Re: [COUNTERPATCH] mm: avoid overflowing preempt_count() in mmu_take_all_locks()

Avi Kivity
2010-04-01T16:38:50Z

On 04/01/2010 06:42 PM, Andrea Arcangeli wrote:
> On Thu, Apr 01, 2010 at 01:43:14PM +0200, Peter Zijlstra wrote:
>
>> On Thu, 2010-04-01 at 13:27 +0200, Peter Zijlstra wrote:
>>
>>> I've almost got a patch done that converts those two, still need to look
>>> where that tasklist_lock muck happens.
>>>
>> OK, so the below builds and boots, only need to track down that
>> tasklist_lock nesting, but I got to run an errand first.
>>
> You should have a look at my old patchset where Christoph already
> implemented this (and not for decreasing latency but to allow
> scheduling in mmu notifier handlers, only needed by XPMEM):
>
> http://www.kernel.org/pub/linux/kernel/people/andrea/patches/v2.6/2.6.26-rc7/mmu-notifier-v18/
>
> The ugliest part of it (that I think you missed below) is the breakage
> of the RCU locking in the anon-vma which requires adding refcounting
> to it. That was the worst part of the conversion as far as I can tell.
>
> http://www.kernel.org/pub/linux/kernel/people/andrea/patches/v2.6/2.6.26-rc7/mmu-notifier-v18/anon-vma
>

Can we use srcu now instead?

--
error compiling committee.c: too many arguments to function