[PATCH] drm/syncobj: ensure progress for syncobj queries

[Chia-I Wu]

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.
---
 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);
-- 
2.47.0.rc1.288.g06298d1525-goog