From 30bdfc5373eab96cb1f3d62ab90b07becd885272 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Wed, 10 Oct 2018 20:22:07 +0100 Subject: [PATCH 41/49] block: Remove aio_poll() in bdrv_drain_poll variants RH-Author: Kevin Wolf Message-id: <20181010202213.7372-29-kwolf@redhat.com> Patchwork-id: 82619 O-Subject: [RHEL-8 qemu-kvm PATCH 38/44] block: Remove aio_poll() in bdrv_drain_poll variants Bugzilla: 1637976 RH-Acked-by: Max Reitz RH-Acked-by: John Snow RH-Acked-by: Thomas Huth bdrv_drain_poll_top_level() was buggy because it didn't release the AioContext lock of the node to be drained before calling aio_poll(). This way, callbacks called by aio_poll() would possibly take the lock a second time and run into a deadlock with a nested AIO_WAIT_WHILE() call. However, it turns out that the aio_poll() call isn't actually needed any more. It was introduced in commit 91af091f923, which is effectively reverted by this patch. The cases it was supposed to fix are now covered by bdrv_drain_poll(), which waits for block jobs to reach a quiescent state. Signed-off-by: Kevin Wolf Reviewed-by: Fam Zheng Reviewed-by: Max Reitz (cherry picked from commit 4cf077b59fc73eec29f8b7d082919dbb278bdc86) Signed-off-by: Kevin Wolf Signed-off-by: Danilo C. L. de Paula --- block/io.c | 8 -------- 1 file changed, 8 deletions(-) diff --git a/block/io.c b/block/io.c index 19db35e..3313958 100644 --- a/block/io.c +++ b/block/io.c @@ -266,10 +266,6 @@ bool bdrv_drain_poll(BlockDriverState *bs, bool recursive, static bool bdrv_drain_poll_top_level(BlockDriverState *bs, bool recursive, BdrvChild *ignore_parent) { - /* Execute pending BHs first and check everything else only after the BHs - * have executed. */ - while (aio_poll(bs->aio_context, false)); - return bdrv_drain_poll(bs, recursive, ignore_parent, false); } @@ -509,10 +505,6 @@ static bool bdrv_drain_all_poll(void) BlockDriverState *bs = NULL; bool result = false; - /* Execute pending BHs first (may modify the graph) and check everything - * else only after the BHs have executed. */ - while (aio_poll(qemu_get_aio_context(), false)); - /* bdrv_drain_poll() can't make changes to the graph and we are holding the * main AioContext lock, so iterating bdrv_next_all_states() is safe. */ while ((bs = bdrv_next_all_states(bs))) { -- 1.8.3.1