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    Subject[PATCH 01/22] perf evlist: Reference count the cpu and thread maps at set_maps()
    Date
    From: Arnaldo Carvalho de Melo <acme@redhat.com>

    We were dropping the reference we possibly held but not obtaining one
    for the new maps, which we will drop at perf_evlist__delete(), fix it.

    This was caught by Steven Noonan in some of the machines which would
    produce this output when caught by glibc debug mechanisms:

    $ sudo perf test 21
    21: Test object code reading :***
    Error in `perf': corrupted double-linked list: 0x00000000023ffcd0 ***
    ======= Backtrace: =========
    /usr/lib/libc.so.6(+0x72055)[0x7f25be0f3055]
    /usr/lib/libc.so.6(+0x779b6)[0x7f25be0f89b6]
    /usr/lib/libc.so.6(+0x7a0ed)[0x7f25be0fb0ed]
    /usr/lib/libc.so.6(__libc_calloc+0xba)[0x7f25be0fceda]
    perf(parse_events_lex_init_extra+0x38)[0x4cfff8]
    perf(parse_events+0x55)[0x4a0615]
    perf(perf_evlist__config+0xcf)[0x4eeb2f]
    perf[0x479f82]
    perf(test__code_reading+0x1e)[0x47ad4e]
    perf(cmd_test+0x5dd)[0x46452d]
    perf[0x47f4e3]
    perf(main+0x603)[0x42c723]
    /usr/lib/libc.so.6(__libc_start_main+0xf0)[0x7f25be0a1610]
    perf(_start+0x29)[0x42c859]

    Further investigation using valgrind led to the reference count imbalance fixed
    in this patch.

    Reported-and-Tested-by: Steven Noonan <steven@uplinklabs.net>
    Report-Link: http://lkml.kernel.org/r/CAKbGBLjC2Dx5vshxyGmQkcD+VwiAQLbHoXA9i7kvRB2-2opHZQ@mail.gmail.com
    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>
    Fixes: f30a79b012e5 ("perf tools: Add reference counting for cpu_map object")
    Link: http://lkml.kernel.org/n/tip-j0u1bdhr47sa511sgg76kb8h@git.kernel.org
    Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
    ---
    tools/perf/util/evlist.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
    index d81f13de2476..a7eb0eae9938 100644
    --- a/tools/perf/util/evlist.c
    +++ b/tools/perf/util/evlist.c
    @@ -1181,12 +1181,12 @@ void perf_evlist__set_maps(struct perf_evlist *evlist, struct cpu_map *cpus,
    */
    if (cpus != evlist->cpus) {
    cpu_map__put(evlist->cpus);
    - evlist->cpus = cpus;
    + evlist->cpus = cpu_map__get(cpus);
    }

    if (threads != evlist->threads) {
    thread_map__put(evlist->threads);
    - evlist->threads = threads;
    + evlist->threads = thread_map__get(threads);
    }

    perf_evlist__propagate_maps(evlist);
    --
    2.5.0
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