Il 18/06/2013 17:14, mdroth ha scritto: > Could we possibly simplify this by introducing a recursive mutex that we > could use to protect the whole list loop and hold even during the cb?
If it is possible, we should avoid recursive locks. It makes impossible to establish a lock hierarchy. For example: > I assume we can't hold the lock during the cb currently since we might > try to reschedule, but if it's a recursive mutex would that simplify > things? If you have two callbacks in two different AioContexts, both of which do bdrv_drain_all(), you get an AB-BA deadlock Also, the barriers for qemu_bh_schedule are needed anyway. It's only those that order bh->next vs. ctx->first_bh that would go away. Paolo > I've been doing something similar with IOHandlers for the QContext > stuff, and that's the approach I took. This patch introduces the > recursive mutex: > > https://github.com/mdroth/qemu/commit/c7ee0844da62283c9466fcb10ddbfadd0b8bfc53
