On Thu, 17 Oct 2024 09:20:53 -0700
Chia-I Wu <olvaffe@xxxxxxxxx> wrote:
> Userspace might poll a syncobj with the query ioctl. Call
> dma_fence_enable_sw_signaling to ensure dma_fence_is_signaled returns
> true in finite time.
>
> ---
>
> panvk hits this issue when timeline semaphore is enabled. It uses the
> transfer ioctl to propagate fences. dma_fence_unwrap_merge converts the
> dma_fence_chain to a dma_fence_array. dma_fence_array_signaled never
> return true unless signaling is enabled.
Looks like a bugfix to me. Should we add Fixes+Cc-stable tags so it
gets backported to stable branches.
> ---
> drivers/gpu/drm/drm_syncobj.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_syncobj.c b/drivers/gpu/drm/drm_syncobj.c
> index 4fcfc0b9b386c..58c5593c897a2 100644
> --- a/drivers/gpu/drm/drm_syncobj.c
> +++ b/drivers/gpu/drm/drm_syncobj.c
> @@ -1689,6 +1689,9 @@ int drm_syncobj_query_ioctl(struct drm_device *dev, void *data,
> DRM_SYNCOBJ_QUERY_FLAGS_LAST_SUBMITTED) {
> point = fence->seqno;
> } else {
> + /* ensure forward progress */
> + dma_fence_enable_sw_signaling(fence);
> +
> dma_fence_chain_for_each(iter, fence) {
> if (iter->context != fence->context) {
> dma_fence_put(iter);
