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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
/*
* lockdep_lock: protects the lockdep graph, the hashes and the
* class/list/hash allocators.
*
* This is one of the rare exceptions where it's justified
* to use a raw spinlock - we really dont want the spinlock
* code to recurse back into the lockdep code...
*/
static arch_spinlock_t lockdep_lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
static int graph_lock(void)
{
arch_spin_lock(&lockdep_lock);
/*
* Make sure that if another CPU detected a bug while
* walking the graph we dont change it (while the other
* CPU is busy printing out stuff with the graph lock
* dropped already)
*/
if (!debug_locks) {
arch_spin_unlock(&lockdep_lock);
return 0;
}
/* prevent any recursions within lockdep from causing deadlocks */
current->lockdep_recursion++;
return 1;
}
static inline int graph_unlock(void)
{
if (debug_locks && !arch_spin_is_locked(&lockdep_lock)) {
/*
* The lockdep graph lock isn't locked while we expect it to
* be, we're confused now, bye!
*/
return DEBUG_LOCKS_WARN_ON(1);
}
current->lockdep_recursion--;
arch_spin_unlock(&lockdep_lock);
return 0;
}
/*
* Turn lock debugging off and return with 0 if it was off already,
* and also release the graph lock:
*/
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];
/*
* All data structures here are protected by the global debug_lock.
*
* Mutex key structs only get allocated, once during bootup, and never
* get freed - this significantly simplifies the debugging code.
*/
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) {
/*
* Someone passed in garbage, we give up.
*/
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
/*
* We keep a global list of all lock classes. The list only grows,
* never shrinks. The list is only accessed with the lockdep
* spinlock lock held.
*/
LIST_HEAD(all_lock_classes);
/*
* The lockdep classes are in a hash-table as well, for fast lookup:
*/
#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];
/*
* We put the lock dependency chains into a hash-table as well, to cache
* their existence:
*/
#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];
/*
* The hash key of the lock dependency chains is a hash itself too:
* it's a hash of all locks taken up to that lock, including that lock.
* It's a 64-bit hash, because it's important for the keys to be
* unique.
*/
#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);
/*
* Debugging switches:
*/
#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
/*
* Quick filtering for interesting events:
*/
static int class_filter(struct lock_class *class)
{
#if 0
/* Example */
if (class->name_version == 1 &&
!strcmp(class->name, "lockname"))
return 1;
if (class->name_version == 1 &&
!strcmp(class->name, "&struct->lockfield"))
return 1;
#endif
/* Filter everything else. 1 would be to allow everything else */
return 0;
}
#endif
static int verbose(struct lock_class *class)
{
#if VERBOSE
return class_filter(class);
#endif
return 0;
}
/*
* Stack-trace: tightly packed array of stack backtrace
* addresses. Protected by the graph_lock.
*/
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);
/*
* Some daft arches put -1 at the end to indicate its a full trace.
*
* <rant> this is buggy anyway, since it takes a whole extra entry so a
* complete trace that maxes out the entries provided will be reported
* as incomplete, friggin useless </rant>
*/
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
/*
* We cannot printk in early bootup code. Not even early_printk()
* might work. So we mark any initialization errors and printk
* about it later on, in lockdep_info().
*/
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,
};
/*
* Various lockdep statistics:
*/
DEFINE_PER_CPU(struct lockdep_stats, lockdep_stats);
#endif
/*
* Locking printouts:
*/
#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;
}
/*
* Is this the address of a static object:
*/
static int static_obj(void *obj)
{
unsigned long start = (unsigned long) &_stext,
end = (unsigned long) &_end,
addr = (unsigned long) obj;
/*
* static variable?
*/
if ((addr >= start) && (addr < end))
return 1;
if (arch_is_kernel_data(addr))
return 1;
/*
* in-kernel percpu var?
*/
if (is_kernel_percpu_address(addr))
return 1;
/*
* module static or percpu var?
*/
return is_module_address(addr) || is_module_percpu_address(addr);
}
/*
* To make lock name printouts unique, we calculate a unique
* class->name_version generation counter:
*/
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;
}
/*
* Register a lock's class in the hash-table, if the class is not present
* yet. Otherwise we look it up. We cache the result in the lock object
* itself, so actual lookup of the hash should be once per lock object.
*/
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 the architecture calls into lockdep before initializing
* the hashes then we'll warn about it later. (we cannot printk
* right now)
*/
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;
}
/*
* Static locks do not have their class-keys yet - for them the key
* is the lock object itself:
*/
if (unlikely(!lock->key))
lock->key = (void *)lock;
/*
* NOTE: the class-key must be unique. For dynamic locks, a static
* lock_class_key variable is passed in through the mutex_init()
* (or spin_lock_init()) call - which acts as the key. For static
* locks we use the lock object itself as the key.
*/
BUILD_BUG_ON(sizeof(struct lock_class_key) >
sizeof(struct lockdep_map));
key = lock->key->subkeys + subclass;
hash_head = classhashentry(key);
/*
* We can walk the hash lockfree, because the hash only
* grows, and we are careful when adding entries to the end:
*/
list_for_each_entry(class, hash_head, hash_entry) {
if (class->key == key) {
/*
* Huh! same key, different name? Did someone trample
* on some memory? We're most confused.
*/
WARN_ON_ONCE(class->name != lock->name);
return class;
}
}
return NULL;
}
/*
* Register a lock's class in the hash-table, if the class is not present
* yet. Otherwise we look it up. We cache the result in the lock object
* itself, so actual lookup of the hash should be once per lock object.
*/
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;
/*
* Debug-check: all keys must be persistent!
