Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1289681

Re: [PATCH v0 3/5] perf: Introduce instruction trace filtering

Show all headers | View raw

Peter Zijlstra <peterz@infradead.org> writes:

> On Fri, Dec 11, 2015 at 03:36:36PM +0200, Alexander Shishkin wrote:
>> +static int perf_event_itrace_filters_setup(struct perf_event *event)
>> +{
>> +	int ret;
>> +
>> +	/*
>> +	 * We can't use event_function_call() here, because that would
>> +	 * require ctx::mutex, but one of our callers is called with
>> +	 * mm::mmap_sem down, which would cause an inversion, see bullet
>> +	 * (2) in put_event().
>> +	 */
>> +	do {
>> +		if (READ_ONCE(event->state) != PERF_EVENT_STATE_ACTIVE) {
>> +			ret = event->pmu->itrace_filter_setup(event);
>> +			break;
>
> So this is tricky, if its not active it can be any moment, there is
> nothing serializing against that.

Indeed. But we should be able to call pmu::itrace_filter_setup()
multiple times, so if after this we re-check that the event is still
inactive, we can return, otherwise proceed with the cross-call. Does
this make sense?

>
>> +		}
>> +
>> +		/* matches smp_wmb() in event_sched_in() */
>> +		smp_rmb();
>> +
>> +		ret = cpu_function_call(READ_ONCE(event->oncpu),
>> +					__perf_event_itrace_filters_setup, event);
>
> This otoh, running with IRQs disabled on the CPU the thing is active on
> guarantees it will not become inactive -- nothing can come in and switch
> it off.
>
>> +	} while (ret == -EAGAIN);
>> +
>> +	return ret;
>> +}
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[PATCH v0 3/5] perf: Introduce instruction trace filtering Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2015-12-11 14:40 +0100
  Re: [PATCH v0 3/5] perf: Introduce instruction trace filtering Peter Zijlstra <peterz@infradead.org> - 2015-12-11 15:10 +0100
    Re: [PATCH v0 3/5] perf: Introduce instruction trace filtering Mark Rutland <mark.rutland@arm.com> - 2015-12-11 15:30 +0100
      Re: [PATCH v0 3/5] perf: Introduce instruction trace filtering Peter Zijlstra <peterz@infradead.org> - 2015-12-11 16:00 +0100
        Re: [PATCH v0 3/5] perf: Introduce instruction trace filtering Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2015-12-11 16:20 +0100
    Re: [PATCH v0 3/5] perf: Introduce instruction trace filtering Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2015-12-11 15:30 +0100
  Re: [PATCH v0 3/5] perf: Introduce instruction trace filtering Peter Zijlstra <peterz@infradead.org> - 2015-12-11 16:00 +0100
    Re: [PATCH v0 3/5] perf: Introduce instruction trace filtering Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2015-12-11 16:20 +0100
  Re: [PATCH v0 3/5] perf: Introduce instruction trace filtering Peter Zijlstra <peterz@infradead.org> - 2015-12-11 16:10 +0100
    Re: [PATCH v0 3/5] perf: Introduce instruction trace filtering Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2015-12-11 16:30 +0100
      Re: [PATCH v0 3/5] perf: Introduce instruction trace filtering Peter Zijlstra <peterz@infradead.org> - 2015-12-11 16:40 +0100
        Re: [PATCH v0 3/5] perf: Introduce instruction trace filtering Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2015-12-11 16:50 +0100
          Re: [PATCH v0 3/5] perf: Introduce instruction trace filtering Peter Zijlstra <peterz@infradead.org> - 2015-12-11 17:10 +0100
            Re: [PATCH v0 3/5] perf: Introduce instruction trace filtering Peter Zijlstra <peterz@infradead.org> - 2015-12-11 18:10 +0100
    Re: [PATCH v0 3/5] perf: Introduce instruction trace filtering Peter Zijlstra <peterz@infradead.org> - 2015-12-11 16:30 +0100
  Re: [PATCH v0 3/5] perf: Introduce instruction trace filtering Peter Zijlstra <peterz@infradead.org> - 2015-12-11 16:10 +0100
  Re: [PATCH v0 3/5] perf: Introduce instruction trace filtering Peter Zijlstra <peterz@infradead.org> - 2015-12-11 16:10 +0100
    Re: [PATCH v0 3/5] perf: Introduce instruction trace filtering Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2015-12-11 16:20 +0100
      Re: [PATCH v0 3/5] perf: Introduce instruction trace filtering Peter Zijlstra <peterz@infradead.org> - 2015-12-11 16:40 +0100
    Re: [PATCH v0 3/5] perf: Introduce instruction trace filtering Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2015-12-11 17:10 +0100
  Re: [PATCH v0 3/5] perf: Introduce instruction trace filtering Peter Zijlstra <peterz@infradead.org> - 2015-12-11 16:20 +0100
  Re: [PATCH v0 3/5] perf: Introduce instruction trace filtering Peter Zijlstra <peterz@infradead.org> - 2015-12-11 16:30 +0100
    Re: [PATCH v0 3/5] perf: Introduce instruction trace filtering Peter Zijlstra <peterz@infradead.org> - 2015-12-11 18:10 +0100
      Re: [PATCH v0 3/5] perf: Introduce instruction trace filtering Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2015-12-11 18:20 +0100
        Re: [PATCH v0 3/5] perf: Introduce instruction trace filtering Peter Zijlstra <peterz@infradead.org> - 2015-12-11 23:40 +0100
  Re: [PATCH v0 3/5] perf: Introduce instruction trace filtering Peter Zijlstra <peterz@infradead.org> - 2015-12-11 18:00 +0100
    Re: [PATCH v0 3/5] perf: Introduce instruction trace filtering Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2015-12-11 18:20 +0100
  Re: [PATCH v0 3/5] perf: Introduce instruction trace filtering Mathieu Poirier <mathieu.poirier@linaro.org> - 2015-12-11 19:20 +0100
    Re: [PATCH v0 3/5] perf: Introduce instruction trace filtering Peter Zijlstra <peterz@infradead.org> - 2015-12-11 23:50 +0100

csiph-web