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virtio-serial-bus: use bh for unthrottling
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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.

Signed-off-by: Alon Levy <alevy@redhat.com>
Signed-off-by: Amit Shah <amit.shah@redhat.com>
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Alon Levy authored and Amit Shah committed May 27, 2011
1 parent aa29141 commit 199646d
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Showing 2 changed files with 15 additions and 2 deletions.
12 changes: 10 additions & 2 deletions hw/virtio-serial-bus.c
Original file line number Diff line number Diff line change
Expand Up @@ -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) {
Expand All @@ -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 */
Expand Down Expand Up @@ -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
Expand Down Expand Up @@ -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);
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5 changes: 5 additions & 0 deletions hw/virtio-serial.h
Original file line number Diff line number Diff line change
Expand Up @@ -119,6 +119,11 @@ struct VirtIOSerialPort {
uint32_t iov_idx;
uint64_t iov_offset;

/*
* When unthrottling we use a bottom-half to call flush_queued_data.
*/
QEMUBH *bh;

/* Identify if this is a port that binds with hvc in the guest */
uint8_t is_console;

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