From: Nick Desaulniers <ndesaulniers@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>,
Borislav Petkov <bp@alien8.de>
Subject: Re: [PATCH -tip v3 09/11] data_race: Avoid nested statement expression
Date: Thu, 21 May 2020 13:21:09 -0700 [thread overview]
Message-ID: <CAKwvOdnR7BXw_jYS5PFTuUamcwprEnZ358qhOxSu6wSSSJhxOA@mail.gmail.com> (raw)
In-Reply-To: <20200521142047.169334-10-elver@google.com>
On Thu, May 21, 2020 at 7:22 AM 'Marco Elver' via Clang Built Linux
<clang-built-linux@googlegroups.com> wrote:
>
> It appears that compilers have trouble with nested statement
> expressions. Therefore remove one level of statement expression nesting
> from the data_race() macro. This will help us avoid potential problems
> in future as its usage increases.
>
> Link: https://lkml.kernel.org/r/20200520221712.GA21166@zn.tnic
> Acked-by: Will Deacon <will@kernel.org>
> Signed-off-by: Marco Elver <elver@google.com>
Thanks Marco, I can confirm this series fixes the significant build
time regressions.
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
More measurements in: https://github.com/ClangBuiltLinux/linux/issues/1032
Might want:
Reported-by: Borislav Petkov <bp@suse.de>
Reported-by: Nathan Chancellor <natechancellor@gmail.com>
too.
> ---
> v3:
> * Fix for 'const' non-scalar expressions.
> v2:
> * Add patch to series in response to above linked discussion.
> ---
> include/linux/compiler.h | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/compiler.h b/include/linux/compiler.h
> index 7444f026eead..379a5077e9c6 100644
> --- a/include/linux/compiler.h
> +++ b/include/linux/compiler.h
> @@ -211,12 +211,12 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
> */
> #define data_race(expr) \
> ({ \
> - __kcsan_disable_current(); \
> - ({ \
> - __unqual_scalar_typeof(({ expr; })) __v = ({ expr; }); \
> - __kcsan_enable_current(); \
> - __v; \
> + __unqual_scalar_typeof(({ expr; })) __v = ({ \
> + __kcsan_disable_current(); \
> + expr; \
> }); \
> + __kcsan_enable_current(); \
> + __v; \
> })
>
> /*
> --
> 2.26.2.761.g0e0b3e54be-goog
>
> --
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--
Thanks,
~Nick Desaulniers
next prev parent reply other threads:[~2020-05-21 20:21 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 ` [PATCH -tip v3 08/11] READ_ONCE, WRITE_ONCE: Remove data_race() and unnecessary checks Marco Elver
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 [this message]
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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