linux-kernel - Re: [PATCH 1/2] tracing: Fix synth event test to avoid using smp_processor

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Date:   Thu, 20 Feb 2020 16:56:33 -0600
From:   Tom Zanussi <zanussi@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>
Cc:     artem.bityutskiy@...ux.intel.com, linux-kernel@...r.kernel.org,
        linux-rt-users@...r.kernel.org
Subject: Re: [PATCH 1/2] tracing: Fix synth event test to avoid using
 smp_processor_id()

Hi Steve,

On Thu, 2020-02-20 at 17:48 -0500, Steven Rostedt wrote:
> On Mon, 17 Feb 2020 18:52:29 +0900
> Masami Hiramatsu <mhiramat@...nel.org> wrote:
> 
> > Since smp_processor_id() requires irq-disabled or preempt-disabled,
> > synth event generation test module made some warnings. To prevent
> > that, use get_cpu()/put_cpu() instead of smp_processor_id().
> > 
> > Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> > ---
> >  kernel/trace/synth_event_gen_test.c |   23 +++++++++++++++++------
> >  1 file changed, 17 insertions(+), 6 deletions(-)
> > 
> 
> I just noticed this patch, after applying my version that just uses
> the
> raw_smp_processor_id(). We don't really care what CPU it is do we?
> 
> I didn't want a test to muck with preemption disabling and all that
> fun.
> 

Right, we don't really care, it's just to test the trace API - for this
it could even be a constant.  I just happened to pick that as an
example, and wasn't expecting unrelated complications.

Tom 

> -- Steve