linux-kernel - Re: [PATCH v2] drm/sched/tests: Use one lock for fence context

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Message-ID: <9783f727-faad-44bb-b47d-3ba06ef8b82d@igalia.com>
Date: Mon, 2 Jun 2025 08:58:30 +0100
From: Tvrtko Ursulin <tvrtko.ursulin@...lia.com>
To: Philipp Stanner <phasta@...nel.org>,
 Matthew Brost <matthew.brost@...el.com>, Danilo Krummrich <dakr@...nel.org>,
 Christian König <ckoenig.leichtzumerken@...il.com>,
 airlied@...il.com, Simona Vetter <simona@...ll.ch>
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] drm/sched/tests: Use one lock for fence context


On 27/05/2025 11:10, Philipp Stanner wrote:
> There is no need for separate locks for single jobs and the entire
> scheduler. The dma_fence context can be protected by the scheduler lock,
> allowing for removing the jobs' locks. This simplifies things and
> reduces the likelyhood of deadlocks etc.
> 
> Replace the jobs' locks with the mock scheduler lock.
> 
> Signed-off-by: Philipp Stanner <phasta@...nel.org>
> ---
> Changes in v2:
>    - Make commit message more neutral by stating it's about simplifying
>      the code. (Tvrtko)
> ---
>   drivers/gpu/drm/scheduler/tests/mock_scheduler.c | 5 ++---
>   drivers/gpu/drm/scheduler/tests/sched_tests.h    | 1 -
>   2 files changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/scheduler/tests/mock_scheduler.c b/drivers/gpu/drm/scheduler/tests/mock_scheduler.c
> index f999c8859cf7..17023276f4b0 100644
> --- a/drivers/gpu/drm/scheduler/tests/mock_scheduler.c
> +++ b/drivers/gpu/drm/scheduler/tests/mock_scheduler.c
> @@ -64,7 +64,7 @@ static void drm_mock_sched_job_complete(struct drm_mock_sched_job *job)
>   
>   	job->flags |= DRM_MOCK_SCHED_JOB_DONE;
>   	list_move_tail(&job->link, &sched->done_list);
> -	dma_fence_signal(&job->hw_fence);
> +	dma_fence_signal_locked(&job->hw_fence);
>   	complete(&job->done);
>   }
>   
> @@ -123,7 +123,6 @@ drm_mock_sched_job_new(struct kunit *test,
>   	job->test = test;
>   
>   	init_completion(&job->done);
> -	spin_lock_init(&job->lock);
>   	INIT_LIST_HEAD(&job->link);
>   	hrtimer_setup(&job->timer, drm_mock_sched_job_signal_timer,
>   		      CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
> @@ -169,7 +168,7 @@ static struct dma_fence *mock_sched_run_job(struct drm_sched_job *sched_job)
>   
>   	dma_fence_init(&job->hw_fence,
>   		       &drm_mock_sched_hw_fence_ops,
> -		       &job->lock,
> +		       &sched->lock,
>   		       sched->hw_timeline.context,
>   		       atomic_inc_return(&sched->hw_timeline.next_seqno));
>   
> diff --git a/drivers/gpu/drm/scheduler/tests/sched_tests.h b/drivers/gpu/drm/scheduler/tests/sched_tests.h
> index 27caf8285fb7..fbba38137f0c 100644
> --- a/drivers/gpu/drm/scheduler/tests/sched_tests.h
> +++ b/drivers/gpu/drm/scheduler/tests/sched_tests.h
> @@ -106,7 +106,6 @@ struct drm_mock_sched_job {
>   	unsigned int		duration_us;
>   	ktime_t			finish_at;
>   
> -	spinlock_t		lock;
>   	struct dma_fence	hw_fence;
>   
>   	struct kunit		*test;

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@...lia.com>

Regards,

Tvrtko