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

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Message-ID: <20171128192234.53d685d4@gandalf.local.home>
Date:   Tue, 28 Nov 2017 19:22:34 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     joe.korty@...current-rt.com
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, 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.

-- Steve