linux-kernel - Re: [PATCH 2/2] media: venus: sync with threaded IRQ during inst destruction

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Message-ID: <CAAFQd5ACxz-3icNH_CwWxWj5OyKdg89mOkNadYKa=YTVDRYRLg@mail.gmail.com>
Date: Thu, 24 Oct 2024 14:18:32 +0900
From: Tomasz Figa <tfiga@...omium.org>
To: Sergey Senozhatsky <senozhatsky@...omium.org>
Cc: Stanimir Varbanov <stanimir.k.varbanov@...il.com>, 
	Vikash Garodia <quic_vgarodia@...cinc.com>, "Bryan O'Donoghue" <bryan.odonoghue@...aro.org>, 
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] media: venus: sync with threaded IRQ during inst destruction

Hi Sergey,

On Thu, Oct 24, 2024 at 2:13 PM Sergey Senozhatsky
<senozhatsky@...omium.org> wrote:
>
> On (24/10/24 13:58), Sergey Senozhatsky wrote:
> > Date: Thu, 24 Oct 2024 13:58:36 +0900
> > From: Sergey Senozhatsky <senozhatsky@...omium.org>
> > To: Sergey Senozhatsky <senozhatsky@...omium.org>
> > Cc: Stanimir Varbanov <stanimir.k.varbanov@...il.com>, Vikash Garodia
> >  <quic_vgarodia@...cinc.com>, Bryan O'Donoghue
> >  <bryan.odonoghue@...aro.org>, linux-media@...r.kernel.org,
> >  linux-kernel@...r.kernel.org
> > Subject: Re: [PATCH 2/2] media: venus: sync with threaded IRQ during inst
> >  destruction
> > Message-ID: <20241024045836.GJ1279924@...gle.com>
> >
> > On (24/10/23 14:24), Sergey Senozhatsky wrote:
> > > Guard inst destruction (both dec and enc) with hard and threaded
> > > IRQ synchronization.
> >
> > Folks, please ignore this patch.   Stand by for v2.
>
> I think it probably should be something like this (both for dec and
> enc).
>
> ---
>
> @@ -1538,9 +1538,25 @@ static int venc_close(struct file *file)
>
>         venc_pm_get(inst);
>
> +       /*
> +        * First, remove the inst from the ->instances list, so that
> +        * to_instance() will return NULL.
> +        */
> +       hfi_session_destroy(inst);
> +       /*
> +        * Second, make sure we don't have IRQ/IRQ-thread currently running or
> +        * pending execution (disable_irq() calls synchronize_irq()), which
> +        * can race with the inst destruction.
> +        */
> +       disable_irq(inst->core->irq);
> +       /*
> +        * Lastly, inst is gone from the core->instances list and we don't
> +        * have running/pending IRQ/IRQ-thread, proceed with the destruction
> +        */
> +       enable_irq(inst->core->irq);
> +

Thanks a lot for looking into this. Wouldn't it be enough to just call
synchronize_irq() at this point, since the instance was removed from
the list already? I guess the question is if that's the only way the
interrupt handler can get hold of the instance.

Best,
Tomasz

>         v4l2_m2m_ctx_release(inst->m2m_ctx);
>         v4l2_m2m_release(inst->m2m_dev);
> -       hfi_session_destroy(inst);
>         v4l2_fh_del(&inst->fh);
>         v4l2_fh_exit(&inst->fh);
>         venc_ctrl_deinit(inst);
>