Commit 6f2b9b9a authored by Johannes Berg's avatar Johannes Berg Committed by Ingo Molnar
Browse files

timer: implement lockdep deadlock detection 



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: default avatarJohannes Berg <johannes@sipsolutions.net>
parent 673f8205

include/linux/timer.h

+84 −9
Original line number Diff line number Diff line
@@ -5,6 +5,7 @@ 
#include <linux/ktime.h>

#include <linux/stddef.h>

#include <linux/debugobjects.h>

#include <linux/stringify.h>



struct tvec_base;
@@ -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);

}



/**

kernel/timer.c

+57 −11
Original line number Diff line number Diff line
@@ -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)

{
@@ -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);
@@ -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);

}



/**
@@ -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)
@@ -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)
@@ -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"