[perfmon2] task_cpu cannot attach

[Dan U. <up...@vi...>]

I'm trying to monitor some multithreaded applications and I just found
the task_cpu example tool.  I can't get it to attach to any program
though, single or multithreaded, even something as simple as ls:

$ ./task_cpu -- /bin/ls
task_cpu: cannot attach event0 PERF_COUNT_HW_CPU_CYCLES: Permission denied

However, task_smpl and task work fine.  Is something special required
to get task_cpu to work?

-dan