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-rw-r--r--util/aio-posix.c47
1 files changed, 25 insertions, 22 deletions
diff --git a/util/aio-posix.c b/util/aio-posix.c
index 1b2a3af65b..f7f13ebfc2 100644
--- a/util/aio-posix.c
+++ b/util/aio-posix.c
@@ -464,9 +464,6 @@ static bool remove_idle_poll_handlers(AioContext *ctx, int64_t now)
*
* Polls for a given time.
*
- * Note that ctx->notify_me must be non-zero so this function can detect
- * aio_notify().
- *
* Note that the caller must have incremented ctx->list_lock.
*
* Returns: true if progress was made, false otherwise
@@ -476,7 +473,6 @@ static bool run_poll_handlers(AioContext *ctx, int64_t max_ns, int64_t *timeout)
bool progress;
int64_t start_time, elapsed_time;
- assert(ctx->notify_me);
assert(qemu_lockcnt_count(&ctx->list_lock) > 0);
trace_run_poll_handlers_begin(ctx, max_ns, *timeout);
@@ -520,8 +516,6 @@ static bool run_poll_handlers(AioContext *ctx, int64_t max_ns, int64_t *timeout)
* @timeout: timeout for blocking wait, computed by the caller and updated if
* polling succeeds.
*
- * ctx->notify_me must be non-zero so this function can detect aio_notify().
- *
* Note that the caller must have incremented ctx->list_lock.
*
* Returns: true if progress was made, false otherwise
@@ -556,6 +550,7 @@ bool aio_poll(AioContext *ctx, bool blocking)
AioHandlerList ready_list = QLIST_HEAD_INITIALIZER(ready_list);
int ret = 0;
bool progress;
+ bool use_notify_me;
int64_t timeout;
int64_t start = 0;
@@ -566,33 +561,39 @@ bool aio_poll(AioContext *ctx, bool blocking)
*/
assert(in_aio_context_home_thread(ctx));
- /* aio_notify can avoid the expensive event_notifier_set if
+ qemu_lockcnt_inc(&ctx->list_lock);
+
+ if (ctx->poll_max_ns) {
+ start = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
+ }
+
+ timeout = blocking ? aio_compute_timeout(ctx) : 0;
+ progress = try_poll_mode(ctx, &timeout);
+ assert(!(timeout && progress));
+
+ /*
+ * aio_notify can avoid the expensive event_notifier_set if
* everything (file descriptors, bottom halves, timers) will
* be re-evaluated before the next blocking poll(). This is
* already true when aio_poll is called with blocking == false;
* if blocking == true, it is only true after poll() returns,
* so disable the optimization now.
*/
- if (blocking) {
+ use_notify_me = timeout != 0;
+ if (use_notify_me) {
atomic_set(&ctx->notify_me, atomic_read(&ctx->notify_me) + 2);
/*
- * Write ctx->notify_me before computing the timeout
- * (reading bottom half flags, etc.). Pairs with
+ * Write ctx->notify_me before reading ctx->notified. Pairs with
* smp_mb in aio_notify().
*/
smp_mb();
- }
-
- qemu_lockcnt_inc(&ctx->list_lock);
- if (ctx->poll_max_ns) {
- start = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
+ /* Don't block if aio_notify() was called */
+ if (atomic_read(&ctx->notified)) {
+ timeout = 0;
+ }
}
- timeout = blocking ? aio_compute_timeout(ctx) : 0;
- progress = try_poll_mode(ctx, &timeout);
- assert(!(timeout && progress));
-
/* If polling is allowed, non-blocking aio_poll does not need the
* system call---a single round of run_poll_handlers_once suffices.
*/
@@ -600,12 +601,14 @@ bool aio_poll(AioContext *ctx, bool blocking)
ret = ctx->fdmon_ops->wait(ctx, &ready_list, timeout);
}
- if (blocking) {
+ if (use_notify_me) {
/* Finish the poll before clearing the flag. */
- atomic_store_release(&ctx->notify_me, atomic_read(&ctx->notify_me) - 2);
- aio_notify_accept(ctx);
+ atomic_store_release(&ctx->notify_me,
+ atomic_read(&ctx->notify_me) - 2);
}
+ aio_notify_accept(ctx);
+
/* Adjust polling time */
if (ctx->poll_max_ns) {
int64_t block_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME) - start;