[41/45] drm/i915: Keep contexts pinned until after the next kernel context switch

Submitted by Chris Wilson on April 25, 2019, 9:20 a.m.

Details

Message ID 20190425092004.9995-41-chris@chris-wilson.co.uk
State New
Headers show
Series "Series without cover letter" ( rev: 2 1 ) in Intel GFX

Browsing this patch as part of:
"Series without cover letter" rev 2 in Intel GFX
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Commit Message

Chris Wilson April 25, 2019, 9:20 a.m.
We need to keep the context image pinned in memory until after the GPU
has finished writing into it. Since it continues to write as we signal
the final breadcrumb, we need to keep it pinned until the request after
it is complete. Currently we know the order in which requests execute on
each engine, and so to remove that presumption we need to identify a
request/context-switch we know must occur after our completion. Any
request queued after the signal must imply a context switch, for
simplicity we use a fresh request from the kernel context.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/gem/i915_gem_context.c   | 24 ++----
 drivers/gpu/drm/i915/gem/i915_gem_context.h   |  1 -
 drivers/gpu/drm/i915/gem/i915_gem_pm.c        | 17 ++++
 drivers/gpu/drm/i915/gt/intel_context.c       | 80 +++++++++++++++---
 drivers/gpu/drm/i915/gt/intel_context.h       |  3 +
 drivers/gpu/drm/i915/gt/intel_context_types.h |  6 +-
 drivers/gpu/drm/i915/gt/intel_engine.h        |  2 -
 drivers/gpu/drm/i915/gt/intel_engine_cs.c     | 23 +-----
 drivers/gpu/drm/i915/gt/intel_engine_pm.c     |  2 +
 drivers/gpu/drm/i915/gt/intel_engine_types.h  | 13 +--
 drivers/gpu/drm/i915/gt/intel_lrc.c           | 62 ++------------
 drivers/gpu/drm/i915/gt/intel_ringbuffer.c    | 44 +---------
 drivers/gpu/drm/i915/gt/mock_engine.c         | 11 +--
 drivers/gpu/drm/i915/i915_active.c            | 81 ++++++++++++++++++-
 drivers/gpu/drm/i915/i915_active.h            |  5 ++
 drivers/gpu/drm/i915/i915_active_types.h      |  3 +
 drivers/gpu/drm/i915/i915_gem.c               |  4 -
 drivers/gpu/drm/i915/i915_request.c           | 15 ----
 .../gpu/drm/i915/selftests/mock_gem_device.c  |  1 -
 19 files changed, 213 insertions(+), 184 deletions(-)

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diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
index d4f13278d5b6..3d0a7af096f6 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
@@ -676,17 +676,6 @@  int i915_gem_contexts_init(struct drm_i915_private *dev_priv)
 	return 0;
 }
 
-void i915_gem_contexts_lost(struct drm_i915_private *dev_priv)
-{
-	struct intel_engine_cs *engine;
-	enum intel_engine_id id;
-
-	lockdep_assert_held(&dev_priv->drm.struct_mutex);
-
-	for_each_engine(engine, dev_priv, id)
-		intel_engine_lost_context(engine);
-}
-
 void i915_gem_contexts_fini(struct drm_i915_private *i915)
 {
 	lockdep_assert_held(&i915->drm.struct_mutex);
@@ -1174,10 +1163,6 @@  gen8_modify_rpcs(struct intel_context *ce, struct intel_sseu sseu)
 	if (ret)
 		goto out_add;
 
