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[Qemu-devel] [RFC PATCH] async: Fix aio_notify_accept
From: |
Fam Zheng |
Subject: |
[Qemu-devel] [RFC PATCH] async: Fix aio_notify_accept |
Date: |
Fri, 3 Aug 2018 23:49:55 +0800 |
>From main loop, bdrv_set_aio_context() can call IOThread's aio_poll().
That breaks aio_notify() because the ctx->notifier event can get cleared
too early by this which causes IOThread hanging.
See https://bugzilla.redhat.com/show_bug.cgi?id=1562750 for details.
Signed-off-by: Fam Zheng <address@hidden>
---
util/async.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/util/async.c b/util/async.c
index 05979f8014..c6e8aebc3a 100644
--- a/util/async.c
+++ b/util/async.c
@@ -355,7 +355,11 @@ void aio_notify(AioContext *ctx)
void aio_notify_accept(AioContext *ctx)
{
- if (atomic_xchg(&ctx->notified, false)) {
+ /* If ctx->notify_me >= 2, another aio_poll() is waiting which may need the
+ * ctx->notifier event to wake up, so don't already clear it just because
"we" are
+ * done iterating. */
+ if (atomic_read(&ctx->notify_me) < 2
+ && atomic_xchg(&ctx->notified, false)) {
event_notifier_test_and_clear(&ctx->notifier);
}
}
--
2.17.1
- [Qemu-devel] [RFC PATCH] async: Fix aio_notify_accept,
Fam Zheng <=