Hi Vince,
On Wed, 8 Jan 2014 16:30:17 -0500 (EST), Vince Weaver wrote:
> just checking on the status of this patch. Am I sending it to the wrong
> place? Did it get lost in the post-holiday e-mail purges?
>
> The bug is annoying if you're trying to use perf on ARM systems.
Right, acme, would you please merge this?
Thanks,
Namhyung
>
> On Mon, 30 Dec 2013, Vince Weaver wrote:
>
>>
>> "perf list" listing of hardware events doesn't work on older ARM devices.
>> The change enabling event detection:
>>
>> commit b41f1cec91c37eeea6fdb15effbfa24ea0a5536b
>> Author: Namhyung Kim <namhyung....@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.para...@umit.maine.edu>
>> Signed-off-by: Vince Weaver <vincent.wea...@maine.edu>
>> Acked-by: Namhyung Kim <namhy...@kernel.org>
>>
>> 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);
>> }
>>
>>
>
> Vince Weaver
> vincent.wea...@maine.edu
> http://www.eece.maine.edu/~vweaver/
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