[PATCH 1/8] dma-buf: remove shared fence staging in reservation object
Christian König
ckoenig.leichtzumerken at gmail.com
Fri Oct 12 08:22:00 UTC 2018
Ping! Adding a few people directly and more mailing lists.
Can I get an acked-by/rb for this? It's only a cleanup and not much
functional change.
Regards,
Christian.
Am 04.10.2018 um 15:12 schrieb Christian König:
> No need for that any more. Just replace the list when there isn't enough
> room any more for the additional fence.
>
> Signed-off-by: Christian König <christian.koenig at amd.com>
> ---
> drivers/dma-buf/reservation.c | 178 ++++++++++++++----------------------------
> include/linux/reservation.h | 4 -
> 2 files changed, 58 insertions(+), 124 deletions(-)
>
> diff --git a/drivers/dma-buf/reservation.c b/drivers/dma-buf/reservation.c
> index 6c95f61a32e7..5825fc336a13 100644
> --- a/drivers/dma-buf/reservation.c
> +++ b/drivers/dma-buf/reservation.c
> @@ -68,105 +68,23 @@ EXPORT_SYMBOL(reservation_seqcount_string);
> */
> int reservation_object_reserve_shared(struct reservation_object *obj)
> {
> - struct reservation_object_list *fobj, *old;
> - u32 max;
> + struct reservation_object_list *old, *new;
> + unsigned int i, j, k, max;
>
> old = reservation_object_get_list(obj);
>
> if (old && old->shared_max) {
> - if (old->shared_count < old->shared_max) {
> - /* perform an in-place update */
> - kfree(obj->staged);
> - obj->staged = NULL;
> + if (old->shared_count < old->shared_max)
> return 0;
> - } else
> + else
> max = old->shared_max * 2;
> - } else
> - max = 4;
> -
> - /*
> - * resize obj->staged or allocate if it doesn't exist,
> - * noop if already correct size
> - */
> - fobj = krealloc(obj->staged, offsetof(typeof(*fobj), shared[max]),
> - GFP_KERNEL);
> - if (!fobj)
> - return -ENOMEM;
> -
> - obj->staged = fobj;
> - fobj->shared_max = max;
> - return 0;
> -}
> -EXPORT_SYMBOL(reservation_object_reserve_shared);
> -
> -static void
> -reservation_object_add_shared_inplace(struct reservation_object *obj,
> - struct reservation_object_list *fobj,
> - struct dma_fence *fence)
> -{
> - struct dma_fence *signaled = NULL;
> - u32 i, signaled_idx;
> -
> - dma_fence_get(fence);
> -
> - preempt_disable();
> - write_seqcount_begin(&obj->seq);
> -
> - for (i = 0; i < fobj->shared_count; ++i) {
> - struct dma_fence *old_fence;
> -
> - old_fence = rcu_dereference_protected(fobj->shared[i],
> - reservation_object_held(obj));
> -
> - if (old_fence->context == fence->context) {
> - /* memory barrier is added by write_seqcount_begin */
> - RCU_INIT_POINTER(fobj->shared[i], fence);
> - write_seqcount_end(&obj->seq);
> - preempt_enable();
> -
> - dma_fence_put(old_fence);
> - return;
> - }
> -
> - if (!signaled && dma_fence_is_signaled(old_fence)) {
> - signaled = old_fence;
> - signaled_idx = i;
> - }
> - }
> -
> - /*
> - * memory barrier is added by write_seqcount_begin,
> - * fobj->shared_count is protected by this lock too
> - */
> - if (signaled) {
> - RCU_INIT_POINTER(fobj->shared[signaled_idx], fence);
> } else {
> - BUG_ON(fobj->shared_count >= fobj->shared_max);
> - RCU_INIT_POINTER(fobj->shared[fobj->shared_count], fence);
> - fobj->shared_count++;
> + max = 4;
> }
>
> - write_seqcount_end(&obj->seq);
> - preempt_enable();
> -
> - dma_fence_put(signaled);
> -}
> -
> -static void
> -reservation_object_add_shared_replace(struct reservation_object *obj,
> - struct reservation_object_list *old,
> - struct reservation_object_list *fobj,
> - struct dma_fence *fence)
> -{
> - unsigned i, j, k;
> -
> - dma_fence_get(fence);
> -
> - if (!old) {
> - RCU_INIT_POINTER(fobj->shared[0], fence);
> - fobj->shared_count = 1;
> - goto done;
> - }
> + new = kmalloc(offsetof(typeof(*new), shared[max]), GFP_KERNEL);
> + if (!new)
> + return -ENOMEM;
>
> /*
> * no need to bump fence refcounts, rcu_read access
> @@ -174,46 +92,45 @@ reservation_object_add_shared_replace(struct reservation_object *obj,
> * references from the old struct are carried over to
> * the new.
