xref: /openbmc/linux/kernel/locking/lockdep_proc.c (revision 35267cea)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * kernel/lockdep_proc.c
4  *
5  * Runtime locking correctness validator
6  *
7  * Started by Ingo Molnar:
8  *
9  *  Copyright (C) 2006,2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
10  *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
11  *
12  * Code for /proc/lockdep and /proc/lockdep_stats:
13  *
14  */
15 #include <linux/export.h>
16 #include <linux/proc_fs.h>
17 #include <linux/seq_file.h>
18 #include <linux/kallsyms.h>
19 #include <linux/debug_locks.h>
20 #include <linux/vmalloc.h>
21 #include <linux/sort.h>
22 #include <linux/uaccess.h>
23 #include <asm/div64.h>
24 
25 #include "lockdep_internals.h"
26 
27 static void *l_next(struct seq_file *m, void *v, loff_t *pos)
28 {
29 	return seq_list_next(v, &all_lock_classes, pos);
30 }
31 
32 static void *l_start(struct seq_file *m, loff_t *pos)
33 {
34 	return seq_list_start_head(&all_lock_classes, *pos);
35 }
36 
37 static void l_stop(struct seq_file *m, void *v)
38 {
39 }
40 
41 static void print_name(struct seq_file *m, struct lock_class *class)
42 {
43 	char str[KSYM_NAME_LEN];
44 	const char *name = class->name;
45 
46 	if (!name) {
47 		name = __get_key_name(class->key, str);
48 		seq_printf(m, "%s", name);
49 	} else{
50 		seq_printf(m, "%s", name);
51 		if (class->name_version > 1)
52 			seq_printf(m, "#%d", class->name_version);
53 		if (class->subclass)
54 			seq_printf(m, "/%d", class->subclass);
55 	}
56 }
57 
58 static int l_show(struct seq_file *m, void *v)
59 {
60 	struct lock_class *class = list_entry(v, struct lock_class, lock_entry);
61 	struct lock_list *entry;
62 	char usage[LOCK_USAGE_CHARS];
63 
64 	if (v == &all_lock_classes) {
65 		seq_printf(m, "all lock classes:\n");
66 		return 0;
67 	}
68 
69 	seq_printf(m, "%p", class->key);
70 #ifdef CONFIG_DEBUG_LOCKDEP
71 	seq_printf(m, " OPS:%8ld", debug_class_ops_read(class));
72 #endif
73 	if (IS_ENABLED(CONFIG_PROVE_LOCKING)) {
74 		seq_printf(m, " FD:%5ld", lockdep_count_forward_deps(class));
75 		seq_printf(m, " BD:%5ld", lockdep_count_backward_deps(class));
76 
77 		get_usage_chars(class, usage);
78 		seq_printf(m, " %s", usage);
79 	}
80 
81 	seq_printf(m, ": ");
82 	print_name(m, class);
83 	seq_puts(m, "\n");
84 
85 	if (IS_ENABLED(CONFIG_PROVE_LOCKING)) {
86 		list_for_each_entry(entry, &class->locks_after, entry) {
87 			if (entry->distance == 1) {
88 				seq_printf(m, " -> [%p] ", entry->class->key);
89 				print_name(m, entry->class);
90 				seq_puts(m, "\n");
91 			}
92 		}
93 		seq_puts(m, "\n");
94 	}
95 
96 	return 0;
97 }
98 
99 static const struct seq_operations lockdep_ops = {
100 	.start	= l_start,
101 	.next	= l_next,
102 	.stop	= l_stop,
103 	.show	= l_show,
104 };
105 
106 #ifdef CONFIG_PROVE_LOCKING
107 static void *lc_start(struct seq_file *m, loff_t *pos)
108 {
109 	if (*pos < 0)
110 		return NULL;
111 
112 	if (*pos == 0)
113 		return SEQ_START_TOKEN;
114 