*/
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;
}
/*
* We have to do the hash-walk again, to avoid races
* with another CPU:
*/
list_for_each_entry(class, hash_head, hash_entry)
if (class->key == key)
goto out_unlock_set;
/*
* Allocate a new key from the static array, and add it to
* the hash:
*/
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);
/*
* We use RCU's safe list-add method to make
* parallel walking of the hash-list safe:
*/
list_add_tail_rcu(&class->hash_entry, hash_head);
/*
* Add it to the global list of classes:
*/
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;
/*
* Hash collision, did we smoke some? We found a class with a matching
* hash but the subclass -- which is hashed in -- didn't match.
*/
if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))
return NULL;
return class;
}
#ifdef CONFIG_PROVE_LOCKING
/*
* Allocate a lockdep entry. (assumes the graph_lock held, returns
* with NULL on failure)
*/
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++;
}
/*
* Add a new dependency to the head of the list:
*/
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;
/*
* Lock not present yet - get a new dependency struct and
* add it to the list:
*/
entry = alloc_list_entry();
if (!entry)
return 0;
entry->class = this;
entry->distance = distance;
entry->trace = *trace;
/*
* Since we never remove from the dependency list, the list can
* be walked lockless by other CPUs, it's only allocation
* that must be protected by the spinlock. But this also means
* we must make new entries visible only once writes to the
* entry become visible - hence the RCU op:
*/
list_add_tail_rcu(&entry->entry, head);
return 1;
}
/*
* For good efficiency of modular, we use power of 2
*/
#define MAX_CIRCULAR_QUEUE_SIZE 4096UL
#define CQ_MASK (MAX_CIRCULAR_QUEUE_SIZE-1)
/*
* The circular_queue and helpers is used to implement the
* breadth-first search(BFS)algorithem, by which we can build
* the shortest path from the next lock to be acquired to the
* previous held lock if there is a circular between them.
*/
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); /* Out-of-bounds, input fail */
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); /* Out-of-bounds, input fail */
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);
}
/*
* Recursive, forwards-direction lock-dependency checking, used for
* both noncyclic checking and for hardirq-unsafe/softirq-unsafe
* checking.
*/
/*
* Print a dependency chain entry (this is only done when a deadlock
* has been detected):
*/
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;
/*
* A direct locking problem where unsafe_class lock is taken
* directly by safe_class lock, then all we need to show
* is the deadlock scenario, as it is obvious that the
* unsafe lock is taken under the safe lock.
*
* But if there is a chain instead, where the safe lock takes
* an intermediate lock (middle_class) where this lock is
* not the same as the safe lock, then the lock chain is
* used to describe the problem. Otherwise we would need
* to show a different CPU case for each link in the chain
* from the safe_class lock to the unsafe_class lock.
*/
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");
}
/*
* When a circular dependency is detected, print the
* header first:
*/
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;
/*
* Breadth-first-search failed, graph got corrupted?
*/
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;
}
/*
* Prove that the dependency graph starting at <entry> can not
* lead to <target>. Print an error and return 0 if it does.
*/
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)
/*
* Forwards and backwards subgraph searching, for the purposes of
* proving that two subgraphs can be connected by a new dependency
* without creating any illegal irq-safe -> irq-unsafe lock dependency.
*/
static inline int usage_match(struct lock_list *entry, void *bit)
{
return entry->class->usage_mask & (1 << (enum lock_usage_bit)bit);
}
/*
* Find a node in the forwards-direction dependency sub-graph starting
* at @root->class that matches @bit.
*
* Return 0 if such a node exists in the subgraph, and put that node
* into *@target_entry.
*
* Return 1 otherwise and keep *@target_entry unchanged.
* Return <0 on error.
*/
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;
}
/*
* Find a node in the backwards-direction dependency sub-graph starting
* at @root->class that matches @bit.
*
* Return 0 if such a node exists in the subgraph, and put that node
* into *@target_entry.
*
* Return 1 otherwise and keep *@target_entry unchanged.
* Return <0 on error.
*/
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);
}
/*
* printk the shortest lock dependencies from @start to @end in reverse order:
*/
static void __used
print_shortest_lock_dependencies(struct lock_list *leaf,
struct lock_list *root)
{
struct lock_list *entry = leaf;
int depth;
/*compute depth from generated tree by BFS*/
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;
/*
* A direct locking problem where unsafe_class lock is taken
* directly by safe_class lock, then all we need to show
* is the deadlock scenario, as it is obvious that the
* unsafe lock is taken under the safe lock.
*
* But if there is a chain instead, where the safe lock takes
* an intermediate lock (middle_class) where this lock is
* not the same as the safe lock, then the lock chain is
* used to describe the problem. Otherwise we would need
* to show a different CPU case for each link in the chain
* from the safe_class lock to the unsafe_class lock.
*/
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)
{
/*
* USED_IN
* USED_IN_READ
* ENABLED
* ENABLED_READ
*
* bit 0 - write/read
* bit 1 - used_in/enabled
* bit 2+ state
*/
int state = new_bit & ~3;
int dir = new_bit & 2;
/*
* keep state, bit flip the direction and strip read.
*/
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)
{
/*
* Prove that the new dependency does not connect a hardirq-safe
* lock with a hardirq-unsafe lock - to achieve this we search
* the backwards-subgraph starting at <prev>, and the
* forwards-subgraph starting at <next>:
*/
if (!check_usage(curr, prev, next, bit,
exclusive_bit(bit), state_name(bit)))
return 0;
bit++; /* _READ */
/*
* Prove that the new dependency does not connect a hardirq-safe-read
* lock with a hardirq-unsafe lock - to achieve this we search
* the backwards-subgraph starting at <prev>, and the
* forwards-subgraph starting at <next>:
*/
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;
}
/*
* Check whether we are holding such a class already.
*
* (Note that this has to be done separately, because the graph cannot
* detect such classes of deadlocks.)
