drm/i915: Move list of timelines under its own lock

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>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190128102356.15037-5-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_drv.h

@@ -1975,7 +1975,10 @@ struct drm_i915_private {
 		void (*resume)(struct drm_i915_private *);
 		void (*cleanup_engine)(struct intel_engine_cs *engine);
 
-		struct list_head timelines;
+		struct i915_gt_timelines {
+			struct mutex mutex; /* protects list, tainted by GPU */
+			struct list_head list;
+		} timelines;
 
 		struct list_head active_rings;
 		struct list_head closed_vma;

drivers/gpu/drm/i915/i915_gem.c

@@ -3222,14 +3222,38 @@ 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,
+static int wait_for_engines(struct drm_i915_private *i915)
+{
+	if (wait_for(intel_engines_are_idle(i915), I915_IDLE_ENGINES_TIMEOUT)) {
+		dev_err(i915->drm.dev,
+			"Failed to idle engines, declaring wedged!\n");
+		GEM_TRACE_DUMP();
+		i915_gem_set_wedged(i915);
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static long
+wait_for_timelines(struct drm_i915_private *i915,
 		   unsigned int flags, long timeout)
 {
+	struct i915_gt_timelines *gt = &i915->gt.timelines;
+	struct i915_timeline *tl;
+
+	if (!READ_ONCE(i915->gt.active_requests))
+		return timeout;
+
+	mutex_lock(&gt->mutex);
+	list_for_each_entry(tl, &gt->list, link) {
 		struct i915_request *rq;
 
 		rq = i915_gem_active_get_unlocked(&tl->last_request);
 		if (!rq)
-		return timeout;
+			continue;
+
+		mutex_unlock(&gt->mutex);
 
 		/*
 		 * "Race-to-idle".
@@ -3245,21 +3269,16 @@ static long wait_for_timeline(struct i915_timeline *tl,
 
 		timeout = i915_request_wait(rq, flags, timeout);
 		i915_request_put(rq);
-
+		if (timeout < 0)
 			return timeout;
-}
 
-static int wait_for_engines(struct drm_i915_private *i915)
-{
-	if (wait_for(intel_engines_are_idle(i915), I915_IDLE_ENGINES_TIMEOUT)) {
-		dev_err(i915->drm.dev,
-			"Failed to idle engines, declaring wedged!\n");
-		GEM_TRACE_DUMP();
-		i915_gem_set_wedged(i915);
-		return -EIO;
+		/* restart after reacquiring the lock */
+		mutex_lock(&gt->mutex);
+		tl = list_entry(&gt->list, typeof(*tl), link);
 	}
+	mutex_unlock(&gt->mutex);
 
-	return 0;
+	return timeout;
 }
 
 int i915_gem_wait_for_idle(struct drm_i915_private *i915,
@@ -3273,17 +3292,15 @@ int i915_gem_wait_for_idle(struct drm_i915_private *i915,
 	if (!READ_ONCE(i915->gt.awake))
 		return 0;
 
+	timeout = wait_for_timelines(i915, flags, timeout);
+	if (timeout < 0)
+		return timeout;
+
 	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 +3314,6 @@ 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 +5014,8 @@ 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 +5138,10 @@ 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 +5192,7 @@ 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 +5295,6 @@ 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 +5338,6 @@ 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);

drivers/gpu/drm/i915/i915_reset.c

@@ -854,7 +854,8 @@ bool i915_gem_unset_wedged(struct drm_i915_private *i915)
 	 *
 	 * No more can be submitted until we reset the wedged bit.
 	 */
-	list_for_each_entry(tl, &i915->gt.timelines, link) {
+	mutex_lock(&i915->gt.timelines.mutex);
+	list_for_each_entry(tl, &i915->gt.timelines.list, link) {
 		struct i915_request *rq;
 		long timeout;
 
