From: Andi Kleen <ak@linux.intel.com>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: Florian Weimer <fweimer@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
LKML <linux-kernel@vger.kernel.org>,
Andi Kleen <andi@firstfloor.org>,
linux-toolchains@vger.kernel.org
Subject: Re: [PATCH] sched: Work around undefined behavior in sched class checking
Date: Wed, 5 May 2021 09:48:58 -0700 [thread overview]
Message-ID: <a4d64648-6726-2046-0883-ac7f20c70445@linux.intel.com> (raw)
In-Reply-To: <CAKwvOdneTkwm1xmte2SxwR=pcp3vi320kQuQHtVNVbnqLbcP3Q@mail.gmail.com>
On 5/5/2021 9:41 AM, Nick Desaulniers wrote:
> On Wed, May 5, 2021 at 7:39 AM Andi Kleen <ak@linux.intel.com> wrote:
>>> Would you please provide a
>>> minimal test case?
>> You can only reproduce it with a LTO build because it needs knowledge
>> between different translation units for this specific case.
>>
>> But gcc will totally do the optimization even without LTO if it can
>> prove the same inside a single TU.
> It would be helpful to isolate a test case that doesn't rely on LTO,
> if possible.
Like I wrote earlier we used to see it all the time in __pa_symbol
before it used RELOC_HIDE. I bet if you make RELOC_HIDE a nop you'll see
multiple instances.
But not sure why you want a test case?
-Andi
next prev parent reply other threads:[~2021-05-05 17:00 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-05 3:39 [PATCH] sched: Work around undefined behavior in sched class checking Andi Kleen
2021-05-05 6:46 ` Peter Zijlstra
2021-05-05 8:47 ` Florian Weimer
2021-05-05 9:04 ` Peter Zijlstra
2021-05-05 14:39 ` Andi Kleen
2021-05-05 16:41 ` Nick Desaulniers
2021-05-05 16:48 ` Andi Kleen [this message]
2021-05-05 17:08 ` Nick Desaulniers
2021-05-05 17:20 ` Andi Kleen
2021-05-05 14:34 ` Andi Kleen
2021-05-05 15:34 ` Peter Zijlstra
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