From: Marco Elver <elver@google.com>
To: elver@google.com
Cc: paulmck@kernel.org, dvyukov@google.com, glider@google.com,
andreyknvl@google.com, kasan-dev@googlegroups.com,
linux-kernel@vger.kernel.org, tglx@linutronix.de,
mingo@kernel.org, peterz@infradead.org, will@kernel.org,
clang-built-linux@googlegroups.com, bp@alien8.de
Subject: [PATCH -tip v3 08/11] READ_ONCE, WRITE_ONCE: Remove data_race() and unnecessary checks
Date: Thu, 21 May 2020 16:20:44 +0200 [thread overview]
Message-ID: <20200521142047.169334-9-elver@google.com> (raw)
In-Reply-To: <20200521142047.169334-1-elver@google.com>
The volatile accesses no longer need to be wrapped in data_race(),
because we require compilers that emit instrumentation distinguishing
volatile accesses. Consequently, we also no longer require the explicit
kcsan_check_atomic*(), since the compiler emits instrumentation
distinguishing the volatile accesses. Finally, simplify
__READ_ONCE_SCALAR and remove __WRITE_ONCE_SCALAR.
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Marco Elver <elver@google.com>
---
v2:
* Remove unnecessary kcsan_check_atomic*() in *_ONCE.
* Simplify __READ_ONCE_SCALAR and remove __WRITE_ONCE_SCALAR. This
effectively restores Will Deacon's pre-KCSAN version:
https://git.kernel.org/pub/scm/linux/kernel/git/will/linux.git/tree/include/linux/compiler.h?h=rwonce/cleanup#n202
---
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 17c98b215572..7444f026eead 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -228,9 +228,7 @@ 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; \
})
@@ -246,17 +244,10 @@ 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
--
2.26.2.761.g0e0b3e54be-goog
next prev parent reply other threads:[~2020-05-21 14:22 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-21 14:20 [PATCH -tip v3 00/11] Fix KCSAN for new ONCE (require Clang 11) Marco Elver
2020-05-21 14:20 ` [PATCH -tip v3 01/11] ubsan, kcsan: don't combine sanitizer with kcov on clang Marco Elver
2020-05-21 14:20 ` [PATCH -tip v3 02/11] kcsan: Avoid inserting __tsan_func_entry/exit if possible Marco Elver
2020-05-22 16:08 ` [tip: locking/kcsan] " tip-bot2 for Marco Elver
2020-05-21 14:20 ` [PATCH -tip v3 03/11] kcsan: Support distinguishing volatile accesses Marco Elver
2020-05-22 10:26 ` Borislav Petkov
2020-05-22 10:34 ` Marco Elver
2020-05-22 10:47 ` Borislav Petkov
2020-05-22 16:08 ` [tip: locking/kcsan] " tip-bot2 for Marco Elver
2020-05-21 14:20 ` [PATCH -tip v3 04/11] kcsan: Pass option tsan-instrument-read-before-write to Clang Marco Elver
2020-05-22 16:08 ` [tip: locking/kcsan] " tip-bot2 for Marco Elver
2020-05-21 14:20 ` [PATCH -tip v3 05/11] kcsan: Remove 'noinline' from __no_kcsan_or_inline Marco Elver
2020-05-29 17:07 ` Peter Zijlstra
2020-05-29 18:36 ` Marco Elver
2020-05-29 18:59 ` Peter Zijlstra
2020-05-21 14:20 ` [PATCH -tip v3 06/11] kcsan: Restrict supported compilers Marco Elver
2020-05-21 14:20 ` [PATCH -tip v3 07/11] kcsan: Update Documentation to change " Marco Elver
2020-05-22 16:08 ` [tip: locking/kcsan] " tip-bot2 for Marco Elver
2020-05-21 14:20 ` Marco Elver [this message]
2020-05-22 16:08 ` [tip: locking/kcsan] compiler.h: Remove data_race() and unnecessary checks from {READ,WRITE}_ONCE() tip-bot2 for Marco Elver
2020-05-21 14:20 ` [PATCH -tip v3 09/11] data_race: Avoid nested statement expression Marco Elver
2020-05-21 20:21 ` Nick Desaulniers
2020-05-26 10:42 ` Arnd Bergmann
2020-05-26 12:02 ` Will Deacon
2020-05-26 12:19 ` Arnd Bergmann
2020-05-26 13:12 ` Marco Elver
2020-05-26 17:33 ` Marco Elver
2020-05-26 19:00 ` Arnd Bergmann
2020-05-26 23:10 ` Arnd Bergmann
2020-05-27 7:22 ` Will Deacon
2020-05-27 7:44 ` Marco Elver
2020-05-27 9:26 ` Arnd Bergmann
2020-05-28 12:53 ` Stephen Rothwell
2020-05-26 21:36 ` Peter Zijlstra
2020-05-21 14:20 ` [PATCH -tip v3 10/11] compiler.h: Move function attributes to compiler_types.h Marco Elver
2020-05-22 16:08 ` [tip: locking/kcsan] " tip-bot2 for Marco Elver
2020-05-21 14:20 ` [PATCH -tip v3 11/11] compiler_types.h, kasan: Use __SANITIZE_ADDRESS__ instead of CONFIG_KASAN to decide inlining Marco Elver
2020-05-22 16:08 ` [tip: locking/kcsan] " tip-bot2 for Marco Elver
2020-05-22 11:35 ` [PATCH -tip v3 00/11] Fix KCSAN for new ONCE (require Clang 11) Peter Zijlstra
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