linux-kernel - Re: [PATCH] tracing: Have synthetic event test use raw_smp_processor

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Date:   Fri, 21 Feb 2020 09:22:30 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Tom Zanussi <zanussi@...nel.org>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>
Subject: Re: [PATCH] tracing: Have synthetic event test use
 raw_smp_processor_id()

On Thu, 20 Feb 2020 16:14:40 -0600
Tom Zanussi <zanussi@...nel.org> wrote:

> Hi Steve,
> 
> On Thu, 2020-02-20 at 16:29 -0500, Steven Rostedt wrote:
> > From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>
> > 
> > The test code that tests synthetic event creation pushes in as one of
> > its
> > test fields the current CPU using "smp_processor_id()". As this is
> > just
> > something to see if the value is correctly passed in, and the actual
> > CPU
> > used does not matter, use raw_smp_processor_id(), otherwise with
> > debug
> > preemption enabled, a warning happens as the smp_processor_id() is
> > called
> > without preemption enabled.
> > 
> > Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
> 
> Makes sense - I guess it's simpler than Masami's and fine for this
> purpose.
> 
> Reviewed-by: Tom Zanussi <zanussi@...nel.org>

Hmm, can we reserve ring buffer on CPU1 and commit it on CPU2?
Shouldn't we disable preemption between them?

Thank you,

-- 
Masami Hiramatsu <mhiramat@...nel.org>