From: John Stultz
Date: Wed Apr 24 2013 - 12:42:29 EST

On 04/24/2013 09:32 AM, Kay Sievers wrote:
On Wed, Apr 24, 2013 at 6:07 PM, John Stultz <john.stultz@xxxxxxxxxx> wrote:

So summarizing the above, because as much as I'm aware, its always been
redundant and unnecessary on x86. Thus being able at build time to mark it
as unnecessary was attractive, since it reduced the code paths running at

That said, Kay's concerns about userland implications (basically the
userland side effects of SYSTOHC being enabled) give me pause, so I may
revert the HAS_PERSISTENT_CLOCK on x86 change.
Thanks a lot for all the missing details!

No, I think that all makes too much sense to revert it. Let's just
find a way to solve it properly. I don't think it is of any pressing
importance to keep the old behaviour, if we can still provide the
functionality today.

So some compile time optimizations for code that likely needs to be reworked anyway aren't worth the risk of breaking userland to me. Let me pull these out (on the kernel side, the same code paths will run, we just avoid some extra checks) so the hctosys flag doesn't change in distro configs that expect it.


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