/kernel/lockdep.c

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/*
 * kernel/lockdep.c
 *
 * Runtime locking correctness validator
 *
 * Started by Ingo Molnar:
 *
 *  Copyright (C) 2006,2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
 *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
 *
 * this code maps all the lock dependencies as they occur in a live kernel
 * and will warn about the following classes of locking bugs:
 *
 * - lock inversion scenarios
 * - circular lock dependencies
 * - hardirq/softirq safe/unsafe locking bugs
 *
 * Bugs are reported even if the current locking scenario does not cause
 * any deadlock at this point.
 *
 * I.e. if anytime in the past two locks were taken in a different order,
 * even if it happened for another task, even if those were different
 * locks (but of the same class as this lock), this code will detect it.
 *
 * Thanks to Arjan van de Ven for coming up with the initial idea of
 * mapping lock dependencies runtime.
 */
#define DISABLE_BRANCH_PROFILING
#include <linux/mutex.h>
#include <linux/sched.h>
#include <linux/delay.h>
#include <linux/module.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/spinlock.h>
#include <linux/kallsyms.h>
#include <linux/interrupt.h>
#include <linux/stacktrace.h>
#include <linux/debug_locks.h>
#include <linux/irqflags.h>
#include <linux/utsname.h>
#include <linux/hash.h>
#include <linux/ftrace.h>
#include <linux/stringify.h>
#include <linux/bitops.h>
#include <linux/gfp.h>
#include <linux/kmemcheck.h>

#include <asm/sections.h>

#include "lockdep_internals.h"

#define CREATE_TRACE_POINTS
#include <trace/events/lock.h>

#ifdef CONFIG_PROVE_LOCKING
int prove_locking = 1;
module_param(prove_locking, int, 0644);
#else
#define prove_locking 0
#endif

#ifdef CONFIG_LOCK_STAT
int lock_stat = 1;
module_param(lock_stat, int, 0644);
#else
#define lock_stat 0
#endif

static arch_spinlock_t lockdep_lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;

static int graph_lock(void)
{
	arch_spin_lock(&lockdep_lock);
	if (!debug_locks) {
		arch_spin_unlock(&lockdep_lock);
		return 0;
	}
	
	current->lockdep_recursion++;
	return 1;
}

static inline int graph_unlock(void)
{
	if (debug_locks && !arch_spin_is_locked(&lockdep_lock)) {
		return DEBUG_LOCKS_WARN_ON(1);
	}

	current->lockdep_recursion--;
	arch_spin_unlock(&lockdep_lock);
	return 0;
}

static inline int debug_locks_off_graph_unlock(void)
{
	int ret = debug_locks_off();

	arch_spin_unlock(&lockdep_lock);

	return ret;
}

static int lockdep_initialized;

unsigned long nr_list_entries;
static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES];

unsigned long nr_lock_classes;
static struct lock_class lock_classes[MAX_LOCKDEP_KEYS];

static inline struct lock_class *hlock_class(struct held_lock *hlock)
{
	if (!hlock->class_idx) {
		DEBUG_LOCKS_WARN_ON(1);
		return NULL;
	}
	return lock_classes + hlock->class_idx - 1;
}

#ifdef CONFIG_LOCK_STAT
static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS],
		      cpu_lock_stats);

static inline u64 lockstat_clock(void)
{
	return local_clock();
}

static int lock_point(unsigned long points[], unsigned long ip)
{
	int i;

	for (i = 0; i < LOCKSTAT_POINTS; i++) {
		if (points[i] == 0) {
			points[i] = ip;
			break;
		}
		if (points[i] == ip)
			break;
	}

	return i;
}

static void lock_time_inc(struct lock_time *lt, u64 time)
{
	if (time > lt->max)
		lt->max = time;

	if (time < lt->min || !lt->nr)
		lt->min = time;

	lt->total += time;
	lt->nr++;
}

static inline void lock_time_add(struct lock_time *src, struct lock_time *dst)
{
	if (!src->nr)
		return;

	if (src->max > dst->max)
		dst->max = src->max;

	if (src->min < dst->min || !dst->nr)
		dst->min = src->min;

	dst->total += src->total;
	dst->nr += src->nr;
}

struct lock_class_stats lock_stats(struct lock_class *class)
{
	struct lock_class_stats stats;
	int cpu, i;

	memset(&stats, 0, sizeof(struct lock_class_stats));
	for_each_possible_cpu(cpu) {
		struct lock_class_stats *pcs =
			&per_cpu(cpu_lock_stats, cpu)[class - lock_classes];

		for (i = 0; i < ARRAY_SIZE(stats.contention_point); i++)
			stats.contention_point[i] += pcs->contention_point[i];

		for (i = 0; i < ARRAY_SIZE(stats.contending_point); i++)
			stats.contending_point[i] += pcs->contending_point[i];

		lock_time_add(&pcs->read_waittime, &stats.read_waittime);
		lock_time_add(&pcs->write_waittime, &stats.write_waittime);

		lock_time_add(&pcs->read_holdtime, &stats.read_holdtime);
		lock_time_add(&pcs->write_holdtime, &stats.write_holdtime);

		for (i = 0; i < ARRAY_SIZE(stats.bounces); i++)
			stats.bounces[i] += pcs->bounces[i];
	}

	return stats;
}

void clear_lock_stats(struct lock_class *class)
{
	int cpu;

	for_each_possible_cpu(cpu) {
		struct lock_class_stats *cpu_stats =
			&per_cpu(cpu_lock_stats, cpu)[class - lock_classes];

		memset(cpu_stats, 0, sizeof(struct lock_class_stats));
	}
	memset(class->contention_point, 0, sizeof(class->contention_point));
	memset(class->contending_point, 0, sizeof(class->contending_point));
}

static struct lock_class_stats *get_lock_stats(struct lock_class *class)
{
	return &get_cpu_var(cpu_lock_stats)[class - lock_classes];
}

static void put_lock_stats(struct lock_class_stats *stats)
{
	put_cpu_var(cpu_lock_stats);
}

static void lock_release_holdtime(struct held_lock *hlock)
{
	struct lock_class_stats *stats;
	u64 holdtime;

	if (!lock_stat)
		return;

	holdtime = lockstat_clock() - hlock->holdtime_stamp;

	stats = get_lock_stats(hlock_class(hlock));
	if (hlock->read)
		lock_time_inc(&stats->read_holdtime, holdtime);
	else
		lock_time_inc(&stats->write_holdtime, holdtime);
	put_lock_stats(stats);
}
#else
static inline void lock_release_holdtime(struct held_lock *hlock)
{
}
#endif

LIST_HEAD(all_lock_classes);

#define CLASSHASH_BITS		(MAX_LOCKDEP_KEYS_BITS - 1)
#define CLASSHASH_SIZE		(1UL << CLASSHASH_BITS)
#define __classhashfn(key)	hash_long((unsigned long)key, CLASSHASH_BITS)
#define classhashentry(key)	(classhash_table + __classhashfn((key)))

static struct list_head classhash_table[CLASSHASH_SIZE];

