linux-kernel - Re: [PATCH 7/8] Remove current_tick

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Date:	Fri, 14 Mar 2008 20:48:29 -0700
From:	john stultz <johnstul@...ibm.com>
To:	Roman Zippel <zippel@...ux-m68k.org>
Cc:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org
Subject: Re: [PATCH 7/8] Remove current_tick_length()


On Sat, 2008-03-15 at 04:32 +0100, Roman Zippel wrote:
> Hi,
> 
> On Fri, 14 Mar 2008, john stultz wrote:
> 
> > On Fri, 2008-03-14 at 19:40 +0100, zippel@...ux-m68k.org wrote:
> > > plain text document attachment (tick_length)
> > > current_tick_length used to do a little more, but now it just returns
> > > tick_length, which we can also access directly at the few places, where
> > > it's needed.
> > > 
> > > Signed-off-by: Roman Zippel <zippel@...ux-m68k.org>
> > 
> > Hrm. I'm not sure I like using a global variable instead of using an
> > accessor function. At least with the accessor function folks couldn't
> > just tweak the value outside ntp as easily.
> 
> Why would someone do something silly like this?

Its not a huge deal, but we've seen globally scoped timekeeping
variables misused either accidentally or intentionally. Awhile back ppc
was corrupting time_offset by using it for a timezone offset value. 

So I think its a valid maintainability issue.

> > Is there any additional rational for this change?
> 
> Useless bloat?

I agree its a trade off. But do you have performance numbers to make the
maintainability trade off worth it? (I admit, it is used in the
timer_interrupt, so it may very well be worth it, but we might want to
check first).

thanks
-john


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