linux-kernel - Re: [BUG] perf: can not resolve symbols for forked threads

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Message-ID: <20140624104213.GL19860@laptop.programming.kicks-ass.net>
Date:	Tue, 24 Jun 2014 12:42:13 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Tony Lu <zlu@...era.com>
Cc:	Paul Mackerras <paulus@...ba.org>, Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Chris Metcalf <cmetcalf@...era.com>
Subject: Re: [BUG] perf: can not resolve symbols for forked threads

On Tue, Jun 24, 2014 at 06:47:38AM +0000, Tony Lu wrote:
> >That pthread_exit() is the problem; this results in:
> >
> >29456 pts/23   Zl     0:00          |               \_ [hello] <defunct>
> >
> >You want to wait for the threads to complete using pthread_join().
> >
> >I suspect the defunct state hides the process.
> 
> Yes, using pthread_join() can workaround this problem.
> Does that mean the parent thread can not exit before the child threads? It still seems like a perf bug.

So we scan /proc at record start to acquire the state for the existing
tasks, it might be defunct tasks simply aren't there anymore, in which
case there's nothing we can do.

But I haven't checked..

That said, yes it would be nice if we could cure this.
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