Re: [GIT PULL] SLAB changes for v2.6.39-rc1

[Eric Dumazet]

Le jeudi 24 mars 2011 Ã 14:51 -0500, Christoph Lameter a Ãcrit :
> 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.
> 
> 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.
> 


Thats strange, alloc_percpu() is supposed to zero the memory already ...

Are you sure its really this problem of interrupts being disabled ?



--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/