115 	return lock_chains + (*pos - 1);
116 }
117 
118 static void *lc_next(struct seq_file *m, void *v, loff_t *pos)
119 {
120 	*pos = lockdep_next_lockchain(*pos - 1) + 1;
121 	return lc_start(m, pos);
122 }
123 
124 static void lc_stop(struct seq_file *m, void *v)
125 {
126 }
127 
128 static int lc_show(struct seq_file *m, void *v)
129 {
130 	struct lock_chain *chain = v;
131 	struct lock_class *class;
132 	int i;
133 	static const char * const irq_strs[] = {
134 		[0]			     = "0",
135 		[LOCK_CHAIN_HARDIRQ_CONTEXT] = "hardirq",
136 		[LOCK_CHAIN_SOFTIRQ_CONTEXT] = "softirq",
137 		[LOCK_CHAIN_SOFTIRQ_CONTEXT|
138 		 LOCK_CHAIN_HARDIRQ_CONTEXT] = "hardirq|softirq",
139 	};
140 
141 	if (v == SEQ_START_TOKEN) {
142 		if (!nr_free_chain_hlocks)
143 			seq_printf(m, "(buggered) ");
144 		seq_printf(m, "all lock chains:\n");
145 		return 0;
146 	}
147 
148 	seq_printf(m, "irq_context: %s\n", irq_strs[chain->irq_context]);
149 
150 	for (i = 0; i < chain->depth; i++) {
151 		class = lock_chain_get_class(chain, i);
152 		if (!class->key)
153 			continue;
154 
155 		seq_printf(m, "[%p] ", class->key);
156 		print_name(m, class);
157 		seq_puts(m, "\n");
158 	}
159 	seq_puts(m, "\n");
160 
161 	return 0;
162 }
163 
164 static const struct seq_operations lockdep_chains_ops = {
165 	.start	= lc_start,
166 	.next	= lc_next,
167 	.stop	= lc_stop,
168 	.show	= lc_show,
169 };
170 #endif /* CONFIG_PROVE_LOCKING */
171 
172 static void lockdep_stats_debug_show(struct seq_file *m)
173 {
174 #ifdef CONFIG_DEBUG_LOCKDEP
175 	unsigned long long hi1 = debug_atomic_read(hardirqs_on_events),
176 			   hi2 = debug_atomic_read(hardirqs_off_events),
177 			   hr1 = debug_atomic_read(redundant_hardirqs_on),
178 			   hr2 = debug_atomic_read(redundant_hardirqs_off),
179 			   si1 = debug_atomic_read(softirqs_on_events),
180 			   si2 = debug_atomic_read(softirqs_off_events),
181 			   sr1 = debug_atomic_read(redundant_softirqs_on),
182 			   sr2 = debug_atomic_read(redundant_softirqs_off);
183 
184 	seq_printf(m, " chain lookup misses:           %11llu\n",
185 		debug_atomic_read(chain_lookup_misses));
186 	seq_printf(m, " chain lookup hits:             %11llu\n",
187 		debug_atomic_read(chain_lookup_hits));
188 	seq_printf(m, " cyclic checks:                 %11llu\n",
189 		debug_atomic_read(nr_cyclic_checks));
190 	seq_printf(m, " redundant checks:              %11llu\n",
191 		debug_atomic_read(nr_redundant_checks));
192 	seq_printf(m, " redundant links:               %11llu\n",
193 		debug_atomic_read(nr_redundant));
194 	seq_printf(m, " find-mask forwards checks:     %11llu\n",
195 		debug_atomic_read(nr_find_usage_forwards_checks));
196 	seq_printf(m, " find-mask backwards checks:    %11llu\n",
197 		debug_atomic_read(nr_find_usage_backwards_checks));
198 
199 	seq_printf(m, " hardirq on events:             %11llu\n", hi1);
200 	seq_printf(m, " hardirq off events:            %11llu\n", hi2);
201 	seq_printf(m, " redundant hardirq ons:         %11llu\n", hr1);