*
* Returns: 0 on deadlock detected, 1 on OK, 2 on recursive read
*/
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;
/*
* Allow read-after-read recursion of the same
* lock class (i.e. read_lock(lock)+read_lock(lock)):
*/
if ((read == 2) && prev->read)
return 2;
/*
* We're holding the nest_lock, which serializes this lock's
* nesting behaviour.
*/
if (nest)
return 2;
return print_deadlock_bug(curr, prev, next);
}
return 1;
}
/*
* There was a chain-cache miss, and we are about to add a new dependency
* to a previous lock. We recursively validate the following rules:
*
* - would the adding of the <prev> -> <next> dependency create a
* circular dependency in the graph? [== circular deadlock]
*
* - does the new prev->next dependency connect any hardirq-safe lock
* (in the full backwards-subgraph starting at <prev>) with any
* hardirq-unsafe lock (in the full forwards-subgraph starting at
* <next>)? [== illegal lock inversion with hardirq contexts]
*
* - does the new prev->next dependency connect any softirq-safe lock
* (in the full backwards-subgraph starting at <prev>) with any
* softirq-unsafe lock (in the full forwards-subgraph starting at
* <next>)? [== illegal lock inversion with softirq contexts]
*
* any of these scenarios could lead to a deadlock.
*
* Then if all the validations pass, we add the forwards and backwards
* dependency.
*/
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 variable, serialized by the graph_lock().
*
* We use this static variable to save the stack trace in case
* we call into this function multiple times due to encountering
* trylocks in the held lock stack.
*/
static struct stack_trace trace;
/*
* Prove that the new <prev> -> <next> dependency would not
* create a circular dependency in the graph. (We do this by
* forward-recursing into the graph starting at <next>, and
* checking whether we can reach <prev>.)
*
* We are using global variables to control the recursion, to
* keep the stackframe size of the recursive functions low:
*/
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;
/*
* For recursive read-locks we do all the dependency checks,
* but we dont store read-triggered dependencies (only
* write-triggered dependencies). This ensures that only the
* write-side dependencies matter, and that if for example a
* write-lock never takes any other locks, then the reads are
* equivalent to a NOP.
*/
if (next->read == 2 || prev->read == 2)
return 1;
/*
* Is the <prev> -> <next> dependency already present?
*
* (this may occur even though this is a new chain: consider
* e.g. the L1 -> L2 -> L3 -> L4 and the L5 -> L1 -> L2 -> L3
* chains - the second one will be new, but L1 already has
* L2 added to its dependency list, due to the first chain.)
*/
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;
/*
* Ok, all validations passed, add the new lock
* to the previous lock's dependency list:
*/
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;
/*
* Debugging printouts:
*/
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;
}
/*
* Add the dependency to all directly-previous locks that are 'relevant'.
* The ones that are relevant are (in increasing distance from curr):
* all consecutive trylock entries and the final non-trylock entry - or
* the end of this context's lock-chain - whichever comes first.
*/
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;
/*
* Debugging checks.
*
* Depth must not be zero for a non-head lock:
*/
if (!depth)
goto out_bug;
/*
* At least two relevant locks must exist for this
* to be a head:
*/
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;
/*
* Only non-recursive-read entries get new dependencies
* added:
*/
if (hlock->read != 2) {
if (!check_prev_add(curr, hlock, next,
distance, trylock_loop))
return 0;
/*
* Stop after the first non-trylock entry,
* as non-trylock entries have added their
* own direct dependencies already, so this
* lock is connected to them indirectly:
*/
if (!hlock->trylock)
break;
}
depth--;
/*
* End of lock-stack?
*/
if (!depth)
break;
/*
* Stop the search if we cross into another context:
*/
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;
/*
* Clearly we all shouldn't be here, but since we made it we
* can reliable say we messed up our state. See the above two
* gotos for reasons why we could possibly end up here.
*/
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];
}
/*
* Look up a dependency chain. If the key is not present yet then
* add it and return 1 - in this case the new dependency chain is
* validated. If the key is already hashed, return 0.
* (On return with 1 graph_lock is held.)
*/
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;
/*
* We might need to take the graph lock, ensure we've got IRQs
* disabled to make this an IRQ-safe lock.. for recursion reasons
* lockdep won't complain about its own locking errors.
*/
if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
return 0;
/*
* We can walk it lock-free, because entries only get added
* to the hash:
*/
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);
/*
* Allocate a new chain entry from the static array, and add
* it to the hash:
*/
if (!graph_lock())
return 0;
/*
* We have to walk the chain again locked - to avoid duplicates:
*/
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;
/* Find the first held_lock of current chain */
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)
{
/*
* Trylock needs to maintain the stack of held locks, but it
* does not add new dependencies, because trylock can be done
* in any order.
*
* We look up the chain_key and do the O(N^2) check and update of
* the dependencies only if this is a new dependency chain.
* (If lookup_chain_cache() returns with 1 it acquires
* graph_lock for us)
*/
if (!hlock->trylock && (hlock->check == 2) &&
lookup_chain_cache(curr, hlock, chain_key)) {
/*
* Check whether last held lock:
*
* - is irq-safe, if this lock is irq-unsafe
* - is softirq-safe, if this lock is hardirq-unsafe
*
* And check whether the new lock's dependency graph
* could lead back to the previous lock.
*
* any of these scenarios could lead to a deadlock. If
* All validations
*/
int ret = check_deadlock(curr, hlock, lock, hlock->read);
if (!ret)
return 0;
/*
* Mark recursive read, as we jump over it when
* building dependencies (just like we jump over
* trylock entries):
*/
if (ret == 2)
hlock->read = 2;
/*
* Add dependency only if this lock is not the head
* of the chain, and if it's not a secondary read-lock:
*/
if (!chain_head && ret != 2)
if (!check_prevs_add(curr, hlock))
return 0;
graph_unlock();
} else
/* after lookup_chain_cache(): */
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
/*
* We are building curr_chain_key incrementally, so double-check
* it from scratch, to make sure that it's done correctly:
*/
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();
/*
* We got mighty confused, our chain keys don't match
* with what we expect, someone trample on our task state?
