On Wed, 05/27 11:38, Paolo Bonzini wrote: > > > On 27/05/2015 09:19, Fam Zheng wrote: > > This series looks at the other side of the broken "qmp transaction" problem > > with dataplane [1] - the event loop. > > > > Before, an ioeventfd of a non-dataplane device is registered via > > qemu_set_fd_handler, which is only polled directly by main_loop_wait(), not > > in > > aio_poll(); an ioeventfd of a dataplane device (virtio-blk/virtio-scsi) is > > registered specially via aio_set_event_notifier, which is a wrapper of > > aio_set_fd_handler, thus it WILL be polled by all aio_poll(). > > > > As explained in [1], and in patch 3, this is wrong. The handlers mustn't > > run. > > > > [1] Fixes it by unregistering them temporarily around such nested poll, > > while > > this series fixes it by skipping those file descriptors in all nested > > aio_poll(), just like how iohandler behaves in the main loop. > > > > On the one hand, it is simpler than [1]; on the other hand, this approach is > > also interesting because once we remove qemu_set_fd_handler2 [2], > > iohandler.c > > can be removed by converting all qemu_set_fd_handler to the new > > aio_set_io_event_notifier introduced in this series. > > I don't think this can work. > > Whenever the main context is doing synchronous work for dataplane, it is > in the outermost aio_poll. >
You're right. :( The main context uses iohandler and aio_dispatch, neither calls aio_set_dispatching(). However, if we have [2], they can be changed to aio_poll(), then would this idea work? Fam
