Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get the selected hardware PMU conuter

From	"Wangnan (F)" <wangnan0@huawei.com>
Newsgroups	linux.kernel
Subject	Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get the selected hardware PMU conuter
Date	2015-07-17 14:10 +0200
Message-ID	<pNcCK-4Yl-1@gated-at.bofh.it> (permalink)
References	(3 earlier) <pNc9I-4aY-15@gated-at.bofh.it> <pNc9I-4aY-13@gated-at.bofh.it> <pNcjo-4ml-5@gated-at.bofh.it> <pNct4-4xC-13@gated-at.bofh.it> <pNct4-4xC-19@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw


On 2015/7/17 19:56, Peter Zijlstra wrote:
> On Fri, Jul 17, 2015 at 01:55:05PM +0200, Peter Zijlstra wrote:
>> On Fri, Jul 17, 2015 at 07:45:02PM +0800, Wangnan (F) wrote:
>>
>>>> Depends on what all you need, if you need full perf events to work then
>>>> yes perf_event_read_value() is your only option.
>>>>
>>>> But note that that requires scheduling, so you cannot actually use it
>>>> for tracing purposes etc..
>>> What you mean "full perf events"? Even with your code some event still not
>>> work?
>> The code I posted only works for events that do not have inherit set.
>> And only works from IRQ/NMI context for events that monitor the current
>> task or the current CPU (although that needs a little extra code still).
>>
>> Anything else and it does not work (correctly).
> Scratch that from NMI, for that to work we need more magic still.
The scheduling you said is caused by

mutex_lock(&event->child_mutex)

right?

What about replacing it to mutex_trylock() and simply return an error
if it read from a BPF program?

Thank you.

--
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/

Thread

[RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get the selected hardware PMU conuter kaixu xia <xiakaixu@huawei.com> - 2015-07-17 12:50 +0200
  Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get  the selected hardware PMU conuter Peter Zijlstra <peterz@infradead.org> - 2015-07-17 13:10 +0200
    Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get  the selected hardware PMU conuter Peter Zijlstra <peterz@infradead.org> - 2015-07-17 13:40 +0200
    Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get  the selected hardware PMU conuter Peter Zijlstra <peterz@infradead.org> - 2015-07-17 13:40 +0200
      Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get  the selected hardware PMU conuter "Wangnan (F)" <wangnan0@huawei.com> - 2015-07-17 13:50 +0200
        Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get  the selected hardware PMU conuter Peter Zijlstra <peterz@infradead.org> - 2015-07-17 14:00 +0200
          Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get  the selected hardware PMU conuter Peter Zijlstra <peterz@infradead.org> - 2015-07-17 14:00 +0200
            Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get  the selected hardware PMU conuter "Wangnan (F)" <wangnan0@huawei.com> - 2015-07-17 14:10 +0200
              Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get  the selected hardware PMU conuter "Wangnan (F)" <wangnan0@huawei.com> - 2015-07-17 14:10 +0200
              Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get  the selected hardware PMU conuter Peter Zijlstra <peterz@infradead.org> - 2015-07-17 14:20 +0200
                Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get  the selected hardware PMU conuter "Wangnan (F)" <wangnan0@huawei.com> - 2015-07-17 14:40 +0200
                Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get  the selected hardware PMU conuter Peter Zijlstra <peterz@infradead.org> - 2015-07-17 14:50 +0200
                Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get  the selected hardware PMU conuter Peter Zijlstra <peterz@infradead.org> - 2015-07-17 14:50 +0200
                Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get the selected hardware PMU conuter pi3orama <pi3orama@163.com> - 2015-07-17 15:10 +0200
                Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get  the selected hardware PMU conuter Peter Zijlstra <peterz@infradead.org> - 2015-07-17 15:30 +0200
                Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get the selected hardware PMU conuter pi3orama <pi3orama@163.com> - 2015-07-17 15:50 +0200
    Re: [RFC PATCH 5/6] bpf: Implement function bpf_read_pmu() that get  the selected hardware PMU conuter "Wangnan (F)" <wangnan0@huawei.com> - 2015-07-17 13:40 +0200

csiph-web