I've checked both implementations (radeon/nouveau) and they both grab the page array from ttm simply by dereferencing it and then wrapping it up with drm_prime_pages_to_sg in the callback and map it with dma_map_sg (in the helper). Only the grabbing of the underlying page array is anything we need to be concerned about, and either those pages are pinned independently, or we're screwed no matter what. And indeed, nouveau/radeon pin the backing storage in their attach/detach functions. The only thing we might claim it does is prevent concurrent mapping of dma_buf attachments. But a) that's not allowed and b) the current code is racy already since it checks whether the sg mapping exists _before_ grabbing the lock. So the dev->struct_mutex locking here does absolutely nothing useful, but only distracts. Remove it. This should also help Maarten's work to eventually pin the backing storage more dynamically by preventing locking inversions around dev->struct_mutex. Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxx> Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxx> --- drivers/gpu/drm/drm_prime.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c index 85e450e..64a99b3 100644 --- a/drivers/gpu/drm/drm_prime.c +++ b/drivers/gpu/drm/drm_prime.c @@ -167,8 +167,6 @@ static struct sg_table *drm_gem_map_dma_buf(struct dma_buf_attachment *attach, if (WARN_ON(prime_attach->dir != DMA_NONE)) return ERR_PTR(-EBUSY); - mutex_lock(&obj->dev->struct_mutex); - sgt = obj->dev->driver->gem_prime_get_sg_table(obj); if (!IS_ERR(sgt)) { @@ -182,7 +180,6 @@ static struct sg_table *drm_gem_map_dma_buf(struct dma_buf_attachment *attach, } } - mutex_unlock(&obj->dev->struct_mutex); return sgt; } -- 1.8.3.2 _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel