Subject: Re: [PATCH 01/11] drm/vgem: Use ww_mutex_(un)lock even with a NULL
 context
To: =?UTF-8?Q?Nicolai_H=c3=a4hnle?= <nhaehnle@gmail.com>,
        linux-kernel@vger.kernel.org
References: <1480335612-12069-1-git-send-email-nhaehnle@gmail.com>
 <1480335612-12069-2-git-send-email-nhaehnle@gmail.com>
Cc: =?UTF-8?Q?Nicolai_H=c3=a4hnle?= <Nicolai.Haehnle@amd.com>,
        Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@redhat.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        Chris Wilson <chris@chris-wilson.co.uk>,
        dri-devel@lists.freedesktop.org
From: Maarten Lankhorst <dev@mblankhorst.nl>
Message-ID: <03202725-ecf3-1b49-f22a-1cbff84156bc@mblankhorst.nl>
Date: Mon, 28 Nov 2016 13:42:26 +0100
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Op 28-11-16 om 13:20 schreef Nicolai Hähnle:
> From: Nicolai Hähnle <Nicolai.Haehnle@amd.com>
>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Maarten Lankhorst <dev@mblankhorst.nl>
> Cc: Daniel Vetter <daniel@ffwll.ch>
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: dri-devel@lists.freedesktop.org
> Signed-off-by: Nicolai Hähnle <Nicolai.Haehnle@amd.com>
> ---
>  drivers/gpu/drm/vgem/vgem_fence.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/vgem/vgem_fence.c b/drivers/gpu/drm/vgem/vgem_fence.c
> index 488909a..e1d516f 100644
> --- a/drivers/gpu/drm/vgem/vgem_fence.c
> +++ b/drivers/gpu/drm/vgem/vgem_fence.c
> @@ -191,12 +191,12 @@ int vgem_fence_attach_ioctl(struct drm_device *dev,
>  
>  	/* Expose the fence via the dma-buf */
>  	ret = 0;
> -	mutex_lock(&resv->lock.base);
> +	ww_mutex_lock(&resv->lock.base, NULL);
Yuck, can we rename base to __NEVER_TOUCH_DIRECTLY_OUTSIDE_LOCKING_CORE?
It's harder to get them confused like that, even with a null context it's illegal to call mutex_lock/unlock directly.

~Maarten