Re: [PATCH 3/5] perf tools: Reference count map_groups objects

From: Jiri Olsa <jolsa@redhat.com>
To: David Ahern <dsahern@gmail.com>
Cc: linux-kernel@vger.kernel.org,
	Arnaldo Carvalho de Melo <acme@redhat.com>,
	Adrian Hunter <adrian.hunter@intel.com>,
	Don Zickus <dzickus@redhat.com>,
	Frederic Weisbecker <fweisbec@gmail.com>,
	Mike Galbraith <efault@gmx.de>,
	Namhyung Kim <namhyung@kernel.org>,
	Paul Mackerras <paulus@samba.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Stephane Eranian <eranian@google.com>
Subject: Re: [PATCH 3/5] perf tools: Reference count map_groups objects
Date: Tue, 15 Apr 2014 11:56:58 +0200	[thread overview]
Message-ID: <20140415095657.GC1700@krava.brq.redhat.com> (raw)
In-Reply-To: <534C193A.2000806@gmail.com>

On Mon, Apr 14, 2014 at 11:22:02AM -0600, David Ahern wrote:
> On 4/14/14, 9:52 AM, Jiri Olsa wrote:

SNIP

> >
> >+void map_groups__put(struct map_groups *mg)
> >+{
> >+	if (--mg->refcnt == 0)
> >+		map_groups__delete(mg);
> >+}
> >+
> >  void map_groups__flush(struct map_groups *mg)
> >  {
> >  	int type;
> >diff --git a/tools/perf/util/map.h b/tools/perf/util/map.h
> >index 1073e2d..d6445b2 100644
> >--- a/tools/perf/util/map.h
> >+++ b/tools/perf/util/map.h
> >@@ -59,11 +59,20 @@ struct map_groups {
> >  	struct rb_root	 maps[MAP__NR_TYPES];
> >  	struct list_head removed_maps[MAP__NR_TYPES];
> >  	struct machine	 *machine;
> >+	int		 refcnt;
> >  };
> 
> 
> atomic for refcnt? This is part of a libperf; would be good to
> support multithreaded users.

hum.. I think using atomic type is not enough, we'd need
to make map_groups__put/get atomic as well

not sure what's the support in user space for that.. will check

also not to be negative, but libperf is not thread safe anyway, right? ;-)

thanks,
jirka