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Subject[tip:sched/core] sched/wait: Introduce prepare_to_wait_event()
Commit-ID:  c2d816443ef305aba8eaf0bf368f4d3d87494f06
Gitweb: http://git.kernel.org/tip/c2d816443ef305aba8eaf0bf368f4d3d87494f06
Author: Oleg Nesterov <oleg@redhat.com>
AuthorDate: Mon, 7 Oct 2013 18:18:24 +0200
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 16 Oct 2013 14:22:18 +0200

sched/wait: Introduce prepare_to_wait_event()

Add the new helper, prepare_to_wait_event() which should only be used
by ___wait_event().

prepare_to_wait_event() returns -ERESTARTSYS if signal_pending_state()
is true, otherwise it does prepare_to_wait/exclusive. This allows to
uninline the signal-pending checks in wait_event*() macros.

Also, it can initialize wait->private/func. We do not care if they were
already initialized, the values are the same. This also shaves a couple
of insns from the inlined code.

This obviously makes prepare_*() path a little bit slower, but we are
likely going to sleep anyway, so I think it makes sense to shrink .text:

text data bss dec hex filename
===================================================
before: 5126092 2959248 10117120 18202460 115bf5c vmlinux
after: 5124618 2955152 10117120 18196890 115a99a vmlinux

on my build.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20131007161824.GA29757@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
include/linux/wait.h | 24 ++++++++++++++----------
kernel/wait.c | 24 ++++++++++++++++++++++++
2 files changed, 38 insertions(+), 10 deletions(-)

diff --git a/include/linux/wait.h b/include/linux/wait.h
index 04c0260..ec099b0 100644
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -187,27 +187,30 @@ wait_queue_head_t *bit_waitqueue(void *, int);
__cond || !__ret; \
})

-#define ___wait_signal_pending(state) \
- ((state == TASK_INTERRUPTIBLE && signal_pending(current)) || \
- (state == TASK_KILLABLE && fatal_signal_pending(current)))
+#define ___wait_is_interruptible(state) \
+ (!__builtin_constant_p(state) || \
+ state == TASK_INTERRUPTIBLE || state == TASK_KILLABLE) \

#define ___wait_event(wq, condition, state, exclusive, ret, cmd) \
({ \
__label__ __out; \
- DEFINE_WAIT(__wait); \
+ wait_queue_t __wait; \
long __ret = ret; \
\
+ INIT_LIST_HEAD(&__wait.task_list); \
+ if (exclusive) \
+ __wait.flags = WQ_FLAG_EXCLUSIVE; \
+ else \
+ __wait.flags = 0; \
+ \
for (;;) { \
- if (exclusive) \
- prepare_to_wait_exclusive(&wq, &__wait, state); \
- else \
- prepare_to_wait(&wq, &__wait, state); \
+ long __int = prepare_to_wait_event(&wq, &__wait, state);\
\
if (condition) \
break; \
\
- if (___wait_signal_pending(state)) { \
- __ret = -ERESTARTSYS; \
+ if (___wait_is_interruptible(state) && __int) { \
+ __ret = __int; \
if (exclusive) { \
abort_exclusive_wait(&wq, &__wait, \
state, NULL); \
@@ -791,6 +794,7 @@ extern long interruptible_sleep_on_timeout(wait_queue_head_t *q, signed long tim
*/
void prepare_to_wait(wait_queue_head_t *q, wait_queue_t *wait, int state);
void prepare_to_wait_exclusive(wait_queue_head_t *q, wait_queue_t *wait, int state);
+long prepare_to_wait_event(wait_queue_head_t *q, wait_queue_t *wait, int state);
void finish_wait(wait_queue_head_t *q, wait_queue_t *wait);
void abort_exclusive_wait(wait_queue_head_t *q, wait_queue_t *wait, unsigned int mode, void *key);
int autoremove_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key);
diff --git a/kernel/wait.c b/kernel/wait.c
index d550920..de21c63 100644
--- a/kernel/wait.c
+++ b/kernel/wait.c
@@ -92,6 +92,30 @@ prepare_to_wait_exclusive(wait_queue_head_t *q, wait_queue_t *wait, int state)
}
EXPORT_SYMBOL(prepare_to_wait_exclusive);

+long prepare_to_wait_event(wait_queue_head_t *q, wait_queue_t *wait, int state)
+{
+ unsigned long flags;
+
+ if (signal_pending_state(state, current))
+ return -ERESTARTSYS;
+
+ wait->private = current;
+ wait->func = autoremove_wake_function;
+
+ spin_lock_irqsave(&q->lock, flags);
+ if (list_empty(&wait->task_list)) {
+ if (wait->flags & WQ_FLAG_EXCLUSIVE)
+ __add_wait_queue_tail(q, wait);
+ else
+ __add_wait_queue(q, wait);
+ }
+ set_current_state(state);
+ spin_unlock_irqrestore(&q->lock, flags);
+
+ return 0;
+}
+EXPORT_SYMBOL(prepare_to_wait_event);
+
/**
* finish_wait - clean up after waiting in a queue
* @q: waitqueue waited on

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