linux-kernel - Re: [BISECTION RESULT] sched: revert cpu_clock to pre-27ec4407790d075c325e1f4da0a19c56953cce23 state

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Message-ID: <20080805173447.GD7812@us.ibm.com>
Date:	Tue, 5 Aug 2008 10:34:47 -0700
From:	Nishanth Aravamudan <nacc@...ibm.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	mingo@...e.hu, tony.luck@...el.com, linux-ia64@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>,
	Bill Gatliff <bgat@...lgatliff.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>
Subject: Re: [BISECTION RESULT] sched: revert cpu_clock to
	pre-27ec4407790d075c325e1f4da0a19c56953cce23 state

On 05.08.2008 [10:56:25 +0200], Peter Zijlstra wrote:
> On Mon, 2008-08-04 at 12:46 -0700, Nishanth Aravamudan wrote:
> > Bisection on an x455 (2-node IA64) showed that commit
> > 27ec4407790d075c325e1f4da0a19c56953cce23 (sched: make cpu_clock()
> > globally synchronous) broke booting. I see the uncompressing initramfs
> > message and then nothing on the console. I wait about 5 minutes (which
> > is way longer than it takes for the first console messages to get
> > printed normally). The commit immediately before it works fine.
> > 
> > The commit no longer cleanly reverts, but I tried to manually put things
> > back to the way they were before in cpu_clock(). The resulting kernel
> > boots fine. I could figure out a clean way to leave cpu_clock() in
> > sched_clock.c because of all the rq dependencies from sched.c. The
> > attempt I tested is below [1]. This patch is *NOT* for inclusion, just
> > to demonstrate what I tested.
> > 
> > I'm happy to test any better patches.
> 
> Does this work for you?
> 
> ---
> Subject: sched_clock: delay using sched_clock()
> 
> Some arch's can't handle sched_clock() being called too early - delay
> this until sched_clock_init() has been called.
> 
> Reported-by: Bill Gatliff <bgat@...lgatliff.com>
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> CC: Russell King - ARM Linux <linux@....linux.org.uk>

Yep, this fixes things on the box, as well.

Tested-by: Nishanth Aravamudan <nacc@...ibm.com>

Thanks,
Nish

-- 
Nishanth Aravamudan <nacc@...ibm.com>
IBM Linux Technology Center
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