[PATCH] drm: fix deadlock of syncobj v2

[Chunming Zhou <david1.zhou@xxxxxxx>]

v2:
add a mutex between sync_cb execution and free.

Signed-off-by: Chunming Zhou <david1.zhou@xxxxxxx>
Cc: Daniel Vetter <daniel@xxxxxxxx>
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Christian König <christian.koenig@xxxxxxx>
---
 drivers/gpu/drm/drm_syncobj.c | 11 +++++++++--
 include/drm/drm_syncobj.h     |  4 ++++
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_syncobj.c b/drivers/gpu/drm/drm_syncobj.c
index 57bf6006394d..c025a0b93565 100644
--- a/drivers/gpu/drm/drm_syncobj.c
+++ b/drivers/gpu/drm/drm_syncobj.c
@@ -158,9 +158,11 @@ void drm_syncobj_add_callback(struct drm_syncobj *syncobj,
 void drm_syncobj_remove_callback(struct drm_syncobj *syncobj,
 				 struct drm_syncobj_cb *cb)
 {
+	mutex_lock(&syncobj->mutex);
 	spin_lock(&syncobj->lock);
 	list_del_init(&cb->node);
 	spin_unlock(&syncobj->lock);
+	mutex_unlock(&syncobj->mutex);
 }
 
 static void drm_syncobj_init(struct drm_syncobj *syncobj)
@@ -344,13 +346,17 @@ void drm_syncobj_replace_fence(struct drm_syncobj *syncobj,
 	drm_syncobj_create_signal_pt(syncobj, fence, pt_value);
 	if (fence) {
 		struct drm_syncobj_cb *cur, *tmp;
+		LIST_HEAD(cb_list);
 
+		mutex_lock(&syncobj->mutex);
 		spin_lock(&syncobj->lock);
-		list_for_each_entry_safe(cur, tmp, &syncobj->cb_list, node) {
+		list_splice_init(&syncobj->cb_list, &cb_list);
+		spin_unlock(&syncobj->lock);
+		list_for_each_entry_safe(cur, tmp, &cb_list, node) {
 			list_del_init(&cur->node);
 			cur->func(syncobj, cur);
 		}
-		spin_unlock(&syncobj->lock);
+		mutex_unlock(&syncobj->mutex);
 	}
 }
 EXPORT_SYMBOL(drm_syncobj_replace_fence);
@@ -501,6 +507,7 @@ int drm_syncobj_create(struct drm_syncobj **out_syncobj, uint32_t flags,
 	kref_init(&syncobj->refcount);
 	INIT_LIST_HEAD(&syncobj->cb_list);
 	spin_lock_init(&syncobj->lock);
+	mutex_init(&syncobj->mutex);
 	if (flags & DRM_SYNCOBJ_CREATE_TYPE_TIMELINE)
 		syncobj->type = DRM_SYNCOBJ_TYPE_TIMELINE;
 	else
diff --git a/include/drm/drm_syncobj.h b/include/drm/drm_syncobj.h
index 5e8c5c027e09..3d3c8c181bd2 100644
--- a/include/drm/drm_syncobj.h
+++ b/include/drm/drm_syncobj.h
@@ -78,6 +78,10 @@ struct drm_syncobj {
 	 * @lock: Protects syncobj list and write-locks &fence.
 	 */
 	spinlock_t lock;
+	/**
+	 * @mutex: mutex between syncobj cb execution and free.
+	 */
+	struct mutex mutex;
 	/**
 	 * @file: A file backing for this syncobj.
 	 */
-- 
2.17.1

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