-	ret = gen8_emit_rpcs_config(rq, ce, sseu);
-	if (ret)
-		goto out_add;
-
 	/*
 	 * Guarantee context image and the timeline remains pinned until the
 	 * modifying request is retired by setting the ce activity tracker.
@@ -1185,9 +1170,12 @@  gen8_modify_rpcs(struct intel_context *ce, struct intel_sseu sseu)
 	 * But we only need to take one pin on the account of it. Or in other
 	 * words transfer the pinned ce object to tracked active request.
 	 */
-	if (!i915_active_request_isset(&ce->active_tracker))
-		__intel_context_pin(ce);
-	__i915_active_request_set(&ce->active_tracker, rq);
+	GEM_BUG_ON(i915_active_is_idle(&ce->active));
+	ret = i915_active_ref(&ce->active, rq->fence.context, rq);
+	if (ret)
+		goto out_add;
+
+	ret = gen8_emit_rpcs_config(rq, ce, sseu);
 
 out_add:
 	i915_request_add(rq);
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.h b/drivers/gpu/drm/i915/gem/i915_gem_context.h
index 630392c77e48..9691dd062f72 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_context.h
+++ b/drivers/gpu/drm/i915/gem/i915_gem_context.h
@@ -134,7 +134,6 @@  static inline bool i915_gem_context_is_kernel(struct i915_gem_context *ctx)
 
 /* i915_gem_context.c */
 int __must_check i915_gem_contexts_init(struct drm_i915_private *dev_priv);
-void i915_gem_contexts_lost(struct drm_i915_private *dev_priv);
 void i915_gem_contexts_fini(struct drm_i915_private *dev_priv);
 
 int i915_gem_context_open(struct drm_i915_private *i915,
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pm.c b/drivers/gpu/drm/i915/gem/i915_gem_pm.c
index 7e3511773fc1..6e8f86de1ed9 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_pm.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_pm.c
@@ -10,6 +10,22 @@ 
 #include "i915_drv.h"
 #include "i915_globals.h"
 
+static void call_idle_barriers(struct intel_engine_cs *engine)
+{
+	struct llist_node *node, *next;
+
+	llist_for_each_safe(node, next, llist_del_all(&engine->barrier_tasks)) {
+		struct i915_active_request *active =
+			container_of((struct list_head *)node,
+				     typeof(*active), link);
+
+		INIT_LIST_HEAD(&active->link);
+		RCU_INIT_POINTER(active->request, NULL);
+
+		active->retire(active, NULL);
+	}
+}
+
 static void i915_gem_park(struct drm_i915_private *i915)
 {
 	struct intel_engine_cs *engine;
@@ -33,6 +49,7 @@  static void i915_gem_park(struct drm_i915_private *i915)
 		}
 		tasklet_kill(&engine->execlists.tasklet);
 
+		call_idle_barriers(engine); /* cleanup after wedging */
 		i915_gem_batch_pool_fini(&engine->batch_pool);
 	}
 
diff --git a/drivers/gpu/drm/i915/gt/intel_context.c b/drivers/gpu/drm/i915/gt/intel_context.c
index 7e2b18ddda19..0102f6bb62ec 100644
--- a/drivers/gpu/drm/i915/gt/intel_context.c
+++ b/drivers/gpu/drm/i915/gt/intel_context.c
@@ -61,7 +61,6 @@  int __intel_context_do_pin(struct intel_context *ce)
 
 		i915_gem_context_get(ce->gem_context); /* for ctx->ppgtt */
 
-		intel_context_get(ce);
 		smp_mb__before_atomic(); /* flush pin before it is visible */
 	}
 
@@ -89,20 +88,45 @@  void intel_context_unpin(struct intel_context *ce)
 		ce->ops->unpin(ce);
 
 		i915_gem_context_put(ce->gem_context);
-		intel_context_put(ce);
+		intel_context_inactive(ce);
 	}
 
 	mutex_unlock(&ce->pin_mutex);
 	intel_context_put(ce);
 }
 
-static void intel_context_retire(struct i915_active_request *active,
-				 struct i915_request *rq)
+static int __context_pin_state(struct i915_vma *vma, unsigned long flags)
 {
-	struct intel_context *ce =
-		container_of(active, typeof(*ce), active_tracker);
+	int err;
 
