linux-kernel - Re: [PATCH v1] drm/scheduler: Don't kill jobs in interrupt context

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Date:   Wed, 13 Apr 2022 11:04:56 +0100
From:   Steven Price <steven.price@....com>
To:     Dmitry Osipenko <dmitry.osipenko@...labora.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        Rob Herring <robh@...nel.org>,
        Alyssa Rosenzweig <alyssa.rosenzweig@...labora.com>,
        Rob Clark <robdclark@...il.com>,
        Andrey Grodzovsky <andrey.grodzovsky@....com>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Dmitry Osipenko <digetx@...il.com>
Subject: Re: [PATCH v1] drm/scheduler: Don't kill jobs in interrupt context

On 11/04/2022 23:15, Dmitry Osipenko wrote:
> Interrupt context can't sleep. Drivers like Panfrost and MSM are taking
> mutex when job is released, and thus, that code can sleep. This results
> into "BUG: scheduling while atomic" if locks are contented while job is
> freed. There is no good reason for releasing scheduler's jobs in IRQ
> context, hence use normal context to fix the trouble.
> 
> Cc: stable@...r.kernel.org
> Fixes: 542cff7893a3 ("drm/sched: Avoid lockdep spalt on killing a processes")
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@...labora.com>

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

> ---
>  drivers/gpu/drm/scheduler/sched_entity.c | 6 +++---
>  include/drm/gpu_scheduler.h              | 4 ++--
>  2 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c
> index 191c56064f19..6b25b2f4f5a3 100644
> --- a/drivers/gpu/drm/scheduler/sched_entity.c
> +++ b/drivers/gpu/drm/scheduler/sched_entity.c
> @@ -190,7 +190,7 @@ long drm_sched_entity_flush(struct drm_sched_entity *entity, long timeout)
>  }
>  EXPORT_SYMBOL(drm_sched_entity_flush);
>  
> -static void drm_sched_entity_kill_jobs_irq_work(struct irq_work *wrk)
> +static void drm_sched_entity_kill_jobs_work(struct work_struct *wrk)
>  {
>  	struct drm_sched_job *job = container_of(wrk, typeof(*job), work);
>  
> @@ -207,8 +207,8 @@ static void drm_sched_entity_kill_jobs_cb(struct dma_fence *f,
>  	struct drm_sched_job *job = container_of(cb, struct drm_sched_job,
>  						 finish_cb);
>  
> -	init_irq_work(&job->work, drm_sched_entity_kill_jobs_irq_work);
> -	irq_work_queue(&job->work);
> +	INIT_WORK(&job->work, drm_sched_entity_kill_jobs_work);
> +	schedule_work(&job->work);
>  }
>  
>  static struct dma_fence *
> diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
> index 0fca8f38bee4..addb135eeea6 100644
> --- a/include/drm/gpu_scheduler.h
> +++ b/include/drm/gpu_scheduler.h
> @@ -28,7 +28,7 @@
>  #include <linux/dma-fence.h>
>  #include <linux/completion.h>
>  #include <linux/xarray.h>
> -#include <linux/irq_work.h>
> +#include <linux/workqueue.h>
>  
>  #define MAX_WAIT_SCHED_ENTITY_Q_EMPTY msecs_to_jiffies(1000)
>  
> @@ -295,7 +295,7 @@ struct drm_sched_job {
>  	 */
>  	union {
>  		struct dma_fence_cb		finish_cb;
> -		struct irq_work 		work;
> +		struct work_struct 		work;
>  	};
>  
>  	uint64_t			id;