[tip:perf/core] perf cpu_map: Fix core dump caused by per-socket/ core system-wide stat

[tip-bot for Kan Liang <tipbot@zytor.com>]

Commit-ID:  bc1d03687b9be3a30aab8e8d78c7884449b6e511
Gitweb:     http://git.kernel.org/tip/bc1d03687b9be3a30aab8e8d78c7884449b6e511
Author:     Kan Liang <kan.liang@intel.com>
AuthorDate: Fri, 9 Oct 2015 06:59:23 -0400
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Tue, 20 Oct 2015 15:54:20 -0300

perf cpu_map: Fix core dump caused by per-socket/core system-wide stat

Perf will core dump if --per-socket/core -a are applied for perf stat.

The root cause is that cpu_map__build_map set refcnt of evlist's cpu_map
to 1.  It should set refcnt for the newly created cpu_map, not evlist's
cpu_map.

Here is the example:

  # perf stat -e cycles --per-socket -a sleep 1

   Performance counter stats for 'system wide':

  S0       36         30,196,257      cycles
  S1       28         15,823,536      cycles

       1.001126828 seconds time elapsed

  *** Error in `./perf': corrupted double-linked list: 0x00000000021f9090 ***
  ======= Backtrace: =========
  /lib64/libc.so.6[0x3002e7bbe7]
  /lib64/libc.so.6[0x3002e7d2b5]
  ./perf(perf_evsel__delete+0x28)[0x485bdd]
  ./perf[0x4800e8]
  ./perf(perf_evlist__delete+0x5e)[0x482cd5]
  ./perf(cmd_stat+0xf25)[0x432328]
  ./perf[0x4768e0]
  ./perf[0x476ad6]
  ./perf[0x476b41]
  ./perf(main+0x1d0)[0x476db2]
  /lib64/libc.so.6(__libc_start_main+0xf5)[0x3002e21b45]
  ./perf[0x4202c5]

Signed-off-by: Kan Liang <kan.liang@intel.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Andi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/r/1444388363-35936-1-git-send-email-kan.liang@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/cpumap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/cpumap.c b/tools/perf/util/cpumap.c
index b368453..aa6b490 100644
--- a/tools/perf/util/cpumap.c
+++ b/tools/perf/util/cpumap.c
@@ -285,7 +285,7 @@ int cpu_map__build_map(struct cpu_map *cpus, struct cpu_map **res,
 	/* ensure we process id in increasing order */
 	qsort(c->map, c->nr, sizeof(int), cmp_ids);
 
-	atomic_set(&cpus->refcnt, 1);
+	atomic_set(&c->refcnt, 1);
 	*res = c;
 	return 0;
 }