On (Wed) Sep 15 2010 [15:04:53], Hans de Goede wrote: > Hi All, > > I found this while working on a Linux agent for spice, the symptom I was > seeing was select blocking on the spice vdagent virtio serial port even > though there were messages queued up there. > > I found this while working on a Linux agent for spice, the symptom I was > seeing was select blocking on the spice vdagent virtio serial port even > though there were messages queued up there. > > virtio_console's port_fops_poll checks port->inbuf != NULL to determine if > read won't block. However if an application reads enough bytes from inbuf > through port_fops_read, to empty the current port->inbuf, port->inbuf > will be NULL even though there may be buffers left in the virtqueue. > > This causes poll() to block even though there is data to be read, this patch > fixes this by using the alredy defined will_read_block utility function > instead of the port->inbuf != NULL check. > > Signed-off-By: Hans de Goede <hdegoede@xxxxxxxxxx> > > Regards, > > Hans > diff -up linux-2.6.35.x86_64/drivers/char/virtio_console.c~ linux-2.6.35.x86_64/drivers/char/virtio_console.c > --- linux-2.6.35.x86_64/drivers/char/virtio_console.c~ 2010-08-02 00:11:14.000000000 +0200 > +++ linux-2.6.35.x86_64/drivers/char/virtio_console.c 2010-09-15 13:39:29.043505000 +0200 > @@ -642,7 +642,7 @@ static unsigned int port_fops_poll(struc > poll_wait(filp, &port->waitqueue, wait); > > ret = 0; > - if (port->inbuf) > + if (!will_read_block(port)) Looks correct, but this should be if (port_has_data(port)) instead. will_read_block() also tests if the host is connected, which is not what we want for POLLIN to be set. Amit -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
