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Date: Mon, 7 May 2018 14:46:11 -0700
From: Joel Fernandes <joel@joelfernandes.org>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Joel Fernandes <joelaf@google.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        rostedt <rostedt@goodmis.org>, Peter Zijlstra <peterz@infradead.org>,
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        Namhyung Kim <namhyung@kernel.org>,
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Subject: Re: [PATCH RFC v6 4/5] tracepoint: Make rcuidle tracepoint callers
 use SRCU
Message-ID: <20180507214611.GB13787@joelaf.mtv.corp.google.com>
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On Mon, May 07, 2018 at 05:05:41PM -0400, Mathieu Desnoyers wrote:
> ----- On May 7, 2018, at 4:41 PM, Joel Fernandes joelaf@google.com wrote:
> [...]
> > +extern struct srcu_struct tracepoint_srcu;
> > +
> > extern int
> > tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data);
> > extern int
> > @@ -77,6 +80,9 @@ int unregister_tracepoint_module_notifier(struct
> > notifier_block *nb)
> >  */
> > static inline void tracepoint_synchronize_unregister(void)
> > {
> > +#ifdef CONFIG_TRACEPOINTS
> > +	synchronize_srcu(&tracepoint_srcu);
> > +#endif
> > 	synchronize_sched();
> 
> Why is this ifdef needed ?

tracepoint_srcu is defined in tracepoint.c so if we don't protect usage here, it
would cause a build error.

thanks,

- Joel