linux-kernel - Re: lockdep and debug objects together are broken?

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Message-ID: <19f34abd0901201311t2425056dia6182812f7270297@mail.gmail.com>
Date:	Tue, 20 Jan 2009 22:11:47 +0100
From:	"Vegard Nossum" <vegard.nossum@...il.com>
To:	"Nick Piggin" <npiggin@...e.de>
Cc:	"Ingo Molnar" <mingo@...e.hu>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"Peter Zijlstra" <a.p.zijlstra@...llo.nl>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>
Subject: Re: lockdep and debug objects together are broken?

On Tue, Jan 20, 2009 at 9:55 AM, Nick Piggin <npiggin@...e.de> wrote:
> Hi,
>
> I've had a problem frustrating my testing because lockdep was silently turning
> itself off... I patched out the code to disable lockdep after the first error,
> and it started showing up weird errors. kernel/fork.c:990 seemed to be the
> first to trigger (hard irqs disabled) from a call_usermodehelper call. Later,
> migration thread was reported to try to unlock rq->lock although it was
> holding no locks. Then init was reported to return to userspace without
> releasing an objectdebug hash lock.
>
> All that went away and everything seemed to work properly with debug objects
> configured out.
>
> I didn't get too far in trying to debug the problem. But it should be easy
> enough to reproduce (if not, I can post traces or test patches).

I just built a kernel with lockdep and debugobjects enabled, and
everything seemed fine. I think you should post your kernel version,
config, and the lockdep patch (if needed -- it didn't seem to turn
itself off here).


Vegard

-- 
"The animistic metaphor of the bug that maliciously sneaked in while
the programmer was not looking is intellectually dishonest as it
disguises that the error is the programmer's own creation."
	-- E. W. Dijkstra, EWD1036
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