202 	seq_printf(m, " redundant hardirq offs:        %11llu\n", hr2);
203 	seq_printf(m, " softirq on events:             %11llu\n", si1);
204 	seq_printf(m, " softirq off events:            %11llu\n", si2);
205 	seq_printf(m, " redundant softirq ons:         %11llu\n", sr1);
206 	seq_printf(m, " redundant softirq offs:        %11llu\n", sr2);
207 #endif
208 }
209 
210 static int lockdep_stats_show(struct seq_file *m, void *v)
211 {
212 	unsigned long nr_unused = 0, nr_uncategorized = 0,
213 		      nr_irq_safe = 0, nr_irq_unsafe = 0,
214 		      nr_softirq_safe = 0, nr_softirq_unsafe = 0,
215 		      nr_hardirq_safe = 0, nr_hardirq_unsafe = 0,
216 		      nr_irq_read_safe = 0, nr_irq_read_unsafe = 0,
217 		      nr_softirq_read_safe = 0, nr_softirq_read_unsafe = 0,
218 		      nr_hardirq_read_safe = 0, nr_hardirq_read_unsafe = 0,
219 		      sum_forward_deps = 0;
220 
221 #ifdef CONFIG_PROVE_LOCKING
222 	struct lock_class *class;
223 
224 	list_for_each_entry(class, &all_lock_classes, lock_entry) {
225 
226 		if (class->usage_mask == 0)
227 			nr_unused++;
228 		if (class->usage_mask == LOCKF_USED)
229 			nr_uncategorized++;
230 		if (class->usage_mask & LOCKF_USED_IN_IRQ)
231 			nr_irq_safe++;
232 		if (class->usage_mask & LOCKF_ENABLED_IRQ)
233 			nr_irq_unsafe++;
234 		if (class->usage_mask & LOCKF_USED_IN_SOFTIRQ)
235 			nr_softirq_safe++;
236 		if (class->usage_mask & LOCKF_ENABLED_SOFTIRQ)
237 			nr_softirq_unsafe++;
238 		if (class->usage_mask & LOCKF_USED_IN_HARDIRQ)
239 			nr_hardirq_safe++;
240 		if (class->usage_mask & LOCKF_ENABLED_HARDIRQ)
241 			nr_hardirq_unsafe++;
242 		if (class->usage_mask & LOCKF_USED_IN_IRQ_READ)
243 			nr_irq_read_safe++;
244 		if (class->usage_mask & LOCKF_ENABLED_IRQ_READ)
245 			nr_irq_read_unsafe++;
246 		if (class->usage_mask & LOCKF_USED_IN_SOFTIRQ_READ)
247 			nr_softirq_read_safe++;
248 		if (class->usage_mask & LOCKF_ENABLED_SOFTIRQ_READ)
249 			nr_softirq_read_unsafe++;
250 		if (class->usage_mask & LOCKF_USED_IN_HARDIRQ_READ)
251 			nr_hardirq_read_safe++;
252 		if (class->usage_mask & LOCKF_ENABLED_HARDIRQ_READ)
253 			nr_hardirq_read_unsafe++;
254 
255 		sum_forward_deps += lockdep_count_forward_deps(class);
256 	}
257 #ifdef CONFIG_DEBUG_LOCKDEP
258 	DEBUG_LOCKS_WARN_ON(debug_atomic_read(nr_unused_locks) != nr_unused);
259 #endif
260 
261 #endif
262 	seq_printf(m, " lock-classes:                  %11lu [max: %lu]\n",
263 			nr_lock_classes, MAX_LOCKDEP_KEYS);
264 	seq_printf(m, " direct dependencies:           %11lu [max: %lu]\n",
265 			nr_list_entries, MAX_LOCKDEP_ENTRIES);
266 	seq_printf(m, " indirect dependencies:         %11lu\n",
267 			sum_forward_deps);
268 
269 	/*
270 	 * Total number of dependencies:
271 	 *
272 	 * All irq-safe locks may nest inside irq-unsafe locks,
273 	 * plus all the other known dependencies:
274 	 */
275 	seq_printf(m, " all direct dependencies:       %11lu\n",
276 			nr_irq_unsafe * nr_irq_safe +
277 			nr_hardirq_unsafe * nr_hardirq_safe +
278 			nr_list_entries);
279 
