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Root/kernel/lockdep.c

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

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