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

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Date:   Wed, 1 Jul 2020 18:28:15 +0100
From:   "Lad, Prabhakar" <prabhakar.csengg@...il.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        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>,
        Biju Das <biju.das.jz@...renesas.com>
Subject: Re: [PATCH] serial: sh-sci: Initialize spinlock for uart console

Hi Geert,

On Wed, Jul 1, 2020 at 6:17 PM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
>
> 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...
>
I have attached .config for your reference.

Cheers,
--Prabhakar

> 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

Download attachment "serial_defconfig" of type "application/octet-stream" (161804 bytes)