linux-kernel - Re: [PATCH 2/5] use mutex instead of semaphore in the USB gadget serial driver

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Message-Id: <200707131300.52923.david-b@pacbell.net>
Date:	Fri, 13 Jul 2007 13:00:52 -0700
From:	David Brownell <david-b@...bell.net>
To:	Matthias Kaehlcke <matthias.kaehlcke@...il.com>
Cc:	dbrownell@...rs.sourceforge.net,
	linux-usb-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	alborchers@...inerpoint.com
Subject: Re: [PATCH 2/5] use mutex instead of semaphore in the USB gadget serial driver

On Friday 13 July 2007, Matthias Kaehlcke wrote:
> The USB gadget serial driver uses a semaphore as mutex. Use the
> mutex API instead of the (binary) semaphore.
> 
> Signed-off-by: Matthias Kaehlcke <matthias.kaehlcke@...il.com>

ACK (and thanks)

> 
> --
> 
> diff --git a/drivers/usb/gadget/serial.c b/drivers/usb/gadget/serial.c
> index dd33ff0..4192d24 100644
> --- a/drivers/usb/gadget/serial.c
> +++ b/drivers/usb/gadget/serial.c
> @@ -33,6 +33,7 @@
>  #include <linux/device.h>
>  #include <linux/tty.h>
>  #include <linux/tty_flip.h>
> +#include <linux/mutex.h>
>  
>  #include <asm/byteorder.h>
>  #include <asm/io.h>
> @@ -258,7 +259,7 @@ static const char *EP_IN_NAME;
>  static const char *EP_OUT_NAME;
>  static const char *EP_NOTIFY_NAME;
>  
> -static struct semaphore	gs_open_close_sem[GS_NUM_PORTS];
> +static struct mutex gs_open_close_lock[GS_NUM_PORTS];
>  
>  static unsigned int read_q_size = GS_DEFAULT_READ_Q_SIZE;
>  static unsigned int write_q_size = GS_DEFAULT_WRITE_Q_SIZE;
> @@ -595,7 +596,7 @@ static int __init gs_module_init(void)
>  	tty_set_operations(gs_tty_driver, &gs_tty_ops);
>  
>  	for (i=0; i < GS_NUM_PORTS; i++)
> -		sema_init(&gs_open_close_sem[i], 1);
> +		mutex_init(&gs_open_close_lock[i]);
>  
>  	retval = tty_register_driver(gs_tty_driver);
>  	if (retval) {
> @@ -635,7 +636,7 @@ static int gs_open(struct tty_struct *tty, struct file *file)
>  	struct gs_port *port;
>  	struct gs_dev *dev;
>  	struct gs_buf *buf;
> -	struct semaphore *sem;
> +	struct mutex *mtx;
>  	int ret;
>  
>  	port_num = tty->index;
> @@ -656,10 +657,10 @@ static int gs_open(struct tty_struct *tty, struct file *file)
>  		return -ENODEV;
>  	}
>  
> -	sem = &gs_open_close_sem[port_num];
> -	if (down_interruptible(sem)) {
> +	mtx = &gs_open_close_lock[port_num];
> +	if (mutex_lock_interruptible(mtx)) {
>  		printk(KERN_ERR
> -		"gs_open: (%d,%p,%p) interrupted waiting for semaphore\n",
> +		"gs_open: (%d,%p,%p) interrupted waiting for mutex\n",
>  			port_num, tty, file);
>  		return -ERESTARTSYS;
>  	}
> @@ -754,12 +755,12 @@ static int gs_open(struct tty_struct *tty, struct file *file)
>  
>  exit_unlock_port:
>  	spin_unlock_irqrestore(&port->port_lock, flags);
> -	up(sem);
> +	mutex_unlock(mtx);
>  	return ret;
>  
>  exit_unlock_dev:
>  	spin_unlock_irqrestore(&dev->dev_lock, flags);
> -	up(sem);
> +	mutex_unlock(mtx);
>  	return ret;
>  
>  }
> @@ -781,7 +782,7 @@ exit_unlock_dev:
>  static void gs_close(struct tty_struct *tty, struct file *file)
>  {
>  	struct gs_port *port = tty->driver_data;
> -	struct semaphore *sem;
> +	struct mutex *mtx;
>  
>  	if (port == NULL) {
>  		printk(KERN_ERR "gs_close: NULL port pointer\n");
> @@ -790,8 +791,8 @@ static void gs_close(struct tty_struct *tty, struct file *file)
>  
>  	gs_debug("gs_close: (%d,%p,%p)\n", port->port_num, tty, file);
>  
> -	sem = &gs_open_close_sem[port->port_num];
> -	down(sem);
> +	mtx = &gs_open_close_lock[port->port_num];
> +	mutex_lock(mtx);
>  
>  	spin_lock_irq(&port->port_lock);
>  
> @@ -846,7 +847,7 @@ static void gs_close(struct tty_struct *tty, struct file *file)
>  
>  exit:
>  	spin_unlock_irq(&port->port_lock);
> -	up(sem);
> +	mutex_unlock(mtx);
>  }
>  
>  /*
> 
> -- 
> Matthias Kaehlcke
> Linux Application Developer
> Barcelona
> 
>              If liberty means anything at all, it means the
>            right to tell people what they do not want to hear
>                             (George Orwell)
>                                                                  .''`.
>     using free software / Debian GNU/Linux | http://debian.org  : :'  :
>                                                                 `. `'`
> gpg --keyserver pgp.mit.edu --recv-keys 47D8E5D4                  `-
> 


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