280 #ifdef CONFIG_PROVE_LOCKING
281 	seq_printf(m, " dependency chains:             %11lu [max: %lu]\n",
282 			lock_chain_count(), MAX_LOCKDEP_CHAINS);
283 	seq_printf(m, " dependency chain hlocks used:  %11lu [max: %lu]\n",
284 			MAX_LOCKDEP_CHAIN_HLOCKS -
285 			(nr_free_chain_hlocks + nr_lost_chain_hlocks),
286 			MAX_LOCKDEP_CHAIN_HLOCKS);
287 	seq_printf(m, " dependency chain hlocks lost:  %11u\n",
288 			nr_lost_chain_hlocks);
289 #endif
290 
291 #ifdef CONFIG_TRACE_IRQFLAGS
292 	seq_printf(m, " in-hardirq chains:             %11u\n",
293 			nr_hardirq_chains);
294 	seq_printf(m, " in-softirq chains:             %11u\n",
295 			nr_softirq_chains);
296 #endif
297 	seq_printf(m, " in-process chains:             %11u\n",
298 			nr_process_chains);
299 	seq_printf(m, " stack-trace entries:           %11lu [max: %lu]\n",
300 			nr_stack_trace_entries, MAX_STACK_TRACE_ENTRIES);
301 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
302 	seq_printf(m, " number of stack traces:        %11llu\n",
303 		   lockdep_stack_trace_count());
304 	seq_printf(m, " number of stack hash chains:   %11llu\n",
305 		   lockdep_stack_hash_count());
306 #endif
307 	seq_printf(m, " combined max dependencies:     %11u\n",
308 			(nr_hardirq_chains + 1) *
309 			(nr_softirq_chains + 1) *
310 			(nr_process_chains + 1)
311 	);
312 	seq_printf(m, " hardirq-safe locks:            %11lu\n",
313 			nr_hardirq_safe);
314 	seq_printf(m, " hardirq-unsafe locks:          %11lu\n",
315 			nr_hardirq_unsafe);
316 	seq_printf(m, " softirq-safe locks:            %11lu\n",
317 			nr_softirq_safe);
318 	seq_printf(m, " softirq-unsafe locks:          %11lu\n",
319 			nr_softirq_unsafe);
320 	seq_printf(m, " irq-safe locks:                %11lu\n",
321 			nr_irq_safe);
322 	seq_printf(m, " irq-unsafe locks:              %11lu\n",
323 			nr_irq_unsafe);
324 
325 	seq_printf(m, " hardirq-read-safe locks:       %11lu\n",
326 			nr_hardirq_read_safe);
327 	seq_printf(m, " hardirq-read-unsafe locks:     %11lu\n",
328 			nr_hardirq_read_unsafe);
329 	seq_printf(m, " softirq-read-safe locks:       %11lu\n",
330 			nr_softirq_read_safe);
331 	seq_printf(m, " softirq-read-unsafe locks:     %11lu\n",
332 			nr_softirq_read_unsafe);
333 	seq_printf(m, " irq-read-safe locks:           %11lu\n",
334 			nr_irq_read_safe);
335 	seq_printf(m, " irq-read-unsafe locks:         %11lu\n",
336 			nr_irq_read_unsafe);
337 
338 	seq_printf(m, " uncategorized locks:           %11lu\n",
339 			nr_uncategorized);
340 	seq_printf(m, " unused locks:                  %11lu\n",
341 			nr_unused);
342 	seq_printf(m, " max locking depth:             %11u\n",
343 			max_lockdep_depth);
344 #ifdef CONFIG_PROVE_LOCKING
345 	seq_printf(m, " max bfs queue depth:           %11u\n",
346 			max_bfs_queue_depth);
347 #endif
348 	lockdep_stats_debug_show(m);
349 	seq_printf(m, " debug_locks:                   %11u\n",
350 			debug_locks);
351 
352 	/*
353 	 * Zapped classes and lockdep data buffers reuse statistics.
