linux-kernel - Re: INFO: possible recursive locking detected: get_partial

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

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.



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