Messages in this thread Patch in this message | | | From | Krzysztof Kozlowski <> | Subject | [PATCH] PM: runtime: document common mistake with pm_runtime_get_sync() | Date | Thu, 22 Apr 2021 18:46:06 +0200 |
| |
pm_runtime_get_sync(), contradictory to intuition, does not drop the runtime PM usage counter on errors which lead to several wrong usages in drivers (missing the put). pm_runtime_resume_and_get() was added as a better implementation so document the preference of using it, hoping it will stop bad patterns.
Suggested-by: Marek Szyprowski <m.szyprowski@samsung.com> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com> --- Documentation/power/runtime_pm.rst | 4 +++- include/linux/pm_runtime.h | 3 +++ 2 files changed, 6 insertions(+), 1 deletion(-)
diff --git a/Documentation/power/runtime_pm.rst b/Documentation/power/runtime_pm.rst index 18ae21bf7f92..478f08942811 100644 --- a/Documentation/power/runtime_pm.rst +++ b/Documentation/power/runtime_pm.rst @@ -378,7 +378,9 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h: `int pm_runtime_get_sync(struct device *dev);` - increment the device's usage counter, run pm_runtime_resume(dev) and - return its result + return its result; + be aware that it does not drop the device's usage counter on errors so + usage of pm_runtime_resume_and_get(dev) usually results in cleaner code `int pm_runtime_get_if_in_use(struct device *dev);` - return -EINVAL if 'power.disable_depth' is nonzero; otherwise, if the diff --git a/include/linux/pm_runtime.h b/include/linux/pm_runtime.h index 6c08a085367b..0dfd23d2cfc3 100644 --- a/include/linux/pm_runtime.h +++ b/include/linux/pm_runtime.h @@ -380,6 +380,9 @@ static inline int pm_runtime_get(struct device *dev) * The possible return values of this function are the same as for * pm_runtime_resume() and the runtime PM usage counter of @dev remains * incremented in all cases, even if it returns an error code. + * Lack of decrementing the runtime PM usage counter on errors is a common + * mistake, so consider using pm_runtime_resume_and_get() instead for a cleaner + * code. */ static inline int pm_runtime_get_sync(struct device *dev) { -- 2.25.1
| |