linux-kernel - Re: [PATCH 1/1] tty: serial: owl: Initialize lock before registering port

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Date:   Fri, 29 May 2020 13:53:54 +0200
From:   Andreas Färber <afaerber@...e.de>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Cristian Ciocaltea <cristian.ciocaltea@...il.com>
Cc:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Jiri Slaby <jslaby@...e.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-serial@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-actions@...ts.infradead.org
Subject: Re: [PATCH 1/1] tty: serial: owl: Initialize lock before registering
 port

Am 29.05.20 um 13:34 schrieb Greg Kroah-Hartman:
> On Fri, May 29, 2020 at 02:06:47PM +0300, Cristian Ciocaltea wrote:
>> Running a lockdep-enabled kernel leads to the following splat when
>> probing the owl-uart driver:
>>
>> [    1.271784] b0124000.serial: ttyOWL2 at MMIO 0xb0124000 (irq = 22, base_baud = 1500000) is a owl-uart
>> [    1.281226] INFO: trying to register non-static key.
>> [    1.286179] the code is fine but needs lockdep annotation.
>> [    1.291648] turning off the locking correctness validator.
>> [    1.297125] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.7.0-rc7+ #70
>> [    1.303462] Hardware name: Generic DT based system
>> [    1.308268] [<80111d3c>] (unwind_backtrace) from [<8010c9b8>] (show_stack+0x10/0x14)
>> [    1.316003] [<8010c9b8>] (show_stack) from [<805016b4>] (dump_stack+0xb4/0xe0)
>> [    1.323218] [<805016b4>] (dump_stack) from [<80182dec>] (register_lock_class+0x25c/0x8f4)
>> [    1.331391] [<80182dec>] (register_lock_class) from [<8017ee34>] (__lock_acquire+0xb4/0x2ee4)
>> [    1.339901] [<8017ee34>] (__lock_acquire) from [<8018291c>] (lock_acquire+0x424/0x4c8)
>> [    1.347813] [<8018291c>] (lock_acquire) from [<808597b0>] (_raw_spin_lock_irqsave+0x54/0x68)
>> [    1.356242] [<808597b0>] (_raw_spin_lock_irqsave) from [<80582e94>] (uart_add_one_port+0x384/0x510)
>> [    1.365276] [<80582e94>] (uart_add_one_port) from [<8058b4d0>] (owl_uart_probe+0x1bc/0x248)
>> [    1.373621] [<8058b4d0>] (owl_uart_probe) from [<8059c0e4>] (platform_drv_probe+0x48/0x94)
>> [    1.381874] [<8059c0e4>] (platform_drv_probe) from [<805997c4>] (really_probe+0x200/0x470)
>> [    1.390123] [<805997c4>] (really_probe) from [<80599c80>] (driver_probe_device+0x16c/0x1bc)
>> [    1.398461] [<80599c80>] (driver_probe_device) from [<80599f18>] (device_driver_attach+0x44/0x60)
>> [    1.407317] [<80599f18>] (device_driver_attach) from [<8059a078>] (__driver_attach+0x144/0x14c)
>> [    1.416000] [<8059a078>] (__driver_attach) from [<805978ac>] (bus_for_each_dev+0x5c/0xb4)
>> [    1.424162] [<805978ac>] (bus_for_each_dev) from [<8059896c>] (bus_add_driver+0x118/0x204)
>> [    1.432410] [<8059896c>] (bus_add_driver) from [<8059ae6c>] (driver_register+0xbc/0xf8)
>> [    1.440405] [<8059ae6c>] (driver_register) from [<80c1fd24>] (owl_uart_init+0x20/0x40)
>> [    1.448313] [<80c1fd24>] (owl_uart_init) from [<801021d8>] (do_one_initcall+0x184/0x3a4)
>> [    1.456399] [<801021d8>] (do_one_initcall) from [<80c01100>] (kernel_init_freeable+0x264/0x2e4)
>> [    1.465085] [<80c01100>] (kernel_init_freeable) from [<80850a88>] (kernel_init+0x8/0x110)
>> [    1.473249] [<80850a88>] (kernel_init) from [<80100114>] (ret_from_fork+0x14/0x20)
>> [    1.480800] Exception stack(0xee8bdfb0 to 0xee8bdff8)
>> [    1.485841] dfa0:                                     00000000 00000000 00000000 00000000
>> [    1.494002] dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
>> [    1.502162] dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
>> [    1.508914] printk: console [ttyOWL2] enabled
>>
>> The locking issue occurs in uart_configure_port() when trying to
>> guard the call to set_mctrl().
>>
>> uart_add_one_port() should normally initialize the spinlock via
>> uart_port_spin_lock_init(), but it never happens because the port is
>> detected as a console and, as a consequence, the spinlock is expected
>> to be already initialized.
>>
>> The commit a3cb39d258ef
>> ("serial: core: Allow detach and attach serial device for console")
>> changed the lock initialization logic to assume the spinlock is
>> initialized even if the console is not enabled.
>>
>> Therefore, initialize the lock explicitly in owl_uart_probe(), before
>> attempting to invoke uart_add_one_port().
>>
>> Fixes: a3cb39d258ef ("serial: core: Allow detach and attach serial device for console")
>> Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@...il.com>
>> ---
>>   drivers/tty/serial/owl-uart.c | 2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/drivers/tty/serial/owl-uart.c b/drivers/tty/serial/owl-uart.c
>> index c149f8c30007..c2fa2f15d50a 100644
>> --- a/drivers/tty/serial/owl-uart.c
>> +++ b/drivers/tty/serial/owl-uart.c
>> @@ -705,6 +705,8 @@ static int owl_uart_probe(struct platform_device *pdev)
>>   	owl_uart_ports[pdev->id] = owl_port;
>>   	platform_set_drvdata(pdev, owl_port);
>>   
>> +	spin_lock_init(&owl_port->port.lock);
>> +
>>   	ret = uart_add_one_port(&owl_uart_driver, &owl_port->port);
>>   	if (ret)
>>   		owl_uart_ports[pdev->id] = NULL;
> 
> Ugh, another one :(
> 
> Thanks for this, will queue this up now.

Thanks. If this is the expected pattern now, I'll also have to update 
in-flight patches, such as Sunplus.

Regards,
Andreas

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