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