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authorKevin Wolf <kwolf@redhat.com>2023-05-17 17:28:32 +0200
committerKevin Wolf <kwolf@redhat.com>2023-05-19 19:16:53 +0200
commit80fc5d260002432628710f8b0c7cfc7d9b97bb9d (patch)
treec0a397e67f8711a120340993ab5273473c0c4c2d /nbd
parent844a12a63e12b1235a8fc17f9b278929dc6eb00e (diff)
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graph-lock: Disable locking for now
In QEMU 8.0, we've been seeing deadlocks in bdrv_graph_wrlock(). They come from callers that hold an AioContext lock, which is not allowed during polling. In theory, we could temporarily release the lock, but callers are inconsistent about whether they hold a lock, and if they do, some are also confused about which one they hold. While all of this is fixable, it's not trivial, and the best course of action for 8.0.1 is probably just disabling the graph locking code temporarily. We don't currently rely on graph locking yet. It is supposed to replace the AioContext lock eventually to enable multiqueue support, but as long as we still have the AioContext lock, it is sufficient without the graph lock. Once the AioContext lock goes away, the deadlock doesn't exist any more either and this commit can be reverted. (Of course, it can also be reverted while the AioContext lock still exists if the callers have been fixed.) Cc: qemu-stable@nongnu.org Signed-off-by: Kevin Wolf <kwolf@redhat.com> Message-Id: <20230517152834.277483-2-kwolf@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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