_lock_name(forwards_entry->class);
1541 printk("\n... which became %s-irq-unsafe at:\n", irqclass);
1542 printk("...");
1543
1544 print_stack_trace(forwards_entry->class->usage_traces + bit2, 1);
1545
1546 printk("\nother info that might help us debug this:\n\n");
1547 print_irq_lock_scenario(backwards_entry, forwards_entry,
1548 hlock_class(prev), hlock_class(next));
1549
1550 lockdep_print_held_locks(curr);
1551
1552 printk("\nthe dependencies between %s-irq-safe lock", irqclass);
1553 printk(" and the holding lock:\n");
1554 if (!save_trace(&prev_root->trace))
1555 return 0;
1556 print_shortest_lock_dependencies(backwards_entry, prev_root);
1557
1558 printk("\nthe dependencies between the lock to be acquired");
1559 printk(" and %s-irq-unsafe lock:\n", irqclass);
1560 if (!save_trace(&next_root->trace))
1561 return 0;
1562 print_shortest_lock_dependencies(forwards_entry, next_root);
1563
1564 printk("\nstack backtrace:\n");
1565 dump_stack();
1566
1567 return 0;
1568 }
1569
1570 static int
check_usage(struct task_struct * curr,struct held_lock * prev,struct held_lock * next,enum lock_usage_bit bit_backwards,enum lock_usage_bit bit_forwards,const char * irqclass)1571 check_usage(struct task_struct *curr, struct held_lock *prev,
1572 struct held_lock *next, enum lock_usage_bit bit_backwards,
1573 enum lock_usage_bit bit_forwards, const char *irqclass)
1574 {
1575 int ret;
1576 struct lock_list this, that;
1577 struct lock_list *uninitialized_var(target_entry);
1578 struct lock_list *uninitialized_var(target_entry1);
1579
1580 this.parent = NULL;
1581
1582 this.class = hlock_class(prev);
1583 ret = find_usage_backwards(&this, bit_backwards, &target_entry);
1584 if (ret < 0)
1585 return print_bfs_bug(ret);
1586 if (ret == 1)
1587 return ret;
1588
1589 that.parent = NULL;
1590 that.class = hlock_class(next);
1591 ret = find_usage_forwards(&that, bit_forwards, &target_entry1);
1592 if (ret < 0)
1593 return print_bfs_bug(ret);
1594 if (ret == 1)
1595 return ret;
1596
1597 return print_bad_irq_dependency(curr, &this, &that,
1598 target_entry, target_entry1,
1599 prev, next,
1600 bit_backwards, bit_forwards, irqclass);
1601 }
1602
1603 static const char *state_names[] = {
1604 #define LOCKDEP_STATE(__STATE) \
1605 __stringify(__STATE),
1606 #include "lockdep_states.h"
1607 #undef LOCKDEP_STATE
1608 };
1609
1610 static const char *state_rnames[] = {
1611 #define LOCKDEP_STATE(__STATE) \
1612 __stringify(__STATE)"-READ",
1613 #include "lockdep_states.h"
1614 #undef LOCKDEP_STATE
1615 };
1616
state_name(enum lock_usage_bit bit)1617 static inline const char *state_name(enum lock_usage_bit bit)
1618 {
1619 return (bit & 1) ? state_rnames[bit >> 2] : state_names[bit >> 2];
1620 }
1621
exclusive_bit(int new_bit)1622 static int exclusive_bit(int new_bit)
1623 {
1624 /*
1625 * USED_IN
1626 * USED_IN_READ
1627 * ENABLED
1628 * ENABLED_READ
1629 *
1630 * bit 0 - write/read
1631 * bit 1 - used_in/enabled
1632 * bit 2+ state
1633 */
1634
1635 int state = new_bit & ~3;
1636 int dir = new_bit & 2;
1637
1638 /*
1639 * keep state, bit flip the direction and strip read.
1640 */
1641 return state | (dir ^ 2);
1642 }
1643
check_irq_usage(struct task_struct * curr,struct held_lock * prev,struct held_lock * next,enum lock_usage_bit bit)1644 static int check_irq_usage(struct task_struct *curr, struct held_lock *prev,
1645 struct held_lock *next, enum lock_usage_bit bit)
1646 {
1647 /*
1648 * Prove that the new dependency does not connect a hardirq-safe
1649 * lock with a hardirq-unsafe lock - to achieve this we search
1650 * the backwards-subgraph starting at <prev>, and the
1651 * forwards-subgraph starting at <next>:
1652 */
1653 if (!check_usage(curr, prev, next, bit,
1654 exclusive_bit(bit), state_name(bit)))
1655 return 0;
1656
1657 bit++; /* _READ */
1658
1659 /*
1660 * Prove that the new dependency does not connect a hardirq-safe-read
1661 * lock with a hardirq-unsafe lock - to achieve this we search
1662 * the backwards-subgraph starting at <prev>, and the
1663 * forwards-subgraph starting at <next>:
1664 */
1665 if (!check_usage(curr, prev, next, bit,
1666 exclusive_bit(bit), state_name(bit)))
1667 return 0;
1668
1669 return 1;
1670 }
1671
1672 static int
check_prev_add_irq(struct task_struct * curr,struct held_lock * prev,struct held_lock * next)1673 check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
1674 struct held_lock *next)
1675 {
1676 #define LOCKDEP_STATE(__STATE) \
1677 if (!check_irq_usage(curr, prev, next, LOCK_USED_IN_##__STATE)) \
1678 return 0;
1679 #include "lockdep_states.h"
1680 #undef LOCKDEP_STATE
1681
1682 return 1;
1683 }
1684
inc_chains(void)1685 static void inc_chains(void)
1686 {
1687 if (current->hardirq_context)
1688 nr_hardirq_chains++;
1689 else {
1690 if (current->softirq_context)
1691 nr_softirq_chains++;
1692 else
1693 nr_process_chains++;
1694 }
1695 }
1696
1697 #else
1698
1699 static inline int
check_prev_add_irq(struct task_struct * curr,struct held_lock * prev,struct held_lock * next)1700 check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
1701 struct held_lock *next)
1702 {
1703 return 1;
1704 }
1705
inc_chains(void)1706 static inline void inc_chains(void)
1707 {
1708 nr_process_chains++;
1709 }
1710
1711 #endif
1712
1713 static void
print_deadlock_scenario(struct held_lock * nxt,struct held_lock * prv)1714 print_deadlock_scenario(struct held_lock *nxt,
1715 struct held_lock *prv)
1716 {
1717 struct lock_class *next = hlock_class(nxt);
1718 struct lock_class *prev = hlock_class(prv);
1719
1720 printk(" Possible unsafe locking scenario:\n\n");
1721 printk(" CPU0\n");
1722 printk(" ----\n");
1723 printk(" lock(");
1724 __print_lock_name(prev);
1725 printk(");\n");
1726 printk(" lock(");
1727 __print_lock_name(next);
1728 printk(");\n");
1729 printk("\n *** DEADLOCK ***\n\n");
1730 printk(" May be due to missing lock nesting notation\n\n");
1731 }
1732
1733 static int
print_deadlock_bug(struct task_struct * curr,struct held_lock * prev,struct held_lock * next)1734 print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
1735 struct held_lock *next)
1736 {
1737 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1738 return 0;
1739
1740 printk("\n");
1741 printk("=============================================\n");
1742 printk("[ INFO: possible recursive locking detected ]\n");
1743 print_kernel_ident();
1744 printk("---------------------------------------------\n");
1745 printk("%s/%d is trying to acquire lock:\n",
1746 curr->comm, task_pid_nr(curr));
1747 print_lock(next);
1748 printk("\nbut task is already holding lock:\n");
1749 print_lock(prev);
1750
1751 printk("\nother info that might help us debug this:\n");
1752 print_deadlock_scenario(next, prev);
1753 lockdep_print_held_locks(curr);
1754
1755 printk("\nstack backtrace:\n");
1756 dump_stack();
1757
1758 return 0;
1759 }
1760
1761 /*
1762 * Check whether we are holding such a class already.
1763 *
1764 * (Note that this has to be done separately, because the graph cannot
1765 * detect such classes of deadlocks.)
1766 *
1767 * Returns: 0 on deadlock detected, 1 on OK, 2 on recursive read
1768 */
1769 static int
check_deadlock(struct task_struct * curr,struct held_lock * next,struct lockdep_map * next_instance,int read)1770 check_deadlock(struct task_struct *curr, struct held_lock *next,
1771 struct lockdep_map *next_instance, int read)
1772 {
1773 struct held_lock *prev;
1774 struct held_lock *nest = NULL;
1775 int i;
1776
1777 for (i = 0; i < curr->lockdep_depth; i++) {
1778 prev = curr->held_locks + i;
1779
1780 if (prev->instance == next->nest_lock)
1781 nest = prev;
1782
1783 if (hlock_class(prev) != hlock_class(next))
1784 continue;
1785
1786 /*
1787 * Allow read-after-read recursion of the same
1788 * lock class (i.e. read_lock(lock)+read_lock(lock)):
1789 */
1790 if ((read == 2) && prev->read)
1791 return 2;
1792
1793 /*
1794 * We're holding the nest_lock, which serializes this lock's
1795 * nesting behaviour.
1796 */
1797 if (nest)
1798 return 2;
1799
1800 return print_deadlock_bug(curr, prev, next);
1801 }
1802 return 1;
1803 }
1804
1805 /*
1806 * There was a chain-cache miss, and we are about to add a new dependency
1807 * to a previous lock. We recursively validate the following rules:
1808 *
1809 * - would the adding of the <prev> -> <next> dependency create a
1810 * circular dependency in the graph? [== circular deadlock]
1811 *
1812 * - does the new prev->next dependency connect any hardirq-safe lock
1813 * (in the full backwards-subgraph starting at <prev>) with any
1814 * hardirq-unsafe lock (in the full forwards-subgraph starting at
1815 * <next>)? [== illegal lock inversion with hardirq contexts]
1816 *
1817 * - does the new prev->next dependency connect any softirq-safe lock
1818 * (in the full backwards-subgraph starting at <prev>) with any
1819 * softirq-unsafe lock (in the full forwards-subgraph starting at
1820 * <next>)? [== illegal lock inversion with softirq contexts]
1821 *
1822 * any of these scenarios could lead to a deadlock.
1823 *
1824 * Then if all the validations pass, we add the forwards and backwards
1825 * dependency.
1826 */
1827 static int
check_prev_add(struct task_struct * curr,struct held_lock * prev,struct held_lock * next,int distance,int trylock_loop)1828 check_prev_add(struct task_struct *curr, struct held_lock *prev,
1829 struct held_lock *next, int distance, int trylock_loop)
1830 {
1831 struct lock_list *entry;
1832 int ret;
1833 struct lock_list this;
1834 struct lock_list *uninitialized_var(target_entry);
1835 /*
1836 * Static variable, serialized by the graph_lock().
1837 *
1838 * We use this static variable to save the stack trace in case
1839 * we call into this function multiple times due to encountering
1840 * trylocks in the held lock stack.
1841 */
1842 static struct stack_trace trace;
1843
1844 /*
1845 * Prove that the new <prev> -> <next> dependency would not
1846 * create a circular dependency in the graph. (We do this by
1847 * forward-recursing into the graph starting at <next>, and
1848 * checking whether we can reach <prev>.)
1849 *
1850 * We are using global variables to control the recursion, to
1851 * keep the stackframe size of the recursive functions low:
1852 */
1853 this.class = hlock_class(next);
1854 this.parent = NULL;
1855 ret = check_noncircular(&this, hlock_class(prev), &target_entry);
1856 if (unlikely(!ret))
1857 return print_circular_bug(&this, target_entry, next, prev);
1858 else if (unlikely(ret < 0))
1859 return print_bfs_bug(ret);
1860
1861 if (!check_prev_add_irq(curr, prev, next))
1862 return 0;
1863
1864 /*
1865 * For recursive read-locks we do all the dependency checks,
1866 * but we dont store read-triggered dependencies (only
1867 * write-triggered dependencies). This ensures that only the
1868 * write-side dependencies matter, and that if for example a
1869 * write-lock never takes any other locks, then the reads are
1870 * equivalent to a NOP.
1871 */
1872 if (next->read == 2 || prev->read == 2)
1873 return 1;
1874 /*
1875 * Is the <prev> -> <next> dependency already present?
1876 *
1877 * (this may occur even though this is a new chain: consider
1878 * e.g. the L1 -> L2 -> L3 -> L4 and the L5 -> L1 -> L2 -> L3
1879 * chains - the second one will be new, but L1 already has
1880 * L2 added to its dependency list, due to the first chain.)
