[Xen-changelog] [xen-unstable] [XENBUS] Don't perform normal state-machine transitions and

[Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User kfraser@xxxxxxxxxxxxxxxxxxxxx
# Node ID dc017943eea2182390e675c08d9daac2b2ebdf1d
# Parent  d90be316e5f5852da5626d1b1a72d890a5c18000
[XENBUS] Don't perform normal state-machine transitions and
notifications during shutdown. When rootfs goes away this can
cause the system to hang, as we notify userspace etc.
Instead we forcibly reset the state machine back to state Closed
if we are a frontend driver, to get the backend to release
resources. Necessary if we are going to kexec.
Signed-off-by: Keir Fraser <keir@xxxxxxxxxxxxx>
---
 linux-2.6-xen-sparse/drivers/xen/blkfront/blkfront.c   |    2 +-
 linux-2.6-xen-sparse/drivers/xen/xenbus/xenbus_probe.c |   14 ++++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff -r d90be316e5f5 -r dc017943eea2 
linux-2.6-xen-sparse/drivers/xen/blkfront/blkfront.c
--- a/linux-2.6-xen-sparse/drivers/xen/blkfront/blkfront.c      Thu Sep 28 
13:44:00 2006 -0700
+++ b/linux-2.6-xen-sparse/drivers/xen/blkfront/blkfront.c      Fri Sep 29 
09:14:28 2006 +0100
@@ -273,7 +273,7 @@ static void backend_changed(struct xenbu
                        xenbus_dev_fatal(dev, -ENODEV, "bdget failed");
 
                down(&bd->bd_sem);
-               if (info->users > 0 && system_state == SYSTEM_RUNNING)
+               if (info->users > 0)
                        xenbus_dev_error(dev, -EBUSY,
                                         "Device in use; refusing to close");
                else
diff -r d90be316e5f5 -r dc017943eea2 
linux-2.6-xen-sparse/drivers/xen/xenbus/xenbus_probe.c
--- a/linux-2.6-xen-sparse/drivers/xen/xenbus/xenbus_probe.c    Thu Sep 28 
13:44:00 2006 -0700
+++ b/linux-2.6-xen-sparse/drivers/xen/xenbus/xenbus_probe.c    Fri Sep 29 
09:14:28 2006 +0100
@@ -322,6 +322,20 @@ static void otherend_changed(struct xenb
        DPRINTK("state is %d (%s), %s, %s", state, xenbus_strstate(state),
                dev->otherend_watch.node, vec[XS_WATCH_PATH]);
 
+       /*
+        * Ignore xenbus transitions during shutdown. This prevents us doing
+        * work that can fail e.g., when the rootfs is gone.
+        */
+       if (system_state > SYSTEM_RUNNING) {
+               struct xen_bus_type *bus = bus;
+               bus = container_of(dev->dev.bus, struct xen_bus_type, bus);
+               /* If we're frontend, drive the state machine to Closed. */
+               /* This should cause the backend to release our resources. */
+               if ((bus == &xenbus_frontend) && (state == XenbusStateClosing))
+                       xenbus_frontend_closed(dev);
+               return;
+       }
+
        if (drv->otherend_changed)
                drv->otherend_changed(dev, state);
 }

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