[PATCH][WIP][RFC] powerpc: fixup lwsync at runtime

[Kumar Gala]

On Jun 20, 2008, at 6:23 PM, Benjamin Herrenschmidt wrote:

> On Fri, 2008-06-20 at 11:36 -0500, Kumar Gala wrote:
>> This is a work in progress towards make lwsync fixed up at  
>> runtime.  The
>> patch is based (requires) the module refactoring patch.  Some of  
>> this code
>> should be reworked based on the code patching work from Michael.   
>> Also,
>> ppc64 and vdso support needs a bit of cleaning up.
>>
>> Some questions:
>> * How do we determine at runtime if we need to convert sync to  
>> lwsync.
>> This is simliar to cpu_feature but has the issue that cpu_feature  
>> is about
>> either having code in or not.
>>
>> * Do we simplify the section of fixup information and remove the  
>> mask and
>> value since we don't use them and they double the size of the section
>
> Remind me why we want to do that ? ie. can't we just use lwsync
> unconditionally ? It's supposed to degrade to sync on CPUs that don't
> support it, or is that broken on some parts ?

I believe its broken on e500v1/v2.  However I'll double check.

- k