1881 */
1882 list_for_each_entry(entry, &hlock_class(prev)->locks_after, entry) {
1883 if (entry->class == hlock_class(next)) {
1884 if (distance == 1)
1885 entry->distance = 1;
1886 return 2;
1887 }
1888 }
1889
1890 if (!trylock_loop && !save_trace(&trace))
1891 return 0;
1892
1893 /*
1894 * Ok, all validations passed, add the new lock
1895 * to the previous lock's dependency list:
1896 */
1897 ret = add_lock_to_list(hlock_class(prev), hlock_class(next),
1898 &hlock_class(prev)->locks_after,
1899 next->acquire_ip, distance, &trace);
1900
1901 if (!ret)
1902 return 0;
1903
1904 ret = add_lock_to_list(hlock_class(next), hlock_class(prev),
1905 &hlock_class(next)->locks_before,
1906 next->acquire_ip, distance, &trace);
1907 if (!ret)
1908 return 0;
1909
1910 /*
1911 * Debugging printouts:
1912 */
1913 if (verbose(hlock_class(prev)) || verbose(hlock_class(next))) {
1914 graph_unlock();
1915 printk("\n new dependency: ");
1916 print_lock_name(hlock_class(prev));
1917 printk(" => ");
1918 print_lock_name(hlock_class(next));
1919 printk("\n");
1920 dump_stack();
1921 return graph_lock();
1922 }
1923 return 1;
1924 }
1925
1926 /*
1927 * Add the dependency to all directly-previous locks that are 'relevant'.
1928 * The ones that are relevant are (in increasing distance from curr):
1929 * all consecutive trylock entries and the final non-trylock entry - or
1930 * the end of this context's lock-chain - whichever comes first.
1931 */
1932 static int
check_prevs_add(struct task_struct * curr,struct held_lock * next)1933 check_prevs_add(struct task_struct *curr, struct held_lock *next)
1934 {
1935 int depth = curr->lockdep_depth;
1936 int trylock_loop = 0;
1937 struct held_lock *hlock;
1938
1939 /*
1940 * Debugging checks.
1941 *
1942 * Depth must not be zero for a non-head lock:
1943 */
1944 if (!depth)
1945 goto out_bug;
1946 /*
1947 * At least two relevant locks must exist for this
1948 * to be a head:
1949 */
1950 if (curr->held_locks[depth].irq_context !=
1951 curr->held_locks[depth-1].irq_context)
1952 goto out_bug;
1953
1954 for (;;) {
1955 int distance = curr->lockdep_depth - depth + 1;
1956 hlock = curr->held_locks + depth - 1;
1957 /*
1958 * Only non-recursive-read entries get new dependencies
1959 * added:
1960 */
1961 if (hlock->read != 2 && hlock->check) {
1962 if (!check_prev_add(curr, hlock, next,
1963 distance, trylock_loop))
1964 return 0;
1965 /*
1966 * Stop after the first non-trylock entry,
1967 * as non-trylock entries have added their
1968 * own direct dependencies already, so this
1969 * lock is connected to them indirectly:
1970 */
1971 if (!hlock->trylock)
1972 break;
1973 }
1974 depth--;
1975 /*
1976 * End of lock-stack?
1977 */
1978 if (!depth)
1979 break;
1980 /*
1981 * Stop the search if we cross into another context:
1982 */
1983 if (curr->held_locks[depth].irq_context !=
1984 curr->held_locks[depth-1].irq_context)
1985 break;
1986 trylock_loop = 1;
1987 }
1988 return 1;
1989 out_bug:
1990 if (!debug_locks_off_graph_unlock())
1991 return 0;
1992
1993 /*
1994 * Clearly we all shouldn't be here, but since we made it we
1995 * can reliable say we messed up our state. See the above two
1996 * gotos for reasons why we could possibly end up here.
1997 */
1998 WARN_ON(1);
1999
2000 return 0;
2001 }
2002
2003 unsigned long nr_lock_chains;
2004 struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
2005 int nr_chain_hlocks;
2006 static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
2007
lock_chain_get_class(struct lock_chain * chain,int i)2008 struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
2009 {
2010 return lock_classes + chain_hlocks[chain->base + i];
2011 }
2012
2013 /*
2014 * Look up a dependency chain. If the key is not present yet then
2015 * add it and return 1 - in this case the new dependency chain is
2016 * validated. If the key is already hashed, return 0.
2017 * (On return with 1 graph_lock is held.)
2018 */
lookup_chain_cache(struct task_struct * curr,struct held_lock * hlock,u64 chain_key)2019 static inline int lookup_chain_cache(struct task_struct *curr,
2020 struct held_lock *hlock,
2021 u64 chain_key)
2022 {
2023 struct lock_class *class = hlock_class(hlock);
2024 struct list_head *hash_head = chainhashentry(chain_key);
2025 struct lock_chain *chain;
2026 struct held_lock *hlock_curr;
2027 int i, j;
2028
2029 /*
2030 * We might need to take the graph lock, ensure we've got IRQs
2031 * disabled to make this an IRQ-safe lock.. for recursion reasons
2032 * lockdep won't complain about its own locking errors.
2033 */
2034 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2035 return 0;
2036 /*
2037 * We can walk it lock-free, because entries only get added
2038 * to the hash:
2039 */
2040 list_for_each_entry_rcu(chain, hash_head, entry) {
2041 if (chain->chain_key == chain_key) {
2042 cache_hit:
2043 debug_atomic_inc(chain_lookup_hits);
2044 if (very_verbose(class))
2045 printk("\nhash chain already cached, key: "
2046 "%016Lx tail class: [%p] %s\n",
2047 (unsigned long long)chain_key,
2048 class->key, class->name);
2049 return 0;
2050 }
2051 }
2052 if (very_verbose(class))
2053 printk("\nnew hash chain, key: %016Lx tail class: [%p] %s\n",
2054 (unsigned long long)chain_key, class->key, class->name);
2055 /*
2056 * Allocate a new chain entry from the static array, and add
2057 * it to the hash:
2058 */
2059 if (!graph_lock())
2060 return 0;
2061 /*
2062 * We have to walk the chain again locked - to avoid duplicates:
2063 */
2064 list_for_each_entry(chain, hash_head, entry) {
2065 if (chain->chain_key == chain_key) {
2066 graph_unlock();
2067 goto cache_hit;
2068 }
2069 }
2070 if (unlikely(nr_lock_chains >= MAX_LOCKDEP_CHAINS)) {
2071 if (!debug_locks_off_graph_unlock())
2072 return 0;
2073
2074 print_lockdep_off("BUG: MAX_LOCKDEP_CHAINS too low!");
2075 dump_stack();
2076 return 0;
2077 }
2078 chain = lock_chains + nr_lock_chains++;
2079 chain->chain_key = chain_key;
2080 chain->irq_context = hlock->irq_context;
2081 /* Find the first held_lock of current chain */
2082 for (i = curr->lockdep_depth - 1; i >= 0; i--) {
2083 hlock_curr = curr->held_locks + i;
2084 if (hlock_curr->irq_context != hlock->irq_context)
2085 break;
2086 }
2087 i++;
2088 chain->depth = curr->lockdep_depth + 1 - i;
2089 if (likely(nr_chain_hlocks + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) {
2090 chain->base = nr_chain_hlocks;
2091 nr_chain_hlocks += chain->depth;
2092 for (j = 0; j < chain->depth - 1; j++, i++) {
2093 int lock_id = curr->held_locks[i].class_idx - 1;
2094 chain_hlocks[chain->base + j] = lock_id;
2095 }
2096 chain_hlocks[chain->base + j] = class - lock_classes;
2097 }
2098 list_add_tail_rcu(&chain->entry, hash_head);
2099 debug_atomic_inc(chain_lookup_misses);
2100 inc_chains();
2101
2102 return 1;
2103 }
2104
validate_chain(struct task_struct * curr,struct lockdep_map * lock,struct held_lock * hlock,int chain_head,u64 chain_key)2105 static int validate_chain(struct task_struct *curr, struct lockdep_map *lock,
2106 struct held_lock *hlock, int chain_head, u64 chain_key)
2107 {
2108 /*
2109 * Trylock needs to maintain the stack of held locks, but it
2110 * does not add new dependencies, because trylock can be done
2111 * in any order.
2112 *
2113 * We look up the chain_key and do the O(N^2) check and update of
2114 * the dependencies only if this is a new dependency chain.
2115 * (If lookup_chain_cache() returns with 1 it acquires
2116 * graph_lock for us)
2117 */
2118 if (!hlock->trylock && hlock->check &&
2119 lookup_chain_cache(curr, hlock, chain_key)) {
2120 /*
2121 * Check whether last held lock:
2122 *
2123 * - is irq-safe, if this lock is irq-unsafe
2124 * - is softirq-safe, if this lock is hardirq-unsafe
2125 *
2126 * And check whether the new lock's dependency graph
2127 * could lead back to the previous lock.
2128 *
2129 * any of these scenarios could lead to a deadlock. If
2130 * All validations
2131 */
2132 int ret = check_deadlock(curr, hlock, lock, hlock->read);
2133
2134 if (!ret)
2135 return 0;
2136 /*
2137 * Mark recursive read, as we jump over it when
2138 * building dependencies (just like we jump over
2139 * trylock entries):
2140 */
2141 if (ret == 2)
2142 hlock->read = 2;
2143 /*
2144 * Add dependency only if this lock is not the head
2145 * of the chain, and if it's not a secondary read-lock:
2146 */
2147 if (!chain_head && ret != 2)
2148 if (!check_prevs_add(curr, hlock))
2149 return 0;
2150 graph_unlock();
2151 } else
2152 /* after lookup_chain_cache(): */
2153 if (unlikely(!debug_locks))
2154 return 0;
2155
2156 return 1;
2157 }
2158 #else
validate_chain(struct task_struct * curr,struct lockdep_map * lock,struct held_lock * hlock,int chain_head,u64 chain_key)2159 static inline int validate_chain(struct task_struct *curr,
2160 struct lockdep_map *lock, struct held_lock *hlock,
2161 int chain_head, u64 chain_key)
2162 {
2163 return 1;
2164 }
2165 #endif
2166
2167 /*
2168 * We are building curr_chain_key incrementally, so double-check
2169 * it from scratch, to make sure that it's done correctly:
2170 */
check_chain_key(struct task_struct * curr)2171 static void check_chain_key(struct task_struct *curr)
2172 {
2173 #ifdef CONFIG_DEBUG_LOCKDEP
2174 struct held_lock *hlock, *prev_hlock = NULL;
2175 unsigned int i, id;
2176 u64 chain_key = 0;
2177
2178 for (i = 0; i < curr->lockdep_depth; i++) {
2179 hlock = curr->held_locks + i;
2180 if (chain_key != hlock->prev_chain_key) {
2181 debug_locks_off();
2182 /*
2183 * We got mighty confused, our chain keys don't match
2184 * with what we expect, someone trample on our task state?
2185 */
2186 WARN(1, "hm#1, depth: %u [%u], %016Lx != %016Lx\n",
2187 curr->lockdep_depth, i,
2188 (unsigned long long)chain_key,
2189 (unsigned long long)hlock->prev_chain_key);
2190 return;
2191 }
2192 id = hlock->class_idx - 1;
2193 /*
2194 * Whoops ran out of static storage again?
2195 */
2196 if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
2197 return;
2198
2199 if (prev_hlock && (prev_hlock->irq_context !=
2200 hlock->irq_context))
2201 chain_key = 0;
2202 chain_key = iterate_chain_key(chain_key, id);
2203 prev_hlock = hlock;
2204 }
2205 if (chain_key != curr->curr_chain_key) {
2206 debug_locks_off();
2207 /*
2208 * More smoking hash instead of calculating it, damn see these
2209 * numbers float.. I bet that a pink elephant stepped on my memory.
