Re: [tip:perf/core] perf/core: Check return value of the perf_event_read() IPI

[Peter Zijlstra]

On Mon, Aug 29, 2016 at 08:58:41PM +0200, Jiri Olsa wrote:
> couldn't we just call smp_call_function_single(cpu_to_read, __perf_event_read, ...
> once we read oncpu != -1 ?
> 

Yes, and at that point we can simply revert this WARN, because that is
exactly the same.

Which I think is what I'm going to do.

If oncpu is not valid, the sched_out that made it invalid will have
updated the event count and we're good.

All I'll leave is an explicit comment that we've ignored the
smp_call_function_single() return value on purpose.