linux-kernel - Re: [PATCH v2 01/10] media: v4l2-ctrls: Add missing v4l2 ctrl unlock

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Message-ID: <20180420072316.sifritx54mppgwz3@flea>
Date:   Fri, 20 Apr 2018 09:23:16 +0200
From:   Maxime Ripard <maxime.ripard@...tlin.com>
To:     Paul Kocialkowski <paul.kocialkowski@...tlin.com>
Cc:     linux-media@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-sunxi@...glegroups.com,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Chen-Yu Tsai <wens@...e.org>, Pawel Osciak <pawel@...iak.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Arnd Bergmann <arnd@...db.de>,
        Alexandre Courbot <acourbot@...omium.org>,
        Tomasz Figa <tfiga@...omium.org>
Subject: Re: [PATCH v2 01/10] media: v4l2-ctrls: Add missing v4l2 ctrl unlock

On Thu, Apr 19, 2018 at 05:41:15PM +0200, Paul Kocialkowski wrote:
> This adds a missing v4l2_ctrl_unlock call that is required to avoid
> deadlocks.

Maybe you can explain what the deadlock scenario is?

> Signed-off-by: Paul Kocialkowski <paul.kocialkowski@...tlin.com>
> ---
>  drivers/media/v4l2-core/v4l2-ctrls.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
> index f67e9f5531fa..ba05a8b9a095 100644
> --- a/drivers/media/v4l2-core/v4l2-ctrls.c
> +++ b/drivers/media/v4l2-core/v4l2-ctrls.c
> @@ -3614,10 +3614,12 @@ void v4l2_ctrl_request_complete(struct media_request *req,
>  			continue;
>  
>  		v4l2_ctrl_lock(ctrl);
> +
>  		if (ref->req)
>  			ptr_to_ptr(ctrl, ref->req->p_req, ref->p_req);
>  		else
>  			ptr_to_ptr(ctrl, ctrl->p_cur, ref->p_req);
> +

I'm not sure that this is relevant in this patch.

Maxime

-- 
Maxime Ripard, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com

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