linux-kernel - Re: [PATCH 1/2] drm/msm: Move hangcheck timer restart

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Message-ID: <c80d70b6-a7ad-5900-ea7a-f0f2157e4a40@quicinc.com>
Date:   Thu, 4 Aug 2022 01:22:21 +0530
From:   Akhil P Oommen <quic_akhilpo@...cinc.com>
To:     Rob Clark <robdclark@...il.com>, <dri-devel@...ts.freedesktop.org>
CC:     <linux-arm-msm@...r.kernel.org>, <freedreno@...ts.freedesktop.org>,
        "Rob Clark" <robdclark@...omium.org>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] drm/msm: Move hangcheck timer restart

On 8/3/2022 10:53 PM, Rob Clark wrote:
> From: Rob Clark <robdclark@...omium.org>
> 
> Don't directly restart the hangcheck timer from the timer handler, but
> instead start it after the recover_worker replays remaining jobs.
> 
> If the kthread is blocked for other reasons, there is no point to
> immediately restart the timer.  Fixes a random symptom of the problem
> fixed in the next patch.
> 
> Signed-off-by: Rob Clark <robdclark@...omium.org>
> ---
>   drivers/gpu/drm/msm/msm_gpu.c | 14 +++++++++-----
>   1 file changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/msm_gpu.c b/drivers/gpu/drm/msm/msm_gpu.c
> index fba85f894314..8f9c48eabf7d 100644
> --- a/drivers/gpu/drm/msm/msm_gpu.c
> +++ b/drivers/gpu/drm/msm/msm_gpu.c
> @@ -328,6 +328,7 @@ find_submit(struct msm_ringbuffer *ring, uint32_t fence)
>   }
>   
>   static void retire_submits(struct msm_gpu *gpu);
> +static void hangcheck_timer_reset(struct msm_gpu *gpu);
>   
>   static void get_comm_cmdline(struct msm_gem_submit *submit, char **comm, char **cmd)
>   {
> @@ -420,6 +421,8 @@ static void recover_worker(struct kthread_work *work)
>   	}
>   
>   	if (msm_gpu_active(gpu)) {
> +		bool restart_hangcheck = false;
> +
>   		/* retire completed submits, plus the one that hung: */
>   		retire_submits(gpu);
>   
> @@ -436,10 +439,15 @@ static void recover_worker(struct kthread_work *work)
>   			unsigned long flags;
>   
>   			spin_lock_irqsave(&ring->submit_lock, flags);
> -			list_for_each_entry(submit, &ring->submits, node)
> +			list_for_each_entry(submit, &ring->submits, node) {
>   				gpu->funcs->submit(gpu, submit);
> +				restart_hangcheck = true;
> +			}
>   			spin_unlock_irqrestore(&ring->submit_lock, flags);
>   		}
> +
> +		if (restart_hangcheck)
> +			hangcheck_timer_reset(gpu);
>   	}
>   
>   	mutex_unlock(&gpu->lock);
> @@ -515,10 +523,6 @@ static void hangcheck_handler(struct timer_list *t)
>   		kthread_queue_work(gpu->worker, &gpu->recover_work);
>   	}
>   
> -	/* if still more pending work, reset the hangcheck timer: */
In the scenario mentioned here, shouldn't we restart the timer?

-Akhil.
> -	if (fence_after(ring->fctx->last_fence, ring->hangcheck_fence))
> -		hangcheck_timer_reset(gpu);
> -
>   	/* workaround for missing irq: */
>   	msm_gpu_retire(gpu);
>   }
>