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Subject[patch v3] perf tools: perf list broken on ARM

OK, here's an updated version that reuses evsel and hopefully doesn't leak
memory like the previous patch I posted.


"perf list" listing of hardware events doesn't work on older ARM devices.
The change enabling event detection:

commit b41f1cec91c37eeea6fdb15effbfa24ea0a5536b
Author: Namhyung Kim <namhyung.kim@lge.com>
Date: Tue Aug 27 11:41:53 2013 +0900

perf list: Skip unsupported events


uses the following code in tools/perf/util/parse-events.c:

struct perf_event_attr attr = {
.type = type,
.config = config,
.disabled = 1,
.exclude_kernel = 1,
};

On ARM machines pre-dating the Cortex-A15 this doesn't work, as
these machines don't support .exclude_kernel. So starting with 3.12
"perf list" does not report any hardware events at all on older
machines (seen on Rasp-Pi, Pandaboard, Beagleboard, etc).

This version of the patch makes changes suggested by Namhyung Kim
to check for EACCESS and retry (instead of just dropping
the exclude_kernel) so we can properly handle machines where
/proc/sys/kernel/perf_event_paranoid is set to 2.

Reported-by: Chad Paradis <chad.paradis@umit.maine.edu>
Signed-off-by: Vince Weaver <vincent.weaver@maine.edu>

diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index 6de6f89..1fa98b9 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -1082,12 +1082,12 @@ int is_valid_tracepoint(const char *event_string)
static bool is_event_supported(u8 type, unsigned config)
{
bool ret = true;
+ int open_return;
struct perf_evsel *evsel;
struct perf_event_attr attr = {
.type = type,
.config = config,
.disabled = 1,
- .exclude_kernel = 1,
};
struct {
struct thread_map map;
@@ -1099,7 +1099,20 @@ static bool is_event_supported(u8 type, unsigned config)

evsel = perf_evsel__new(&attr);
if (evsel) {
- ret = perf_evsel__open(evsel, NULL, &tmap.map) >= 0;
+ open_return = perf_evsel__open(evsel, NULL, &tmap.map);
+ ret = open_return >= 0;
+
+ if (open_return == -EACCES) {
+ /*
+ * This happens if the paranoid value
+ * /proc/sys/kernel/perf_event_paranoid is set to 2
+ * Re-run with exclude_kernel set; we don't do that
+ * by default as some ARM machines do not support it.
+ *
+ */
+ evsel->attr.exclude_kernel = 1;
+ ret = perf_evsel__open(evsel, NULL, &tmap.map) >= 0;
+ }
perf_evsel__delete(evsel);
}


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