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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 /include/linux/wait.h | |
parent | 24337c133ff92ba8d7c42819db17f7f2b0de3129 (diff) | |
download | linux-stable-22c43c81a51e05f61e90445ceb59d486c12fd921.tar.gz linux-stable-22c43c81a51e05f61e90445ceb59d486c12fd921.tar.bz2 linux-stable-22c43c81a51e05f61e90445ceb59d486c12fd921.zip |
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 'include/linux/wait.h')
-rw-r--r-- | include/linux/wait.h | 149 |
1 files changed, 149 insertions, 0 deletions
diff --git a/include/linux/wait.h b/include/linux/wait.h index a48e16b77d5e..fc3c040e5e3a 100644 --- a/include/linux/wait.h +++ b/include/linux/wait.h @@ -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); \ |