diff options
Diffstat (limited to 'linux-2.6.35.4-virtio_console-fix-poll.patch')
| -rw-r--r-- | linux-2.6.35.4-virtio_console-fix-poll.patch | 29 |
1 files changed, 29 insertions, 0 deletions
diff --git a/linux-2.6.35.4-virtio_console-fix-poll.patch b/linux-2.6.35.4-virtio_console-fix-poll.patch new file mode 100644 index 000000000..ff46eb41e --- /dev/null +++ b/linux-2.6.35.4-virtio_console-fix-poll.patch @@ -0,0 +1,29 @@ +Subject: virtio_console: Fix poll blocking even though there is data to read (version 2) +From: Hans de Goede <hdegoede@redhat.com> + +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 ready to be read, this +patch fixes this by using port_has_data(port) instead of the +port->inbuf != NULL check. + +Signed-off-By: Hans de Goede <hdegoede@redhat.com> +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 (port_has_data(port)) + ret |= POLLIN | POLLRDNORM; + if (!will_write_block(port)) + ret |= POLLOUT; |