linux-kernel - Re: [PATCH] serial: 8250: Fix oops for port->pm on uart_change

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Message-ID: <ZM1VK6hYGYfPN0Rd@smile.fi.intel.com>
Date:   Fri, 4 Aug 2023 22:44:43 +0300
From:   Andy Shevchenko <andriy.shevchenko@...el.com>
To:     Tony Lindgren <tony@...mide.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>, 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-kernel@...r.kernel.org, linux-serial@...r.kernel.org
Subject: Re: [PATCH] serial: 8250: Fix oops for port->pm on uart_change_pm()

On Fri, Aug 04, 2023 at 04:15:51PM +0300, Tony Lindgren wrote:
> Unloading a hardware specific 8250 driver can produce error "Unable to
> handle kernel paging request at virtual address" about ten seconds after
> unloading the driver. This happens on uart_hangup() calling
> uart_change_pm().
> 
> Turns out commit 04e82793f068 ("serial: 8250: Reinit port->pm on port
> specific driver unbind") was only a partial fix. If the hardware specific
> driver has initialized port->pm function, we need to clear port->pm too.
> Just reinitializing port->ops does not do this. Otherwise serial8250_pm()
> will call port->pm() instead of serial8250_do_pm().

Oh, good catch!
Reviewed-by: Andy Shevchenko <andriy.shevchenko@...el.com>

-- 
With Best Regards,
Andy Shevchenko