Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get the selected hardware PMU conuter

Peter Zijlstra
2015-07-17T11:56:22Z

On Fri, Jul 17, 2015 at 01:55:05PM +0200, Peter Zijlstra wrote:
> On Fri, Jul 17, 2015 at 07:45:02PM +0800, Wangnan (F) wrote:
>
> > >Depends on what all you need, if you need full perf events to work then
> > >yes perf_event_read_value() is your only option.
> > >
> > >But note that that requires scheduling, so you cannot actually use it
> > >for tracing purposes etc..
>
> > What you mean "full perf events"? Even with your code some event still not
> > work?
>
> The code I posted only works for events that do not have inherit set.
> And only works from IRQ/NMI context for events that monitor the current
> task or the current CPU (although that needs a little extra code still).
>
> Anything else and it does not work (correctly).

Scratch that from NMI, for that to work we need more magic still.