linux-kernel - Re: [PATCH 01/11] drm/vgem: Use ww_mutex

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Message-ID: <03202725-ecf3-1b49-f22a-1cbff84156bc@mblankhorst.nl>
Date:   Mon, 28 Nov 2016 13:42:26 +0100
From:   Maarten Lankhorst <dev@...ankhorst.nl>
To:     Nicolai Hähnle <nhaehnle@...il.com>,
        linux-kernel@...r.kernel.org
Cc:     Nicolai Hähnle <Nicolai.Haehnle@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH 01/11] drm/vgem: Use ww_mutex_(un)lock even with a NULL
 context

Op 28-11-16 om 13:20 schreef Nicolai Hähnle:
> From: Nicolai Hähnle <Nicolai.Haehnle@....com>
>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Maarten Lankhorst <dev@...ankhorst.nl>
> Cc: Daniel Vetter <daniel@...ll.ch>
> Cc: Chris Wilson <chris@...is-wilson.co.uk>
> Cc: dri-devel@...ts.freedesktop.org
> Signed-off-by: Nicolai Hähnle <Nicolai.Haehnle@....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