*/
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;
/*
* Whoops ran out of static storage again?
*/
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();
/*
* More smoking hash instead of calculating it, damn see these
* numbers float.. I bet that a pink elephant stepped on my memory.
*/
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;
}
/*
* Print out an error if an invalid bit is set:
*/
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)
/*
* print irq inversion bug:
*/
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");
/* Find a middle lock (if one exists) */
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;
}
/*
* Prove that in the forwards-direction subgraph starting at <this>
* there is no lock matching <mask>:
*/
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);
}
/*
* Prove that in the backwards-direction subgraph starting at <this>
* there is no lock matching <mask>:
*/
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;
/*
* mark USED_IN has to look forwards -- to ensure no dependency
* has ENABLED state, which would allow recursion deadlocks.
*
* mark ENABLED has to look backwards -- to ensure no dependee
* has USED_IN state, which, again, would allow recursion deadlocks.
*/
check_usage_f usage = dir ?
check_usage_backwards : check_usage_forwards;
/*
* Validate that this particular lock does not have conflicting
* usage states.
*/
if (!valid_state(curr, this, new_bit, excl_bit))
return 0;
/*
* Validate that the lock dependencies don't have conflicting usage
* states.
*/
if ((!read || !dir || STRICT_READ_CHECKS) &&
!usage(curr, this, excl_bit, state_name(new_bit & ~1)))
return 0;
/*
* Check for read in write conflicts
*/
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
};
/*
* Mark all held locks with a usage bit:
*/
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); /* ENABLED */
if (hlock->read)
usage_bit += 1; /* READ */
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;
}
/*
* Hardirqs will be enabled:
*/
static void __trace_hardirqs_on_caller(unsigned long ip)
{
struct task_struct *curr = current;
/* we'll do an OFF -> ON transition: */
curr->hardirqs_enabled = 1;
/*
* We are going to turn hardirqs on, so set the
* usage bit for all held locks:
*/
if (!mark_held_locks(curr, HARDIRQ))
return;
/*
* If we have softirqs enabled, then set the usage
* bit for all held locks. (disabled hardirqs prevented
* this bit from being set before)
*/
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)) {
/*
* Neither irq nor preemption are disabled here
* so this is racy by nature but losing one hit
* in a stat is not a big deal.
*/
__debug_atomic_inc(redundant_hardirqs_on);
return;
}
/*
* We're enabling irqs and according to our state above irqs weren't
* already enabled, yet we find the hardware thinks they are in fact
* enabled.. someone messed up their IRQ state tracing.
*/
if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
return;
/*
* See the fine text that goes along with this variable definition.
*/
if (DEBUG_LOCKS_WARN_ON(unlikely(early_boot_irqs_disabled)))
return;
/*
* Can't allow enabling interrupts while in an interrupt handler,
* that's general bad form and such. Recursion, limited stack etc..
*/
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);
/*
* Hardirqs were disabled:
*/
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;
/*
* So we're supposed to get called after you mask local IRQs, but for
* some reason the hardware doesn't quite think you did a proper job.
*/
if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
return;
if (curr->hardirqs_enabled) {
/*
* We have done an ON -> OFF transition:
*/
curr->hardirqs_enabled = 0;
curr->hardirq_disable_ip = ip;
curr->hardirq_disable_event = ++curr->irq_events;
debug_atomic_inc(hardirqs_off_events);
} else
debug_atomic_inc(redundant_hardirqs_off);
}
EXPORT_SYMBOL(trace_hardirqs_off_caller);
void trace_hardirqs_off(void)
{
trace_hardirqs_off_caller(CALLER_ADDR0);
}
EXPORT_SYMBOL(trace_hardirqs_off);
/*
* Softirqs will be enabled:
*/
void trace_softirqs_on(unsigned long ip)
{
struct task_struct *curr = current;
if (unlikely(!debug_locks || current->lockdep_recursion))
return;
/*
* We fancy IRQs being disabled here, see softirq.c, avoids
* funny state and nesting things.
*/
if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
return;
if (curr->softirqs_enabled) {
debug_atomic_inc(redundant_softirqs_on);
return;
}
current->lockdep_recursion = 1;
/*
* We'll do an OFF -> ON transition:
*/
curr->softirqs_enabled = 1;
curr->softirq_enable_ip = ip;
curr->softirq_enable_event = ++curr->irq_events;
debug_atomic_inc(softirqs_on_events);
/*
* We are going to turn softirqs on, so set the
* usage bit for all held locks, if hardirqs are
* enabled too:
*/
if (curr->hardirqs_enabled)
mark_held_locks(curr, SOFTIRQ);
current->lockdep_recursion = 0;
}
/*
* Softirqs were disabled:
*/
void trace_softirqs_off(unsigned long ip)
{
struct task_struct *curr = current;
if (unlikely(!debug_locks || current->lockdep_recursion))
return;
/*
* We fancy IRQs being disabled here, see softirq.c
*/
if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
return;
if (curr->softirqs_enabled) {
/*
* We have done an ON -> OFF transition:
*/
curr->softirqs_enabled = 0;
curr->softirq_disable_ip = ip;
curr->softirq_disable_event = ++curr->irq_events;
debug_atomic_inc(softirqs_off_events);
/*
* Whoops, we wanted softirqs off, so why aren't they?
