Message-ID: <4D8F0A85.3050409@redhat.com>
Date: Sun, 27 Mar 2011 11:59:33 +0200
From: Avi Kivity <avi@redhat.com>
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To: Christoph Lameter <cl@linux.com>
CC: Pekka Enberg <penberg@kernel.org>, Ingo Molnar <mingo@elte.hu>,
        Eric Dumazet <eric.dumazet@gmail.com>, torvalds@linux-foundation.org,
        akpm@linux-foundation.org, tj@kernel.org, npiggin@kernel.dk,
        rientjes@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [GIT PULL] SLAB changes for v2.6.39-rc1
References: <alpine.DEB.2.00.1103241300420.32226@router.home> <AANLkTi=KZQd-GrXaq4472V3XnEGYqnCheYcgrdPFE0LJ@mail.gmail.com> <alpine.DEB.2.00.1103241312280.32226@router.home> <1300990853.3747.189.camel@edumazet-laptop> <alpine.DEB.2.00.1103241346060.32226@router.home> <AANLkTik3rkNvLG-rgiWxKaPc-v9sZQq96ok0CXfAU+r_@mail.gmail.com> <20110324185903.GA30510@elte.hu> <AANLkTi=66Q-8=AV3Y0K28jZbT3ddCHy9azWedoCC4Nrn@mail.gmail.com> <alpine.DEB.2.00.1103241404490.5576@router.home> <AANLkTimWYCHEsZjswLpD-xDcu_cL=GqsMshKRtkHt5Vn@mail.gmail.com> <20110324193647.GA7957@elte.hu> <AANLkTinBwKT3s=1En5Urs56gmt_zCNgPXnQzzy52Tgdo@mail.gmail.com> <alpine.DEB.2.00.1103241451060.5576@router.home>
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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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