Quoting Tvrtko Ursulin (2018-04-23 11:25:54)
>
> On 23/04/2018 11:13, Chris Wilson wrote:
> > We don't need to track every ring for its lifetime as they are managed
> > by the contexts/engines. What we do want to track are the live rings so
> > that we can sporadically clean up requests if userspace falls behind. We
> > can simply restrict the gt->rings list to being only gt->live_rings.
> >
> > Suggested-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>
> > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/i915_drv.h | 2 +-
> > drivers/gpu/drm/i915/i915_gem.c | 3 ++-
> > drivers/gpu/drm/i915/i915_request.c | 6 +++++-
> > drivers/gpu/drm/i915/i915_utils.h | 6 ++++++
> > drivers/gpu/drm/i915/intel_ringbuffer.c | 4 ----
> > drivers/gpu/drm/i915/intel_ringbuffer.h | 2 +-
> > drivers/gpu/drm/i915/selftests/mock_engine.c | 4 ----
> > drivers/gpu/drm/i915/selftests/mock_gem_device.c | 2 +-
> > 8 files changed, 16 insertions(+), 13 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> > index 73936be90aed..a7787c2cb53c 100644
> > --- a/drivers/gpu/drm/i915/i915_drv.h
> > +++ b/drivers/gpu/drm/i915/i915_drv.h
> > @@ -2060,7 +2060,7 @@ struct drm_i915_private {
> >
> > struct i915_gem_timeline global_timeline;
> > struct list_head timelines;
> > - struct list_head rings;
> > + struct list_head live_rings;
> > u32 active_requests;
> >
> > /**
> > diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> > index 906e2395c245..0097a77fae8d 100644
> > --- a/drivers/gpu/drm/i915/i915_gem.c
> > +++ b/drivers/gpu/drm/i915/i915_gem.c
> > @@ -141,6 +141,7 @@ static u32 __i915_gem_park(struct drm_i915_private *i915)
> > {
> > lockdep_assert_held(&i915->drm.struct_mutex);
> > GEM_BUG_ON(i915->gt.active_requests);
> > + GEM_BUG_ON(!list_empty(&i915->gt.live_rings));
> >
> > if (!i915->gt.awake)
> > return I915_EPOCH_INVALID;
> > @@ -5600,7 +5601,7 @@ int i915_gem_init_early(struct drm_i915_private *dev_priv)
> > goto err_dependencies;
> >
> > mutex_lock(&dev_priv->drm.struct_mutex);
> > - INIT_LIST_HEAD(&dev_priv->gt.rings);
> > + INIT_LIST_HEAD(&dev_priv->gt.live_rings);
> > INIT_LIST_HEAD(&dev_priv->gt.timelines);
> > err = i915_gem_timeline_init__global(dev_priv);
> > mutex_unlock(&dev_priv->drm.struct_mutex);
> > diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
> > index 0bf949ec9f1a..534b8d684cef 100644
> > --- a/drivers/gpu/drm/i915/i915_request.c
> > +++ b/drivers/gpu/drm/i915/i915_request.c
> > @@ -316,6 +316,7 @@ static void advance_ring(struct i915_request *request)
> > * noops - they are safe to be replayed on a reset.
> > */
> > tail = READ_ONCE(request->tail);
> > + list_del(&ring->live);
> > } else {
> > tail = request->postfix;
> > }
> > @@ -1046,6 +1047,8 @@ void __i915_request_add(struct i915_request *request, bool flush_caches)
> > i915_gem_active_set(&timeline->last_request, request);
> >
> > list_add_tail(&request->ring_link, &ring->request_list);
> > + if (list_is_first(&request->ring_link, &ring->request_list))
> > + list_add(&ring->live, &request->i915->gt.live_rings);
>
> If you re-order the two list adds you could use list_empty and wouldn't
> have to add list_is_first.
list_is_first tallies nicely with the list_is_last used before the
corresponding list_del.
>
> > request->emitted_jiffies = jiffies;
> >
> > /*
> > @@ -1375,7 +1378,8 @@ void i915_retire_requests(struct drm_i915_private *i915)
> > if (!i915->gt.active_requests)
> > return;
> >
> > - list_for_each_entry_safe(ring, next, &i915->gt.rings, link)
> > + GEM_BUG_ON(list_empty(&i915->gt.live_rings));
>
> Maybe blank line here since the assert is not logically associated with
> the list but with the !i915.active_requests?
I was thinking list when I wrote it. It's small enough we can argue both
and both be right.
>
> > + list_for_each_entry_safe(ring, next, &i915->gt.live_rings, live)
> > ring_retire_requests(ring);
> > }
> >
> > diff --git a/drivers/gpu/drm/i915/i915_utils.h b/drivers/gpu/drm/i915/i915_utils.h
> > index 0695717522ea..00165ad55fb3 100644
> > --- a/drivers/gpu/drm/i915/i915_utils.h
> > +++ b/drivers/gpu/drm/i915/i915_utils.h
> > @@ -120,6 +120,12 @@ static inline u64 ptr_to_u64(const void *ptr)
> >
> > #include <linux/list.h>
> >
> > +static inline int list_is_first(const struct list_head *list,
> > + const struct list_head *head)
>
> Return bool if you decide you prefer to keep list_is_first?
Copy'n'paste from list_is_last().
>
> > +{
> > + return head->next == list;
> > +}
> > +
> > static inline void __list_del_many(struct list_head *head,
> > struct list_head *first)
> > {
> > diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> > index 792a2ca95872..3453e7426f6b 100644
> > --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> > +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> > @@ -1150,8 +1150,6 @@ intel_engine_create_ring(struct intel_engine_cs *engine, int size)
> > }
> > ring->vma = vma;
> >
> > - list_add(&ring->link, &engine->i915->gt.rings);
> > -
> > return ring;
> > }
> >
> > @@ -1163,8 +1161,6 @@ intel_ring_free(struct intel_ring *ring)
> > i915_vma_close(ring->vma);
> > __i915_gem_object_release_unless_active(obj);
> >
> > - list_del(&ring->link);
> > -
> > kfree(ring);
> > }
> >
> > diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
> > index d816f8dea245..fd5a6363ab1d 100644
> > --- a/drivers/gpu/drm/i915/intel_ringbuffer.h
> > +++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
> > @@ -129,7 +129,7 @@ struct intel_ring {
> > void *vaddr;
> >
> > struct list_head request_list;
> > - struct list_head link;
> > + struct list_head live;
>
> live_link?
live or active.
active_rings ties in with active_requests, so active_link here.
-Chris
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