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xen-netfront: Fix hang on device removal

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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: 5b5971df3b ("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>
This commit is contained in:
Jason Andryuk 2018-02-28 07:23:23 -05:00 committed by Juergen Gross
parent 910f8befdf
commit c2d2e6738a
1 changed files with 6 additions and 1 deletions
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7
drivers/net/xen-netfront.c
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@ -2005,7 +2005,10 @@ 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:
@ -2136,7 +2139,9 @@ 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,