linux-kernel - Re: WARNING: __GFP_FS allocations with IRQs disabled (kmemcheck_alloc

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Message-ID: <CAAmzW4PRYtsY33JTiOr496cj__PHJNZ5ZY5X+Co1FGYcebu8Ww@mail.gmail.com>
Date:	Mon, 9 Jul 2012 22:52:41 +0900
From:	JoonSoo Kim <js1304@...il.com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Fengguang Wu <fengguang.wu@...el.com>,
	Vegard Nossum <vegard.nossum@...il.com>,
	Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...nel.org>, Rus <rus@...nxsoft.com>,
	Ben Hutchings <ben@...adent.org.uk>,
	Steven Rostedt <rostedt@...dmis.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: WARNING: __GFP_FS allocations with IRQs disabled (kmemcheck_alloc_shadow)

2012/7/9 David Rientjes <rientjes@...gle.com>:
> On Mon, 9 Jul 2012, JoonSoo Kim wrote:
>
>> diff --git a/mm/slub.c b/mm/slub.c
>> index 8c691fa..5d41cad 100644
>> --- a/mm/slub.c
>> +++ b/mm/slub.c
>> @@ -1324,8 +1324,14 @@ static struct page *allocate_slab(struct
>> kmem_cache *s, gfp_t flags, int node)
>>                 && !(s->flags & (SLAB_NOTRACK | DEBUG_DEFAULT_FLAGS))) {
>>                 int pages = 1 << oo_order(oo);
>>
>> +               if (flags & __GFP_WAIT)
>> +                       local_irq_enable();
>> +
>>                 kmemcheck_alloc_shadow(page, oo_order(oo), flags, node);
>>
>> +               if (flags & __GFP_WAIT)
>> +                       local_irq_disable();
>> +
>>                 /*
>>                  * Objects from caches that have a constructor don't get
>>                  * cleared when they're allocated, so we need to do it here.
>
> This patch is suboptimal when the branch is taken since you just disabled
> irqs and now are immediately reenabling them and then disabling them
> again.  (And your patch is also whitespace damaged, has no changelog, and
> isn't signed off so it can't be applied.)

My intent is just to provide reference, because there is no replay to
this thread when I see it.


> The correct fix is what I proposed at
> http://marc.info/?l=linux-kernel&m=133754837703630 and was awaiting
> testing.  If Rus, Steven, or Fengguang could test this then we could add
> it as a stable backport as well.

Your patch looks good to me.
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