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Message-ID: <1f1b08da0908061536o57cebeb6r2f522cb3c5419e1@mail.gmail.com>
Date: Thu, 6 Aug 2009 15:36:36 -0700
From: john stultz <johnstul@...ibm.com>
To: Ingo Molnar <mingo@...e.hu>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
Thomas Gleixner <tglx@...utronix.de>,
Andrew Morton <akpm@...ux-foundation.org>,
LKML <linux-kernel@...r.kernel.org>,
Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: Re: [GIT pull] timers fixes for 2.6.31
On Fri, Jul 31, 2009 at 5:37 AM, Ingo Molnar<mingo@...e.hu> wrote:
> [ Markus, John: the fix looks right for .31 but i think there's two
> small structural problems with this code, which might have
> contributed to the bug to happen to begin with:
>
> Firstly, ->mult_orig is a slight misnomer - if it was named
> properly we wouldnt even need the comments to explain how to use
> and update it. It's the unadjusted multiplicator while _orig
> patterns in the kernel generally suggest some sort of save/restore
> pattern (which this is not).
>
> I'd suggest to rename it to ->mult_unadjusted, ->mult_raw or
> ->mult_static instead. This field has not gotten into many
> clocksource drivers yet so it's easy to do. For .32 obviously.
>
> Secondly, the broader design question is: why are clocksource
> drivers mucking around with NTP details? Whether NTP is running
> should be a transparent detail to drivers and if such details are
> visible in low level driver (which they are in
> arch/arm/plat-omap/common.c et al) that's sign of uncleanliness.
> Mind improving that? (for .32 too)
Well, the clocksources aren't really mucking with NTP details, but NTP
mucks with the clocksource. And so this was a way to try to preserve
the original mult value, and I'll admit was a bit stapled on. This
mostly comes from how the clocksource structure has swelled over time
to include quite a bit of timekeeping specific information.
Splitting this up has been on my list for awhile, but I've never
gotten to it. However, Martin Schwidefsky has been doing a great job
with his latest patches cleaning up some of uglier parts of the
timekeeping/clocksource interactions. There is still lots of changes
I'd like to see, but they will take time as we still haven't gotten
all the arches over to GENERIC_TIME, so some cruft has to stick
around. But Martin's patches are a great big step towards it and
hopefully his patches will be ready for .32.
thanks
-john
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