Message buffer and printf reentrancy patch

[M. Warner Losh]

In message: <200306151406.aa36218 at salmon.maths.tcd.ie>
            Ian Dowse <iedowse at maths.tcd.ie> writes:
: occur via tputchar() when using xconsole, and generally make the
: use of printf() in the kernel a bit safer. Many of the ideas here
: were suggested by Bruce Evans.

Safe enough to be used for ddb?  That is, can we get the ddb output in
out dmesg buffers?

Warner