linux-kernel - Re: [PATCH 05/15] serial: sc16is7xx: use guards for simple mutex locks

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Message-Id: <20250929202708.c81f114be5286eab259aa4c1@hugovil.com>
Date: Mon, 29 Sep 2025 20:27:08 -0400
From: Hugo Villeneuve <hugo@...ovil.com>
To: Jiri Slaby <jirislaby@...nel.org>
Cc: gregkh@...uxfoundation.org, fvallee@...rea.fr,
 linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org, Hugo Villeneuve
 <hvilleneuve@...onoff.com>
Subject: Re: [PATCH 05/15] serial: sc16is7xx: use guards for simple mutex
 locks

Hi Jiri,

On Mon, 29 Sep 2025 08:09:12 +0200
Jiri Slaby <jirislaby@...nel.org> wrote:

> On 24. 09. 25, 17:37, Hugo Villeneuve wrote:
> > --- a/drivers/tty/serial/sc16is7xx.c
> > +++ b/drivers/tty/serial/sc16is7xx.c
> ...
> > @@ -829,9 +827,6 @@ static bool sc16is7xx_port_irq(struct sc16is7xx_port *s, int portno)
> >   		break;
> >   	}
> >   
> > -out_port_irq:
> > -	mutex_unlock(&one->lock);
> > -
> >   	return rc;
> 
> No need for rc now AFAICT.

You are right, I will remove it in v2.

> 
> >   }
> >   
> > @@ -874,9 +869,8 @@ static void sc16is7xx_tx_proc(struct kthread_work *ws)
> >   	    (port->rs485.delay_rts_before_send > 0))
> >   		msleep(port->rs485.delay_rts_before_send);
> >   
> > -	mutex_lock(&one->lock);
> > +	guard(mutex)(&one->lock);
> >   	sc16is7xx_handle_tx(port);
> > -	mutex_unlock(&one->lock);
> >   }
> >   
> >   static void sc16is7xx_reconf_rs485(struct uart_port *port)
> > @@ -943,9 +937,8 @@ static void sc16is7xx_ms_proc(struct kthread_work *ws)
> >   	struct sc16is7xx_port *s = dev_get_drvdata(one->port.dev);
> >   
> >   	if (one->port.state) {
> > -		mutex_lock(&one->lock);
> > +		guard(mutex)(&one->lock);
> >   		sc16is7xx_update_mlines(one);
> > -		mutex_unlock(&one->lock);
> >   
> >   		kthread_queue_delayed_work(&s->kworker, &one->ms_work, HZ);
> 
> Now the lock is held till here. R U sure it is OK?

Now that you mention it, I am sure its not OK :)

I will restore this one to the original lock/unlock code in V2.

Thank you,
Hugo.