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

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Date:	Mon, 9 Jul 2012 01:12:28 +0900
From:	JoonSoo Kim <js1304@...il.com>
To:	Fengguang Wu <fengguang.wu@...el.com>
Cc:	Vegard Nossum <vegard.nossum@...il.com>,
	Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...nel.org>,
	Linux Memory Management List <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: WARNING: __GFP_FS allocations with IRQs disabled (kmemcheck_alloc_shadow)

2012/7/8 Fengguang Wu <fengguang.wu@...el.com>:
> Hi Vegard,
>
> This warning code is triggered for the attached config:
>
> __lockdep_trace_alloc():
>         /*
>          * Oi! Can't be having __GFP_FS allocations with IRQs disabled.
>          */
>         if (DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags)))
>                 return;
>
> Where the irq is possibly disabled at the beginning of __slab_alloc():
>
>         local_irq_save(flags);

Currently, in slub code, kmemcheck_alloc_shadow is always invoked with
irq_disabled.
I think that something like below is needed.

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.
-- 
1.7.0.4
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