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timer: implement lockdep deadlock detection
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This modifies the timer code in a way to allow lockdep to detect
deadlocks resulting from a lock being taken in the timer function
as well as around the del_timer_sync() call.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
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Johannes Berg authored and Ingo Molnar committed Feb 14, 2009
1 parent 673f820 commit 6f2b9b9
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Showing 2 changed files with 141 additions and 20 deletions.
93 changes: 84 additions & 9 deletions include/linux/timer.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@
#include <linux/ktime.h>
#include <linux/stddef.h>
#include <linux/debugobjects.h>
#include <linux/stringify.h>

struct tvec_base;

Expand All @@ -21,52 +22,126 @@ struct timer_list {
char start_comm[16];
int start_pid;
#endif
#ifdef CONFIG_LOCKDEP
struct lockdep_map lockdep_map;
#endif
};

extern struct tvec_base boot_tvec_bases;

#ifdef CONFIG_LOCKDEP
/*
* NB: because we have to copy the lockdep_map, setting the lockdep_map key
* (second argument) here is required, otherwise it could be initialised to
* the copy of the lockdep_map later! We use the pointer to and the string
* "<file>:<line>" as the key resp. the name of the lockdep_map.
*/
#define __TIMER_LOCKDEP_MAP_INITIALIZER(_kn) \
.lockdep_map = STATIC_LOCKDEP_MAP_INIT(_kn, &_kn),
#else
#define __TIMER_LOCKDEP_MAP_INITIALIZER(_kn)
#endif

#define TIMER_INITIALIZER(_function, _expires, _data) { \
.entry = { .prev = TIMER_ENTRY_STATIC }, \
.function = (_function), \
.expires = (_expires), \
.data = (_data), \
.base = &boot_tvec_bases, \
__TIMER_LOCKDEP_MAP_INITIALIZER( \
__FILE__ ":" __stringify(__LINE__)) \
}

#define DEFINE_TIMER(_name, _function, _expires, _data) \
struct timer_list _name = \
TIMER_INITIALIZER(_function, _expires, _data)

void init_timer(struct timer_list *timer);
void init_timer_deferrable(struct timer_list *timer);
void init_timer_key(struct timer_list *timer,
const char *name,
struct lock_class_key *key);
void init_timer_deferrable_key(struct timer_list *timer,
const char *name,
struct lock_class_key *key);

#ifdef CONFIG_LOCKDEP
#define init_timer(timer) \
do { \
static struct lock_class_key __key; \
init_timer_key((timer), #timer, &__key); \
} while (0)

#define init_timer_deferrable(timer) \
do { \
static struct lock_class_key __key; \
init_timer_deferrable_key((timer), #timer, &__key); \
} while (0)

#define init_timer_on_stack(timer) \
do { \
static struct lock_class_key __key; \
init_timer_on_stack_key((timer), #timer, &__key); \
} while (0)

#define setup_timer(timer, fn, data) \
do { \
static struct lock_class_key __key; \
setup_timer_key((timer), #timer, &__key, (fn), (data));\
} while (0)

#define setup_timer_on_stack(timer, fn, data) \
do { \
static struct lock_class_key __key; \
setup_timer_on_stack_key((timer), #timer, &__key, \
(fn), (data)); \
} while (0)
#else
#define init_timer(timer)\
init_timer_key((timer), NULL, NULL)
#define init_timer_deferrable(timer)\
init_timer_deferrable_key((timer), NULL, NULL)
#define init_timer_on_stack(timer)\
init_timer_on_stack_key((timer), NULL, NULL)
#define setup_timer(timer, fn, data)\
setup_timer_key((timer), NULL, NULL, (fn), (data))
#define setup_timer_on_stack(timer, fn, data)\
setup_timer_on_stack_key((timer), NULL, NULL, (fn), (data))
#endif

#ifdef CONFIG_DEBUG_OBJECTS_TIMERS
extern void init_timer_on_stack(struct timer_list *timer);
extern void init_timer_on_stack_key(struct timer_list *timer,
const char *name,
struct lock_class_key *key);
extern void destroy_timer_on_stack(struct timer_list *timer);
#else
static inline void destroy_timer_on_stack(struct timer_list *timer) { }
static inline void init_timer_on_stack(struct timer_list *timer)
static inline void init_timer_on_stack_key(struct timer_list *timer,
const char *name,
struct lock_class_key *key)
{
init_timer(timer);
init_timer_key(timer, name, key);
}
#endif

static inline void setup_timer(struct timer_list * timer,
static inline void setup_timer_key(struct timer_list * timer,
const char *name,
struct lock_class_key *key,
void (*function)(unsigned long),
unsigned long data)
{
timer->function = function;
timer->data = data;
init_timer(timer);
init_timer_key(timer, name, key);
}

static inline void setup_timer_on_stack(struct timer_list *timer,
static inline void setup_timer_on_stack_key(struct timer_list *timer,
const char *name,
struct lock_class_key *key,
void (*function)(unsigned long),
unsigned long data)
{
timer->function = function;
timer->data = data;
init_timer_on_stack(timer);
init_timer_on_stack_key(timer, name, key);
}

