linux-kernel - Re: [PATCH] staging: zcache: fix possible sleep under lock

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Message-ID: <4E52B2D9.5070904@linux.vnet.ibm.com>
Date:	Mon, 22 Aug 2011 14:49:45 -0500
From:	Seth Jennings <sjenning@...ux.vnet.ibm.com>
To:	Dan Carpenter <error27@...il.com>
CC:	gregkh@...e.de, devel@...verdev.osuosl.org,
	dan.magenheimer@...cle.com, ascardo@...oscopio.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: zcache: fix possible sleep under lock

On 08/22/2011 02:09 PM, Dan Carpenter wrote:
> On Mon, Aug 22, 2011 at 01:47:49PM -0500, Seth Jennings wrote:
>> zcache_new_pool() calls kmalloc() with GFP_KERNEL which has
>> __GFP_WAIT set.  However, zcache_new_pool() gets called on
>> a stack that holds the swap_lock spinlock, leading to a
>> possible sleep-with-lock situation. The lock is obtained
>> in enable_swap_info().
>>
>> The patch replaces GFP_KERNEL with GFP_IOFS, which is
>> GFP_KERNEL & ~__GFP_WAIT.
>>
> 
> You should use GFP_ATOMIC.  We don't want to do IO with the locks
> held.  The only reason GFP_IOFS exists is so that we can turn off
> io during suspend and resume.
> 
> regards,
> dan carpenter
> 
Actually, should this be GFP_ATOMIC or GFP_NOWAIT?

--
Seth
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