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>
diff --git a/drivers/base/core.c b/drivers/base/core.c
index 4c5be85..356dd01 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -1734,10 +1734,25 @@
*/
void device_shutdown(void)
{
- struct device *dev, *devn;
+ struct device *dev;
- list_for_each_entry_safe_reverse(dev, devn, &devices_kset->list,
- kobj.entry) {
+ 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);
+
if (dev->bus && dev->bus->shutdown) {
dev_dbg(dev, "shutdown\n");
dev->bus->shutdown(dev);
@@ -1745,6 +1760,10 @@
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();
}