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authorChris Wilson <chris@chris-wilson.co.uk>2016-08-29 10:08:31 +0300
committerSumit Semwal <sumit.semwal@linaro.org>2016-10-12 17:27:14 +0300
commit1cec20f0ea0e3bc617aed47e0936f17386c131f9 (patch)
treed70211f8dd4f56e064775ff746b46447fff3cbb7 /drivers/dma-buf
parentfedf54132d2410c3949036e3f611ab8dd9dbe89e (diff)
downloadlinux-1cec20f0ea0e3bc617aed47e0936f17386c131f9.tar.xz
dma-buf: Restart reservation_object_wait_timeout_rcu() after writes
In order to be completely generic, we have to double check the read seqlock after acquiring a reference to the fence. If the driver is allocating fences from a SLAB_DESTROY_BY_RCU, or similar freelist, then within an RCU grace period a fence may be freed and reallocated. The RCU read side critical section does not prevent this reallocation, instead we have to inspect the reservation's seqlock to double check if the fences have been reassigned as we were acquiring our reference. Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Christian König <christian.koenig@amd.com> Cc: Alex Deucher <alexander.deucher@amd.com> 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: Daniel Vetter <daniel.vetter@ffwll.ch> Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org> Link: http://patchwork.freedesktop.org/patch/msgid/20160829070834.22296-8-chris@chris-wilson.co.uk
Diffstat (limited to 'drivers/dma-buf')
-rw-r--r--drivers/dma-buf/reservation.c11
1 files changed, 5 insertions, 6 deletions
diff --git a/drivers/dma-buf/reservation.c b/drivers/dma-buf/reservation.c
index ba3e25dab95b..648e5d0325f9 100644
--- a/drivers/dma-buf/reservation.c
+++ b/drivers/dma-buf/reservation.c
@@ -388,9 +388,6 @@ retry:
if (fobj)
shared_count = fobj->shared_count;
- if (read_seqcount_retry(&obj->seq, seq))
- goto unlock_retry;
-
for (i = 0; i < shared_count; ++i) {
struct fence *lfence = rcu_dereference(fobj->shared[i]);
@@ -413,9 +410,6 @@ retry:
if (!shared_count) {
struct fence *fence_excl = rcu_dereference(obj->fence_excl);
- if (read_seqcount_retry(&obj->seq, seq))
- goto unlock_retry;
-
if (fence_excl &&
!test_bit(FENCE_FLAG_SIGNALED_BIT, &fence_excl->flags)) {
if (!fence_get_rcu(fence_excl))
@@ -430,6 +424,11 @@ retry:
rcu_read_unlock();
if (fence) {
+ if (read_seqcount_retry(&obj->seq, seq)) {
+ fence_put(fence);
+ goto retry;
+ }
+
ret = fence_wait_timeout(fence, intr, ret);
fence_put(fence);
if (ret > 0 && wait_all && (i + 1 < shared_count))