*/
DEBUG_LOCKS_WARN_ON(!softirq_count());
} else
debug_atomic_inc(redundant_softirqs_off);
}
static void __lockdep_trace_alloc(gfp_t gfp_mask, unsigned long flags)
{
struct task_struct *curr = current;
if (unlikely(!debug_locks))
return;
/* no reclaim without waiting on it */
if (!(gfp_mask & __GFP_WAIT))
return;
/* this guy won't enter reclaim */
if ((curr->flags & PF_MEMALLOC) && !(gfp_mask & __GFP_NOMEMALLOC))
return;
/* We're only interested __GFP_FS allocations for now */
if (!(gfp_mask & __GFP_FS))
return;
/*
* Oi! Can't be having __GFP_FS allocations with IRQs disabled.
*/
if (DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags)))
return;
mark_held_locks(curr, RECLAIM_FS);
}
static void check_flags(unsigned long flags);
void lockdep_trace_alloc(gfp_t gfp_mask)
{
unsigned long flags;
if (unlikely(current->lockdep_recursion))
return;
raw_local_irq_save(flags);
check_flags(flags);
current->lockdep_recursion = 1;
__lockdep_trace_alloc(gfp_mask, flags);
current->lockdep_recursion = 0;
raw_local_irq_restore(flags);
}
static int mark_irqflags(struct task_struct *curr, struct held_lock *hlock)
{
/*
* If non-trylock use in a hardirq or softirq context, then
* mark the lock as used in these contexts:
*/
if (!hlock->trylock) {
if (hlock->read) {
if (curr->hardirq_context)
if (!mark_lock(curr, hlock,
LOCK_USED_IN_HARDIRQ_READ))
return 0;
if (curr->softirq_context)
if (!mark_lock(curr, hlock,
LOCK_USED_IN_SOFTIRQ_READ))
return 0;
} else {
if (curr->hardirq_context)
if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ))
return 0;
if (curr->softirq_context)
if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ))
return 0;
}
}
if (!hlock->hardirqs_off) {
if (hlock->read) {
if (!mark_lock(curr, hlock,
LOCK_ENABLED_HARDIRQ_READ))
return 0;
if (curr->softirqs_enabled)
if (!mark_lock(curr, hlock,
LOCK_ENABLED_SOFTIRQ_READ))
return 0;
} else {
if (!mark_lock(curr, hlock,
LOCK_ENABLED_HARDIRQ))
return 0;
if (curr->softirqs_enabled)
if (!mark_lock(curr, hlock,
LOCK_ENABLED_SOFTIRQ))
return 0;
}
}
/*
* We reuse the irq context infrastructure more broadly as a general
* context checking code. This tests GFP_FS recursion (a lock taken
* during reclaim for a GFP_FS allocation is held over a GFP_FS
* allocation).
*/
if (!hlock->trylock && (curr->lockdep_reclaim_gfp & __GFP_FS)) {
if (hlock->read) {
if (!mark_lock(curr, hlock, LOCK_USED_IN_RECLAIM_FS_READ))
return 0;
} else {
if (!mark_lock(curr, hlock, LOCK_USED_IN_RECLAIM_FS))
return 0;
}
}
return 1;
}
static int separate_irq_context(struct task_struct *curr,
struct held_lock *hlock)
{
unsigned int depth = curr->lockdep_depth;
/*
* Keep track of points where we cross into an interrupt context:
*/
hlock->irq_context = 2*(curr->hardirq_context ? 1 : 0) +
curr->softirq_context;
if (depth) {
struct held_lock *prev_hlock;
prev_hlock = curr->held_locks + depth-1;
/*
* If we cross into another context, reset the
* hash key (this also prevents the checking and the
* adding of the dependency to 'prev'):
*/
if (prev_hlock->irq_context != hlock->irq_context)
return 1;
}
return 0;
}
#else /* defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING) */
static inline
int mark_lock_irq(struct task_struct *curr, struct held_lock *this,
enum lock_usage_bit new_bit)
{
WARN_ON(1); /* Impossible innit? when we don't have TRACE_IRQFLAG */
return 1;
}
static inline int mark_irqflags(struct task_struct *curr,
struct held_lock *hlock)
{
return 1;
}
static inline int separate_irq_context(struct task_struct *curr,
struct held_lock *hlock)
{
return 0;
}
void lockdep_trace_alloc(gfp_t gfp_mask)
{
}
#endif /* defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING) */
/*
* Mark a lock with a usage bit, and validate the state transition:
*/
static int mark_lock(struct task_struct *curr, struct held_lock *this,
enum lock_usage_bit new_bit)
{
unsigned int new_mask = 1 << new_bit, ret = 1;
/*
* If already set then do not dirty the cacheline,
* nor do any checks:
*/
if (likely(hlock_class(this)->usage_mask & new_mask))
return 1;
if (!graph_lock())
return 0;
/*
* Make sure we didn't race:
*/
if (unlikely(hlock_class(this)->usage_mask & new_mask)) {
graph_unlock();
return 1;
}
hlock_class(this)->usage_mask |= new_mask;
if (!save_trace(hlock_class(this)->usage_traces + new_bit))
return 0;
switch (new_bit) {
#define LOCKDEP_STATE(__STATE) \
case LOCK_USED_IN_##__STATE: \
case LOCK_USED_IN_##__STATE##_READ: \
case LOCK_ENABLED_##__STATE: \
case LOCK_ENABLED_##__STATE##_READ:
#include "lockdep_states.h"
#undef LOCKDEP_STATE
ret = mark_lock_irq(curr, this, new_bit);
if (!ret)
return 0;
break;
case LOCK_USED:
debug_atomic_dec(nr_unused_locks);
break;
default:
if (!debug_locks_off_graph_unlock())
return 0;
WARN_ON(1);
return 0;
}
graph_unlock();
/*
* We must printk outside of the graph_lock:
*/
if (ret == 2) {
printk("\nmarked lock as {%s}:\n", usage_str[new_bit]);
print_lock(this);
print_irqtrace_events(curr);
dump_stack();
}
return ret;
}
/*
* Initialize a lock instance's lock-class mapping info:
*/
void lockdep_init_map(struct lockdep_map *lock, const char *name,
struct lock_class_key *key, int subclass)
{
int i;
kmemcheck_mark_initialized(lock, sizeof(*lock));
for (i = 0; i < NR_LOCKDEP_CACHING_CLASSES; i++)
lock->class_cache[i] = NULL;
#ifdef CONFIG_LOCK_STAT
lock->cpu = raw_smp_processor_id();
#endif
/*
* Can't be having no nameless bastards around this place!
