Driver core: Protect device shutdown from hot unplug events.

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>

1 files changed, 22 insertions, 3 deletions

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 4c5be85016b6..356dd011b8f9 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -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();
 }