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Date: Fri, 11 Nov 2011 09:02:08 -0600 (CST)
From: Christoph Lameter <cl@linux.com>
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To: Shaohua Li <shaohua.li@intel.com>
cc: Julie Sullivan <kernelmail.jms@gmail.com>,
        Yong Zhang <yong.zhang0@gmail.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Pekka Enberg <penberg@kernel.org>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>
Subject: Re: INFO: possible recursive locking detected: get_partial_node()
 on 3.2-rc1
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On Fri, 11 Nov 2011, Shaohua Li wrote:

> Looks this could be a real dead lock. we hold a lock to free a object,
> but the free need allocate a new object. if the new object and the freed
> object are from the same slab, there is a deadlock.

unfreeze partials is never called when going through get_partial_node()
so there is no deadlock AFAICT.

> discard_slab() doesn't need hold the lock if the slab is already removed
> from partial list. how about below patch, only compile tested.

In general I think it is good to move the call to discard_slab() out from
under the list_lock in unfreeze_partials(). Could you fold
discard_page_list into unfreeze_partials()? __flush_cpu_slab still calls
discard_page_list with disabled interrupts even after your patch.