-	intel_context_unpin(ce);
+	err = i915_vma_pin(vma, 0, 0, flags | PIN_GLOBAL);
+	if (err)
+		return err;
+
+	/*
+	 * And mark it as a globally pinned object to let the shrinker know
+	 * it cannot reclaim the object until we release it.
+	 */
+	vma->obj->pin_global++;
+	vma->obj->mm.dirty = true;
+
+	return 0;
+}
+
+static void __context_unpin_state(struct i915_vma *vma)
+{
+	vma->obj->pin_global--;
+	__i915_vma_unpin(vma);
+}
+
+static void intel_context_retire(struct i915_active *active)
+{
+	struct intel_context *ce = container_of(active, typeof(*ce), active);
+
+	if (ce->state)
+		__context_unpin_state(ce->state);
+
+	intel_context_put(ce);
 }
 
 void
@@ -124,8 +148,46 @@  intel_context_init(struct intel_context *ce,
 
 	mutex_init(&ce->pin_mutex);
 
-	i915_active_request_init(&ce->active_tracker,
-				 NULL, intel_context_retire);
+	i915_active_init(ctx->i915, &ce->active, intel_context_retire);
+}
+
+int intel_context_active(struct intel_context *ce, unsigned long flags)
+{
+	int err;
+
+	if (!i915_active_acquire(&ce->active))
+		return 0;
+
+	intel_context_get(ce);
+
+	if (!ce->state)
+		return 0;
+
+	err = __context_pin_state(ce->state, flags);
+	if (err) {
+		i915_active_cancel(&ce->active);
+		intel_context_put(ce);
+		return err;
+	}
+
+	/* Preallocate tracking nodes */
+	if (!i915_gem_context_is_kernel(ce->gem_context)) {
+		err = i915_active_acquire_preallocate_barrier(&ce->active,
+							      ce->engine);
+		if (err) {
+			i915_active_release(&ce->active);
+			return err;
+		}
+	}
+
+	return 0;
+}
+
+void intel_context_inactive(struct intel_context *ce)
+{
+	/* Nodes preallocated in intel_context_active() */
+	i915_active_acquire_barrier(&ce->active);
+	i915_active_release(&ce->active);
 }
 
 static void i915_global_context_shrink(void)
diff --git a/drivers/gpu/drm/i915/gt/intel_context.h b/drivers/gpu/drm/i915/gt/intel_context.h
index 63392c88cd98..e71629f7c2e0 100644
--- a/drivers/gpu/drm/i915/gt/intel_context.h
+++ b/drivers/gpu/drm/i915/gt/intel_context.h
@@ -102,6 +102,9 @@  static inline void intel_context_exit(struct intel_context *ce)
 		ce->ops->exit(ce);
 }
 
+int intel_context_active(struct intel_context *ce, unsigned long flags);
+void intel_context_inactive(struct intel_context *ce);
+
 static inline struct intel_context *intel_context_get(struct intel_context *ce)
 {
 	kref_get(&ce->ref);
diff --git a/drivers/gpu/drm/i915/gt/intel_context_types.h b/drivers/gpu/drm/i915/gt/intel_context_types.h
index 47f2970ab5b7..92401d25764b 100644
--- a/drivers/gpu/drm/i915/gt/intel_context_types.h
+++ b/drivers/gpu/drm/i915/gt/intel_context_types.h
@@ -53,10 +53,10 @@  struct intel_context {
 	struct mutex pin_mutex; /* guards pinning and associated on-gpuing */
 
