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From 8c657cb165e931b4eb6f3675495240437b0c1cb1 Mon Sep 17 00:00:00 2001
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From: Kevin Wolf <kwolf@redhat.com>
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Date: Fri, 14 Sep 2018 10:55:38 +0200
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Subject: [PATCH 47/49] test-bdrv-drain: Test nested poll in
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bdrv_drain_poll_top_level()
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RH-Author: Kevin Wolf <kwolf@redhat.com>
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Message-id: <20180914105540.18077-41-kwolf@redhat.com>
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Patchwork-id: 82189
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O-Subject: [RHV-7.6 qemu-kvm-rhev PATCH 40/42] test-bdrv-drain: Test nested poll in bdrv_drain_poll_top_level()
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Bugzilla: 1601212
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RH-Acked-by: John Snow <jsnow@redhat.com>
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RH-Acked-by: Max Reitz <mreitz@redhat.com>
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RH-Acked-by: Fam Zheng <famz@redhat.com>
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This is a regression test for a deadlock that could occur in callbacks
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called from the aio_poll() in bdrv_drain_poll_top_level(). The
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AioContext lock wasn't released and therefore would be taken a second
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time in the callback. This would cause a possible AIO_WAIT_WHILE() in
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the callback to hang.
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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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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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tests/test-bdrv-drain.c | 13 +++++++++++++
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1 file changed, 13 insertions(+)
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diff --git a/tests/test-bdrv-drain.c b/tests/test-bdrv-drain.c
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index 05f3b55..f4b57f7 100644
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--- a/tests/test-bdrv-drain.c
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+++ b/tests/test-bdrv-drain.c
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@@ -636,6 +636,17 @@ static void test_iothread_aio_cb(void *opaque, int ret)
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qemu_event_set(&done_event);
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}
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+static void test_iothread_main_thread_bh(void *opaque)
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+{
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+ struct test_iothread_data *data = opaque;
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+
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+ /* Test that the AioContext is not yet locked in a random BH that is
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+ * executed during drain, otherwise this would deadlock. */
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+ aio_context_acquire(bdrv_get_aio_context(data->bs));
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+ bdrv_flush(data->bs);
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+ aio_context_release(bdrv_get_aio_context(data->bs));
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+}
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+
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/*
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* Starts an AIO request on a BDS that runs in the AioContext of iothread 1.
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* The request involves a BH on iothread 2 before it can complete.
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@@ -705,6 +716,8 @@ static void test_iothread_common(enum drain_type drain_type, int drain_thread)
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aio_context_acquire(ctx_a);
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}
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+ aio_bh_schedule_oneshot(ctx_a, test_iothread_main_thread_bh, &data);
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+
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/* The request is running on the IOThread a. Draining its block device
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* will make sure that it has completed as far as the BDS is concerned,
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* but the drain in this thread can continue immediately after
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--
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1.8.3.1
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