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Date:   Thu, 17 Mar 2022 10:43:11 +0200 (EET)
From:   =?ISO-8859-15?Q?Ilpo_J=E4rvinen?= <ilpo.jarvinen@linux.intel.com>
To:     Wander Lairson Costa <wander@redhat.com>
cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jiri Slaby <jirislaby@kernel.org>,
        Johan Hovold <johan@kernel.org>,
        "Maciej W. Rozycki" <macro@orcam.me.uk>,
        Serge Semin <fancer.lancer@gmail.com>,
        Lukas Wunner <lukas@wunner.de>,
        =?ISO-8859-15?Q?Pali_Roh=E1r?= <pali@kernel.org>,
        "open list:SERIAL DRIVERS" <linux-serial@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>, rostedt@goodmis.org,
        senozhatsky@chromium.org, andre.goddard@gmail.com,
        sudipm.mukherjee@gmail.com, andy.shevchenko@gmail.com,
        David.Laight@aculab.com, jonathanh@nvidia.com, phil@raspberrypi.com
Subject: Re: [PATCH v4 5/5] serial/8250: Only use fifo after the port is
 initialized in console_write
In-Reply-To: <20220316143646.13301-6-wander@redhat.com>
Message-ID: <2f3d386-b82a-9ae1-eaba-f2123b1346f8@linux.intel.com>
References: <20220316143646.13301-1-wander@redhat.com> <20220316143646.13301-6-wander@redhat.com>
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On Wed, 16 Mar 2022, Wander Lairson Costa wrote:

> The serial driver set the value of uart_8250_port.fcr in the function
> serial8250_config_port, but only writes the value to the controller
> register later in the initalization code.
> 
> That opens a small window in which is not safe to use the fifo for
> console write.
> 
> Make sure the port is initialized correctly before reading the FCR
> cached value.
> 
> Unfortunately, I lost track of who originally reported the issue. If
> s/he is reading this, please speak up so I can give you the due credit.
> 
> Signed-off-by: Wander Lairson Costa <wander@redhat.com>
> ---
>  drivers/tty/serial/8250/8250_port.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
> index 4acf620be241..7e2227161555 100644
> --- a/drivers/tty/serial/8250/8250_port.c
> +++ b/drivers/tty/serial/8250/8250_port.c
> @@ -3416,6 +3416,7 @@ void serial8250_console_write(struct uart_8250_port *up, const char *s,
>  		!(up->capabilities & UART_CAP_MINI) &&
>  		up->tx_loadsz > 1 &&
>  		(up->fcr & UART_FCR_ENABLE_FIFO) &&
> +		test_bit(TTY_PORT_INITIALIZED, &port->state->port.iflags) &&
>  		/*
>  		 * After we put a data in the fifo, the controller will send
>  		 * it regardless of the CTS state. Therefore, only use fifo

So it looks like 2-5 just contain your development history and should all 
be merged to 1/5 (perhaps with Co-developed-by: tags where appropriate).

And please don't just merge them "silently" there w/o describing in the 
message _why_ you ended up doing the things the way you did in the end.
The messages you've written for patches 2-5 will serve you as great source 
material (with small mods, obviously).


-- 
 i.