linux-kernel - Re: [PATCH] drm/panthor: Defer scheduler entitiy destruction to queue release

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Message-ID: <30f56d2a-941c-4876-90e6-c7054b51ec10@arm.com>
Date: Wed, 24 Sep 2025 11:31:21 +0100
From: Steven Price <steven.price@....com>
To: Adrián Larumbe <adrian.larumbe@...labora.com>,
 linux-kernel@...r.kernel.org
Cc: dri-devel@...ts.freedesktop.org,
 Boris Brezillon <boris.brezillon@...labora.com>, kernel@...labora.com,
 Liviu Dudau <liviu.dudau@....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>,
 Heiko Stuebner <heiko@...ech.de>
Subject: Re: [PATCH] drm/panthor: Defer scheduler entitiy destruction to queue
 release

On 19/09/2025 17:43, Adrián Larumbe wrote:
> Commit de8548813824 ("drm/panthor: Add the scheduler logical block")
> handled destruction of a group's queues' drm scheduler entities early
> into the group destruction procedure.
> 
> However, that races with the group submit ioctl, because by the time
> entities are destroyed (through the group destroy ioctl), the submission
> procedure might've already obtained a group handle, and therefore the
> ability to push jobs into entities. This is met with a DRM error message
> within the drm scheduler core as a situation that should never occur.
> 
> Fix by deferring drm scheduler entity destruction to queue release time.
> 
> Fixes: de8548813824 ("drm/panthor: Add the scheduler logical block")
> Signed-off-by: Adrián Larumbe <adrian.larumbe@...labora.com>

Looks good - I can't figure out why we had the early destruction, this
is more simple and safer.

Reviewed-by: Steven Price <steven.price@....com>

Thanks,
Steve

> ---
>  drivers/gpu/drm/panthor/panthor_sched.c | 8 +-------
>  1 file changed, 1 insertion(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c
> index 0cc9055f4ee5..f5e01cb16cfc 100644
> --- a/drivers/gpu/drm/panthor/panthor_sched.c
> +++ b/drivers/gpu/drm/panthor/panthor_sched.c
> @@ -898,8 +898,7 @@ static void group_free_queue(struct panthor_group *group, struct panthor_queue *
>  	if (IS_ERR_OR_NULL(queue))
>  		return;
>  
> -	if (queue->entity.fence_context)
> -		drm_sched_entity_destroy(&queue->entity);
> +	drm_sched_entity_destroy(&queue->entity);
>  
>  	if (queue->scheduler.ops)
>  		drm_sched_fini(&queue->scheduler);
> @@ -3609,11 +3608,6 @@ int panthor_group_destroy(struct panthor_file *pfile, u32 group_handle)
>  	if (!group)
>  		return -EINVAL;
>  
> -	for (u32 i = 0; i < group->queue_count; i++) {
> -		if (group->queues[i])
> -			drm_sched_entity_destroy(&group->queues[i]->entity);
> -	}
> -
>  	mutex_lock(&sched->reset.lock);
>  	mutex_lock(&sched->lock);
>  	group->destroyed = true;