linux-kernel - Re: [PATCH v5] slab/mempolicy: always use local policy from interrupt context

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Date:	Mon, 18 Jun 2012 04:20:54 -0400
From:	KOSAKI Motohiro <kosaki.motohiro@...il.com>
To:	David Mackey <tdmackey@...tter.com>
CC:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	rientjes@...gle.com, Andi Kleen <ak@...ux.intel.com>,
	penberg@...nel.org, cl@...ux.com, kosaki.motohiro@...il.com
Subject: Re: [PATCH v5] slab/mempolicy: always use local policy from interrupt
 context

(6/9/12 5:40 AM), David Mackey wrote:
> From: Andi Kleen<ak@...ux.intel.com>
> 
> From: Andi Kleen<ak@...ux.intel.com>
> 
> slab_node() could access current->mempolicy from interrupt context.
> However there's a race condition during exit where the mempolicy
> is first freed and then the pointer zeroed.
> 
> Using this from interrupts seems bogus anyways. The interrupt
> will interrupt a random process and therefore get a random
> mempolicy. Many times, this will be idle's, which noone can change.
> 
> Just disable this here and always use local for slab
> from interrupts. I also cleaned up the callers of slab_node a bit
> which always passed the same argument.
> 
> I believe the original mempolicy code did that in fact,
> so it's likely a regression.
> 
> v2: send version with correct logic
> v3: simplify. fix typo.
> Reported-by: Arun Sharma<asharma@...com>
> Cc: penberg@...nel.org
> Cc: cl@...ux.com
> Signed-off-by: Andi Kleen<ak@...ux.intel.com>
> [tdmackey@...tter.com: Rework control flow based on feedback from
> cl@...ux.com, fix logic, and cleanup current task_struct reference]
> Signed-off-by: David Mackey<tdmackey@...tter.com>

Acked-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>




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