Re: [PATCH] drm/etnaviv: always start/stop scheduler in timeout processing

[Russell King - ARM Linux admin <linux@armlinux.org.uk>]

On Mon, Aug 24, 2020 at 01:02:48PM +0200, Lucas Stach wrote:
> The drm scheduler currently expects that the stop/start sequence is always
> executed in the timeout handling, as the job at the head of the hardware
> execution list is always removed from the ring mirror before the driver
> function is called and only inserted back into the list when starting the
> scheduler.
> 
> This adds some unnecessary overhead if the timeout handler determines
> that the GPU is still executing jobs normally and just wished to extend
> the timeout, but a better solution requires a major rearchitecture of the
> scheduler, which is not applicable as a fix.
> 
> Fixes: 135517d3565b drm/scheduler: Avoid accessing freed bad job.)
> Signed-off-by: Lucas Stach <l.stach@pengutronix.de>

From a brief test, this seems to fix the problem, thanks.

Tested-by: Russell King <rmk+kernel@armlinux.org.uk>

> ---
>  drivers/gpu/drm/etnaviv/etnaviv_sched.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_sched.c b/drivers/gpu/drm/etnaviv/etnaviv_sched.c
> index 4e3e95dce6d8..cd46c882269c 100644
> --- a/drivers/gpu/drm/etnaviv/etnaviv_sched.c
> +++ b/drivers/gpu/drm/etnaviv/etnaviv_sched.c
> @@ -89,12 +89,15 @@ static void etnaviv_sched_timedout_job(struct drm_sched_job *sched_job)
>  	u32 dma_addr;
>  	int change;
>  
> +	/* block scheduler */
> +	drm_sched_stop(&gpu->sched, sched_job);
> +
>  	/*
>  	 * If the GPU managed to complete this jobs fence, the timout is
>  	 * spurious. Bail out.
>  	 */
>  	if (dma_fence_is_signaled(submit->out_fence))
> -		return;
> +		goto out_no_timeout;
>  
>  	/*
>  	 * If the GPU is still making forward progress on the front-end (which
> @@ -105,12 +108,9 @@ static void etnaviv_sched_timedout_job(struct drm_sched_job *sched_job)
>  	change = dma_addr - gpu->hangcheck_dma_addr;
>  	if (change < 0 || change > 16) {
>  		gpu->hangcheck_dma_addr = dma_addr;
> -		return;
> +		goto out_no_timeout;
>  	}
>  
> -	/* block scheduler */
> -	drm_sched_stop(&gpu->sched, sched_job);
> -
>  	if(sched_job)
>  		drm_sched_increase_karma(sched_job);
>  
> @@ -120,6 +120,7 @@ static void etnaviv_sched_timedout_job(struct drm_sched_job *sched_job)
>  
>  	drm_sched_resubmit_jobs(&gpu->sched);
>  
> +out_no_timeout:
>  	/* restart scheduler after GPU is usable again */
>  	drm_sched_start(&gpu->sched, true);
>  }
> -- 
> 2.20.1
> 
> 

-- 
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