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

David Jeffery
2026-04-20T15:26:47Z

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.

And only acquire a reference to the parent device if the parent is to be
locked.

Signed-off-by: Stuart Hayes <stuart.w.hayes@gmail.com>
Signed-off-by: David Jeffery <djeffery@redhat.com>
Tested-by: Laurence Oberman <loberman@redhat.com>
---
drivers/base/core.c | 30 ++++++++++++++++--------------
1 file changed, 16 insertions(+), 14 deletions(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 5353c6c22d49..a32fc7141957 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -4783,13 +4783,8 @@ 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 */
@@ -4812,10 +4807,23 @@ static void shutdown_one_device(struct device *dev)
}

device_unlock(dev);
- if (parent)
+}
+
+static void shutdown_one_device(struct device *dev)
+{
+ struct device *parent;
+
+ /* hold lock if needed to avoid race with probe/release */
+ if (dev->bus && dev->bus->need_parent_lock &&
+ (parent = get_device(dev->parent))) {
+ device_lock(parent);
+ __shutdown_one_device(dev);
device_unlock(parent);
+ put_device(parent);
+ } else {
+ __shutdown_one_device(dev);
+ }

- put_device(parent);
put_device(dev);
}

@@ -4841,12 +4849,6 @@ void device_shutdown(void)
dev = list_entry(devices_kset->list.prev, struct device,
kobj.entry);

- /*
- * hold reference count of device's parent to
- * prevent it from being freed because parent's
- * lock is to be held
- */
- get_device(dev->parent);
get_device(dev);
/*
* Make sure the device is off the kset list, in the
--
2.53.0