Commit b83ce9cb authored by Christian König's avatar Christian König
Browse files

dma-buf: add dma_fence_timestamp helper 



When a fence signals there is a very small race window where the timestamp
isn't updated yet. sync_file solves this by busy waiting for the
timestamp to appear, but on other ocassions didn't handled this
correctly.

Provide a dma_fence_timestamp() helper function for this and use it in
all appropriate cases.

Another alternative would be to grab the spinlock when that happens.

v2 by teddy: add a wait parameter to wait for the timestamp to show up, in case
   the accurate timestamp is needed and/or the timestamp is not based on
   ktime (e.g. hw timestamp)
v3 chk: drop the parameter again for unified handling

Signed-off-by: default avatarYunxiang Li <Yunxiang.Li@amd.com>
Signed-off-by: default avatarChristian König <christian.koenig@amd.com>
Fixes: 1774baa6 ("drm/scheduler: Change scheduled fence track v2")
Reviewed-by: default avatarAlex Deucher <alexander.deucher@amd.com>
CC: stable@vger.kernel.org
Link: https://patchwork.freedesktop.org/patch/msgid/20230929104725.2358-1-christian.koenig@amd.com
parent d59e75ee

drivers/dma-buf/dma-fence-unwrap.c

+4 −9
Original line number Diff line number Diff line
@@ -76,16 +76,11 @@ struct dma_fence *__dma_fence_unwrap_merge(unsigned int num_fences, 
		dma_fence_unwrap_for_each(tmp, &iter[i], fences[i]) {

			if (!dma_fence_is_signaled(tmp)) {

				++count;

			} else if (test_bit(DMA_FENCE_FLAG_TIMESTAMP_BIT,

					    &tmp->flags)) {

				if (ktime_after(tmp->timestamp, timestamp))

					timestamp = tmp->timestamp;

			} else {

				/*

				 * Use the current time if the fence is

				 * currently signaling.

				 */

				timestamp = ktime_get();

				ktime_t t = dma_fence_timestamp(tmp);



				if (ktime_after(t, timestamp))

					timestamp = t;

			}

		}

	}

drivers/dma-buf/sync_file.c

+3 −6
Original line number Diff line number Diff line
@@ -268,12 +268,9 @@ static int sync_fill_fence_info(struct dma_fence *fence, 
		sizeof(info->driver_name));



	info->status = dma_fence_get_status(fence);

	while (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags) &&

	       !test_bit(DMA_FENCE_FLAG_TIMESTAMP_BIT, &fence->flags))

		cpu_relax();

	info->timestamp_ns =

		test_bit(DMA_FENCE_FLAG_TIMESTAMP_BIT, &fence->flags) ?

		ktime_to_ns(fence->timestamp) :

		dma_fence_is_signaled(fence) ?

			ktime_to_ns(dma_fence_timestamp(fence)) :

			ktime_set(0, 0);



	return info->status;

drivers/gpu/drm/scheduler/sched_main.c

+1 −1
Original line number Diff line number Diff line
@@ -929,7 +929,7 @@ drm_sched_get_cleanup_job(struct drm_gpu_scheduler *sched) 


		if (next) {

			next->s_fence->scheduled.timestamp =

				job->s_fence->finished.timestamp;

				dma_fence_timestamp(&job->s_fence->finished);

			/* start TO timer for next job */

			drm_sched_start_timeout(sched);

		}

include/linux/dma-fence.h

+19 −0
Original line number Diff line number Diff line
@@ -568,6 +568,25 @@ static inline void dma_fence_set_error(struct dma_fence *fence, 
	fence->error = error;

}



/**

 * dma_fence_timestamp - helper to get the completion timestamp of a fence

 * @fence: fence to get the timestamp from.

 *

 * After a fence is signaled the timestamp is updated with the signaling time,

 * but setting the timestamp can race with tasks waiting for the signaling. This

 * helper busy waits for the correct timestamp to appear.

 */

static inline ktime_t dma_fence_timestamp(struct dma_fence *fence)

{

	if (WARN_ON(!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)))

		return ktime_get();



	while (!test_bit(DMA_FENCE_FLAG_TIMESTAMP_BIT, &fence->flags))

		cpu_relax();



	return fence->timestamp;

}



signed long dma_fence_wait_timeout(struct dma_fence *,

				   bool intr, signed long timeout);

signed long dma_fence_wait_any_timeout(struct dma_fence **fences,