1 files changed, 64 insertions, 41 deletions

diff --git a/drivers/gpu/drm/i915/gt/intel_gt_buffer_pool.c b/drivers/gpu/drm/i915/gt/intel_gt_buffer_pool.c
index 418ae184cecf..104cb30e8c13 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt_buffer_pool.c
+++ b/drivers/gpu/drm/i915/gt/intel_gt_buffer_pool.c
@@ -35,39 +35,65 @@ static void node_free(struct intel_gt_buffer_pool_node *node)
 {
 	i915_gem_object_put(node->obj);
 	i915_active_fini(&node->active);
-	kfree(node);
+	kfree_rcu(node, rcu);
 }
 
-static void pool_free_work(struct work_struct *wrk)
+static bool pool_free_older_than(struct intel_gt_buffer_pool *pool, long keep)
 {
-	struct intel_gt_buffer_pool *pool =
-		container_of(wrk, typeof(*pool), work.work);
-	struct intel_gt_buffer_pool_node *node, *next;
-	unsigned long old = jiffies - HZ;
+	struct intel_gt_buffer_pool_node *node, *stale = NULL;
 	bool active = false;
-	LIST_HEAD(stale);
 	int n;
 
 	/* Free buffers that have not been used in the past second */
-	spin_lock_irq(&pool->lock);
 	for (n = 0; n < ARRAY_SIZE(pool->cache_list); n++) {
 		struct list_head *list = &pool->cache_list[n];
 
-		/* Most recent at head; oldest at tail */
-		list_for_each_entry_safe_reverse(node, next, list, link) {
-			if (time_before(node->age, old))
-				break;
+		if (list_empty(list))
+			continue;
+
+		if (spin_trylock_irq(&pool->lock)) {
+			struct list_head *pos;
+
+			/* Most recent at head; oldest at tail */
+			list_for_each_prev(pos, list) {
+				unsigned long age;
+
+				node = list_entry(pos, typeof(*node), link);
+
+				age = READ_ONCE(node->age);
+				if (!age || jiffies - age < keep)
+					break;
+
+				/* Check we are the first to claim this node */
+				if (!xchg(&node->age, 0))
+					break;
 
-			list_move(&node->link, &stale);
+				node->free = stale;
+				stale = node;
+			}
+			if (!list_is_last(pos, list))
+				__list_del_many(pos, list);
+
+			spin_unlock_irq(&pool->lock);
 		}
+
 		active |= !list_empty(list);
 	}
-	spin_unlock_irq(&pool->lock);
 
-	list_for_each_entry_safe(node, next, &stale, link)
+	while ((node = stale)) {
+		stale = stale->free;
 		node_free(node);
+	}
+
+	return active;
+}
+
+static void pool_free_work(struct work_struct *wrk)
+{
+	struct intel_gt_buffer_pool *pool =
+		container_of(wrk, typeof(*pool), work.work);
 
-	if (active)
+	if (pool_free_older_than(pool, HZ))
 		schedule_delayed_work(&pool->work,
 				      round_jiffies_up_relative(HZ));
 }
@@ -108,9 +134,10 @@ static void pool_retire(struct i915_active *ref)
 	/* Return this object to the shrinker pool */
 	i915_gem_object_make_purgeable(node->obj);
 
+	GEM_BUG_ON(node->age);
 	spin_lock_irqsave(&pool->lock, flags);
-	node->age = jiffies;
-	list_add(&node->link, list);
+	list_add_rcu(&node->link, list);
+	WRITE_ONCE(node->age, jiffies ?: 1); /* 0 reserved for active nodes */
 	spin_unlock_irqrestore(&pool->lock, flags);
 
 	schedule_delayed_work(&pool->work,
@@ -129,6 +156,7 @@ node_create(struct intel_gt_buffer_pool *pool, size_t sz)
 	if (!node)
 		return ERR_PTR(-ENOMEM);
 
+	node->age = 0;
 	node->pool = pool;
 	i915_active_init(&node->active, pool_active, pool_retire);
 
@@ -151,20 +179,30 @@ intel_gt_get_buffer_pool(struct intel_gt *gt, size_t size)
 	struct intel_gt_buffer_pool *pool = &gt->buffer_pool;
 	struct intel_gt_buffer_pool_node *node;
 	struct list_head *list;
-	unsigned long flags;
 	int ret;
 
 	size = PAGE_ALIGN(size);
 	list = bucket_for_size(pool, size);
 
-	spin_lock_irqsave(&pool->lock, flags);
-	list_for_each_entry(node, list, link) {
+	rcu_read_lock();
+	list_for_each_entry_rcu(node, list, link) {
+		unsigned long age;
+
 		if (node->obj->base.size < size)
 			continue;
-		list_del(&node->link);
-		break;
+
+		age = READ_ONCE(node->age);
+		if (!age)
+			continue;
+
+		if (cmpxchg(&node->age, age, 0) == age) {
+			spin_lock_irq(&pool->lock);
+			list_del_rcu(&node->link);
+			spin_unlock_irq(&pool->lock);
+			break;
+		}
 	}
-	spin_unlock_irqrestore(&pool->lock, flags);
+	rcu_read_unlock();
 
 	if (&node->link == list) {
 		node = node_create(pool, size);
@@ -192,28 +230,13 @@ void intel_gt_init_buffer_pool(struct intel_gt *gt)
 	INIT_DELAYED_WORK(&pool->work, pool_free_work);
 }
 
-static void pool_free_imm(struct intel_gt_buffer_pool *pool)
-{
-	int n;
-
-	spin_lock_irq(&pool->lock);
-	for (n = 0; n < ARRAY_SIZE(pool->cache_list); n++) {
-		struct intel_gt_buffer_pool_node *node, *next;
-		struct list_head *list = &pool->cache_list[n];
-
-		list_for_each_entry_safe(node, next, list, link)
-			node_free(node);
-		INIT_LIST_HEAD(list);
-	}
-	spin_unlock_irq(&pool->lock);
-}
-
 void intel_gt_flush_buffer_pool(struct intel_gt *gt)
 {
 	struct intel_gt_buffer_pool *pool = &gt->buffer_pool;
 
 	do {
-		pool_free_imm(pool);
+		while (pool_free_older_than(pool, 0))
+			;
 	} while (cancel_delayed_work_sync(&pool->work));
 }