[PATCH] fix gettimeofday vs. update_gtod race

[Nathan Lynch]

Benjamin Herrenschmidt wrote:
> On Wed, 2006-08-16 at 19:18 -0500, Nathan Lynch wrote:
> 
> > No?  I didn't find anything about mftb having synchronizing
> > behavior.  How should we ensure that temp_varp is assigned before
> > reading the timebase?
> 
> I sync an isync would be enough.

I see, thanks.

> > > I need to think about it a bit more closely but what about instead
> > > just check if tb_ticks goes negative, and if yes, just do get_tb()
> > > again ?  That might be faster than having a sync in there and should
> > > still be correct.
> > 
> > I did try something like that but found that a loop (i.e. multiple
> > get_tb's to "catch up") was necessary.
> 
> Hrm... even with an isync ?

No, sorry, I was confusing this with a different bug (cpu
hotplug-related, separate patch for that forthcoming).