*/
if (DEBUG_LOCKS_WARN_ON(!name)) {
lock->name = "NULL";
return;
}
lock->name = name;
/*
* No key, no joy, we need to hash something.
*/
if (DEBUG_LOCKS_WARN_ON(!key))
return;
/*
* Sanity check, the lock-class key must be persistent:
*/
if (!static_obj(key)) {
printk("BUG: key %p not in .data!\n", key);
/*
* What it says above ^^^^^, I suggest you read it.
*/
DEBUG_LOCKS_WARN_ON(1);
return;
}
lock->key = key;
if (unlikely(!debug_locks))
return;
if (subclass)
register_lock_class(lock, subclass, 1);
}
EXPORT_SYMBOL_GPL(lockdep_init_map);
struct lock_class_key __lockdep_no_validate__;
static int
print_lock_nested_lock_not_held(struct task_struct *curr,
struct held_lock *hlock,
unsigned long ip)
{
if (!debug_locks_off())
return 0;
if (debug_locks_silent)
return 0;
printk("\n");
printk("==================================\n");
printk("[ BUG: Nested lock was not taken ]\n");
print_kernel_ident();
printk("----------------------------------\n");
printk("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr));
print_lock(hlock);
printk("\nbut this task is not holding:\n");
printk("%s\n", hlock->nest_lock->name);
printk("\nstack backtrace:\n");
dump_stack();
printk("\nother info that might help us debug this:\n");
lockdep_print_held_locks(curr);
printk("\nstack backtrace:\n");
dump_stack();
return 0;
}
static int __lock_is_held(struct lockdep_map *lock);
/*
* This gets called for every mutex_lock*()/spin_lock*() operation.
* We maintain the dependency maps and validate the locking attempt:
*/
static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
int trylock, int read, int check, int hardirqs_off,
struct lockdep_map *nest_lock, unsigned long ip,
int references)
{
struct task_struct *curr = current;
struct lock_class *class = NULL;
struct held_lock *hlock;
unsigned int depth, id;
int chain_head = 0;
int class_idx;
u64 chain_key;
if (!prove_locking)
check = 1;
if (unlikely(!debug_locks))
return 0;
/*
* Lockdep should run with IRQs disabled, otherwise we could
* get an interrupt which would want to take locks, which would
* end up in lockdep and have you got a head-ache already?
*/
if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
return 0;
if (lock->key == &__lockdep_no_validate__)
check = 1;
if (subclass < NR_LOCKDEP_CACHING_CLASSES)
class = lock->class_cache[subclass];
/*
* Not cached?
*/
if (unlikely(!class)) {
class = register_lock_class(lock, subclass, 0);
if (!class)
return 0;
}
atomic_inc((atomic_t *)&class->ops);
if (very_verbose(class)) {
printk("\nacquire class [%p] %s", class->key, class->name);
if (class->name_version > 1)
printk("#%d", class->name_version);
printk("\n");
dump_stack();
}
/*
* Add the lock to the list of currently held locks.
* (we dont increase the depth just yet, up until the
* dependency checks are done)
*/
depth = curr->lockdep_depth;
/*
* Ran out of static storage for our per-task lock stack again have we?
*/
if (DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH))
return 0;
class_idx = class - lock_classes + 1;
if (depth) {
hlock = curr->held_locks + depth - 1;
if (hlock->class_idx == class_idx && nest_lock) {
if (hlock->references)
hlock->references++;
else
hlock->references = 2;
return 1;
}
}
hlock = curr->held_locks + depth;
/*
* Plain impossible, we just registered it and checked it weren't no
* NULL like.. I bet this mushroom I ate was good!
*/
if (DEBUG_LOCKS_WARN_ON(!class))
return 0;
hlock->class_idx = class_idx;
hlock->acquire_ip = ip;
hlock->instance = lock;
hlock->nest_lock = nest_lock;
hlock->trylock = trylock;
hlock->read = read;
hlock->check = check;
hlock->hardirqs_off = !!hardirqs_off;
hlock->references = references;
#ifdef CONFIG_LOCK_STAT
hlock->waittime_stamp = 0;
hlock->holdtime_stamp = lockstat_clock();
#endif
if (check == 2 && !mark_irqflags(curr, hlock))
return 0;
/* mark it as used: */
if (!mark_lock(curr, hlock, LOCK_USED))
return 0;
/*
* Calculate the chain hash: it's the combined hash of all the
* lock keys along the dependency chain. We save the hash value
* at every step so that we can get the current hash easily
* after unlock. The chain hash is then used to cache dependency
* results.
*
* The 'key ID' is what is the most compact key value to drive
* the hash, not class->key.
*/
id = class - lock_classes;
/*
* Whoops, we did it again.. ran straight out of our static allocation.
*/
if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
return 0;
chain_key = curr->curr_chain_key;
if (!depth) {
/*
* How can we have a chain hash when we ain't got no keys?!
