Re: [Intel-gfx] [PATCH 06/26] dma-buf: use new iterator in dma_resv_test_signaled

Daniel Vetter
2021-09-17T14:45:40Z

On Fri, Sep 17, 2021 at 02:34:53PM +0200, Christian König wrote:
> This makes the function much simpler since the complex
> retry logic is now handled elsewhere.
>
> Signed-off-by: Christian König <christian.koenig@amd.com>
> ---
> drivers/dma-buf/dma-resv.c | 56 ++++++--------------------------------
> 1 file changed, 9 insertions(+), 47 deletions(-)
>
> diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c
> index c7db553ab115..d8f428ddaedd 100644
> --- a/drivers/dma-buf/dma-resv.c
> +++ b/drivers/dma-buf/dma-resv.c
> @@ -593,22 +593,6 @@ long dma_resv_wait_timeout(struct dma_resv *obj, bool wait_all, bool intr,
> EXPORT_SYMBOL_GPL(dma_resv_wait_timeout);
>
>
> -static inline int dma_resv_test_signaled_single(struct dma_fence *passed_fence)
> -{
> - struct dma_fence *fence, *lfence = passed_fence;
> - int ret = 1;
> -
> - if (!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &lfence->flags)) {
> - fence = dma_fence_get_rcu(lfence);
> - if (!fence)
> - return -1;
> -
> - ret = !!dma_fence_is_signaled(fence);
> - dma_fence_put(fence);
> - }
> - return ret;
> -}
> -
> /**
> * dma_resv_test_signaled - Test if a reservation object's fences have been
> * signaled.
> @@ -625,43 +609,21 @@ static inline int dma_resv_test_signaled_single(struct dma_fence *passed_fence)
> */
> bool dma_resv_test_signaled(struct dma_resv *obj, bool test_all)
> {
> + struct dma_resv_iter cursor;
> struct dma_fence *fence;
> - unsigned int seq;
> - int ret;
>
> rcu_read_lock();
> -retry:
> - ret = true;
> - seq = read_seqcount_begin(&obj->seq);
> -
> - if (test_all) {
> - struct dma_resv_list *fobj = dma_resv_shared_list(obj);
> - unsigned int i, shared_count;
> -
> - shared_count = fobj ? fobj->shared_count : 0;
> - for (i = 0; i < shared_count; ++i) {
> - fence = rcu_dereference(fobj->shared[i]);
> - ret = dma_resv_test_signaled_single(fence);
> - if (ret < 0)
> - goto retry;
> - else if (!ret)
> - break;
> + dma_resv_iter_begin(&cursor, obj, test_all);
> + dma_resv_for_each_fence_unlocked(&cursor, fence) {
> + if (!dma_fence_is_signaled(fence)) {

Should we be extremely clever and document that the iterator already
filters out unsignalled fences? We could rely on that here :-) Otoh we
don't want to make the full is_signalled check in that iterator, so this
makes sense.

Again rcu_read_lock into the iterators pls. With that:

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

> + dma_resv_iter_end(&cursor);
> + rcu_read_unlock();
> + return false;
> }
> }
> -
> - fence = dma_resv_excl_fence(obj);
> - if (ret && fence) {
> - ret = dma_resv_test_signaled_single(fence);
> - if (ret < 0)
> - goto retry;
> -
> - }
> -
> - if (read_seqcount_retry(&obj->seq, seq))
> - goto retry;
> -
> + dma_resv_iter_end(&cursor);
> rcu_read_unlock();
> - return ret;
> + return true;
> }
> EXPORT_SYMBOL_GPL(dma_resv_test_signaled);
>
> --
> 2.25.1
>

--
Daniel Vetter
Software Engineer, Intel Corporation