linux-kernel - Re: [PATCH 2/3] drm/sched: Adjust outdated docu for run

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Message-ID: <Z4To3x2dCGEi6hJX@pollux>
Date: Mon, 13 Jan 2025 11:20:15 +0100
From: Danilo Krummrich <dakr@...nel.org>
To: Philipp Stanner <phasta@...nel.org>
Cc: Luben Tuikov <ltuikov89@...il.com>,
	Matthew Brost <matthew.brost@...el.com>,
	Philipp Stanner <pstanner@...hat.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
	Sumit Semwal <sumit.semwal@...aro.org>,
	Christian König <christian.koenig@....com>,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	linux-media@...r.kernel.org, linaro-mm-sig@...ts.linaro.org
Subject: Re: [PATCH 2/3] drm/sched: Adjust outdated docu for run_job()

On Thu, Jan 09, 2025 at 02:37:11PM +0100, Philipp Stanner wrote:
> The documentation for drm_sched_backend_ops.run_job() mentions a certain
> function called drm_sched_job_recovery(). This function does not exist.
> What's actually meant is drm_sched_resubmit_jobs(), which is by now also
> deprecated.
> 
> Remove the mention of the deprecated function.
> 
> Discourage the behavior of drm_sched_backend_ops.run_job() being called
> multiple times for the same job.
> 
> Signed-off-by: Philipp Stanner <phasta@...nel.org>
> ---
>  include/drm/gpu_scheduler.h | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
> index d5cd2a78f27c..c4e65f9f7f22 100644
> --- a/include/drm/gpu_scheduler.h
> +++ b/include/drm/gpu_scheduler.h
> @@ -421,9 +421,12 @@ struct drm_sched_backend_ops {
>  
>  	/**
>  	 * @run_job: Called to execute the job once all of the dependencies
> -	 * have been resolved. This may be called multiple times, if
> -	 * timedout_job() has happened and drm_sched_job_recovery() decides to
> -	 * try it again.
> +	 * have been resolved.
> +	 *
> +	 * The deprecated drm_sched_resubmit_jobs() (called from
> +	 * drm_sched_backend_ops.timedout_job()) can invoke this again with the
> +	 * same parameters. Doing this is strongly discouraged because it

Maybe "invoke this again for the same job"?

> +	 * violates dma_fence rules.

Does it? AFAIU it puts certain expectations on the driver, before a driver can
call this function, which likely leads to the driver to violate dma_fence rules,
right?

Maybe we should also list the exact rules that are (likely to be) violated to
allow drivers to fix it at their end more easily.

>  	 *
>  	 * @sched_job: the job to run
>  	 *
> -- 
> 2.47.1
>