[43/50] drm/i915: Move list of timelines under its own lock

Submitted by Chris Wilson on Jan. 11, 2019, 11:53 p.m.

Details

Message ID 20190111235332.2032-43-chris@chris-wilson.co.uk
State New
Series "Series without cover letter"
Headers show

Commit Message

Chris Wilson Jan. 11, 2019, 11:53 p.m.
Currently, the list of timelines is serialised by the struct_mutex, but
to alleviate difficulties with using that mutex in future, move the
list management under its own dedicated mutex.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_drv.h               |  1 +
 drivers/gpu/drm/i915/i915_gem.c               | 89 +++++++++----------
 drivers/gpu/drm/i915/i915_timeline.c          | 27 +++++-
 drivers/gpu/drm/i915/i915_timeline.h          |  3 +
 drivers/gpu/drm/i915/i915_vma.c               |  6 ++
 .../gpu/drm/i915/selftests/mock_gem_device.c  |  7 +-
 .../gpu/drm/i915/selftests/mock_timeline.c    |  3 +-
 7 files changed, 82 insertions(+), 54 deletions(-)

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diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index c7f1808757e2..34c8bc5d2fd4 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1971,6 +1971,7 @@  struct drm_i915_private {
 		void (*resume)(struct drm_i915_private *);
 		void (*cleanup_engine)(struct intel_engine_cs *engine);
 
+		struct mutex timeline_lock;
 		struct list_head timelines;
 
 		struct list_head active_rings;
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 9e2f59b84e7b..9c418fe3680d 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3222,33 +3222,6 @@  i915_gem_wait_ioctl(struct drm_device *dev, void *data, struct drm_file *file)
 	return ret;
 }
 
-static long wait_for_timeline(struct i915_timeline *tl,
-			      unsigned int flags, long timeout)
-{
-	struct i915_request *rq;
-
-	rq = i915_gem_active_get_unlocked(&tl->last_request);
-	if (!rq)
-		return timeout;
-
-	/*
-	 * "Race-to-idle".
-	 *
-	 * Switching to the kernel context is often used a synchronous
-	 * step prior to idling, e.g. in suspend for flushing all
-	 * current operations to memory before sleeping. These we
-	 * want to complete as quickly as possible to avoid prolonged
-	 * stalls, so allow the gpu to boost to maximum clocks.
-	 */
-	if (flags & I915_WAIT_FOR_IDLE_BOOST)
-		gen6_rps_boost(rq, NULL);
-
-	timeout = i915_request_wait(rq, flags, timeout);
-	i915_request_put(rq);
-
-	return timeout;
-}
-
 static int wait_for_engines(struct drm_i915_private *i915)
 {
 	if (wait_for(intel_engines_are_idle(i915), I915_IDLE_ENGINES_TIMEOUT)) {
@@ -3265,6 +3238,8 @@  static int wait_for_engines(struct drm_i915_private *i915)
 int i915_gem_wait_for_idle(struct drm_i915_private *i915,
 			   unsigned int flags, long timeout)
 {
+	struct i915_timeline *tl;
+
 	GEM_TRACE("flags=%x (%s), timeout=%ld%s\n",
 		  flags, flags & I915_WAIT_LOCKED ? "locked" : "unlocked",
 		  timeout, timeout == MAX_SCHEDULE_TIMEOUT ? " (forever)" : "");
@@ -3273,17 +3248,45 @@  int i915_gem_wait_for_idle(struct drm_i915_private *i915,
 	if (!READ_ONCE(i915->gt.awake))
 		return 0;
 