@@ -876,9 +877,12 @@ bool i915_gem_unset_wedged(struct drm_i915_private *i915)
 		timeout = dma_fence_default_wait(&rq->fence, true,
 						 MAX_SCHEDULE_TIMEOUT);
 		i915_request_put(rq);
-		if (timeout < 0)
+		if (timeout < 0) {
+			mutex_unlock(&i915->gt.timelines.mutex);
 			goto unlock;
 		}
+	}
+	mutex_unlock(&i915->gt.timelines.mutex);
 
 	intel_engines_sanitize(i915, false);
 

drivers/gpu/drm/i915/i915_timeline.c

@@ -13,7 +13,7 @@ void i915_timeline_init(struct drm_i915_private *i915,
 			struct i915_timeline *timeline,
 			const char *name)
 {
-	lockdep_assert_held(&i915->drm.struct_mutex);
+	struct i915_gt_timelines *gt = &i915->gt.timelines;
 
 	/*
 	 * Ideally we want a set of engines on a single leaf as we expect
@@ -23,9 +23,12 @@ void i915_timeline_init(struct drm_i915_private *i915,
 	 */
 	BUILD_BUG_ON(KSYNCMAP < I915_NUM_ENGINES);
 
+	timeline->i915 = i915;
 	timeline->name = name;
 
-	list_add(&timeline->link, &i915->gt.timelines);
+	mutex_lock(&gt->mutex);
+	list_add(&timeline->link, &gt->list);
+	mutex_unlock(&gt->mutex);
 
 	/* Called during early_init before we know how many engines there are */
 
@@ -39,6 +42,17 @@ void i915_timeline_init(struct drm_i915_private *i915,
 	i915_syncmap_init(&timeline->sync);
 }
 
+void i915_timelines_init(struct drm_i915_private *i915)
+{
+	struct i915_gt_timelines *gt = &i915->gt.timelines;
+
+	mutex_init(&gt->mutex);
+	INIT_LIST_HEAD(&gt->list);
+
+	/* via i915_gem_wait_for_idle() */
+	i915_gem_shrinker_taints_mutex(i915, &gt->mutex);
+}
+
 /**
  * i915_timelines_park - called when the driver idles
  * @i915: the drm_i915_private device
@@ -51,11 +65,11 @@ void i915_timeline_init(struct drm_i915_private *i915,
  */
 void i915_timelines_park(struct drm_i915_private *i915)
 {
+	struct i915_gt_timelines *gt = &i915->gt.timelines;
 	struct i915_timeline *timeline;
 
-	lockdep_assert_held(&i915->drm.struct_mutex);
-
-	list_for_each_entry(timeline, &i915->gt.timelines, link) {
+	mutex_lock(&gt->mutex);
+	list_for_each_entry(timeline, &gt->list, link) {
 		/*
 		 * All known fences are completed so we can scrap
 		 * the current sync point tracking and start afresh,
@@ -64,15 +78,20 @@ void i915_timelines_park(struct drm_i915_private *i915)
 		 */
 		i915_syncmap_free(&timeline->sync);
 	}
+	mutex_unlock(&gt->mutex);
 }
 
 void i915_timeline_fini(struct i915_timeline *timeline)
 {
+	struct i915_gt_timelines *gt = &timeline->i915->gt.timelines;
+
 	GEM_BUG_ON(!list_empty(&timeline->requests));
 
 	i915_syncmap_free(&timeline->sync);
 
+	mutex_lock(&gt->mutex);
 	list_del(&timeline->link);
+	mutex_unlock(&gt->mutex);
 }
 
 struct i915_timeline *
@@ -99,6 +118,15 @@ void __i915_timeline_free(struct kref *kref)
 	kfree(timeline);
 }
 
+void i915_timelines_fini(struct drm_i915_private *i915)
+{
+	struct i915_gt_timelines *gt = &i915->gt.timelines;
+
+	GEM_BUG_ON(!list_empty(&gt->list));
+
+	mutex_destroy(&gt->mutex);
+}
+
 #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
 #include "selftests/mock_timeline.c"
 #include "selftests/i915_timeline.c"

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

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->ggtt);
 	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);

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);
 }