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Subject: Re: WARNING: at mm/slub.c:3357, kernel BUG at mm/slub.c:3413
From: Eric Dumazet <eric.dumazet@gmail.com>
To: Christoph Lameter <cl@linux.com>
Cc: Christian Kujau <lists@nerdbynature.de>,
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Date: Tue, 22 Nov 2011 08:48:33 +0100
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Le lundi 21 novembre 2011 à 21:18 -0600, Christoph Lameter a écrit :

> Hmmm... That means that c->page points to page not frozen. Per cpu
> partial pages are frozen until they are reused or until the partial list
> is flushed.
> 
> Does this ever happen on x86 or only on other platforms? In put_cpu_partial() the
> this_cpu_cmpxchg really needs really to be irq safe. this_cpu_cmpxchg is
> only preempt safe.
> 
> Index: linux-2.6/mm/slub.c
> ===================================================================
> --- linux-2.6.orig/mm/slub.c	2011-11-21 21:15:41.575673204 -0600
> +++ linux-2.6/mm/slub.c	2011-11-21 21:16:33.442336849 -0600
> @@ -1969,7 +1969,7 @@
>  		page->pobjects = pobjects;
>  		page->next = oldpage;
> 
> -	} while (this_cpu_cmpxchg(s->cpu_slab->partial, oldpage, page) != oldpage);
> +	} while (irqsafe_cpu_cmpxchg(s->cpu_slab->partial, oldpage, page) != oldpage);
>  	stat(s, CPU_PARTIAL_FREE);
>  	return pobjects;
>  }
> 

For x86, I wonder if our !X86_FEATURE_CX16 support is correct on SMP
machines.

this_cpu_cmpxchg16b_emu() claims to be IRQ safe, but may be buggy...

Could we have somewhere a NMI handler calling kmalloc() ?

Please Markus send us :

cat /proc/cpuinfo