linux-kernel - Re: rcu self-detected stall messages on OMAP3, 4 boards

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Message-ID: <CAFTL4hy5wO9CL5_1e8U7L3Tihm_HYD6uAsda3ue-zDKFjir2Xg@mail.gmail.com>
Date:	Sat, 22 Sep 2012 17:45:12 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	paulmck@...ux.vnet.ibm.com
Cc:	Tony Lindgren <tony@...mide.com>, Paul Walmsley <paul@...an.com>,
	"Bruce, Becky" <bbruce@...com>,
	"Paul E. McKenney" <paul.mckenney@...aro.org>,
	"<linux-kernel@...r.kernel.org>" <linux-kernel@...r.kernel.org>,
	"<linux-omap@...r.kernel.org>" <linux-omap@...r.kernel.org>,
	"<linux-arm-kernel@...ts.infradead.org>" 
	<linux-arm-kernel@...ts.infradead.org>,
	"Hilman, Kevin" <khilman@...com>,
	"Shilimkar, Santosh" <santosh.shilimkar@...com>,
	"Hunter, Jon" <jon-hunter@...com>,
	"<snijsure@...d-net.com>" <snijsure@...d-net.com>
Subject: Re: rcu self-detected stall messages on OMAP3, 4 boards

2012/9/22 Paul E. McKenney <paulmck@...ux.vnet.ibm.com>:
> On Fri, Sep 21, 2012 at 01:31:49PM -0700, Tony Lindgren wrote:
>> * Paul E. McKenney <paulmck@...ux.vnet.ibm.com> [120921 12:58]:
>> >
>> > Just to make sure I understand the combinations:
>> >
>> > o   All stalls have happened when running a minimal userspace.
>> > o   CONFIG_NO_HZ=n suppresses the stalls.
>> > o   CONFIG_RCU_FAST_NO_HZ (which depends on CONFIG_NO_HZ=y) has
>> >     no observable effect on the stalls.
>>
>> The reason why you may need minimal userspace is to cut down
>> the number of timers waking up the system with NO_HZ.
>> Booting with init=/bin/sh might also do the trick for that.
>
> Good point!  This does make for a very quiet system, but does not
> reproduce the problem under kvm, even after waiting for four minutes.
> I will leave it for more time, but it looks like I really might need to
> ask Linaro for remote access to a Panda.

I have one. I'm currently installing Ubuntu on it and I'll try to
manage to build
a kernel and reproduce the issue.

I'll give more news soon.
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