 	/**
-	 * active_tracker: Active tracker for the external rq activity
-	 * on this intel_context object.
+	 * active: Active tracker for the rq activity (inc. external) on this
+	 * intel_context object.
 	 */
-	struct i915_active_request active_tracker;
+	struct i915_active active;
 
 	const struct intel_context_ops *ops;
 
diff --git a/drivers/gpu/drm/i915/gt/intel_engine.h b/drivers/gpu/drm/i915/gt/intel_engine.h
index f5b0f27cecb6..89463e18cdcc 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine.h
+++ b/drivers/gpu/drm/i915/gt/intel_engine.h
@@ -468,8 +468,6 @@  static inline void intel_engine_reset(struct intel_engine_cs *engine,
 bool intel_engine_is_idle(struct intel_engine_cs *engine);
 bool intel_engines_are_idle(struct drm_i915_private *dev_priv);
 
-void intel_engine_lost_context(struct intel_engine_cs *engine);
-
 void intel_engines_reset_default_submission(struct drm_i915_private *i915);
 unsigned int intel_engines_has_context_isolation(struct drm_i915_private *i915);
 
diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
index 5eef7d3bf7e3..62914e796248 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
@@ -542,6 +542,8 @@  static int intel_engine_setup_common(struct intel_engine_cs *engine)
 {
 	int err;
 
+	init_llist_head(&engine->barrier_tasks);
+
 	err = init_status_page(engine);
 	if (err)
 		return err;
@@ -797,6 +799,7 @@  void intel_engine_cleanup_common(struct intel_engine_cs *engine)
 	if (engine->preempt_context)
 		intel_context_unpin(engine->preempt_context);
 	intel_context_unpin(engine->kernel_context);
+	GEM_BUG_ON(!llist_empty(&engine->barrier_tasks));
 
 	i915_timeline_fini(&engine->timeline);
 
@@ -1122,26 +1125,6 @@  void intel_engines_reset_default_submission(struct drm_i915_private *i915)
 		engine->set_default_submission(engine);
 }
 
-/**
- * intel_engine_lost_context: called when the GPU is reset into unknown state
- * @engine: the engine
- *
- * We have either reset the GPU or otherwise about to lose state tracking of
- * the current GPU logical state (e.g. suspend). On next use, it is therefore
- * imperative that we make no presumptions about the current state and load
- * from scratch.
- */
-void intel_engine_lost_context(struct intel_engine_cs *engine)
-{
-	struct intel_context *ce;
-
-	lockdep_assert_held(&engine->i915->drm.struct_mutex);
-
-	ce = fetch_and_zero(&engine->last_retired_context);
-	if (ce)
-		intel_context_unpin(ce);
-}
-
 bool intel_engine_can_store_dword(struct intel_engine_cs *engine)
 {
 	switch (INTEL_GEN(engine->i915)) {
diff --git a/drivers/gpu/drm/i915/gt/intel_engine_pm.c b/drivers/gpu/drm/i915/gt/intel_engine_pm.c
index 3976aea3c1d1..2abc2c810e28 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_pm.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_pm.c
@@ -71,6 +71,8 @@  static bool switch_to_kernel_context(struct intel_engine_cs *engine)
 
 	/* Check again on the next retirement. */
 	engine->wakeref_serial = engine->serial + 1;
+
+	i915_request_add_barriers(rq);
 	__i915_request_commit(rq);
 
 	return false;
diff --git a/drivers/gpu/drm/i915/gt/intel_engine_types.h b/drivers/gpu/drm/i915/gt/intel_engine_types.h
index ae73c6596d08..bcede4ddc5ba 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_types.h
+++ b/drivers/gpu/drm/i915/gt/intel_engine_types.h
@@ -11,6 +11,7 @@ 
 #include <linux/irq_work.h>
 #include <linux/kref.h>
 #include <linux/list.h>
+#include <linux/llist.h>
 #include <linux/types.h>
 
 #include "i915_gem.h"
@@ -286,6 +287,7 @@  struct intel_engine_cs {
 	struct intel_ring *buffer;
 
 	struct i915_timeline timeline;
+	struct llist_head barrier_tasks;
 
 	struct intel_context *kernel_context; /* pinned */
 	struct intel_context *preempt_context; /* pinned; optional */
@@ -433,17 +435,6 @@  struct intel_engine_cs {
 
 	struct intel_engine_execlists execlists;
 
