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Date: Thu, 14 Jul 2011 09:57:51 -0700
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
        Steven Rostedt <rostedt@goodmis.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Dipankar Sarma <dipankar@in.ibm.com>, linux-kernel@vger.kernel.org
Subject: Re: INFO: possible circular locking dependency detected
Message-ID: <20110714165751.GA7400@linux.vnet.ibm.com>
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References: <20110714144946.GA3354@swordfish.minsk.epam.com>
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On Thu, Jul 14, 2011 at 06:41:39PM +0200, Peter Zijlstra wrote:
> On Thu, 2011-07-14 at 17:49 +0300, Sergey Senozhatsky wrote:
> > Hello,
> > 
> > [ 4172.371094] =======================================================
> > [ 4172.371097] [ INFO: possible circular locking dependency detected ]
> > [ 4172.371103] 3.0.0-rc7-dbg-00565-g6b31efc #644
> > [ 4172.371105] -------------------------------------------------------
> > [ 4172.371108] make/11702 is trying to acquire lock:
> > [ 4172.371111]  (rcu_node_level_0){..-...}, at: [<ffffffff810a55e2>] __rcu_read_unlock+0xb9/0x217
> > [ 4172.371123] 
> > [ 4172.371123] but task is already holding lock:
> > [ 4172.371125]  (&p->pi_lock){-.-.-.}, at: [<ffffffff8103775e>] try_to_wake_up+0x29/0x28b
> > [ 4172.371135] 
> > [ 4172.371135] which lock already depends on the new lock.
> 
> Happen to have a .config and means of reproduction? We're a little
> stumped at trying to explain how this can actually happen.

What Peter said!  Sergey, could also you please tell us what tree you
are using?  I am not seeing commit 6b31efc in mainline or -tip.

							Thanx, Paul