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SubjectRe: [PATCH] perf parse-events: Use strcmp to compare the PMU name
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On 30/04/2020 12:15, Jiri Olsa wrote:

+

> On Thu, Apr 30, 2020 at 09:54:18AM +0100, John Garry wrote:
>> On 30/04/2020 09:45, Jiri Olsa wrote:
>>> On Thu, Apr 30, 2020 at 08:36:18AM +0800, Jin Yao wrote:
>>>> A big uncore event group is split into multiple small groups which
>>>> only include the uncore events from the same PMU. This has been
>>>> supported in the commit 3cdc5c2cb924a ("perf parse-events: Handle
>>>> uncore event aliases in small groups properly").
>>>>
>>>> If the event's PMU name starts to repeat, it must be a new event.
>>>> That can be used to distinguish the leader from other members.
>>>> But now it only compares the pointer of pmu_name
>>>> (leader->pmu_name == evsel->pmu_name).
>>>>
>>>> If we use "perf stat -M LLC_MISSES.PCIE_WRITE -a" on cascadelakex,
>>>> the event list is:
>>>>
>>>> evsel->name evsel->pmu_name
>>>> ---------------------------------------------------------------
>>>> unc_iio_data_req_of_cpu.mem_write.part0 uncore_iio_4 (as leader)
>>>> unc_iio_data_req_of_cpu.mem_write.part0 uncore_iio_2
>>>> unc_iio_data_req_of_cpu.mem_write.part0 uncore_iio_0
>>>> unc_iio_data_req_of_cpu.mem_write.part0 uncore_iio_5
>>>> unc_iio_data_req_of_cpu.mem_write.part0 uncore_iio_3
>>>> unc_iio_data_req_of_cpu.mem_write.part0 uncore_iio_1
>>>> unc_iio_data_req_of_cpu.mem_write.part1 uncore_iio_4
>>>> ......
>>>>
>>>> For the event "unc_iio_data_req_of_cpu.mem_write.part1" with
>>>> "uncore_iio_4", it should be the event from PMU "uncore_iio_4".
>>>> It's not a new leader for this PMU.
>>>>
>>>> But if we use "(leader->pmu_name == evsel->pmu_name)", the check
>>>> would be failed and the event is stored to leaders[] as a new
>>>> PMU leader.
>>>>
>>>> So this patch uses strcmp to compare the PMU name between events.
>>>>
>>>> Fixes: 3cdc5c2cb924a ("perf parse-events: Handle uncore event aliases in small groups properly")
>>>> Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
>>>
>>> looks good, any chance we could have automated test
>>> for this uncore leader setup logic? like maybe the way
>>> John did the pmu-events tests? like test will trigger
>>> only when there's the pmu/events in the system
>>>
>>> Acked-by: Jiri Olsa <jolsa@redhat.com>
>>>
>>> thanks,
>>> jirka
>>
>> Hi jirka,
>>
>> JFYI, this is effectively the same patch as I mentioned to you, which was a
>> fix for the same WARN:
>>
>> https://lore.kernel.org/linux-arm-kernel/1587120084-18990-2-git-send-email-john.garry@huawei.com/
>>
>> but I found that it "fixed" d4953f7ef1a2 ("perf parse-events: Fix 3 use
>> after frees found with clang ASANutil/parse-events.c"), based on bisect
>> breakage
>
> hum right.. sorry I did not recalled that, there's
> also the warn removal in here, could you guys also
> plz sync on the fixes clauses?

I just thought that it fixes d4953f7ef1a2, as I found that the pointer
equality fails from that commit. I assume the parse-events code was
sound before then (in that regard). That's all I know :)

Thanks!

>
> thanks,
> jirka
>
>>
>> cheers
>>
>>>
>>>
>>>> ---
>>>> tools/perf/util/parse-events.c | 5 ++---
>>>> 1 file changed, 2 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
>>>> index 10107747b361..786eddb6a097 100644
>>>> --- a/tools/perf/util/parse-events.c
>>>> +++ b/tools/perf/util/parse-events.c
>>>> @@ -1629,12 +1629,11 @@ parse_events__set_leader_for_uncore_aliase(char *name, struct list_head *list,
>>>> * event. That can be used to distinguish the leader from
>>>> * other members, even they have the same event name.
>>>> */
>>>> - if ((leader != evsel) && (leader->pmu_name == evsel->pmu_name)) {
>>>> + if ((leader != evsel) &&
>>>> + !strcmp(leader->pmu_name, evsel->pmu_name)) {
>>>> is_leader = false;
>>>> continue;
>>>> }
>>>> - /* The name is always alias name */
>>>> - WARN_ON(strcmp(leader->name, evsel->name));
>>>> /* Store the leader event for each PMU */
>>>> leaders[nr_pmu++] = (uintptr_t) evsel;
>>>> --
>>>> 2.17.1
>>>>
>>>
>>> .
>>>
>>
>
> .
>

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