#define CHAINHASH_BITS		(MAX_LOCKDEP_CHAINS_BITS-1)
#define CHAINHASH_SIZE		(1UL << CHAINHASH_BITS)
#define __chainhashfn(chain)	hash_long(chain, CHAINHASH_BITS)
#define chainhashentry(chain)	(chainhash_table + __chainhashfn((chain)))

static struct list_head chainhash_table[CHAINHASH_SIZE];

#define iterate_chain_key(key1, key2) \
	(((key1) << MAX_LOCKDEP_KEYS_BITS) ^ \
	((key1) >> (64-MAX_LOCKDEP_KEYS_BITS)) ^ \
	(key2))

void lockdep_off(void)
{
	current->lockdep_recursion++;
}
EXPORT_SYMBOL(lockdep_off);

void lockdep_on(void)
{
	current->lockdep_recursion--;
}
EXPORT_SYMBOL(lockdep_on);


#define VERBOSE			0
#define VERY_VERBOSE		0

#if VERBOSE
# define HARDIRQ_VERBOSE	1
# define SOFTIRQ_VERBOSE	1
# define RECLAIM_VERBOSE	1
#else
# define HARDIRQ_VERBOSE	0
# define SOFTIRQ_VERBOSE	0
# define RECLAIM_VERBOSE	0
#endif

#if VERBOSE || HARDIRQ_VERBOSE || SOFTIRQ_VERBOSE || RECLAIM_VERBOSE
static int class_filter(struct lock_class *class)
{
#if 0
	
	if (class->name_version == 1 &&
			!strcmp(class->name, "lockname"))
		return 1;
	if (class->name_version == 1 &&
			!strcmp(class->name, "&struct->lockfield"))
		return 1;
#endif
	
	return 0;
}
#endif

static int verbose(struct lock_class *class)
{
#if VERBOSE
	return class_filter(class);
#endif
	return 0;
}

unsigned long nr_stack_trace_entries;
static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];

static int save_trace(struct stack_trace *trace)
{
	trace->nr_entries = 0;
	trace->max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries;
	trace->entries = stack_trace + nr_stack_trace_entries;

	trace->skip = 3;

	save_stack_trace(trace);

	if (trace->nr_entries != 0 &&
	    trace->entries[trace->nr_entries-1] == ULONG_MAX)
		trace->nr_entries--;

	trace->max_entries = trace->nr_entries;

	nr_stack_trace_entries += trace->nr_entries;

	if (nr_stack_trace_entries >= MAX_STACK_TRACE_ENTRIES-1) {
		if (!debug_locks_off_graph_unlock())
			return 0;

		printk("BUG: MAX_STACK_TRACE_ENTRIES too low!\n");
		printk("turning off the locking correctness validator.\n");
		dump_stack();

		return 0;
	}

	return 1;
}

unsigned int nr_hardirq_chains;
unsigned int nr_softirq_chains;
unsigned int nr_process_chains;
unsigned int max_lockdep_depth;

#ifdef CONFIG_DEBUG_LOCKDEP
static int lockdep_init_error;
static const char *lock_init_error;
static unsigned long lockdep_init_trace_data[20];
static struct stack_trace lockdep_init_trace = {
	.max_entries = ARRAY_SIZE(lockdep_init_trace_data),
	.entries = lockdep_init_trace_data,
};

DEFINE_PER_CPU(struct lockdep_stats, lockdep_stats);
#endif


#define __USAGE(__STATE)						\
	[LOCK_USED_IN_##__STATE] = "IN-"__stringify(__STATE)"-W",	\
	[LOCK_ENABLED_##__STATE] = __stringify(__STATE)"-ON-W",		\
	[LOCK_USED_IN_##__STATE##_READ] = "IN-"__stringify(__STATE)"-R",\
	[LOCK_ENABLED_##__STATE##_READ] = __stringify(__STATE)"-ON-R",

static const char *usage_str[] =
{
#define LOCKDEP_STATE(__STATE) __USAGE(__STATE)
#include "lockdep_states.h"
#undef LOCKDEP_STATE
	[LOCK_USED] = "INITIAL USE",
};

const char * __get_key_name(struct lockdep_subclass_key *key, char *str)
{
	return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str);
}

static inline unsigned long lock_flag(enum lock_usage_bit bit)
{
	return 1UL << bit;
}

static char get_usage_char(struct lock_class *class, enum lock_usage_bit bit)
{
	char c = '.';

	if (class->usage_mask & lock_flag(bit + 2))
		c = '+';
	if (class->usage_mask & lock_flag(bit)) {
		c = '-';
		if (class->usage_mask & lock_flag(bit + 2))
			c = '?';
	}

	return c;
}

void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS])
{
	int i = 0;

#define LOCKDEP_STATE(__STATE) 						\
	usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE);	\
	usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE##_READ);
#include "lockdep_states.h"
#undef LOCKDEP_STATE

	usage[i] = '\0';
}

static void __print_lock_name(struct lock_class *class)
{
	char str[KSYM_NAME_LEN];
	const char *name;

	name = class->name;
	if (!name) {
		name = __get_key_name(class->key, str);
		printk("%s", name);
	} else {
		printk("%s", name);
		if (class->name_version > 1)
			printk("#%d", class->name_version);
		if (class->subclass)
			printk("/%d", class->subclass);
	}
}

static void print_lock_name(struct lock_class *class)
{
	char usage[LOCK_USAGE_CHARS];

	get_usage_chars(class, usage);

	printk(" (");
	__print_lock_name(class);
	printk("){%s}", usage);
}

static void print_lockdep_cache(struct lockdep_map *lock)
{
	const char *name;
	char str[KSYM_NAME_LEN];

	name = lock->name;
	if (!name)
		name = __get_key_name(lock->key->subkeys, str);

	printk("%s", name);
}

static void print_lock(struct held_lock *hlock)
{
	print_lock_name(hlock_class(hlock));
	printk(", at: ");
	print_ip_sym(hlock->acquire_ip);
}

static void lockdep_print_held_locks(struct task_struct *curr)
{
	int i, depth = curr->lockdep_depth;

	if (!depth) {
		printk("no locks held by %s/%d.\n", curr->comm, task_pid_nr(curr));
		return;
	}
	printk("%d lock%s held by %s/%d:\n",
		depth, depth > 1 ? "s" : "", curr->comm, task_pid_nr(curr));

	for (i = 0; i < depth; i++) {
		printk(" #%d: ", i);
		print_lock(curr->held_locks + i);
	}
}

static void print_kernel_ident(void)
{
	printk("%s %.*s %s\n", init_utsname()->release,
		(int)strcspn(init_utsname()->version, " "),
		init_utsname()->version,
		print_tainted());
}

static int very_verbose(struct lock_class *class)
{
#if VERY_VERBOSE
	return class_filter(class);
#endif
	return 0;
}

static int static_obj(void *obj)
{
	unsigned long start = (unsigned long) &_stext,
		      end   = (unsigned long) &_end,
		      addr  = (unsigned long) obj;

	if ((addr >= start) && (addr < end))
		return 1;

	if (arch_is_kernel_data(addr))
		return 1;

	if (is_kernel_percpu_address(addr))
		return 1;

	return is_module_address(addr) || is_module_percpu_address(addr);
}

static int count_matching_names(struct lock_class *new_class)
{
	struct lock_class *class;
	int count = 0;

	if (!new_class->name)
		return 0;

	list_for_each_entry(class, &all_lock_classes, lock_entry) {
		if (new_class->key - new_class->subclass == class->key)
			return class->name_version;
		if (class->name && !strcmp(class->name, new_class->name))
			count = max(count, class->name_version);
	}

	return count + 1;
}

static inline struct lock_class *
look_up_lock_class(struct lockdep_map *lock, unsigned int subclass)
{
	struct lockdep_subclass_key *key;
	struct list_head *hash_head;
	struct lock_class *class;

