perf: FORMAT_GROUP on attached process stops working in 3.16-rc

[Vince Weaver]

Hello

I noticed in the 3.16-rc kernels that one of my regression tests was 
failing, specifically
	https://github.com/deater/perf_event_tests/blob/master/tests/bugs/read_group_attached.c

This test creates an event group with two events and PERF_FORMAT_GROUP
set.

It creates a child process, stops it, attaches the event group to it, 
starts the events and the child, waits for the child to finish, stops the
events, then reads the value.

In theory a subsequent read from the group leader should return values for 
*both* events (due to PERF_FORMAT_GROUP) but this stopped working, it only 
returns the value for the leader.

I've bisected it down to change: 15a2d4de0eab5 
	"perf: Always destroy groups on exit"

So is this expected behavior due to this patch, or is it a regression?

Thanks,

Vince
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/