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wait_event_interruptible_locked() interface

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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: Michal 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: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Michal Nazarewicz 2010-05-05 12:53:11 +02:00 committed by Greg Kroah-Hartman
parent 24337c133f
commit 22c43c81a5
2 changed files with 150 additions and 0 deletions
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149
include/linux/wait.h
View file

@ -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); \

1
kernel/sched.c
View file

@ -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)
{