Re: [PATCH 1/5] drm/msm: Fix improper uses of smp_mb__{before,after}_atomic()

[Andrea Parri]

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@xxxxxxxxxxxxxxx
> Reported-by: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxx>
> Reported-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Signed-off-by: Andrea Parri <andrea.parri@xxxxxxxxxxxxxxxxxxxx>
> Cc: Rob Clark <robdclark@xxxxxxxxx>
> Cc: Sean Paul <sean@xxxxxxxxxx>
> Cc: David Airlie <airlied@xxxxxxxx>
> Cc: Daniel Vetter <daniel@xxxxxxxx>
> Cc: Jordan Crouse <jcrouse@xxxxxxxxxxxxxx>
> Cc: linux-arm-msm@xxxxxxxxxxxxxxx
> Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
> Cc: freedreno@xxxxxxxxxxxxxxxxxxxxx

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
>