netdev - Re: [PATCH v2 bpf-next 1/4] bpf: unprivileged BPF access via /dev/bpf

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Message-ID: <CACAyw98VyM8a-h_8jtsNdF0KfK69-AxzRR4K28HVsyUecb0a5Q@mail.gmail.com>
Date:   Mon, 1 Jul 2019 10:34:25 +0100
From:   Lorenz Bauer <lmb@...udflare.com>
To:     Song Liu <songliubraving@...com>
Cc:     Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kernel Team <Kernel-team@...com>, Jann Horn <jannh@...gle.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v2 bpf-next 1/4] bpf: unprivileged BPF access via /dev/bpf

On Fri, 28 Jun 2019 at 20:10, Song Liu <songliubraving@...com> wrote:
> There should be a master thread, no? Can we do that from the master thread at
> the beginning of the execution?

Unfortunately, no. The Go runtime has no such concept. This is all
that is defined about program start up:

  https://golang.org/ref/spec#Program_initialization_and_execution

Salient section:

  Package initialization—variable initialization and the invocation of init
  functions—happens in a single goroutine, sequentially, one package at
  a time. An init function may launch other goroutines, which can run
  concurrently with the initialization code. However, initialization always
  sequences the init functions: it will not invoke the next one until the
  previous one has returned.

This means that at the earliest possible moment for Go code to run,
the scheduler is already active with at least GOMAXPROCS threads.

-- 
Lorenz Bauer  |  Systems Engineer
6th Floor, County Hall/The Riverside Building, SE1 7PB, UK

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