Re: [PATCH 3/5] perf_counter: rework ioctl()s

[Paul Mackerras]

Peter Zijlstra writes:

> Corey noticed that ioctl()s on grouped counters didn't work on the whole group.
> This extends the ioctl() interface to take a second argument that is
> interpreted as a flags field. We then provide PERF_IOC_FLAG_GROUP to toggle
> the behaviour.
> 
> Having this flag gives the greatest flexibility, allowing you to individually
> enable/disable/reset counters in a group, or all together.

As far as enable/disable are concerned, I don't think this is really
necessary.  My intention was that if you want to enable/disable a
whole group you just enable/disable the leader and leave all its
siblings enabled, since if the leader is disabled the whole group
can't go on.

Corey's problem was that we have a bug where enabling the leader only
puts the leader on and not the enabled group members.  I meant to send
a patch to fix that ages ago but I got distracted.  I'll send out the
patch shortly.

Paul.
--
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/