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test-bdrv-drain: Take graph lock more selectively

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If we take a reader lock, we can't call any functions that take a writer
lock internally without causing deadlocks once the reader lock is
actually enforced in the main thread, too. Take the reader lock only
where it is actually needed.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20230510203601.418015-6-kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Kevin Wolf 2023-05-10 22:35:58 +02:00
parent 3db0c8b25c
commit 87f130bdaa
1 changed files with 2 additions and 2 deletions
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4
tests/unit/test-bdrv-drain.c
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@ -1004,8 +1004,6 @@ static void coroutine_fn test_co_delete_by_drain(void *opaque)
void *buffer = g_malloc(65536); void *buffer = g_malloc(65536);
QEMUIOVector qiov = QEMU_IOVEC_INIT_BUF(qiov, buffer, 65536); QEMUIOVector qiov = QEMU_IOVEC_INIT_BUF(qiov, buffer, 65536);
GRAPH_RDLOCK_GUARD();
/* Pretend some internal write operation from parent to child. /* Pretend some internal write operation from parent to child.
* Important: We have to read from the child, not from the parent! * Important: We have to read from the child, not from the parent!
* Draining works by first propagating it all up the tree to the * Draining works by first propagating it all up the tree to the
@ -1014,7 +1012,9 @@ static void coroutine_fn test_co_delete_by_drain(void *opaque)
* everything will be drained before we go back down the tree, but * everything will be drained before we go back down the tree, but
* we do not want that. We want to be in the middle of draining * we do not want that. We want to be in the middle of draining
* when this following requests returns. */ * when this following requests returns. */
bdrv_graph_co_rdlock();
bdrv_co_preadv(tts->wait_child, 0, 65536, &qiov, 0); bdrv_co_preadv(tts->wait_child, 0, 65536, &qiov, 0);
bdrv_graph_co_rdunlock();
g_assert_cmpint(bs->refcnt, ==, 1); g_assert_cmpint(bs->refcnt, ==, 1);