I didn't test is yet, and I did write the changelog.
But let me show the patch for review right now, before we all
forget the details... On top of Peter's "wait: Collapse __wait_event
macros -v4".
This patch moves the signal-pending checks and part of DEFINE_WAIT's
code into the new helper: prepare_to_wait_event().
Yes, sure, prepare_to_wait_event() becomes a little bit slower than
prepare_to_wait/prepare_to_wait_exclusive. But this is the slow path
anyway, we are likely going to sleep. IMO, it is better to shrink
.text, and on my build the difference is
- 5124686 2955056 10117120 18196862 115a97e vmlinux
+ 5123212 2955088 10117120 18195420 115a3dc vmlinux
The code with the patch is
#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;
\
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 (;;) {
\
long intr = prepare_to_wait_event(&wq, &__wait, state);
\
\
if (condition)
\
break;
\
\
if (___wait_is_interruptible(state) && intr) {
\
__ret = intr;
\
if (exclusive) {
\
abort_exclusive_wait(&wq, &__wait,
\
state, NULL);
\
goto __out;
\
}
\
break;
\
}
\
\
cmd;
\
}
\
finish_wait(&wq, &__wait);
\
__out: __ret;
\
})
Compiler should optimize out "long intr" if !interruptible/killable.
What do you think?
Oleg.
---
diff --git a/include/linux/wait.h b/include/linux/wait.h
index bd4bd7b..aa758d3 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 intr = prepare_to_wait_event(&wq, &__wait, state); \
\
if (condition) \
break; \
\
- if (___wait_signal_pending(state)) { \
- __ret = -ERESTARTSYS; \
+ if (___wait_is_interruptible(state) && intr) { \
+ __ret = intr; \
if (exclusive) { \
abort_exclusive_wait(&wq, &__wait, \
state, NULL); \
@@ -794,6 +797,7 @@ extern long
interruptible_sleep_on_timeout(wait_queue_head_t *q,
*/
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);
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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