#ifdef CONFIG_DEBUG_LOCKDEP
	if (unlikely(!lockdep_initialized)) {
		lockdep_init();
		lockdep_init_error = 1;
		lock_init_error = lock->name;
		save_stack_trace(&lockdep_init_trace);
	}
#endif

	if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
		debug_locks_off();
		printk(KERN_ERR
			"BUG: looking up invalid subclass: %u\n", subclass);
		printk(KERN_ERR
			"turning off the locking correctness validator.\n");
		dump_stack();
		return NULL;
	}

	if (unlikely(!lock->key))
		lock->key = (void *)lock;

	BUILD_BUG_ON(sizeof(struct lock_class_key) >
			sizeof(struct lockdep_map));

	key = lock->key->subkeys + subclass;

	hash_head = classhashentry(key);

	list_for_each_entry(class, hash_head, hash_entry) {
		if (class->key == key) {
			WARN_ON_ONCE(class->name != lock->name);
			return class;
		}
	}

	return NULL;
}

static inline struct lock_class *
register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
{
	struct lockdep_subclass_key *key;
	struct list_head *hash_head;
	struct lock_class *class;
	unsigned long flags;

	class = look_up_lock_class(lock, subclass);
	if (likely(class))
		goto out_set_class_cache;

	if (!static_obj(lock->key)) {
		debug_locks_off();
		printk("INFO: trying to register non-static key.\n");
		printk("the code is fine but needs lockdep annotation.\n");
		printk("turning off the locking correctness validator.\n");
		dump_stack();

		return NULL;
	}

	key = lock->key->subkeys + subclass;
	hash_head = classhashentry(key);

	raw_local_irq_save(flags);
	if (!graph_lock()) {
		raw_local_irq_restore(flags);
		return NULL;
	}
	list_for_each_entry(class, hash_head, hash_entry)
		if (class->key == key)
			goto out_unlock_set;
	if (nr_lock_classes >= MAX_LOCKDEP_KEYS) {
		if (!debug_locks_off_graph_unlock()) {
			raw_local_irq_restore(flags);
			return NULL;
		}
		raw_local_irq_restore(flags);

		printk("BUG: MAX_LOCKDEP_KEYS too low!\n");
		printk("turning off the locking correctness validator.\n");
		dump_stack();
		return NULL;
	}
	class = lock_classes + nr_lock_classes++;
	debug_atomic_inc(nr_unused_locks);
	class->key = key;
	class->name = lock->name;
	class->subclass = subclass;
	INIT_LIST_HEAD(&class->lock_entry);
	INIT_LIST_HEAD(&class->locks_before);
	INIT_LIST_HEAD(&class->locks_after);
	class->name_version = count_matching_names(class);
	list_add_tail_rcu(&class->hash_entry, hash_head);
	list_add_tail_rcu(&class->lock_entry, &all_lock_classes);

	if (verbose(class)) {
		graph_unlock();
		raw_local_irq_restore(flags);

		printk("\nnew class %p: %s", class->key, class->name);
		if (class->name_version > 1)
			printk("#%d", class->name_version);
		printk("\n");
		dump_stack();

		raw_local_irq_save(flags);
		if (!graph_lock()) {
			raw_local_irq_restore(flags);
			return NULL;
		}
	}
out_unlock_set:
	graph_unlock();
	raw_local_irq_restore(flags);

out_set_class_cache:
	if (!subclass || force)
		lock->class_cache[0] = class;
	else if (subclass < NR_LOCKDEP_CACHING_CLASSES)
		lock->class_cache[subclass] = class;

	if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))
		return NULL;

	return class;
}

#ifdef CONFIG_PROVE_LOCKING
static struct lock_list *alloc_list_entry(void)
{
	if (nr_list_entries >= MAX_LOCKDEP_ENTRIES) {
		if (!debug_locks_off_graph_unlock())
			return NULL;

		printk("BUG: MAX_LOCKDEP_ENTRIES too low!\n");
		printk("turning off the locking correctness validator.\n");
		dump_stack();
		return NULL;
	}
	return list_entries + nr_list_entries++;
}

static int add_lock_to_list(struct lock_class *class, struct lock_class *this,
			    struct list_head *head, unsigned long ip,
			    int distance, struct stack_trace *trace)
{
	struct lock_list *entry;
	entry = alloc_list_entry();
	if (!entry)
		return 0;

	entry->class = this;
	entry->distance = distance;
	entry->trace = *trace;
	list_add_tail_rcu(&entry->entry, head);

	return 1;
}

#define MAX_CIRCULAR_QUEUE_SIZE		4096UL
#define CQ_MASK				(MAX_CIRCULAR_QUEUE_SIZE-1)

struct circular_queue {
	unsigned long element[MAX_CIRCULAR_QUEUE_SIZE];
	unsigned int  front, rear;
};

static struct circular_queue lock_cq;

unsigned int max_bfs_queue_depth;

static unsigned int lockdep_dependency_gen_id;

static inline void __cq_init(struct circular_queue *cq)
{
	cq->front = cq->rear = 0;
	lockdep_dependency_gen_id++;
}

static inline int __cq_empty(struct circular_queue *cq)
{
	return (cq->front == cq->rear);
}

static inline int __cq_full(struct circular_queue *cq)
{
	return ((cq->rear + 1) & CQ_MASK) == cq->front;
}

static inline int __cq_enqueue(struct circular_queue *cq, unsigned long elem)
{
	if (__cq_full(cq))
		return -1;

	cq->element[cq->rear] = elem;
	cq->rear = (cq->rear + 1) & CQ_MASK;
	return 0;
}

static inline int __cq_dequeue(struct circular_queue *cq, unsigned long *elem)
{
	if (__cq_empty(cq))
		return -1;

	*elem = cq->element[cq->front];
	cq->front = (cq->front + 1) & CQ_MASK;
	return 0;
}

static inline unsigned int  __cq_get_elem_count(struct circular_queue *cq)
{
	return (cq->rear - cq->front) & CQ_MASK;
}

static inline void mark_lock_accessed(struct lock_list *lock,
					struct lock_list *parent)
{
	unsigned long nr;

	nr = lock - list_entries;
	WARN_ON(nr >= nr_list_entries); 
	lock->parent = parent;
	lock->class->dep_gen_id = lockdep_dependency_gen_id;
}

static inline unsigned long lock_accessed(struct lock_list *lock)
{
	unsigned long nr;

	nr = lock - list_entries;
	WARN_ON(nr >= nr_list_entries); 
	return lock->class->dep_gen_id == lockdep_dependency_gen_id;
}

static inline struct lock_list *get_lock_parent(struct lock_list *child)
{
	return child->parent;
}

static inline int get_lock_depth(struct lock_list *child)
{
	int depth = 0;
	struct lock_list *parent;

	while ((parent = get_lock_parent(child))) {
		child = parent;
		depth++;
	}
	return depth;
}

static int __bfs(struct lock_list *source_entry,
		 void *data,
		 int (*match)(struct lock_list *entry, void *data),
		 struct lock_list **target_entry,
		 int forward)
{
	struct lock_list *entry;
	struct list_head *head;
	struct circular_queue *cq = &lock_cq;
	int ret = 1;

	if (match(source_entry, data)) {
		*target_entry = source_entry;
		ret = 0;
		goto exit;
	}

	if (forward)
		head = &source_entry->class->locks_after;
	else
		head = &source_entry->class->locks_before;

	if (list_empty(head))
		goto exit;

