linux-kernel - Re: [PATCH] timekeeping: drop irq-context clocksource polling

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Message-Id: <1175809082.28526.28.camel@localhost>
Date:	Thu, 05 Apr 2007 14:38:02 -0700
From:	john stultz <johnstul@...ibm.com>
To:	Daniel Walker <dwalker@...sta.com>
Cc:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	mingo@...e.hu
Subject: Re: [PATCH] timekeeping: drop irq-context clocksource polling

On Thu, 2007-04-05 at 14:29 -0700, Daniel Walker wrote:
> On Thu, 2007-04-05 at 14:25 -0700, john stultz wrote:
> > On Thu, 2007-04-05 at 14:03 -0700, Daniel Walker wrote:
> > > Before this change the timekeeping code would poll the clocksource
> > > list every interrupt. This changes that so the clocksource list is
> > > only checked when there has been and update, and no longer checks
> > > in interrupt context.
> > > 
> > > This also has a few small space and line cleanups.
> > > 
> > > Boot tested on i386, compile tested on x86_64 .. However, I couldn't
> > > find a !GENERIC_TIME that compiled without this change so it's untested..
> > > 
> > > Signed-Off-By: Daniel Walker <dwalker@...sta.com>
> > 
> > Err.. I think you need to be holding a write on the xtime_lock (as is
> > done before calling update_wall_time()) when changing the clocksource.
> 
> I added a write_seqlock_irqsave() on xtime_lock in
> change_clocksource() .. Did I need more (different) protection than
> that?

Nope. You're ok there. I just missed it and then I tried to cancel my
mail from being sent, but apparently it still got out. whoops! :)

-john


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