linux-kernel - Re: [RFC][PATCH] tracepoints: Free early tracepoints after RCU is initialized

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Message-Id: <20180810170709.GW24813@linux.vnet.ibm.com>
Date:   Fri, 10 Aug 2018 10:07:09 -0700
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [RFC][PATCH] tracepoints: Free early tracepoints after RCU is
 initialized

On Fri, Aug 10, 2018 at 12:35:17PM -0400, Steven Rostedt wrote:
> On Fri, 10 Aug 2018 12:30:42 -0400
> Steven Rostedt <rostedt@...dmis.org> wrote:
> 
> Maybe I should say SRCU?

That would be an improvement.  What, me read comments?  ;-)

						Thanx, Paul

> +/* SRCU is initialized at core_initcall */
> +postcore_initcall(release_early_probes);
> +
>  static inline void release_probes(struct tracepoint_func *old)
>  {
>  	if (old) {
>  		struct tp_probes *tp_probes = container_of(old,
>  			struct tp_probes, probes[0]);
> +
> +		/*
> +		 * We can't free probes if SRCU is not initialized yet.
> +		 * Postpone the freeing till after SRCU is initialized.
> +		 */
> +		if (unlikely(!ok_to_free_tracepoints)) {
> +			tp_probes->rcu.next = early_probes;
> +			early_probes = &tp_probes->rcu;
> +			return;
> +		}
> +
> 
> -- Steve
>