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Subject[PATCH 2/2] wait: introduce prepare_to_wait_event()
Add the new helper, prepare_to_wait_event() which should only be used
by wait_event_common/etc.

prepare_to_wait_event() returns -ERESTARTSYS if signal_pending_state()
is true, otherwise it calls prepare_to_wait(). This allows to uninline
the signal-pending checks in wait_event_*.

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

Unlike the previous change, this patch "reliably" shrinks the size of
generated code for every wait_event*() call.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
include/linux/wait.h | 22 +++++++++++-----------
kernel/wait.c | 14 ++++++++++++++
2 files changed, 25 insertions(+), 11 deletions(-)

diff --git a/include/linux/wait.h b/include/linux/wait.h
index 392c54d..a2314dd 100644
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -176,28 +176,27 @@ wait_queue_head_t *bit_waitqueue(void *, int);
#define __wait_no_timeout(tout) \
(__builtin_constant_p(tout) && (tout) == MAX_SCHEDULE_TIMEOUT)

-/* uglified signal_pending_state() optimized for constant state */
-#define __wait_signal_pending(state) \
- ((state == TASK_INTERRUPTIBLE) ? signal_pending(current) : \
- (state == TASK_KILLABLE) ? fatal_signal_pending(current) : \
- 0)
+#define __wait_interruptible(state) \
+ (!__builtin_constant_p(state) || \
+ state == TASK_INTERRUPTIBLE || state == TASK_KILLABLE)

#define __wait_event_common(wq, condition, state, tout) \
({ \
- DEFINE_WAIT(__wait); \
- long __ret = 0, __tout = tout; \
+ long __ret, __tout = tout; \
+ wait_queue_t __wait; \
+ \
+ INIT_LIST_HEAD(&__wait.task_list); \
+ __wait.flags = 0; \
\
for (;;) { \
- prepare_to_wait(&wq, &__wait, state); \
+ __ret = prepare_to_wait_event(&wq, &__wait, state); \
if (condition) { \
__ret = __wait_no_timeout(tout) ?: __tout ?: 1; \
break; \
} \
\
- if (__wait_signal_pending(state)) { \
- __ret = -ERESTARTSYS; \
+ if (__wait_interruptible(state) && __ret) \
break; \
- } \
\
if (__wait_no_timeout(tout)) \
schedule(); \
@@ -781,6 +780,7 @@ extern long interruptible_sleep_on_timeout(wait_queue_head_t *q,
* Waitqueues which are removed from the waitqueue_head at wakeup time
*/
void prepare_to_wait(wait_queue_head_t *q, wait_queue_t *wait, int state);
+int prepare_to_wait_event(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);
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,
diff --git a/kernel/wait.c b/kernel/wait.c
index 6698e0c..57cc6e7 100644
--- a/kernel/wait.c
+++ b/kernel/wait.c
@@ -78,6 +78,20 @@ prepare_to_wait(wait_queue_head_t *q, wait_queue_t *wait, int state)
}
EXPORT_SYMBOL(prepare_to_wait);

+int
+prepare_to_wait_event(wait_queue_head_t *q, wait_queue_t *wait, int state)
+{
+ if (signal_pending_state(state, current))
+ return -ERESTARTSYS;
+
+ wait->private = current;
+ wait->func = autoremove_wake_function;
+ prepare_to_wait(q, wait, state);
+
+ return 0;
+}
+EXPORT_SYMBOL(prepare_to_wait_event);
+
void
prepare_to_wait_exclusive(wait_queue_head_t *q, wait_queue_t *wait, int state)
{
--
1.5.5.1



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