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Subject: Re: [PATCH 08/20] powerpc: Preemptible mmu_gather
From: Peter Zijlstra <peterz@infradead.org>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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Date: Tue, 31 Aug 2010 11:14:44 +0200
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On Tue, 2010-08-31 at 16:31 +1000, Benjamin Herrenschmidt wrote:

> Of course, with -rt and the pte lock becoming a mutex, all of your
> changes do become necessary (and I suppose that's where they come from).
>
> Now, those changes won't technically hurt on a non-rt kernel, tho they
> will add a tiny bit of overhead. I'll see if I can measure it.

Indeed, those parts are only strictly needed for -rt, I was hoping the
tiny bit of overhead wouldn't be too bad and we could keep it.

If not I guess we should put those two bits in __switch_to() under
CONFIG_PREEMPT_RT and carry them there for a little while longer.

> > I suppose that's what's causing the similar patch you have in -rt to
> > fail btw. This could be fixed easily by using "current" instead.
> 
> And here's a fix. Using current_thread_info() everywhere is better
> anyways, you are not supposed to touch the local_flags within anything
> but "current" so we may as well make it explicit.
> 
> Feel free to fold that into your -rt patch and this one if you decide
> not to drop that whole part. 

Thanks! And yeah I'd prefer to keep it to reduce Thomas' burden if
possible.