linux-kernel - [PATCH 06/13] READ_ONCE: Remove smp_read_barrier

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Message-Id: <20191108170120.22331-7-will@kernel.org>
Date:   Fri,  8 Nov 2019 17:01:13 +0000
From:   Will Deacon <will@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     Will Deacon <will@...nel.org>, Yunjae Lee <lyj7694@...il.com>,
        SeongJae Park <sj38.park@...il.com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Josh Triplett <josh@...htriplett.org>,
        Matt Turner <mattst88@...il.com>,
        Ivan Kokshaysky <ink@...assic.park.msu.ru>,
        Richard Henderson <rth@...ddle.net>,
        Peter Zijlstra <peterz@...radead.org>,
        Alan Stern <stern@...land.harvard.edu>,
        Michael Ellerman <mpe@...erman.id.au>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Arnd Bergmann <arnd@...db.de>, Joe Perches <joe@...ches.com>,
        Boqun Feng <boqun.feng@...il.com>, linux-alpha@...r.kernel.org,
        virtualization@...ts.linux-foundation.org
Subject: [PATCH 06/13] READ_ONCE: Remove smp_read_barrier_depends() invocation

Alpha overrides '__read_once_size_n()' directly, so there's no need to
use 'smp_read_barrier_depends()' in the core code.

Signed-off-by: Will Deacon <will@...nel.org>
---
 include/asm-generic/rwonce.h | 1 -
 1 file changed, 1 deletion(-)

diff --git a/include/asm-generic/rwonce.h b/include/asm-generic/rwonce.h
index 2c2ac0948c94..2e3289268a89 100644
--- a/include/asm-generic/rwonce.h
+++ b/include/asm-generic/rwonce.h
@@ -102,7 +102,6 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
 		__read_once_size(&(x), __u.__c, sizeof(x));		\
 	else								\
 		__read_once_size_nocheck(&(x), __u.__c, sizeof(x));	\
-	smp_read_barrier_depends(); /* Enforce dependency ordering from x */ \
 	__u.__val;							\
 })
 #define READ_ONCE(x) __READ_ONCE(x, 1)
-- 
2.24.0.rc1.363.gb1bccd3e3d-goog