Patchwork [1/1] virtio-serial-bus: use bh for unthrottling

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Submitter Amit Shah
Date May 12, 2011, 7:08 a.m.
Message ID <40674846d3c8f773976e0a43aebcd720038ee42d.1305184045.git.amit.shah@redhat.com>
Download mbox | patch
Permalink /patch/95265/
State New
Headers show

Comments

Amit Shah - May 12, 2011, 7:08 a.m.
From: Alon Levy <alevy@redhat.com>

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>
---
 hw/virtio-serial-bus.c |   12 ++++++++++--
 hw/virtio-serial.h     |    5 +++++
 2 files changed, 15 insertions(+), 2 deletions(-)

Patch

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;