From: "Rafael J. Wysocki" rafael.j.wysocki@intel.com
[ Upstream commit d1579e61192e0e686faa4208500ef4c3b529b16c ]
Because refcount_dec_not_one() returns true if the target refcount becomes saturated, it is generally unsafe to use its return value as a loop termination condition, but that is what happens when a device link's supplier device is released during runtime PM suspend operations and on device link removal.
To address this, introduce pm_runtime_release_supplier() to be used in the above cases which will check the supplier device's runtime PM usage counter in addition to the refcount_dec_not_one() return value, so the loop can be terminated in case the rpm_active refcount value becomes invalid, and update the code in question to use it as appropriate.
This change is not expected to have any visible functional impact.
Reported-by: Peter Zijlstra peterz@infradead.org Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Acked-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Acked-by: Peter Zijlstra (Intel) peterz@infradead.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/base/core.c | 3 +-- drivers/base/power/runtime.c | 41 ++++++++++++++++++++++++++---------- include/linux/pm_runtime.h | 3 +++ 3 files changed, 34 insertions(+), 13 deletions(-)
diff --git a/drivers/base/core.c b/drivers/base/core.c index 63577de268565..8e73a34e10055 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -485,8 +485,7 @@ static void device_link_release_fn(struct work_struct *work) /* Ensure that all references to the link object have been dropped. */ device_link_synchronize_removal();
- while (refcount_dec_not_one(&link->rpm_active)) - pm_runtime_put(link->supplier); + pm_runtime_release_supplier(link, true);
put_device(link->consumer); put_device(link->supplier); diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c index ec94049442b99..44ae3909e64bb 100644 --- a/drivers/base/power/runtime.c +++ b/drivers/base/power/runtime.c @@ -305,19 +305,40 @@ static int rpm_get_suppliers(struct device *dev) return 0; }
+/** + * pm_runtime_release_supplier - Drop references to device link's supplier. + * @link: Target device link. + * @check_idle: Whether or not to check if the supplier device is idle. + * + * Drop all runtime PM references associated with @link to its supplier device + * and if @check_idle is set, check if that device is idle (and so it can be + * suspended). + */ +void pm_runtime_release_supplier(struct device_link *link, bool check_idle) +{ + struct device *supplier = link->supplier; + + /* + * The additional power.usage_count check is a safety net in case + * the rpm_active refcount becomes saturated, in which case + * refcount_dec_not_one() would return true forever, but it is not + * strictly necessary. + */ + while (refcount_dec_not_one(&link->rpm_active) && + atomic_read(&supplier->power.usage_count) > 0) + pm_runtime_put_noidle(supplier); + + if (check_idle) + pm_request_idle(supplier); +} + static void __rpm_put_suppliers(struct device *dev, bool try_to_suspend) { struct device_link *link;
list_for_each_entry_rcu(link, &dev->links.suppliers, c_node, - device_links_read_lock_held()) { - - while (refcount_dec_not_one(&link->rpm_active)) - pm_runtime_put_noidle(link->supplier); - - if (try_to_suspend) - pm_request_idle(link->supplier); - } + device_links_read_lock_held()) + pm_runtime_release_supplier(link, try_to_suspend); }
static void rpm_put_suppliers(struct device *dev) @@ -1770,9 +1791,7 @@ void pm_runtime_drop_link(struct device_link *link) return;
pm_runtime_drop_link_count(link->consumer); - - while (refcount_dec_not_one(&link->rpm_active)) - pm_runtime_put(link->supplier); + pm_runtime_release_supplier(link, true); }
static bool pm_runtime_need_not_resume(struct device *dev) diff --git a/include/linux/pm_runtime.h b/include/linux/pm_runtime.h index eddd66d426caf..016de5776b6db 100644 --- a/include/linux/pm_runtime.h +++ b/include/linux/pm_runtime.h @@ -58,6 +58,7 @@ 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_drop_link(struct device_link *link); +extern void pm_runtime_release_supplier(struct device_link *link, bool check_idle);
extern int devm_pm_runtime_enable(struct device *dev);
@@ -283,6 +284,8 @@ 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_drop_link(struct device_link *link) {} +static inline void pm_runtime_release_supplier(struct device_link *link, + bool check_idle) {}
#endif /* !CONFIG_PM */