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author | Michal Nazarewicz <m.nazarewicz@samsung.com> | 2010-05-05 12:53:11 +0200 |
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committer | Greg Kroah-Hartman <gregkh@suse.de> | 2010-05-20 13:21:42 -0700 |
commit | 22c43c81a51e05f61e90445ceb59d486c12fd921 (patch) | |
tree | 88582f01bf413bdc4d9d95a512116c9fe44afa33 /kernel | |
parent | 24337c133ff92ba8d7c42819db17f7f2b0de3129 (diff) | |
download | kernel_samsung_tuna-22c43c81a51e05f61e90445ceb59d486c12fd921.zip kernel_samsung_tuna-22c43c81a51e05f61e90445ceb59d486c12fd921.tar.gz kernel_samsung_tuna-22c43c81a51e05f61e90445ceb59d486c12fd921.tar.bz2 |
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: 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>
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/sched.c | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/kernel/sched.c b/kernel/sched.c index 3c2a54f..9584b66 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -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) { |