linux-kernel - Re: Regression in gdm-2.18 since 2.6.24

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Message-ID: <20080408085027.GB13042@linux.vnet.ibm.com>
Date:	Tue, 8 Apr 2008 14:20:27 +0530
From:	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>
To:	Ken Moffat <zarniwhoop@...world.com>
Cc:	Ingo Molnar <mingo@...e.hu>, "Rafael J. Wysocki" <rjw@...k.pl>,
	lkml <linux-kernel@...r.kernel.org>, a.p.zijlstra@...llo.nl,
	aneesh.kumar@...ux.vnet.ibm.com, dhaval@...ux.vnet.ibm.com,
	Balbir Singh <balbir@...ibm.com>, skumar@...ux.vnet.ibm.com
Subject: Re: Regression in gdm-2.18 since 2.6.24

On Mon, Apr 07, 2008 at 12:48:33AM +0100, Ken Moffat wrote:
>  Well, I found your analysis convincing.  Unfortunately, my hardware
> disagreed.  Testing -rc8 with CONFIG_GROUP_SCHED disabled (a test is
> a mixture of 5 attempts to restart and 5 to shutdown):
> 
> 1. the base version success is 4/10
> 
> 2. increasing the granularity by a factor of 10 as you requested,
> success is 8/10

This makes me think that we are just exposing a timing related problem
in gdm here.

How abt a larger factor?

	# echo 200000000 > /proc/sys/kernel/sched_wakeup_granularity_ns

Does that make it 10/10 ?!

Anyway, it would be interesting to analyze the failure scenario more
(with help from gdm developers). Can you get some more debug data in this 
regard?

Before you shutdown,

	# strace -p <gdm-binary-pid1> 2>/tmp/gdmlog1 &
	# strace -p <gdm-binary-pid2> 2>/tmp/gdmlog2 &

Now shutdown and wait few minutes to confirm its not working. Send me
the strace log files ..Hopefully this will give a hint on what they are
deadlocked on (in the last log you sent, i can see both gdm-binaries in
sleep state ..whether that was a momentary state or whether they are 
actually deadlocked, will be confirmed by strace logs above).

>  If I was confused earlier, I guess I must be dazed and confused
> now!

me too!

Ingo/Peter, Any other suggestions you have?

-- 
Regards,
vatsa
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