Subject: Re: newlock
To: Garrett D'Amore <firstname.lastname@example.org>
From: Jason Thorpe <email@example.com>
Date: 09/03/2006 18:36:19
On Sep 3, 2006, at 5:24 PM, Garrett D'Amore wrote:
> I wish instead of "simple_locks", and "splx" and such we just had
> mutexes and spl() was handled under the covers.
That is the intent of the "newlock" branch I worked those N years ago,
that Andrew is now picking back up. I basically sat down with my copy
of _Solaris Internals_ and wrote a clone implementation of the Solaris
turnstiles, mutexes, and rwlocks.
> Recursive mutexes have their uses, but mostly they wind up being a
> crutch for poor design, I think. I agree with Jason here.
Exactly. If you NEED a recursive mutex, your code structure needs to
be fixed. If you can't avoid it, then your (poorly-designed)
subsystem can implement its own using mutexes underneath.
> I'd rather have actual condition variables than "msleep" and such.
> Condition variables are really, really useful for a variety of
> purposes. But I'm probably corrupted by having so many pleasant
> experiences developing for Solaris. :-)
Yah, a real CV implementation could be nice; but then again, it is
also really handy to have any arbitrary identifier available as a
That said, I DID do a turnstile implementation on the newlock branch,
and turnstiles are very conducive to CVs, and quite scalable. We
could certainly do away *sleep() entirely (by fully adopting
turnstiles and CVs) and eliminate the big fat "scheduler lock", which
is pretty much guaranteed to be a barrier to MP scalability (not that
it matters much in the NetBSD kernel right *now*).