[Xen-devel] [PATCH 10/11] xen kexec: reset device state to Initializing during reboot

[Olaf Hering <olaf@xxxxxxxxx>]

During kexec all devices will be shutdown, the backend drivers enter the
Closed state. But in this state the kexec kernel can not connect to the
backend because it expects the devices in InitWait state.
After triggering the Closing event, trigger also the Initializing event
and wait until the backend has changed its state. Without this waiting
the kexec kernel may find a device where a state change from Closed to
InitWait is still in progress.

v2:
 unregister the watch on the /local/domain/0/backend/<dev>/<domid>/0/state
 node to avoid memory corruption in the kexec kernel

v3:
 use kexec_is_loaded() function

Signed-off-by: Olaf Hering <olaf@xxxxxxxxx>

---
 drivers/xen/xenbus/xenbus_probe.c |   25 +++++++++++++++++++++++--
 1 file changed, 23 insertions(+), 2 deletions(-)

Index: linux-3.0/drivers/xen/xenbus/xenbus_probe.c
===================================================================
--- linux-3.0.orig/drivers/xen/xenbus/xenbus_probe.c
+++ linux-3.0/drivers/xen/xenbus/xenbus_probe.c
@@ -46,6 +46,7 @@
 #include <linux/mutex.h>
 #include <linux/io.h>
 #include <linux/slab.h>
+#include <linux/kexec.h>
 
 #include <asm/page.h>
 #include <asm/pgtable.h>
@@ -192,8 +193,19 @@ void xenbus_otherend_changed(struct xenb
         * work that can fail e.g., when the rootfs is gone.
         */
        if (system_state > SYSTEM_RUNNING) {
-               if (ignore_on_shutdown && (state == XenbusStateClosing))
-                       xenbus_frontend_closed(dev);
+               if (ignore_on_shutdown) {
+                       switch (state) {
+                       case XenbusStateClosing:
+                               xenbus_frontend_closed(dev);
+                               break;
+                       case XenbusStateInitialising:
+                       case XenbusStateInitWait:
+                               complete(&dev->down);
+                               break;
+                       default:
+                               break;
+                       }
+               }
                return;
        }
 
@@ -284,6 +296,15 @@ void xenbus_dev_shutdown(struct device *
        if (!timeout)
                printk(KERN_INFO "%s: %s timeout closing device\n",
                       __func__, dev->nodename);
+
+       if (system_state > SYSTEM_RUNNING && kexec_is_loaded()) {
+               xenbus_switch_state(dev, XenbusStateInitialising);
+               timeout = wait_for_completion_timeout(&dev->down, timeout);
+               if (!timeout)
+                       printk(KERN_INFO "%s: %s timeout initializing device\n",
+                              __func__, dev->nodename);
+               free_otherend_watch(dev);
+       }
  out:
        put_device(&dev->dev);
 }


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