Subject: Re: Issue 90 of the NetBSD CVS Digest is out.
To: Current Users <current-users@NetBSD.org>
From: Matthias Scheler <firstname.lastname@example.org>
Date: 02/11/2007 23:03:47
On 11 Feb 2007, at 22:49, Aaron J. Grier wrote:
> the public announcements don't tell me anything other than "ooh,
> and neglect to tell me why M:N was seemingly abandoned.
I don't know all the details. What I can remember is:
1.) Our M:N implementation never worked properly on multiple CPUs.
2.) It didn't work very well on certain platforms e.g NetBSD-sparc
> this seems like quite a large change and it would be nice to know
> how we
> got here.
Is it really surprising that we got there? Solaris and Linux both
M:N to 1:1 because M:N didn't work very well.
One of the problems with M:N in Linux is e.g. that a userland thread
running on a kernel thread which was previously used to lock a mutex
userland thread which is currently not running. And if the active
tries to lock the same mutex the application will die because of a
recursive mutex entry.
Matthias Scheler http://zhadum.org.uk/