Root/kernel/lockdep.c

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

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