linux-kernel - Re: [PATCH] drm/sched: warn about drm_sched_job

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Message-ID: <ZxsDRWxVRt2fCKpF@DUT025-TGLU.fm.intel.com>
Date: Fri, 25 Oct 2024 02:32:37 +0000
From: Matthew Brost <matthew.brost@...el.com>
To: Philipp Stanner <pstanner@...hat.com>
CC: Luben Tuikov <ltuikov89@...il.com>, Danilo Krummrich <dakr@...nel.org>,
	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>, Christian
 König <christian.koenig@....com>, Tvrtko Ursulin
	<tursulin@...lia.com>, <dri-devel@...ts.freedesktop.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/sched: warn about drm_sched_job_init()'s partial init

On Wed, Oct 23, 2024 at 04:15:31PM +0200, Philipp Stanner wrote:
> drm_sched_job_init()'s name suggests that after the function succeeded,
> parameter "job" will be fully initialized. This is not the case; some
> members are only later set, notably drm_sched_job.sched by
> drm_sched_job_arm().
> 
> Document that drm_sched_job_init() does not set all struct members.
> 
> Document the lifetime of drm_sched_job.sched.
> 
> Signed-off-by: Philipp Stanner <pstanner@...hat.com>

Reviewed-by: Matthew Brost <matthew.brost@...el.com>

> ---
>  drivers/gpu/drm/scheduler/sched_main.c | 4 ++++
>  include/drm/gpu_scheduler.h            | 8 ++++++++
>  2 files changed, 12 insertions(+)
> 
> diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
> index dab8cca79eb7..8c1c4739f36d 100644
> --- a/drivers/gpu/drm/scheduler/sched_main.c
> +++ b/drivers/gpu/drm/scheduler/sched_main.c
> @@ -771,6 +771,10 @@ EXPORT_SYMBOL(drm_sched_resubmit_jobs);
>   * Drivers must make sure drm_sched_job_cleanup() if this function returns
>   * successfully, even when @job is aborted before drm_sched_job_arm() is called.
>   *
> + * Note that this function does not assign a valid value to each struct member
> + * of struct drm_sched_job. Take a look at that struct's documentation to see
> + * who sets which struct member with what lifetime.
> + *
>   * WARNING: amdgpu abuses &drm_sched.ready to signal when the hardware
>   * has died, which can mean that there's no valid runqueue for a @entity.
>   * This function returns -ENOENT in this case (which probably should be -EIO as
> diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
> index ab161289d1bf..95e17504e46a 100644
> --- a/include/drm/gpu_scheduler.h
> +++ b/include/drm/gpu_scheduler.h
> @@ -340,6 +340,14 @@ struct drm_sched_fence *to_drm_sched_fence(struct dma_fence *f);
>  struct drm_sched_job {
>  	struct spsc_node		queue_node;
>  	struct list_head		list;
> +
> +	/**
> +	 * @sched:
> +	 *
> +	 * The scheduler this job is or will be scheduled on. Gets set by
> +	 * drm_sched_job_arm(). Valid until drm_sched_backend_ops.free_job()
> +	 * has finished.
> +	 */
>  	struct drm_gpu_scheduler	*sched;
>  	struct drm_sched_fence		*s_fence;
>  
> -- 
> 2.47.0
>