drm/nouveau: hold mutex while syncing to kernel channel

Not holding the mutex potentially causes corruption of the kernel
channel when page flipping.

Cc: stable@vger.kernel.org #3.13
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@canonical.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

1 files changed, 8 insertions, 7 deletions

diff --git a/drivers/gpu/drm/nouveau/nouveau_display.c b/drivers/gpu/drm/nouveau/nouveau_display.c
index 25ea82f8def3..8b757483a107 100644
--- a/drivers/gpu/drm/nouveau/nouveau_display.c
+++ b/drivers/gpu/drm/nouveau/nouveau_display.c
@@ -603,6 +603,14 @@ nouveau_crtc_page_flip(struct drm_crtc *crtc, struct drm_framebuffer *fb,
         if (!s)
                 return -ENOMEM;
 
+        if (new_bo != old_bo) {
+                ret = nouveau_bo_pin(new_bo, TTM_PL_FLAG_VRAM);
+                if (ret)
+                        goto fail_free;
+        }
+
+        mutex_lock(&chan->cli->mutex);
+
         /* synchronise rendering channel with the kernel's channel */
         spin_lock(&new_bo->bo.bdev->fence_lock);
         fence = nouveau_fence_ref(new_bo->bo.sync_obj);
@@ -612,13 +620,6 @@ nouveau_crtc_page_flip(struct drm_crtc *crtc, struct drm_framebuffer *fb,
         if (ret)
                 goto fail_free;
 
-        if (new_bo != old_bo) {
-                ret = nouveau_bo_pin(new_bo, TTM_PL_FLAG_VRAM);
-                if (ret)
-                        goto fail_free;
-        }
-
-        mutex_lock(&chan->cli->mutex);
         ret = ttm_bo_reserve(&old_bo->bo, true, false, false, NULL);
         if (ret)
                 goto fail_unpin;