On Tue, 2012-07-31 at 09:16 +0200, Ingo Molnar wrote:

* Peter Zijlstra [off-list ref] wrote:

quoted

On Fri, 2012-07-27 at 13:53 +0200, Ingo Molnar wrote:

quoted

quoted

Bloating the interface for something that is already well 
possible is.

There's no 'bloat' worth speaking off: a single bit out of 
an already allocated bitmap, plus a single check in an 
already existing loop,

Uhm, no. The existing prctl() loop is over the fd's the task 
owns, you want a loop over the fd's that monitor you. This 
needs new prctl()s at the very least.

We could add a new prctl if you think, but I thought to not 
complicate it and offer it as a simple extension of the 
semantics to loop over active events. No existing binary's 
behavior will change.

It muddles up the semantics of the existing prctl()s though.

Ideally we'd simply remove the current ones though, I don't think
anybody actually uses them and as an owner you actually have all the fds
to call ioctl() on.

This would let us get rid of the entire event->owner, event->owner_entry
and task->perf_event_list mess. See perf_event_exit_task() and
perf_release() for why I'd love that crap to go away.