linux-kernel - [PATCH] x86: use WRITE_ONCE/READ_ONCE in smp_store_release/smp_load

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Date:	Sat,  1 Aug 2015 18:45:34 +0200
From:	Andrey Konovalov <andreyknvl@...gle.com>
To:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	"David S. Miller" <davem@...emloft.net>,
	Peter Zijlstra <peterz@...radead.org>,
	Alexander Duyck <alexander.h.duyck@...hat.com>,
	Borislav Petkov <bp@...e.de>, linux-kernel@...r.kernel.org
Cc:	Andrey Konovalov <andreyknvl@...gle.com>,
	Dmitry Vyukov <dvyukov@...gle.com>
Subject: [PATCH] x86: use WRITE_ONCE/READ_ONCE in smp_store_release/smp_load_acquire

Replace ACCESS_ONCE() macro in smp_store_release() and smp_load_acquire()
from arch/x86/include/asm/barrier.h with WRITE_ONCE() and READ_ONCE() since
ACCESS_ONCE does not work reliably on non-scalar types.

WRITE_ONCE() and READ_ONCE() were introduced in the commits 230fa253df63
("kernel: Provide READ_ONCE and ASSIGN_ONCE") and 43239cbe79fc ("kernel:
Change ASSIGN_ONCE(val, x) to WRITE_ONCE(x, val)").

Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
---
 arch/x86/include/asm/barrier.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/barrier.h b/arch/x86/include/asm/barrier.h
index e51a8f8..d2bcfbe 100644
--- a/arch/x86/include/asm/barrier.h
+++ b/arch/x86/include/asm/barrier.h
@@ -57,12 +57,12 @@
 do {									\
 	compiletime_assert_atomic_type(*p);				\
 	smp_mb();							\
-	ACCESS_ONCE(*p) = (v);						\
+	WRITE_ONCE(*p, v);						\
 } while (0)
 
 #define smp_load_acquire(p)						\
 ({									\
-	typeof(*p) ___p1 = ACCESS_ONCE(*p);				\
+	typeof(*p) ___p1 = READ_ONCE(*p);				\
 	compiletime_assert_atomic_type(*p);				\
 	smp_mb();							\
 	___p1;								\
@@ -74,12 +74,12 @@ do {									\
 do {									\
 	compiletime_assert_atomic_type(*p);				\
 	barrier();							\
-	ACCESS_ONCE(*p) = (v);						\
+	WRITE_ONCE(*p, v);						\
 } while (0)
 
 #define smp_load_acquire(p)						\
 ({									\
-	typeof(*p) ___p1 = ACCESS_ONCE(*p);				\
+	typeof(*p) ___p1 = READ_ONCE(*p);				\
 	compiletime_assert_atomic_type(*p);				\
 	barrier();							\
 	___p1;								\
-- 
2.5.0.rc2.392.g76e840b

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