linux-kernel - Re: [PATCH 5/5] perf tools: Share process map groups within process threads

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Date:	Mon, 17 Mar 2014 11:45:33 +0100
From:	Jiri Olsa <jolsa@...hat.com>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	linux-kernel@...r.kernel.org, Don Zickus <dzickus@...hat.com>,
	Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
	David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
Subject: Re: [PATCH 5/5] perf tools: Share process map groups within process
 threads

On Mon, Mar 17, 2014 at 04:25:15PM +0900, Namhyung Kim wrote:
> On Fri, 14 Mar 2014 15:00:06 +0100, Jiri Olsa wrote:
> > +	if (!mg) {
> > +		struct thread *leader = thread__get_leader(thread);
> > +
> > +		if (!leader)
> > +			return NULL;
> > +
> > +		if (leader->mg)
> > +			mg = leader->mg;
> > +		else
> > +			mg = thread__map_groups_alloc(leader);
> > +
> > +		if (leader != thread)
> > +			thread->mg = mg;
> > +
> > +		mg->refcnt++;
> 
> What's the value of mg->refcnt here in case of leader != thread and
> leader->mg was not allocated originally?  I think it's 1 - but shouldn't
> it be 2 since it's referenced from both of leader and the thread now?

right you are..

I need to initialize refcnt to 1 in thread__map_groups_alloc
and increase it only for the '(leader != thread)' case

I'll add some test for this

thanks,
jirka
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