linux-kernel - Re: [PATCH] [4/4] SLAB: Fix node add timer race in cache

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Message-ID: <alpine.DEB.2.00.1002242357450.26099@chino.kir.corp.google.com>
Date:	Thu, 25 Feb 2010 00:01:30 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Pekka Enberg <penberg@...helsinki.fi>
cc:	Christoph Lameter <cl@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>,
	Nick Piggin <npiggin@...e.de>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, haicheng.li@...el.com
Subject: Re: [PATCH] [4/4] SLAB: Fix node add timer race in cache_reap

On Thu, 25 Feb 2010, Pekka Enberg wrote:

> > > > > I'm just worried there is still an underlying problem here.
> > > > So am I. What caused the breakage that requires this patchset?
> > > Memory hotadd with a new node being onlined.
> > 
> > That used to work fine.
> 
> OK, can we get this issue resolved? The merge window is open and Christoph
> seems to be unhappy with the whole patch queue. I'd hate this bug fix to miss
> .34...
> 

I don't see how memory hotadd with a new node being onlined could have 
worked fine before since slab lacked any memory hotplug notifier until 
Andi just added it.

That said, I think the first and fourth patch in this series may be 
unnecessary if slab's notifier were to call slab_node_prepare() on 
MEM_GOING_ONLINE instead of MEM_ONLINE.  Otherwise, kswapd is already 
running, the zonelists for the new pgdat have been initialized, and the 
bit has been set in node_states[N_HIGH_MEMORY] without allocated 
cachep->nodelists[node] memory.
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