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[PATCH] test-bdrv-drain: fix iothread_join() hang
From: |
Stefan Hajnoczi |
Subject: |
[PATCH] test-bdrv-drain: fix iothread_join() hang |
Date: |
Thu, 3 Oct 2019 11:01:03 +0100 |
tests/test-bdrv-drain can hang in tests/iothread.c:iothread_run():
while (!atomic_read(&iothread->stopping)) {
aio_poll(iothread->ctx, true);
}
The iothread_join() function works as follows:
void iothread_join(IOThread *iothread)
{
iothread->stopping = true;
aio_notify(iothread->ctx);
qemu_thread_join(&iothread->thread);
If iothread_run() checks iothread->stopping before the iothread_join()
thread sets stopping to true, then aio_notify() may be optimized away
and iothread_run() hangs forever in aio_poll().
The correct way to change iothread->stopping is from a BH that executes
within iothread_run(). This ensures that iothread->stopping is checked
after we set it to true.
This was already fixed for ./iothread.c (note this is a different source
file!) by commit 2362a28ea11c145e1a13ae79342d76dc118a72a6 ("iothread:
fix iothread_stop() race condition"), but not for tests/iothread.c.
Fixes: 0c330a734b51c177ab8488932ac3b0c4d63a718a
("aio: introduce aio_co_schedule and aio_co_wake")
Reported-by: Dr. David Alan Gilbert <address@hidden>
Cc: Paolo Bonzini <address@hidden>
Signed-off-by: Stefan Hajnoczi <address@hidden>
---
tests/iothread.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/tests/iothread.c b/tests/iothread.c
index 777d9eea46..13c9fdcd8d 100644
--- a/tests/iothread.c
+++ b/tests/iothread.c
@@ -55,10 +55,16 @@ static void *iothread_run(void *opaque)
return NULL;
}
-void iothread_join(IOThread *iothread)
+static void iothread_stop_bh(void *opaque)
{
+ IOThread *iothread = opaque;
+
iothread->stopping = true;
- aio_notify(iothread->ctx);
+}
+
+void iothread_join(IOThread *iothread)
+{
+ aio_bh_schedule_oneshot(iothread->ctx, iothread_stop_bh, iothread);
qemu_thread_join(&iothread->thread);
qemu_cond_destroy(&iothread->init_done_cond);
qemu_mutex_destroy(&iothread->init_done_lock);
--
2.21.0
- [PATCH] test-bdrv-drain: fix iothread_join() hang,
Stefan Hajnoczi <=