Quoting Christian König (2017-10-30 14:59:03)
> From: Christian König <christian.koenig at amd.com>
>
> The amdgpu issue to also need signaled fences in the reservation objects
> should be fixed by now.
>
> Optimize the list by keeping only the not signaled yet fences around.
>
> v2: temporary put the signaled fences at the end of the new container
>
> Signed-off-by: Christian König <christian.koenig at amd.com>
> ---
> drivers/dma-buf/reservation.c | 36 ++++++++++++++++++++++++++----------
> 1 file changed, 26 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/dma-buf/reservation.c b/drivers/dma-buf/reservation.c
> index b44d9d7db347..6fc794576997 100644
> --- a/drivers/dma-buf/reservation.c
> +++ b/drivers/dma-buf/reservation.c
> @@ -145,8 +145,8 @@ reservation_object_add_shared_replace(struct reservation_object *obj,
> struct reservation_object_list *fobj,
> struct dma_fence *fence)
> {
> - unsigned i;
> struct dma_fence *old_fence = NULL;
> + unsigned i, j, k;
>
> dma_fence_get(fence);
>
> @@ -162,9 +162,7 @@ reservation_object_add_shared_replace(struct reservation_object *obj,
> * references from the old struct are carried over to
> * the new.
> */
> - fobj->shared_count = old->shared_count;
> -
> - for (i = 0; i < old->shared_count; ++i) {
> + for (i = 0, j = 0, k = fobj->shared_max; i < old->shared_count; ++i) {
> struct dma_fence *check;
>
> check = rcu_dereference_protected(old->shared[i],
> @@ -172,10 +170,18 @@ reservation_object_add_shared_replace(struct reservation_object *obj,
>
> if (!old_fence && check->context == fence->context) {
> old_fence = check;
> - RCU_INIT_POINTER(fobj->shared[i], fence);
> - } else
> - RCU_INIT_POINTER(fobj->shared[i], check);
> + RCU_INIT_POINTER(fobj->shared[j++], fence);
> + } else if (!dma_fence_is_signaled(check)) {
> + RCU_INIT_POINTER(fobj->shared[j++], check);
> + } else {
> + /*
> + * Temporary save the signaled fences at the end of the
> + * new container
> + */
> + RCU_INIT_POINTER(fobj->shared[--k], check);
> + }
> }
> + fobj->shared_count = j;
> if (!old_fence) {
> RCU_INIT_POINTER(fobj->shared[fobj->shared_count], fence);
> fobj->shared_count++;
> @@ -192,10 +198,20 @@ reservation_object_add_shared_replace(struct reservation_object *obj,
> write_seqcount_end(&obj->seq);
> preempt_enable();
>
> - if (old)
> - kfree_rcu(old, rcu);
> -
> dma_fence_put(old_fence);
We don't need to keep old_fence (local var) around any more in this
scheme. By construction, the new shared_list is large enough to hold all
the old_fences+1, so you can use a loop like
j = 0;
k = fobj->shared_max;
RCU_INIT_POINTER(fobj->shared[j++], fence);
for (i = 0; i < old->shared_count; ++i) {
struct dma_fence *check;
check = rcu_dereference_protected(old->shared[i],
reservation_object_held(obj));
if (check->context == fence->context ||
dma_fence_is_signaled(check))
RCU_INIT_POINTER(fobj->shared[--k], check);
else
RCU_INIT_POINTER(fobj->shared[j++], check);
}
fobj->shared_count = j;
> +
> + if (!old)
> + return;
> +
> + /* Drop the references to the signaled fences */
> + for (i = k; i < fobj->shared_max; ++i) {
> + struct dma_fence *f;
> +
> + f = rcu_dereference_protected(fobj->shared[i],
> + reservation_object_held(obj));
> + dma_fence_put(f);
> + }
> + kfree_rcu(old, rcu);
> }
Fwiw, this fixes a big problem with the lack of pruning of the
reservation_object, so \o/
-Chris
