From 3d6b7c14f88f11fd835c1947c149545d393f3fad Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Tue, 12 Feb 2019 13:08:10 +0100 Subject: driver core: Fix possible supplier PM-usage counter imbalance [ Upstream commit 4c06c4e6cf63d7f3d5dfe62593a073253d750a59 ] If a stateless device link to a certain supplier with DL_FLAG_PM_RUNTIME set in the flags is added and then removed by the consumer driver's probe callback, the supplier's PM-runtime usage counter will be nonzero after that which effectively causes the supplier to remain "always on" going forward. Namely, device_link_add() called to add the link invokes device_link_rpm_prepare() which notices that the consumer driver is probing, so it increments the supplier's PM-runtime usage counter with the assumption that the link will stay around until pm_runtime_put_suppliers() is called by driver_probe_device(), but if the link goes away before that point, the supplier's PM-runtime usage counter will remain nonzero. To prevent that from happening, first rework pm_runtime_get_suppliers() and pm_runtime_put_suppliers() to use the rpm_active refounts of device links and make the latter only drop rpm_active and the supplier's PM-runtime usage counter for each link by one, unless rpm_active is one already for it. Next, modify device_link_add() to bump up the new link's rpm_active refcount and the suppliers PM-runtime usage counter by two, to prevent pm_runtime_put_suppliers(), if it is called subsequently, from suspending the supplier prematurely (in case its PM-runtime usage counter goes down to 0 in there). Due to the way rpm_put_suppliers() works, this change does not affect runtime suspend of the consumer ends of new device links (or, generally, device links for which DL_FLAG_PM_RUNTIME has just been set). Fixes: e2f3cd831a28 ("driver core: Fix handling of runtime PM flags in device_link_add()") Reported-by: Ulf Hansson Signed-off-by: Rafael J. Wysocki Reviewed-by: Ulf Hansson Tested-by: Ulf Hansson Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- include/linux/pm_runtime.h | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'include/linux/pm_runtime.h') diff --git a/include/linux/pm_runtime.h b/include/linux/pm_runtime.h index f0fc4700b6ff..bace7df51af4 100644 --- a/include/linux/pm_runtime.h +++ b/include/linux/pm_runtime.h @@ -59,6 +59,8 @@ extern void pm_runtime_clean_up_links(struct device *dev); extern void pm_runtime_get_suppliers(struct device *dev); extern void pm_runtime_put_suppliers(struct device *dev); extern void pm_runtime_new_link(struct device *dev); +extern void pm_runtime_active_link(struct device_link *link, + struct device *supplier); extern void pm_runtime_drop_link(struct device *dev); static inline void pm_suspend_ignore_children(struct device *dev, bool enable) @@ -176,6 +178,8 @@ static inline void pm_runtime_clean_up_links(struct device *dev) {} static inline void pm_runtime_get_suppliers(struct device *dev) {} static inline void pm_runtime_put_suppliers(struct device *dev) {} static inline void pm_runtime_new_link(struct device *dev) {} +static inline void pm_runtime_active_link(struct device_link *link, + struct device *supplier) {} static inline void pm_runtime_drop_link(struct device *dev) {} #endif /* !CONFIG_PM */ -- cgit v1.2.3