*/
if (DEBUG_LOCKS_WARN_ON(chain_key != 0))
return 0;
chain_head = 1;
}
hlock->prev_chain_key = chain_key;
if (separate_irq_context(curr, hlock)) {
chain_key = 0;
chain_head = 1;
}
chain_key = iterate_chain_key(chain_key, id);
if (nest_lock && !__lock_is_held(nest_lock))
return print_lock_nested_lock_not_held(curr, hlock, ip);
if (!validate_chain(curr, lock, hlock, chain_head, chain_key))
return 0;
curr->curr_chain_key = chain_key;
curr->lockdep_depth++;
check_chain_key(curr);
#ifdef CONFIG_DEBUG_LOCKDEP
if (unlikely(!debug_locks))
return 0;
#endif
if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
debug_locks_off();
printk("BUG: MAX_LOCK_DEPTH too low!\n");
printk("turning off the locking correctness validator.\n");
dump_stack();
return 0;
}
if (unlikely(curr->lockdep_depth > max_lockdep_depth))
max_lockdep_depth = curr->lockdep_depth;
return 1;
}
static int
print_unlock_inbalance_bug(struct task_struct *curr, struct lockdep_map *lock,
unsigned long ip)
{
if (!debug_locks_off())
return 0;
if (debug_locks_silent)
return 0;
printk("\n");
printk("=====================================\n");
printk("[ BUG: bad unlock balance detected! ]\n");
print_kernel_ident();
printk("-------------------------------------\n");
printk("%s/%d is trying to release lock (",
curr->comm, task_pid_nr(curr));
print_lockdep_cache(lock);
printk(") at:\n");
print_ip_sym(ip);
printk("but there are no more locks to release!\n");
printk("\nother info that might help us debug this:\n");
lockdep_print_held_locks(curr);
printk("\nstack backtrace:\n");
dump_stack();
return 0;
}
/*
* Common debugging checks for both nested and non-nested unlock:
*/
static int check_unlock(struct task_struct *curr, struct lockdep_map *lock,
unsigned long ip)
{
if (unlikely(!debug_locks))
return 0;
/*
* Lockdep should run with IRQs disabled, recursion, head-ache, etc..
*/
if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
return 0;
if (curr->lockdep_depth <= 0)
return print_unlock_inbalance_bug(curr, lock, ip);
return 1;
}
static int match_held_lock(struct held_lock *hlock, struct lockdep_map *lock)
{
if (hlock->instance == lock)
return 1;
if (hlock->references) {
struct lock_class *class = lock->class_cache[0];
if (!class)
class = look_up_lock_class(lock, 0);
/*
* If look_up_lock_class() failed to find a class, we're trying
* to test if we hold a lock that has never yet been acquired.
* Clearly if the lock hasn't been acquired _ever_, we're not
* holding it either, so report failure.
*/
if (!class)
return 0;
/*
* References, but not a lock we're actually ref-counting?
* State got messed up, follow the sites that change ->references
* and try to make sense of it.
*/
if (DEBUG_LOCKS_WARN_ON(!hlock->nest_lock))
return 0;
if (hlock->class_idx == class - lock_classes + 1)
return 1;
}
return 0;
}
static int
__lock_set_class(struct lockdep_map *lock, const char *name,
struct lock_class_key *key, unsigned int subclass,
unsigned long ip)
{
struct task_struct *curr = current;
struct held_lock *hlock, *prev_hlock;
struct lock_class *class;
unsigned int depth;
int i;
depth = curr->lockdep_depth;
/*
* This function is about (re)setting the class of a held lock,
* yet we're not actually holding any locks. Naughty user!
*/
if (DEBUG_LOCKS_WARN_ON(!depth))
return 0;
prev_hlock = NULL;
for (i = depth-1; i >= 0; i--) {
hlock = curr->held_locks + i;
/*
* We must not cross into another context:
*/
if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
break;
if (match_held_lock(hlock, lock))
goto found_it;
prev_hlock = hlock;
}
return print_unlock_inbalance_bug(curr, lock, ip);
found_it:
lockdep_init_map(lock, name, key, 0);
class = register_lock_class(lock, subclass, 0);
hlock->class_idx = class - lock_classes + 1;
curr->lockdep_depth = i;
curr->curr_chain_key = hlock->prev_chain_key;
for (; i < depth; i++) {
hlock = curr->held_locks + i;
if (!__lock_acquire(hlock->instance,
hlock_class(hlock)->subclass, hlock->trylock,
hlock->read, hlock->check, hlock->hardirqs_off,
hlock->nest_lock, hlock->acquire_ip,
hlock->references))
return 0;
}
/*
* I took it apart and put it back together again, except now I have
* these 'spare' parts.. where shall I put them.
*/
if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth))
return 0;
return 1;
}
/*
* Remove the lock to the list of currently held locks in a
* potentially non-nested (out of order) manner. This is a
* relatively rare operation, as all the unlock APIs default
* to nested mode (which uses lock_release()):
*/
static int
lock_release_non_nested(struct task_struct *curr,
struct lockdep_map *lock, unsigned long ip)
{
struct held_lock *hlock, *prev_hlock;
unsigned int depth;
int i;
/*
* Check whether the lock exists in the current stack
* of held locks:
*/
depth = curr->lockdep_depth;
/*
* So we're all set to release this lock.. wait what lock? We don't
* own any locks, you've been drinking again?
*/
if (DEBUG_LOCKS_WARN_ON(!depth))
return 0;
prev_hlock = NULL;
for (i = depth-1; i >= 0; i--) {
hlock = curr->held_locks + i;
/*
* We must not cross into another context:
*/
if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
break;
if (match_held_lock(hlock, lock))
goto found_it;
prev_hlock = hlock;
}
return print_unlock_inbalance_bug(curr, lock, ip);
found_it:
if (hlock->instance == lock)
lock_release_holdtime(hlock);
if (hlock->references) {
hlock->references--;
if (hlock->references) {
/*
* We had, and after removing one, still have
* references, the current lock stack is still
* valid. We're done!
