On Thursday, December 10, 2015 11:43:50 AM Imre Deak wrote:

On Thu, 2015-12-10 at 01:58 +0100, Rafael J. Wysocki wrote:

quoted

On Wednesday, December 09, 2015 06:22:19 PM Joonas Lahtinen wrote:

quoted

Introduce pm_runtime_get_noidle to for situations where it is not
desireable to touch an idling device. One use scenario is periodic
hangchecks performed by the drm/i915 driver which can be omitted
on a device in a runtime idle state.

v2:
- Fix inconsistent return value when !CONFIG_PM.
- Update documentation for bool return value

Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reported-by: Chris Wilson <redacted>
Cc: Chris Wilson <redacted>
Cc: "Rafael J. Wysocki" <redacted>
Cc: linux-pm@vger.kernel.org

Well, I don't quite see how this can be used in a non-racy way
without doing an additional pm_runtime_resume() or something like
that in the same code path.

We don't want to resume, that would be the whole point. We'd like to
ensure that we hold a reference _and_ the device is already active. So
AFAICS we'd need to check runtime_status == RPM_ACTIVE in addition
after taking the reference.

Right, and that under the lock.

Thanks,
Rafael