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 09:50:02 -0600 (CST)
From:	Christoph Lameter <cl@...ux.com>
To:	Eric Dumazet <eric.dumazet@...il.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()

On Mon, 12 Dec 2011, Eric Dumazet wrote:

> We miss a deactivate_slab() call or just deliver object if c->freelist
> is not null (and NUMA node matches)
>
> Untested patch :
>
> diff --git a/mm/slub.c b/mm/slub.c
> index ed3334d..923d238 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -2166,6 +2166,12 @@ redo:
>  		goto new_slab;
>  	}
>
> +#ifdef CONFIG_PREEMPT
> +	object = c->freelist;
> +	if (object)
> +		goto load_freelist;
> +#endif
> +
>  	stat(s, ALLOC_SLOWPATH);
>
>  	do {

Correct. Issue was introduced in 2.6.39.

Acked-by: Christoph Lameter <cl@...ux.com>

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