/**
Expand Down
68 changes: 57 additions & 11 deletions kernel/timer.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -491,14 +491,18 @@ static inline void debug_timer_free(struct timer_list *timer)
debug_object_free(timer, &timer_debug_descr);
}

static void __init_timer(struct timer_list *timer);
static void __init_timer(struct timer_list *timer,
const char *name,
struct lock_class_key *key);

void init_timer_on_stack(struct timer_list *timer)
void init_timer_on_stack_key(struct timer_list *timer,
const char *name,
struct lock_class_key *key)
{
debug_object_init_on_stack(timer, &timer_debug_descr);
__init_timer(timer);
__init_timer(timer, name, key);
}
EXPORT_SYMBOL_GPL(init_timer_on_stack);
EXPORT_SYMBOL_GPL(init_timer_on_stack_key);

void destroy_timer_on_stack(struct timer_list *timer)
{
Expand All @@ -512,7 +516,9 @@ static inline void debug_timer_activate(struct timer_list *timer) { }
static inline void debug_timer_deactivate(struct timer_list *timer) { }
#endif

static void __init_timer(struct timer_list *timer)
static void __init_timer(struct timer_list *timer,
const char *name,
struct lock_class_key *key)
{
timer->entry.next = NULL;
timer->base = __raw_get_cpu_var(tvec_bases);
Expand All @@ -521,6 +527,7 @@ static void __init_timer(struct timer_list *timer)
timer->start_pid = -1;
memset(timer->start_comm, 0, TASK_COMM_LEN);
#endif
lockdep_init_map(&timer->lockdep_map, name, key, 0);
}

/**
Expand All @@ -530,19 +537,23 @@ static void __init_timer(struct timer_list *timer)
* init_timer() must be done to a timer prior calling *any* of the
* other timer functions.
*/
void init_timer(struct timer_list *timer)
void init_timer_key(struct timer_list *timer,
const char *name,
struct lock_class_key *key)
{
debug_timer_init(timer);
__init_timer(timer);
__init_timer(timer, name, key);
}
EXPORT_SYMBOL(init_timer);
EXPORT_SYMBOL(init_timer_key);

void init_timer_deferrable(struct timer_list *timer)
void init_timer_deferrable_key(struct timer_list *timer,
const char *name,
struct lock_class_key *key)
{
init_timer(timer);
init_timer_key(timer, name, key);
timer_set_deferrable(timer);
}
EXPORT_SYMBOL(init_timer_deferrable);
EXPORT_SYMBOL(init_timer_deferrable_key);

static inline void detach_timer(struct timer_list *timer,
int clear_pending)
Expand Down Expand Up @@ -789,6 +800,15 @@ EXPORT_SYMBOL(try_to_del_timer_sync);
*/
int del_timer_sync(struct timer_list *timer)
{
#ifdef CONFIG_LOCKDEP
unsigned long flags;

local_irq_save(flags);
lock_map_acquire(&timer->lockdep_map);
lock_map_release(&timer->lockdep_map);
local_irq_restore(flags);
#endif

for (;;) {
int ret = try_to_del_timer_sync(timer);
if (ret >= 0)
Expand Down Expand Up @@ -861,10 +881,36 @@ static inline void __run_timers(struct tvec_base *base)

set_running_timer(base, timer);
detach_timer(timer, 1);

spin_unlock_irq(&base->lock);
{
int preempt_count = preempt_count();

#ifdef CONFIG_LOCKDEP
/*
* It is permissible to free the timer from
* inside the function that is called from
* it, this we need to take into account for
* lockdep too. To avoid bogus "held lock
* freed" warnings as well as problems when
* looking into timer->lockdep_map, make a
* copy and use that here.
*/
struct lockdep_map lockdep_map =
timer->lockdep_map;
#endif
/*
* Couple the lock chain with the lock chain at
* del_timer_sync() by acquiring the lock_map
* around the fn() call here and in
* del_timer_sync().
*/
lock_map_acquire(&lockdep_map);

fn(data);

lock_map_release(&lockdep_map);

if (preempt_count != preempt_count()) {
printk(KERN_ERR "huh, entered %p "
"with preempt_count %08x, exited"
Expand Down

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