Re: [PATCH] drm: Convert cmpxchg(bool) back to a two step operation

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Thu, Mar 30, 2017 at 03:08:32PM +0100, Chris Wilson wrote:
> ARM v6 (at least) only allows cmpxchg on 32bit variables which doesn't
> always include the bool type.
> 
> drivers/built-in.o: In function `vblank_disable_and_save':
> imx-ocotp.c:(.text+0xb45e8): undefined reference to `__bad_cmpxchg'
> Makefile:986: recipe for target 'vmlinux' failed
> 
> Reported-by: kbuild test robot <fengguang.wu@intel.com>
> Reported-by: Leonard Crestez <leonard.crestez@nxp.com>
> Fixes: 43dc7fe2b211 ("drm: Mark up accesses of vblank->enabled outside of its spinlock")
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>

Thanks for the quick fix. Pushed to drm-misc-next.

> ---
>  drivers/gpu/drm/drm_irq.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
> index aa23b9833588..dac1b2593cb1 100644
> --- a/drivers/gpu/drm/drm_irq.c
> +++ b/drivers/gpu/drm/drm_irq.c
> @@ -338,8 +338,10 @@ static void vblank_disable_and_save(struct drm_device *dev, unsigned int pipe)
>  	 * calling the ->disable_vblank() operation in atomic context with the
>  	 * hardware potentially runtime suspended.
>  	 */
> -	if (cmpxchg_relaxed(&vblank->enabled, true, false))
> +	if (vblank->enabled) {
>  		__disable_vblank(dev, pipe);
> +		vblank->enabled = false;
> +	}
>  
>  	/*
>  	 * Always update the count and timestamp to maintain the
> -- 
> 2.11.0

-- 
Ville Syrjälä
Intel OTC
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