linux-kernel - Re: [BUG] segfault in perf-top -- thread refcnt

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Message-ID: <20150330131724.GC24063@kernel.org>
Date:	Mon, 30 Mar 2015 10:17:24 -0300
From:	Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	David Ahern <dsahern@...il.com>, Jiri Olsa <jolsa@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Stephane Eranian <eranian@...gle.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [BUG] segfault in perf-top -- thread refcnt

Em Mon, Mar 30, 2015 at 12:22:20PM +0200, Jiri Olsa escreveu:
> On Mon, Mar 30, 2015 at 10:07:37AM +0200, Jiri Olsa wrote:
> looks like race among __machine__findnew_thread and thread__put
> over the machine->threads rb_tree insert/removal
> 
> is there a reason why thread__put does not erase itself from machine->threads?

IIRC it has to first pass thru:

machine__remove_thread() that will remove the reference count obtained
when inserting the thread on the rbtree and move it to the dead_threads
list, where it will stay until the last reference count obtained when
adding the thread to some hist_entry is finally dropped via
thread__put().

- Arnaldo
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