2210 */
2211 WARN(1, "hm#2, depth: %u [%u], %016Lx != %016Lx\n",
2212 curr->lockdep_depth, i,
2213 (unsigned long long)chain_key,
2214 (unsigned long long)curr->curr_chain_key);
2215 }
2216 #endif
2217 }
2218
2219 static void
print_usage_bug_scenario(struct held_lock * lock)2220 print_usage_bug_scenario(struct held_lock *lock)
2221 {
2222 struct lock_class *class = hlock_class(lock);
2223
2224 printk(" Possible unsafe locking scenario:\n\n");
2225 printk(" CPU0\n");
2226 printk(" ----\n");
2227 printk(" lock(");
2228 __print_lock_name(class);
2229 printk(");\n");
2230 printk(" <Interrupt>\n");
2231 printk(" lock(");
2232 __print_lock_name(class);
2233 printk(");\n");
2234 printk("\n *** DEADLOCK ***\n\n");
2235 }
2236
2237 static int
print_usage_bug(struct task_struct * curr,struct held_lock * this,enum lock_usage_bit prev_bit,enum lock_usage_bit new_bit)2238 print_usage_bug(struct task_struct *curr, struct held_lock *this,
2239 enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
2240 {
2241 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2242 return 0;
2243
2244 printk("\n");
2245 printk("=================================\n");
2246 printk("[ INFO: inconsistent lock state ]\n");
2247 print_kernel_ident();
2248 printk("---------------------------------\n");
2249
2250 printk("inconsistent {%s} -> {%s} usage.\n",
2251 usage_str[prev_bit], usage_str[new_bit]);
2252
2253 printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] takes:\n",
2254 curr->comm, task_pid_nr(curr),
2255 trace_hardirq_context(curr), hardirq_count() >> HARDIRQ_SHIFT,
2256 trace_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT,
2257 trace_hardirqs_enabled(curr),
2258 trace_softirqs_enabled(curr));
2259 print_lock(this);
2260
2261 printk("{%s} state was registered at:\n", usage_str[prev_bit]);
2262 print_stack_trace(hlock_class(this)->usage_traces + prev_bit, 1);
2263
2264 print_irqtrace_events(curr);
2265 printk("\nother info that might help us debug this:\n");
2266 print_usage_bug_scenario(this);
2267
2268 lockdep_print_held_locks(curr);
2269
2270 printk("\nstack backtrace:\n");
2271 dump_stack();
2272
2273 return 0;
2274 }
2275
2276 /*
2277 * Print out an error if an invalid bit is set:
2278 */
2279 static inline int
valid_state(struct task_struct * curr,struct held_lock * this,enum lock_usage_bit new_bit,enum lock_usage_bit bad_bit)2280 valid_state(struct task_struct *curr, struct held_lock *this,
2281 enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit)
2282 {
2283 if (unlikely(hlock_class(this)->usage_mask & (1 << bad_bit)))
2284 return print_usage_bug(curr, this, bad_bit, new_bit);
2285 return 1;
2286 }
2287
2288 static int mark_lock(struct task_struct *curr, struct held_lock *this,
2289 enum lock_usage_bit new_bit);
2290
2291 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
2292
2293 /*
2294 * print irq inversion bug:
2295 */
2296 static int
print_irq_inversion_bug(struct task_struct * curr,struct lock_list * root,struct lock_list * other,struct held_lock * this,int forwards,const char * irqclass)2297 print_irq_inversion_bug(struct task_struct *curr,
2298 struct lock_list *root, struct lock_list *other,
2299 struct held_lock *this, int forwards,
2300 const char *irqclass)
2301 {
2302 struct lock_list *entry = other;
2303 struct lock_list *middle = NULL;
2304 int depth;
2305
2306 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2307 return 0;
2308
2309 printk("\n");
2310 printk("=========================================================\n");
2311 printk("[ INFO: possible irq lock inversion dependency detected ]\n");
2312 print_kernel_ident();
2313 printk("---------------------------------------------------------\n");
2314 printk("%s/%d just changed the state of lock:\n",
2315 curr->comm, task_pid_nr(curr));
2316 print_lock(this);
2317 if (forwards)
2318 printk("but this lock took another, %s-unsafe lock in the past:\n", irqclass);
2319 else
2320 printk("but this lock was taken by another, %s-safe lock in the past:\n", irqclass);
2321 print_lock_name(other->class);
2322 printk("\n\nand interrupts could create inverse lock ordering between them.\n\n");
2323
2324 printk("\nother info that might help us debug this:\n");
2325
2326 /* Find a middle lock (if one exists) */
2327 depth = get_lock_depth(other);
2328 do {
2329 if (depth == 0 && (entry != root)) {
2330 printk("lockdep:%s bad path found in chain graph\n", __func__);
2331 break;
2332 }
2333 middle = entry;
2334 entry = get_lock_parent(entry);
2335 depth--;
2336 } while (entry && entry != root && (depth >= 0));
2337 if (forwards)
2338 print_irq_lock_scenario(root, other,
2339 middle ? middle->class : root->class, other->class);
2340 else
2341 print_irq_lock_scenario(other, root,
2342 middle ? middle->class : other->class, root->class);
2343
2344 lockdep_print_held_locks(curr);
2345
2346 printk("\nthe shortest dependencies between 2nd lock and 1st lock:\n");
2347 if (!save_trace(&root->trace))
2348 return 0;
2349 print_shortest_lock_dependencies(other, root);
2350
2351 printk("\nstack backtrace:\n");
2352 dump_stack();
2353
2354 return 0;
2355 }
2356
2357 /*
2358 * Prove that in the forwards-direction subgraph starting at <this>
2359 * there is no lock matching <mask>:
2360 */
2361 static int
check_usage_forwards(struct task_struct * curr,struct held_lock * this,enum lock_usage_bit bit,const char * irqclass)2362 check_usage_forwards(struct task_struct *curr, struct held_lock *this,
2363 enum lock_usage_bit bit, const char *irqclass)
2364 {
2365 int ret;
2366 struct lock_list root;
2367 struct lock_list *uninitialized_var(target_entry);
2368
2369 root.parent = NULL;
2370 root.class = hlock_class(this);
2371 ret = find_usage_forwards(&root, bit, &target_entry);
2372 if (ret < 0)
2373 return print_bfs_bug(ret);
2374 if (ret == 1)
2375 return ret;
2376
2377 return print_irq_inversion_bug(curr, &root, target_entry,
2378 this, 1, irqclass);
2379 }
2380
2381 /*
2382 * Prove that in the backwards-direction subgraph starting at <this>
2383 * there is no lock matching <mask>:
2384 */
2385 static int
check_usage_backwards(struct task_struct * curr,struct held_lock * this,enum lock_usage_bit bit,const char * irqclass)2386 check_usage_backwards(struct task_struct *curr, struct held_lock *this,
2387 enum lock_usage_bit bit, const char *irqclass)
2388 {
2389 int ret;
2390 struct lock_list root;
2391 struct lock_list *uninitialized_var(target_entry);
2392
2393 root.parent = NULL;
2394 root.class = hlock_class(this);
2395 ret = find_usage_backwards(&root, bit, &target_entry);
2396 if (ret < 0)
2397 return print_bfs_bug(ret);
2398 if (ret == 1)
2399 return ret;
2400
2401 return print_irq_inversion_bug(curr, &root, target_entry,
2402 this, 0, irqclass);
2403 }
2404
print_irqtrace_events(struct task_struct * curr)2405 void print_irqtrace_events(struct task_struct *curr)
2406 {
2407 printk("irq event stamp: %u\n", curr->irq_events);
2408 printk("hardirqs last enabled at (%u): ", curr->hardirq_enable_event);
2409 print_ip_sym(curr->hardirq_enable_ip);
2410 printk("hardirqs last disabled at (%u): ", curr->hardirq_disable_event);
2411 print_ip_sym(curr->hardirq_disable_ip);
2412 printk("softirqs last enabled at (%u): ", curr->softirq_enable_event);
2413 print_ip_sym(curr->softirq_enable_ip);
2414 printk("softirqs last disabled at (%u): ", curr->softirq_disable_event);
2415 print_ip_sym(curr->softirq_disable_ip);
2416 }
2417
HARDIRQ_verbose(struct lock_class * class)2418 static int HARDIRQ_verbose(struct lock_class *class)
2419 {
2420 #if HARDIRQ_VERBOSE
2421 return class_filter(class);
2422 #endif
2423 return 0;
2424 }
2425
SOFTIRQ_verbose(struct lock_class * class)2426 static int SOFTIRQ_verbose(struct lock_class *class)
2427 {
2428 #if SOFTIRQ_VERBOSE
2429 return class_filter(class);
2430 #endif
2431 return 0;
2432 }
2433
RECLAIM_FS_verbose(struct lock_class * class)2434 static int RECLAIM_FS_verbose(struct lock_class *class)
2435 {
2436 #if RECLAIM_VERBOSE
2437 return class_filter(class);
2438 #endif
2439 return 0;
2440 }
2441
2442 #define STRICT_READ_CHECKS 1
2443
2444 static int (*state_verbose_f[])(struct lock_class *class) = {
2445 #define LOCKDEP_STATE(__STATE) \
2446 __STATE##_verbose,
2447 #include "lockdep_states.h"
2448 #undef LOCKDEP_STATE
2449 };
2450
state_verbose(enum lock_usage_bit bit,struct lock_class * class)2451 static inline int state_verbose(enum lock_usage_bit bit,
2452 struct lock_class *class)
2453 {
2454 return state_verbose_f[bit >> 2](class);
2455 }
2456
2457 typedef int (*check_usage_f)(struct task_struct *, struct held_lock *,
2458 enum lock_usage_bit bit, const char *name);
2459
2460 static int
mark_lock_irq(struct task_struct * curr,struct held_lock * this,enum lock_usage_bit new_bit)2461 mark_lock_irq(struct task_struct *curr, struct held_lock *this,
2462 enum lock_usage_bit new_bit)
2463 {
2464 int excl_bit = exclusive_bit(new_bit);
2465 int read = new_bit & 1;
2466 int dir = new_bit & 2;
2467
2468 /*
2469 * mark USED_IN has to look forwards -- to ensure no dependency
2470 * has ENABLED state, which would allow recursion deadlocks.
2471 *
2472 * mark ENABLED has to look backwards -- to ensure no dependee
2473 * has USED_IN state, which, again, would allow recursion deadlocks.
2474 */
2475 check_usage_f usage = dir ?
2476 check_usage_backwards : check_usage_forwards;
2477
2478 /*
2479 * Validate that this particular lock does not have conflicting
2480 * usage states.
2481 */
2482 if (!valid_state(curr, this, new_bit, excl_bit))
2483 return 0;
2484
2485 /*
2486 * Validate that the lock dependencies don't have conflicting usage
2487 * states.
2488 */
2489 if ((!read || !dir || STRICT_READ_CHECKS) &&
2490 !usage(curr, this, excl_bit, state_name(new_bit & ~1)))
2491 return 0;
2492
2493 /*
2494 * Check for read in write conflicts
2495 */
2496 if (!read) {
2497 if (!valid_state(curr, this, new_bit, excl_bit + 1))
2498 return 0;
2499
2500 if (STRICT_READ_CHECKS &&
2501 !usage(curr, this, excl_bit + 1,
2502 state_name(new_bit + 1)))
2503 return 0;
2504 }
2505
2506 if (state_verbose(new_bit, hlock_class(this)))
2507 return 2;
2508
2509 return 1;
2510 }
2511
2512 enum mark_type {
2513 #define LOCKDEP_STATE(__STATE) __STATE,
2514 #include "lockdep_states.h"
2515 #undef LOCKDEP_STATE
2516 };
2517
2518 /*
2519 * Mark all held locks with a usage bit:
2520 */
2521 static int
mark_held_locks(struct task_struct * curr,enum mark_type mark)2522 mark_held_locks(struct task_struct *curr, enum mark_type mark)
2523 {
2524 enum lock_usage_bit usage_bit;
2525 struct held_lock *hlock;
2526 int i;
2527
2528 for (i = 0; i < curr->lockdep_depth; i++) {
2529 hlock = curr->held_locks + i;
2530
2531 usage_bit = 2 + (mark << 2); /* ENABLED */
2532 if (hlock->read)
2533 usage_bit += 1; /* READ */
2534
2535 BUG_ON(usage_bit >= LOCK_USAGE_STATES);
2536
2537 if (!hlock->check)
2538 continue;
2539
2540 if (!mark_lock(curr, hlock, usage_bit))
2541 return 0;
2542 }
2543
2544 return 1;
2545 }
2546
2547 /*
2548 * Hardirqs will be enabled:
2549 */
__trace_hardirqs_on_caller(unsigned long ip)2550 static void __trace_hardirqs_on_caller(unsigned long ip)
2551 {
2552 struct task_struct *curr = current;
2553
2554 /* we'll do an OFF -> ON transition: */
2555 curr->hardirqs_enabled = 1;
2556
2557 /*
2558 * We are going to turn hardirqs on, so set the
2559 * usage bit for all held locks:
2560 */
2561 if (!mark_held_locks(curr, HARDIRQ))
2562 return;
2563 /*
2564 * If we have softirqs enabled, then set the usage
2565 * bit for all held locks. (disabled hardirqs prevented
2566 * this bit from being set before)
2567 */
2568 if (curr->softirqs_enabled)
2569 if (!mark_held_locks(curr, SOFTIRQ))
2570 return;
2571
2572 curr->hardirq_enable_ip = ip;
2573 curr->hardirq_enable_event = ++curr->irq_events;
2574 debug_atomic_inc(hardirqs_on_events);
2575 }
2576
trace_hardirqs_on_caller(unsigned long ip)2577 __visible void trace_hardirqs_on_caller(unsigned long ip)
2578 {
2579 time_hardirqs_on(CALLER_ADDR0, ip);
2580
2581 if (unlikely(!debug_locks || current->lockdep_recursion))
2582 return;
2583
2584 if (unlikely(current->hardirqs_enabled)) {
2585 /*
2586 * Neither irq nor preemption are disabled here
2587 * so this is racy by nature but losing one hit
2588 * in a stat is not a big deal.