+	mutex_lock(&i915->gt.timeline_lock);
+	list_for_each_entry(tl, &i915->gt.timelines, link) {
+		struct i915_request *rq;
+
+		rq = i915_gem_active_get_unlocked(&tl->last_request);
+		if (!rq)
+			continue;
+
+		mutex_unlock(&i915->gt.timeline_lock);
+
+		/*
+		 * "Race-to-idle".
+		 *
+		 * Switching to the kernel context is often used a synchronous
+		 * step prior to idling, e.g. in suspend for flushing all
+		 * current operations to memory before sleeping. These we
+		 * want to complete as quickly as possible to avoid prolonged
+		 * stalls, so allow the gpu to boost to maximum clocks.
+		 */
+		if (flags & I915_WAIT_FOR_IDLE_BOOST)
+			gen6_rps_boost(rq, NULL);
+
+		timeout = i915_request_wait(rq, flags, timeout);
+		i915_request_put(rq);
+		if (timeout < 0)
+			return timeout;
+
+		mutex_lock(&i915->gt.timeline_lock);
+
+		/* restart after dropping the lock */
+		tl = list_entry(&i915->gt.timelines, typeof(*tl), link);
+	}
+	mutex_unlock(&i915->gt.timeline_lock);
+
 	if (flags & I915_WAIT_LOCKED) {
-		struct i915_timeline *tl;
 		int err;
 
 		lockdep_assert_held(&i915->drm.struct_mutex);
 
-		list_for_each_entry(tl, &i915->gt.timelines, link) {
-			timeout = wait_for_timeline(tl, flags, timeout);
-			if (timeout < 0)
-				return timeout;
-		}
 		if (GEM_SHOW_DEBUG() && !timeout) {
 			/* Presume that timeout was non-zero to begin with! */
 			dev_warn(&i915->drm.pdev->dev,
@@ -3297,17 +3300,6 @@  int i915_gem_wait_for_idle(struct drm_i915_private *i915,
 
 		i915_retire_requests(i915);
 		GEM_BUG_ON(i915->gt.active_requests);
-	} else {
-		struct intel_engine_cs *engine;
-		enum intel_engine_id id;
-
-		for_each_engine(engine, i915, id) {
-			struct i915_timeline *tl = &engine->timeline;
-
-			timeout = wait_for_timeline(tl, flags, timeout);
-			if (timeout < 0)
-				return timeout;
-		}
 	}
 
 	return 0;
@@ -5008,6 +5000,8 @@  int i915_gem_init(struct drm_i915_private *dev_priv)
 		dev_priv->gt.cleanup_engine = intel_engine_cleanup;
 	}
 
+	i915_timelines_init(dev_priv);
+
 	ret = i915_gem_init_userptr(dev_priv);
 	if (ret)
 		return ret;
@@ -5130,8 +5124,10 @@  int i915_gem_init(struct drm_i915_private *dev_priv)
 err_uc_misc:
 	intel_uc_fini_misc(dev_priv);
 
-	if (ret != -EIO)
+	if (ret != -EIO) {
 		i915_gem_cleanup_userptr(dev_priv);
+		i915_timelines_fini(dev_priv);
+	}
 
 	if (ret == -EIO) {
 		mutex_lock(&dev_priv->drm.struct_mutex);
@@ -5182,6 +5178,7 @@  void i915_gem_fini(struct drm_i915_private *dev_priv)
 
 	intel_uc_fini_misc(dev_priv);
 	i915_gem_cleanup_userptr(dev_priv);
+	i915_timelines_fini(dev_priv);
 
 	i915_gem_drain_freed_objects(dev_priv);
 
@@ -5284,7 +5281,6 @@  int i915_gem_init_early(struct drm_i915_private *dev_priv)
 	if (!dev_priv->priorities)
 		goto err_dependencies;
 
-	INIT_LIST_HEAD(&dev_priv->gt.timelines);
 	INIT_LIST_HEAD(&dev_priv->gt.active_rings);
 	INIT_LIST_HEAD(&dev_priv->gt.closed_vma);
 
