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Date: Mon, 4 Aug 2014 09:28:45 +0800
From: Lai Jiangshan <laijs@cn.fujitsu.com>
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To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>, <peterz@infradead.org>
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Subject: Re: [PATCH v3 tip/core/rcu 1/9] rcu: Add call_rcu_tasks()
References: <20140731215445.GA21933@linux.vnet.ibm.com> <1406843709-23396-1-git-send-email-paulmck@linux.vnet.ibm.com>
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On 08/01/2014 05:55 AM, Paul E. McKenney wrote:
> +		rcu_read_lock();
> +		for_each_process_thread(g, t) {
> +			if (t != current && ACCESS_ONCE(t->on_rq) &&
> +			    !is_idle_task(t)) {
> +				get_task_struct(t);
> +				t->rcu_tasks_nvcsw = ACCESS_ONCE(t->nvcsw);
> +				ACCESS_ONCE(t->rcu_tasks_holdout) = 1;
> +				list_add(&t->rcu_tasks_holdout_list,
> +					 &rcu_tasks_holdouts);

This loop will collect all the runnable tasks.  It is too much tasks.
Is it possible to collect only on_cpu tasks or PREEMPT_ACTIVE tasks?
It seems hard to achieve it.