linux-kernel - Re: [Slub allocator] There are chances that kmem_cache_cpu->freelist gets lost if the process happens to be rescheduled to a differenet cpu before the local_irq_save() completes in __slab

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Date:	Mon, 12 Dec 2011 20:31:38 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Christoph Lameter <cl@...ux.com>
Cc:	zhihua che <zhihua.che@...il.com>, linux-kernel@...r.kernel.org,
	Pekka Enberg <penberg@...helsinki.fi>
Subject: Re: [Slub allocator] There are chances that
 kmem_cache_cpu->freelist gets lost if the process happens to be rescheduled
 to a differenet cpu before the local_irq_save() completes in __slab_alloc()

Le lundi 12 décembre 2011 à 12:53 -0600, Christoph Lameter a écrit :
> On Mon, 12 Dec 2011, Eric Dumazet wrote:
> 
> > Indeed, I reproduced the leak with hackbench and lot of threads.
> 
> Ran it here and did not see anything. But obviously this is an issue.
> Strange that no one noticed earlier. Usage of CONFIG_PREEMPT must not be
> that frequent.
> 

Yes, probably :(

All I did was using hackbench with 4000 threads on my 16 cpu machine,

while :; do hackbench 100 process 2000 ; done

I got about one leak (freelist chain, so several objects leaked) per
second.



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