-	/* Contexts are pinned whilst they are active on the GPU. The last
-	 * context executed remains active whilst the GPU is idle - the
-	 * switch away and write to the context object only occurs on the
-	 * next execution.  Contexts are only unpinned on retirement of the
-	 * following request ensuring that we can always write to the object
-	 * on the context switch even after idling. Across suspend, we switch
-	 * to the kernel context and trash it as the save may not happen
-	 * before the hardware is powered down.
-	 */
-	struct intel_context *last_retired_context;
-
 	/* status_notifier: list of callbacks for context-switch changes */
 	struct atomic_notifier_head context_status_notifier;
 
diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
index b277c0750943..07c7b6a5a596 100644
--- a/drivers/gpu/drm/i915/gt/intel_lrc.c
+++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
@@ -1441,60 +1441,11 @@  static void execlists_context_destroy(struct kref *kref)
 	intel_context_free(ce);
 }
 
-static int __context_pin(struct i915_vma *vma)
-{
-	unsigned int flags;
-	int err;
-
-	flags = PIN_GLOBAL | PIN_HIGH;
-	flags |= PIN_OFFSET_BIAS | i915_ggtt_pin_bias(vma);
-
-	err = i915_vma_pin(vma, 0, 0, flags);
-	if (err)
-		return err;
-
-	vma->obj->pin_global++;
-	vma->obj->mm.dirty = true;
-
-	return 0;
-}
-
-static void __context_unpin(struct i915_vma *vma)
-{
-	vma->obj->pin_global--;
-	__i915_vma_unpin(vma);
-}
-
 static void execlists_context_unpin(struct intel_context *ce)
 {
-	struct intel_engine_cs *engine;
-
-	/*
-	 * The tasklet may still be using a pointer to our state, via an
-	 * old request. However, since we know we only unpin the context
-	 * on retirement of the following request, we know that the last
-	 * request referencing us will have had a completion CS interrupt.
-	 * If we see that it is still active, it means that the tasklet hasn't
-	 * had the chance to run yet; let it run before we teardown the
-	 * reference it may use.
-	 */
-	engine = READ_ONCE(ce->inflight);
-	if (unlikely(engine)) {
-		unsigned long flags;
-
-		spin_lock_irqsave(&engine->timeline.lock, flags);
-		process_csb(engine);
-		spin_unlock_irqrestore(&engine->timeline.lock, flags);
-
-		GEM_BUG_ON(READ_ONCE(ce->inflight));
-	}
-
 	i915_gem_context_unpin_hw_id(ce->gem_context);
-
-	intel_ring_unpin(ce->ring);
-
 	i915_gem_object_unpin_map(ce->state->obj);
-	__context_unpin(ce->state);
+	intel_ring_unpin(ce->ring);
 }
 
 static void
@@ -1531,7 +1482,10 @@  __execlists_context_pin(struct intel_context *ce,
 		goto err;
 	GEM_BUG_ON(!ce->state);
 
-	ret = __context_pin(ce->state);
+	ret = intel_context_active(ce,
+				   engine->i915->ggtt.pin_bias |
+				   PIN_OFFSET_BIAS |
+				   PIN_HIGH);
 	if (ret)
 		goto err;
 