354 	 */
355 	seq_puts(m, "\n");
356 	seq_printf(m, " zapped classes:                %11lu\n",
357 			nr_zapped_classes);
358 #ifdef CONFIG_PROVE_LOCKING
359 	seq_printf(m, " zapped lock chains:            %11lu\n",
360 			nr_zapped_lock_chains);
361 	seq_printf(m, " large chain blocks:            %11u\n",
362 			nr_large_chain_blocks);
363 #endif
364 	return 0;
365 }
366 
367 #ifdef CONFIG_LOCK_STAT
368 
369 struct lock_stat_data {
370 	struct lock_class *class;
371 	struct lock_class_stats stats;
372 };
373 
374 struct lock_stat_seq {
375 	struct lock_stat_data *iter_end;
376 	struct lock_stat_data stats[MAX_LOCKDEP_KEYS];
377 };
378 
379 /*
380  * sort on absolute number of contentions
381  */
382 static int lock_stat_cmp(const void *l, const void *r)
383 {
384 	const struct lock_stat_data *dl = l, *dr = r;
385 	unsigned long nl, nr;
386 
387 	nl = dl->stats.read_waittime.nr + dl->stats.write_waittime.nr;
388 	nr = dr->stats.read_waittime.nr + dr->stats.write_waittime.nr;
389 
390 	return nr - nl;
391 }
392 
393 static void seq_line(struct seq_file *m, char c, int offset, int length)
394 {
395 	int i;
396 
397 	for (i = 0; i < offset; i++)
398 		seq_puts(m, " ");
399 	for (i = 0; i < length; i++)
400 		seq_printf(m, "%c", c);
401 	seq_puts(m, "\n");
402 }
403 
404 static void snprint_time(char *buf, size_t bufsiz, s64 nr)
405 {
406 	s64 div;
407 	s32 rem;
408 
409 	nr += 5; /* for display rounding */
410 	div = div_s64_rem(nr, 1000, &rem);
411 	snprintf(buf, bufsiz, "%lld.%02d", (long long)div, (int)rem/10);
412 }
413 
414 static void seq_time(struct seq_file *m, s64 time)
415 {
416 	char num[15];
417 
418 	snprint_time(num, sizeof(num), time);
419 	seq_printf(m, " %14s", num);
420 }
421 
422 static void seq_lock_time(struct seq_file *m, struct lock_time *lt)
423 {
424 	seq_printf(m, "%14lu", lt->nr);
425 	seq_time(m, lt->min);
426 	seq_time(m, lt->max);
427 	seq_time(m, lt->total);
428 	seq_time(m, lt->nr ? div64_u64(lt->total, lt->nr) : 0);
429 }
430 
431 static void seq_stats(struct seq_file *m, struct lock_stat_data *data)
432 {
433 	const struct lockdep_subclass_key *ckey;
434 	struct lock_class_stats *stats;
435 	struct lock_class *class;
436 	const char *cname;
437 	int i, namelen;
438 	char name[39];
439 
440 	class = data->class;
441 	stats = &data->stats;
442 
443 	namelen = 38;
444 	if (class->name_version > 1)
445 		namelen -= 2; /* XXX truncates versions > 9 */
446 	if (class->subclass)
447 		namelen -= 2;
448 
449 	rcu_read_lock_sched();
450 	cname = rcu_dereference_sched(class->name);
451 	ckey  = rcu_dereference_sched(class->key);
452 
453 	if (!cname && !ckey) {
454 		rcu_read_unlock_sched();
455 		return;
456 
457 	} else if (!cname) {
458 		char str[KSYM_NAME_LEN];
459 		const char *key_name;
460 
461 		key_name = __get_key_name(ckey, str);
462 		snprintf(name, namelen, "%s", key_name);
463 	} else {
464 		snprintf(name, namelen, "%s", cname);
465 	}
466 	rcu_read_unlock_sched();
467 
468 	namelen = strlen(name);
