[PATCH] staging: zcache: fix possible sleep under lock

Seth Jennings sjenning at linux.vnet.ibm.com
Mon Aug 22 19:49:45 UTC 2011


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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