@@ -1540,7 +1494,7 @@  __execlists_context_pin(struct intel_context *ce,
 					I915_MAP_OVERRIDE);
 	if (IS_ERR(vaddr)) {
 		ret = PTR_ERR(vaddr);
-		goto unpin_vma;
+		goto unpin_active;
 	}
 
 	ret = intel_ring_pin(ce->ring);
@@ -1561,8 +1515,8 @@  __execlists_context_pin(struct intel_context *ce,
 	intel_ring_unpin(ce->ring);
 unpin_map:
 	i915_gem_object_unpin_map(ce->state->obj);
-unpin_vma:
-	__context_unpin(ce->state);
+unpin_active:
+	intel_context_inactive(ce);
 err:
 	return ret;
 }
diff --git a/drivers/gpu/drm/i915/gt/intel_ringbuffer.c b/drivers/gpu/drm/i915/gt/intel_ringbuffer.c
index 62ad585531b8..b539463931c0 100644
--- a/drivers/gpu/drm/i915/gt/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/gt/intel_ringbuffer.c
@@ -1363,45 +1363,9 @@  static void __context_unpin_ppgtt(struct i915_gem_context *ctx)
 		gen6_ppgtt_unpin(ppgtt);
 }
 
-static int __context_pin(struct intel_context *ce)
-{
-	struct i915_vma *vma;
-	int err;
-
-	vma = ce->state;
-	if (!vma)
-		return 0;
-
-	err = i915_vma_pin(vma, 0, 0, PIN_GLOBAL | PIN_HIGH);
-	if (err)
-		return err;
-
-	/*
-	 * And mark is as a globally pinned object to let the shrinker know
-	 * it cannot reclaim the object until we release it.
-	 */
-	vma->obj->pin_global++;
-	vma->obj->mm.dirty = true;
-
-	return 0;
-}
-
-static void __context_unpin(struct intel_context *ce)
-{
-	struct i915_vma *vma;
-
-	vma = ce->state;
-	if (!vma)
-		return;
-
-	vma->obj->pin_global--;
-	i915_vma_unpin(vma);
-}
-
 static void ring_context_unpin(struct intel_context *ce)
 {
 	__context_unpin_ppgtt(ce->gem_context);
-	__context_unpin(ce);
 }
 
 static struct i915_vma *
@@ -1491,18 +1455,18 @@  static int ring_context_pin(struct intel_context *ce)
 		ce->state = vma;
 	}
 
-	err = __context_pin(ce);
+	err = intel_context_active(ce, PIN_HIGH);
 	if (err)
 		return err;
 
 	err = __context_pin_ppgtt(ce->gem_context);
 	if (err)
-		goto err_unpin;
+		goto err_active;
 
 	return 0;
 
-err_unpin:
-	__context_unpin(ce);
+err_active:
+	intel_context_inactive(ce);
 	return err;
 }
 
diff --git a/drivers/gpu/drm/i915/gt/mock_engine.c b/drivers/gpu/drm/i915/gt/mock_engine.c
index 6d7562769eb2..b7675ef18523 100644
--- a/drivers/gpu/drm/i915/gt/mock_engine.c
+++ b/drivers/gpu/drm/i915/gt/mock_engine.c
@@ -146,12 +146,18 @@  static void mock_context_destroy(struct kref *ref)
 
 static int mock_context_pin(struct intel_context *ce)
 {
+	int ret;
+
 	if (!ce->ring) {
 		ce->ring = mock_ring(ce->engine);
 		if (!ce->ring)
 			return -ENOMEM;
 	}
 
+	ret = intel_context_active(ce, PIN_HIGH);
+	if (ret)
+		return ret;
+
 	mock_timeline_pin(ce->ring->timeline);
 	return 0;
 }
@@ -328,14 +334,9 @@  void mock_engine_free(struct intel_engine_cs *engine)
 {
 	struct mock_engine *mock =
 		container_of(engine, typeof(*mock), base);
-	struct intel_context *ce;
 
 	GEM_BUG_ON(timer_pending(&mock->hw_delay));
 