2589 */
2590 __debug_atomic_inc(redundant_hardirqs_on);
2591 return;
2592 }
2593
2594 /*
2595 * We're enabling irqs and according to our state above irqs weren't
2596 * already enabled, yet we find the hardware thinks they are in fact
2597 * enabled.. someone messed up their IRQ state tracing.
2598 */
2599 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2600 return;
2601
2602 /*
2603 * See the fine text that goes along with this variable definition.
2604 */
2605 if (DEBUG_LOCKS_WARN_ON(unlikely(early_boot_irqs_disabled)))
2606 return;
2607
2608 /*
2609 * Can't allow enabling interrupts while in an interrupt handler,
2610 * that's general bad form and such. Recursion, limited stack etc..
2611 */
2612 if (DEBUG_LOCKS_WARN_ON(current->hardirq_context))
2613 return;
2614
2615 current->lockdep_recursion = 1;
2616 __trace_hardirqs_on_caller(ip);
2617 current->lockdep_recursion = 0;
2618 }
2619 EXPORT_SYMBOL(trace_hardirqs_on_caller);
2620
trace_hardirqs_on(void)2621 void trace_hardirqs_on(void)
2622 {
2623 trace_hardirqs_on_caller(CALLER_ADDR0);
2624 }
2625 EXPORT_SYMBOL(trace_hardirqs_on);
2626
2627 /*
2628 * Hardirqs were disabled:
2629 */
trace_hardirqs_off_caller(unsigned long ip)2630 __visible void trace_hardirqs_off_caller(unsigned long ip)
2631 {
2632 struct task_struct *curr = current;
2633
2634 time_hardirqs_off(CALLER_ADDR0, ip);
2635
2636 if (unlikely(!debug_locks || current->lockdep_recursion))
2637 return;
2638
2639 /*
2640 * So we're supposed to get called after you mask local IRQs, but for
2641 * some reason the hardware doesn't quite think you did a proper job.
2642 */
2643 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2644 return;
2645
2646 if (curr->hardirqs_enabled) {
2647 /*
2648 * We have done an ON -> OFF transition:
2649 */
2650 curr->hardirqs_enabled = 0;
2651 curr->hardirq_disable_ip = ip;
2652 curr->hardirq_disable_event = ++curr->irq_events;
2653 debug_atomic_inc(hardirqs_off_events);
2654 } else
2655 debug_atomic_inc(redundant_hardirqs_off);
2656 }
2657 EXPORT_SYMBOL(trace_hardirqs_off_caller);
2658
trace_hardirqs_off(void)2659 void trace_hardirqs_off(void)
2660 {
2661 trace_hardirqs_off_caller(CALLER_ADDR0);
2662 }
2663 EXPORT_SYMBOL(trace_hardirqs_off);
2664
2665 /*
2666 * Softirqs will be enabled:
2667 */
trace_softirqs_on(unsigned long ip)2668 void trace_softirqs_on(unsigned long ip)
2669 {
2670 struct task_struct *curr = current;
2671
2672 if (unlikely(!debug_locks || current->lockdep_recursion))
2673 return;
2674
2675 /*
2676 * We fancy IRQs being disabled here, see softirq.c, avoids
2677 * funny state and nesting things.
2678 */
2679 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2680 return;
2681
2682 if (curr->softirqs_enabled) {
2683 debug_atomic_inc(redundant_softirqs_on);
2684 return;
2685 }
2686
2687 current->lockdep_recursion = 1;
2688 /*
2689 * We'll do an OFF -> ON transition:
2690 */
2691 curr->softirqs_enabled = 1;
2692 curr->softirq_enable_ip = ip;
2693 curr->softirq_enable_event = ++curr->irq_events;
2694 debug_atomic_inc(softirqs_on_events);
2695 /*
2696 * We are going to turn softirqs on, so set the
2697 * usage bit for all held locks, if hardirqs are
2698 * enabled too:
2699 */
2700 if (curr->hardirqs_enabled)
2701 mark_held_locks(curr, SOFTIRQ);
2702 current->lockdep_recursion = 0;
2703 }
2704
2705 /*
2706 * Softirqs were disabled:
2707 */
trace_softirqs_off(unsigned long ip)2708 void trace_softirqs_off(unsigned long ip)
2709 {
2710 struct task_struct *curr = current;
2711
2712 if (unlikely(!debug_locks || current->lockdep_recursion))
2713 return;
2714
2715 /*
2716 * We fancy IRQs being disabled here, see softirq.c
2717 */
2718 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2719 return;
2720
2721 if (curr->softirqs_enabled) {
2722 /*
2723 * We have done an ON -> OFF transition:
2724 */
2725 curr->softirqs_enabled = 0;
2726 curr->softirq_disable_ip = ip;
2727 curr->softirq_disable_event = ++curr->irq_events;
2728 debug_atomic_inc(softirqs_off_events);
2729 /*
2730 * Whoops, we wanted softirqs off, so why aren't they?
2731 */
2732 DEBUG_LOCKS_WARN_ON(!softirq_count());
2733 } else
2734 debug_atomic_inc(redundant_softirqs_off);
2735 }
2736
__lockdep_trace_alloc(gfp_t gfp_mask,unsigned long flags)2737 static void __lockdep_trace_alloc(gfp_t gfp_mask, unsigned long flags)
2738 {
2739 struct task_struct *curr = current;
2740
2741 if (unlikely(!debug_locks))
2742 return;
2743
2744 /* no reclaim without waiting on it */
2745 if (!(gfp_mask & __GFP_DIRECT_RECLAIM))
2746 return;
2747
2748 /* this guy won't enter reclaim */
2749 if ((curr->flags & PF_MEMALLOC) && !(gfp_mask & __GFP_NOMEMALLOC))
2750 return;
2751
2752 /* We're only interested __GFP_FS allocations for now */
2753 if (!(gfp_mask & __GFP_FS))
2754 return;
2755
2756 /*
2757 * Oi! Can't be having __GFP_FS allocations with IRQs disabled.
2758 */
2759 if (DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags)))
2760 return;
2761
2762 mark_held_locks(curr, RECLAIM_FS);
2763 }
2764
2765 static void check_flags(unsigned long flags);
2766
lockdep_trace_alloc(gfp_t gfp_mask)2767 void lockdep_trace_alloc(gfp_t gfp_mask)
2768 {
2769 unsigned long flags;
2770
2771 if (unlikely(current->lockdep_recursion))
2772 return;
2773
2774 raw_local_irq_save(flags);
2775 check_flags(flags);
2776 current->lockdep_recursion = 1;
2777 __lockdep_trace_alloc(gfp_mask, flags);
2778 current->lockdep_recursion = 0;
2779 raw_local_irq_restore(flags);
2780 }
2781
mark_irqflags(struct task_struct * curr,struct held_lock * hlock)2782 static int mark_irqflags(struct task_struct *curr, struct held_lock *hlock)
2783 {
2784 /*
2785 * If non-trylock use in a hardirq or softirq context, then
2786 * mark the lock as used in these contexts:
2787 */
2788 if (!hlock->trylock) {
2789 if (hlock->read) {
2790 if (curr->hardirq_context)
2791 if (!mark_lock(curr, hlock,
2792 LOCK_USED_IN_HARDIRQ_READ))
2793 return 0;
2794 if (curr->softirq_context)
2795 if (!mark_lock(curr, hlock,
2796 LOCK_USED_IN_SOFTIRQ_READ))
2797 return 0;
2798 } else {
2799 if (curr->hardirq_context)
2800 if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ))
2801 return 0;
2802 if (curr->softirq_context)
2803 if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ))
2804 return 0;
2805 }
2806 }
2807 if (!hlock->hardirqs_off) {
2808 if (hlock->read) {
2809 if (!mark_lock(curr, hlock,
2810 LOCK_ENABLED_HARDIRQ_READ))
2811 return 0;
2812 if (curr->softirqs_enabled)
2813 if (!mark_lock(curr, hlock,
2814 LOCK_ENABLED_SOFTIRQ_READ))
2815 return 0;
2816 } else {
2817 if (!mark_lock(curr, hlock,
2818 LOCK_ENABLED_HARDIRQ))
2819 return 0;
2820 if (curr->softirqs_enabled)
2821 if (!mark_lock(curr, hlock,
2822 LOCK_ENABLED_SOFTIRQ))
2823 return 0;
2824 }
2825 }
2826
2827 /*
2828 * We reuse the irq context infrastructure more broadly as a general
2829 * context checking code. This tests GFP_FS recursion (a lock taken
2830 * during reclaim for a GFP_FS allocation is held over a GFP_FS
2831 * allocation).
2832 */
2833 if (!hlock->trylock && (curr->lockdep_reclaim_gfp & __GFP_FS)) {
2834 if (hlock->read) {
2835 if (!mark_lock(curr, hlock, LOCK_USED_IN_RECLAIM_FS_READ))
2836 return 0;
2837 } else {
2838 if (!mark_lock(curr, hlock, LOCK_USED_IN_RECLAIM_FS))
2839 return 0;
2840 }
2841 }
2842
2843 return 1;
2844 }
2845
separate_irq_context(struct task_struct * curr,struct held_lock * hlock)2846 static int separate_irq_context(struct task_struct *curr,
2847 struct held_lock *hlock)
2848 {
2849 unsigned int depth = curr->lockdep_depth;
2850
2851 /*
2852 * Keep track of points where we cross into an interrupt context:
2853 */
2854 hlock->irq_context = 2*(curr->hardirq_context ? 1 : 0) +
2855 curr->softirq_context;
2856 if (depth) {
2857 struct held_lock *prev_hlock;
2858
2859 prev_hlock = curr->held_locks + depth-1;
2860 /*
2861 * If we cross into another context, reset the
2862 * hash key (this also prevents the checking and the
2863 * adding of the dependency to 'prev'):
2864 */
2865 if (prev_hlock->irq_context != hlock->irq_context)
2866 return 1;
2867 }
2868 return 0;
2869 }
2870
2871 #else /* defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING) */
2872
2873 static inline
mark_lock_irq(struct task_struct * curr,struct held_lock * this,enum lock_usage_bit new_bit)2874 int mark_lock_irq(struct task_struct *curr, struct held_lock *this,
2875 enum lock_usage_bit new_bit)
2876 {
2877 WARN_ON(1); /* Impossible innit? when we don't have TRACE_IRQFLAG */
2878 return 1;
2879 }
2880
mark_irqflags(struct task_struct * curr,struct held_lock * hlock)2881 static inline int mark_irqflags(struct task_struct *curr,
2882 struct held_lock *hlock)
2883 {
2884 return 1;
2885 }
2886
separate_irq_context(struct task_struct * curr,struct held_lock * hlock)2887 static inline int separate_irq_context(struct task_struct *curr,
2888 struct held_lock *hlock)
2889 {
2890 return 0;
2891 }
2892
lockdep_trace_alloc(gfp_t gfp_mask)2893 void lockdep_trace_alloc(gfp_t gfp_mask)
2894 {
2895 }
2896
2897 #endif /* defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING) */
2898
2899 /*
2900 * Mark a lock with a usage bit, and validate the state transition:
2901 */
mark_lock(struct task_struct * curr,struct held_lock * this,enum lock_usage_bit new_bit)2902 static int mark_lock(struct task_struct *curr, struct held_lock *this,
2903 enum lock_usage_bit new_bit)
2904 {
2905 unsigned int new_mask = 1 << new_bit, ret = 1;
2906
2907 /*
2908 * If already set then do not dirty the cacheline,
2909 * nor do any checks:
2910 */
2911 if (likely(hlock_class(this)->usage_mask & new_mask))
2912 return 1;
2913
2914 if (!graph_lock())
2915 return 0;
2916 /*
2917 * Make sure we didn't race:
2918 */
2919 if (unlikely(hlock_class(this)->usage_mask & new_mask)) {
2920 graph_unlock();
2921 return 1;
2922 }
2923
2924 hlock_class(this)->usage_mask |= new_mask;
2925
2926 if (!save_trace(hlock_class(this)->usage_traces + new_bit))
2927 return 0;
2928
2929 switch (new_bit) {
2930 #define LOCKDEP_STATE(__STATE) \
2931 case LOCK_USED_IN_##__STATE: \
2932 case LOCK_USED_IN_##__STATE##_READ: \
2933 case LOCK_ENABLED_##__STATE: \
2934 case LOCK_ENABLED_##__STATE##_READ:
2935 #include "lockdep_states.h"
2936 #undef LOCKDEP_STATE
2937 ret = mark_lock_irq(curr, this, new_bit);
2938 if (!ret)
2939 return 0;
2940 break;
2941 case LOCK_USED:
2942 debug_atomic_dec(nr_unused_locks);
2943 break;
2944 default:
2945 if (!debug_locks_off_graph_unlock())
2946 return 0;
2947 WARN_ON(1);
2948 return 0;
2949 }
2950
2951 graph_unlock();
2952
2953 /*
2954 * We must printk outside of the graph_lock:
2955 */
2956 if (ret == 2) {
2957 printk("\nmarked lock as {%s}:\n", usage_str[new_bit]);
2958 print_lock(this);
2959 print_irqtrace_events(curr);
2960 dump_stack();
2961 }
2962
2963 return ret;
2964 }
2965
2966 /*
2967 * Initialize a lock instance's lock-class mapping info:
2968 */
lockdep_init_map(struct lockdep_map * lock,const char * name,struct lock_class_key * key,int subclass)2969 void lockdep_init_map(struct lockdep_map *lock, const char *name,
2970 struct lock_class_key *key, int subclass)
2971 {
2972 int i;
2973
2974 kmemcheck_mark_initialized(lock, sizeof(*lock));
2975
2976 for (i = 0; i < NR_LOCKDEP_CACHING_CLASSES; i++)
2977 lock->class_cache[i] = NULL;
2978
2979 #ifdef CONFIG_LOCK_STAT
2980 lock->cpu = raw_smp_processor_id();
2981 #endif
2982
2983 /*
2984 * Can't be having no nameless bastards around this place!
