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Date:   Tue, 1 Aug 2023 10:02:47 -0400
From:   Steven Rostedt <rostedt@goodmis.org>
To:     Yajun Deng <yajun.deng@linux.dev>
Cc:     mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com,
        vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
        bsegall@google.com, mgorman@suse.de, bristot@redhat.com,
        vschneid@redhat.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] sched/rt: move back to RT_GROUP_SCHED and rename it
 child
Message-ID: <20230801100247.169b3a9c@gandalf.local.home>
In-Reply-To: <20230801100030.5efec7e2@gandalf.local.home>
References: <20230801062714.3424299-1-yajun.deng@linux.dev>
        <20230801100030.5efec7e2@gandalf.local.home>
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On Tue, 1 Aug 2023 10:00:30 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Tue,  1 Aug 2023 14:27:14 +0800
> Yajun Deng <yajun.deng@linux.dev> wrote:
> 
> > @@ -228,13 +228,10 @@ void init_tg_rt_entry(struct task_group *tg, struct rt_rq *rt_rq,
> >  	if (!rt_se)
> >  		return;

Ah, I missed the second part of your change log where you said parent is
only NULL when rt_se is NULL.

I would then add:

	if (!rt_se)
		return;

	if (WARN_ON_ONCE(!parent))
		return;

-- Steve


> >  
> > -	if (!parent)
> > -		rt_se->rt_rq = &rq->rt;
> > -	else
> > -		rt_se->rt_rq = parent->my_q;
> > -
> > +	rt_se->rt_rq = parent->my_q;  
> 
> So when this is called with parent = NULL, this will crash?
> 
> -- Steve
> 
> >  	rt_se->my_q = rt_rq;
> >  	rt_se->parent = parent;
> > +	parent->child = rt_se;
> >  	INIT_LIST_HEAD(&rt_se->run_list);
> >  }
> >