[Intel-gfx] [PATCH 5/8] drm/i915: Protect request retirement with timeline->mutex

[Matthew Auld]

On Wed, 14 Aug 2019 at 10:28, Chris Wilson <chris at chris-wilson.co.uk> wrote:
>
> Forgo the struct_mutex requirement for request retirement as we have
> been transitioning over to only using the timeline->mutex for
> controlling the lifetime of a request on that timeline.
>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> ---
>  .../gpu/drm/i915/gem/i915_gem_execbuffer.c    | 183 ++++++++++--------
>  drivers/gpu/drm/i915/gt/intel_context.h       |  18 +-
>  drivers/gpu/drm/i915/gt/intel_engine_cs.c     |   1 -
>  drivers/gpu/drm/i915/gt/intel_engine_types.h  |   3 -
>  drivers/gpu/drm/i915/gt/intel_gt.c            |   2 -
>  drivers/gpu/drm/i915/gt/intel_gt_types.h      |   2 -
>  drivers/gpu/drm/i915/gt/intel_lrc.c           |   1 +
>  drivers/gpu/drm/i915/gt/intel_ringbuffer.c    |  19 +-
>  drivers/gpu/drm/i915/gt/mock_engine.c         |   1 -
>  drivers/gpu/drm/i915/gt/selftest_context.c    |   9 +-
>  drivers/gpu/drm/i915/i915_request.c           | 156 +++++++--------
>  drivers/gpu/drm/i915/i915_request.h           |   3 -
>  12 files changed, 209 insertions(+), 189 deletions(-)
>

>  bool i915_retire_requests(struct drm_i915_private *i915)
>  {
> -       struct intel_ring *ring, *tmp;
> +       struct intel_gt_timelines *timelines = &i915->gt.timelines;
> +       struct intel_timeline *tl, *tn;
> +       LIST_HEAD(free);
> +
> +       spin_lock(&timelines->lock);
> +       list_for_each_entry_safe(tl, tn, &timelines->active_list, link) {
> +               if (!mutex_trylock(&tl->mutex))
> +                       continue;
>
> -       lockdep_assert_held(&i915->drm.struct_mutex);
> +               intel_timeline_get(tl);
> +               GEM_BUG_ON(!tl->active_count);
> +               tl->active_count++; /* pin the list element */
> +               spin_unlock(&timelines->lock);
>
> -       list_for_each_entry_safe(ring, tmp,
> -                                &i915->gt.active_rings, active_link) {
> -               intel_ring_get(ring); /* last rq holds reference! */
> -               ring_retire_requests(ring);
> -               intel_ring_put(ring);
> +               retire_requests(tl);
> +
> +               spin_lock(&timelines->lock);
> +
> +               /* Restart iteration after dropping lock */
> +               list_safe_reset_next(tl, tn, link);

That's a new one.

"Several hours later",
Reviewed-by: Matthew Auld <matthew.auld at intel.com>