linux-kernel - Re: [PATCH] 4.4.86-rt99: fix sync breakage between nr_cpus_allowed and cpus

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Message-ID: <20171129142448.GA18507@zipoli.concurrent-rt.com>
Date:   Wed, 29 Nov 2017 09:24:48 -0500
From:   joe.korty@...current-rt.com
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: Re: [PATCH] 4.4.86-rt99: fix sync breakage between nr_cpus_allowed
 and cpus_allowed

On Tue, Nov 28, 2017 at 07:22:34PM -0500, Steven Rostedt wrote:
> On Tue, 21 Nov 2017 10:33:17 -0500
> joe.korty@...current-rt.com wrote:
> 
> > On Tue, Nov 21, 2017 at 09:33:52AM -0500, joe.korty@...current-rt.com wrote:
> > > On Mon, Nov 20, 2017 at 11:57:51PM -0500, Steven Rostedt wrote:  
> > > > On Mon, 20 Nov 2017 23:02:07 -0500
> > > > Steven Rostedt <rostedt@...dmis.org> wrote:
> > > > 
> > > >   
> > > > > Ideally, I would like to stay close to what upstream -rt does. Would
> > > > > you be able to backport the 4.11-rt patch?
> > > > > 
> > > > > I'm currently working on releasing 4.9-rt and 4.4-rt with the latest
> > > > > backports. I could easily add this one too.  
> > > > 
> > > > Speaking of which. I just backported this patch to 4.4-rt. Is this what
> > > > you are talking about?  
> > > 
> > > Yes it is.
> > > Thanks for finding that!
> > > Joe  
> > 
> > I spoke too fast.  You will a variant of my one-liner fix
> > when you backport the 4.11.12-r16 patch:
> > 
> >     rt-Increase-decrease-the-nr-of-migratory-tasks-when-.patch
> > 
> > to 4.9-rt and 4.4-rt.  The fix of interest is the introduction of
> > 
> >     p->nr_cpus_allowed = cpumask_weight(&p->cpus_mask);
> > 
> > to migrate_enable_update_cpus_allowed().
> 
> You totally confused me here.
> 
> Hmm, that patch isn't marked for stable. I'm guessing that it should be
> backported.
> 
> Now are you saying your patch still needs to be applied if we backport
> this patch? Or does your patch need to be applied to what I have
> already done?
> 
> I want to release 4.4-rt (and 4.9-rt) this week so let me know.



Hi Steve,
Just porting that other patch should do the trick.  Or you can just apply
my patch, I know that one works as it has actually been tested.

Joe