linux-kernel - Re: [PATCH resend] serial_core: Fix pm imbalance on unbind

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Date:	Fri, 21 Mar 2014 14:23:49 +0100
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Peter Hurley <peter@...leysoftware.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.cz>, linux-serial@...r.kernel.org,
	Linux-sh list <linux-sh@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Geert Uytterhoeven <geert+renesas@...ux-m68k.org>
Subject: Re: [PATCH resend] serial_core: Fix pm imbalance on unbind

Hi Peter,

On Fri, Mar 21, 2014 at 2:06 PM, Peter Hurley <peter@...leysoftware.com> wrote:
>> @@ -2681,10 +2683,12 @@ int uart_remove_one_port(struct uart_driver *drv,
>> struct uart_port *uport)
>>         }
>>
>>         /*
>> -        * If the port is used as a console, unregister it
>> +        * If the port is used as a console, unregister it, and power it
>> down
>>          */
>> -       if (uart_console(uport))
>> +       if (uart_console(uport)) {
>>                 unregister_console(uport->cons);
>> +               uart_change_pm(state, UART_PM_STATE_OFF);
>
> Won't this power off the port while tty consoles may still be open?

I didn't see that actually happening.

> I think the right thing here is to unregister_console then set uport->cons =
> NULL
>
> [uport->cons is properly reassigned when/if a port is re-added via
> uart_add_one_port()).]

But indeed, for concistency/symmetry uport->state and uport->cons
should be resend, but that's something separate.

> Then, uart_close() will power off the port when all ttys using the port have
> been closed.

uart_close() won't get that far, so uart_change_pm() won't be called.

See also https://lkml.org/lkml/2014/3/10/651, and my workaround for the
crash https://lkml.org/lkml/2014/3/17/231.

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
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