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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/
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