From: Krzysztof Kozlowski Date: Wed, 26 May 2021 16:22:51 +0000 (-0400) Subject: PM: runtime: document common mistake with pm_runtime_get_sync() X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=c58e7ed28b4534ed073371843d03c433d6a9fe34;p=linux.git PM: runtime: document common mistake with pm_runtime_get_sync() 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 Signed-off-by: Krzysztof Kozlowski [ rjw: Documentation change edits ] Signed-off-by: Rafael J. Wysocki --- diff --git a/Documentation/power/runtime_pm.rst b/Documentation/power/runtime_pm.rst index 18ae21bf7f925..b48cac5f90489 100644 --- a/Documentation/power/runtime_pm.rst +++ b/Documentation/power/runtime_pm.rst @@ -378,7 +378,11 @@ 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; + note that it does not drop the device's usage counter on errors, so + consider using pm_runtime_resume_and_get() instead of it, especially + if its return value is checked by the caller, as this is likely to + result 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 6c08a085367bf..aab8b35e9f8ac 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. + * Consider using pm_runtime_resume_and_get() instead of it, especially + * if its return value is checked by the caller, as this is likely to result + * in cleaner code. */ static inline int pm_runtime_get_sync(struct device *dev) {