svn commit: r233097 - head/sys/amd64/amd64

[Alan Cox]

On 03/17/2012 17:14, Nathan Whitehorn wrote:
>
>
> On Mar 17, 2012, at 5:04 PM, Alan Cox wrote:
>
>> Author: alc
>> Date: Sat Mar 17 22:04:58 2012
>> New Revision: 233097
>> URL: http://svn.freebsd.org/changeset/base/233097
>>
>> Log:
>>  With the changes over the past year to how accesses to the page's dirty
>>  field are synchronized, there is no need for pmap_protect() to acquire
>>  the page queues lock unless it is going to access the pv lists.
>>
>>  Reviewed by:    kib
>
> Under what circumstances does the page queue lock actually have to be 
> held?

You need it when you are manipulating the pvo_vlink lists.  That said, 
we are at the point where the PPC/AIM pmap could define its own PVO list 
mutex and not (ab)use the page queues mutex for this purpose.  Just do a 
straightforward, mechanical substitution, and you should be fine.

> It looks like from this that I can remove the page queue lock from the 
> PPC/AIM pmap_protect() completely, but I don't have a good sense of it.

Yes, you can this instant remove the acquisition and release of the page 
queues lock from this function.