On Mon, Oct 3, 2016 at 2:42 PM, Geert Uytterhoeven <[email protected]> wrote:
> Hi Rob,
>
> On Mon, Oct 3, 2016 at 8:25 PM, Rob Herring <[email protected]> wrote:
>> On Thu, Sep 29, 2016 at 10:31 AM, Geert Uytterhoeven
>> <[email protected]> wrote:
>>> The port->console flag is always false, as uart_console() is called
>>> before the serial console has been registered.
>>
>> I'm not seeing how that is. Everything uart_console() depends on
>> (port->cons, port->cons->index, and port->line) should be set already.
>> Maybe you pass in -1 for index which gets changed to 0 is the only
>> thing I can see. Is doing that valid if you have multiple ports?
>
> Isn't .index always initialized to -1, and set to the actual line number when
> the console is registered? That's how I remember it from when
> register_console() was introduced (in 2.1)...
Okay, the index is also set and gets marked enabled when specified on
the command line (or DT).
>>> Hence for a serial port used as the console, uart_tty_port_shutdown()
>>> will still be called when userspace closes the port, powering it down.
>>> This will lead to a system lock up when the serial console driver writes
>>> to the serial port's registers.
>>>
>>> To fix this, move the setting of port->console after the call to
>>> uart_configure_port(), which registers the serial console.
>>>
>>> Fixes: 761ed4a94582ab29 ("tty: serial_core: convert uart_close to use
>>> tty_port_close")
>>> Reported-by: Niklas Söderlund <[email protected]>
>>> Reported-by: Takeshi Kihara <[email protected]>
>>> Signed-off-by: Geert Uytterhoeven <[email protected]>
>>> ---
>>> RFC because of the comment "If this port is a console, then the spinlock
>>> is already initialised", and the pre-existing code calling
>>> uart_console() before uart_configure_port().
>>
>> So the spinlock is initialized twice which is probably harmless? If
>> the spinlock was initialized by the console, then the index would
>> probably not be -1.
>
> Shouldn't a double initialization cause a warning, with DEBUG_SPINLOCK=y
> (which I have enabled)?
I though only missing init caused warnings.
Anyway, we can't really re-order things as uart_configure_port uses
the spinlock. This has existed this way for some time and is all an
independent of my change and your fix. So for your fix:
Acked-by: Rob Herring <[email protected]>
Rob
