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Date: Wed, 27 Aug 2008 10:02:38 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Yinghai Lu <yhlu.kernel@gmail.com>, Thomas Gleixner <tglx@linutronix.de>,
       "H. Peter Anvin" <hpa@zytor.com>,
       Andrew Morton <akpm@linux-foundation.org>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86: printk_time to use tsc before cpu_clock is ready
Message-ID: <20080827080238.GC4453@elte.hu>
References: <1219822736-18628-1-git-send-email-yhlu.kernel@gmail.com> <1219822736-18628-2-git-send-email-yhlu.kernel@gmail.com> <20080827074230.GA20993@elte.hu> <1219823233.6462.38.camel@twins>
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* Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:

> On Wed, 2008-08-27 at 09:42 +0200, Ingo Molnar wrote:
> > * Yinghai Lu <yhlu.kernel@gmail.com> wrote:
> > 
> > > +static unsigned long long tsc_clock(int cpu)
> > > +{
> > > +	unsigned long long t;
> > > +
> > > +	rdtscll(t);
> > > +
> > > +	return t;
> > > +}
> > 
> > hm, i'm not sure i like the whole direction - this reintroduces 
> > printk_clock in essence.
> > 
> > how about initializing cpu_clock() sooner, so that printk timestamps 
> > start ticking as soon as possible?
> 
> which will make some archs quite unhappy iirc, see those arm and ia64 
> bugs I caused the other day.

that's OK - that still allows arches to start their clocks whenever they 
want to. But also add the possibility for architectures to initialize 
things even sooner.

	Ingo