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Commit cd8084f9 authored by Byungchul Park's avatar Byungchul Park Committed by Ingo Molnar
Browse files

locking/lockdep: Apply crossrelease to completions 



Although wait_for_completion() and its family can cause deadlock, the
lock correctness validator could not be applied to them until now,
because things like complete() are usually called in a different context
from the waiting context, which violates lockdep's assumption.

Thanks to CONFIG_LOCKDEP_CROSSRELEASE, we can now apply the lockdep
detector to those completion operations. Applied it.

Signed-off-by: default avatarByungchul Park <byungchul.park@lge.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: akpm@linux-foundation.org
Cc: boqun.feng@gmail.com
Cc: kernel-team@lge.com
Cc: kirill@shutemov.name
Cc: npiggin@gmail.com
Cc: walken@google.com
Cc: willy@infradead.org
Link: http://lkml.kernel.org/r/1502089981-21272-10-git-send-email-byungchul.park@lge.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 383a4bc8

include/linux/completion.h

+44 −1
Original line number Diff line number Diff line
@@ -9,6 +9,9 @@ 
 */



#include <linux/wait.h>

#ifdef CONFIG_LOCKDEP_COMPLETE

#include <linux/lockdep.h>

#endif



/*

 * struct completion - structure used to maintain state for a "completion"
@@ -25,10 +28,50 @@ 
struct completion {

	unsigned int done;

	wait_queue_head_t wait;

#ifdef CONFIG_LOCKDEP_COMPLETE

	struct lockdep_map_cross map;

#endif

};



#ifdef CONFIG_LOCKDEP_COMPLETE

static inline void complete_acquire(struct completion *x)

{

	lock_acquire_exclusive((struct lockdep_map *)&x->map, 0, 0, NULL, _RET_IP_);

}



static inline void complete_release(struct completion *x)

{

	lock_release((struct lockdep_map *)&x->map, 0, _RET_IP_);

}



static inline void complete_release_commit(struct completion *x)

{

	lock_commit_crosslock((struct lockdep_map *)&x->map);

}



#define init_completion(x)						\

do {									\

	static struct lock_class_key __key;				\

	lockdep_init_map_crosslock((struct lockdep_map *)&(x)->map,	\

			"(complete)" #x,				\

			&__key, 0);					\

	__init_completion(x);						\

} while (0)

#else

#define init_completion(x) __init_completion(x)

static inline void complete_acquire(struct completion *x) {}

static inline void complete_release(struct completion *x) {}

static inline void complete_release_commit(struct completion *x) {}

#endif



#ifdef CONFIG_LOCKDEP_COMPLETE

#define COMPLETION_INITIALIZER(work) \

	{ 0, __WAIT_QUEUE_HEAD_INITIALIZER((work).wait), \

	STATIC_CROSS_LOCKDEP_MAP_INIT("(complete)" #work, &(work)) }

#else

#define COMPLETION_INITIALIZER(work) \

	{ 0, __WAIT_QUEUE_HEAD_INITIALIZER((work).wait) }

#endif



#define COMPLETION_INITIALIZER_ONSTACK(work) \

	({ init_completion(&work); work; })
@@ -70,7 +113,7 @@ struct completion { 
 * This inline function will initialize a dynamically created completion

 * structure.

 */

static inline void init_completion(struct completion *x)

static inline void __init_completion(struct completion *x)

{

	x->done = 0;

	init_waitqueue_head(&x->wait);

kernel/sched/completion.c

+11 −0
Original line number Diff line number Diff line
@@ -32,6 +32,12 @@ void complete(struct completion *x) 
	unsigned long flags;



	spin_lock_irqsave(&x->wait.lock, flags);



	/*

	 * Perform commit of crossrelease here.

	 */

	complete_release_commit(x);



	if (x->done != UINT_MAX)

		x->done++;

	__wake_up_locked(&x->wait, TASK_NORMAL, 1);
@@ -92,9 +98,14 @@ __wait_for_common(struct completion *x, 
{

	might_sleep();



	complete_acquire(x);



	spin_lock_irq(&x->wait.lock);

	timeout = do_wait_for_common(x, action, timeout, state);

	spin_unlock_irq(&x->wait.lock);



	complete_release(x);



	return timeout;

}

lib/Kconfig.debug

+9 −0
Original line number Diff line number Diff line
@@ -1162,6 +1162,15 @@ config LOCKDEP_CROSSRELEASE 
	 such as page locks or completions can use the lock correctness

	 detector, lockdep.



config LOCKDEP_COMPLETE

	bool "Lock debugging: allow completions to use deadlock detector"

	depends on PROVE_LOCKING

	select LOCKDEP_CROSSRELEASE

	default n

	help

	 A deadlock caused by wait_for_completion() and complete() can be

	 detected by lockdep using crossrelease feature.



config DEBUG_LOCKDEP

	bool "Lock dependency engine debugging"

	depends on DEBUG_KERNEL && LOCKDEP