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    Subject[PATCH 13/40] perf trace: Introduce filter_loop_pids()
    Date
    From: Arnaldo Carvalho de Melo <acme@redhat.com>

    No change in functionality, just to make clearer that what we want when
    filtering the tracer pid in a system wide tracing session is to avoid a
    feedback loop.

    This also paves the way for a more interesting loop avoidance algorithm,
    one that tries to figure out if we are in a ssh session, xterm, etc.

    Cc: Adrian Hunter <adrian.hunter@intel.com>
    Cc: David Ahern <dsahern@gmail.com>
    Cc: Jiri Olsa <jolsa@kernel.org>
    Cc: Namhyung Kim <namhyung@kernel.org>
    Cc: Wang Nan <wangnan0@huawei.com>
    Link: http://lkml.kernel.org/n/tip-5fcttc5kdjkcyp9404ezkuy9@git.kernel.org
    Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
    ---
    tools/perf/builtin-trace.c | 12 +++++++++++-
    1 file changed, 11 insertions(+), 1 deletion(-)

    diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
    index 9e74e675d7cb..0ba36f08efd8 100644
    --- a/tools/perf/builtin-trace.c
    +++ b/tools/perf/builtin-trace.c
    @@ -2239,6 +2239,16 @@ static int trace__set_ev_qualifier_filter(struct trace *trace)
    goto out;
    }

    +static int trace__set_filter_loop_pids(struct trace *trace)
    +{
    + int nr = 1;
    + pid_t pids[32] = {
    + getpid(),
    + };
    +
    + return perf_evlist__set_filter_pids(trace->evlist, nr, pids);
    +}
    +
    static int trace__run(struct trace *trace, int argc, const char **argv)
    {
    struct perf_evlist *evlist = trace->evlist;
    @@ -2362,7 +2372,7 @@ static int trace__run(struct trace *trace, int argc, const char **argv)
    if (trace->filter_pids.nr > 0)
    err = perf_evlist__set_filter_pids(evlist, trace->filter_pids.nr, trace->filter_pids.entries);
    else if (thread_map__pid(evlist->threads, 0) == -1)
    - err = perf_evlist__set_filter_pid(evlist, getpid());
    + err = trace__set_filter_loop_pids(trace);

    if (err < 0)
    goto out_error_mem;
    --
    2.9.4
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