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    SubjectRe: [PATCH] perf tools: session: avoid infinite loop
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    On 17/09/15 18:41, Mark Rutland wrote:
    > Hi,
    >
    > On Wed, Sep 16, 2015 at 09:54:54PM +0100, Arnaldo Carvalho de Melo wrote:
    >> Em Wed, Sep 16, 2015 at 06:18:49PM +0100, Mark Rutland escreveu:
    >>> This has been observed to result in an exit-time hang when counting
    >>> rare/unschedulable events with perf record, and can be triggered
    >>> artificially with the script below:
    >>>
    >>> ----
    >>> #!/bin/sh
    >>> printf "REPRO: launching perf\n";
    >>> ./perf record -e software/config=9/ sleep 1 &
    >>> PERF_PID=$!;
    >>> sleep 0.002;
    >>> kill -2 $PERF_PID;
    >>> printf "REPRO: waiting for perf (%d) to exit...\n" "$PERF_PID";
    >>> wait $PERF_PID;
    >>> printf "REPRO: perf exited\n";
    >>> ----
    >>
    >> So, I run it here, without this patch, and get:
    >>
    >> [root@zoo ~]# time ./repro.sh
    >> REPRO: launching perf
    >> REPRO: waiting for perf (766) to exit...
    >> [ perf record: Woken up 1 times to write data ]
    >> [ perf record: Captured and wrote 0.015 MB perf.data ]
    >> REPRO: perf exited
    >> real 0m1.060s
    >> user 0m0.018s
    >> sys 0m0.037s
    >
    > [...]
    >
    >> What am I doing wrong? Trying to reproduce this before even looking at
    >> the patch :-)
    >
    > I suspect you have a shinier computer than I do! ;)
    >

    I imagine you would also need to contrive not to write any synthesized MMAP
    or COMM events i.e. no access to /proc perhaps?



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