linux-kernel - Re: DEBUG_PAGEALLOC + order-10 alloc/free

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Date:	Fri, 26 Dec 2008 10:55:23 +0100
From:	Arjan van de Ven <arjan@...ux.intel.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Tony Battersby <tonyb@...ernetics.com>,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	venkatesh.pallipadi@...el.com, jeremy@...p.org
Subject: Re: DEBUG_PAGEALLOC + order-10 alloc/free_pages = lockup

Ingo Molnar wrote:
> * Tony Battersby <tonyb@...ernetics.com> wrote:
> 
>> An order-10 alloc_pages followed by free_pages with DEBUG_PAGEALLOC
>> causes a lockup during subsequent memory allocations.  Order-9 and lower
>> do not trigger the problem.  This problem was introduced in 2.6.25-rc1
>> and fixed in 2.6.28-rc1.  Even though the bug is now fixed, I am
>> reporting it because:
>>
>> 1) I am not sure that anyone ever realized that the bug existed.
> 
> Correct.
> 
>> 2) I want to make sure that the bug is really fixed and not just hidden
>>    from view.
> 
> i think it got hidden. Apparently splitting up a large kernel linear page 
> in IRQ context has a bug. I dont see it immediately what it could be - 
> Thomas, Suresh, do you have any ideas?
> 
>> 3) To see if anyone thinks that the fix should be included in
>>    2.6.27 -stable.
> 
> if 0b8fdcbcd287a1fbe66817491e6149841ae25705 applies cleanly to .27 -stable 
> then i'd agree it should be added. If there's lots of dependencies then 
> maybe not.

I also wonder who is doing an order 10 allocation... that'd worry me ;)

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