Re: mutexes, IPL, tty locking

[David Holland <dholland-tech%netbsd.org@localhost>]

On Wed, Oct 21, 2009 at 09:52:35PM +0100, David Laight wrote:
 > But the locking scheme ought to support releasing locks in other
 > that strict reverse order of acquisition. Which rather makes
 > saving the old IPL anywhere other than in the callers stack frame
 > rather difficult.

Not really. My understanding is that somewhere in there there's code
that counts how many times each IPL has been asserted; the current IPL
is thus the highest IPL that's been asserted at least once.

In this case it would seem that the observed behavior is wrong. But
maybe my understanding is inadequate.

-- 
David A. Holland
dholland%netbsd.org@localhost