From 36003d4cf57ca431fb3f94d317bcca426a2394d6 Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Tue, 19 Feb 2019 17:53:26 +0100 Subject: driver core: Fix PM-runtime for links added during consumer probe Commit 4c06c4e6cf63 ("driver core: Fix possible supplier PM-usage counter imbalance") introduced a regression that causes suppliers to be suspended prematurely for device links added during consumer driver probe if the initial PM-runtime status of the consumer is "suspended" and the consumer is resumed after adding the link and before pm_runtime_put_suppliers() is called. In that case, pm_runtime_put_suppliers() will drop the rpm_active refcount for the link by one and (since rpm_active is equal to two after the preceding consumer resume) the supplier's PM-runtime usage counter will be decremented, which may cause the supplier to suspend even though the consumer's PM-runtime status is "active". For this reason, partially revert commit 4c06c4e6cf63 as the problem it tried to fix needs to be addressed somewhat differently, and change pm_runtime_get_suppliers() and pm_runtime_put_suppliers() so that the latter only drops rpm_active references acquired by the former. [This requires adding a new field to struct device_link, but I coulnd't find a cleaner way to address the issue that would work in all cases.] This causes pm_runtime_put_suppliers() to effectively ignore device links added during consumer probe, so device_link_add() doesn't need to worry about ensuring that suppliers will remain active after pm_runtime_put_suppliers() for links created with DL_FLAG_RPM_ACTIVE set and it only needs to bump up rpm_active by one for those links, so pm_runtime_active_link() is not necessary any more. Fixes: 4c06c4e6cf63 ("driver core: Fix possible supplier PM-usage counter imbalance") Reported-by: Jon Hunter Tested-by: Jon Hunter Tested-by: Ulf Hansson Reviewed-by: Ulf Hansson Signed-off-by: Rafael J. Wysocki Tested-by: Thierry Reding Signed-off-by: Greg Kroah-Hartman --- include/linux/device.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/device.h') diff --git a/include/linux/device.h b/include/linux/device.h index 292b720c4bc2..a7967a48cdc9 100644 --- a/include/linux/device.h +++ b/include/linux/device.h @@ -861,6 +861,7 @@ struct device_link { #ifdef CONFIG_SRCU struct rcu_head rcu_head; #endif + bool supplier_preactivated; /* Owned by consumer probe. */ }; /** -- cgit v1.2.2