> */
> - for (i = 0, j = 0, k = fobj->shared_max; i < old->shared_count; ++i) {
> - struct dma_fence *check;
> + for (i = 0, j = 0, k = max; i < (old ? old->shared_count : 0); ++i) {
> + struct dma_fence *fence;
>
> - 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);
> + fence = rcu_dereference_protected(old->shared[i],
> + reservation_object_held(obj));
> + if (dma_fence_is_signaled(fence))
> + RCU_INIT_POINTER(new->shared[--k], fence);
> else
> - RCU_INIT_POINTER(fobj->shared[j++], check);
> + RCU_INIT_POINTER(new->shared[j++], fence);
> }
> - fobj->shared_count = j;
> - RCU_INIT_POINTER(fobj->shared[fobj->shared_count], fence);
> - fobj->shared_count++;
> + new->shared_count = j;
> + new->shared_max = max;
>
> -done:
> preempt_disable();
> write_seqcount_begin(&obj->seq);
> /*
> * RCU_INIT_POINTER can be used here,
> * seqcount provides the necessary barriers
> */
> - RCU_INIT_POINTER(obj->fence, fobj);
> + RCU_INIT_POINTER(obj->fence, new);
> write_seqcount_end(&obj->seq);
> preempt_enable();
>
> if (!old)
> - return;
> + return 0;
>
> /* Drop the references to the signaled fences */
> - for (i = k; i < fobj->shared_max; ++i) {
> - struct dma_fence *f;
> + for (i = k; i < new->shared_max; ++i) {
> + struct dma_fence *fence;
>
> - f = rcu_dereference_protected(fobj->shared[i],
> - reservation_object_held(obj));
> - dma_fence_put(f);
> + fence = rcu_dereference_protected(new->shared[i],
> + reservation_object_held(obj));
> + dma_fence_put(fence);
> }
> kfree_rcu(old, rcu);
> +
> + return 0;
> }
> +EXPORT_SYMBOL(reservation_object_reserve_shared);
>
> /**
> * reservation_object_add_shared_fence - Add a fence to a shared slot
> @@ -226,15 +143,39 @@ reservation_object_add_shared_replace(struct reservation_object *obj,
> void reservation_object_add_shared_fence(struct reservation_object *obj,
> struct dma_fence *fence)
> {
> - struct reservation_object_list *old, *fobj = obj->staged;
> + struct reservation_object_list *fobj;
> + unsigned int i;
>
> - old = reservation_object_get_list(obj);
> - obj->staged = NULL;
> + dma_fence_get(fence);
> +
> + fobj = reservation_object_get_list(obj);
>
> - if (!fobj)
> - reservation_object_add_shared_inplace(obj, old, fence);
> - else
> - reservation_object_add_shared_replace(obj, old, fobj, fence);
> + preempt_disable();
> + write_seqcount_begin(&obj->seq);
> +
> + for (i = 0; i < fobj->shared_count; ++i) {
> + struct dma_fence *old_fence;
> +
> + old_fence = rcu_dereference_protected(fobj->shared[i],
> + reservation_object_held(obj));
> + if (old_fence->context == fence->context ||
> + dma_fence_is_signaled(old_fence)) {
> + dma_fence_put(old_fence);
> + goto replace;
> + }
> + }
> +
> + BUG_ON(fobj->shared_count >= fobj->shared_max);
> + fobj->shared_count++;
> +
> +replace:
> + /*
> + * memory barrier is added by write_seqcount_begin,
> + * fobj->shared_count is protected by this lock too
> + */
> + RCU_INIT_POINTER(fobj->shared[i], fence);
> + write_seqcount_end(&obj->seq);
> + preempt_enable();
> }
> EXPORT_SYMBOL(reservation_object_add_shared_fence);
>
> @@ -343,9 +284,6 @@ int reservation_object_copy_fences(struct reservation_object *dst,
> new = dma_fence_get_rcu_safe(&src->fence_excl);
> rcu_read_unlock();
>
> - kfree(dst->staged);
> - dst->staged = NULL;
> -
> src_list = reservation_object_get_list(dst);
> old = reservation_object_get_excl(dst);
>
> diff --git a/include/linux/reservation.h b/include/linux/reservation.h
> index 02166e815afb..54cf6773a14c 100644
> --- a/include/linux/reservation.h
> +++ b/include/linux/reservation.h
> @@ -68,7 +68,6 @@ struct reservation_object_list {
> * @seq: sequence count for managing RCU read-side synchronization
> * @fence_excl: the exclusive fence, if there is one currently
> * @fence: list of current shared fences
> - * @staged: staged copy of shared fences for RCU updates
> */
> struct reservation_object {
> struct ww_mutex lock;
> @@ -76,7 +75,6 @@ struct reservation_object {
>
> struct dma_fence __rcu *fence_excl;
> struct reservation_object_list __rcu *fence;
> - struct reservation_object_list *staged;
> };
>
> #define reservation_object_held(obj) lockdep_is_held(&(obj)->lock.base)
> @@ -95,7 +93,6 @@ reservation_object_init(struct reservation_object *obj)
> __seqcount_init(&obj->seq, reservation_seqcount_string, &reservation_seqcount_class);
> RCU_INIT_POINTER(obj->fence, NULL);
> RCU_INIT_POINTER(obj->fence_excl, NULL);
> - obj->staged = NULL;
> }
>
> /**
> @@ -124,7 +121,6 @@ reservation_object_fini(struct reservation_object *obj)
>
> kfree(fobj);
> }
> - kfree(obj->staged);
>
> ww_mutex_destroy(&obj->lock);
> }
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