linux-kernel - Re: [PATCH] serial: sh-sci: Initialize spinlock for uart console

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Message-ID: <CAMuHMdWU7kVJMuNMSGxZSjErmj7rB=tvXH3GANmPRjYz+=JP1g@mail.gmail.com>
Date:   Wed, 1 Jul 2020 19:17:36 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Prabhakar <prabhakar.csengg@...il.com>,
        Biju Das <biju.das.jz@...renesas.com>
Subject: Re: [PATCH] serial: sh-sci: Initialize spinlock for uart console

Hi Prabhakar,

On Wed, Jul 1, 2020 at 5:42 PM Lad Prabhakar
<prabhakar.mahadev-lad.rj@...renesas.com> wrote:
> serial core expects the spinlock to be initialized by the controller
> driver for serial console, this patch makes sure the spinlock is
> initialized, fixing the below issue:
>
> [    0.865928] BUG: spinlock bad magic on CPU#0, swapper/0/1
> [    0.865945]  lock: sci_ports+0x0/0x4c80, .magic: 00000000, .owner: <none>/-1, .owner_cpu: 0
> [    0.865955] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.8.0-rc1+ #112
> [    0.865961] Hardware name: HopeRun HiHope RZ/G2H with sub board (DT)
> [    0.865968] Call trace:
> [    0.865979]  dump_backtrace+0x0/0x1d8
> [    0.865985]  show_stack+0x14/0x20
> [    0.865996]  dump_stack+0xe8/0x130
> [    0.866006]  spin_dump+0x6c/0x88
> [    0.866012]  do_raw_spin_lock+0xb0/0xf8
> [    0.866023]  _raw_spin_lock_irqsave+0x80/0xa0
> [    0.866032]  uart_add_one_port+0x3a4/0x4e0
> [    0.866039]  sci_probe+0x504/0x7c8
> [    0.866048]  platform_drv_probe+0x50/0xa0
> [    0.866059]  really_probe+0xdc/0x330
> [    0.866066]  driver_probe_device+0x58/0xb8
> [    0.866072]  device_driver_attach+0x6c/0x90
> [    0.866078]  __driver_attach+0x88/0xd0
> [    0.866085]  bus_for_each_dev+0x74/0xc8
> [    0.866091]  driver_attach+0x20/0x28
> [    0.866098]  bus_add_driver+0x14c/0x1f8
> [    0.866104]  driver_register+0x60/0x110
> [    0.866109]  __platform_driver_register+0x40/0x48
> [    0.866119]  sci_init+0x2c/0x34
> [    0.866127]  do_one_initcall+0x88/0x428
> [    0.866137]  kernel_init_freeable+0x2c0/0x328
> [    0.866143]  kernel_init+0x10/0x108
> [    0.866150]  ret_from_fork+0x10/0x18

Interesting...

How can I reproduce that? I do have CONFIG_DEBUG_SPINLOCK=y.
I'm wondering why haven't we seen this before...

Thanks!

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