|author||Stefan Hajnoczi <email@example.com>||2014-06-03 11:21:01 +0200|
|committer||Stefan Hajnoczi <firstname.lastname@example.org>||2014-06-04 09:56:06 +0200|
aio: fix qemu_bh_schedule() bh->ctx race condition
qemu_bh_schedule() is supposed to be thread-safe at least the first time it is called. Unfortunately this is not quite true: bh->scheduled = 1; aio_notify(bh->ctx); Since another thread may run the BH callback once it has been scheduled, there is a race condition if the callback frees the BH before aio_notify(bh->ctx) has a chance to run. Reported-by: Stefan Priebe <email@example.com> Signed-off-by: Stefan Hajnoczi <firstname.lastname@example.org> Reviewed-by: Paolo Bonzini <email@example.com> Tested-by: Stefan Priebe <firstname.lastname@example.org>
Diffstat (limited to 'async.c')
1 files changed, 10 insertions, 4 deletions
@@ -117,15 +117,21 @@ void qemu_bh_schedule_idle(QEMUBH *bh)
void qemu_bh_schedule(QEMUBH *bh)
+ AioContext *ctx;
+ ctx = bh->ctx;
bh->idle = 0;
- /* Make sure that idle & any writes needed by the callback are done
- * before the locations are read in the aio_bh_poll.
+ /* Make sure that:
+ * 1. idle & any writes needed by the callback are done before the
+ * locations are read in the aio_bh_poll.
+ * 2. ctx is loaded before scheduled is set and the callback has a chance
+ * to execute.
bh->scheduled = 1;