From f8e0731db4a02c8c5624e1dce6dc983210a51f64 Mon Sep 17 00:00:00 2001 From: Christian König Date: Fri, 15 Sep 2017 11:53:07 +0200 Subject: dma-fence: fix dma_fence_get_rcu_safe v2 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit When dma_fence_get_rcu() fails to acquire a reference it doesn't necessary mean that there is no fence at all. It usually mean that the fence was replaced by a new one and in this situation we certainly want to have the new one as result and *NOT* NULL. v2: Keep extra check after dma_fence_get_rcu(). Signed-off-by: Christian König Cc: Chris Wilson Cc: Daniel Vetter Cc: Sumit Semwal Cc: linux-media@vger.kernel.org Cc: dri-devel@lists.freedesktop.org Cc: linaro-mm-sig@lists.linaro.org Reviewed-by: Maarten Lankhorst Signed-off-by: Alex Deucher Link: https://patchwork.freedesktop.org/patch/msgid/1505469187-3565-1-git-send-email-deathsimple@vodafone.de --- include/linux/dma-fence.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'include/linux') diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h index 171895072435..ca974224d92e 100644 --- a/include/linux/dma-fence.h +++ b/include/linux/dma-fence.h @@ -248,9 +248,12 @@ dma_fence_get_rcu_safe(struct dma_fence * __rcu *fencep) struct dma_fence *fence; fence = rcu_dereference(*fencep); - if (!fence || !dma_fence_get_rcu(fence)) + if (!fence) return NULL; + if (!dma_fence_get_rcu(fence)) + continue; + /* The atomic_inc_not_zero() inside dma_fence_get_rcu() * provides a full memory barrier upon success (such as now). * This is paired with the write barrier from assigning -- cgit