@@ -5328,7 +5324,6 @@  void i915_gem_cleanup_early(struct drm_i915_private *dev_priv)
 	GEM_BUG_ON(!llist_empty(&dev_priv->mm.free_list));
 	GEM_BUG_ON(atomic_read(&dev_priv->mm.free_count));
 	WARN_ON(dev_priv->mm.object_count);
-	WARN_ON(!list_empty(&dev_priv->gt.timelines));
 
 	kmem_cache_destroy(dev_priv->priorities);
 	kmem_cache_destroy(dev_priv->dependencies);
diff --git a/drivers/gpu/drm/i915/i915_timeline.c b/drivers/gpu/drm/i915/i915_timeline.c
index 4667cc08c416..0434b5e0d3e1 100644
--- a/drivers/gpu/drm/i915/i915_timeline.c
+++ b/drivers/gpu/drm/i915/i915_timeline.c
@@ -13,8 +13,6 @@  void i915_timeline_init(struct drm_i915_private *i915,
 			struct i915_timeline *timeline,
 			const char *name)
 {
-	lockdep_assert_held(&i915->drm.struct_mutex);
-
 	/*
 	 * Ideally we want a set of engines on a single leaf as we expect
 	 * to mostly be tracking synchronisation between engines. It is not
@@ -23,9 +21,12 @@  void i915_timeline_init(struct drm_i915_private *i915,
 	 */
 	BUILD_BUG_ON(KSYNCMAP < I915_NUM_ENGINES);
 
+	timeline->i915 = i915;
 	timeline->name = name;
 
+	mutex_lock(&i915->gt.timeline_lock);
 	list_add(&timeline->link, &i915->gt.timelines);
+	mutex_unlock(&i915->gt.timeline_lock);
 
 	/* Called during early_init before we know how many engines there are */
 
@@ -39,6 +40,15 @@  void i915_timeline_init(struct drm_i915_private *i915,
 	i915_syncmap_init(&timeline->sync);
 }
 
+void i915_timelines_init(struct drm_i915_private *i915)
+{
+	mutex_init(&i915->gt.timeline_lock);
+	INIT_LIST_HEAD(&i915->gt.timelines);
+
+	/* via i915_gem_wait_for_idle() */
+	i915_gem_shrinker_taints_mutex(i915, &i915->gt.timeline_lock);
+}
+
 /**
  * i915_timelines_park - called when the driver idles
  * @i915: the drm_i915_private device
@@ -53,8 +63,7 @@  void i915_timelines_park(struct drm_i915_private *i915)
 {
 	struct i915_timeline *timeline;
 
-	lockdep_assert_held(&i915->drm.struct_mutex);
-
+	mutex_lock(&i915->gt.timeline_lock);
 	list_for_each_entry(timeline, &i915->gt.timelines, link) {
 		/*
 		 * All known fences are completed so we can scrap
@@ -64,6 +73,7 @@  void i915_timelines_park(struct drm_i915_private *i915)
 		 */
 		i915_syncmap_free(&timeline->sync);
 	}
+	mutex_unlock(&i915->gt.timeline_lock);
 }
 
 void i915_timeline_fini(struct i915_timeline *timeline)
@@ -72,7 +82,9 @@  void i915_timeline_fini(struct i915_timeline *timeline)
 
 	i915_syncmap_free(&timeline->sync);
 
+	mutex_lock(&timeline->i915->gt.timeline_lock);
 	list_del(&timeline->link);
+	mutex_unlock(&timeline->i915->gt.timeline_lock);
 }
 
 struct i915_timeline *
@@ -99,6 +111,13 @@  void __i915_timeline_free(struct kref *kref)
 	kfree(timeline);
 }
 
+void i915_timelines_fini(struct drm_i915_private *i915)
+{
+	GEM_BUG_ON(!list_empty(&i915->gt.timelines));
+
+	mutex_destroy(&i915->gt.timeline_lock);
+}
+
 #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
 #include "selftests/mock_timeline.c"
 #include "selftests/i915_timeline.c"
diff --git a/drivers/gpu/drm/i915/i915_timeline.h b/drivers/gpu/drm/i915/i915_timeline.h
index 38c1e15e927a..87ad2dd31c20 100644
--- a/drivers/gpu/drm/i915/i915_timeline.h
+++ b/drivers/gpu/drm/i915/i915_timeline.h
@@ -66,6 +66,7 @@  struct i915_timeline {
 
 	struct list_head link;
 	const char *name;
+	struct drm_i915_private *i915;
 
 	struct kref kref;
 };
@@ -134,6 +135,8 @@  static inline bool i915_timeline_sync_is_later(struct i915_timeline *tl,
 	return __i915_timeline_sync_is_later(tl, fence->context, fence->seqno);
 }
 