-	ce = fetch_and_zero(&engine->last_retired_context);
-	if (ce)
-		intel_context_unpin(ce);
-
 	intel_context_unpin(engine->kernel_context);
 
 	intel_engine_fini_breadcrumbs(engine);
diff --git a/drivers/gpu/drm/i915/i915_active.c b/drivers/gpu/drm/i915/i915_active.c
index 863ae12707ba..563299e50901 100644
--- a/drivers/gpu/drm/i915/i915_active.c
+++ b/drivers/gpu/drm/i915/i915_active.c
@@ -100,7 +100,7 @@  active_instance(struct i915_active *ref, u64 idx)
 		parent = *p;
 
 		node = rb_entry(parent, struct active_node, node);
-		if (node->timeline == idx)
+		if (node->timeline == idx && !IS_ERR(node->base.request))
 			goto replace;
 
 		if (node->timeline < idx)
@@ -157,6 +157,7 @@  void i915_active_init(struct drm_i915_private *i915,
 	ref->retire = retire;
 	ref->tree = RB_ROOT;
 	i915_active_request_init(&ref->last, NULL, last_retire);
+	init_llist_head(&ref->barriers);
 	ref->count = 0;
 }
 
@@ -263,6 +264,84 @@  void i915_active_fini(struct i915_active *ref)
 }
 #endif
 
+int i915_active_acquire_preallocate_barrier(struct i915_active *ref,
+					    struct intel_engine_cs *engine)
+{
+	struct drm_i915_private *i915 = engine->i915;
+	unsigned long tmp;
+	int err = 0;
+
+	i915_active_acquire(ref);
+	for_each_engine_masked(engine, i915, engine->mask, tmp) {
+		struct intel_context *kctx = engine->kernel_context;
+		struct active_node *node;
+
+		node = kmem_cache_alloc(global.slab_cache, GFP_KERNEL);
+		if (unlikely(!node)) {
+			err = -ENOMEM;
+			break;
+		}
+
+		i915_active_request_init(&node->base,
+					 (void *)engine, node_retire);
+		node->timeline = kctx->ring->timeline->fence_context;
+		node->ref = ref;
+		ref->count++;
+
+		llist_add((struct llist_node *)&node->base.link,
+			  &ref->barriers);
+	}
+	i915_active_release(ref);
+
+	return err;
+}
+
+void i915_active_acquire_barrier(struct i915_active *ref)
+{
+	struct llist_node *pos, *next;
+
+	i915_active_acquire(ref);
+
+	llist_for_each_safe(pos, next, llist_del_all(&ref->barriers)) {
+		struct intel_engine_cs *engine;
+		struct active_node *node;
+		struct rb_node **p, *parent;
+
+		node = container_of((struct list_head *)pos,
+				    typeof(*node), base.link);
+
+		engine = (void *)rcu_access_pointer(node->base.request);
+		RCU_INIT_POINTER(node->base.request, ERR_PTR(-EAGAIN));
+
+		parent = NULL;
+		p = &ref->tree.rb_node;
+		while (*p) {
+			parent = *p;
+			if (rb_entry(parent,
+				     struct active_node,
+				     node)->timeline < node->timeline)
+				p = &parent->rb_right;
+			else
+				p = &parent->rb_left;
+		}
+		rb_link_node(&node->node, parent, p);
+		rb_insert_color(&node->node, &ref->tree);
+
+		llist_add((struct llist_node *)&node->base.link,
+			  &engine->barrier_tasks);
+	}
+	i915_active_release(ref);
+}
+
+void i915_request_add_barriers(struct i915_request *rq)
+{
+	struct intel_engine_cs *engine = rq->engine;
+	struct llist_node *node, *next;
+
+	llist_for_each_safe(node, next, llist_del_all(&engine->barrier_tasks))
+		list_add_tail((struct list_head *)node, &rq->active_list);
+}
+
 int i915_active_request_set(struct i915_active_request *active,
 			    struct i915_request *rq)
 {
diff --git a/drivers/gpu/drm/i915/i915_active.h b/drivers/gpu/drm/i915/i915_active.h
index 7d758719ce39..d55d37673944 100644
--- a/drivers/gpu/drm/i915/i915_active.h
+++ b/drivers/gpu/drm/i915/i915_active.h
@@ -406,4 +406,9 @@  void i915_active_fini(struct i915_active *ref);
 static inline void i915_active_fini(struct i915_active *ref) { }
 #endif
 
