Il 25/06/2013 08:32, liu ping fan ha scritto: > On Tue, Jun 25, 2013 at 2:24 PM, Paolo Bonzini <pbonz...@redhat.com> wrote: >> Il 25/06/2013 19:38, Liu Ping Fan ha scritto: >>> This series relies on refcnt of object used by bh callback to run against >>> unplug. >>> >>> Open issue: >>> Another choice may be rcu, but I think some issues are hard to resolve. >>> Using rcu, we have two choice: >>> when holding object refcnt, call qemu_bh_delete(); then after grace >>> period, we can release. >>> Or making qemu_bh_delete() sync in the path of DeviceState's finalization. >> >> What do you mean exactly? qemu_bh_delete() is async, but it operates on >> dynamically-allocated memory. >> > Before DeviceState is freed, we should make sure the bh is delete, and > not related bh is in fly.
The bh need not be deleted. It just needs to be not-scheduled (easy, qemu_bh_delete does that) and not running. The latter part could be the hard one in a multi-threaded context, but I think it's up to the device to ensure it. It doesn't _have_ to be hard. For example, joining the data-plane thread would do that as well. Paolo >> Paolo >> >>> but currently, the callers of qemu_bh_delete() can not satisfy any of the >>> two condition. >>
