Re: [PATCH] perf evsel: Skip group members without fds when walking a group

[TAKANO Mitsuhiro <takano32@gmail.com>]

Thanks for testing this on Zen 3, and for the EBADF detail: it says the
member is being grouped against a descriptor that is not a perf event at
all, which is what the patch stops the walk from doing.

On the counting improvement you describe, I would rather not fold it into
this patch.  Returning -1 from get_group_fd() for a leader that has no
perf event changes what the kernel is asked for: the members stop using
PERF_FORMAT_GROUP and start being read on their own, so on top of the
patch that stops the crash it becomes a change in how the group is
created, and it needs its own explanation and its own testing across the
PMU types that can lead a group.

Would you post it as a follow-up on top of this one?  You have the
measurement I do not: the "{user_time,cycles,instructions}" case counting
on Zen 3.  If you would rather have it here, say so and I will post a v2
that carries your diff with a Suggested-by, but then the changelog is
about a behaviour change rather than a segfault fix and I would want a
run of the group tests on a second host before asking anyone to take it.