linux-kernel - [PATCH 2/2] compiler: Prevent evaluation of WRITE

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Date:   Fri, 24 May 2019 12:35:36 +0200
From:   Andrea Parri <andrea.parri@...rulasolutions.com>
To:     linux-kernel@...r.kernel.org
Cc:     Andrea Parri <andrea.parri@...rulasolutions.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jorgen Hansen <jhansen@...are.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>,
        "Paul E. McKenney" <paulmck@...ux.ibm.com>
Subject: [PATCH 2/2] compiler: Prevent evaluation of WRITE_ONCE()

Now that there's no single use of the value of WRITE_ONCE(), change
the implementation to eliminate it.

Suggested-by: Mark Rutland <mark.rutland@....com>
Signed-off-by: Andrea Parri <andrea.parri@...rulasolutions.com>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Jorgen Hansen <jhansen@...are.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Will Deacon <will.deacon@....com>
Cc: Mark Rutland <mark.rutland@....com>
Cc: "Paul E. McKenney" <paulmck@...ux.ibm.com>
---
 include/linux/compiler.h | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 8aaf7cd026b06..4024c809a6c63 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -277,12 +277,11 @@ unsigned long read_word_at_a_time(const void *addr)
 }
 
 #define WRITE_ONCE(x, val) \
-({							\
+do {							\
 	union { typeof(x) __val; char __c[1]; } __u =	\
 		{ .__val = (__force typeof(x)) (val) }; \
 	__write_once_size(&(x), __u.__c, sizeof(x));	\
-	__u.__val;					\
-})
+} while (0)
 
 #endif /* __KERNEL__ */
 
-- 
2.7.4