perf: regression with PERF_EVENT_IOC_REFRESH

From: Vince Weaver
Date: Mon May 23 2011 - 16:05:12 EST


the changeset 2e939d1d perf: Limit event refresh to sampling event

changes the behavior of

before the changeset, you could have a counter group where only one of the
subevents was sampling. PERF_EVENT_IOC_REFRESH would correctly enable
sampling for only that subevent.

With the changeset applied, this fails with EINVALID. Now you can only
sample in a group leader.

Was this an intended change? It breaks various of our PAPI regression
tests that worked fine before the change was committed.

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