	__cq_init(cq);
	__cq_enqueue(cq, (unsigned long)source_entry);

	while (!__cq_empty(cq)) {
		struct lock_list *lock;

		__cq_dequeue(cq, (unsigned long *)&lock);

		if (!lock->class) {
			ret = -2;
			goto exit;
		}

		if (forward)
			head = &lock->class->locks_after;
		else
			head = &lock->class->locks_before;

		list_for_each_entry(entry, head, entry) {
			if (!lock_accessed(entry)) {
				unsigned int cq_depth;
				mark_lock_accessed(entry, lock);
				if (match(entry, data)) {
					*target_entry = entry;
					ret = 0;
					goto exit;
				}

				if (__cq_enqueue(cq, (unsigned long)entry)) {
					ret = -1;
					goto exit;
				}
				cq_depth = __cq_get_elem_count(cq);
				if (max_bfs_queue_depth < cq_depth)
					max_bfs_queue_depth = cq_depth;
			}
		}
	}
exit:
	return ret;
}

static inline int __bfs_forwards(struct lock_list *src_entry,
			void *data,
			int (*match)(struct lock_list *entry, void *data),
			struct lock_list **target_entry)
{
	return __bfs(src_entry, data, match, target_entry, 1);

}

static inline int __bfs_backwards(struct lock_list *src_entry,
			void *data,
			int (*match)(struct lock_list *entry, void *data),
			struct lock_list **target_entry)
{
	return __bfs(src_entry, data, match, target_entry, 0);

}


static noinline int
print_circular_bug_entry(struct lock_list *target, int depth)
{
	if (debug_locks_silent)
		return 0;
	printk("\n-> #%u", depth);
	print_lock_name(target->class);
	printk(":\n");
	print_stack_trace(&target->trace, 6);

	return 0;
}

static void
print_circular_lock_scenario(struct held_lock *src,
			     struct held_lock *tgt,
			     struct lock_list *prt)
{
	struct lock_class *source = hlock_class(src);
	struct lock_class *target = hlock_class(tgt);
	struct lock_class *parent = prt->class;

	if (parent != source) {
		printk("Chain exists of:\n  ");
		__print_lock_name(source);
		printk(" --> ");
		__print_lock_name(parent);
		printk(" --> ");
		__print_lock_name(target);
		printk("\n\n");
	}

	printk(" Possible unsafe locking scenario:\n\n");
	printk("       CPU0                    CPU1\n");
	printk("       ----                    ----\n");
	printk("  lock(");
	__print_lock_name(target);
	printk(");\n");
	printk("                               lock(");
	__print_lock_name(parent);
	printk(");\n");
	printk("                               lock(");
	__print_lock_name(target);
	printk(");\n");
	printk("  lock(");
	__print_lock_name(source);
	printk(");\n");
	printk("\n *** DEADLOCK ***\n\n");
}

static noinline int
print_circular_bug_header(struct lock_list *entry, unsigned int depth,
			struct held_lock *check_src,
			struct held_lock *check_tgt)
{
	struct task_struct *curr = current;

	if (debug_locks_silent)
		return 0;

	printk("\n");
	printk("======================================================\n");
	printk("[ INFO: possible circular locking dependency detected ]\n");
	print_kernel_ident();
	printk("-------------------------------------------------------\n");
	printk("%s/%d is trying to acquire lock:\n",
		curr->comm, task_pid_nr(curr));
	print_lock(check_src);
	printk("\nbut task is already holding lock:\n");
	print_lock(check_tgt);
	printk("\nwhich lock already depends on the new lock.\n\n");
	printk("\nthe existing dependency chain (in reverse order) is:\n");

	print_circular_bug_entry(entry, depth);

	return 0;
}

static inline int class_equal(struct lock_list *entry, void *data)
{
	return entry->class == data;
}

static noinline int print_circular_bug(struct lock_list *this,
				struct lock_list *target,
				struct held_lock *check_src,
				struct held_lock *check_tgt)
{
	struct task_struct *curr = current;
	struct lock_list *parent;
	struct lock_list *first_parent;
	int depth;

	if (!debug_locks_off_graph_unlock() || debug_locks_silent)
		return 0;

	if (!save_trace(&this->trace))
		return 0;

	depth = get_lock_depth(target);

	print_circular_bug_header(target, depth, check_src, check_tgt);

	parent = get_lock_parent(target);
	first_parent = parent;

	while (parent) {
		print_circular_bug_entry(parent, --depth);
		parent = get_lock_parent(parent);
	}

	printk("\nother info that might help us debug this:\n\n");
	print_circular_lock_scenario(check_src, check_tgt,
				     first_parent);

	lockdep_print_held_locks(curr);

	printk("\nstack backtrace:\n");
	dump_stack();

	return 0;
}

static noinline int print_bfs_bug(int ret)
{
	if (!debug_locks_off_graph_unlock())
		return 0;

	WARN(1, "lockdep bfs error:%d\n", ret);

	return 0;
}

static int noop_count(struct lock_list *entry, void *data)
{
	(*(unsigned long *)data)++;
	return 0;
}

unsigned long __lockdep_count_forward_deps(struct lock_list *this)
{
	unsigned long  count = 0;
	struct lock_list *uninitialized_var(target_entry);

	__bfs_forwards(this, (void *)&count, noop_count, &target_entry);

	return count;
}
unsigned long lockdep_count_forward_deps(struct lock_class *class)
{
	unsigned long ret, flags;
	struct lock_list this;

	this.parent = NULL;
	this.class = class;

	local_irq_save(flags);
	arch_spin_lock(&lockdep_lock);
	ret = __lockdep_count_forward_deps(&this);
	arch_spin_unlock(&lockdep_lock);
	local_irq_restore(flags);

	return ret;
}

unsigned long __lockdep_count_backward_deps(struct lock_list *this)
{
	unsigned long  count = 0;
	struct lock_list *uninitialized_var(target_entry);

