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From: Marco Elver <elver@google.com>
To: Marco Elver <elver@google.com>
Cc: "Paul E. McKenney" <paulmck@kernel.org>,
	Dmitry Vyukov <dvyukov@google.com>,
	Alexander Potapenko <glider@google.com>,
	Andrey Konovalov <andreyknvl@google.com>,
	kasan-dev <kasan-dev@googlegroups.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Will Deacon <will@kernel.org>,
	clang-built-linux <clang-built-linux@googlegroups.com>
Subject: Re: [PATCH -tip 08/10] READ_ONCE, WRITE_ONCE: Remove data_race() wrapping
Date: Thu, 21 May 2020 11:47:54 +0200	[thread overview]
Message-ID: <CANpmjNNdBrO=dJ1gL+y0w2zBFdB7G1E9g4uk7oDDEt_X9FaRVA@mail.gmail.com> (raw)
In-Reply-To: <20200515150338.190344-9-elver@google.com>

On Fri, 15 May 2020 at 17:04, Marco Elver <elver@google.com> wrote:
>
> The volatile access no longer needs to be wrapped in data_race(),
> because we require compilers that emit instrumentation distinguishing
> volatile accesses.
>
> Signed-off-by: Marco Elver <elver@google.com>
> ---
>  include/linux/compiler.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/compiler.h b/include/linux/compiler.h
> index 17c98b215572..fce56402c082 100644
> --- a/include/linux/compiler.h
> +++ b/include/linux/compiler.h
> @@ -229,7 +229,7 @@ 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));  \
> +       __unqual_scalar_typeof(x) __x = __READ_ONCE(*__xp);             \
>         kcsan_check_atomic_read(__xp, sizeof(*__xp));                   \

Some self-review: We don't need kcsan_check_atomic anymore, and this
should be removed.

I'll send v2 to address this (together with fix to data_race()
removing nested statement expressions).

>         smp_read_barrier_depends();                                     \
>         (typeof(x))__x;                                                 \
> @@ -250,7 +250,7 @@ do {                                                                        \
>  do {                                                                   \
>         typeof(x) *__xp = &(x);                                         \
>         kcsan_check_atomic_write(__xp, sizeof(*__xp));                  \

Same.

> -       data_race(({ __WRITE_ONCE(*__xp, val); 0; }));                  \
> +       __WRITE_ONCE(*__xp, val);                                       \
>  } while (0)
>
>  #define WRITE_ONCE(x, val)                                             \
> --
> 2.26.2.761.g0e0b3e54be-goog
>

  reply	other threads:[~2020-05-21  9:48 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-15 15:03 [PATCH -tip 00/10] Fix KCSAN for new ONCE (require Clang 11) Marco Elver
2020-05-15 15:03 ` [PATCH -tip 01/10] ubsan, kcsan: don't combine sanitizer with kcov on clang Marco Elver
2020-05-15 15:03 ` [PATCH -tip 02/10] kcsan: Avoid inserting __tsan_func_entry/exit if possible Marco Elver
2020-05-15 15:03 ` [PATCH -tip 03/10] kcsan: Support distinguishing volatile accesses Marco Elver
2020-05-15 15:03 ` [PATCH -tip 04/10] kcsan: Pass option tsan-instrument-read-before-write to Clang Marco Elver
2020-05-15 15:03 ` [PATCH -tip 05/10] kcsan: Remove 'noinline' from __no_kcsan_or_inline Marco Elver
2020-05-15 15:03 ` [PATCH -tip 06/10] kcsan: Restrict supported compilers Marco Elver
2020-05-15 15:03 ` [PATCH -tip 07/10] kcsan: Update Documentation to change " Marco Elver
2020-05-15 15:03 ` [PATCH -tip 08/10] READ_ONCE, WRITE_ONCE: Remove data_race() wrapping Marco Elver
2020-05-21  9:47   ` Marco Elver [this message]
2020-05-21 10:18     ` Marco Elver
2020-05-21 10:22       ` Will Deacon
2020-05-15 15:03 ` [PATCH -tip 09/10] compiler.h: Move function attributes to compiler_types.h Marco Elver
2020-05-15 15:03 ` [PATCH -tip 10/10] compiler_types.h, kasan: Use __SANITIZE_ADDRESS__ instead of CONFIG_KASAN to decide inlining Marco Elver
2020-05-21 11:11 ` [PATCH -tip 00/10] Fix KCSAN for new ONCE (require Clang 11) Marco Elver

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