*/
return 1;
}
}
/*
* We have the right lock to unlock, 'hlock' points to it.
* Now we remove it from the stack, and add back the other
* entries (if any), recalculating the hash along the way:
*/
curr->lockdep_depth = i;
curr->curr_chain_key = hlock->prev_chain_key;
for (i++; i < depth; i++) {
hlock = curr->held_locks + i;
if (!__lock_acquire(hlock->instance,
hlock_class(hlock)->subclass, hlock->trylock,
hlock->read, hlock->check, hlock->hardirqs_off,
hlock->nest_lock, hlock->acquire_ip,
hlock->references))
return 0;
}
/*
* We had N bottles of beer on the wall, we drank one, but now
* there's not N-1 bottles of beer left on the wall...
*/
if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - 1))
return 0;
return 1;
}
/*
* Remove the lock to the list of currently held locks - this gets
* called on mutex_unlock()/spin_unlock*() (or on a failed
* mutex_lock_interruptible()). This is done for unlocks that nest
* perfectly. (i.e. the current top of the lock-stack is unlocked)
*/
static int lock_release_nested(struct task_struct *curr,
struct lockdep_map *lock, unsigned long ip)
{
struct held_lock *hlock;
unsigned int depth;
/*
* Pop off the top of the lock stack:
*/
depth = curr->lockdep_depth - 1;
hlock = curr->held_locks + depth;
/*
* Is the unlock non-nested:
*/
if (hlock->instance != lock || hlock->references)
return lock_release_non_nested(curr, lock, ip);
curr->lockdep_depth--;
/*
* No more locks, but somehow we've got hash left over, who left it?
*/
if (DEBUG_LOCKS_WARN_ON(!depth && (hlock->prev_chain_key != 0)))
return 0;
curr->curr_chain_key = hlock->prev_chain_key;
lock_release_holdtime(hlock);
#ifdef CONFIG_DEBUG_LOCKDEP
hlock->prev_chain_key = 0;
hlock->class_idx = 0;
hlock->acquire_ip = 0;
hlock->irq_context = 0;
#endif
return 1;
}
/*
* Remove the lock to the list of currently held locks - this gets
* called on mutex_unlock()/spin_unlock*() (or on a failed
* mutex_lock_interruptible()). This is done for unlocks that nest
* perfectly. (i.e. the current top of the lock-stack is unlocked)
*/
static void
__lock_release(struct lockdep_map *lock, int nested, unsigned long ip)
{
struct task_struct *curr = current;
if (!check_unlock(curr, lock, ip))
return;
if (nested) {
if (!lock_release_nested(curr, lock, ip))
return;
} else {
if (!lock_release_non_nested(curr, lock, ip))
return;
}
check_chain_key(curr);
}
static int __lock_is_held(struct lockdep_map *lock)
{
struct task_struct *curr = current;
int i;
for (i = 0; i < curr->lockdep_depth; i++) {
struct held_lock *hlock = curr->held_locks + i;
if (match_held_lock(hlock, lock))
return 1;
}
return 0;
}
/*
* Check whether we follow the irq-flags state precisely:
*/
static void check_flags(unsigned long flags)
{
#if defined(CONFIG_PROVE_LOCKING) && defined(CONFIG_DEBUG_LOCKDEP) && \
defined(CONFIG_TRACE_IRQFLAGS)
if (!debug_locks)
return;
if (irqs_disabled_flags(flags)) {
if (DEBUG_LOCKS_WARN_ON(current->hardirqs_enabled)) {
printk("possible reason: unannotated irqs-off.\n");
}
} else {
if (DEBUG_LOCKS_WARN_ON(!current->hardirqs_enabled)) {
printk("possible reason: unannotated irqs-on.\n");
}
}
/*
* We dont accurately track softirq state in e.g.
* hardirq contexts (such as on 4KSTACKS), so only
* check if not in hardirq contexts:
*/
if (!hardirq_count()) {
if (softirq_count()) {
/* like the above, but with softirqs */
DEBUG_LOCKS_WARN_ON(current->softirqs_enabled);
} else {
/* lick the above, does it taste good? */
DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled);
}
}
if (!debug_locks)
print_irqtrace_events(current);
#endif
}
void lock_set_class(struct lockdep_map *lock, const char *name,
struct lock_class_key *key, unsigned int subclass,
unsigned long ip)
{
unsigned long flags;
if (unlikely(current->lockdep_recursion))
return;
raw_local_irq_save(flags);
current->lockdep_recursion = 1;
check_flags(flags);
if (__lock_set_class(lock, name, key, subclass, ip))
check_chain_key(current);
current->lockdep_recursion = 0;
raw_local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(lock_set_class);
/*
* We are not always called with irqs disabled - do that here,
* and also avoid lockdep recursion:
*/
void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
int trylock, int read, int check,
struct lockdep_map *nest_lock, unsigned long ip)
{
unsigned long flags;
if (unlikely(current->lockdep_recursion))
return;
raw_local_irq_save(flags);
check_flags(flags);
current->lockdep_recursion = 1;
trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip);
__lock_acquire(lock, subclass, trylock, read, check,
irqs_disabled_flags(flags), nest_lock, ip, 0);
current->lockdep_recursion = 0;
raw_local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(lock_acquire);
void lock_release(struct lockdep_map *lock, int nested,
unsigned long ip)
{
unsigned long flags;
if (unlikely(current->lockdep_recursion))
return;
raw_local_irq_save(flags);
check_flags(flags);
current->lockdep_recursion = 1;
trace_lock_release(lock, ip);
__lock_release(lock, nested, ip);
current->lockdep_recursion = 0;
raw_local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(lock_release);
int lock_is_held(struct lockdep_map *lock)
{
unsigned long flags;
int ret = 0;
if (unlikely(current->lockdep_recursion))