Am 04.06.19 um 14:39 schrieb Chris Wilson:
> If we have to drop the seqcount & rcu lock to perform a krealloc, we
> have to restart the loop. In doing so, be careful not to lose track of
> the already acquired exclusive fence.
>
> Fixes: fedf54132d24 ("dma-buf: Restart reservation_object_get_fences_rcu() after writes") #v4.10
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
> Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
> Cc: Christian König <christian.koenig@xxxxxxx>
> Cc: Alex Deucher <alexander.deucher@xxxxxxx>
> Cc: Sumit Semwal <sumit.semwal@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> ---
> drivers/dma-buf/reservation.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/drivers/dma-buf/reservation.c b/drivers/dma-buf/reservation.c
> index 4d32e2c67862..704503df4892 100644
> --- a/drivers/dma-buf/reservation.c
> +++ b/drivers/dma-buf/reservation.c
> @@ -365,6 +365,12 @@ int reservation_object_get_fences_rcu(struct reservation_object *obj,
> GFP_NOWAIT | __GFP_NOWARN);
> if (!nshared) {
> rcu_read_unlock();
> +
> + if (fence_excl) {
> + dma_fence_put(fence_excl);
> + fence_excl = NULL;
> + }
> +
dma_fence_put is NULL save, so no need for the if.
But apart from that a good catch,
Christian.
> nshared = krealloc(shared, sz, GFP_KERNEL);
> if (nshared) {
> shared = nshared;
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