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Date: Fri, 4 Aug 2006 12:24:57 -0700 (PDT)
From: Linus Torvalds <torvalds@osdl.org>
To: Michal Piotrowski <michal.k.k.piotrowski@gmail.com>
cc: Dave Jones <davej@codemonkey.org.uk>, LKML <linux-kernel@vger.kernel.org>
Subject: Re: 2.6.18-rc3-g3b445eea BUG: warning at
 /usr/src/linux-git/kernel/cpu.c:51/unlock_cpu_hotplug()
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On Fri, 4 Aug 2006, Michal Piotrowski wrote:
> 
> This was reported
> http://www.ussg.iu.edu/hypermail/linux/kernel/0607.3/1867.html
> http://www.ussg.iu.edu/hypermail/linux/kernel/0608.0/0675.html
> 
> It's time to use git-bisect.
> 
> BUG: warning at /usr/src/linux-git/kernel/cpu.c:51/unlock_cpu_hotplug()

Ok, that really is a pretty scary thing. The warning happens if the lock 
is released by somebody else than the person who took it. I don't _think_ 
that's supposed to happen, but with cpu hotplug locking being as 
"creative" as it is, maybe it's valid. 

I was planning on shutting the cpu hotplug warnings up for v2.6.18 - at 
least the "lukewarm IQ" one for _taking_ the lock recursively. But I had 
planned on leaving the unlock_cpu_hotplug() in place, since up until now 
it hadn't triggered, and it really smells like a bug if it does.

> [<c0132a04>] unlock_cpu_hotplug+0x2c/0x54
> [<c013a2ec>] stop_machine_run+0x2e/0x34
> [<c0135686>] sys_init_module+0x15a0/0x178a
> [<c015b7b7>] do_sync_read+0xb6/0xf1
> [<c0102d51>] sysenter_past_esp+0x56/0x79


DaveJ, any ideas?

		Linus
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