[PATCH libdrm 2/2] drm:fix race issue between two bo functions(v2)

[Monk Liu]

From: Monk Liu <monk.liu at amd.com>

there is race issue between two threads on amdgpu_bo_reference and
amdgpu_bo_import, this patch tends to fix it by moving the
pthread_mutex_lock out of bo_free_internal and move to bo_reference
to cover the update_reference part.

The mutex_unlock in bo_import should also cover bo refcount
increasement.

Change-Id: I1f65eacf74cd28cc0d3a71ef2f7a19b890d63c29
Signed-off-by: Monk Liu <monk.liu at amd.com>
---
 amdgpu/amdgpu_bo.c       |  5 +----
 amdgpu/amdgpu_internal.h | 15 ++++++++++++---
 2 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/amdgpu/amdgpu_bo.c b/amdgpu/amdgpu_bo.c
index 07eb743..82f38c0 100644
--- a/amdgpu/amdgpu_bo.c
+++ b/amdgpu/amdgpu_bo.c
@@ -55,14 +55,12 @@ static void amdgpu_close_kms_handle(amdgpu_device_handle dev,
 void amdgpu_bo_free_internal(amdgpu_bo_handle bo)
 {
 	/* Remove the buffer from the hash tables. */
-	pthread_mutex_lock(&bo->dev->bo_table_mutex);
 	util_hash_table_remove(bo->dev->bo_handles,
 			       (void*)(uintptr_t)bo->handle);
 	if (bo->flink_name) {
 		util_hash_table_remove(bo->dev->bo_flink_names,
 				       (void*)(uintptr_t)bo->flink_name);
 	}
-	pthread_mutex_unlock(&bo->dev->bo_table_mutex);
 
 	/* Release CPU access. */
 	if (bo->cpu_map_count > 0) {
@@ -340,10 +338,9 @@ int amdgpu_bo_import(amdgpu_device_handle dev,
 	}
 
 	if (bo) {
-		pthread_mutex_unlock(&dev->bo_table_mutex);
-
 		/* The buffer already exists, just bump the refcount. */
 		atomic_inc(&bo->refcount);
+		pthread_mutex_unlock(&dev->bo_table_mutex);
 
 		output->buf_handle = bo;
 		output->alloc_size = bo->alloc_size;
diff --git a/amdgpu/amdgpu_internal.h b/amdgpu/amdgpu_internal.h
index 0508131..79da0e7 100644
--- a/amdgpu/amdgpu_internal.h
+++ b/amdgpu/amdgpu_internal.h
@@ -143,7 +143,7 @@ void amdgpu_vamgr_deinit(struct amdgpu_bo_va_mgr *mgr);
 uint64_t amdgpu_vamgr_find_va(struct amdgpu_bo_va_mgr *mgr, uint64_t size,
 				uint64_t alignment, uint64_t base_required);
 
-void amdgpu_vamgr_free_va(struct amdgpu_bo_va_mgr *mgr, uint64_t va, 
+void amdgpu_vamgr_free_va(struct amdgpu_bo_va_mgr *mgr, uint64_t va,
 				uint64_t size);
 
 int amdgpu_query_gpu_info_init(amdgpu_device_handle dev);
@@ -193,8 +193,17 @@ static inline bool update_references(atomic_t *dst, atomic_t *src)
 static inline void amdgpu_bo_reference(struct amdgpu_bo **dst,
 					struct amdgpu_bo *src)
 {
-	if (update_references(&(*dst)->refcount, &src->refcount))
-		amdgpu_bo_free_internal(*dst);
+	pthread_mutex_t *mlock;
+	struct amdgpu_bo* bo = *dst;
+
+	assert(bo != NULL);
+	mlock = &bo->dev->bo_table_mutex;
+	pthread_mutex_lock(mlock);
+
+	if (update_references(&bo->refcount, src?&src->refcount:NULL))
+		amdgpu_bo_free_internal(bo);
+
+	pthread_mutex_unlock(mlock);
 	*dst = src;
 }
 
-- 
2.7.4