2985 */
2986 if (DEBUG_LOCKS_WARN_ON(!name)) {
2987 lock->name = "NULL";
2988 return;
2989 }
2990
2991 lock->name = name;
2992
2993 /*
2994 * No key, no joy, we need to hash something.
2995 */
2996 if (DEBUG_LOCKS_WARN_ON(!key))
2997 return;
2998 /*
2999 * Sanity check, the lock-class key must be persistent:
3000 */
3001 if (!static_obj(key)) {
3002 printk("BUG: key %p not in .data!\n", key);
3003 /*
3004 * What it says above ^^^^^, I suggest you read it.
3005 */
3006 DEBUG_LOCKS_WARN_ON(1);
3007 return;
3008 }
3009 lock->key = key;
3010
3011 if (unlikely(!debug_locks))
3012 return;
3013
3014 if (subclass) {
3015 unsigned long flags;
3016
3017 if (DEBUG_LOCKS_WARN_ON(current->lockdep_recursion))
3018 return;
3019
3020 raw_local_irq_save(flags);
3021 current->lockdep_recursion = 1;
3022 register_lock_class(lock, subclass, 1);
3023 current->lockdep_recursion = 0;
3024 raw_local_irq_restore(flags);
3025 }
3026 }
3027 EXPORT_SYMBOL_GPL(lockdep_init_map);
3028
3029 struct lock_class_key __lockdep_no_validate__;
3030 EXPORT_SYMBOL_GPL(__lockdep_no_validate__);
3031
3032 static int
print_lock_nested_lock_not_held(struct task_struct * curr,struct held_lock * hlock,unsigned long ip)3033 print_lock_nested_lock_not_held(struct task_struct *curr,
3034 struct held_lock *hlock,
3035 unsigned long ip)
3036 {
3037 if (!debug_locks_off())
3038 return 0;
3039 if (debug_locks_silent)
3040 return 0;
3041
3042 printk("\n");
3043 printk("==================================\n");
3044 printk("[ BUG: Nested lock was not taken ]\n");
3045 print_kernel_ident();
3046 printk("----------------------------------\n");
3047
3048 printk("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr));
3049 print_lock(hlock);
3050
3051 printk("\nbut this task is not holding:\n");
3052 printk("%s\n", hlock->nest_lock->name);
3053
3054 printk("\nstack backtrace:\n");
3055 dump_stack();
3056
3057 printk("\nother info that might help us debug this:\n");
3058 lockdep_print_held_locks(curr);
3059
3060 printk("\nstack backtrace:\n");
3061 dump_stack();
3062
3063 return 0;
3064 }
3065
3066 static int __lock_is_held(struct lockdep_map *lock);
3067
3068 /*
3069 * This gets called for every mutex_lock*()/spin_lock*() operation.
3070 * We maintain the dependency maps and validate the locking attempt:
3071 */
__lock_acquire(struct lockdep_map * lock,unsigned int subclass,int trylock,int read,int check,int hardirqs_off,struct lockdep_map * nest_lock,unsigned long ip,int references,int pin_count)3072 static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
3073 int trylock, int read, int check, int hardirqs_off,
3074 struct lockdep_map *nest_lock, unsigned long ip,
3075 int references, int pin_count)
3076 {
3077 struct task_struct *curr = current;
3078 struct lock_class *class = NULL;
3079 struct held_lock *hlock;
3080 unsigned int depth, id;
3081 int chain_head = 0;
3082 int class_idx;
3083 u64 chain_key;
3084
3085 if (unlikely(!debug_locks))
3086 return 0;
3087
3088 /*
3089 * Lockdep should run with IRQs disabled, otherwise we could
3090 * get an interrupt which would want to take locks, which would
3091 * end up in lockdep and have you got a head-ache already?
3092 */
3093 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
3094 return 0;
3095
3096 if (!prove_locking || lock->key == &__lockdep_no_validate__)
3097 check = 0;
3098
3099 if (subclass < NR_LOCKDEP_CACHING_CLASSES)
3100 class = lock->class_cache[subclass];
3101 /*
3102 * Not cached?
3103 */
3104 if (unlikely(!class)) {
3105 class = register_lock_class(lock, subclass, 0);
3106 if (!class)
3107 return 0;
3108 }
3109 atomic_inc((atomic_t *)&class->ops);
3110 if (very_verbose(class)) {
3111 printk("\nacquire class [%p] %s", class->key, class->name);
3112 if (class->name_version > 1)
3113 printk("#%d", class->name_version);
3114 printk("\n");
3115 dump_stack();
3116 }
3117
3118 /*
3119 * Add the lock to the list of currently held locks.
3120 * (we dont increase the depth just yet, up until the
3121 * dependency checks are done)
3122 */
3123 depth = curr->lockdep_depth;
3124 /*
3125 * Ran out of static storage for our per-task lock stack again have we?
3126 */
3127 if (DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH))
3128 return 0;
3129
3130 class_idx = class - lock_classes + 1;
3131
3132 if (depth) {
3133 hlock = curr->held_locks + depth - 1;
3134 if (hlock->class_idx == class_idx && nest_lock) {
3135 if (!references)
3136 references++;
3137
3138 if (!hlock->references)
3139 hlock->references++;
3140
3141 hlock->references += references;
3142
3143 /* Overflow */
3144 if (DEBUG_LOCKS_WARN_ON(hlock->references < references))
3145 return 0;
3146
3147 return 1;
3148 }
3149 }
3150
3151 hlock = curr->held_locks + depth;
3152 /*
3153 * Plain impossible, we just registered it and checked it weren't no
3154 * NULL like.. I bet this mushroom I ate was good!
3155 */
3156 if (DEBUG_LOCKS_WARN_ON(!class))
3157 return 0;
3158 hlock->class_idx = class_idx;
3159 hlock->acquire_ip = ip;
3160 hlock->instance = lock;
3161 hlock->nest_lock = nest_lock;
3162 hlock->trylock = trylock;
3163 hlock->read = read;
3164 hlock->check = check;
3165 hlock->hardirqs_off = !!hardirqs_off;
3166 hlock->references = references;
3167 #ifdef CONFIG_LOCK_STAT
3168 hlock->waittime_stamp = 0;
3169 hlock->holdtime_stamp = lockstat_clock();
3170 #endif
3171 hlock->pin_count = pin_count;
3172
3173 if (check && !mark_irqflags(curr, hlock))
3174 return 0;
3175
3176 /* mark it as used: */
3177 if (!mark_lock(curr, hlock, LOCK_USED))
3178 return 0;
3179
3180 /*
3181 * Calculate the chain hash: it's the combined hash of all the
3182 * lock keys along the dependency chain. We save the hash value
3183 * at every step so that we can get the current hash easily
3184 * after unlock. The chain hash is then used to cache dependency
3185 * results.
3186 *
3187 * The 'key ID' is what is the most compact key value to drive
3188 * the hash, not class->key.
3189 */
3190 id = class - lock_classes;
3191 /*
3192 * Whoops, we did it again.. ran straight out of our static allocation.
3193 */
3194 if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
3195 return 0;
3196
3197 chain_key = curr->curr_chain_key;
3198 if (!depth) {
3199 /*
3200 * How can we have a chain hash when we ain't got no keys?!
3201 */
3202 if (DEBUG_LOCKS_WARN_ON(chain_key != 0))
3203 return 0;
3204 chain_head = 1;
3205 }
3206
3207 hlock->prev_chain_key = chain_key;
3208 if (separate_irq_context(curr, hlock)) {
3209 chain_key = 0;
3210 chain_head = 1;
3211 }
3212 chain_key = iterate_chain_key(chain_key, id);
3213
3214 if (nest_lock && !__lock_is_held(nest_lock))
3215 return print_lock_nested_lock_not_held(curr, hlock, ip);
3216
3217 if (!validate_chain(curr, lock, hlock, chain_head, chain_key))
3218 return 0;
3219
3220 curr->curr_chain_key = chain_key;
3221 curr->lockdep_depth++;
3222 check_chain_key(curr);
3223 #ifdef CONFIG_DEBUG_LOCKDEP
3224 if (unlikely(!debug_locks))
3225 return 0;
3226 #endif
3227 if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
3228 debug_locks_off();
3229 print_lockdep_off("BUG: MAX_LOCK_DEPTH too low!");
3230 printk(KERN_DEBUG "depth: %i max: %lu!\n",
3231 curr->lockdep_depth, MAX_LOCK_DEPTH);
3232
3233 lockdep_print_held_locks(current);
3234 debug_show_all_locks();
3235 dump_stack();
3236
3237 return 0;
3238 }
3239
3240 if (unlikely(curr->lockdep_depth > max_lockdep_depth))
3241 max_lockdep_depth = curr->lockdep_depth;
3242
3243 return 1;
3244 }
3245
3246 static int
print_unlock_imbalance_bug(struct task_struct * curr,struct lockdep_map * lock,unsigned long ip)3247 print_unlock_imbalance_bug(struct task_struct *curr, struct lockdep_map *lock,
3248 unsigned long ip)
3249 {
3250 if (!debug_locks_off())
3251 return 0;
3252 if (debug_locks_silent)
3253 return 0;
3254
3255 printk("\n");
3256 printk("=====================================\n");
3257 printk("[ BUG: bad unlock balance detected! ]\n");
3258 print_kernel_ident();
3259 printk("-------------------------------------\n");
3260 printk("%s/%d is trying to release lock (",
3261 curr->comm, task_pid_nr(curr));
3262 print_lockdep_cache(lock);
3263 printk(") at:\n");
3264 print_ip_sym(ip);
3265 printk("but there are no more locks to release!\n");
3266 printk("\nother info that might help us debug this:\n");
3267 lockdep_print_held_locks(curr);
3268
3269 printk("\nstack backtrace:\n");
3270 dump_stack();
3271
3272 return 0;
3273 }
3274
match_held_lock(struct held_lock * hlock,struct lockdep_map * lock)3275 static int match_held_lock(struct held_lock *hlock, struct lockdep_map *lock)
3276 {
3277 if (hlock->instance == lock)
3278 return 1;
3279
3280 if (hlock->references) {
3281 struct lock_class *class = lock->class_cache[0];
3282
3283 if (!class)
3284 class = look_up_lock_class(lock, 0);
3285
3286 /*
3287 * If look_up_lock_class() failed to find a class, we're trying
3288 * to test if we hold a lock that has never yet been acquired.
