linux-kernel - Re: [PATCH] perf top: Fix a race in callchain handling

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <87vck3ii18.fsf@sejong.aot.lge.com>
Date:	Fri, 11 May 2012 11:10:59 +0900
From:	Namhyung Kim <namhyung.kim@....com>
To:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH] perf top: Fix a race in callchain handling

Hi,

On Mon, 07 May 2012 10:32:22 +0900, Namhyung Kim wrote:
> On Sun, 6 May 2012 15:32:12 -0300, Arnaldo Carvalho de Melo wrote:
>> Em Sun, May 06, 2012 at 11:25:07AM +0900, Namhyung Kim escreveu:
>>> 2012-05-05 (토), 20:53 -0300, Arnaldo Carvalho de Melo:
>>> > I'm looking how to get that fixed with Peter concerns addressed.
>>> 
>>> I guess it's gonna be a non-trivial job. As far as I can see, the hists
>>> code can handle up to two concurrent threads regardless of the callchain
>>> cursor problem. And also guess that other areas of libperf also doesn't
>>> support the true concurrency, right?
>>
>> Right, but making it even less concurrent is something we should avoid
>> 8-)
>>
>> How about this one instead? At least we would be able to, concurrently,
>> process multiple, unrelated hists:
>
> I thought about it before, but it still cannot protect it from accessing
> a hists by multiple concurrent threads. IOW if two threads call the
> function to a same hists at the same time, ->callchain_collapse_cursor
> would still get the race problem - so crashed.
>
> I guess callchain_cursor should be thread-local, eventually. No need to
> make it hist-local IMHO.
>

So, any thoughts?

Thanks,
Namhyung
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/