[PATCH 3/6] drm/i915: Only track live rings for retiring

[Chris Wilson <chris@chris-wilson.co.uk>]

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@linux.intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
---
 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);
 	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));
+	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 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;
 
 	u32 head;
 	u32 tail;
diff --git a/drivers/gpu/drm/i915/selftests/mock_engine.c b/drivers/gpu/drm/i915/selftests/mock_engine.c
index a0bc324edadd..74a88913623f 100644
--- a/drivers/gpu/drm/i915/selftests/mock_engine.c
+++ b/drivers/gpu/drm/i915/selftests/mock_engine.c
@@ -140,15 +140,11 @@ static struct intel_ring *mock_ring(struct intel_engine_cs *engine)
 	INIT_LIST_HEAD(&ring->request_list);
 	intel_ring_update_space(ring);
 
-	list_add(&ring->link, &engine->i915->gt.rings);
-
 	return ring;
 }
 
 static void mock_ring_free(struct intel_ring *ring)
 {
-	list_del(&ring->link);
-
 	kfree(ring);
 }
 
diff --git a/drivers/gpu/drm/i915/selftests/mock_gem_device.c b/drivers/gpu/drm/i915/selftests/mock_gem_device.c
index ac4bacf8b5b9..9335b09d8b04 100644
--- a/drivers/gpu/drm/i915/selftests/mock_gem_device.c
+++ b/drivers/gpu/drm/i915/selftests/mock_gem_device.c
@@ -225,7 +225,7 @@ struct drm_i915_private *mock_gem_device(void)
 		goto err_dependencies;
 
 	mutex_lock(&i915->drm.struct_mutex);
-	INIT_LIST_HEAD(&i915->gt.rings);
+	INIT_LIST_HEAD(&i915->gt.live_rings);
 	INIT_LIST_HEAD(&i915->gt.timelines);
 	err = i915_gem_timeline_init__global(i915);
 	if (err) {
-- 
2.17.0

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