Am 06.12.2017 um 15:45 hat Stefan Hajnoczi geschrieben: > v2: > * Use StrOrNull for x-blockdev-set-iothread iothread argument [eblake] > > (This is for QEMU 2.12 because this bug is not -rc4 critical) > > Previously AioContext was held across QMP 'transaction' in an attempt to > achieve bdrv_drained_begin/end() semantics. Nowadays we have > bdrv_drained_begin/end() and the AioContext lock just protects state. > Therefore there is no reason to hold AioContext across > .prepare/.commit/.abort/.clean() anymore. > > Besides being cleanup-worthy, holding AioContext also exposes a bug: > BDRV_POLL_WHILE() doesn't support recursive AioContext locking and will hang > if > depth > 1. This is easy to trigger by submitting a transaction with 2 actions > that touch two drives assigned to an IOThread. The IOThread's AioContext will > be locked twice and BDRV_POLL_WHILE() will hang. > > BDRV_POLL_WHILE() is best fixed by eliminating the AioContext lock entirely in > favor of fine-grained locking. I discussed some fixes for BDRV_POLL_WHILE() > with Paolo but we came to the conclusion that it will just add complexity when > we really want to stop using AioContext locking.
Reviewed-by: Kevin Wolf <kw...@redhat.com> The only thing that I see that could use some improvements is the test case, which tests only a small part of the bugs that are fixed by this series. This doesn't invalidate any of the review, but I think without full test coverage, it's incomplete. Kevin
