linux-kernel - Re: [ANNOUNCE] 4.4-rc6-rt1

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Date:	Sat, 16 Jan 2016 14:43:34 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Mike Galbraith <umgwanakikbuti@...il.com>
cc:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Clark Williams <williams@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-rt-users <linux-rt-users@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [ANNOUNCE] 4.4-rc6-rt1

On Sat, 16 Jan 2016, Mike Galbraith wrote:
> On Thu, 2016-01-14 at 17:05 +0100, Mike Galbraith wrote:
> 
> > This is virgin -rt1 modulo fixlet applied to v4.4.0, built with the
> > .config from v4.4.0 that built it (modulo RT_FULL) rebuilding itself
> > via make -j8.
> > 
> > homer:/root # vmstat 10
> > procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu-----
> >  r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
> >  0  1      0 14742988 179832 680792    0    0   634    25  326 1196  2  1 89  8  0
> >  8  0      0 14476084 179848 701632    0    0   814   525 2421 12314 11  1 87  1  0
> >  8  0      0 14483232 179864 712656    0    0   165  1628 2404 12320 11  1 87  1  0
> >  8  0      0 14493336 180008 727836    0    0   141   762 2328 11306 11  1 87  0  0
> >  8  0      0 14456436 180024 738356    0    0   159  1478 2336 11939 11  1 87  0  0
> > 
> > Way too idle, taking forever.
> 
> It now being the weekend...
> 
> sched: Disable default set_cpus_allowed() method during update_migrate_disable().
> 
> update_migrate_disable() calls class::set_cpus_allowed(), when that method
> is set_cpus_allowed_common(), writing to ->cpus_allowed defeats the intent
> of migrate_disable(), permanently disabling migration instead.

Ha, you found it as well :)

> Signed-off-by: Mike Galbraith <umgwanakikbuti@...il.com>
> ---
>  kernel/sched/core.c |    2 ++
>  1 file changed, 2 insertions(+)
> 
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -1205,6 +1205,8 @@ static int migration_cpu_stop(void *data
>   */
>  void set_cpus_allowed_common(struct task_struct *p, const struct cpumask *new_mask)
>  {
> +	if (__migrate_disabled(p))
> +		return;
>  	cpumask_copy(&p->cpus_allowed, new_mask);
>  	p->nr_cpus_allowed = cpumask_weight(new_mask);
>  }
>