diff options
| -rw-r--r-- | drivers/dma-buf/dma-resv.c | 16 | ||||
| -rw-r--r-- | include/linux/dma-buf.h | 4 | ||||
| -rw-r--r-- | include/linux/dma-resv.h | 22 |
3 files changed, 7 insertions, 35 deletions
diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c index 5001e9b4420a..be65522f0f47 100644 --- a/drivers/dma-buf/dma-resv.c +++ b/drivers/dma-buf/dma-resv.c @@ -351,35 +351,21 @@ EXPORT_SYMBOL(dma_resv_replace_fences); * @fence: the exclusive fence to add * * Add a fence to the exclusive slot. @obj must be locked with dma_resv_lock(). - * Note that this function replaces all fences attached to @obj, see also - * &dma_resv.fence_excl for a discussion of the semantics. + * See also &dma_resv.fence_excl for a discussion of the semantics. */ void dma_resv_add_excl_fence(struct dma_resv *obj, struct dma_fence *fence) { struct dma_fence *old_fence = dma_resv_excl_fence(obj); - struct dma_resv_list *old; - u32 i = 0; dma_resv_assert_held(obj); - old = dma_resv_shared_list(obj); - if (old) - i = old->shared_count; - dma_fence_get(fence); write_seqcount_begin(&obj->seq); /* write_seqcount_begin provides the necessary memory barrier */ RCU_INIT_POINTER(obj->fence_excl, fence); - if (old) - old->shared_count = 0; write_seqcount_end(&obj->seq); - /* inplace update, no shared fences */ - while (i--) - dma_fence_put(rcu_dereference_protected(old->shared[i], - dma_resv_held(obj))); - dma_fence_put(old_fence); } EXPORT_SYMBOL(dma_resv_add_excl_fence); diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index 7ab50076e7a6..85ab5554425e 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -424,9 +424,7 @@ struct dma_buf { * IMPORTANT: * * All drivers must obey the struct dma_resv rules, specifically the - * rules for updating fences, see &dma_resv.fence_excl and - * &dma_resv.fence. If these dependency rules are broken access tracking - * can be lost resulting in use after free issues. + * rules for updating and obeying fences. */ struct dma_resv *resv; diff --git a/include/linux/dma-resv.h b/include/linux/dma-resv.h index 202cc65d0621..dccaf7b1663e 100644 --- a/include/linux/dma-resv.h +++ b/include/linux/dma-resv.h @@ -93,23 +93,11 @@ struct dma_resv { * * The exclusive fence, if there is one currently. * - * There are two ways to update this fence: - * - * - First by calling dma_resv_add_excl_fence(), which replaces all - * fences attached to the reservation object. To guarantee that no - * fences are lost, this new fence must signal only after all previous - * fences, both shared and exclusive, have signalled. In some cases it - * is convenient to achieve that by attaching a struct dma_fence_array - * with all the new and old fences. - * - * - Alternatively the fence can be set directly, which leaves the - * shared fences unchanged. To guarantee that no fences are lost, this - * new fence must signal only after the previous exclusive fence has - * signalled. Since the shared fences are staying intact, it is not - * necessary to maintain any ordering against those. If semantically - * only a new access is added without actually treating the previous - * one as a dependency the exclusive fences can be strung together - * using struct dma_fence_chain. + * To guarantee that no fences are lost, this new fence must signal + * only after the previous exclusive fence has signalled. If + * semantically only a new access is added without actually treating the + * previous one as a dependency the exclusive fences can be strung + * together using struct dma_fence_chain. * * Note that actual semantics of what an exclusive or shared fence mean * is defined by the user, for reservation objects shared across drivers |