From: Will Deacon <will@kernel.org>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Nick Desaulniers <ndesaulniers@google.com>,
Marco Elver <elver@google.com>,
"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>,
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: Tue, 26 May 2020 13:02:46 +0100 [thread overview]
Message-ID: <20200526120245.GB27166@willie-the-truck> (raw)
In-Reply-To: <CAK8P3a0RJtbVi1JMsfik=jkHCNFv+DJn_FeDg-YLW+ueQW3tNg@mail.gmail.com>
On Tue, May 26, 2020 at 12:42:16PM +0200, Arnd Bergmann wrote:
> On Thu, May 21, 2020 at 10:21 PM 'Nick Desaulniers' via Clang Built
> Linux <clang-built-linux@googlegroups.com> wrote:
> >
> > 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.
>
> I find this patch only solves half the problem: it's much faster than
> without the
> patch, but still much slower than the current mainline version. As far as I'm
> concerned, I think the build speed regression compared to mainline is not yet
> acceptable, and we should try harder.
>
> I have not looked too deeply at it yet, but this is what I found from looking
> at a file in a randconfig build:
>
> Configuration: see https://pastebin.com/raw/R9erCwNj
So this .config actually has KCSAN enabled. Do you still see the slowdown
with that disabled? Although not ideal, having a longer compiler time when
the compiler is being asked to perform instrumentation doesn't seem like a
show-stopper to me.
Will
next prev parent reply other threads:[~2020-05-26 12:02 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
2020-05-26 10:42 ` Arnd Bergmann
2020-05-26 12:02 ` Will Deacon [this message]
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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