linux-kernel - Re: [PATCH v12 1/1] serial: core: Start managing serial controllers to enable runtime PM

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Date:   Thu, 1 Jun 2023 11:53:27 +0100
From:   Steven Price <steven.price@....com>
To:     Tony Lindgren <tony@...mide.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Andy Shevchenko <andriy.shevchenko@...el.com>,
        Dhruva Gole <d-gole@...com>,
        Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        John Ogness <john.ogness@...utronix.de>,
        Johan Hovold <johan@...nel.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Vignesh Raghavendra <vigneshr@...com>,
        linux-omap@...r.kernel.org,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org
Subject: Re: [PATCH v12 1/1] serial: core: Start managing serial controllers
 to enable runtime PM

On 01/06/2023 11:44, Tony Lindgren wrote:
> Hi,
> 
> * Steven Price <steven.price@....com> [230601 10:04]:
>> I haven't studied this change in detail, but I assume the bug is that
>> serial_base_port_device_remove() shouldn't be dropping port_mutex. The
>> below hack gets my board booting again.
> 
> You're right. I wonder how I managed to miss that.. Care to post a proper
> fix for this or do you want me to post it?

I'll post a proper fix shortly. Thanks for the confirmation of the fix.

>> Thanks,
>>
>> Steve
>>
>> Hack fix:
>> ----8<----
>> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
>> index 29bd5ede0b25..044e4853341a 100644
>> --- a/drivers/tty/serial/serial_core.c
>> +++ b/drivers/tty/serial/serial_core.c
>> @@ -3234,8 +3234,7 @@ static void serial_core_remove_one_port(struct uart_driver *drv,
>>         wait_event(state->remove_wait, !atomic_read(&state->refcount));
>>         state->uart_port = NULL;
>>         mutex_unlock(&port->mutex);
>> -out:
>> -       mutex_unlock(&port_mutex);
>> +out:;
>>  }
> 
> Seems you can remove out here and just do a return earlier instead of goto.

Yes, this was just the smallest change. I'll do it properly with an
early return in the proper patch.

Thanks,

Steve

> Regards,
> 
> Tony