On 12/02/2015 06:21, Fam Zheng wrote: > Before processing a request, virtio-scsi dataplane will check if the > backend runs on the same context with it. If not, it has to be moved, > with bdrv_set_aio_context. > > However this function is unsafe to be called from IOThread outside BQL. > The reason is that it calls bdrv_drain_all(), to acquire and drain all > existing BDS. Therefore there is a deadlock problem. > > Fix it by offloading the bdrv_set_aio_context to main loop thread, > through a BH (#1). This main loop BH will set the context, then notify > the calling thread with another BH (#2). In BH (#2), we can continue the > virtio-scsi request processing. > > A queue is added to VirtIOSCSI for tracking the pending requests, so in > virtio_scsi_dataplane_stop, we have to drain them for migration. > > Signed-off-by: Fam Zheng <f...@redhat.com>
Could you just do set_aio_context for all devices when starting dataplane? For example with a new scsi_device_set_aio_context function (and a new method in SCSIDeviceClass). Maybe I'm missing the obvious. :) Paolo