3289 * Clearly if the lock hasn't been acquired _ever_, we're not
3290 * holding it either, so report failure.
3291 */
3292 if (!class)
3293 return 0;
3294
3295 /*
3296 * References, but not a lock we're actually ref-counting?
3297 * State got messed up, follow the sites that change ->references
3298 * and try to make sense of it.
3299 */
3300 if (DEBUG_LOCKS_WARN_ON(!hlock->nest_lock))
3301 return 0;
3302
3303 if (hlock->class_idx == class - lock_classes + 1)
3304 return 1;
3305 }
3306
3307 return 0;
3308 }
3309
3310 static int
__lock_set_class(struct lockdep_map * lock,const char * name,struct lock_class_key * key,unsigned int subclass,unsigned long ip)3311 __lock_set_class(struct lockdep_map *lock, const char *name,
3312 struct lock_class_key *key, unsigned int subclass,
3313 unsigned long ip)
3314 {
3315 struct task_struct *curr = current;
3316 struct held_lock *hlock, *prev_hlock;
3317 struct lock_class *class;
3318 unsigned int depth;
3319 int i;
3320
3321 if (unlikely(!debug_locks))
3322 return 0;
3323
3324 depth = curr->lockdep_depth;
3325 /*
3326 * This function is about (re)setting the class of a held lock,
3327 * yet we're not actually holding any locks. Naughty user!
3328 */
3329 if (DEBUG_LOCKS_WARN_ON(!depth))
3330 return 0;
3331
3332 prev_hlock = NULL;
3333 for (i = depth-1; i >= 0; i--) {
3334 hlock = curr->held_locks + i;
3335 /*
3336 * We must not cross into another context:
3337 */
3338 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3339 break;
3340 if (match_held_lock(hlock, lock))
3341 goto found_it;
3342 prev_hlock = hlock;
3343 }
3344 return print_unlock_imbalance_bug(curr, lock, ip);
3345
3346 found_it:
3347 lockdep_init_map(lock, name, key, 0);
3348 class = register_lock_class(lock, subclass, 0);
3349 hlock->class_idx = class - lock_classes + 1;
3350
3351 curr->lockdep_depth = i;
3352 curr->curr_chain_key = hlock->prev_chain_key;
3353
3354 for (; i < depth; i++) {
3355 hlock = curr->held_locks + i;
3356 if (!__lock_acquire(hlock->instance,
3357 hlock_class(hlock)->subclass, hlock->trylock,
3358 hlock->read, hlock->check, hlock->hardirqs_off,
3359 hlock->nest_lock, hlock->acquire_ip,
3360 hlock->references, hlock->pin_count))
3361 return 0;
3362 }
3363
3364 /*
3365 * I took it apart and put it back together again, except now I have
3366 * these 'spare' parts.. where shall I put them.
3367 */
3368 if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth))
3369 return 0;
3370 return 1;
3371 }
3372
3373 /*
3374 * Remove the lock to the list of currently held locks - this gets
3375 * called on mutex_unlock()/spin_unlock*() (or on a failed
3376 * mutex_lock_interruptible()).
3377 *
3378 * @nested is an hysterical artifact, needs a tree wide cleanup.
3379 */
3380 static int
__lock_release(struct lockdep_map * lock,int nested,unsigned long ip)3381 __lock_release(struct lockdep_map *lock, int nested, unsigned long ip)
3382 {
3383 struct task_struct *curr = current;
3384 struct held_lock *hlock, *prev_hlock;
3385 unsigned int depth;
3386 int i;
3387
3388 if (unlikely(!debug_locks))
3389 return 0;
3390
3391 depth = curr->lockdep_depth;
3392 /*
3393 * So we're all set to release this lock.. wait what lock? We don't
3394 * own any locks, you've been drinking again?
3395 */
3396 if (DEBUG_LOCKS_WARN_ON(depth <= 0))
3397 return print_unlock_imbalance_bug(curr, lock, ip);
3398
3399 /*
3400 * Check whether the lock exists in the current stack
3401 * of held locks:
3402 */
3403 prev_hlock = NULL;
3404 for (i = depth-1; i >= 0; i--) {
3405 hlock = curr->held_locks + i;
3406 /*
3407 * We must not cross into another context:
3408 */
3409 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3410 break;
3411 if (match_held_lock(hlock, lock))
3412 goto found_it;
3413 prev_hlock = hlock;
3414 }
3415 return print_unlock_imbalance_bug(curr, lock, ip);
3416
3417 found_it:
3418 if (hlock->instance == lock)
3419 lock_release_holdtime(hlock);
3420
3421 WARN(hlock->pin_count, "releasing a pinned lock\n");
3422
3423 if (hlock->references) {
3424 hlock->references--;
3425 if (hlock->references) {
3426 /*
3427 * We had, and after removing one, still have
3428 * references, the current lock stack is still
3429 * valid. We're done!
3430 */
3431 return 1;
3432 }
3433 }
3434
3435 /*
3436 * We have the right lock to unlock, 'hlock' points to it.
3437 * Now we remove it from the stack, and add back the other
3438 * entries (if any), recalculating the hash along the way:
3439 */
3440
3441 curr->lockdep_depth = i;
3442 curr->curr_chain_key = hlock->prev_chain_key;
3443
3444 for (i++; i < depth; i++) {
3445 hlock = curr->held_locks + i;
3446 if (!__lock_acquire(hlock->instance,
3447 hlock_class(hlock)->subclass, hlock->trylock,
3448 hlock->read, hlock->check, hlock->hardirqs_off,
3449 hlock->nest_lock, hlock->acquire_ip,
3450 hlock->references, hlock->pin_count))
3451 return 0;
3452 }
3453
3454 /*
3455 * We had N bottles of beer on the wall, we drank one, but now
3456 * there's not N-1 bottles of beer left on the wall...
3457 */
3458 if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - 1))
3459 return 0;
3460
3461 return 1;
3462 }
3463
__lock_is_held(struct lockdep_map * lock)3464 static int __lock_is_held(struct lockdep_map *lock)
3465 {
3466 struct task_struct *curr = current;
3467 int i;
3468
3469 for (i = 0; i < curr->lockdep_depth; i++) {
3470 struct held_lock *hlock = curr->held_locks + i;
3471
3472 if (match_held_lock(hlock, lock))
3473 return 1;
3474 }
3475
3476 return 0;
3477 }
3478
__lock_pin_lock(struct lockdep_map * lock)3479 static void __lock_pin_lock(struct lockdep_map *lock)
3480 {
3481 struct task_struct *curr = current;
3482 int i;
3483
3484 if (unlikely(!debug_locks))
3485 return;
3486
3487 for (i = 0; i < curr->lockdep_depth; i++) {
3488 struct held_lock *hlock = curr->held_locks + i;
3489
3490 if (match_held_lock(hlock, lock)) {
3491 hlock->pin_count++;
3492 return;
3493 }
3494 }
3495
3496 WARN(1, "pinning an unheld lock\n");
3497 }
3498
__lock_unpin_lock(struct lockdep_map * lock)3499 static void __lock_unpin_lock(struct lockdep_map *lock)
3500 {
3501 struct task_struct *curr = current;
3502 int i;
3503
3504 if (unlikely(!debug_locks))
3505 return;
3506
3507 for (i = 0; i < curr->lockdep_depth; i++) {
3508 struct held_lock *hlock = curr->held_locks + i;
3509
3510 if (match_held_lock(hlock, lock)) {
3511 if (WARN(!hlock->pin_count, "unpinning an unpinned lock\n"))
3512 return;
3513
3514 hlock->pin_count--;
3515 return;
3516 }
3517 }
3518
3519 WARN(1, "unpinning an unheld lock\n");
3520 }
3521
3522 /*
3523 * Check whether we follow the irq-flags state precisely:
3524 */
check_flags(unsigned long flags)3525 static void check_flags(unsigned long flags)
3526 {
3527 #if defined(CONFIG_PROVE_LOCKING) && defined(CONFIG_DEBUG_LOCKDEP) && \
3528 defined(CONFIG_TRACE_IRQFLAGS)
3529 if (!debug_locks)
3530 return;
3531
3532 if (irqs_disabled_flags(flags)) {
3533 if (DEBUG_LOCKS_WARN_ON(current->hardirqs_enabled)) {
3534 printk("possible reason: unannotated irqs-off.\n");
3535 }
3536 } else {
3537 if (DEBUG_LOCKS_WARN_ON(!current->hardirqs_enabled)) {
3538 printk("possible reason: unannotated irqs-on.\n");
3539 }
3540 }
3541
3542 /*
3543 * We dont accurately track softirq state in e.g.
3544 * hardirq contexts (such as on 4KSTACKS), so only
3545 * check if not in hardirq contexts:
3546 */
3547 if (!hardirq_count()) {
3548 if (softirq_count()) {
3549 /* like the above, but with softirqs */
3550 DEBUG_LOCKS_WARN_ON(current->softirqs_enabled);
3551 } else {
3552 /* lick the above, does it taste good? */
3553 DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled);
3554 }
3555 }
3556
3557 if (!debug_locks)
3558 print_irqtrace_events(current);
3559 #endif
3560 }
3561
lock_set_class(struct lockdep_map * lock,const char * name,struct lock_class_key * key,unsigned int subclass,unsigned long ip)3562 void lock_set_class(struct lockdep_map *lock, const char *name,
3563 struct lock_class_key *key, unsigned int subclass,
3564 unsigned long ip)
3565 {
3566 unsigned long flags;
3567
3568 if (unlikely(current->lockdep_recursion))
3569 return;
3570
3571 raw_local_irq_save(flags);
3572 current->lockdep_recursion = 1;
3573 check_flags(flags);
3574 if (__lock_set_class(lock, name, key, subclass, ip))
3575 check_chain_key(current);
3576 current->lockdep_recursion = 0;
3577 raw_local_irq_restore(flags);
3578 }
3579 EXPORT_SYMBOL_GPL(lock_set_class);
3580
3581 /*
3582 * We are not always called with irqs disabled - do that here,
3583 * and also avoid lockdep recursion:
3584 */
lock_acquire(struct lockdep_map * lock,unsigned int subclass,int trylock,int read,int check,struct lockdep_map * nest_lock,unsigned long ip)3585 void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
3586 int trylock, int read, int check,
3587 struct lockdep_map *nest_lock, unsigned long ip)
3588 {
3589 unsigned long flags;
3590
3591 if (unlikely(current->lockdep_recursion))
3592 return;
3593
3594 raw_local_irq_save(flags);
3595 check_flags(flags);
3596
3597 current->lockdep_recursion = 1;
3598 trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip);
3599 __lock_acquire(lock, subclass, trylock, read, check,
3600 irqs_disabled_flags(flags), nest_lock, ip, 0, 0);
3601 current->lockdep_recursion = 0;
3602 raw_local_irq_restore(flags);
3603 }
3604 EXPORT_SYMBOL_GPL(lock_acquire);
3605
lock_release(struct lockdep_map * lock,int nested,unsigned long ip)3606 void lock_release(struct lockdep_map *lock, int nested,
3607 unsigned long ip)
3608 {
3609 unsigned long flags;
3610
3611 if (unlikely(current->lockdep_recursion))
3612 return;
3613
3614 raw_local_irq_save(flags);
3615 check_flags(flags);
3616 current->lockdep_recursion = 1;
3617 trace_lock_release(lock, ip);
3618 if (__lock_release(lock, nested, ip))
3619 check_chain_key(current);
3620 current->lockdep_recursion = 0;
3621 raw_local_irq_restore(flags);
3622 }
3623 EXPORT_SYMBOL_GPL(lock_release);
3624
lock_is_held(struct lockdep_map * lock)3625 int lock_is_held(struct lockdep_map *lock)
3626 {
3627 unsigned long flags;
3628 int ret = 0;
3629
3630 if (unlikely(current->lockdep_recursion))
3631 return 1; /* avoid false negative lockdep_assert_held() */
3632
3633 raw_local_irq_save(flags);
3634 check_flags(flags);
3635
3636 current->lockdep_recursion = 1;
3637 ret = __lock_is_held(lock);
3638 current->lockdep_recursion = 0;
3639 raw_local_irq_restore(flags);
3640
3641 return ret;
3642 }
3643 EXPORT_SYMBOL_GPL(lock_is_held);
3644
lock_pin_lock(struct lockdep_map * lock)3645 void lock_pin_lock(struct lockdep_map *lock)
3646 {
3647 unsigned long flags;
3648
3649 if (unlikely(current->lockdep_recursion))
3650 return;
3651
3652 raw_local_irq_save(flags);
3653 check_flags(flags);
3654
3655 current->lockdep_recursion = 1;
3656 __lock_pin_lock(lock);
3657 current->lockdep_recursion = 0;
3658 raw_local_irq_restore(flags);
3659 }
3660 EXPORT_SYMBOL_GPL(lock_pin_lock);
3661
lock_unpin_lock(struct lockdep_map * lock)3662 void lock_unpin_lock(struct lockdep_map *lock)
3663 {
3664 unsigned long flags;
3665
3666 if (unlikely(current->lockdep_recursion))
3667 return;
3668
3669 raw_local_irq_save(flags);
3670 check_flags(flags);
3671
3672 current->lockdep_recursion = 1;
3673 __lock_unpin_lock(lock);
3674 current->lockdep_recursion = 0;
3675 raw_local_irq_restore(flags);
3676 }
3677 EXPORT_SYMBOL_GPL(lock_unpin_lock);
3678
lockdep_set_current_reclaim_state(gfp_t gfp_mask)3679 void lockdep_set_current_reclaim_state(gfp_t gfp_mask)
3680 {
3681 current->lockdep_reclaim_gfp = gfp_mask;
3682 }
3683
lockdep_clear_current_reclaim_state(void)3684 void lockdep_clear_current_reclaim_state(void)
3685 {
3686 current->lockdep_reclaim_gfp = 0;
3687 }
3688
3689 #ifdef CONFIG_LOCK_STAT
3690 static int
print_lock_contention_bug(struct task_struct * curr,struct lockdep_map * lock,unsigned long ip)3691 print_lock_contention_bug(struct task_struct *curr, struct lockdep_map *lock,
3692 unsigned long ip)
3693 {
3694 if (!debug_locks_off())
3695 return 0;
3696 if (debug_locks_silent)
3697 return 0;
3698
3699 printk("\n");
3700 printk("=================================\n");
3701 printk("[ BUG: bad contention detected! ]\n");
3702 print_kernel_ident();
3703 printk("---------------------------------\n");
3704 printk("%s/%d is trying to contend lock (",
3705 curr->comm, task_pid_nr(curr));
3706 print_lockdep_cache(lock);
3707 printk(") at:\n");
3708 print_ip_sym(ip);
3709 printk("but there are no locks held!\n");
3710 printk("\nother info that might help us debug this:\n");
3711 lockdep_print_held_locks(curr);
3712
3713 printk("\nstack backtrace:\n");
3714 dump_stack();
3715
3716 return 0;
3717 }
3718
3719 static void
__lock_contended(struct lockdep_map * lock,unsigned long ip)3720 __lock_contended(struct lockdep_map *lock, unsigned long ip)
3721 {
3722 struct task_struct *curr = current;
3723 struct held_lock *hlock, *prev_hlock;
3724 struct lock_class_stats *stats;
3725 unsigned int depth;
3726 int i, contention_point, contending_point;
3727
3728 depth = curr->lockdep_depth;
3729 /*
3730 * Whee, we contended on this lock, except it seems we're not
3731 * actually trying to acquire anything much at all..
