Messages in this thread | | | From | Vince Weaver <> | Date | Fri, 11 Jan 2019 16:52:22 -0500 (EST) | Subject | Re: perf: rdpmc bug when viewing all procs on remote cpu |
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On Thu, 10 Jan 2019, Vince Weaver wrote:
> On Thu, 10 Jan 2019, Vince Weaver wrote: > > > On Thu, 10 Jan 2019, Vince Weaver wrote: > > > > > However if you create an all-process attached to CPU event: > > > perf_event_open(attr, -1, X, -1, 0); > > > the mmap event index is set as if this were a valid event and so the rdpmc > > > succeeds even though it shouldn't (we're trying to read an event value > > > on a remote cpu with a local rdpmc).
so on further looking at the code, it doesn't appear that rdpmc events are explicitly marked as unavailable in the attach-cpu or attach-pid case, it's just by luck the check for PERF_EVENT_STATE_ACTIVE catches most of the cases?
should an explicit check be added to zero out userpg->index in cases where the event being measured is running on a different core?
Vince
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