linux-kernel - Re: [Bug #10815] 2.6.26-rc4: RIP find_pid

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Message-ID: <20080616033126.GF17915@linux.vnet.ibm.com>
Date:	Sun, 15 Jun 2008 20:31:26 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Alexey Dobriyan <adobriyan@...il.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Oleg Nesterov <oleg@...sign.ru>, Adrian Bunk <bunk@...nel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [Bug #10815] 2.6.26-rc4: RIP find_pid_ns+0x6b/0xa0

On Mon, Jun 16, 2008 at 07:01:54AM +0400, Alexey Dobriyan wrote:
> On Sun, Jun 15, 2008 at 04:38:24PM -0700, Linus Torvalds wrote:
> > On Sun, 15 Jun 2008, Paul E. McKenney wrote:
> > >
> > > If that is the right thing to do.  I would feel better about it if I
> > > could reproduce the failure.
> > 
> > Is there some configuration thing that might make it happen for Alexey but 
> > not for you? The only obvious one is the normal PREEMPT thing, but 
> > PREEMPT_RCU obviously depends on that, so there must be something else.
> > 
> > CONFIG_SMP? CONFIG_NO_HZ? CONFIG_[RT|FAIR]_GROUP_SCHED? There's a number 
> > of config options that change scheduling details..
> 
> The only way I can "fix" rcutorture here is SMP=n (not maxcpus=1!).

I am running SMP=y without seeing the problem.

> Among things tried and do not matter are NO_HZ, HIGH_RES_TIMERS, turning off
> debugging options (one by one and in bulk), DEBUG_PER_CPU_MAPS, HZ tweaks,
> SCHED_MC.
> 
> All of this doesn't help, but SMP=n does.

Attached is the compressed config file I used for a run on a POWER
machine.  I have used similar config files for x86.  For this run, I built
LTP, installed it, started rcutorture, ran LTP, then ended rcutorture.

The only other thing I can think of is that Alexey's machines are
somehow managing to nest NMIs or something.  I can produce a fix for
that, but have no way of testing it.

Thoughts?

							Thanx, Paul

Download attachment "dotconfig.bz2" of type "application/octet-stream" (9027 bytes)