linux-kernel - [PATCH v4 22/27] compiler: Simple READ/WRITE

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Date:   Fri, 21 Feb 2020 14:34:38 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        rostedt@...dmis.org
Cc:     peterz@...radead.org, mingo@...nel.org, joel@...lfernandes.org,
        gregkh@...uxfoundation.org, gustavo@...eddedor.com,
        tglx@...utronix.de, paulmck@...nel.org, josh@...htriplett.org,
        mathieu.desnoyers@...icios.com, jiangshanlai@...il.com,
        luto@...nel.org, tony.luck@...el.com, frederic@...nel.org,
        dan.carpenter@...cle.com, mhiramat@...nel.org
Subject: [PATCH v4 22/27] compiler: Simple READ/WRITE_ONCE() implementations

Because I need WRITE_ONCE_NOCHECK() and in anticipation of Will's
READ_ONCE rewrite, provide __{READ,WRITE}_ONCE_SCALAR().

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 include/linux/compiler.h |    8 ++++++++
 1 file changed, 8 insertions(+)

--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -289,6 +289,14 @@ unsigned long read_word_at_a_time(const
 	__u.__val;					\
 })
 
+#define __READ_ONCE_SCALAR(x)			\
+	(*(const volatile typeof(x) *)&(x))
+
+#define __WRITE_ONCE_SCALAR(x, val)		\
+do {						\
+	*(volatile typeof(x) *)&(x) = val;	\
+} while (0)
+
 #endif /* __KERNEL__ */
 
 /*