From mboxrd@z Thu Jan  1 00:00:00 1970
From: Alexei Starovoitov <ast@plumgrid.com>
Subject: Re: [PATCH v3 net-next] bpf: fix bpf_perf_event_read() helper
Date: Thu, 22 Oct 2015 19:30:57 -0700
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 <56299992.8040002@huawei.com>
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Cc: Ingo Molnar <mingo@kernel.org>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	He Kuang <hekuang@huawei.com>, Kaixu Xia <xiakaixu@huawei.com>,
	Daniel Borkmann <daniel@iogearbox.net>, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org
To: "Wangnan (F)" <wangnan0@huawei.com>,
	"David S. Miller" <davem@davemloft.net>
Return-path: <linux-kernel-owner@vger.kernel.org>
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On 10/22/15 7:21 PM, Wangnan (F) wrote:
>> +    if (attr->inherit)
>> +        goto err;
>> +
>
> Since Peter suggest it is pointless for a system-wide perf_event
> has inherit bit set [1], I think it should be safe to enable
> system-wide perf_event pass this check?

here we don't know whether it's system wide or not, so the check
is needed.
The patch is the fix that should have been there from day one.
We must be safe first and relax later.