Hi Vince, On Tue, 10 Dec 2013 14:44:52 -0500 (EST), Vince Weaver wrote: > Hello, > > "perf list" listing of hardware events doesn't work on older ARM devices. > The change enabling event detection: > > commit b41f1cec91c37eeea6fdb15effbfa24ea0a5536b > Author: Namhyung Kim <[email protected]> > 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 <[email protected]> > Signed-off-by: Vince Weaver <[email protected]> > > diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c > index 6de6f89..07b6e2d 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; > @@ -1099,8 +1099,24 @@ 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; > perf_evsel__delete(evsel); > + > + 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. > + * > + */ > + attr.exclude_kernel = 1; > + evsel = perf_evsel__new(&attr);
It seems you need to check the return value. But I'd rather suggest re-using existing evsel then. :) Other than that, it looks good to me. Thanks, Namhyung > + > + ret = perf_evsel__open(evsel, NULL, &tmap.map) >= 0; > + perf_evsel__delete(evsel); > + } > } > > return ret; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
