Commit 6df7aadc authored by Hans de Goede's avatar Hans de Goede Committed by Rusty Russell

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: default avatarHans de Goede <hdegoede@redhat.com>
Signed-off-by: default avatarAmit Shah <amit.shah@redhat.com>
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
Cc: stable@kernel.org
parent 2422084a
...@@ -642,7 +642,7 @@ static unsigned int port_fops_poll(struct file *filp, poll_table *wait) ...@@ -642,7 +642,7 @@ static unsigned int port_fops_poll(struct file *filp, poll_table *wait)
poll_wait(filp, &port->waitqueue, wait); poll_wait(filp, &port->waitqueue, wait);
ret = 0; ret = 0;
if (port->inbuf) if (!will_read_block(port))
ret |= POLLIN | POLLRDNORM; ret |= POLLIN | POLLRDNORM;
if (!will_write_block(port)) if (!will_write_block(port))
ret |= POLLOUT; ret |= POLLOUT;
......
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