virtio_console: break out of buf poll on remove

A common pattern for device reset is currently:
vdev->config->reset(vdev);
.. cleanup ..

reset prevents new interrupts from arriving and waits for interrupt
handlers to finish.

However if - as is common - the handler queues a work request which is
flushed during the cleanup stage, we have code adding buffers / trying
to get buffers while device is reset. Not good.

This was reproduced by running
	modprobe virtio_console
	modprobe -r virtio_console
in a loop.

Fix this up by calling virtio_break_device + flush before reset.

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1786239
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 2359889..e3c4305 100644 (file)
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -1957,6 +1957,13 @@ static void virtcons_remove(struct virtio_device *vdev)
        list_del(&portdev->list);
        spin_unlock_irq(&pdrvdata_lock);
 
+       /* Device is going away, exit any polling for buffers */
+       virtio_break_device(vdev);
+       if (use_multiport(portdev))
+               flush_work(&portdev->control_work);
+       else
+               flush_work(&portdev->config_work);
+
        /* Disable interrupts for vqs */
        virtio_reset_device(vdev);
        /* Finish up work that's lined up */