linux-kernel - Re: lockdep oddity

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Date:	Tue, 5 Sep 2006 20:12:41 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Heiko Carstens <heiko.carstens@...ibm.com>
Cc:	Andrew Morton <akpm@...l.org>, linux-kernel@...r.kernel.org,
	Arjan van de Ven <arjan@...radead.org>,
	Daniel Walker <dwalker@...sta.com>,
	Hua Zhong <hzhong@...il.com>
Subject: Re: lockdep oddity


* Heiko Carstens <heiko.carstens@...ibm.com> wrote:

> The lock validator gives me this (latest -mm and 2.6.18-rc6):
> 
> ===================================== 
> [ BUG: bad unlock balance detected! ] 
> ------------------------------------- 
> swapper/0 is trying to release lock (resource_lock) at:
> [<0000000000042842>] request_resource+0x52/0x88 
> but there are no more locks to release! 
> 
> The reason is that the BUILD_LOCK_OPS macros in kernel/lockdep.c don't 
> contain any of the *_acquire calls, while all of the _unlock functions 
> contain a *_release call. Hence I get immediately unbalanced locks.

hmmm ... that sounds like a bug. Weird - i recently ran 
PREEMPT+SMP+LOCKDEP kernels and didnt notice this.

> Found this will debugging some random memory corruptions that happen 
> when CONFIG_PROVE_LOCKING and CONFIG_PROFILE_LIKELY are both on. 
> Switching both off or having only one of them on seems to work.

previously i had some weirdnesses with PROFILE_LIKELY too, they were 
caused by it generating cross-calls from within lockdep. Do the 
corruptions go away if you remove all likely() and unlikely() markings 
from kernel/lockdep.c?

	Ingo
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