K 10
svn:author
V 3
bde
K 8
svn:date
V 27
2016-08-30T10:57:19.916288Z
K 7
svn:log
V 820
Start adding locking to sc_cngetc().

Restore an splx() lost in r228644.  We aren't nearly ready to remove
spl's.  They give hints about missing locking.  This lost one was
misplaced.  Dropping it early for convenience gave race windows for
accesses to the fkey buffer.  Giant locking accidentally fixed this
for non-console cases.

Put the spl's around the whole function.  Since there are many returns
that would need splx() just before them for a direct fix, split the
function into a wrapper that does the spl's and a "locked" function
that does the work.

Return earlier when no keyboard is attached to match the ordering in a
planned version.  This breaks the dubious feature of returning keys
from the fkey buffer after the keyboard has gone away.  Losing the keys
wouldn't matter, but we keep them too long now.

END