linux-kernel - Re: [PATCH v10 2/3] tracepoint: Make rcuidle tracepoint callers use SRCU

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Message-ID: <20180717201500.GA164758@joelaf.mtv.corp.google.com>
Date:   Tue, 17 Jul 2018 13:15:00 -0700
From:   Joel Fernandes <joel@...lfernandes.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org, kernel-team@...roid.com,
        Boqun Feng <boqun.feng@...il.com>,
        Byungchul Park <byungchul.park@....com>,
        Erick Reyes <erickreyes@...gle.com>,
        Ingo Molnar <mingo@...hat.com>,
        Julia Cartwright <julia@...com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Paul McKenney <paulmck@...ux.vnet.ibm.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Glexiner <tglx@...utronix.de>,
        Todd Kjos <tkjos@...gle.com>,
        Tom Zanussi <tom.zanussi@...ux.intel.com>,
        Will Deacon <will.deacon@....com>
Subject: Re: [PATCH v10 2/3] tracepoint: Make rcuidle tracepoint callers use
 SRCU

On Tue, Jul 17, 2018 at 08:25:28PM +0200, Peter Zijlstra wrote:
> On Fri, Jul 13, 2018 at 02:55:46PM -0700, Joel Fernandes wrote:
> > +		/* keep srcu and sched-rcu usage consistent */		\
> > +		preempt_disable_notrace();				\
> > +									\
> > +		/*							\
> > +		 * For rcuidle callers, use srcu since sched-rcu	\
> > +		 * doesn't work from the idle path.			\
> > +		 */							\
> > +		if (rcuidle)						\
> > +			idx = srcu_read_lock_notrace(&tracepoint_srcu);	\
> > +		else							\
> > +			rcu_read_lock_sched_notrace();			\
> 
> That else is completely superfluous. rcu_read_lock_sched_notrace() :=
> prempt_disable_notrace().

Yes, sorry I missed this in your original idea. Will do it this way and
repost. Thanks Peter!

- Joel