Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY maps trace data output when perf sampling

From	pi3orama <pi3orama@163.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY maps trace data output when perf sampling
Date	2015-10-21 16:10 +0200
Message-ID	<qm2fv-5eA-3@gated-at.bofh.it> (permalink)
References	(5 earlier) <qlZUm-1FU-25@gated-at.bofh.it> <qm0dH-22V-9@gated-at.bofh.it> <qm0x4-2Fy-21@gated-at.bofh.it> <qm1Wa-4CG-11@gated-at.bofh.it> <qm25P-4NY-11@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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发自我的 iPhone

> 在 2015年10月21日，下午9:49，Peter Zijlstra <peterz@infradead.org> 写道：
> 
>> On Wed, Oct 21, 2015 at 09:42:12PM +0800, Wangnan (F) wrote:
>> How can an eBPF program access a !local event:
>> 
>> when creating perf event array we don't care which perf event
>> is for which CPU, so perf program can access any perf event in
>> that array.
> 
> So what is stopping the eBPF thing from calling perf_event_read_local()
> on a !local event and triggering a kernel splat?

I can understand the perf_event_read_local() case, but I really can't understand
what is stopping us to write to an atomic field belong to a !local perf event.
Could you please give a further explanation?

Thank you.
> 

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Thread

[PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY maps trace data output when perf sampling Kaixu Xia <xiakaixu@huawei.com> - 2015-10-20 09:30 +0200
  Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling Alexei Starovoitov <ast@plumgrid.com> - 2015-10-21 01:00 +0200
    Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling Peter Zijlstra <peterz@infradead.org> - 2015-10-21 11:20 +0200
      Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling xiakaixu <xiakaixu@huawei.com> - 2015-10-21 12:40 +0200
        Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling Peter Zijlstra <peterz@infradead.org> - 2015-10-21 13:40 +0200
          Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling "Wangnan (F)" <wangnan0@huawei.com> - 2015-10-21 14:00 +0200
            Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling Peter Zijlstra <peterz@infradead.org> - 2015-10-21 14:20 +0200
              Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling "Wangnan (F)" <wangnan0@huawei.com> - 2015-10-21 15:50 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling Peter Zijlstra <peterz@infradead.org> - 2015-10-21 16:00 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY maps trace data output when perf sampling pi3orama <pi3orama@163.com> - 2015-10-21 16:10 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling Peter Zijlstra <peterz@infradead.org> - 2015-10-21 16:10 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY maps trace data output when perf sampling pi3orama <pi3orama@163.com> - 2015-10-21 17:20 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling Peter Zijlstra <peterz@infradead.org> - 2015-10-21 19:00 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling Alexei Starovoitov <ast@plumgrid.com> - 2015-10-21 23:30 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling Peter Zijlstra <peterz@infradead.org> - 2015-10-22 11:10 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling "Wangnan (F)" <wangnan0@huawei.com> - 2015-10-22 12:40 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling Peter Zijlstra <peterz@infradead.org> - 2015-10-23 15:00 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling Peter Zijlstra <peterz@infradead.org> - 2015-10-23 17:20 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling xiakaixu <xiakaixu@huawei.com> - 2015-10-27 07:50 +0100
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling "Wangnan (F)" <wangnan0@huawei.com> - 2015-10-22 05:00 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling Ingo Molnar <mingo@kernel.org> - 2015-10-22 09:50 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling "Wangnan (F)" <wangnan0@huawei.com> - 2015-10-22 10:00 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling Peter Zijlstra <peterz@infradead.org> - 2015-10-22 11:30 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling "Wangnan (F)" <wangnan0@huawei.com> - 2015-10-22 04:10 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling Alexei Starovoitov <ast@plumgrid.com> - 2015-10-22 05:10 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling "Wangnan (F)" <wangnan0@huawei.com> - 2015-10-22 05:20 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling Alexei Starovoitov <ast@plumgrid.com> - 2015-10-22 05:30 +0200
                Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling Peter Zijlstra <peterz@infradead.org> - 2015-10-22 11:50 +0200
      Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling "Wangnan (F)" <wangnan0@huawei.com> - 2015-10-21 13:40 +0200
        Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling Peter Zijlstra <peterz@infradead.org> - 2015-10-21 14:00 +0200
          Re: [PATCH V5 1/1] bpf: control events stored in PERF_EVENT_ARRAY  maps trace data output when perf sampling "Wangnan (F)" <wangnan0@huawei.com> - 2015-10-21 14:10 +0200

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