netdev - Re: [PATCH bpf-next 3/4] bpf: fix lockdep false positive in bpf_prog

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Message-ID: <20190130193241.4gkbc7zuo3m7r3ll@ast-mbp.dhcp.thefacebook.com>
Date:   Wed, 30 Jan 2019 11:32:43 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Alexei Starovoitov <ast@...nel.org>, davem@...emloft.net,
        daniel@...earbox.net, edumazet@...gle.com, jannh@...gle.com,
        netdev@...r.kernel.org, kernel-team@...com
Subject: Re: [PATCH bpf-next 3/4] bpf: fix lockdep false positive in
 bpf_prog_register

On Wed, Jan 30, 2019 at 11:10:58AM +0100, Peter Zijlstra wrote:
> 
> Why do you say this is not possible? All you need is 3 CPUs, one doing a
> CPU online, one doing a perf ioctl() and one doing that
> bpf_probe_register().

yeah. indeed. I'm impressed that lockdep figured it out
while I missed it manually looking through the code and stack traces.
Will reword the commit log.