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

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Message-ID: <ada7ih7qjoq.fsf@cisco.com>
Date:	Thu, 14 Feb 2008 14:04:05 -0800
From:	Roland Dreier <rdreier@...co.com>
To:	"Tony Luck" <tony.luck@...el.com>
Cc:	"David Miller" <davem@...emloft.net>, mingo@...e.hu,
	linux-kernel@...r.kernel.org
Subject: Re: Strange hang on ia64 with CONFIG_PRINTK_TIME=y

 > >  The strange thing is that Ingo's patch to make cpu_clock() a NOP until
 > >  after sched_init() didn't fix things for me...

 > Very strange.  I threw in an output line counter into the printk code() ... if I
 > disable the timestamps for the first 30 lines, then everything is good (so the
 > basic timestamping code does still work on ia64). But I would have thought
 > that Ingo's delay until sched_init() ought to be long enough too. Clearly I
 > need to figure out exactly what needs to be initialized to prevent the
 > hang/crash.

I guess sched_init() is too early... it does seem really strange to
me, but I just double checked with Ingo's patch and it does indeed
hang.  The slow way to make progress is just to go through
start_kernel() line-by-line and enable cpu_clock() at each stage, and
see where it stops hanging.  I'll give that a shot as a background
process (my ia64 box takes quite a while to boot, so each test takes a
long time but requires very little of my attention).
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