	__bfs_backwards(this, (void *)&count, noop_count, &target_entry);

	return count;
}

unsigned long lockdep_count_backward_deps(struct lock_class *class)
{
	unsigned long ret, flags;
	struct lock_list this;

	this.parent = NULL;
	this.class = class;

	local_irq_save(flags);
	arch_spin_lock(&lockdep_lock);
	ret = __lockdep_count_backward_deps(&this);
	arch_spin_unlock(&lockdep_lock);
	local_irq_restore(flags);

	return ret;
}

static noinline int
check_noncircular(struct lock_list *root, struct lock_class *target,
		struct lock_list **target_entry)
{
	int result;

	debug_atomic_inc(nr_cyclic_checks);

	result = __bfs_forwards(root, target, class_equal, target_entry);

	return result;
}

#if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)

static inline int usage_match(struct lock_list *entry, void *bit)
{
	return entry->class->usage_mask & (1 << (enum lock_usage_bit)bit);
}



static int
find_usage_forwards(struct lock_list *root, enum lock_usage_bit bit,
			struct lock_list **target_entry)
{
	int result;

	debug_atomic_inc(nr_find_usage_forwards_checks);

	result = __bfs_forwards(root, (void *)bit, usage_match, target_entry);

	return result;
}

static int
find_usage_backwards(struct lock_list *root, enum lock_usage_bit bit,
			struct lock_list **target_entry)
{
	int result;

	debug_atomic_inc(nr_find_usage_backwards_checks);

	result = __bfs_backwards(root, (void *)bit, usage_match, target_entry);

	return result;
}

static void print_lock_class_header(struct lock_class *class, int depth)
{
	int bit;

	printk("%*s->", depth, "");
	print_lock_name(class);
	printk(" ops: %lu", class->ops);
	printk(" {\n");

	for (bit = 0; bit < LOCK_USAGE_STATES; bit++) {
		if (class->usage_mask & (1 << bit)) {
			int len = depth;

			len += printk("%*s   %s", depth, "", usage_str[bit]);
			len += printk(" at:\n");
			print_stack_trace(class->usage_traces + bit, len);
		}
	}
	printk("%*s }\n", depth, "");

	printk("%*s ... key      at: ",depth,"");
	print_ip_sym((unsigned long)class->key);
}

static void __used
print_shortest_lock_dependencies(struct lock_list *leaf,
				struct lock_list *root)
{
	struct lock_list *entry = leaf;
	int depth;

	
	depth = get_lock_depth(leaf);

	do {
		print_lock_class_header(entry->class, depth);
		printk("%*s ... acquired at:\n", depth, "");
		print_stack_trace(&entry->trace, 2);
		printk("\n");

		if (depth == 0 && (entry != root)) {
			printk("lockdep:%s bad path found in chain graph\n", __func__);
			break;
		}

		entry = get_lock_parent(entry);
		depth--;
	} while (entry && (depth >= 0));

	return;
}

static void
print_irq_lock_scenario(struct lock_list *safe_entry,
			struct lock_list *unsafe_entry,
			struct lock_class *prev_class,
			struct lock_class *next_class)
{
	struct lock_class *safe_class = safe_entry->class;
	struct lock_class *unsafe_class = unsafe_entry->class;
	struct lock_class *middle_class = prev_class;

	if (middle_class == safe_class)
		middle_class = next_class;

	if (middle_class != unsafe_class) {
		printk("Chain exists of:\n  ");
		__print_lock_name(safe_class);
		printk(" --> ");
		__print_lock_name(middle_class);
		printk(" --> ");
		__print_lock_name(unsafe_class);
		printk("\n\n");
	}

	printk(" Possible interrupt unsafe locking scenario:\n\n");
	printk("       CPU0                    CPU1\n");
	printk("       ----                    ----\n");
	printk("  lock(");
	__print_lock_name(unsafe_class);
	printk(");\n");
	printk("                               local_irq_disable();\n");
	printk("                               lock(");
	__print_lock_name(safe_class);
	printk(");\n");
	printk("                               lock(");
	__print_lock_name(middle_class);
	printk(");\n");
	printk("  <Interrupt>\n");
	printk("    lock(");
	__print_lock_name(safe_class);
	printk(");\n");
	printk("\n *** DEADLOCK ***\n\n");
}

static int
print_bad_irq_dependency(struct task_struct *curr,
			 struct lock_list *prev_root,
			 struct lock_list *next_root,
			 struct lock_list *backwards_entry,
			 struct lock_list *forwards_entry,
			 struct held_lock *prev,
			 struct held_lock *next,
			 enum lock_usage_bit bit1,
			 enum lock_usage_bit bit2,
			 const char *irqclass)
{
	if (!debug_locks_off_graph_unlock() || debug_locks_silent)
		return 0;

	printk("\n");
	printk("======================================================\n");
	printk("[ INFO: %s-safe -> %s-unsafe lock order detected ]\n",
		irqclass, irqclass);
	print_kernel_ident();
	printk("------------------------------------------------------\n");
	printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
		curr->comm, task_pid_nr(curr),
		curr->hardirq_context, hardirq_count() >> HARDIRQ_SHIFT,
		curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT,
		curr->hardirqs_enabled,
		curr->softirqs_enabled);
	print_lock(next);

	printk("\nand this task is already holding:\n");
	print_lock(prev);
	printk("which would create a new lock dependency:\n");
	print_lock_name(hlock_class(prev));
	printk(" ->");
	print_lock_name(hlock_class(next));
	printk("\n");

	printk("\nbut this new dependency connects a %s-irq-safe lock:\n",
		irqclass);
	print_lock_name(backwards_entry->class);
	printk("\n... which became %s-irq-safe at:\n", irqclass);

	print_stack_trace(backwards_entry->class->usage_traces + bit1, 1);

	printk("\nto a %s-irq-unsafe lock:\n", irqclass);
	print_lock_name(forwards_entry->class);
	printk("\n... which became %s-irq-unsafe at:\n", irqclass);
	printk("...");

	print_stack_trace(forwards_entry->class->usage_traces + bit2, 1);

	printk("\nother info that might help us debug this:\n\n");
	print_irq_lock_scenario(backwards_entry, forwards_entry,
				hlock_class(prev), hlock_class(next));

	lockdep_print_held_locks(curr);

	printk("\nthe dependencies between %s-irq-safe lock", irqclass);
	printk(" and the holding lock:\n");
	if (!save_trace(&prev_root->trace))
		return 0;
	print_shortest_lock_dependencies(backwards_entry, prev_root);

	printk("\nthe dependencies between the lock to be acquired");
	printk(" and %s-irq-unsafe lock:\n", irqclass);
	if (!save_trace(&next_root->trace))
		return 0;
	print_shortest_lock_dependencies(forwards_entry, next_root);

	printk("\nstack backtrace:\n");
	dump_stack();

	return 0;
}

static int
check_usage(struct task_struct *curr, struct held_lock *prev,
	    struct held_lock *next, enum lock_usage_bit bit_backwards,
	    enum lock_usage_bit bit_forwards, const char *irqclass)
{
	int ret;
	struct lock_list this, that;
	struct lock_list *uninitialized_var(target_entry);
	struct lock_list *uninitialized_var(target_entry1);

	this.parent = NULL;

	this.class = hlock_class(prev);
	ret = find_usage_backwards(&this, bit_backwards, &target_entry);
	if (ret < 0)
		return print_bfs_bug(ret);
	if (ret == 1)
		return ret;

	that.parent = NULL;
	that.class = hlock_class(next);
	ret = find_usage_forwards(&that, bit_forwards, &target_entry1);
	if (ret < 0)
		return print_bfs_bug(ret);
	if (ret == 1)
		return ret;

	return print_bad_irq_dependency(curr, &this, &that,
			target_entry, target_entry1,
			prev, next,
			bit_backwards, bit_forwards, irqclass);
}

