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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <CAF6AEGv8sYG=72ne4wMx_OQwWOUkx88fYdKM2EEszdmYzOrg1A@mail.gmail.com>
Date:   Thu, 4 Aug 2022 10:33:16 -0700
From:   Rob Clark <robdclark@...il.com>
To:     Akhil P Oommen <quic_akhilpo@...cinc.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 Thu, Aug 4, 2022 at 12:53 AM Akhil P Oommen <quic_akhilpo@...cinc.com> wrote:
>
> 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.
>

right, v2 will change that to only skip rescheduling the timer in the
recover path

BR,
-R

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