Commit 22c43c81 authored by Michal Nazarewicz's avatar Michal Nazarewicz Committed by Greg Kroah-Hartman
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wait_event_interruptible_locked() interface 



New wait_event_interruptible{,_exclusive}_locked{,_irq} macros added.
They work just like versions without _locked* suffix but require the
wait queue's lock to be held.  Also __wake_up_locked() is now exported
as to pair it with the above macros.

The use case of this new facility is when one uses wait queue's lock
to  protect a data structure.  This may be advantageous if the
structure needs to be protected by a spinlock anyway.  In particular,
with additional spinlock the following code has to be used to wait
for a condition:

spin_lock(&data.lock);
...
for (ret = 0; !ret && !(condition); ) {
	spin_unlock(&data.lock);
	ret = wait_event_interruptible(data.wqh, (condition));
	spin_lock(&data.lock);
}
...
spin_unlock(&data.lock);

This looks bizarre plus wait_event_interruptible() locks the wait
queue's lock anyway so there is a unlock+lock sequence where it could
be avoided.

To avoid those problems and benefit from wait queue's lock, a code
similar to the following should be used:

/* Waiting */
spin_lock(&data.wqh.lock);
...
ret = wait_event_interruptible_locked(data.wqh, (condition));
...
spin_unlock(&data.wqh.lock);

/* Waiting exclusively */
spin_lock(&data.whq.lock);
...
ret = wait_event_interruptible_exclusive_locked(data.whq, (condition));
...
spin_unlock(&data.whq.lock);

/* Waking up */
spin_lock(&data.wqh.lock);
...
wake_up_locked(&data.wqh);
...
spin_unlock(&data.wqh.lock);

When spin_lock_irq() is used matching versions of macros need to be
used (*_locked_irq()).

Signed-off-by: default avatarMichal Nazarewicz <m.nazarewicz@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Takashi Iwai <tiwai@suse.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Andreas Herrmann <andreas.herrmann3@amd.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Mike Galbraith <efault@gmx.de>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 24337c13

include/linux/wait.h

+149 −0
Original line number Diff line number Diff line
@@ -362,6 +362,155 @@ do { \ 
	__ret;								\

})





#define __wait_event_interruptible_locked(wq, condition, exclusive, irq) \

({									\

	int __ret = 0;							\

	DEFINE_WAIT(__wait);						\

	if (exclusive)							\

		__wait.flags |= WQ_FLAG_EXCLUSIVE;			\

	do {								\

		if (likely(list_empty(&__wait.task_list)))		\

			__add_wait_queue_tail(&(wq), &__wait);		\

		set_current_state(TASK_INTERRUPTIBLE);			\

		if (signal_pending(current)) {				\

			__ret = -ERESTARTSYS;				\

			break;						\

		}							\

		if (irq)						\

			spin_unlock_irq(&(wq).lock);			\

		else							\

			spin_unlock(&(wq).lock);			\

		schedule();						\

		if (irq)						\

			spin_lock_irq(&(wq).lock);			\

		else							\

			spin_lock(&(wq).lock);				\

	} while (!(condition));						\

	__remove_wait_queue(&(wq), &__wait);				\

	__set_current_state(TASK_RUNNING);				\

	__ret;								\

})





/**

 * wait_event_interruptible_locked - sleep until a condition gets true

 * @wq: the waitqueue to wait on

 * @condition: a C expression for the event to wait for

 *

 * The process is put to sleep (TASK_INTERRUPTIBLE) until the

 * @condition evaluates to true or a signal is received.

 * The @condition is checked each time the waitqueue @wq is woken up.

 *

 * It must be called with wq.lock being held.  This spinlock is

 * unlocked while sleeping but @condition testing is done while lock

 * is held and when this macro exits the lock is held.

 *

 * The lock is locked/unlocked using spin_lock()/spin_unlock()

 * functions which must match the way they are locked/unlocked outside

 * of this macro.

 *

 * wake_up_locked() has to be called after changing any variable that could

 * change the result of the wait condition.

 *

 * The function will return -ERESTARTSYS if it was interrupted by a

 * signal and 0 if @condition evaluated to true.

