[PATCH] drm/sched: test before reading fence timestamp

[Yunxiang Li <Yunxiang.Li@xxxxxxx>]

Reading fence timestamp always need to check the corresponding flag bit
before to make sure the write is actually visible, otherwise we can read
garbage here.

Fixes: 1774baa64f93 ("drm/scheduler: Change scheduled fence track v2")
Signed-off-by: Yunxiang Li <Yunxiang.Li@xxxxxxx>
---
 drivers/gpu/drm/scheduler/sched_main.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
index 506371c42745..8ed00f54c59d 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -928,6 +928,9 @@ drm_sched_get_cleanup_job(struct drm_gpu_scheduler *sched)
 						typeof(*next), list);
 
 		if (next) {
+			while (!test_bit(DMA_FENCE_FLAG_TIMESTAMP_BIT,
+					 &job->s_fence->finished.flags))
+				cpu_relax();
 			next->s_fence->scheduled.timestamp =
 				job->s_fence->finished.timestamp;
 			/* start TO timer for next job */
-- 
2.34.1