static const char *state_names[] = {
#define LOCKDEP_STATE(__STATE) \
	__stringify(__STATE),
#include "lockdep_states.h"
#undef LOCKDEP_STATE
};

static const char *state_rnames[] = {
#define LOCKDEP_STATE(__STATE) \
	__stringify(__STATE)"-READ",
#include "lockdep_states.h"
#undef LOCKDEP_STATE
};

static inline const char *state_name(enum lock_usage_bit bit)
{
	return (bit & 1) ? state_rnames[bit >> 2] : state_names[bit >> 2];
}

static int exclusive_bit(int new_bit)
{

	int state = new_bit & ~3;
	int dir = new_bit & 2;

	return state | (dir ^ 2);
}

static int check_irq_usage(struct task_struct *curr, struct held_lock *prev,
			   struct held_lock *next, enum lock_usage_bit bit)
{
	if (!check_usage(curr, prev, next, bit,
			   exclusive_bit(bit), state_name(bit)))
		return 0;

	bit++; 

	if (!check_usage(curr, prev, next, bit,
			   exclusive_bit(bit), state_name(bit)))
		return 0;

	return 1;
}

static int
check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
		struct held_lock *next)
{
#define LOCKDEP_STATE(__STATE)						\
	if (!check_irq_usage(curr, prev, next, LOCK_USED_IN_##__STATE))	\
		return 0;
#include "lockdep_states.h"
#undef LOCKDEP_STATE

	return 1;
}

static void inc_chains(void)
{
	if (current->hardirq_context)
		nr_hardirq_chains++;
	else {
		if (current->softirq_context)
			nr_softirq_chains++;
		else
			nr_process_chains++;
	}
}

#else

static inline int
check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
		struct held_lock *next)
{
	return 1;
}

static inline void inc_chains(void)
{
	nr_process_chains++;
}

#endif

static void
print_deadlock_scenario(struct held_lock *nxt,
			     struct held_lock *prv)
{
	struct lock_class *next = hlock_class(nxt);
	struct lock_class *prev = hlock_class(prv);

	printk(" Possible unsafe locking scenario:\n\n");
	printk("       CPU0\n");
	printk("       ----\n");
	printk("  lock(");
	__print_lock_name(prev);
	printk(");\n");
	printk("  lock(");
	__print_lock_name(next);
	printk(");\n");
	printk("\n *** DEADLOCK ***\n\n");
	printk(" May be due to missing lock nesting notation\n\n");
}

static int
print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
		   struct held_lock *next)
{
	if (!debug_locks_off_graph_unlock() || debug_locks_silent)
		return 0;

	printk("\n");
	printk("=============================================\n");
	printk("[ INFO: possible recursive locking detected ]\n");
	print_kernel_ident();
	printk("---------------------------------------------\n");
	printk("%s/%d is trying to acquire lock:\n",
		curr->comm, task_pid_nr(curr));
	print_lock(next);
	printk("\nbut task is already holding lock:\n");
	print_lock(prev);

	printk("\nother info that might help us debug this:\n");
	print_deadlock_scenario(next, prev);
	lockdep_print_held_locks(curr);

	printk("\nstack backtrace:\n");
	dump_stack();

	return 0;
}

static int
check_deadlock(struct task_struct *curr, struct held_lock *next,
	       struct lockdep_map *next_instance, int read)
{
	struct held_lock *prev;
	struct held_lock *nest = NULL;
	int i;

	for (i = 0; i < curr->lockdep_depth; i++) {
		prev = curr->held_locks + i;

		if (prev->instance == next->nest_lock)
			nest = prev;

		if (hlock_class(prev) != hlock_class(next))
			continue;

		if ((read == 2) && prev->read)
			return 2;

		if (nest)
			return 2;

		return print_deadlock_bug(curr, prev, next);
	}
	return 1;
}

static int
check_prev_add(struct task_struct *curr, struct held_lock *prev,
	       struct held_lock *next, int distance, int trylock_loop)
{
	struct lock_list *entry;
	int ret;
	struct lock_list this;
	struct lock_list *uninitialized_var(target_entry);
	static struct stack_trace trace;

	this.class = hlock_class(next);
	this.parent = NULL;
	ret = check_noncircular(&this, hlock_class(prev), &target_entry);
	if (unlikely(!ret))
		return print_circular_bug(&this, target_entry, next, prev);
	else if (unlikely(ret < 0))
		return print_bfs_bug(ret);

	if (!check_prev_add_irq(curr, prev, next))
		return 0;

	if (next->read == 2 || prev->read == 2)
		return 1;
	list_for_each_entry(entry, &hlock_class(prev)->locks_after, entry) {
		if (entry->class == hlock_class(next)) {
			if (distance == 1)
				entry->distance = 1;
			return 2;
		}
	}

	if (!trylock_loop && !save_trace(&trace))
		return 0;

	ret = add_lock_to_list(hlock_class(prev), hlock_class(next),
			       &hlock_class(prev)->locks_after,
			       next->acquire_ip, distance, &trace);

	if (!ret)
		return 0;

	ret = add_lock_to_list(hlock_class(next), hlock_class(prev),
			       &hlock_class(next)->locks_before,
			       next->acquire_ip, distance, &trace);
	if (!ret)
		return 0;

	if (verbose(hlock_class(prev)) || verbose(hlock_class(next))) {
		graph_unlock();
		printk("\n new dependency: ");
		print_lock_name(hlock_class(prev));
		printk(" => ");
		print_lock_name(hlock_class(next));
		printk("\n");
		dump_stack();
		return graph_lock();
	}
	return 1;
}

static int
check_prevs_add(struct task_struct *curr, struct held_lock *next)
{
	int depth = curr->lockdep_depth;
	int trylock_loop = 0;
	struct held_lock *hlock;

	if (!depth)
		goto out_bug;
	if (curr->held_locks[depth].irq_context !=
			curr->held_locks[depth-1].irq_context)
		goto out_bug;

	for (;;) {
		int distance = curr->lockdep_depth - depth + 1;
		hlock = curr->held_locks + depth-1;
		if (hlock->read != 2) {
			if (!check_prev_add(curr, hlock, next,
						distance, trylock_loop))
				return 0;
			if (!hlock->trylock)
				break;
		}
		depth--;
		if (!depth)
			break;
		if (curr->held_locks[depth].irq_context !=
				curr->held_locks[depth-1].irq_context)
			break;
		trylock_loop = 1;
	}
	return 1;
out_bug:
	if (!debug_locks_off_graph_unlock())
		return 0;

