From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andi Kleen <andi@firstfloor.org>
Subject: Re: perf_event sampling a multithreaded process - ioctl with PERF_EVENT_IOC_SET_OUTPUT fails
Date: Wed, 19 Apr 2017 08:46:23 -0700
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In-Reply-To: <d7635c6e-1d12-52d7-6b9f-b7c08d3a451f@gmail.com> (Daniel John
        FitzGerald's message of "Wed, 19 Apr 2017 11:15:20 -0400")
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To: Daniel John FitzGerald <daniel.j.fitzgerald@gmail.com>
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Daniel John FitzGerald <daniel.j.fitzgerald@gmail.com> writes:
>
> The problem that I am running into is that whenever I attempt to call
> ioctl() with PERF_EVENT_IOC_SET_OUTPUT, I get a -1 response with
> errno==EINVAL.

There are lots of restrictions to PERF_EVENT_IOC_SET_OUTPUT.

Likely you're violating that it has to be on the same CPU or same task.

-Andi