netdev - Re: [PATCH next] loopback: fix lockdep splat

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Date:   Wed, 3 Jul 2019 10:45:36 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Mahesh Bandewar <maheshb@...gle.com>
Cc:     Netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        David Miller <davem@...emloft.net>,
        Mahesh Bandewar <mahesh@...dewar.net>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>
Subject: Re: [PATCH next] loopback: fix lockdep splat

Hi Mahesh,

s/lockdep/rcu/ in the subject.

On Wed, Jul 3, 2019 at 8:16 AM Mahesh Bandewar <maheshb@...gle.com> wrote:
> dev_init_scheduler() and dev_activate() expect the caller to
> hold RTNL. Since we don't want blackhole device to be initialized
> per ns, we are initializing at init.
>
> [    3.855027] Call Trace:
> [    3.855034]  dump_stack+0x67/0x95
> [    3.855037]  lockdep_rcu_suspicious+0xd5/0x110
> [    3.855044]  dev_init_scheduler+0xe3/0x120
> [    3.855048]  ? net_olddevs_init+0x60/0x60
> [    3.855050]  blackhole_netdev_init+0x45/0x6e
> [    3.855052]  do_one_initcall+0x6c/0x2fa
> [    3.855058]  ? rcu_read_lock_sched_held+0x8c/0xa0
> [    3.855066]  kernel_init_freeable+0x1e5/0x288
> [    3.855071]  ? rest_init+0x260/0x260
> [    3.855074]  kernel_init+0xf/0x180
> [    3.855076]  ? rest_init+0x260/0x260
> [    3.855078]  ret_from_fork+0x24/0x30
>
> Fixes: 4de83b88c66 ("loopback: create blackhole net device similar to loopack.")
> Reported-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> Cc: Eric Dumazet <edumazet@...gle.com>
> Signed-off-by: Mahesh Bandewar <maheshb@...gle.com>

Thanks, that got rid of the rcu splat.

Tested-by: Geert Uytterhoeven <geert+renesas@...der.be>

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds