I think your idea of having the extra kerneldoc as a seperate patch to make this easier to backport should work fine :). Thanks for the good work!
Reviewed-by: Lyude Paul <ly...@redhat.com> On Wed, 2018-02-14 at 08:41 +0100, Lukas Wunner wrote: > Introduce a helper to determine if the current task is an output poll > worker. > > This allows us to fix a long-standing deadlock in several DRM drivers > wherein the ->runtime_suspend callback waits for the output poll worker > to finish and the worker in turn calls a ->detect callback which waits > for runtime suspend to finish. The ->detect callback is invoked from > multiple call sites and waiting for runtime suspend to finish is the > correct thing to do except if it's executing in the context of the > worker. > > v2: Expand kerneldoc to specifically mention deadlock between > output poll worker and autosuspend worker as use case. (Lyude) > > Cc: Dave Airlie <airl...@redhat.com> > Cc: Ben Skeggs <bske...@redhat.com> > Cc: Alex Deucher <alexander.deuc...@amd.com> > Reviewed-by: Lyude Paul <ly...@redhat.com> > Signed-off-by: Lukas Wunner <lu...@wunner.de> > --- > drivers/gpu/drm/drm_probe_helper.c | 20 ++++++++++++++++++++ > include/drm/drm_crtc_helper.h | 1 + > 2 files changed, 21 insertions(+) > > diff --git a/drivers/gpu/drm/drm_probe_helper.c > b/drivers/gpu/drm/drm_probe_helper.c > index 6dc2dde5b672..7a6b2dc08913 100644 > --- a/drivers/gpu/drm/drm_probe_helper.c > +++ b/drivers/gpu/drm/drm_probe_helper.c > @@ -654,6 +654,26 @@ static void output_poll_execute(struct work_struct > *work) > schedule_delayed_work(delayed_work, > DRM_OUTPUT_POLL_PERIOD); > } > > +/** > + * drm_kms_helper_is_poll_worker - is %current task an output poll worker? > + * > + * Determine if %current task is an output poll worker. This can be used > + * to select distinct code paths for output polling versus other contexts. > + * > + * One use case is to avoid a deadlock between the output poll worker and > + * the autosuspend worker wherein the latter waits for polling to finish > + * upon calling drm_kms_helper_poll_disable(), while the former waits for > + * runtime suspend to finish upon calling pm_runtime_get_sync() in a > + * connector ->detect hook. > + */ > +bool drm_kms_helper_is_poll_worker(void) > +{ > + struct work_struct *work = current_work(); > + > + return work && work->func == output_poll_execute; > +} > +EXPORT_SYMBOL(drm_kms_helper_is_poll_worker); > + > /** > * drm_kms_helper_poll_disable - disable output polling > * @dev: drm_device > diff --git a/include/drm/drm_crtc_helper.h b/include/drm/drm_crtc_helper.h > index 76e237bd989b..6914633037a5 100644 > --- a/include/drm/drm_crtc_helper.h > +++ b/include/drm/drm_crtc_helper.h > @@ -77,5 +77,6 @@ void drm_kms_helper_hotplug_event(struct drm_device *dev); > > void drm_kms_helper_poll_disable(struct drm_device *dev); > void drm_kms_helper_poll_enable(struct drm_device *dev); > +bool drm_kms_helper_is_poll_worker(void); > > #endif -- Cheers, Lyude Paul _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel