From fbf692b26afc3523353edfa6c5faf2b5c2058815 Mon Sep 17 00:00:00 2001 From: Marco Elver Date: Thu, 21 May 2020 16:20:44 +0200 Subject: [PATCH] compiler.h: Remove data_race() and unnecessary checks from {READ,WRITE}_ONCE() The volatile accesses no longer need to be wrapped in data_race() because compilers that emit instrumentation distinguishing volatile accesses are required for KCSAN. Consequently, the explicit kcsan_check_atomic*() are no longer required either since the compiler emits instrumentation distinguishing the volatile accesses. Finally, simplify __READ_ONCE_SCALAR() and remove __WRITE_ONCE_SCALAR(). [ bp: Convert commit message to passive voice. ] Signed-off-by: Marco Elver Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Acked-by: Peter Zijlstra (Intel) Acked-by: Will Deacon Link: https://lkml.kernel.org/r/20200521142047.169334-9-elver@google.com --- include/linux/compiler.h | 13 ++----------- 1 file changed, 2 insertions(+), 11 deletions(-) diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 6d307c0aa4b4e..7b090d263fec6 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -281,9 +281,7 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val, #define __READ_ONCE_SCALAR(x) \ ({ \ - typeof(x) *__xp = &(x); \ - __unqual_scalar_typeof(x) __x = data_race(__READ_ONCE(*__xp)); \ - kcsan_check_atomic_read(__xp, sizeof(*__xp)); \ + __unqual_scalar_typeof(x) __x = __READ_ONCE(x); \ smp_read_barrier_depends(); \ (typeof(x))__x; \ }) @@ -299,17 +297,10 @@ do { \ *(volatile typeof(x) *)&(x) = (val); \ } while (0) -#define __WRITE_ONCE_SCALAR(x, val) \ -do { \ - typeof(x) *__xp = &(x); \ - kcsan_check_atomic_write(__xp, sizeof(*__xp)); \ - data_race(({ __WRITE_ONCE(*__xp, val); 0; })); \ -} while (0) - #define WRITE_ONCE(x, val) \ do { \ compiletime_assert_rwonce_type(x); \ - __WRITE_ONCE_SCALAR(x, val); \ + __WRITE_ONCE(x, val); \ } while (0) #ifdef CONFIG_KASAN -- 2.39.5