virtio: console: Fix poll blocking even though there is data to read
authorHans de Goede <hdegoede@redhat.com>
Thu, 16 Sep 2010 09:13:08 +0000 (14:43 +0530)
committerRusty Russell <rusty@rustcorp.com.au>
Tue, 21 Sep 2010 01:24:01 +0000 (10:54 +0930)
commit6df7aadcd9290807c464675098b5dd2dc9da5075
tree0afe6d6010d3eac58b1b5d748da91355fbfa422c
parent2422084a94fcd5038406261b331672a13c92c050
virtio: console: Fix poll blocking even though there is data to read

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 will_read_block(port) instead of the
port->inbuf != NULL check.

Signed-off-By: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: stable@kernel.org
drivers/char/virtio_console.c