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SubjectRe: [GIT PULL] SLAB changes for v2.6.39-rc1
On 03/24/2011 09:51 PM, Christoph Lameter wrote:
> On Thu, 24 Mar 2011, Pekka Enberg wrote:
>
> > Thanks, Ingo! Christoph, may I have your sign-off for the patch and
> > I'll send it to Linus?
>
>
> Subject: SLUB: Write to per cpu data when allocating it
>
> It turns out that the cmpxchg16b emulation has to access vmalloced
> percpu memory with interrupts disabled. If the memory has never
> been touched before then the fault necessary to establish the
> mapping will not to occur and the kernel will fail on boot.
>

I don't get it. Disabling interrupts doesn't disable faults.

> Fix that by reusing the CONFIG_PREEMPT code that writes the
> cpu number into a field on every cpu. Writing to the per cpu
> area before causes the mapping to be established before we get
> to a cmpxchg16b emulation.
>
> Tested-by: Ingo Molnar<mingo@elte.hu>
> Signed-off-by: Christoph Lameter<cl@linux.com>
>
> ---
> mm/slub.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> Index: linux-2.6/mm/slub.c
> ===================================================================
> --- linux-2.6.orig/mm/slub.c 2011-03-24 14:03:10.000000000 -0500
> +++ linux-2.6/mm/slub.c 2011-03-24 14:04:08.000000000 -0500
> @@ -1604,7 +1604,7 @@ static inline void note_cmpxchg_failure(
>
> void init_kmem_cache_cpus(struct kmem_cache *s)
> {
> -#if defined(CONFIG_CMPXCHG_LOCAL)&& defined(CONFIG_PREEMPT)
> +#ifdef CONFIG_CMPXCHG_LOCAL
> int cpu;
>
> for_each_possible_cpu(cpu)
> --
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--
error compiling committee.c: too many arguments to function



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