Re: [PATCH 2/2] perf: Userspace software event and ioctl

[Pawel Moll]

On Mon, 2014-09-29 at 16:32 +0100, Peter Zijlstra wrote:
> Also none of the many words above describe
> PERF_SAMPLE_USERSPACE_EVENT(), wth is that about?

Hopefully description of the v2 makes better job in this:

http://thread.gmane.org/gmane.linux.kernel/1793272/focus=4813

where it's already called "UEVENT" and was generated by write().

Before you get into this, though, the most important outcomes of both v1
and v2 discussions:

* Ingo suggested prctl(PR_TRACE_UEVENT, type, size, data, 0) as the way
of generating such events (so the tracee doesn't have to know the fd to
do ioctl); Frederic seems to have the same on his mind.

* Namhyung proposed sticking the userspace-originating events into the
buffer as PERF_RECORD_UEVENT rather then PERF_SAMPLE_UEVENT.

Working on making both happen now.

Pawel

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