From cf3129323f900ef5ddbccbe86e4fa801e88c566e Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Mon, 22 Jul 2019 17:46:23 +0200 Subject: block-backend: Queue requests while drained This fixes devices like IDE that can still start new requests from I/O handlers in the CPU thread while the block backend is drained. The basic assumption is that in a drain section, no new requests should be allowed through a BlockBackend (blk_drained_begin/end don't exist, we get drain sections only on the node level). However, there are two special cases where requests should not be queued: 1. Block jobs: We already make sure that block jobs are paused in a drain section, so they won't start new requests. However, if the drain_begin is called on the job's BlockBackend first, it can happen that we deadlock because the job stays busy until it reaches a pause point - which it can't if its requests aren't processed any more. The proper solution here would be to make all requests through the job's filter node instead of using a BlockBackend. For now, just disabling request queuing on the job BlockBackend is simpler. 2. In test cases where making requests through bdrv_* would be cumbersome because we'd need a BdrvChild. As we already got the functionality to disable request queuing from 1., use it in tests, too, for convenience. Signed-off-by: Kevin Wolf Reviewed-by: Max Reitz --- tests/test-bdrv-drain.c | 1 + 1 file changed, 1 insertion(+) (limited to 'tests/test-bdrv-drain.c') diff --git a/tests/test-bdrv-drain.c b/tests/test-bdrv-drain.c index 9dffd86c47..468bbcc9a1 100644 --- a/tests/test-bdrv-drain.c +++ b/tests/test-bdrv-drain.c @@ -686,6 +686,7 @@ static void test_iothread_common(enum drain_type drain_type, int drain_thread) &error_abort); s = bs->opaque; blk_insert_bs(blk, bs, &error_abort); + blk_set_disable_request_queuing(blk, true); blk_set_aio_context(blk, ctx_a, &error_abort); aio_context_acquire(ctx_a); -- cgit v1.2.3