On (Fri) 29 Apr 2011 [14:25:06], Alon Levy wrote:
> Instead of calling flush_queued_data when unthrottling, schedule
> a bh. That way we can return immediately to the caller, and the
> flush uses the same call path as a have_data for callbackee.
>
> No migration change is required because bh are called from vm_stop.
This one looks OK; I'll put it through some testing.
However, I'd like confirmation that accessing (and modifying) vq
elements is fine in bh context. Stefan / Michael?
> ---
> hw/virtio-serial-bus.c | 12 ++++++++++--
> hw/virtio-serial.h | 5 +++++
> 2 files changed, 15 insertions(+), 2 deletions(-)
>
> diff --git a/hw/virtio-serial-bus.c b/hw/virtio-serial-bus.c
> index f10d48f..ca0581b 100644
> --- a/hw/virtio-serial-bus.c
> +++ b/hw/virtio-serial-bus.c
> @@ -285,6 +285,13 @@ size_t virtio_serial_guest_ready(VirtIOSerialPort *port)
> return 0;
> }
>
> +static void flush_queued_data_bh(void *opaque)
> +{
> + VirtIOSerialPort *port = opaque;
> +
> + flush_queued_data(port);
> +}
> +
> void virtio_serial_throttle_port(VirtIOSerialPort *port, bool throttle)
> {
> if (!port) {
> @@ -295,8 +302,7 @@ void virtio_serial_throttle_port(VirtIOSerialPort *port,
> bool throttle)
> if (throttle) {
> return;
> }
> -
> - flush_queued_data(port);
> + qemu_bh_schedule(port->bh);
> }
>
> /* Guest wants to notify us of some event */
> @@ -726,6 +732,7 @@ static int virtser_port_qdev_init(DeviceState *qdev,
> DeviceInfo *base)
> bool plugging_port0;
>
> port->vser = bus->vser;
> + port->bh = qemu_bh_new(flush_queued_data_bh, port);
>
> /*
> * Is the first console port we're seeing? If so, put it up at
> @@ -792,6 +799,7 @@ static int virtser_port_qdev_exit(DeviceState *qdev)
> VirtIOSerialPort *port = DO_UPCAST(VirtIOSerialPort, dev, qdev);
> VirtIOSerial *vser = port->vser;
>
> + qemu_bh_delete(port->bh);
> remove_port(port->vser, port->id);
>
> QTAILQ_REMOVE(&vser->ports, port, next);
> diff --git a/hw/virtio-serial.h b/hw/virtio-serial.h
> index 5eb948e..0fa03d1 100644
> --- a/hw/virtio-serial.h
> +++ b/hw/virtio-serial.h
> @@ -119,6 +119,11 @@ struct VirtIOSerialPort {
> uint32_t iov_idx;
> uint64_t iov_offset;
>
> + /*
> + * When unthrottling we use a buttomhalf to call flush_queued_data.
> + */
> + QEMUBH *bh;
> +
> /* Identify if this is a port that binds with hvc in the guest */
> uint8_t is_console;
>
> --
> 1.7.5
>
Amit
