drm/radeon/kms: fix bo's fence association

Previous code did associate fence to bo before the fence was emited
and it also didn't lock protected access to ttm sync_obj member.
Both of this flaw leads to possible race between different code
path. This patch fix this by associating fence only once the fence
is emitted and properly lock protect access to sync_obj member of
ttm.

Fix:
https://bugs.freedesktop.org/show_bug.cgi?id=26438
and likely similar others bugs
Signed-off-by: Jerome Glisse <jglisse@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 15 insertions, 21 deletions

diff --git a/drivers/gpu/drm/radeon/radeon_object.c b/drivers/gpu/drm/radeon/radeon_object.c
index d72a71bff218..f1da370928eb 100644
--- a/drivers/gpu/drm/radeon/radeon_object.c
+++ b/drivers/gpu/drm/radeon/radeon_object.c
@@ -306,11 +306,10 @@ void radeon_bo_list_unreserve(struct list_head *head)
         }
 }
 
-int radeon_bo_list_validate(struct list_head *head, void *fence)
+int radeon_bo_list_validate(struct list_head *head)
 {
         struct radeon_bo_list *lobj;
         struct radeon_bo *bo;
-        struct radeon_fence *old_fence = NULL;
         int r;
 
         r = radeon_bo_list_reserve(head);
@@ -334,32 +333,27 @@ int radeon_bo_list_validate(struct list_head *head, void *fence)
                 }
                 lobj->gpu_offset = radeon_bo_gpu_offset(bo);
                 lobj->tiling_flags = bo->tiling_flags;
-                if (fence) {
-                        old_fence = (struct radeon_fence *)bo->tbo.sync_obj;
-                        bo->tbo.sync_obj = radeon_fence_ref(fence);
-                        bo->tbo.sync_obj_arg = NULL;
-                }
-                if (old_fence) {
-                        radeon_fence_unref(&old_fence);
-                }
         }
         return 0;
 }
 
-void radeon_bo_list_unvalidate(struct list_head *head, void *fence)
+void radeon_bo_list_fence(struct list_head *head, void *fence)
 {
         struct radeon_bo_list *lobj;
-        struct radeon_fence *old_fence;
-
-        if (fence)
-                list_for_each_entry(lobj, head, list) {
-                        old_fence = to_radeon_fence(lobj->bo->tbo.sync_obj);
-                        if (old_fence == fence) {
-                                lobj->bo->tbo.sync_obj = NULL;
-                                radeon_fence_unref(&old_fence);
-                        }
+        struct radeon_bo *bo;
+        struct radeon_fence *old_fence = NULL;
+
+        list_for_each_entry(lobj, head, list) {
+                bo = lobj->bo;
+                spin_lock(&bo->tbo.lock);
+                old_fence = (struct radeon_fence *)bo->tbo.sync_obj;
+                bo->tbo.sync_obj = radeon_fence_ref(fence);
+                bo->tbo.sync_obj_arg = NULL;
+                spin_unlock(&bo->tbo.lock);
+                if (old_fence) {
+                        radeon_fence_unref(&old_fence);
                 }
-        radeon_bo_list_unreserve(head);
+        }
 }
 
 int radeon_bo_fbdev_mmap(struct radeon_bo *bo,