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From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: linux-kernel <linux-kernel@vger.kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	rostedt <rostedt@goodmis.org>
Subject: Possible use of RCU while in extended QS: idle vs RCU read-side in interrupt vs rcu_eqs_exit
Date: Wed, 9 Jan 2019 20:38:51 -0500 (EST)	[thread overview]
Message-ID: <2103471967.794.1547084331086.JavaMail.zimbra@efficios.com> (raw)

Hi Paul,

I've had a user report that trace_sched_waking() appears to be
invoked while !rcu_is_watching() in some situation, so I started
digging into the scheduler idle code.

It appears that interrupts are re-enabled before rcu_eqs_exit() is
invoked when exiting idle code from the scheduler.

I wonder what happens if an interrupt handler (including scheduler code)
happens to issue a RCU read-side critical section before rcu_eqs_exit()
is called ? Is there some code on interrupt entry that ensures rcu eqs
state is exited in such scenario ?

Thanks,

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com

             reply	other threads:[~2019-01-10  1:38 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-10  1:38 Mathieu Desnoyers [this message]
2019-01-10  4:13 ` Possible use of RCU while in extended QS: idle vs RCU read-side in interrupt vs rcu_eqs_exit Paul E. McKenney
2019-01-10  6:30   ` Mathieu Desnoyers
2019-01-10 14:19     ` Paul E. McKenney
2019-01-10 16:08 ` Steven Rostedt
2019-01-10 16:44   ` Mathieu Desnoyers
2019-01-10 17:11     ` Mathieu Desnoyers
2019-01-10 17:23       ` Steven Rostedt
2019-01-10 17:25       ` Mathieu Desnoyers
2019-01-10 17:45         ` Perf: event wakeup discards sched_waking events Mathieu Desnoyers
2019-01-14 13:09           ` Peter Zijlstra
2019-01-14 21:36             ` Mathieu Desnoyers
2019-01-14 22:04               ` Steven Rostedt
2019-01-14 22:31                 ` Mathieu Desnoyers

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