Commit 456374e6 authored Feb 28, 2018 by Jason Andryuk Committed by Greg Kroah-Hartman Apr 24, 2018

xen-netfront: Fix hang on device removal



commit c2d2e6738a209f0f9dffa2dc8e7292fc45360d61 upstream.

A toolstack may delete the vif frontend and backend xenstore entries
while xen-netfront is in the removal code path.  In that case, the
checks for xenbus_read_driver_state would return XenbusStateUnknown, and
xennet_remove would hang indefinitely.  This hang prevents system
shutdown.

xennet_remove must be able to handle XenbusStateUnknown, and
netback_changed must also wake up the wake_queue for that state as well.

Fixes: 5b5971df3bc2 ("xen-netfront: remove warning when unloading module")

Signed-off-by: Jason Andryuk <jandryuk@gmail.com>
Cc: Eduardo Otubo <otubo@redhat.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent e0e3def0

drivers/net/xen-netfront.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -2067,7 +2067,10 @@ static void netback_changed(struct xenbus_device *dev,
		case XenbusStateInitialised:
		case XenbusStateReconfiguring:
		case XenbusStateReconfigured:
		break;

		case XenbusStateUnknown:
		wake_up_all(&module_unload_q);
		break;

		case XenbusStateInitWait:
		@@ -2314,7 +2317,9 @@ static int xennet_remove(struct xenbus_device *dev)
		xenbus_switch_state(dev, XenbusStateClosing);
		wait_event(module_unload_q,
		xenbus_read_driver_state(dev->otherend) ==
		XenbusStateClosing);
		XenbusStateClosing \|\|
		xenbus_read_driver_state(dev->otherend) ==
		XenbusStateUnknown);

		xenbus_switch_state(dev, XenbusStateClosed);
		wait_event(module_unload_q,