Re: [PATCH] drm: Take mode_config.mutex in setcrtc ioctl

From: Alex Deucher <alexdeucher@gmail.com>
To: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Intel Graphics Development <intel-gfx@lists.freedesktop.org>,
	DRI Development <dri-devel@lists.freedesktop.org>,
	Daniel Vetter <daniel.vetter@intel.com>
Subject: Re: [PATCH] drm: Take mode_config.mutex in setcrtc ioctl
Date: Thu, 6 Apr 2017 15:09:04 -0400	[thread overview]
Message-ID: <CADnq5_O9TJV=HXLF7_1G6TZESqr_2a7s11bJxuUGAX7ziAn47Q@mail.gmail.com> (raw)
In-Reply-To: <20170406190654.6733-1-daniel.vetter@ffwll.ch>

On Thu, Apr 6, 2017 at 3:06 PM, Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> Legacy drivers insist that we really take all the locks in this path,
> and the harm in doing so is minimal.
>
> v2: Like git add, it exists :(
>
> Fixes: 2ceb585a956c ("drm: Add explicit acquire ctx handling around ->set_config")
> Cc: Harry Wentland <harry.wentland@amd.com>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: Daniel Vetter <daniel.vetter@intel.com>
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Cc: Sean Paul <seanpaul@chromium.org>
> Cc: David Airlie <airlied@linux.ie>
> Cc: dri-devel@lists.freedesktop.org
> Cc: Alex Deucher <alexdeucher@gmail.com>
> Reported-by: Alex Deucher <alexdeucher@gmail.com>
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>

This actually matches what I tested locally.

Acked-and-tested-by: Alex Deucher <alexander.deucher@amd.com>

> ---
>  drivers/gpu/drm/drm_crtc.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> index d69e180fc563..5af25ce5bf7c 100644
> --- a/drivers/gpu/drm/drm_crtc.c
> +++ b/drivers/gpu/drm/drm_crtc.c
> @@ -576,6 +576,7 @@ int drm_mode_setcrtc(struct drm_device *dev, void *data,
>         }
>         DRM_DEBUG_KMS("[CRTC:%d:%s]\n", crtc->base.id, crtc->name);
>
> +       mutex_lock(&crtc->dev->mode_config.mutex);
>         drm_modeset_acquire_init(&ctx, 0);
>  retry:
>         ret = drm_modeset_lock_all_ctx(crtc->dev, &ctx);
> @@ -721,6 +722,7 @@ int drm_mode_setcrtc(struct drm_device *dev, void *data,
>         }
>         drm_modeset_drop_locks(&ctx);
>         drm_modeset_acquire_fini(&ctx);
> +       mutex_unlock(&crtc->dev->mode_config.mutex);
>
>         return ret;
>  }
> --
> 2.11.0
>
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