4.14-stable review patch. If anyone has any objections, please let me know.
------------------
From: Jason Andryuk <jandryuk@xxxxxxxxx>
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@xxxxxxxxx>
Cc: Eduardo Otubo <otubo@xxxxxxxxxx>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/net/xen-netfront.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -2008,7 +2008,10 @@ static void netback_changed(struct xenbu
case XenbusStateInitialised:
case XenbusStateReconfiguring:
case XenbusStateReconfigured:
+ break;
+
case XenbusStateUnknown:
+ wake_up_all(&module_unload_q);
break;
case XenbusStateInitWait:
@@ -2139,7 +2142,9 @@ static int xennet_remove(struct xenbus_d
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,