On Mon, Feb 12, 2018 at 12:46:11PM -0500, Lyude Paul wrote: > On Sun, 2018-02-11 at 10:38 +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. [snip] > > +/** > > + * 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. > > + */ > > For this, it would be worth explicitly noting in the comments herethat this > should be called by DRM drivers in order to prevent racing with hotplug > polling workers, so that new drivers in the future can avoid implementing this > race condition in their driver.
Good point, I've just sent out a v2 to address your comment. Let me know if this isn't what you had in mind. It may also be worth to expand the DOC section at the top of drm_probe_helper.c to explain the interaction between polling and runtime suspend in more detail, but I think this is better done in a separate patch to keep the present patch small and thus easily backportable to stable. Thanks a lot for the review, Lukas _______________________________________________ dri-devel mailing list email@example.com https://lists.freedesktop.org/mailman/listinfo/dri-devel