3732 */
3733 if (DEBUG_LOCKS_WARN_ON(!depth))
3734 return;
3735
3736 prev_hlock = NULL;
3737 for (i = depth-1; i >= 0; i--) {
3738 hlock = curr->held_locks + i;
3739 /*
3740 * We must not cross into another context:
3741 */
3742 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3743 break;
3744 if (match_held_lock(hlock, lock))
3745 goto found_it;
3746 prev_hlock = hlock;
3747 }
3748 print_lock_contention_bug(curr, lock, ip);
3749 return;
3750
3751 found_it:
3752 if (hlock->instance != lock)
3753 return;
3754
3755 hlock->waittime_stamp = lockstat_clock();
3756
3757 contention_point = lock_point(hlock_class(hlock)->contention_point, ip);
3758 contending_point = lock_point(hlock_class(hlock)->contending_point,
3759 lock->ip);
3760
3761 stats = get_lock_stats(hlock_class(hlock));
3762 if (contention_point < LOCKSTAT_POINTS)
3763 stats->contention_point[contention_point]++;
3764 if (contending_point < LOCKSTAT_POINTS)
3765 stats->contending_point[contending_point]++;
3766 if (lock->cpu != smp_processor_id())
3767 stats->bounces[bounce_contended + !!hlock->read]++;
3768 put_lock_stats(stats);
3769 }
3770
3771 static void
__lock_acquired(struct lockdep_map * lock,unsigned long ip)3772 __lock_acquired(struct lockdep_map *lock, unsigned long ip)
3773 {
3774 struct task_struct *curr = current;
3775 struct held_lock *hlock, *prev_hlock;
3776 struct lock_class_stats *stats;
3777 unsigned int depth;
3778 u64 now, waittime = 0;
3779 int i, cpu;
3780
3781 depth = curr->lockdep_depth;
3782 /*
3783 * Yay, we acquired ownership of this lock we didn't try to
3784 * acquire, how the heck did that happen?
3785 */
3786 if (DEBUG_LOCKS_WARN_ON(!depth))
3787 return;
3788
3789 prev_hlock = NULL;
3790 for (i = depth-1; i >= 0; i--) {
3791 hlock = curr->held_locks + i;
3792 /*
3793 * We must not cross into another context:
3794 */
3795 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3796 break;
3797 if (match_held_lock(hlock, lock))
3798 goto found_it;
3799 prev_hlock = hlock;
3800 }
3801 print_lock_contention_bug(curr, lock, _RET_IP_);
3802 return;
3803
3804 found_it:
3805 if (hlock->instance != lock)
3806 return;
3807
3808 cpu = smp_processor_id();
3809 if (hlock->waittime_stamp) {
3810 now = lockstat_clock();
3811 waittime = now - hlock->waittime_stamp;
3812 hlock->holdtime_stamp = now;
3813 }
3814
3815 trace_lock_acquired(lock, ip);
3816
3817 stats = get_lock_stats(hlock_class(hlock));
3818 if (waittime) {
3819 if (hlock->read)
3820 lock_time_inc(&stats->read_waittime, waittime);
3821 else
3822 lock_time_inc(&stats->write_waittime, waittime);
3823 }
3824 if (lock->cpu != cpu)
3825 stats->bounces[bounce_acquired + !!hlock->read]++;
3826 put_lock_stats(stats);
3827
3828 lock->cpu = cpu;
3829 lock->ip = ip;
3830 }
3831
lock_contended(struct lockdep_map * lock,unsigned long ip)3832 void lock_contended(struct lockdep_map *lock, unsigned long ip)
3833 {
3834 unsigned long flags;
3835
3836 if (unlikely(!lock_stat || !debug_locks))
3837 return;
3838
3839 if (unlikely(current->lockdep_recursion))
3840 return;
3841
3842 raw_local_irq_save(flags);
3843 check_flags(flags);
3844 current->lockdep_recursion = 1;
3845 trace_lock_contended(lock, ip);
3846 __lock_contended(lock, ip);
3847 current->lockdep_recursion = 0;
3848 raw_local_irq_restore(flags);
3849 }
3850 EXPORT_SYMBOL_GPL(lock_contended);
3851
lock_acquired(struct lockdep_map * lock,unsigned long ip)3852 void lock_acquired(struct lockdep_map *lock, unsigned long ip)
3853 {
3854 unsigned long flags;
3855
3856 if (unlikely(!lock_stat || !debug_locks))
3857 return;
3858
3859 if (unlikely(current->lockdep_recursion))
3860 return;
3861
3862 raw_local_irq_save(flags);
3863 check_flags(flags);
3864 current->lockdep_recursion = 1;
3865 __lock_acquired(lock, ip);
3866 current->lockdep_recursion = 0;
3867 raw_local_irq_restore(flags);
3868 }
3869 EXPORT_SYMBOL_GPL(lock_acquired);
3870 #endif
3871
3872 /*
3873 * Used by the testsuite, sanitize the validator state
3874 * after a simulated failure:
3875 */
3876
lockdep_reset(void)3877 void lockdep_reset(void)
3878 {
3879 unsigned long flags;
3880 int i;
3881
3882 raw_local_irq_save(flags);
3883 current->curr_chain_key = 0;
3884 current->lockdep_depth = 0;
3885 current->lockdep_recursion = 0;
3886 memset(current->held_locks, 0, MAX_LOCK_DEPTH*sizeof(struct held_lock));
3887 nr_hardirq_chains = 0;
3888 nr_softirq_chains = 0;
3889 nr_process_chains = 0;
3890 debug_locks = 1;
3891 for (i = 0; i < CHAINHASH_SIZE; i++)
3892 INIT_LIST_HEAD(chainhash_table + i);
3893 raw_local_irq_restore(flags);
3894 }
3895
zap_class(struct lock_class * class)3896 static void zap_class(struct lock_class *class)
3897 {
3898 int i;
3899
3900 /*
3901 * Remove all dependencies this lock is
3902 * involved in:
3903 */
3904 for (i = 0; i < nr_list_entries; i++) {
3905 if (list_entries[i].class == class)
3906 list_del_rcu(&list_entries[i].entry);
3907 }
3908 /*
3909 * Unhash the class and remove it from the all_lock_classes list:
3910 */
3911 list_del_rcu(&class->hash_entry);
3912 list_del_rcu(&class->lock_entry);
3913
3914 RCU_INIT_POINTER(class->key, NULL);
3915 RCU_INIT_POINTER(class->name, NULL);
3916 }
3917
within(const void * addr,void * start,unsigned long size)3918 static inline int within(const void *addr, void *start, unsigned long size)
3919 {
3920 return addr >= start && addr < start + size;
3921 }
3922
3923 /*
3924 * Used in module.c to remove lock classes from memory that is going to be
3925 * freed; and possibly re-used by other modules.
3926 *
3927 * We will have had one sync_sched() before getting here, so we're guaranteed
3928 * nobody will look up these exact classes -- they're properly dead but still
3929 * allocated.
3930 */
lockdep_free_key_range(void * start,unsigned long size)3931 void lockdep_free_key_range(void *start, unsigned long size)
3932 {
3933 struct lock_class *class;
3934 struct list_head *head;
3935 unsigned long flags;
3936 int i;
3937 int locked;
3938
3939 raw_local_irq_save(flags);
3940 locked = graph_lock();
3941
3942 /*
3943 * Unhash all classes that were created by this module:
3944 */
3945 for (i = 0; i < CLASSHASH_SIZE; i++) {
3946 head = classhash_table + i;
3947 if (list_empty(head))
3948 continue;
3949 list_for_each_entry_rcu(class, head, hash_entry) {
3950 if (within(class->key, start, size))
3951 zap_class(class);
3952 else if (within(class->name, start, size))
3953 zap_class(class);
3954 }
3955 }
3956
3957 if (locked)
3958 graph_unlock();
3959 raw_local_irq_restore(flags);
3960
3961 /*
3962 * Wait for any possible iterators from look_up_lock_class() to pass
3963 * before continuing to free the memory they refer to.
3964 *
3965 * sync_sched() is sufficient because the read-side is IRQ disable.
3966 */
3967 synchronize_sched();
3968
3969 /*
3970 * XXX at this point we could return the resources to the pool;
3971 * instead we leak them. We would need to change to bitmap allocators
3972 * instead of the linear allocators we have now.
3973 */
3974 }
3975
lockdep_reset_lock(struct lockdep_map * lock)3976 void lockdep_reset_lock(struct lockdep_map *lock)
3977 {
3978 struct lock_class *class;
3979 struct list_head *head;
3980 unsigned long flags;
3981 int i, j;
3982 int locked;
3983
3984 raw_local_irq_save(flags);
3985
3986 /*
3987 * Remove all classes this lock might have:
3988 */
3989 for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) {
3990 /*
3991 * If the class exists we look it up and zap it:
3992 */
3993 class = look_up_lock_class(lock, j);
3994 if (class)
3995 zap_class(class);
3996 }
3997 /*
3998 * Debug check: in the end all mapped classes should
3999 * be gone.
