Date: Sat, 5 May 2012 20:53:19 -0300
From: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Namhyung Kim <namhyung@gmail.com>, Paul Mackerras <paulus@samba.org>,
        Ingo Molnar <mingo@redhat.com>, LKML <linux-kernel@vger.kernel.org>,
        Frederic Weisbecker <fweisbec@gmail.com>
Subject: Re: [PATCH] perf top: Fix a race in callchain handling
Message-ID: <20120505235319.GB2150@infradead.org>
References: <1336231388-12347-1-git-send-email-namhyung@gmail.com>
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Em Sat, May 05, 2012 at 08:22:47PM +0200, Peter Zijlstra escreveu:
> On Sun, 2012-05-06 at 00:23 +0900, Namhyung Kim wrote:
> > +       static struct callchain_cursor cursor;
> 
> This just begs to become another concurrency problem. If anybody manages
> to call multiple hists__collapse_insert_entry() concurrently you're
> again up some creek without no paddle.
> 
> Adding global state is never a good option when dealing with
> concurrency.

But it seems to fix the current issue, so thanks to Namhyung for
following up on the report and David Ahern for reporting that it was a
cross thread corruption (Namhyung, was your work based on that report?).

I'm looking how to get that fixed with Peter concerns addressed.

First testing Namhyung patch with -F 100000 tho :-)

- Arnaldo
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