On 10/09/2018 16:56, Fam Zheng wrote: > We have this unwanted call stack: > > > ... > > #13 0x00005586602b7793 in virtio_scsi_handle_cmd_vq > > #14 0x00005586602b8d66 in virtio_scsi_data_plane_handle_cmd > > #15 0x00005586602ddab7 in virtio_queue_notify_aio_vq > > #16 0x00005586602dfc9f in virtio_queue_host_notifier_aio_poll > > #17 0x00005586607885da in run_poll_handlers_once > > #18 0x000055866078880e in try_poll_mode > > #19 0x00005586607888eb in aio_poll > > #20 0x0000558660784561 in aio_wait_bh_oneshot > > #21 0x00005586602b9582 in virtio_scsi_dataplane_stop > > #22 0x00005586605a7110 in virtio_bus_stop_ioeventfd > > #23 0x00005586605a9426 in virtio_pci_stop_ioeventfd > > #24 0x00005586605ab808 in virtio_pci_common_write > > #25 0x0000558660242396 in memory_region_write_accessor > > #26 0x00005586602425ab in access_with_adjusted_size > > #27 0x0000558660245281 in memory_region_dispatch_write > > #28 0x00005586601e008e in flatview_write_continue > > #29 0x00005586601e01d8 in flatview_write > > #30 0x00005586601e04de in address_space_write > > #31 0x00005586601e052f in address_space_rw > > #32 0x00005586602607f2 in kvm_cpu_exec > > #33 0x0000558660227148 in qemu_kvm_cpu_thread_fn > > #34 0x000055866078bde7 in qemu_thread_start > > #35 0x00007f5784906594 in start_thread > > #36 0x00007f5784639e6f in clone > > Avoid it with the aio_disable_external/aio_enable_external pair, so that > no vq poll handlers can be called in aio_wait_bh_oneshot.
I don't understand. We are in the vCPU thread, so not in the AioContext's home thread. Why is aio_wait_bh_oneshot polling rather than going through the aio_wait_bh path? Thanks, Paolo