mpsafe psm driver needed

Philip Paeps philip at freebsd.org
Mon Jan 14 07:12:28 PST 2008


On 2008-01-14 09:20:11 (-0500), John Baldwin <jhb at freebsd.org> wrote:
> On Monday 14 January 2008 06:00:54 am Philip Paeps wrote:
> > On 2008-01-13 21:25:03 (+0100), Kris Kennaway <kris at FreeBSD.org> wrote:
> > > I've been looking at some mutex profiling traces from users of 6.x and 7.x 
> > > who are reporting that their mouse pointer sometimes freezes when their 
> > > system is busy.  In most of the situations I have looked at this is because 
> > > the psm driver is Giant-locked, and competes with other things like the 
> > > syncer (in 6.x), or sysctl calls (I have a WIP for this that I need to 
> > > revisit).
> > > 
> > > This is a minor problem from a grand architectural point of view but an 
> > > important one from a usability point of view.  I believe these particular 
> > > interactivity problems would be resolved if the psm driver no longer 
> > > required Giant.  Is anyone able to work on this?
> > 
> > I have taken a look at this in the past.  It's not a trivial problem.
> > 
> > There is a lot of what I can only charitably call "legacy code" in psm and it
> > appears that as soon as you touch any of it, it upsets at least one brand of
> > KVM "out there".
> > 
> > One of my mentees has been working on a rewrite for a while, but the project
> > has not yet been committed to cvs.
> > 
> > jls: any news on this?
> 
> Does psm(4) interface with any subsystems like tty(4)?

It shouldn't.  moused(8) listens on /dev/psm and sends events down again to
syscons with /dev/consctl.  (And syscons then pushes them back up through
/dev/sysmouse for things like X11 to listen on - yikes).

 - Philip

-- 
Philip Paeps                                    Please don't Cc me, I am
philip at freebsd.org                               subscribed to the list.

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