Re: [PATCH v2 net-next 1/3] perf, bpf: Add BPF support to all perf_event types

From	Peter Zijlstra <peterz@infradead.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH v2 net-next 1/3] perf, bpf: Add BPF support to all perf_event types
Date	2017-05-30 21:10 +0200
Message-ID	<tMUGJ-2PS-17@gated-at.bofh.it> (permalink)
References	(2 earlier) <tMp0f-6bg-37@gated-at.bofh.it> <tMpjA-6jW-21@gated-at.bofh.it> <tMSEV-1o1-7@gated-at.bofh.it> <tMSEV-1o1-5@gated-at.bofh.it> <tMUGJ-2PS-19@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Tue, May 30, 2017 at 10:37:46AM -0700, Alexei Starovoitov wrote:
> On 5/30/17 9:51 AM, Peter Zijlstra wrote:

> > I'm not entirely sure I see how that is required. Should per task not
> > already work? The WARN that's there will only trigger if you call them
> > on the wrong task, which is something you shouldn't do anyway.
> 
> The kernel WARN is considered to be a bug of bpf infra. That's the
> reason we do all these checks at map update time and at run-time.
> The bpf program authors should be able to do all possible experiments
> until their scripts work. Dealing with kernel warns and reboots is not
> something user space folks like to do.
> Today bpf_perf_event_read() for per-task events isn't really
> working due to event->oncpu != cpu runtime check in there.
> If we convert warns to returns the existing scripts will continue
> to work as-is and per-task will be possible.

Ah yes.. I always forget that side of things (not ever having seen a
bpf thing working doesn't help either of course).

Let me consider that for a bit..

Thread

[PATCH v2 net-next 0/3] bpf: Add BPF support to all perf_event Alexei Starovoitov <ast@fb.com> - 2017-05-26 08:00 +0200
  [PATCH v2 net-next 2/3] samples/bpf: add samples for more perf event types Alexei Starovoitov <ast@fb.com> - 2017-05-26 08:00 +0200
  [PATCH v2 net-next 3/3] bpf: update perf event helper functions documentation Alexei Starovoitov <ast@fb.com> - 2017-05-26 08:00 +0200
  [PATCH v2 net-next 1/3] perf, bpf: Add BPF support to all perf_event types Alexei Starovoitov <ast@fb.com> - 2017-05-26 08:00 +0200
    Re: [PATCH v2 net-next 1/3] perf, bpf: Add BPF support to all  perf_event types David Miller <davem@davemloft.net> - 2017-05-26 17:00 +0200
    Re: [PATCH v2 net-next 1/3] perf, bpf: Add BPF support to all  perf_event types Peter Zijlstra <peterz@infradead.org> - 2017-05-29 11:20 +0200
      Re: [PATCH v2 net-next 1/3] perf, bpf: Add BPF support to all  perf_event types Peter Zijlstra <peterz@infradead.org> - 2017-05-29 11:40 +0200
        Re: [PATCH v2 net-next 1/3] perf, bpf: Add BPF support to all  perf_event types Peter Zijlstra <peterz@infradead.org> - 2017-05-30 19:00 +0200
          Re: [PATCH v2 net-next 1/3] perf, bpf: Add BPF support to all  perf_event types Peter Zijlstra <peterz@infradead.org> - 2017-05-30 21:10 +0200
            Re: [PATCH v2 net-next 1/3] perf, bpf: Add BPF support to all  perf_event types Peter Zijlstra <peterz@infradead.org> - 2017-06-01 15:40 +0200

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