xen/hvc: handle backend CLOSED without CLOSING

Backend drivers shouldn't transistion to CLOSED unless the frontend is
CLOSED.  If a backend does transition to CLOSED too soon then the
frontend may not see the CLOSING state and will not properly shutdown.

So, treat an unexpected backend CLOSED state the same as CLOSING.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

diff --git a/drivers/tty/hvc/hvc_xen.c b/drivers/tty/hvc/hvc_xen.c
index 2944ff88fdc0b2ea9705850e080a755aca440a8d..f4abfe238f98cb6bb6a4c53607bd4adf2a447ebc 100644 (file)
--- a/drivers/tty/hvc/hvc_xen.c
+++ b/drivers/tty/hvc/hvc_xen.c
@@ -478,7 +478,6 @@ static void xencons_backend_changed(struct xenbus_device *dev,
        case XenbusStateInitialising:
        case XenbusStateInitialised:
        case XenbusStateUnknown:
-       case XenbusStateClosed:
                break;
 
        case XenbusStateInitWait:
@@ -488,6 +487,10 @@ static void xencons_backend_changed(struct xenbus_device *dev,
                xenbus_switch_state(dev, XenbusStateConnected);
                break;
 
+       case XenbusStateClosed:
+               if (dev->state == XenbusStateClosed)
+                       break;
+               /* Missed the backend's CLOSING state -- fallthrough */
        case XenbusStateClosing:
                xenbus_frontend_closed(dev);
                break;