linux-kernel - Re: regression 4.4: deadlock in with cgroup percpu

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Message-ID: <20160121092703.GF6357@twins.programming.kicks-ass.net>
Date:	Thu, 21 Jan 2016 10:27:03 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Christian Borntraeger <borntraeger@...ibm.com>
Cc:	Heiko Carstens <heiko.carstens@...ibm.com>,
	Tejun Heo <tj@...nel.org>,
	"linux-kernel@...r.kernel.org >> Linux Kernel Mailing List" 
	<linux-kernel@...r.kernel.org>,
	linux-s390 <linux-s390@...r.kernel.org>,
	KVM list <kvm@...r.kernel.org>,
	Oleg Nesterov <oleg@...hat.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: regression 4.4: deadlock in with cgroup percpu_rwsem

On Thu, Jan 21, 2016 at 09:23:09AM +0100, Christian Borntraeger wrote:

> With Tejuns "cpuset: make mm migration asynchronous" and this hack
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c

> index cfdc0e6..0847bab 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -8099,8 +8099,8 @@ void free_fair_sched_group(struct task_group *tg)
>                 if (tg->cfs_rq)
>                         kfree(tg->cfs_rq[i]);
>                 if (tg->se) {
> -                       if (tg->se[i])
> -                               remove_entity_load_avg(tg->se[i]);
> +//                     if (tg->se[i])
> +//                             remove_entity_load_avg(tg->se[i]);
>                         kfree(tg->se[i]);
>                 }
>         }
> 
> things look good now on the scheduler/cgroup front. Thank you for your
> quick responses and answers.

OK, I'll work with TJ on fixing that. Depending on the complexity of
his patch I might just delete those two lines for -stable.

Thanks!