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Subject[PATCH 01/19] 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: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: NeilBrown <neilb@suse.com>
---
include/linux/wait.h | 114 ++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 114 insertions(+)

diff --git a/include/linux/wait.h b/include/linux/wait.h
index 158715445ffb..ec7e7c65cee6 100644
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -597,6 +597,120 @@ 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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