4000 */
4001 locked = graph_lock();
4002 for (i = 0; i < CLASSHASH_SIZE; i++) {
4003 head = classhash_table + i;
4004 if (list_empty(head))
4005 continue;
4006 list_for_each_entry_rcu(class, head, hash_entry) {
4007 int match = 0;
4008
4009 for (j = 0; j < NR_LOCKDEP_CACHING_CLASSES; j++)
4010 match |= class == lock->class_cache[j];
4011
4012 if (unlikely(match)) {
4013 if (debug_locks_off_graph_unlock()) {
4014 /*
4015 * We all just reset everything, how did it match?
4016 */
4017 WARN_ON(1);
4018 }
4019 goto out_restore;
4020 }
4021 }
4022 }
4023 if (locked)
4024 graph_unlock();
4025
4026 out_restore:
4027 raw_local_irq_restore(flags);
4028 }
4029
lockdep_init(void)4030 void lockdep_init(void)
4031 {
4032 int i;
4033
4034 /*
4035 * Some architectures have their own start_kernel()
4036 * code which calls lockdep_init(), while we also
4037 * call lockdep_init() from the start_kernel() itself,
4038 * and we want to initialize the hashes only once:
4039 */
4040 if (lockdep_initialized)
4041 return;
4042
4043 for (i = 0; i < CLASSHASH_SIZE; i++)
4044 INIT_LIST_HEAD(classhash_table + i);
4045
4046 for (i = 0; i < CHAINHASH_SIZE; i++)
4047 INIT_LIST_HEAD(chainhash_table + i);
4048
4049 lockdep_initialized = 1;
4050 }
4051
lockdep_info(void)4052 void __init lockdep_info(void)
4053 {
4054 printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");
4055
4056 printk("... MAX_LOCKDEP_SUBCLASSES: %lu\n", MAX_LOCKDEP_SUBCLASSES);
4057 printk("... MAX_LOCK_DEPTH: %lu\n", MAX_LOCK_DEPTH);
4058 printk("... MAX_LOCKDEP_KEYS: %lu\n", MAX_LOCKDEP_KEYS);
4059 printk("... CLASSHASH_SIZE: %lu\n", CLASSHASH_SIZE);
4060 printk("... MAX_LOCKDEP_ENTRIES: %lu\n", MAX_LOCKDEP_ENTRIES);
4061 printk("... MAX_LOCKDEP_CHAINS: %lu\n", MAX_LOCKDEP_CHAINS);
4062 printk("... CHAINHASH_SIZE: %lu\n", CHAINHASH_SIZE);
4063
4064 printk(" memory used by lock dependency info: %lu kB\n",
4065 (sizeof(struct lock_class) * MAX_LOCKDEP_KEYS +
4066 sizeof(struct list_head) * CLASSHASH_SIZE +
4067 sizeof(struct lock_list) * MAX_LOCKDEP_ENTRIES +
4068 sizeof(struct lock_chain) * MAX_LOCKDEP_CHAINS +
4069 sizeof(struct list_head) * CHAINHASH_SIZE
4070 #ifdef CONFIG_PROVE_LOCKING
4071 + sizeof(struct circular_queue)
4072 #endif
4073 ) / 1024
4074 );
4075
4076 printk(" per task-struct memory footprint: %lu bytes\n",
4077 sizeof(struct held_lock) * MAX_LOCK_DEPTH);
4078
4079 #ifdef CONFIG_DEBUG_LOCKDEP
4080 if (lockdep_init_error) {
4081 printk("WARNING: lockdep init error: lock '%s' was acquired before lockdep_init().\n", lock_init_error);
4082 printk("Call stack leading to lockdep invocation was:\n");
4083 print_stack_trace(&lockdep_init_trace, 0);
4084 }
4085 #endif
4086 }
4087
4088 static void
print_freed_lock_bug(struct task_struct * curr,const void * mem_from,const void * mem_to,struct held_lock * hlock)4089 print_freed_lock_bug(struct task_struct *curr, const void *mem_from,
4090 const void *mem_to, struct held_lock *hlock)
4091 {
4092 if (!debug_locks_off())
4093 return;
4094 if (debug_locks_silent)
4095 return;
4096
4097 printk("\n");
4098 printk("=========================\n");
4099 printk("[ BUG: held lock freed! ]\n");
4100 print_kernel_ident();
4101 printk("-------------------------\n");
4102 printk("%s/%d is freeing memory %p-%p, with a lock still held there!\n",
4103 curr->comm, task_pid_nr(curr), mem_from, mem_to-1);
4104 print_lock(hlock);
4105 lockdep_print_held_locks(curr);
4106
4107 printk("\nstack backtrace:\n");
4108 dump_stack();
4109 }
4110
not_in_range(const void * mem_from,unsigned long mem_len,const void * lock_from,unsigned long lock_len)4111 static inline int not_in_range(const void* mem_from, unsigned long mem_len,
4112 const void* lock_from, unsigned long lock_len)
4113 {
4114 return lock_from + lock_len <= mem_from ||
4115 mem_from + mem_len <= lock_from;
4116 }
4117
4118 /*
4119 * Called when kernel memory is freed (or unmapped), or if a lock
4120 * is destroyed or reinitialized - this code checks whether there is
4121 * any held lock in the memory range of <from> to <to>:
4122 */
debug_check_no_locks_freed(const void * mem_from,unsigned long mem_len)4123 void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len)
4124 {
4125 struct task_struct *curr = current;
4126 struct held_lock *hlock;
4127 unsigned long flags;
4128 int i;
4129
4130 if (unlikely(!debug_locks))
4131 return;
4132
4133 raw_local_irq_save(flags);
4134 for (i = 0; i < curr->lockdep_depth; i++) {
4135 hlock = curr->held_locks + i;
4136
4137 if (not_in_range(mem_from, mem_len, hlock->instance,
4138 sizeof(*hlock->instance)))
4139 continue;
4140
4141 print_freed_lock_bug(curr, mem_from, mem_from + mem_len, hlock);
4142 break;
4143 }
4144 raw_local_irq_restore(flags);
4145 }
4146 EXPORT_SYMBOL_GPL(debug_check_no_locks_freed);
4147
print_held_locks_bug(void)4148 static void print_held_locks_bug(void)
4149 {
4150 if (!debug_locks_off())
4151 return;
4152 if (debug_locks_silent)
4153 return;
4154
4155 printk("\n");
4156 printk("=====================================\n");
4157 printk("[ BUG: %s/%d still has locks held! ]\n",
4158 current->comm, task_pid_nr(current));
4159 print_kernel_ident();
4160 printk("-------------------------------------\n");
4161 lockdep_print_held_locks(current);
4162 printk("\nstack backtrace:\n");
4163 dump_stack();
4164 }
4165
debug_check_no_locks_held(void)4166 void debug_check_no_locks_held(void)
4167 {
4168 if (unlikely(current->lockdep_depth > 0))
4169 print_held_locks_bug();
4170 }
4171 EXPORT_SYMBOL_GPL(debug_check_no_locks_held);
4172
4173 #ifdef __KERNEL__
debug_show_all_locks(void)4174 void debug_show_all_locks(void)
4175 {
4176 struct task_struct *g, *p;
4177 int count = 10;
4178 int unlock = 1;
4179
4180 if (unlikely(!debug_locks)) {
4181 printk("INFO: lockdep is turned off.\n");
4182 return;
4183 }
4184 printk("\nShowing all locks held in the system:\n");
4185
4186 /*
4187 * Here we try to get the tasklist_lock as hard as possible,
4188 * if not successful after 2 seconds we ignore it (but keep
4189 * trying). This is to enable a debug printout even if a
4190 * tasklist_lock-holding task deadlocks or crashes.
4191 */
4192 retry:
4193 if (!read_trylock(&tasklist_lock)) {
4194 if (count == 10)
4195 printk("hm, tasklist_lock locked, retrying... ");
4196 if (count) {
4197 count--;
4198 printk(" #%d", 10-count);
4199 mdelay(200);
4200 goto retry;
4201 }
4202 printk(" ignoring it.\n");
4203 unlock = 0;
4204 } else {
4205 if (count != 10)
4206 printk(KERN_CONT " locked it.\n");
4207 }
4208
4209 do_each_thread(g, p) {
4210 /*
4211 * It's not reliable to print a task's held locks
4212 * if it's not sleeping (or if it's not the current
4213 * task):
4214 */
4215 if (p->state == TASK_RUNNING && p != current)
4216 continue;
4217 if (p->lockdep_depth)
4218 lockdep_print_held_locks(p);
4219 if (!unlock)
4220 if (read_trylock(&tasklist_lock))
4221 unlock = 1;
4222 } while_each_thread(g, p);
4223
4224 printk("\n");
4225 printk("=============================================\n\n");
4226
4227 if (unlock)
4228 read_unlock(&tasklist_lock);
4229 }
4230 EXPORT_SYMBOL_GPL(debug_show_all_locks);
4231 #endif
4232
4233 /*
4234 * Careful: only use this function if you are sure that
4235 * the task cannot run in parallel!
4236 */
debug_show_held_locks(struct task_struct * task)4237 void debug_show_held_locks(struct task_struct *task)
4238 {
4239 if (unlikely(!debug_locks)) {
4240 printk("INFO: lockdep is turned off.\n");
4241 return;
4242 }
4243 lockdep_print_held_locks(task);
4244 }
4245 EXPORT_SYMBOL_GPL(debug_show_held_locks);
4246
lockdep_sys_exit(void)4247 asmlinkage __visible void lockdep_sys_exit(void)
4248 {
4249 struct task_struct *curr = current;
4250
4251 if (unlikely(curr->lockdep_depth)) {
4252 if (!debug_locks_off())
4253 return;
4254 printk("\n");
4255 printk("================================================\n");
4256 printk("[ BUG: lock held when returning to user space! ]\n");
4257 print_kernel_ident();
4258 printk("------------------------------------------------\n");
4259 printk("%s/%d is leaving the kernel with locks still held!\n",
4260 curr->comm, curr->pid);
4261 lockdep_print_held_locks(curr);
4262 }
4263 }
4264
lockdep_rcu_suspicious(const char * file,const int line,const char * s)4265 void lockdep_rcu_suspicious(const char *file, const int line, const char *s)
4266 {
4267 struct task_struct *curr = current;
4268
4269 #ifndef CONFIG_PROVE_RCU_REPEATEDLY
4270 if (!debug_locks_off())
4271 return;
4272 #endif /* #ifdef CONFIG_PROVE_RCU_REPEATEDLY */
4273 /* Note: the following can be executed concurrently, so be careful. */
4274 printk("\n");
4275 printk("===============================\n");
4276 printk("[ INFO: suspicious RCU usage. ]\n");
4277 print_kernel_ident();
4278 printk("-------------------------------\n");
4279 printk("%s:%d %s!\n", file, line, s);
4280 printk("\nother info that might help us debug this:\n\n");
4281 printk("\n%srcu_scheduler_active = %d, debug_locks = %d\n",
4282 !rcu_lockdep_current_cpu_online()
4283 ? "RCU used illegally from offline CPU!\n"
4284 : !rcu_is_watching()
4285 ? "RCU used illegally from idle CPU!\n"
4286 : "",
4287 rcu_scheduler_active, debug_locks);
4288
4289 /*
4290 * If a CPU is in the RCU-free window in idle (ie: in the section
4291 * between rcu_idle_enter() and rcu_idle_exit(), then RCU
4292 * considers that CPU to be in an "extended quiescent state",
4293 * which means that RCU will be completely ignoring that CPU.
4294 * Therefore, rcu_read_lock() and friends have absolutely no
4295 * effect on a CPU running in that state. In other words, even if
4296 * such an RCU-idle CPU has called rcu_read_lock(), RCU might well
4297 * delete data structures out from under it. RCU really has no
4298 * choice here: we need to keep an RCU-free window in idle where
4299 * the CPU may possibly enter into low power mode. This way we can
4300 * notice an extended quiescent state to other CPUs that started a grace
4301 * period. Otherwise we would delay any grace period as long as we run
4302 * in the idle task.
4303 *
4304 * So complain bitterly if someone does call rcu_read_lock(),
4305 * rcu_read_lock_bh() and so on from extended quiescent states.
4306 */
4307 if (!rcu_is_watching())
4308 printk("RCU used illegally from extended quiescent state!\n");
4309
4310 lockdep_print_held_locks(curr);
4311 printk("\nstack backtrace:\n");
4312 dump_stack();
4313 }
4314 EXPORT_SYMBOL_GPL(lockdep_rcu_suspicious);
4315