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bh=hMrZ0Fj8O9t2zoQt5sBCV5iZNG5UmOz4mlK4r+ZvSv4=; b=CF9GzDRCUDgkn7qYR6/0E9lYngsq7wM9NfsEO5Fhxv1MSQ6ZnqhCsV0pzTpSi4PB9z UAN/Kti8g2PsYywvG0xqIr71r66VAGMV42GN3IPA/1MbYxbwazw/VvboH4mrOsuN/pc1 ESrg6GWkA64CN8gCpt+ePtT/QNpF8cycsSFCVu4Q96W9OPzjF0M1CMvViK0XQuEDjrX4 PvCfIDX86936Z3VoQo9yQxufPwj2czv7K6E75J3K81ZeIQdkykIcPY3yV05uG43PzwEt t95tQTO7uzZqpLeScQGbH1EG1xlqd/pRqKvOYQYmmziHSHcTM9Ywmtrbr4XXLYfTCDks 305w== X-Gm-Message-State: AOAM530XA9n5jkQ3SGJO/2m0ol3a+yN2gdzSM3WDBJSYZsyjgto/GTOJ HZGnq8zKozM6BnIp19zeQ+1h+ZHbaE7LQF+196Q= X-Google-Smtp-Source: ABdhPJyF4e3whEm/wKrGvNp5pUH/88OopaC3saaBmqlAoJT+L4iXrqeBT8+JVvd2NCynrZtAOa6+Sq5HjJ34LbyOtQs= X-Received: by 2002:a9d:7dd3:: with SMTP id k19mr15778847otn.43.1593714760853; Thu, 02 Jul 2020 11:32:40 -0700 (PDT) MIME-Version: 1.0 References: <1593618100-2151-1-git-send-email-prabhakar.mahadev-lad.rj@bp.renesas.com> In-Reply-To: From: "Lad, Prabhakar" Date: Thu, 2 Jul 2020 19:32:13 +0100 Message-ID: Subject: Re: [PATCH] serial: sh-sci: Initialize spinlock for uart console To: Geert Uytterhoeven Cc: Greg Kroah-Hartman , Jiri Slaby , Linux-Renesas , "open list:SERIAL DRIVERS" , Linux Kernel Mailing List , Biju Das Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Geert, On Thu, Jul 2, 2020 at 3:39 PM Geert Uytterhoeven wrote: > > Hi Prabhakar, > > On Thu, Jul 2, 2020 at 4:05 PM Lad, Prabhakar > wrote: > > > Hi Geert, > > > > On Thu, Jul 2, 2020 at 1:52 PM Geert Uytterhoeven wrote: > > > > > > Hi Prabhakar, > > > > > > On Thu, Jul 2, 2020 at 1:42 PM Lad, Prabhakar > > > wrote: > > > > On Thu, Jul 2, 2020 at 11:49 AM Lad, Prabhakar > > > > wrote: > > > > > On Thu, Jul 2, 2020 at 10:23 AM Geert Uytterhoeven wrote: > > > > > > On Wed, Jul 1, 2020 at 7:28 PM Lad, Prabhakar > > > > > > wrote: > > > > > > > On Wed, Jul 1, 2020 at 6:17 PM Geert Uytterhoeven wrote: > > > > > > > > On Wed, Jul 1, 2020 at 5:42 PM Lad Prabhakar > > > > > > > > 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: /-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. > > > > > > > > > > > > Thank you! > > > > > > > > > > > > I gave it a try with v5.8-rc1 on Salvator-XS with R-Car H3 ES2.0. > > > > > > However, I couldn't reproduce the issue. > > > > > > Does it happen on that specific board only? Is this serdev-related? > > > > > > Note that I had to disable CONFIG_EXTRA_FIRMWARE, as I don't have the > > > > > > firmware blobs it referenced. Do I need them to trigger the issue? > > > > > > As the .config has a few non-upstream options, do you have any patches > > > > > > applied that might impact the issue? > > > > > > > > > > > Can't think of any patches that might cause an issue, most of it are > > > > > just the DT's and config additions. Nor do firmware blobs should > > > > > affect it. I'll try and reproduce it on M3N and get back to you. > > > > > > > > > I did manage to replicate this issue on M3N (v5.8-rc3 tag with no > > > > modifications), I have attached the config file and also the boot log > > > > without this patch for your reference, after applying this patch I no > > > > more see this issue. > > > > > > Thanks, the boot log finally gave me a clue, and allowed me to reproduce. > > > The issue happens only when adding: > > > > > > console=ttySC0,115200n8 > > > > > Ack tested it on G2H. > > > > > to the kernel command line. Which is something we never did on R-Car > > > Gen3, as the console= parameter had been deprecated by chosen/stdout-path > > > on DT systems long before. > > > > > > As we did use console= before on arm32, and drivers/tty/serial/sh-sci.c > > > never called spinlock_init(), I'm wondering if this spinlock bug is > > > actually a regression in serial_core.c? > > > > > Not sure if it's a regression in serial_core.c as I see some drivers > > calling spin_lock_init(). > > Bisected to commit a3cb39d258efef83 ("serial: core: Allow detach and > attach serial device for console"). > The first change to drivers/tty/serial/serial_core.c is the culprit: > > static inline void uart_port_spin_lock_init(struct uart_port *port) > { > - if (uart_console_enabled(port)) > + if (uart_console(port)) > return; > > spin_lock_init(&port->lock); > > as it now skips the spinlock initialization if a console= parameter > is specified. > > Apparently we're not the only one bitten by that... > Thank you for bisecting through, that explains the culprit. Cheers, --Prabhakar > Gr{oetje,eeting}s, > > Geert > > -- > Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-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