Strange hang on ia64 with CONFIG_PRINTK_TIME=y

[Roland Dreier]

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?

Thanks,
  Roland
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