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