linux-kernel - Re: frequent lockups in 3.18rc4

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Message-ID: <20141201171036.GH18466@arm.com>
Date:	Mon, 1 Dec 2014 17:10:37 +0000
From:	Will Deacon <will.deacon@....com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Dave Jones <davej@...hat.com>,
	Andy Lutomirski <luto@...capital.net>,
	Don Zickus <dzickus@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	the arch/x86 maintainers <x86@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: frequent lockups in 3.18rc4

On Mon, Dec 01, 2014 at 05:05:06PM +0000, Linus Torvalds wrote:
> On Mon, Dec 1, 2014 at 3:48 AM, Will Deacon <will.deacon@....com> wrote:
> > so for some bizarre reason, child1 (27912) managed to execve oom_score
> > from /proc.
> 
> That sounds like you have a binfmt that accepts crap. Possibly
> ARM-specific, although more likely it's just a misc script.
> 
> > We can see the child that did the execve has somehow gained its own
> > child process (27921) that we're unable to backtrace. I can't see any
> > clone/fork syscalls in the log for 27912.
> 
> Well, it wouldn't be trinity any more, it would likely be some execve
> script (think "/bin/sh", except likely through binfmt_misc).
> 
> Do you have anything in /proc/sys/fs/binfmt_misc? I don't see anything
> else that would trigger it.

So I don't even have binfmt-misc compiled in. The two handlers I have are
BINFMT_ELF and BINFMT_SCRIPT, but they both check for headers that we won't
get back from oom_score afaict.

> This doesn't really look anything like DaveJ's issue, but who knows..

It's the only lockup I'm seeing on arm64 with trinity, but I agree that it's
not very helpful.

Will
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