+void i915_timelines_init(struct drm_i915_private *i915);
 void i915_timelines_park(struct drm_i915_private *i915);
+void i915_timelines_fini(struct drm_i915_private *i915);
 
 #endif
diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
index 3a680fe2bb8b..d83b8ad5f859 100644
--- a/drivers/gpu/drm/i915/i915_vma.c
+++ b/drivers/gpu/drm/i915/i915_vma.c
@@ -201,6 +201,11 @@  vma_create(struct drm_i915_gem_object *obj,
 		rb = *p;
 		pos = rb_entry(rb, struct i915_vma, obj_node);
 
+		/*
+		 * If the view already exists in the tree, another thread
+		 * already created a matching vma, so return the older instance
+		 * and dispose of ours.
+		 */
 		cmp = i915_vma_compare(pos, vm, view);
 		if (cmp == 0) {
 			spin_unlock(&obj->vma.lock);
@@ -294,6 +299,7 @@  i915_vma_instance(struct drm_i915_gem_object *obj,
 	vma = vma_lookup(obj, vm, view);
 	spin_unlock(&obj->vma.lock);
 
+	/* vma_create() will resolve the race if another creates the vma */
 	if (unlikely(!vma))
 		vma = vma_create(obj, vm, view);
 
diff --git a/drivers/gpu/drm/i915/selftests/mock_gem_device.c b/drivers/gpu/drm/i915/selftests/mock_gem_device.c
index 888c6978bc54..41ae502361d7 100644
--- a/drivers/gpu/drm/i915/selftests/mock_gem_device.c
+++ b/drivers/gpu/drm/i915/selftests/mock_gem_device.c
@@ -68,13 +68,14 @@  static void mock_device_release(struct drm_device *dev)
 	i915_gem_contexts_fini(i915);
 	mutex_unlock(&i915->drm.struct_mutex);
 
+	i915_timelines_fini(i915);
+
 	drain_workqueue(i915->wq);
 	i915_gem_drain_freed_objects(i915);
 
 	mutex_lock(&i915->drm.struct_mutex);
 	mock_fini_ggtt(i915);
 	mutex_unlock(&i915->drm.struct_mutex);
-	WARN_ON(!list_empty(&i915->gt.timelines));
 
 	destroy_workqueue(i915->wq);
 
@@ -226,7 +227,8 @@  struct drm_i915_private *mock_gem_device(void)
 	if (!i915->priorities)
 		goto err_dependencies;
 
-	INIT_LIST_HEAD(&i915->gt.timelines);
+	i915_timelines_init(i915);
+
 	INIT_LIST_HEAD(&i915->gt.active_rings);
 	INIT_LIST_HEAD(&i915->gt.closed_vma);
 
@@ -253,6 +255,7 @@  struct drm_i915_private *mock_gem_device(void)
 	i915_gem_contexts_fini(i915);
 err_unlock:
 	mutex_unlock(&i915->drm.struct_mutex);
+	i915_timelines_fini(i915);
 	kmem_cache_destroy(i915->priorities);
 err_dependencies:
 	kmem_cache_destroy(i915->dependencies);
diff --git a/drivers/gpu/drm/i915/selftests/mock_timeline.c b/drivers/gpu/drm/i915/selftests/mock_timeline.c
index dcf3b16f5a07..cf39ccd9fc05 100644
--- a/drivers/gpu/drm/i915/selftests/mock_timeline.c
+++ b/drivers/gpu/drm/i915/selftests/mock_timeline.c
@@ -10,6 +10,7 @@ 
 
 void mock_timeline_init(struct i915_timeline *timeline, u64 context)
 {
+	timeline->i915 = NULL;
 	timeline->fence_context = context;
 
 	spin_lock_init(&timeline->lock);
@@ -24,5 +25,5 @@  void mock_timeline_init(struct i915_timeline *timeline, u64 context)
 
 void mock_timeline_fini(struct i915_timeline *timeline)
 {
-	i915_timeline_fini(timeline);
+	i915_syncmap_free(&timeline->sync);
 }