linux-kernel - Re: [PATCH] tracing: Remove pointless memory barriers

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Message-ID: <20250626113708.4a96e47c@gandalf.local.home>
Date: Thu, 26 Jun 2025 11:37:08 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Nam Cao <namcao@...utronix.de>
Cc: Masami Hiramatsu <mhiramat@...nel.org>, Mathieu Desnoyers
 <mathieu.desnoyers@...icios.com>, linux-trace-kernel@...r.kernel.org,
 linux-kernel@...r.kernel.org, Gabriele Monaco <gmonaco@...hat.com>,
 john.ogness@...utronix.de
Subject: Re: [PATCH] tracing: Remove pointless memory barriers

On Thu, 26 Jun 2025 11:35:20 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:

> > @@ -2710,8 +2705,6 @@ void trace_buffered_event_enable(void)
> >  
> >  static void enable_trace_buffered_event(void *data)
> >  {
> > -	/* Probably not needed, but do it anyway */
> > -	smp_rmb();  
> 
> As the comment says, this one actually isn't needed, and yes, it can be
> removed.

One reason this isn't needed is because it's called via on_each_cpu() which
will trigger its own barriers.

-- Steve