From: "Rafael J. Wysocki" rafael.j.wysocki@intel.com
[ Upstream commit 36003d4cf57ca431fb3f94d317bcca426a2394d6 ]
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 jonathanh@nvidia.com Tested-by: Jon Hunter jonathanh@nvidia.com Tested-by: Ulf Hansson ulf.hansson@linaro.org Reviewed-by: Ulf Hansson ulf.hansson@linaro.org Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Tested-by: Thierry Reding treding@nvidia.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/base/core.c | 4 ++-- drivers/base/power/runtime.c | 29 ++++++----------------------- include/linux/device.h | 1 + include/linux/pm_runtime.h | 4 ---- 4 files changed, 9 insertions(+), 29 deletions(-)
diff --git a/drivers/base/core.c b/drivers/base/core.c index ab08211ba5d2..742bc60e9cca 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -253,7 +253,7 @@ struct device_link *device_link_add(struct device *consumer, link->flags |= DL_FLAG_PM_RUNTIME; } if (flags & DL_FLAG_RPM_ACTIVE) - pm_runtime_active_link(link, supplier); + refcount_inc(&link->rpm_active); }
kref_get(&link->kref); @@ -268,7 +268,7 @@ struct device_link *device_link_add(struct device *consumer,
if (flags & DL_FLAG_PM_RUNTIME) { if (flags & DL_FLAG_RPM_ACTIVE) - pm_runtime_active_link(link, supplier); + refcount_inc(&link->rpm_active);
pm_runtime_new_link(consumer); } diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c index 0527890b4c19..303ce7d54a30 100644 --- a/drivers/base/power/runtime.c +++ b/drivers/base/power/runtime.c @@ -1571,6 +1571,7 @@ void pm_runtime_get_suppliers(struct device *dev)
list_for_each_entry_rcu(link, &dev->links.suppliers, c_node) if (link->flags & DL_FLAG_PM_RUNTIME) { + link->supplier_preactivated = true; refcount_inc(&link->rpm_active); pm_runtime_get_sync(link->supplier); } @@ -1590,9 +1591,11 @@ void pm_runtime_put_suppliers(struct device *dev) idx = device_links_read_lock();
list_for_each_entry_rcu(link, &dev->links.suppliers, c_node) - if (link->flags & DL_FLAG_PM_RUNTIME && - refcount_dec_not_one(&link->rpm_active)) - pm_runtime_put(link->supplier); + if (link->supplier_preactivated) { + link->supplier_preactivated = false; + if (refcount_dec_not_one(&link->rpm_active)) + pm_runtime_put(link->supplier); + }
device_links_read_unlock(idx); } @@ -1604,26 +1607,6 @@ void pm_runtime_new_link(struct device *dev) spin_unlock_irq(&dev->power.lock); }
-/** - * pm_runtime_active_link - Set up new device link as active for PM-runtime. - * @link: Device link to be set up as active. - * @supplier: Supplier end of the link. - * - * Add 2 to the rpm_active refcount of @link and increment the PM-runtime - * usage counter of @supplier once more in case the link is being added while - * the consumer driver is probing and pm_runtime_put_suppliers() will be called - * subsequently. - * - * Note that this doesn't prevent rpm_put_suppliers() from decreasing the link's - * rpm_active refcount down to one, so runtime suspend of the consumer end of - * @link is not affected. - */ -void pm_runtime_active_link(struct device_link *link, struct device *supplier) -{ - refcount_add(2, &link->rpm_active); - pm_runtime_get_noresume(supplier); -} - void pm_runtime_drop_link(struct device *dev) { spin_lock_irq(&dev->power.lock); diff --git a/include/linux/device.h b/include/linux/device.h index b8fd2a1f859d..e9d1c768f972 100644 --- a/include/linux/device.h +++ b/include/linux/device.h @@ -854,6 +854,7 @@ struct device_link { #ifdef CONFIG_SRCU struct rcu_head rcu_head; #endif + bool supplier_preactivated; /* Owned by consumer probe. */ };
/** diff --git a/include/linux/pm_runtime.h b/include/linux/pm_runtime.h index bace7df51af4..f0fc4700b6ff 100644 --- a/include/linux/pm_runtime.h +++ b/include/linux/pm_runtime.h @@ -59,8 +59,6 @@ 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) @@ -178,8 +176,6 @@ 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 */