linux-kernel - Re: [PATCH 1/5] drm/msm: Fix improper uses of smp_mb__{before,after}

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Message-ID: <20190509201915.GA2931@andrea>
Date:   Thu, 9 May 2019 22:19:15 +0200
From:   Andrea Parri <andrea.parri@...rulasolutions.com>
To:     linux-kernel@...r.kernel.org
Cc:     Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Jordan Crouse <jcrouse@...eaurora.org>,
        linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org,
        "Paul E. McKenney" <paulmck@...ux.ibm.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH 1/5] drm/msm: Fix improper uses of
 smp_mb__{before,after}_atomic()

On Mon, Apr 29, 2019 at 10:14:57PM +0200, Andrea Parri wrote:
> These barriers only apply to the read-modify-write operations; in
> particular, they do not apply to the atomic_set() primitive.
> 
> Replace the barriers with smp_mb()s.
> 
> Fixes: b1fc2839d2f92 ("drm/msm: Implement preemption for A5XX targets")
> Cc: stable@...r.kernel.org
> Reported-by: "Paul E. McKenney" <paulmck@...ux.ibm.com>
> Reported-by: Peter Zijlstra <peterz@...radead.org>
> Signed-off-by: Andrea Parri <andrea.parri@...rulasolutions.com>
> Cc: Rob Clark <robdclark@...il.com>
> Cc: Sean Paul <sean@...rly.run>
> Cc: David Airlie <airlied@...ux.ie>
> Cc: Daniel Vetter <daniel@...ll.ch>
> Cc: Jordan Crouse <jcrouse@...eaurora.org>
> Cc: linux-arm-msm@...r.kernel.org
> Cc: dri-devel@...ts.freedesktop.org
> Cc: freedreno@...ts.freedesktop.org

Rob, Sean, Jordan: any suggestions to move this patch forward?

Thanx,
  Andrea


> ---
>  drivers/gpu/drm/msm/adreno/a5xx_preempt.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/adreno/a5xx_preempt.c b/drivers/gpu/drm/msm/adreno/a5xx_preempt.c
> index 3d62310a535fb..ee0820ee0c664 100644
> --- a/drivers/gpu/drm/msm/adreno/a5xx_preempt.c
> +++ b/drivers/gpu/drm/msm/adreno/a5xx_preempt.c
> @@ -39,10 +39,10 @@ static inline void set_preempt_state(struct a5xx_gpu *gpu,
>  	 * preemption or in the interrupt handler so barriers are needed
>  	 * before...
>  	 */
> -	smp_mb__before_atomic();
> +	smp_mb();
>  	atomic_set(&gpu->preempt_state, new);
>  	/* ... and after*/
> -	smp_mb__after_atomic();
> +	smp_mb();
>  }
>  
>  /* Write the most recent wptr for the given ring into the hardware */
> -- 
> 2.7.4
>