Commit 0957a2c1 authored by NeilBrown's avatar NeilBrown Committed by Greg Kroah-Hartman
Browse files

sched/wait: add wait_event_idle() functions. 



The new TASK_IDLE state (TASK_UNINTERRUPTIBLE | __TASK_NOLOAD)
is not much used.  One way to make it easier to use is to
add wait_event*() family functions that make use of it.
This patch adds:
  wait_event_idle()
  wait_event_idle_timeout()
  wait_event_idle_exclusive()
  wait_event_idle_exclusive_timeout()

This set was chosen because lustre needs them before
it can discard its own l_wait_event() macro.

Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarJames Simmons <jsimmons@infradead.org>
Signed-off-by: default avatarNeilBrown <neilb@suse.com>
Reviewed-by: default avatarPatrick Farrell <paf@cray.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 8016ab9e

include/linux/wait.h

+114 −0
Original line number Diff line number Diff line
@@ -599,6 +599,120 @@ do { \ 
	__ret;									\

})



/**

 * wait_event_idle - wait for a condition without contributing to system load

 * @wq_head: the waitqueue to wait on

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

 *

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

 * @condition evaluates to true.

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

 *

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

 * change the result of the wait condition.

 *

 */

#define wait_event_idle(wq_head, condition)					\

do {										\

	might_sleep();								\

	if (!(condition))							\

		___wait_event(wq_head, condition, TASK_IDLE, 0, 0, schedule());	\

} while (0)



/**

 * wait_event_idle_exclusive - wait for a condition with contributing to system load

 * @wq_head: the waitqueue to wait on

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

 *

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

 * @condition evaluates to true.

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

 *

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

 * set thus if other processes wait on the same list, when this

 * process is woken further processes are not considered.

 *

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

 * change the result of the wait condition.

 *

 */

#define wait_event_idle_exclusive(wq_head, condition)				\

do {										\

	might_sleep();								\

	if (!(condition))							\

		___wait_event(wq_head, condition, TASK_IDLE, 1, 0, schedule());	\

} while (0)



#define __wait_event_idle_timeout(wq_head, condition, timeout)			\

	___wait_event(wq_head, ___wait_cond_timeout(condition),			\

		      TASK_IDLE, 0, timeout,					\

		      __ret = schedule_timeout(__ret))



/**

 * wait_event_idle_timeout - sleep without load until a condition becomes true or a timeout elapses

 * @wq_head: the waitqueue to wait on

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

 * @timeout: timeout, in jiffies

 *

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

 * @condition evaluates to true. The @condition is checked each time

 * the waitqueue @wq_head is woken up.

 *

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

 * change the result of the wait condition.

 *

 * Returns:

 * 0 if the @condition evaluated to %false after the @timeout elapsed,

 * 1 if the @condition evaluated to %true after the @timeout elapsed,

 * or the remaining jiffies (at least 1) if the @condition evaluated

 * to %true before the @timeout elapsed.

 */

#define wait_event_idle_timeout(wq_head, condition, timeout)			\

({										\

	long __ret = timeout;							\

	might_sleep();								\

	if (!___wait_cond_timeout(condition))					\

		__ret = __wait_event_idle_timeout(wq_head, condition, timeout);	\

	__ret;									\

})



#define __wait_event_idle_exclusive_timeout(wq_head, condition, timeout)	\

	___wait_event(wq_head, ___wait_cond_timeout(condition),			\

		      TASK_IDLE, 1, timeout,					\

		      __ret = schedule_timeout(__ret))



/**

 * wait_event_idle_exclusive_timeout - sleep without load until a condition becomes true or a timeout elapses

 * @wq_head: the waitqueue to wait on

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

 * @timeout: timeout, in jiffies

 *

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

 * @condition evaluates to true. The @condition is checked each time

 * the waitqueue @wq_head is woken up.

 *

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

 * set thus if other processes wait on the same list, when this

 * process is woken further processes are not considered.

 *

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

 * change the result of the wait condition.

 *

 * Returns:

 * 0 if the @condition evaluated to %false after the @timeout elapsed,

 * 1 if the @condition evaluated to %true after the @timeout elapsed,

 * or the remaining jiffies (at least 1) if the @condition evaluated

 * to %true before the @timeout elapsed.

 */

#define wait_event_idle_exclusive_timeout(wq_head, condition, timeout)		\

({										\

	long __ret = timeout;							\

	might_sleep();								\

	if (!___wait_cond_timeout(condition))					\

		__ret = __wait_event_idle_exclusive_timeout(wq_head, condition, timeout);\

	__ret;									\

})



extern int do_wait_intr(wait_queue_head_t *, wait_queue_entry_t *);

extern int do_wait_intr_irq(wait_queue_head_t *, wait_queue_entry_t *);

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