linux-kernel - Re: [PATCH] vt: Grab console_lock around con_is_bound in show

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Message-ID: <20190723073820.GU15868@phenom.ffwll.local>
Date:   Tue, 23 Jul 2019 09:38:20 +0200
From:   Daniel Vetter <daniel@...ll.ch>
To:     Intel Graphics Development <intel-gfx@...ts.freedesktop.org>
Cc:     Daniel Vetter <daniel.vetter@...ll.ch>,
        Jens Remus <jremus@...ux.ibm.com>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-fbdev@...r.kernel.org, linux-s390@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Nicolas Pitre <nicolas.pitre@...aro.org>,
        Martin Hostettler <textshell@...uujin.de>,
        Adam Borowski <kilobyte@...band.pl>,
        Mikulas Patocka <mpatocka@...hat.com>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Sam Ravnborg <sam@...nborg.org>
Subject: Re: [PATCH] vt: Grab console_lock around con_is_bound in show_bind

Hi Greg,

Do you plan to pick this up in your console/vt/whatever-fixes branch?
There's no reason for me to route this through drm-fixes.
-Daniel

On Thu, Jul 18, 2019 at 10:09:03AM +0200, Daniel Vetter wrote:
> Not really harmful not to, but also not harm in grabbing the lock. And
> this shuts up a new WARNING I introduced in commit ddde3c18b700 ("vt:
> More locking checks").
> 
> Reported-by: Jens Remus <jremus@...ux.ibm.com>
> Cc: linux-kernel@...r.kernel.org
> Cc: dri-devel@...ts.freedesktop.org
> Cc: linux-fbdev@...r.kernel.org
> Cc: linux-s390@...r.kernel.org
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Nicolas Pitre <nicolas.pitre@...aro.org>
> Cc: Martin Hostettler <textshell@...uujin.de>
> Cc: Adam Borowski <kilobyte@...band.pl>
> Cc: Mikulas Patocka <mpatocka@...hat.com>
> Signed-off-by: Daniel Vetter <daniel.vetter@...el.com>
> Cc: Daniel Vetter <daniel.vetter@...ll.ch>
> Cc: Sam Ravnborg <sam@...nborg.org>
> ---
>  drivers/tty/vt/vt.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
> index ec92f36ab5c4..34aa39d1aed9 100644
> --- a/drivers/tty/vt/vt.c
> +++ b/drivers/tty/vt/vt.c
> @@ -3771,7 +3771,11 @@ static ssize_t show_bind(struct device *dev, struct device_attribute *attr,
>  			 char *buf)
>  {
>  	struct con_driver *con = dev_get_drvdata(dev);
> -	int bind = con_is_bound(con->con);
> +	int bind;
> +
> +	console_lock();
> +	bind = con_is_bound(con->con);
> +	console_unlock();
>  
>  	return snprintf(buf, PAGE_SIZE, "%i\n", bind);
>  }
> -- 
> 2.20.1
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch