linux-kernel - Re: [PATCH 4/4] tty: serial: do unlock on a common path in altera_jtaguart_console

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Message-ID: <fdfd4174-37d1-fc0-9a5-57f5bcebbe7f@linux.intel.com>
Date:   Wed, 28 Sep 2022 13:27:45 +0300 (EEST)
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     Jiri Slaby <jslaby@...e.cz>
cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-serial <linux-serial@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Tobias Klauser <tklauser@...tanz.ch>
Subject: Re: [PATCH 4/4] tty: serial: do unlock on a common path in
 altera_jtaguart_console_putc()

On Tue, 27 Sep 2022, Jiri Slaby wrote:

> port->lock is unlocked in each branch in altera_jtaguart_console_putc(),
> so do it before the "if". "status" needs not be under the lock, as the
> register was already read.
> 
> Cc: Tobias Klauser <tklauser@...tanz.ch>
> Signed-off-by: Jiri Slaby <jslaby@...e.cz>
> ---
>  drivers/tty/serial/altera_jtaguart.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/tty/serial/altera_jtaguart.c b/drivers/tty/serial/altera_jtaguart.c
> index ac8ce418de36..c2d154d78e54 100644
> --- a/drivers/tty/serial/altera_jtaguart.c
> +++ b/drivers/tty/serial/altera_jtaguart.c
> @@ -310,11 +310,12 @@ static void altera_jtaguart_console_putc(struct uart_port *port, unsigned char c
>  
>  	spin_lock_irqsave(&port->lock, flags);
>  	while (!altera_jtaguart_tx_space(port, &status)) {
> +		spin_unlock_irqrestore(&port->lock, flags);
> +
>  		if ((status & ALTERA_JTAGUART_CONTROL_AC_MSK) == 0) {
> -			spin_unlock_irqrestore(&port->lock, flags);
>  			return;	/* no connection activity */
>  		}

There braces are now unnecessary.

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>

-- 
 i.


> -		spin_unlock_irqrestore(&port->lock, flags);
> +
>  		cpu_relax();
>  		spin_lock_irqsave(&port->lock, flags);
>  	}
>