linux-kernel - Re: [PATCH] time: remove xtime

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Message-ID: <1271131600.3469.20.camel@localhost.localdomain>
Date:	Mon, 12 Apr 2010 21:06:40 -0700
From:	john stultz <johnstul@...ibm.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Petr Titěra <P.Titera@...tury.cz>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] time: remove xtime_cache (take 2)

On Mon, 2010-04-12 at 21:00 -0400, Andrew Morton wrote:
> On Tue,  6 Apr 2010 14:30:51 -0700 John Stultz <johnstul@...ibm.com> wrote:
> 
> > Thomas: Mind queueing this up for 2.6.35?
> > 
> > With the earlier logarithmic time accumulation patch, xtime will now
> > always be within one "tick" of the current time, instead of possibly
> > half a second off.
> > 
> > This removes the need for the xtime_cache value, which always stored the
> > time at the last interrupt, so this patch cleans that up removing the
> > xtime_cache related code.
> > 
> > This patch also addresses an issue with an earlier version of this change,
> > where xtime_cache was normalizing xtime, which could in some cases be
> > not valid (ie: tv_nsec == NSEC_PER_SEC). This is fixed by handling
> > the edge case in update_wall_time().
> > 
> > ...
> >
> > --- a/kernel/time.c
> > +++ b/kernel/time.c
> > @@ -135,7 +135,6 @@ static inline void warp_clock(void)
> >  	write_seqlock_irq(&xtime_lock);
> >  	wall_to_monotonic.tv_sec -= sys_tz.tz_minuteswest * 60;
> >  	xtime.tv_sec += sys_tz.tz_minuteswest * 60;
> > -	update_xtime_cache(0);
> >  	write_sequnlock_irq(&xtime_lock);
> >  	clock_was_set();
> >  }
> 
> This conflicts with your time-clean-up-warp_clock.patch, below.
> 
> Shrug, I simply ignored the rejected hunk.

Yep. That should be fine. We're just dropping the update_xtime_cache
call, so if it doesn't exist, its not a problem.

thanks
-john

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