	WARN_ON(1);

	return 0;
}

unsigned long nr_lock_chains;
struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
int nr_chain_hlocks;
static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];

struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
{
	return lock_classes + chain_hlocks[chain->base + i];
}

static inline int lookup_chain_cache(struct task_struct *curr,
				     struct held_lock *hlock,
				     u64 chain_key)
{
	struct lock_class *class = hlock_class(hlock);
	struct list_head *hash_head = chainhashentry(chain_key);
	struct lock_chain *chain;
	struct held_lock *hlock_curr, *hlock_next;
	int i, j;

	if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
		return 0;
	list_for_each_entry(chain, hash_head, entry) {
		if (chain->chain_key == chain_key) {
cache_hit:
			debug_atomic_inc(chain_lookup_hits);
			if (very_verbose(class))
				printk("\nhash chain already cached, key: "
					"%016Lx tail class: [%p] %s\n",
					(unsigned long long)chain_key,
					class->key, class->name);
			return 0;
		}
	}
	if (very_verbose(class))
		printk("\nnew hash chain, key: %016Lx tail class: [%p] %s\n",
			(unsigned long long)chain_key, class->key, class->name);
	if (!graph_lock())
		return 0;
	list_for_each_entry(chain, hash_head, entry) {
		if (chain->chain_key == chain_key) {
			graph_unlock();
			goto cache_hit;
		}
	}
	if (unlikely(nr_lock_chains >= MAX_LOCKDEP_CHAINS)) {
		if (!debug_locks_off_graph_unlock())
			return 0;

		printk("BUG: MAX_LOCKDEP_CHAINS too low!\n");
		printk("turning off the locking correctness validator.\n");
		dump_stack();
		return 0;
	}
	chain = lock_chains + nr_lock_chains++;
	chain->chain_key = chain_key;
	chain->irq_context = hlock->irq_context;
	
	hlock_next = hlock;
	for (i = curr->lockdep_depth - 1; i >= 0; i--) {
		hlock_curr = curr->held_locks + i;
		if (hlock_curr->irq_context != hlock_next->irq_context)
			break;
		hlock_next = hlock;
	}
	i++;
	chain->depth = curr->lockdep_depth + 1 - i;
	if (likely(nr_chain_hlocks + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) {
		chain->base = nr_chain_hlocks;
		nr_chain_hlocks += chain->depth;
		for (j = 0; j < chain->depth - 1; j++, i++) {
			int lock_id = curr->held_locks[i].class_idx - 1;
			chain_hlocks[chain->base + j] = lock_id;
		}
		chain_hlocks[chain->base + j] = class - lock_classes;
	}
	list_add_tail_rcu(&chain->entry, hash_head);
	debug_atomic_inc(chain_lookup_misses);
	inc_chains();

	return 1;
}

static int validate_chain(struct task_struct *curr, struct lockdep_map *lock,
		struct held_lock *hlock, int chain_head, u64 chain_key)
{
	if (!hlock->trylock && (hlock->check == 2) &&
	    lookup_chain_cache(curr, hlock, chain_key)) {
		int ret = check_deadlock(curr, hlock, lock, hlock->read);

		if (!ret)
			return 0;
		if (ret == 2)
			hlock->read = 2;
		if (!chain_head && ret != 2)
			if (!check_prevs_add(curr, hlock))
				return 0;
		graph_unlock();
	} else
		
		if (unlikely(!debug_locks))
			return 0;

	return 1;
}
#else
static inline int validate_chain(struct task_struct *curr,
	       	struct lockdep_map *lock, struct held_lock *hlock,
		int chain_head, u64 chain_key)
{
	return 1;
}
#endif

static void check_chain_key(struct task_struct *curr)
{
#ifdef CONFIG_DEBUG_LOCKDEP
	struct held_lock *hlock, *prev_hlock = NULL;
	unsigned int i, id;
	u64 chain_key = 0;

	for (i = 0; i < curr->lockdep_depth; i++) {
		hlock = curr->held_locks + i;
		if (chain_key != hlock->prev_chain_key) {
			debug_locks_off();
			WARN(1, "hm#1, depth: %u [%u], %016Lx != %016Lx\n",
				curr->lockdep_depth, i,
				(unsigned long long)chain_key,
				(unsigned long long)hlock->prev_chain_key);
			return;
		}
		id = hlock->class_idx - 1;
		if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
			return;

		if (prev_hlock && (prev_hlock->irq_context !=
							hlock->irq_context))
			chain_key = 0;
		chain_key = iterate_chain_key(chain_key, id);
		prev_hlock = hlock;
	}
	if (chain_key != curr->curr_chain_key) {
		debug_locks_off();
		WARN(1, "hm#2, depth: %u [%u], %016Lx != %016Lx\n",
			curr->lockdep_depth, i,
			(unsigned long long)chain_key,
			(unsigned long long)curr->curr_chain_key);
	}
#endif
}

static void
print_usage_bug_scenario(struct held_lock *lock)
{
	struct lock_class *class = hlock_class(lock);

	printk(" Possible unsafe locking scenario:\n\n");
	printk("       CPU0\n");
	printk("       ----\n");
	printk("  lock(");
	__print_lock_name(class);
	printk(");\n");
	printk("  <Interrupt>\n");
	printk("    lock(");
	__print_lock_name(class);
	printk(");\n");
	printk("\n *** DEADLOCK ***\n\n");
}

static int
print_usage_bug(struct task_struct *curr, struct held_lock *this,
		enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
{
	if (!debug_locks_off_graph_unlock() || debug_locks_silent)
		return 0;

	printk("\n");
	printk("=================================\n");
	printk("[ INFO: inconsistent lock state ]\n");
	print_kernel_ident();
	printk("---------------------------------\n");

	printk("inconsistent {%s} -> {%s} usage.\n",
		usage_str[prev_bit], usage_str[new_bit]);

	printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] takes:\n",
		curr->comm, task_pid_nr(curr),
		trace_hardirq_context(curr), hardirq_count() >> HARDIRQ_SHIFT,
		trace_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT,
		trace_hardirqs_enabled(curr),
		trace_softirqs_enabled(curr));
	print_lock(this);

	printk("{%s} state was registered at:\n", usage_str[prev_bit]);
	print_stack_trace(hlock_class(this)->usage_traces + prev_bit, 1);

	print_irqtrace_events(curr);
	printk("\nother info that might help us debug this:\n");
	print_usage_bug_scenario(this);

	lockdep_print_held_locks(curr);

	printk("\nstack backtrace:\n");
	dump_stack();

	return 0;
}

static inline int
valid_state(struct task_struct *curr, struct held_lock *this,
	    enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit)
{
	if (unlikely(hlock_class(this)->usage_mask & (1 << bad_bit)))
		return print_usage_bug(curr, this, bad_bit, new_bit);
	return 1;
}

static int mark_lock(struct task_struct *curr, struct held_lock *this,
		     enum lock_usage_bit new_bit);

