Is MTX_CONTESTED evil?

[M. Warner Losh]

In message: <xzpekrgf103.fsf at dwp.des.no>
            des at des.no (Dag-Erling Smørgrav) writes:
: "Brian F. Feldman" <green at FreeBSD.org> writes:
: > Well, that certainly explains the blitz of crashes I had to fix
: > recently!  Since INVARIANTS and WITNESS are on by default, it would
: > make sense to make ADAPTIVE_MUTEX default to catch more bugs.
: 
: Making ADAPTIVE_MUTEXES default will not catch more bugs, it will just
: piss off users.

I think that if we don't fix the class of bugs that AM points out,
we'll ruin our reputation as a quality system in the long run.  Maybe
they are so pervasive that we don't want to turn it on by default just
yet, but there will come a time we turn it on, just like we turned on
WITNESS and INVARIANTS to get better coverage on our testing.

Warner