linux-kernel - Re: soft lockup when passing vvar address to write(2)

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Message-ID: <CALCETrX__AbsmV161tYVvVfSjeETTHoMLgpZYo+tQB+ewG8kPQ@mail.gmail.com>
Date:	Thu, 3 Mar 2016 16:17:51 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:	Andy Lutomirski <luto@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	X86 ML <x86@...nel.org>
Subject: Re: soft lockup when passing vvar address to write(2)

On Thu, Mar 3, 2016 at 2:58 PM, Rasmus Villemoes
<linux@...musvillemoes.dk> wrote:
> Looking up the vvar mapping and dumping its contents sometimes results
> in a soft lockup. On 4.5-rc6+ (master from earlier today) it seems to be
> a little harder to trigger than on the 4.2something Ubuntu kernel I
> first saw it on, but in both cases it's easy to reproduce (10s of
> iterations at most) by running the below program in a loop.
>

I can't reproduce this.  Do you have a .config or some other hint?

Can you also give me the contents of
/sys/devices/system/clocksource/clocksource0/current_clocksource and
the output from 'dmesg |grep -i hpet'?  And is this in a VM or on a
native boot?

My best guess is that you have a particularly buggy hpet.

--Andy