linux-kernel - Re: [PATCH v2 net-next] bpf: fix bpf_perf_event

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Date:	Wed, 21 Oct 2015 22:00:12 -0700
From:	Alexei Starovoitov <ast@...mgrid.com>
To:	"Wangnan (F)" <wangnan0@...wei.com>,
	"David S. Miller" <davem@...emloft.net>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	He Kuang <hekuang@...wei.com>, Kaixu Xia <xiakaixu@...wei.com>,
	Daniel Borkmann <daniel@...earbox.net>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 net-next] bpf: fix bpf_perf_event_read() helper

On 10/21/15 9:49 PM, Wangnan (F) wrote:
> After applying this patch I'm unable to use perf passing perf_event
> again like this:

please do not top post and trim your replies.

>   # perf record -a -e evt=cycles -e
> ./test_config_map.c/maps.pmu_map.event=evt/ --exclude-perf ls
>
> With -v it output:
>
> ...
> adding perf_bpf_probe:func_write
> adding perf_bpf_probe:func_write to 0x367d6a0
> add bpf event perf_bpf_probe:func_write_return and attach bpf program 6
> adding perf_bpf_probe:func_write_return
> adding perf_bpf_probe:func_write_return to 0x3a7fc40
> mmap size 528384B
> ERROR: failed to insert value to pmu_map[0]
> ERROR: Apply config to BPF failed: Invalid option for map, add -v to see
> detail
> Opening /sys/kernel/debug/tracing//kprobe_events write=
> ...
>
> Looks like perf sets attr.inherit for cycles? I'll look into this problem.

yes. that's perf default.
How did it even work before?!
I was testing with your samples/bpf/tracex6 that sets inherit to zero.

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