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Message-ID: <561F0D9D.4000205@huawei.com> Date: Thu, 15 Oct 2015 10:21:17 +0800 From: xiakaixu <xiakaixu@...wei.com> To: Alexei Starovoitov <ast@...mgrid.com> CC: <davem@...emloft.net>, <acme@...nel.org>, <mingo@...hat.com>, <a.p.zijlstra@...llo.nl>, <masami.hiramatsu.pt@...achi.com>, <jolsa@...nel.org>, <daniel@...earbox.net>, <wangnan0@...wei.com>, <linux-kernel@...r.kernel.org>, <pi3orama@....com>, <hekuang@...wei.com>, <netdev@...r.kernel.org> Subject: Re: [PATCH V2 2/2] bpf: control a set of perf events by creating a new ioctl PERF_EVENT_IOC_SET_ENABLER δΊ 2015/10/15 5:28, Alexei Starovoitov ει: > On 10/14/15 5:37 AM, Kaixu Xia wrote: >> + event->p_sample_disable = &enabler_event->sample_disable; > > I don't like it as a concept and it's buggy implementation. > What happens here when enabler is alive, but other event is destroyed? > >> --- a/kernel/trace/bpf_trace.c >> +++ b/kernel/trace/bpf_trace.c >> @@ -221,9 +221,12 @@ static u64 bpf_perf_event_sample_control(u64 r1, u64 index, u64 flag, u64 r4, u6 >> struct bpf_array *array = container_of(map, struct bpf_array, map); >> struct perf_event *event; >> >> - if (unlikely(index >= array->map.max_entries)) >> + if (unlikely(index > array->map.max_entries)) >> return -E2BIG; >> >> + if (index == array->map.max_entries) >> + index = 0; > > what is this hack for ? > > Either use notification and user space disable or > call bpf_perf_event_sample_control() manually for each cpu. I will discard current implemention that controlling a set of perf events by the 'enabler' event. Call bpf_perf_event_sample_control() manually for each cpu is fine. Maybe we can add a loop to control all the events stored in maps by judging the index, OK? > > > > . > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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