linux-kernel - PERF_EVENT_IOC_SET

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Date:	Tue, 01 Oct 2013 22:11:56 +0300
From:	Adrian Hunter <adrian.hunter@...el.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Ingo Molnar <mingo@...nel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	linux-kernel@...r.kernel.org, "Kleen, Andi" <andi.kleen@...el.com>,
	"Shishkin, Alexander" <alexander.shishkin@...el.com>
Subject: PERF_EVENT_IOC_SET_OUTPUT

Hi

It does not seem possible to use set-output between
task contexts of different types (e.g. a software event
to a hardware event)

If you look at perf_event_set_output():

           /*
            * If its not a per-cpu rb, it must be the same task.
            */
           if (output_event->cpu == -1 && output_event->ctx != event->ctx)
                   goto out;

ctx (perf_event_context) won't be the same for events
of different types.  Is this restriction necessary?

Regards
Adrian
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