linux-kernel - Re: [PATCH Not-for-merge 40/40] perf tools: Disable thread refcount due to bug

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Date:	Mon, 18 May 2015 21:21:31 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Jiri Olsa <jolsa@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Andi Kleen <andi@...stfloor.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH Not-for-merge 40/40] perf tools: Disable thread refcount
 due to bug

On Sun, May 17, 2015 at 10:23:36PM -0300, Arnaldo Carvalho de Melo wrote:
> Em Mon, May 18, 2015 at 09:30:55AM +0900, Namhyung Kim escreveu:
> > This makes thread mg sharing test failed due to not decrement
> > thread->refcnt on thread__put().
> 
> I fixed this one already:
> 
> https://git.kernel.org/cgit/linux/kernel/git/acme/linux.git/commit/?h=perf/core&id=8b00f46951bed1edd9c5cb9d9adb62d28bbe7623
> 
> No?

I meant that I added this patch not to segfault caused by the thread
refcount, but as a side-effect it makes thread_mg_sharing test failed
due to non-decremented refcount.

As of 70923bd26c73 ("perf tools: Make flex/bison calls honour V=1")
I can reproduce the segfault.

Thanks,
Namhyung


>  
> > Not-signed-off-by: Namhyung Kim <namhyung@...nel.org>
> > ---
> >  tools/perf/util/thread.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/tools/perf/util/thread.c b/tools/perf/util/thread.c
> > index 702f12dc5a90..dc5ec9a5cca1 100644
> > --- a/tools/perf/util/thread.c
> > +++ b/tools/perf/util/thread.c
> > @@ -163,7 +163,7 @@ struct thread *thread__get(struct thread *thread)
> >  
> >  void thread__put(struct thread *thread)
> >  {
> > -	if (thread && atomic_dec_and_test(&thread->refcnt)) {
> > +	if (thread && atomic_dec_and_test(&thread->refcnt) && 0) {
> >  		if (!RB_EMPTY_NODE(&thread->rb_node)) {
> >  			struct machine *machine = thread->mg->machine;
> >  
> > -- 
> > 2.4.0
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