From 2a22f692bbe0a7933acbd50045479ffc0fdf11f7 Mon Sep 17 00:00:00 2001 From: Mark Rutland Date: Mon, 27 Nov 2017 10:38:22 +0000 Subject: [PATCH] tools/include: Remove ACCESS_ONCE() There are no longer any usersapce uses of ACCESS_ONCE(), so we can remove the definition from our userspace , 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. Tested-by: Paul E. McKenney Signed-off-by: Mark Rutland Cc: Arnaldo Carvalho de Melo Cc: Joe Perches Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: apw@canonical.com Link: http://lkml.kernel.org/r/20171127103824.36526-3-mark.rutland@arm.com Signed-off-by: Ingo Molnar --- 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 /* @@ -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. -- GitLab