[PATCH 2/5] driver core: do not always lock parent in shutdown

[David Jeffery]

Don't lock a parent device unless it is needed in device_shutdown. This
is in preparation for making device shutdown asynchronous, when it will
be needed to allow children of a common parent to shut down
simultaneously.

Signed-off-by: Stuart Hayes <stuart.w.hayes@xxxxxxxxx>
Signed-off-by: David Jeffery <djeffery@xxxxxxxxxx>
Tested-by: Laurence Oberman <loberman@xxxxxxxxxx>
---
 drivers/base/core.c | 23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 10586298e18b..2e9094f5c5aa 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -4782,13 +4782,8 @@ int device_change_owner(struct device *dev, kuid_t kuid, kgid_t kgid)
 	return error;
 }
 
-static void shutdown_one_device(struct device *dev)
+static void __shutdown_one_device(struct device *dev)
 {
-	struct device *parent = dev->parent;
-
-	/* hold lock to avoid race with probe/release */
-	if (parent)
-		device_lock(parent);
 	device_lock(dev);
 
 	/* Don't allow any more runtime suspends */
@@ -4811,10 +4806,20 @@ static void shutdown_one_device(struct device *dev)
 	}
 
 	device_unlock(dev);
-	if (parent)
-		device_unlock(parent);
+}
 
-	put_device(parent);
+static void shutdown_one_device(struct device *dev)
+{
+	/* hold lock to avoid race with probe/release */
+	if (dev->parent && dev->bus && dev->bus->need_parent_lock) {
+		device_lock(dev->parent);
+		__shutdown_one_device(dev);
+		device_unlock(dev->parent);
+	} else {
+		__shutdown_one_device(dev);
+	}
+
+	put_device(dev->parent);
 	put_device(dev);
 }
 
-- 
2.53.0