linux-kernel - Re: [tip:sched/core] sched/fair: Use rq_lock/unlock in online_fair_sched

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Date:   Mon, 12 Aug 2019 09:13:13 -0400
From:   Phil Auld <pauld@...hat.com>
To:     tglx@...utronix.de
Cc:     peterz@...radead.org, mingo@...hat.com, hpa@...or.com,
        linux-kernel@...r.kernel.org, mingo@...nel.org,
        vincent.guittot@...aro.org
Subject: Re: [tip:sched/core] sched/fair: Use rq_lock/unlock in
 online_fair_sched_group

On Mon, Aug 12, 2019 at 05:52:04AM -0700 tip-bot for Phil Auld wrote:
> Commit-ID:  a46d14eca7b75fffe35603aa8b81df654353d80f
> Gitweb:     https://git.kernel.org/tip/a46d14eca7b75fffe35603aa8b81df654353d80f
> Author:     Phil Auld <pauld@...hat.com>
> AuthorDate: Thu, 1 Aug 2019 09:37:49 -0400
> Committer:  Thomas Gleixner <tglx@...utronix.de>
> CommitDate: Mon, 12 Aug 2019 14:45:34 +0200
> 
> sched/fair: Use rq_lock/unlock in online_fair_sched_group
> 
> Enabling WARN_DOUBLE_CLOCK in /sys/kernel/debug/sched_features causes
> warning to fire in update_rq_clock. This seems to be caused by onlining
> a new fair sched group not using the rq lock wrappers.
> 
>   [] rq->clock_update_flags & RQCF_UPDATED
>   [] WARNING: CPU: 5 PID: 54385 at kernel/sched/core.c:210 update_rq_clock+0xec/0x150
> 
>   [] Call Trace:
>   []  online_fair_sched_group+0x53/0x100
>   []  cpu_cgroup_css_online+0x16/0x20
>   []  online_css+0x1c/0x60
>   []  cgroup_apply_control_enable+0x231/0x3b0
>   []  cgroup_mkdir+0x41b/0x530
>   []  kernfs_iop_mkdir+0x61/0xa0
>   []  vfs_mkdir+0x108/0x1a0
>   []  do_mkdirat+0x77/0xe0
>   []  do_syscall_64+0x55/0x1d0
>   []  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> 
> Using the wrappers in online_fair_sched_group instead of the raw locking
> removes this warning.
> 
> [ tglx: Use rq_*lock_irq() ]
> 
> Signed-off-by: Phil Auld <pauld@...hat.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Vincent Guittot <vincent.guittot@...aro.org>
> Cc: Ingo Molnar <mingo@...nel.org>
> Link: https://lkml.kernel.org/r/20190801133749.11033-1-pauld@redhat.com
> ---
>  kernel/sched/fair.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 19c58599e967..1054d2cf6aaa 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -10281,18 +10281,18 @@ err:
>  void online_fair_sched_group(struct task_group *tg)
>  {
>  	struct sched_entity *se;
> +	struct rq_flags rf;
>  	struct rq *rq;
>  	int i;
>  
>  	for_each_possible_cpu(i) {
>  		rq = cpu_rq(i);
>  		se = tg->se[i];
> -
> -		raw_spin_lock_irq(&rq->lock);
> +		rq_lock_irq(rq, &rf);
>  		update_rq_clock(rq);
>  		attach_entity_cfs_rq(se);
>  		sync_throttle(tg, i);
> -		raw_spin_unlock_irq(&rq->lock);
> +		rq_unlock_irq(rq, &rf);
>  	}
>  }
>  

Thanks Thomas!

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