From 88fee52e58ca14d8465b614774ed0bf08e1a7790 Mon Sep 17 00:00:00 2001 From: Vince Weaver Date: Mon, 30 Dec 2013 15:39:45 -0500 Subject: [PATCH] perf list: Fix checking for supported events on older kernels "perf list" listing of hardware events doesn't work on older ARM devices. The change enabling event detection: commit b41f1cec91c37eeea6fdb15effbfa24ea0a5536b Author: Namhyung Kim 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 Signed-off-by: Vince Weaver Acked-by: Namhyung Kim Cc: Chad Paradis Cc: Ingo Molnar Cc: Namhyung Kim Cc: Paul Mackerras Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1312301536150.28814@vincent-weaver-1.um.maine.edu Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/parse-events.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c index d248fca6d7ed..1e15df10a88c 100644 --- a/tools/perf/util/parse-events.c +++ b/tools/perf/util/parse-events.c @@ -1091,12 +1091,12 @@ 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; @@ -1108,7 +1108,20 @@ 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); } -- 2.20.1