linux-kernel - Re: [PATCH 2/6] x86: allow to call text_poke

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Message-ID: <20131019180239.1e318628@gandalf.local.home>
Date:	Sat, 19 Oct 2013 18:02:39 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	paulmck@...ux.vnet.ibm.com
Cc:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Petr Mladek <pmladek@...e.cz>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jiri Kosina <jkosina@...e.cz>, linux-kernel@...r.kernel.org,
	x86@...nel.org
Subject: Re: [PATCH 2/6] x86: allow to call text_poke_bp during boot

On Sat, 19 Oct 2013 14:33:50 -0700
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> wrote:

 
> > > It's used to convert the calls to mcount to nops. But maybe a better
> > > thing to do is to check if we only have a single CPU:
> > > 
> > > static void run_sync(void)
> > > {
> > > 	if (num_online_cpus() != 1)
> > 
> > Hmm, to be more robust to handle our future "ideal" machines, perhaps
> > this should be:
> > 
> > 	/* Ideally we would like to run on zero CPUS! */
> > 	if (num_online_cpus() < 2)
> 

Bah! And for such a simple computation, I got it wrong.


	/* Ideally we would like to run on zero CPUS! */
	if (num_online_cpus > 1)

But I guess the question comes. If we are running on zero CPUS, should
we perform the "on_each_cpu(do_sync_core, NULL, 1);" or not? Same goes
with 5i-3 CPUS, or negative number CPUs. If we need to do on_each_cpu(),
then I guess the != 1 will suffice.

-- Steve
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