linux-kernel - [PATCH 2/4] tools: include: remove ACCESS

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Date:   Mon, 27 Nov 2017 10:38:22 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     linux-kernel@...r.kernel.org, mingo@...hat.com
Cc:     acme@...hat.com, apw@...onical.com, joe@...ches.com,
        mark.rutland@....com, paulmck@...ux.vnet.ibm.com,
        peterz@...radead.org
Subject: [PATCH 2/4] tools: include: remove ACCESS_ONCE()

There are no longer any usersapce uses of ACCESS_ONCE(), so we can
remove the definition from our userspace <linux/compiler.h>, which is
only used by tools in the kernel directory (i.e. it isn't a uapi
header).

This patch removes the ACCESS_ONCE() definition, and updates comments
which referred to it. At the same time, some inconsistent and redundant
whitespace is removed from comments.

Signed-off-by: Mark Rutland <mark.rutland@....com>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Joe Perches <joe@...ches.com>
Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@...radead.org>
---
 tools/include/linux/compiler.h | 21 +++++++++------------
 1 file changed, 9 insertions(+), 12 deletions(-)

diff --git a/tools/include/linux/compiler.h b/tools/include/linux/compiler.h
index 07fd03c74a77..04e32f965ad7 100644
--- a/tools/include/linux/compiler.h
+++ b/tools/include/linux/compiler.h
@@ -84,8 +84,6 @@
 
 #define uninitialized_var(x) x = *(&(x))
 
-#define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))
-
 #include <linux/types.h>
 
 /*
@@ -135,20 +133,19 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
 /*
  * Prevent the compiler from merging or refetching reads or writes. The
  * compiler is also forbidden from reordering successive instances of
- * READ_ONCE, WRITE_ONCE and ACCESS_ONCE (see below), but only when the
- * compiler is aware of some particular ordering.  One way to make the
- * compiler aware of ordering is to put the two invocations of READ_ONCE,
- * WRITE_ONCE or ACCESS_ONCE() in different C statements.
+ * READ_ONCE and WRITE_ONCE, but only when the compiler is aware of some
+ * particular ordering. One way to make the compiler aware of ordering is to
+ * put the two invocations of READ_ONCE or WRITE_ONCE in different C
+ * statements.
  *
- * In contrast to ACCESS_ONCE these two macros will also work on aggregate
- * data types like structs or unions. If the size of the accessed data
- * type exceeds the word size of the machine (e.g., 32 bits or 64 bits)
- * READ_ONCE() and WRITE_ONCE()  will fall back to memcpy and print a
- * compile-time warning.
+ * These two macros will also work on aggregate data types like structs or
+ * unions. If the size of the accessed data type exceeds the word size of
+ * the machine (e.g., 32 bits or 64 bits) READ_ONCE() and WRITE_ONCE() will
+ * fall back to memcpy and print a compile-time warning.
  *
  * Their two major use cases are: (1) Mediating communication between
  * process-level code and irq/NMI handlers, all running on the same CPU,
- * and (2) Ensuring that the compiler does not  fold, spindle, or otherwise
+ * and (2) Ensuring that the compiler does not fold, spindle, or otherwise
  * mutilate accesses that either do not require ordering or that interact
  * with an explicit memory barrier or atomic instruction that provides the
  * required ordering.
-- 
2.11.0