#if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)

static int
print_irq_inversion_bug(struct task_struct *curr,
			struct lock_list *root, struct lock_list *other,
			struct held_lock *this, int forwards,
			const char *irqclass)
{
	struct lock_list *entry = other;
	struct lock_list *middle = NULL;
	int depth;

	if (!debug_locks_off_graph_unlock() || debug_locks_silent)
		return 0;

	printk("\n");
	printk("=========================================================\n");
	printk("[ INFO: possible irq lock inversion dependency detected ]\n");
	print_kernel_ident();
	printk("---------------------------------------------------------\n");
	printk("%s/%d just changed the state of lock:\n",
		curr->comm, task_pid_nr(curr));
	print_lock(this);
	if (forwards)
		printk("but this lock took another, %s-unsafe lock in the past:\n", irqclass);
	else
		printk("but this lock was taken by another, %s-safe lock in the past:\n", irqclass);
	print_lock_name(other->class);
	printk("\n\nand interrupts could create inverse lock ordering between them.\n\n");

	printk("\nother info that might help us debug this:\n");

	
	depth = get_lock_depth(other);
	do {
		if (depth == 0 && (entry != root)) {
			printk("lockdep:%s bad path found in chain graph\n", __func__);
			break;
		}
		middle = entry;
		entry = get_lock_parent(entry);
		depth--;
	} while (entry && entry != root && (depth >= 0));
	if (forwards)
		print_irq_lock_scenario(root, other,
			middle ? middle->class : root->class, other->class);
	else
		print_irq_lock_scenario(other, root,
			middle ? middle->class : other->class, root->class);

	lockdep_print_held_locks(curr);

	printk("\nthe shortest dependencies between 2nd lock and 1st lock:\n");
	if (!save_trace(&root->trace))
		return 0;
	print_shortest_lock_dependencies(other, root);

	printk("\nstack backtrace:\n");
	dump_stack();

	return 0;
}

static int
check_usage_forwards(struct task_struct *curr, struct held_lock *this,
		     enum lock_usage_bit bit, const char *irqclass)
{
	int ret;
	struct lock_list root;
	struct lock_list *uninitialized_var(target_entry);

	root.parent = NULL;
	root.class = hlock_class(this);
	ret = find_usage_forwards(&root, bit, &target_entry);
	if (ret < 0)
		return print_bfs_bug(ret);
	if (ret == 1)
		return ret;

	return print_irq_inversion_bug(curr, &root, target_entry,
					this, 1, irqclass);
}

static int
check_usage_backwards(struct task_struct *curr, struct held_lock *this,
		      enum lock_usage_bit bit, const char *irqclass)
{
	int ret;
	struct lock_list root;
	struct lock_list *uninitialized_var(target_entry);

	root.parent = NULL;
	root.class = hlock_class(this);
	ret = find_usage_backwards(&root, bit, &target_entry);
	if (ret < 0)
		return print_bfs_bug(ret);
	if (ret == 1)
		return ret;

	return print_irq_inversion_bug(curr, &root, target_entry,
					this, 0, irqclass);
}

void print_irqtrace_events(struct task_struct *curr)
{
	printk("irq event stamp: %u\n", curr->irq_events);
	printk("hardirqs last  enabled at (%u): ", curr->hardirq_enable_event);
	print_ip_sym(curr->hardirq_enable_ip);
	printk("hardirqs last disabled at (%u): ", curr->hardirq_disable_event);
	print_ip_sym(curr->hardirq_disable_ip);
	printk("softirqs last  enabled at (%u): ", curr->softirq_enable_event);
	print_ip_sym(curr->softirq_enable_ip);
	printk("softirqs last disabled at (%u): ", curr->softirq_disable_event);
	print_ip_sym(curr->softirq_disable_ip);
}

static int HARDIRQ_verbose(struct lock_class *class)
{
#if HARDIRQ_VERBOSE
	return class_filter(class);
#endif
	return 0;
}

static int SOFTIRQ_verbose(struct lock_class *class)
{
#if SOFTIRQ_VERBOSE
	return class_filter(class);
#endif
	return 0;
}

static int RECLAIM_FS_verbose(struct lock_class *class)
{
#if RECLAIM_VERBOSE
	return class_filter(class);
#endif
	return 0;
}

#define STRICT_READ_CHECKS	1

static int (*state_verbose_f[])(struct lock_class *class) = {
#define LOCKDEP_STATE(__STATE) \
	__STATE##_verbose,
#include "lockdep_states.h"
#undef LOCKDEP_STATE
};

static inline int state_verbose(enum lock_usage_bit bit,
				struct lock_class *class)
{
	return state_verbose_f[bit >> 2](class);
}

typedef int (*check_usage_f)(struct task_struct *, struct held_lock *,
			     enum lock_usage_bit bit, const char *name);

static int
mark_lock_irq(struct task_struct *curr, struct held_lock *this,
		enum lock_usage_bit new_bit)
{
	int excl_bit = exclusive_bit(new_bit);
	int read = new_bit & 1;
	int dir = new_bit & 2;

	check_usage_f usage = dir ?
		check_usage_backwards : check_usage_forwards;

	if (!valid_state(curr, this, new_bit, excl_bit))
		return 0;

	if ((!read || !dir || STRICT_READ_CHECKS) &&
			!usage(curr, this, excl_bit, state_name(new_bit & ~1)))
		return 0;

	if (!read) {
		if (!valid_state(curr, this, new_bit, excl_bit + 1))
			return 0;

		if (STRICT_READ_CHECKS &&
			!usage(curr, this, excl_bit + 1,
				state_name(new_bit + 1)))
			return 0;
	}

	if (state_verbose(new_bit, hlock_class(this)))
		return 2;

	return 1;
}

enum mark_type {
#define LOCKDEP_STATE(__STATE)	__STATE,
#include "lockdep_states.h"
#undef LOCKDEP_STATE
};

static int
mark_held_locks(struct task_struct *curr, enum mark_type mark)
{
	enum lock_usage_bit usage_bit;
	struct held_lock *hlock;
	int i;

	for (i = 0; i < curr->lockdep_depth; i++) {
		hlock = curr->held_locks + i;

		usage_bit = 2 + (mark << 2); 
		if (hlock->read)
			usage_bit += 1; 

		BUG_ON(usage_bit >= LOCK_USAGE_STATES);

		if (hlock_class(hlock)->key == __lockdep_no_validate__.subkeys)
			continue;

		if (!mark_lock(curr, hlock, usage_bit))
			return 0;
	}

	return 1;
}

static void __trace_hardirqs_on_caller(unsigned long ip)
{
	struct task_struct *curr = current;

	
	curr->hardirqs_enabled = 1;

	if (!mark_held_locks(curr, HARDIRQ))
		return;
	if (curr->softirqs_enabled)
		if (!mark_held_locks(curr, SOFTIRQ))
			return;

	curr->hardirq_enable_ip = ip;
	curr->hardirq_enable_event = ++curr->irq_events;
	debug_atomic_inc(hardirqs_on_events);
}

void trace_hardirqs_on_caller(unsigned long ip)
{
	time_hardirqs_on(CALLER_ADDR0, ip);

	if (unlikely(!debug_locks || current->lockdep_recursion))
		return;

	if (unlikely(current->hardirqs_enabled)) {
		__debug_atomic_inc(redundant_hardirqs_on);
		return;
	}

	if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
		return;

	if (DEBUG_LOCKS_WARN_ON(unlikely(early_boot_irqs_disabled)))
		return;

	if (DEBUG_LOCKS_WARN_ON(current->hardirq_context))
		return;

	current->lockdep_recursion = 1;
	__trace_hardirqs_on_caller(ip);
	current->lockdep_recursion = 0;
}
EXPORT_SYMBOL(trace_hardirqs_on_caller);

void trace_hardirqs_on(void)
{
	trace_hardirqs_on_caller(CALLER_ADDR0);
}
EXPORT_SYMBOL(trace_hardirqs_on);

void trace_hardirqs_off_caller(unsigned long ip)
{
	struct task_struct *curr = current;

	time_hardirqs_off(CALLER_ADDR0, ip);

	if (unlikely(!debug_locks || current->lockdep_recursion))
		return;

	if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
		return;

	if (curr->hardirqs_enabled) {
		curr->hardirqs_enabled = …