From 4c06c4e6cf63d7f3d5dfe62593a073253d750a59 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 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 --- drivers/base/core.c | 21 ++++----------------- 1 file changed, 4 insertions(+), 17 deletions(-) (limited to 'drivers/base/core.c') diff --git a/drivers/base/core.c b/drivers/base/core.c index abfce4f613f8..787190238753 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -165,19 +165,6 @@ void device_pm_move_to_tail(struct device *dev) device_links_read_unlock(idx); } -static void device_link_rpm_prepare(struct device *consumer, - struct device *supplier) -{ - pm_runtime_new_link(consumer); - /* - * If the link is being added by the consumer driver at probe time, - * balance the decrementation of the supplier's runtime PM usage counter - * after consumer probe in driver_probe_device(). - */ - if (consumer->links.status == DL_DEV_PROBING) - pm_runtime_get_noresume(supplier); -} - /** * device_link_add - Create a link between two devices. * @consumer: Consumer end of the link. @@ -286,11 +273,11 @@ struct device_link *device_link_add(struct device *consumer, if (flags & DL_FLAG_PM_RUNTIME) { if (!(link->flags & DL_FLAG_PM_RUNTIME)) { - device_link_rpm_prepare(consumer, supplier); + pm_runtime_new_link(consumer); link->flags |= DL_FLAG_PM_RUNTIME; } if (flags & DL_FLAG_RPM_ACTIVE) - refcount_inc(&link->rpm_active); + pm_runtime_active_link(link, supplier); } if (flags & DL_FLAG_STATELESS) { @@ -323,9 +310,9 @@ struct device_link *device_link_add(struct device *consumer, if (flags & DL_FLAG_PM_RUNTIME) { if (flags & DL_FLAG_RPM_ACTIVE) - refcount_inc(&link->rpm_active); + pm_runtime_active_link(link, supplier); - device_link_rpm_prepare(consumer, supplier); + pm_runtime_new_link(consumer); } get_device(supplier); -- cgit v1.2.3