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dma-fence: fix dma_fence_get_rcu_safe v2

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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 <christian.koenig@amd.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: linux-media@vger.kernel.org
Cc: dri-devel@lists.freedesktop.org
Cc: linaro-mm-sig@lists.linaro.org
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1505469187-3565-1-git-send-email-deathsimple@vodafone.de
This commit is contained in:
Christian König 2017-09-15 11:53:07 +02:00 committed by Alex Deucher
parent 39e16ba16c
commit f8e0731db4
1 changed files with 4 additions and 1 deletions
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5
include/linux/dma-fence.h
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@ -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