Quoting Sultan Alsawaf (2020-03-30 04:30:57)
> +static void engine_retire(struct work_struct *work)
> +{
> + struct intel_engine_cs *engine =
> + container_of(work, typeof(*engine), retire_work);
> + struct intel_timeline *tl = xchg(&engine->retire, NULL);
> +
> + do {
> + struct intel_timeline *next = xchg(&tl->retire, NULL);
> +
> + /*
> + * Our goal here is to retire _idle_ timelines as soon as
> + * possible (as they are idle, we do not expect userspace
> + * to be cleaning up anytime soon).
> + *
> + * If the timeline is currently locked, either it is being
> + * retired elsewhere or about to be!
> + */
iirc the backport requires the retirement to be wrapped in struct_mutex
mutex_lock(&engine->i915->drm.struct_mutex);
> + if (mutex_trylock(&tl->mutex)) {
> + retire_requests(tl);
> + mutex_unlock(&tl->mutex);
> + }
mutex_unlock(&engine->i915->drm.struct_mutex);
Now the question is whether that was for 5.3 or 5.4. I think 5.3 is
where the changes were more severe and where we switch to the 4.19
approach.
> + intel_timeline_put(tl);
> +
> + GEM_BUG_ON(!next);
> + tl = ptr_mask_bits(next, 1);
> + } while (tl);
> +}
