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From:   Andrea Parri <andrea.parri@amarulasolutions.com>
To:     linux-kernel@vger.kernel.org
Cc:     Andrea Parri <andrea.parri@amarulasolutions.com>,
        stable@vger.kernel.org, Rob Clark <robdclark@gmail.com>,
        Sean Paul <sean@poorly.run>, David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Jordan Crouse <jcrouse@codeaurora.org>,
        linux-arm-msm@vger.kernel.org, dri-devel@lists.freedesktop.org,
        freedreno@lists.freedesktop.org,
        "Paul E. McKenney" <paulmck@linux.ibm.com>,
        Peter Zijlstra <peterz@infradead.org>
Subject: [PATCH 1/4] drm/msm: Fix improper uses of smp_mb__{before,after}_atomic()
Date:   Mon, 20 May 2019 19:23:55 +0200
Message-Id: <1558373038-5611-2-git-send-email-andrea.parri@amarulasolutions.com>
In-Reply-To: <1558373038-5611-1-git-send-email-andrea.parri@amarulasolutions.com>
References: <1558373038-5611-1-git-send-email-andrea.parri@amarulasolutions.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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@vger.kernel.org
Reported-by: "Paul E. McKenney" <paulmck@linux.ibm.com>
Reported-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Cc: Rob Clark <robdclark@gmail.com>
Cc: Sean Paul <sean@poorly.run>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Jordan Crouse <jcrouse@codeaurora.org>
Cc: linux-arm-msm@vger.kernel.org
Cc: dri-devel@lists.freedesktop.org
Cc: freedreno@lists.freedesktop.org
Cc: "Paul E. McKenney" <paulmck@linux.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
---
 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