On Thu, 19 Jul 2012 21:11:44 -0000, Seiji Aguchi said:

> [Solution]
>    To avoid losing a critical message, this patchset is based on a following concept.
>      - A basic policy is _not_ to overwrite existing entries.
>
>      - However, if kernel panics while a system is rebooting, a critical message
>        can't be saved by the policy above.
>        (In this case, panic message is critical.)

OK, system boots in "overwrite mode", and when done booting, we go into
"non-overwrite mode".  Makes sense to me.  Only part I'm missing is how/when/why
we leave overwrite mode - what makes the change, and how?

(If I missed an ioctl or /sys entry or something that userspace toggles to say "I'll
take care of it from here", please point me at it and I'll go re-read after I find
some more caffeine ;)