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From:   Rob Herring <robh@kernel.org>
Date:   Thu, 9 Jul 2020 09:44:36 -0600
Message-ID: <CAL_JsqL=+ToP1w3m8GdK0K0o8ER2eYSiM5ffuFVxyMsZns4gqA@mail.gmail.com>
Subject: Re: [PATCH] drm/panfrost: fix ref count leak in panfrost_job_hw_submit
To:     Navid Emamdoost <navid.emamdoost@gmail.com>
Cc:     Tomeu Vizoso <tomeu.vizoso@collabora.com>,
        Steven Price <steven.price@arm.com>,
        Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        dri-devel <dri-devel@lists.freedesktop.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Navid Emamdoost <emamd001@umn.edu>, wu000273@umn.edu,
        kjlu@umn.edu, Stephen McCamant <smccaman@umn.edu>
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On Sun, Jun 14, 2020 at 12:27 AM Navid Emamdoost
<navid.emamdoost@gmail.com> wrote:
>
> in panfrost_job_hw_submit, pm_runtime_get_sync is called which
> increments the counter even in case of failure, leading to incorrect
> ref count. In case of failure, decrement the ref count before returning.
>
> Signed-off-by: Navid Emamdoost <navid.emamdoost@gmail.com>
> ---
>  drivers/gpu/drm/panfrost/panfrost_job.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c b/drivers/gpu/drm/panfrost/panfrost_job.c
> index 7914b1570841..89ac84667eb1 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_job.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_job.c
> @@ -147,11 +147,10 @@ static void panfrost_job_hw_submit(struct panfrost_job *job, int js)
>
>         ret = pm_runtime_get_sync(pfdev->dev);
>         if (ret < 0)
> -               return;
> +               goto out;

If the get failed, I don't think we want to do a put.

>
>         if (WARN_ON(job_read(pfdev, JS_COMMAND_NEXT(js)))) {
> -               pm_runtime_put_sync_autosuspend(pfdev->dev);
> -               return;
> +               goto out;
>         }
>
>         cfg = panfrost_mmu_as_get(pfdev, &job->file_priv->mmu);
> @@ -184,6 +183,9 @@ static void panfrost_job_hw_submit(struct panfrost_job *job, int js)
>                                 job, js, jc_head);
>
>         job_write(pfdev, JS_COMMAND_NEXT(js), JS_COMMAND_START);

So we start the job here and then...

> +out:
> +       pm_runtime_put_sync_autosuspend(pfdev->dev);

...turn off clocks/power here. Typically, you'd be fine as autosuspend
has a delay by default, but userspace is free to change the delay to
0.

> +       return;
>  }
>
>  static void panfrost_acquire_object_fences(struct drm_gem_object **bos,
> --
> 2.17.1
>