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From: Sergei Trofimovich <slyich@gmail.com>
To: libc-alpha@sourceware.org, linux-kernel@vger.kernel.org, x86@kernel.org
Cc: "H.J. Lu" <hjl.tools@gmail.com>
Subject: Re: x86_64: movdqu rarely stores bad data (movdqu works fine). Kernel bug, fried CPU or glibc bug?
Date: Sun, 17 Jun 2018 21:39:00 -0000	[thread overview]
Message-ID: <20180617223941.3e1e4973@sf> (raw)
In-Reply-To: <20180616222250.618cecaa@sf>

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On Sat, 16 Jun 2018 22:22:50 +0100
Sergei Trofimovich <slyich@gmail.com> wrote:

> TL;DR: on master string/test-memmove glibc test fails on my machine
> and I don't know why. Other tests work fine.
> ...
> This fails:
>   loop {
>     movdqu [src++],%xmm0
>     movntdq %xmm0,[dst++]
>   }
>   sfence
> This works:
>   loop {
>     movdqu [src++],%xmm0
>     movdqu %xmm0,[dst++]
>   }
>   sfence
> ...
> If there is no obvious problems with glibc's memove() or my small test
> what can I do to rule-out/pin-down hardware or kernel problem?

Found the cause: bad RAM module.

After I've tweaked test to allocate most of available physical RAM
I've got fully reproducible failure.

I unplugged RAM modules one by one and ran the test. That way I've
nailed down to one bad chip. Removing single bad chip restored
string/test-memmove test on this machine \o/

Sorry for the noise!

-- 

  Sergei

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      reply	other threads:[~2018-06-17 21:39 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-06-16 21:23 Sergei Trofimovich
2018-06-17 21:39 ` Sergei Trofimovich [this message]

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