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From: David Miller <davem@davemloft.net>
To: rdreier@cisco.com
Cc: linux-kernel@vger.kernel.org, mingo@elte.hu
Subject: Re: Strange hang on ia64 with CONFIG_PRINTK_TIME=y
Date: Tue, 12 Feb 2008 23:01:56 -0800 (PST)	[thread overview]
Message-ID: <20080212.230156.33759433.davem@davemloft.net> (raw)
In-Reply-To: <adazlu5tlve.fsf@cisco.com>

From: Roland Dreier <rdreier@cisco.com>
Date: Tue, 12 Feb 2008 22:24:05 -0800

> I'm seeing a strange hang with current git (head 96b5a46e) on an ia64
> box -- an Intel SDV with 2 dual core hyperthreaded Itanium 2 CPUs (so
> 8 logical CPUs to the kernel).  It hangs without printing anything
> ("Uncompressing Linux... done" from ELILO is the last thing I see) if
> I have CONFIG_PRINTK_TIME=y; it works fine with CONFIG_PRINTK_TIME=n.
> 
> The really strange thing is that I have bisected this down to 326e96b9
> ("printk: revert ktime_get() timestamps"), and verified that if revert
> this one patch on top of my current git tree, then the kernel boots
> fine with CONFIG_PRINTK_TIME=y.  The strange thing is that I have also
> checked that the real v2.6.24 kernel boots fine on this system, and as
> far as I can tell, 2.6.24 didn't have the commit that 326e96b9 reverts
> (19ef9309), so there is some interaction with another patch that made
> 19ef9309 necessary on my system.
> 
> Any good idea how to debug this, given that the broken kernels don't
> give any output at all?

The kernel now derefernces per-cpu variables very early, essentially
in the very first printk() (via printk()'s call to cpu_clock()).

This bit me on sparc64 because of how I do the per-cpu address
formation.  If I booted on a non-zero cpuid things would explode.

You might be hitting something similar.

  reply	other threads:[~2008-02-13  7:01 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-13  6:24 Roland Dreier
2008-02-13  7:01 ` David Miller [this message]
2008-02-13 12:57   ` Ingo Molnar
2008-02-13 13:02     ` Ingo Molnar
2008-02-14  0:26       ` Roland Dreier
2008-02-13 13:03     ` David Miller
2008-02-13 13:06       ` Ingo Molnar
2008-02-14  0:59       ` Tony Luck
2008-02-14  1:04         ` David Miller
2008-02-14  3:33           ` Tony Luck
2008-02-14  3:47             ` Roland Dreier
2008-02-14 18:24               ` Luck, Tony
2008-02-14 21:27               ` Tony Luck
2008-02-14 22:04                 ` Roland Dreier
2008-02-14 22:23                   ` Luck, Tony
2008-02-15  2:17                     ` Tony Luck
2008-02-19 22:40                       ` Tony Luck
2008-02-20  8:12                         ` Ingo Molnar
2008-02-20  8:15                           ` David Miller
2008-02-20 23:35                         ` Roland Dreier
2008-02-20 23:36                         ` Roland Dreier

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