The patch below does not apply to the 6.6-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable@xxxxxxxxxxxxxxx>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y git checkout FETCH_HEAD git cherry-pick -x 0da611a8702101814257a7c03f6caf0574c83b98 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable@xxxxxxxxxxxxxxx>' --in-reply-to '2024012643-undecided-bride-578b@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^.. Possible dependencies: 0da611a87021 ("dma-buf: add dma_fence_timestamp helper") thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 0da611a8702101814257a7c03f6caf0574c83b98 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Christian=20K=C3=B6nig?= <christian.koenig@xxxxxxx> Date: Fri, 8 Sep 2023 10:27:23 +0200 Subject: [PATCH] dma-buf: add dma_fence_timestamp helper MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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: Yunxiang Li <Yunxiang.Li@xxxxxxx> Signed-off-by: Christian König <christian.koenig@xxxxxxx> Fixes: 1774baa64f93 ("drm/scheduler: Change scheduled fence track v2") Reviewed-by: Alex Deucher <alexander.deucher@xxxxxxx> CC: stable@xxxxxxxxxxxxxxx Link: https://patchwork.freedesktop.org/patch/msgid/20230929104725.2358-1-christian.koenig@xxxxxxx diff --git a/drivers/dma-buf/dma-fence-unwrap.c b/drivers/dma-buf/dma-fence-unwrap.c index c625bb2b5d56..628af51c81af 100644 --- a/drivers/dma-buf/dma-fence-unwrap.c +++ b/drivers/dma-buf/dma-fence-unwrap.c @@ -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; } } } diff --git a/drivers/dma-buf/sync_file.c b/drivers/dma-buf/sync_file.c index af57799c86ce..2e9a316c596a 100644 --- a/drivers/dma-buf/sync_file.c +++ b/drivers/dma-buf/sync_file.c @@ -268,13 +268,10 @@ 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) : - ktime_set(0, 0); + dma_fence_is_signaled(fence) ? + ktime_to_ns(dma_fence_timestamp(fence)) : + ktime_set(0, 0); return info->status; } diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c index fd755e953487..99797a8c836a 100644 --- a/drivers/gpu/drm/scheduler/sched_main.c +++ b/drivers/gpu/drm/scheduler/sched_main.c @@ -935,7 +935,7 @@ 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); } diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h index 0d678e9a7b24..ebe78bd3d121 100644 --- a/include/linux/dma-fence.h +++ b/include/linux/dma-fence.h @@ -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,
