Date: Wed, 12 Dec 2007 11:40:13 -0500
From: Dave Jones <davej@redhat.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: linux-kernel@vger.kernel.org, "Rafael J. Wysocki" <rjw@sisk.pl>
Subject: Re: [crash] kernel BUG at drivers/cpufreq/cpufreq.c:1060!
Message-ID: <20071212164013.GA2359@redhat.com>
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	Ingo Molnar <mingo@elte.hu>, linux-kernel@vger.kernel.org,
	"Rafael J. Wysocki" <rjw@sisk.pl>
References: <20071212091144.GA11986@elte.hu>
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On Wed, Dec 12, 2007 at 10:11:44AM +0100, Ingo Molnar wrote:

 > 2.6.24-rc4-git5, got this cpufreq crash on x86 64-bit, during 'make 
 > randconfig' random bootup testing:

You hit all the fun bugs.

Just before we initialise cpufreqs notifier list..

 > Testing NMI watchdog ... <4>WARNING: CPU#0: NMI appears to be stuck (0->0)!

eek?

 > powernow-k8: Found 1 AMD Athlon(tm) 64 X2 Dual Core Processor 3800+ processors (1 cpu cores) (version 2.20.00)
 > powernow-k8: BIOS error - no PSB or ACPI _PSS objects
 > ------------[ cut here ]------------
 > kernel BUG at drivers/cpufreq/cpufreq.c:1060!

The actual BUG you hit is 

        if (unlikely(lock_policy_rwsem_write(cpu)))
                BUG();

It _looks_ like we're leaking a refcount on that lock, but
I don't see where.  It's a shame you can't reproduce this easily,
as cpufreq.debug=7 would give us more clues.
(And CONFIG_CPUFREQ_DEBUG=y)

I'll think about this some more.

	Dave

-- 
http://www.codemonkey.org.uk
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