linux-kernel - Re: Strange hang on ia64 with CONFIG_PRINTK

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Message-ID: <20080220081228.GA27036@elte.hu>
Date:	Wed, 20 Feb 2008 09:12:28 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Tony Luck <tony.luck@...il.com>
Cc:	Roland Dreier <rdreier@...co.com>,
	David Miller <davem@...emloft.net>,
	linux-kernel@...r.kernel.org
Subject: Re: Strange hang on ia64 with CONFIG_PRINTK_TIME=y


* Tony Luck <tony.luck@...il.com> wrote:

> > Perhaps what is happening is that cpu0 comes online ... safely skips 
> > over the early printk calls.  Calls cpu_init() which sets up the 
> > resources *it* needs (ar.k3 points to per-cpu space), and then 
> > executes sched_init() which marks it safe for all printk's. Then 
> > cpu1 comes up and does a printk before it gets to cpu_init().
> 
> I just tried Ingo's patch[1] on a 2.6.25-rc2 kernel with printk 
> timestamps turned on ... and it booted just fine on my tiger4.  The 
> default path for non-boot cpus is from head.S to start_secondary(), 
> and that calls cpu_init() pretty quickly.  There shouldn't normally[2] 
> be any printk() calls on the non-boot cpu before it is safe to do so.

ok. I've queued up the patch again in sched.git, as a .25 fix. Can i add 
your Tested-by and Acked-by tags?

	Ingo
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