469 	if (class->name_version > 1) {
470 		snprintf(name+namelen, 3, "#%d", class->name_version);
471 		namelen += 2;
472 	}
473 	if (class->subclass) {
474 		snprintf(name+namelen, 3, "/%d", class->subclass);
475 		namelen += 2;
476 	}
477 
478 	if (stats->write_holdtime.nr) {
479 		if (stats->read_holdtime.nr)
480 			seq_printf(m, "%38s-W:", name);
481 		else
482 			seq_printf(m, "%40s:", name);
483 
484 		seq_printf(m, "%14lu ", stats->bounces[bounce_contended_write]);
485 		seq_lock_time(m, &stats->write_waittime);
486 		seq_printf(m, " %14lu ", stats->bounces[bounce_acquired_write]);
487 		seq_lock_time(m, &stats->write_holdtime);
488 		seq_puts(m, "\n");
489 	}
490 
491 	if (stats->read_holdtime.nr) {
492 		seq_printf(m, "%38s-R:", name);
493 		seq_printf(m, "%14lu ", stats->bounces[bounce_contended_read]);
494 		seq_lock_time(m, &stats->read_waittime);
495 		seq_printf(m, " %14lu ", stats->bounces[bounce_acquired_read]);
496 		seq_lock_time(m, &stats->read_holdtime);
497 		seq_puts(m, "\n");
498 	}
499 
500 	if (stats->read_waittime.nr + stats->write_waittime.nr == 0)
501 		return;
502 
503 	if (stats->read_holdtime.nr)
504 		namelen += 2;
505 
506 	for (i = 0; i < LOCKSTAT_POINTS; i++) {
507 		char ip[32];
508 
509 		if (class->contention_point[i] == 0)
510 			break;
511 
512 		if (!i)
513 			seq_line(m, '-', 40-namelen, namelen);
514 
515 		snprintf(ip, sizeof(ip), "[<%p>]",
516 				(void *)class->contention_point[i]);
517 		seq_printf(m, "%40s %14lu %29s %pS\n",
518 			   name, stats->contention_point[i],
519 			   ip, (void *)class->contention_point[i]);
520 	}
521 	for (i = 0; i < LOCKSTAT_POINTS; i++) {
522 		char ip[32];
523 
524 		if (class->contending_point[i] == 0)
525 			break;
526 
527 		if (!i)
528 			seq_line(m, '-', 40-namelen, namelen);
529 
530 		snprintf(ip, sizeof(ip), "[<%p>]",
531 				(void *)class->contending_point[i]);
532 		seq_printf(m, "%40s %14lu %29s %pS\n",
533 			   name, stats->contending_point[i],
534 			   ip, (void *)class->contending_point[i]);
535 	}
536 	if (i) {
537 		seq_puts(m, "\n");
538 		seq_line(m, '.', 0, 40 + 1 + 12 * (14 + 1));
539 		seq_puts(m, "\n");
540 	}
541 }
542 
543 static void seq_header(struct seq_file *m)
544 {
545 	seq_puts(m, "lock_stat version 0.4\n");
546 
547 	if (unlikely(!debug_locks))
548 		seq_printf(m, "*WARNING* lock debugging disabled!! - possibly due to a lockdep warning\n");
549 
550 	seq_line(m, '-', 0, 40 + 1 + 12 * (14 + 1));
551 	seq_printf(m, "%40s %14s %14s %14s %14s %14s %14s %14s %14s %14s %14s "
552 			"%14s %14s\n",
553 			"class name",
554 			"con-bounces",
555 			"contentions",
556 			"waittime-min",
557 			"waittime-max",
558 			"waittime-total",
559 			"waittime-avg",
560 			"acq-bounces",
561 			"acquisitions",
562 			"holdtime-min",
563 			"holdtime-max",
564 			"holdtime-total",
565 			"holdtime-avg");
566 	seq_line(m, '-', 0, 40 + 1 + 12 * (14 + 1));
567 	seq_printf(m, "\n");
568 }
569 
570 static void *ls_start(struct seq_file *m, loff_t *pos)
571 {