 */

#define wait_event_interruptible_locked(wq, condition)			\

	((condition)							\

	 ? 0 : __wait_event_interruptible_locked(wq, condition, 0, 0))



/**

 * wait_event_interruptible_locked_irq - sleep until a condition gets true

 * @wq: the waitqueue to wait on

 * @condition: a C expression for the event to wait for

 *

 * The process is put to sleep (TASK_INTERRUPTIBLE) until the

 * @condition evaluates to true or a signal is received.

 * The @condition is checked each time the waitqueue @wq is woken up.

 *

 * It must be called with wq.lock being held.  This spinlock is

 * unlocked while sleeping but @condition testing is done while lock

 * is held and when this macro exits the lock is held.

 *

 * The lock is locked/unlocked using spin_lock_irq()/spin_unlock_irq()

 * functions which must match the way they are locked/unlocked outside

 * of this macro.

 *

 * wake_up_locked() has to be called after changing any variable that could

 * change the result of the wait condition.

 *

 * The function will return -ERESTARTSYS if it was interrupted by a

 * signal and 0 if @condition evaluated to true.

 */

#define wait_event_interruptible_locked_irq(wq, condition)		\

	((condition)							\

	 ? 0 : __wait_event_interruptible_locked(wq, condition, 0, 1))



/**

 * wait_event_interruptible_exclusive_locked - sleep exclusively until a condition gets true

 * @wq: the waitqueue to wait on

 * @condition: a C expression for the event to wait for

 *

 * The process is put to sleep (TASK_INTERRUPTIBLE) until the

 * @condition evaluates to true or a signal is received.

 * The @condition is checked each time the waitqueue @wq is woken up.

 *

 * It must be called with wq.lock being held.  This spinlock is

 * unlocked while sleeping but @condition testing is done while lock

 * is held and when this macro exits the lock is held.

 *

 * The lock is locked/unlocked using spin_lock()/spin_unlock()

 * functions which must match the way they are locked/unlocked outside

 * of this macro.

 *

 * The process is put on the wait queue with an WQ_FLAG_EXCLUSIVE flag

 * set thus when other process waits process on the list if this

 * process is awaken further processes are not considered.

 *

 * wake_up_locked() has to be called after changing any variable that could

 * change the result of the wait condition.

 *

 * The function will return -ERESTARTSYS if it was interrupted by a

 * signal and 0 if @condition evaluated to true.

 */

#define wait_event_interruptible_exclusive_locked(wq, condition)	\

	((condition)							\

	 ? 0 : __wait_event_interruptible_locked(wq, condition, 1, 0))



/**

 * wait_event_interruptible_exclusive_locked_irq - sleep until a condition gets true

 * @wq: the waitqueue to wait on

 * @condition: a C expression for the event to wait for

 *

 * The process is put to sleep (TASK_INTERRUPTIBLE) until the

 * @condition evaluates to true or a signal is received.

 * The @condition is checked each time the waitqueue @wq is woken up.

 *

 * It must be called with wq.lock being held.  This spinlock is

 * unlocked while sleeping but @condition testing is done while lock

 * is held and when this macro exits the lock is held.

 *

 * The lock is locked/unlocked using spin_lock_irq()/spin_unlock_irq()

 * functions which must match the way they are locked/unlocked outside

 * of this macro.

 *

 * The process is put on the wait queue with an WQ_FLAG_EXCLUSIVE flag

 * set thus when other process waits process on the list if this

 * process is awaken further processes are not considered.

 *

 * wake_up_locked() has to be called after changing any variable that could

 * change the result of the wait condition.

 *

 * The function will return -ERESTARTSYS if it was interrupted by a

 * signal and 0 if @condition evaluated to true.

 */

#define wait_event_interruptible_exclusive_locked_irq(wq, condition)	\

	((condition)							\

	 ? 0 : __wait_event_interruptible_locked(wq, condition, 1, 1))







#define __wait_event_killable(wq, condition, ret)			\

do {									\

	DEFINE_WAIT(__wait);						\

kernel/sched.c

+1 −0
Original line number Diff line number Diff line
@@ -3950,6 +3950,7 @@ void __wake_up_locked(wait_queue_head_t *q, unsigned int mode) 
{

	__wake_up_common(q, mode, 1, 0, NULL);

}

EXPORT_SYMBOL_GPL(__wake_up_locked);



void __wake_up_locked_key(wait_queue_head_t *q, unsigned int mode, void *key)

{

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