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Re: [tip:perf/core] perf/core: Check return value of the perf_event_read() IPI

From Vince Weaver <vincent.weaver@maine.edu>
Newsgroups linux.kernel
Subject Re: [tip:perf/core] perf/core: Check return value of the perf_event_read() IPI
Date 2016-08-29 15:20 +0200
Message-ID <sbuDL-7Mi-3@gated-at.bofh.it> (permalink)
References (3 earlier) <s8RGx-3cc-3@gated-at.bofh.it> <s8SMh-3Ra-3@gated-at.bofh.it> <s8UO5-56V-1@gated-at.bofh.it> <sbsiB-6dl-21@gated-at.bofh.it> <sbuu6-7IC-25@gated-at.bofh.it>
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On Mon, 29 Aug 2016, Peter Zijlstra wrote:

> 
> The best I can come up with is something like:
> 
> 
> 	do {
> 		state = READ_ONCE(event->state);
> 		if (state != ACTIVE)
> 			break;
> 		smp_rmb();
> 		cpu = READ_ONCE(event->cpu);
> 		smp_rmb();
> 	} while (READ_ONCE(event->state) != state);
> 
> 
> And I suppose perf_event_restart() should do the same thing... Let me
> ponder this a wee bit more.

the perf_fuzzer trips over this warning fairly regularly too, so once you 
have a patch you're happy with I can give it a test.  

I ordered a whole crate of null modem cables so I've got a whole bunch of 
serial consoles ready and raring to go.  Maybe I can find out how the 
fuzzer crashes the new skylake machine, it doesn't leave anything useful 
in the syslog.

Vince

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Thread

Re: [tip:perf/core] perf/core: Check return value of the  perf_event_read() IPI Peter Zijlstra <peterz@infradead.org> - 2016-08-29 12:50 +0200
  Re: [tip:perf/core] perf/core: Check return value of the  perf_event_read() IPI Peter Zijlstra <peterz@infradead.org> - 2016-08-29 15:10 +0200
    Re: [tip:perf/core] perf/core: Check return value of the perf_event_read()  IPI Vince Weaver <vincent.weaver@maine.edu> - 2016-08-29 15:20 +0200
    Re: [tip:perf/core] perf/core: Check return value of the  perf_event_read() IPI Jiri Olsa <jolsa@redhat.com> - 2016-08-29 21:00 +0200
      Re: [tip:perf/core] perf/core: Check return value of the  perf_event_read() IPI Peter Zijlstra <peterz@infradead.org> - 2016-08-30 08:50 +0200
        Re: [tip:perf/core] perf/core: Check return value of the  perf_event_read() IPI Peter Zijlstra <peterz@infradead.org> - 2016-08-30 09:30 +0200
          Re: [tip:perf/core] perf/core: Check return value of the  perf_event_read() IPI Jiri Olsa <jolsa@redhat.com> - 2016-08-30 11:50 +0200
    Re: [tip:perf/core] perf/core: Check return value of the  perf_event_read() IPI Stephane Eranian <eranian@google.com> - 2016-08-30 18:30 +0200
      Re: [tip:perf/core] perf/core: Check return value of the  perf_event_read() IPI Peter Zijlstra <peterz@infradead.org> - 2016-09-02 10:40 +0200

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