linux-kernel - Re: [PATCH v3 tip/core/rcu 1/9] rcu: Add call_rcu

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Message-ID: <20140802145616.GA18195@redhat.com>
Date:	Sat, 2 Aug 2014 16:56:16 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...nel.org,
	laijs@...fujitsu.com, dipankar@...ibm.com,
	akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
	josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
	rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
	dvhart@...ux.intel.com, fweisbec@...il.com, bobby.prani@...il.com
Subject: Re: [PATCH v3 tip/core/rcu 1/9] rcu: Add call_rcu_tasks()

On 07/31, 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)) {

I didn't notice this check before, but it is not needed. for_each_process()
can see the idle threads, there are not on process/thread lists.

But this doesn't really matter, the main problem is that I still think that
for_each_process_thread() can't really work anyway.

Oleg.

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