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    SubjectRe: [PATCH] perf top: Fix a race in callchain handling

    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?

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