linux-kernel - Re: [PATCH] serial: samsung: fix the inconsistency in spinlock

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Message-ID: <56C603E9.9050307@hurleysoftware.com>
Date:	Thu, 18 Feb 2016 09:48:25 -0800
From:	Peter Hurley <peter@...leysoftware.com>
To:	Anand Moon <linux.amoon@...il.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.com>
Cc:	linux-serial@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] serial: samsung: fix the inconsistency in spinlock

Hi Anand,

On 02/18/2016 09:40 AM, Anand Moon wrote:
> From: Anand Moon <linux.amoon@...il.com>
> 
> changes fix the correct order of the spin_lock_irqrestore/save.
> 
> Signed-off-by: Anand Moon <linux.amoon@...il.com>
> ---
>  drivers/tty/serial/samsung.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/tty/serial/samsung.c b/drivers/tty/serial/samsung.c
> index d72cd73..96fe14d 100644
> --- a/drivers/tty/serial/samsung.c
> +++ b/drivers/tty/serial/samsung.c
> @@ -759,9 +759,9 @@ static irqreturn_t s3c24xx_serial_tx_chars(int irq, void *id)
>  	}
>  
>  	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS) {
> -		spin_unlock(&port->lock);
> +		spin_unlock_irqrestore(&port->lock, flags);
>  		uart_write_wakeup(port);
> -		spin_lock(&port->lock);
> +		spin_lock_irqsave(&port->lock, flags);

This driver shouldn't be dropping the spin lock at for write wakeup.
If this is causing lock-ups in a line discipline, the line discipline
needs fixed.

Regards,
Peter Hurley


>  	}
>  
>  	if (uart_circ_empty(xmit))
>