572 	struct lock_stat_seq *data = m->private;
573 	struct lock_stat_data *iter;
574 
575 	if (*pos == 0)
576 		return SEQ_START_TOKEN;
577 
578 	iter = data->stats + (*pos - 1);
579 	if (iter >= data->iter_end)
580 		iter = NULL;
581 
582 	return iter;
583 }
584 
585 static void *ls_next(struct seq_file *m, void *v, loff_t *pos)
586 {
587 	(*pos)++;
588 	return ls_start(m, pos);
589 }
590 
591 static void ls_stop(struct seq_file *m, void *v)
592 {
593 }
594 
595 static int ls_show(struct seq_file *m, void *v)
596 {
597 	if (v == SEQ_START_TOKEN)
598 		seq_header(m);
599 	else
600 		seq_stats(m, v);
601 
602 	return 0;
603 }
604 
605 static const struct seq_operations lockstat_ops = {
606 	.start	= ls_start,
607 	.next	= ls_next,
608 	.stop	= ls_stop,
609 	.show	= ls_show,
610 };
611 
612 static int lock_stat_open(struct inode *inode, struct file *file)
613 {
614 	int res;
615 	struct lock_class *class;
616 	struct lock_stat_seq *data = vmalloc(sizeof(struct lock_stat_seq));
617 
618 	if (!data)
619 		return -ENOMEM;
620 
621 	res = seq_open(file, &lockstat_ops);
622 	if (!res) {
623 		struct lock_stat_data *iter = data->stats;
624 		struct seq_file *m = file->private_data;
625 
626 		list_for_each_entry(class, &all_lock_classes, lock_entry) {
627 			iter->class = class;
628 			iter->stats = lock_stats(class);
629 			iter++;
630 		}
631 		data->iter_end = iter;
632 
633 		sort(data->stats, data->iter_end - data->stats,
634 				sizeof(struct lock_stat_data),
635 				lock_stat_cmp, NULL);
636 
637 		m->private = data;
638 	} else
639 		vfree(data);
640 
641 	return res;
642 }
643 
644 static ssize_t lock_stat_write(struct file *file, const char __user *buf,
645 			       size_t count, loff_t *ppos)
646 {
647 	struct lock_class *class;
648 	char c;
649 
650 	if (count) {
651 		if (get_user(c, buf))
652 			return -EFAULT;
653 
654 		if (c != '0')
655 			return count;
656 
657 		list_for_each_entry(class, &all_lock_classes, lock_entry)
658 			clear_lock_stats(class);
659 	}
660 	return count;
661 }
662 
663 static int lock_stat_release(struct inode *inode, struct file *file)
664 {
665 	struct seq_file *seq = file->private_data;
666 
667 	vfree(seq->private);
668 	return seq_release(inode, file);
669 }
670 
671 static const struct proc_ops lock_stat_proc_ops = {
672 	.proc_open	= lock_stat_open,
673 	.proc_write	= lock_stat_write,
674 	.proc_read	= seq_read,
675 	.proc_lseek	= seq_lseek,
676 	.proc_release	= lock_stat_release,
677 };
678 #endif /* CONFIG_LOCK_STAT */
679 
680 static int __init lockdep_proc_init(void)
681 {
682 	proc_create_seq("lockdep", S_IRUSR, NULL, &lockdep_ops);
683 #ifdef CONFIG_PROVE_LOCKING
684 	proc_create_seq("lockdep_chains", S_IRUSR, NULL, &lockdep_chains_ops);
685 #endif
686 	proc_create_single("lockdep_stats", S_IRUSR, NULL, lockdep_stats_show);
687 #ifdef CONFIG_LOCK_STAT
688 	proc_create("lock_stat", S_IRUSR | S_IWUSR, NULL, &lock_stat_proc_ops);
689 #endif
690 
691 	return 0;
692 }
693 
694 __initcall(lockdep_proc_init);
695 
696