perf tools: Fix locale handling in pmu parsing

Ingo reported regression on display format of big numbers, which is
missing separators (in default perf stat output).

 triton:~/tip> perf stat -a sleep 1
         ...
         127008602      cycles                    #    0.011 GHz
         279538533      stalled-cycles-frontend   #  220.09% frontend cycles idle
         119213269      instructions              #    0.94  insn per cycle

This is caused by recent change:

  perf stat: Check existence of frontend/backed stalled cycles

that added call to pmu_have_event, that subsequently calls
perf_pmu__parse_scale, which has a bug in locale handling.

The lc string returned from setlocale, that we use to store old locale
value, may be allocated in static storage. Getting a dynamic copy to
make it survive another setlocale call.

  $ perf stat ls
         ...
         2,360,602      cycles                    #    3.080 GHz
         2,703,090      instructions              #    1.15  insn per cycle
           546,031      branches                  #  712.511 M/sec

Committer note:

Since the patch introducing the regression didn't made to perf/core,
move it to just before where the regression was introduced, so that we
don't break bisection for this feature.
Reported-by: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20160303095348.GA24511@krava.redhat.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/pmu.c

@@ -123,6 +123,17 @@ static int perf_pmu__parse_scale(struct perf_pmu_alias *alias, char *dir, char *
 	 */
 	lc = setlocale(LC_NUMERIC, NULL);
 
+	/*
+	 * The lc string may be allocated in static storage,
+	 * so get a dynamic copy to make it survive setlocale
+	 * call below.
+	 */
+	lc = strdup(lc);
+	if (!lc) {
+		ret = -ENOMEM;
+		goto error;
+	}
+
 	/*
 	 * force to C locale to ensure kernel
 	 * scale string is converted correctly.
@@ -135,6 +146,8 @@ static int perf_pmu__parse_scale(struct perf_pmu_alias *alias, char *dir, char *
 	/* restore locale */
 	setlocale(LC_NUMERIC, lc);
 
+	free((char *) lc);
+
 	ret = 0;
 error:
 	close(fd);