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| author | Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com> | 2021-05-26 12:22:51 -0400 |
|---|---|---|
| committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2021-05-31 14:17:13 +0200 |
| commit | c58e7ed28b4534ed073371843d03c433d6a9fe34 (patch) | |
| tree | 1eddbefcfcc586e30435101425feaa96887eb283 /Documentation/power | |
| parent | 8124c8a6b35386f73523d27eacb71b5364a68c4c (diff) | |
| download | lwn-c58e7ed28b4534ed073371843d03c433d6a9fe34.tar.gz lwn-c58e7ed28b4534ed073371843d03c433d6a9fe34.zip | |
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 <m.szyprowski@samsung.com>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
[ rjw: Documentation change edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'Documentation/power')
| -rw-r--r-- | Documentation/power/runtime_pm.rst | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/Documentation/power/runtime_pm.rst b/Documentation/power/runtime_pm.rst index 18ae21bf7f92..b48cac5f9048 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 |