Driver core: Protect device shutdown from hot unplug events.
Hugh Daschbach [Mon, 22 Mar 2010 17:36:37 +0000 (10:36 -0700)]
While device_shutdown() walks through devices_kset to shutdown all
devices, device unplug events may race to shutdown individual devices.
Specifically, sd_shutdown(), on behalf of fc_starget_delete(), has
been observed deleting devices during device_shutdown()'s list
traversal.  So we factor out list_for_each_entry_safe_reverse(...) in
favor of while (!list_empty(...)).

Signed-off-by: Hugh Daschbach <hdasch@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/base/core.c

index 4c5be85..356dd01 100644 (file)
@@ -1734,10 +1734,25 @@ EXPORT_SYMBOL_GPL(device_move);
  */
 void device_shutdown(void)
 {
-       struct device *dev, *devn;
+       struct device *dev;
+
+       spin_lock(&devices_kset->list_lock);
+       /*
+        * Walk the devices list backward, shutting down each in turn.
+        * Beware that device unplug events may also start pulling
+        * devices offline, even as the system is shutting down.
+        */
+       while (!list_empty(&devices_kset->list)) {
+               dev = list_entry(devices_kset->list.prev, struct device,
+                               kobj.entry);
+               get_device(dev);
+               /*
+                * Make sure the device is off the kset list, in the
+                * event that dev->*->shutdown() doesn't remove it.
+                */
+               list_del_init(&dev->kobj.entry);
+               spin_unlock(&devices_kset->list_lock);
 
-       list_for_each_entry_safe_reverse(dev, devn, &devices_kset->list,
-                               kobj.entry) {
                if (dev->bus && dev->bus->shutdown) {
                        dev_dbg(dev, "shutdown\n");
                        dev->bus->shutdown(dev);
@@ -1745,6 +1760,10 @@ void device_shutdown(void)
                        dev_dbg(dev, "shutdown\n");
                        dev->driver->shutdown(dev);
                }
+               put_device(dev);
+
+               spin_lock(&devices_kset->list_lock);
        }
+       spin_unlock(&devices_kset->list_lock);
        async_synchronize_full();
 }