+int i915_active_acquire_preallocate_barrier(struct i915_active *ref,
+					    struct intel_engine_cs *engine);
+void i915_active_acquire_barrier(struct i915_active *ref);
+void i915_request_add_barriers(struct i915_request *rq);
+
 #endif /* _I915_ACTIVE_H_ */
diff --git a/drivers/gpu/drm/i915/i915_active_types.h b/drivers/gpu/drm/i915/i915_active_types.h
index b679253b53a5..c025991b9233 100644
--- a/drivers/gpu/drm/i915/i915_active_types.h
+++ b/drivers/gpu/drm/i915/i915_active_types.h
@@ -7,6 +7,7 @@ 
 #ifndef _I915_ACTIVE_TYPES_H_
 #define _I915_ACTIVE_TYPES_H_
 
+#include <linux/llist.h>
 #include <linux/rbtree.h>
 #include <linux/rcupdate.h>
 
@@ -31,6 +32,8 @@  struct i915_active {
 	unsigned int count;
 
 	void (*retire)(struct i915_active *ref);
+
+	struct llist_head barriers;
 };
 
 #endif /* _I915_ACTIVE_TYPES_H_ */
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 90923fa6603d..ad944e12d8be 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1153,10 +1153,6 @@  void i915_gem_sanitize(struct drm_i915_private *i915)
 
 	intel_uncore_forcewake_put(&i915->uncore, FORCEWAKE_ALL);
 	intel_runtime_pm_put(i915, wakeref);
-
-	mutex_lock(&i915->drm.struct_mutex);
-	i915_gem_contexts_lost(i915);
-	mutex_unlock(&i915->drm.struct_mutex);
 }
 
 void i915_gem_init_swizzling(struct drm_i915_private *dev_priv)
diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
index dc5bce2c0504..d69ea896ef87 100644
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -213,18 +213,6 @@  static void __retire_engine_request(struct intel_engine_cs *engine,
 	spin_unlock(&rq->lock);
 
 	local_irq_enable();
-
-	/*
-	 * The backing object for the context is done after switching to the
-	 * *next* context. Therefore we cannot retire the previous context until
-	 * the next context has already started running. However, since we
-	 * cannot take the required locks at i915_request_submit() we
-	 * defer the unpinning of the active context to now, retirement of
-	 * the subsequent request.
-	 */
-	if (engine->last_retired_context)
-		intel_context_unpin(engine->last_retired_context);
-	engine->last_retired_context = rq->hw_context;
 }
 
 static void __retire_engine_upto(struct intel_engine_cs *engine,
@@ -753,9 +741,6 @@  __i915_request_create(struct intel_context *ce, gfp_t gfp)
 
 	rq->infix = rq->ring->emit; /* end of header; start of user payload */
 
-	/* Keep a second pin for the dual retirement along engine and ring */
-	__intel_context_pin(ce);
-
 	intel_context_mark_active(ce);
 	return rq;
 
diff --git a/drivers/gpu/drm/i915/selftests/mock_gem_device.c b/drivers/gpu/drm/i915/selftests/mock_gem_device.c
index ca8d73e6414e..23c02f33f96b 100644
--- a/drivers/gpu/drm/i915/selftests/mock_gem_device.c
+++ b/drivers/gpu/drm/i915/selftests/mock_gem_device.c
@@ -56,7 +56,6 @@  static void mock_device_release(struct drm_device *dev)
 
 	mutex_lock(&i915->drm.struct_mutex);
 	mock_device_flush(i915);
-	i915_gem_contexts_lost(i915);
 	mutex_unlock(&i915->drm.struct_mutex);
 
 	drain_delayed_work(&i915->gem.retire_work);