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Date:   Wed, 11 Nov 2020 08:49:41 -0500
From:   Steven Rostedt <rostedt@goodmis.org>
To:     "Paul E. McKenney" <paulmck@kernel.org>
Cc:     "Joel Fernandes (Google)" <joel@joelfernandes.org>,
        linux-kernel@vger.kernel.org,
        Frederic Weisbecker <frederic@kernel.org>,
        Neeraj Upadhyay <neeraju@codeaurora.org>,
        Josh Triplett <josh@joshtriplett.org>,
        Lai Jiangshan <jiangshanlai@gmail.com>,
        Marco Elver <elver@google.com>,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        rcu@vger.kernel.org, "Uladzislau Rezki (Sony)" <urezki@gmail.com>,
        fweisbec@gmail.com, neeraj.iitr10@gmail.com
Subject: Re: [PATCH v9 4/7] rcu/trace: Add tracing for how segcb list
 changes
Message-ID: <20201111084941.1db1b324@gandalf.local.home>
In-Reply-To: <20201111003530.GA10251@paulmck-ThinkPad-P72>
References: <20201103142603.1302207-1-joel@joelfernandes.org>
        <20201103142603.1302207-5-joel@joelfernandes.org>
        <20201111003530.GA10251@paulmck-ThinkPad-P72>
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On Tue, 10 Nov 2020 16:35:30 -0800
"Paul E. McKenney" <paulmck@kernel.org> wrote:

> > +void __trace_rcu_segcb_stats(struct rcu_segcblist *rsclp, const char *context)
> > +{
> > +	int cbs[RCU_CBLIST_NSEGS];
> > +	unsigned long gps[RCU_CBLIST_NSEGS];
> > +
> > +	if (!trace_rcu_segcb_stats_enabled())
> > +		return;  
> 
> Can't you rely on the trace system to enable and disable this trace
> event?  If the thought is to save instructions, then moving all this
> into TP_fast_assign() enables the trace system to deal with that as well.
> 
> > +	rcu_segcblist_countseq(rsclp, cbs, gps);
> > +
> > +	trace_rcu_segcb_stats(context, cbs, gps);
> > +}
> > +#endif

Yeah, I agree with Paul. I think it is possible to move this all into the
TP_fast_assign. If you have trouble doing so, let me know.

-- Steve