Re: kern/40419 (processor sets broken on 5.99.6)

[Andrew Doran <ad%netbsd.org@localhost>]

The following reply was made to PR kern/40419; it has been noted by GNATS.

From: Andrew Doran <ad%netbsd.org@localhost>
To: Mindaugas Rasiukevicius <rmind%netbsd.org@localhost>
Cc: gnats-bugs%NetBSD.org@localhost, netbsd-bugs%netbsd.org@localhost, 
gnats-admin%netbsd.org@localhost
Subject: Re: kern/40419 (processor sets broken on 5.99.6)
Date: Wed, 21 Jan 2009 09:56:38 +0000

 On Wed, Jan 21, 2009 at 12:01:49AM +0000, Mindaugas Rasiukevicius wrote:
 
 > Andrew Doran <ad%netbsd.org@localhost> wrote:
 > > > We can do yield() in sys__pset_bind(). Do you think it is worth?
 > > 
 > > I was thinking of a function that scans all threads, with cpu_lock held, 
 > > and
 > > checks to see if their l_cpu is allowed by their affinity mask, processor
 > > set or LP_BOUND flag. If not, change l_cpu (or migrate if online), then do 
 > > a
 > > broadcast xcall to nullop() if there have been migrations.
 > 
 > After some thinking, I do not think it is worth. Theoretically, xc_broadcast
 > might still not ensure that all LWPs have migrated, eg. in a case when there
 > are many migrating LWPs in the same run-queue.
 
 Hmm. I can't look at the code right now. If we can have LWPs in the wrong
 runqueue after a pset/affinity change, we should move them to prevent them
 running on that CPU after there is a context switch. Maybe it would be
 useful to add a syncobj_t::sobj_changecpu()?
 
 Thanks,
 Andrew