[igt-dev] [PATCH i-g-t] i915/perf_pmu: Fix perf fd leak

[Tvrtko Ursulin]

On 13/10/2020 11:04, Chris Wilson wrote:
> Quoting Tvrtko Ursulin (2020-10-13 10:46:12)
>> From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
>>
>> As it turns out opening the perf fd in group mode still produces separate
>> file descriptors for all members of the group, which in turn need to be
>> closed manually to avoid leaking them.
> 
> Hmm. That caught me by surprise, but yes while close(group) does call
> free_event() on all its children [aiui], it will not remove the fd and
> each event does receive its own fd. And since close(child) will call
> into perf_event_release, we do have to keep the fd alive until the end.
>   
>> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
>> ---
>>   tests/i915/perf_pmu.c | 130 +++++++++++++++++++++++++-----------------
>>   1 file changed, 78 insertions(+), 52 deletions(-)
>>
>> diff --git a/tests/i915/perf_pmu.c b/tests/i915/perf_pmu.c
>> index 873b275dca6b..6f8bec28d274 100644
>> --- a/tests/i915/perf_pmu.c
>> +++ b/tests/i915/perf_pmu.c
>> @@ -475,7 +475,8 @@ busy_check_all(int gem_fd, const struct intel_execution_engine2 *e,
>>   
>>          end_spin(gem_fd, spin, FLAG_SYNC);
>>          igt_spin_free(gem_fd, spin);
>> -       close(fd[0]);
>> +       for (i = 0; i < num_engines; i++)
>> +               close(fd[i]);
> 
> close_group(fd, num_engines) ?

I am not too keen on that since there is local open_group which does not 
operate on the fd array. Making open_group manage the array and count 
crossed my mind but it felt a bit too much.

Regards,

Tvrtko