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

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Message-ID: <7f7bd85a-2444-1939-4ac8-dbf2685eaf24@quicinc.com>
Date:   Thu, 4 Aug 2022 13:23:00 +0530
From:   Akhil P Oommen <quic_akhilpo@...cinc.com>
To:     Rob Clark <robdclark@...il.com>
CC:     <dri-devel@...ts.freedesktop.org>, <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 8/4/2022 1:59 AM, Rob Clark wrote:
> On Wed, Aug 3, 2022 at 12:52 PM Akhil P Oommen <quic_akhilpo@...cinc.com> wrote:
>> 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?
> yeah, actually the case where we don't want to restart the timer is
> *only* when we schedule recover_work..
>
> BR,
> -R
Not sure if your codebase is different but based on msm-next branch, 
when "if (fence != ring->hangcheck_fence)" is true, we now skip 
rescheduling the timer. I don't think that is what we want. There should 
be a hangcheck timer running as long as there is an active submit, 
unless we have scheduled a recover_work here.

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