Commit a8d78d9f authored by Johan Hovold's avatar Johan Hovold
Browse files

USB: serial: clean up throttle handling 



Clean up the throttle implementation by dropping the redundant
throttle_req flag which was a remnant from back when there was only a
single read URB.

Also convert the throttled flag to an atomic bit flag.

Signed-off-by: default avatarJohan Hovold <johan@kernel.org>
parent 3f5edd58

drivers/usb/serial/generic.c

+8 −26
Original line number Diff line number Diff line
@@ -106,12 +106,8 @@ void usb_serial_generic_deregister(void) 
int usb_serial_generic_open(struct tty_struct *tty, struct usb_serial_port *port)

{

	int result = 0;

	unsigned long flags;



	spin_lock_irqsave(&port->lock, flags);

	port->throttled = 0;

	port->throttle_req = 0;

	spin_unlock_irqrestore(&port->lock, flags);

	clear_bit(USB_SERIAL_THROTTLED, &port->flags);



	if (port->bulk_in_size)

		result = usb_serial_generic_submit_read_urbs(port, GFP_KERNEL);
@@ -375,7 +371,6 @@ void usb_serial_generic_read_bulk_callback(struct urb *urb) 
{

	struct usb_serial_port *port = urb->context;

	unsigned char *data = urb->transfer_buffer;

	unsigned long flags;

	bool stopped = false;

	int status = urb->status;

	int i;
@@ -429,15 +424,10 @@ void usb_serial_generic_read_bulk_callback(struct urb *urb) 
	if (stopped)

		return;



	/* Throttle the device if requested by tty */

	spin_lock_irqsave(&port->lock, flags);

	port->throttled = port->throttle_req;

	if (!port->throttled) {

		spin_unlock_irqrestore(&port->lock, flags);

	if (test_bit(USB_SERIAL_THROTTLED, &port->flags))

		return;



	usb_serial_generic_submit_read_urb(port, i, GFP_ATOMIC);

	} else {

		spin_unlock_irqrestore(&port->lock, flags);

	}

}

EXPORT_SYMBOL_GPL(usb_serial_generic_read_bulk_callback);
@@ -485,23 +475,16 @@ EXPORT_SYMBOL_GPL(usb_serial_generic_write_bulk_callback); 
void usb_serial_generic_throttle(struct tty_struct *tty)

{

	struct usb_serial_port *port = tty->driver_data;

	unsigned long flags;



	spin_lock_irqsave(&port->lock, flags);

	port->throttle_req = 1;

	spin_unlock_irqrestore(&port->lock, flags);

	set_bit(USB_SERIAL_THROTTLED, &port->flags);

}

EXPORT_SYMBOL_GPL(usb_serial_generic_throttle);



void usb_serial_generic_unthrottle(struct tty_struct *tty)

{

	struct usb_serial_port *port = tty->driver_data;

	int was_throttled;



	spin_lock_irq(&port->lock);

	was_throttled = port->throttled;

	port->throttled = port->throttle_req = 0;

	spin_unlock_irq(&port->lock);

	clear_bit(USB_SERIAL_THROTTLED, &port->flags);



	/*

	 * Matches the smp_mb__after_atomic() in
@@ -509,7 +492,6 @@ void usb_serial_generic_unthrottle(struct tty_struct *tty) 
	 */

	smp_mb();



	if (was_throttled)

	usb_serial_generic_submit_read_urbs(port, GFP_KERNEL);

}

EXPORT_SYMBOL_GPL(usb_serial_generic_unthrottle);

include/linux/usb/serial.h

+1 −4
Original line number Diff line number Diff line
@@ -28,6 +28,7 @@ 


/* USB serial flags */

#define USB_SERIAL_WRITE_BUSY	0

#define USB_SERIAL_THROTTLED	1



/**

 * usb_serial_port: structure for the specific ports of a device.
@@ -67,8 +68,6 @@ 
 * @flags: usb serial port flags

 * @write_wait: a wait_queue_head_t used by the port.

 * @work: work queue entry for the line discipline waking up.

 * @throttled: nonzero if the read urb is inactive to throttle the device

 * @throttle_req: nonzero if the tty wants to throttle us

 * @dev: pointer to the serial device

 *

 * This structure is used by the usb-serial core and drivers for the specific
@@ -115,8 +114,6 @@ struct usb_serial_port { 
	unsigned long		flags;

	wait_queue_head_t	write_wait;

	struct work_struct	work;

	char			throttled;

	char			throttle_req;

	unsigned long		sysrq; /* sysrq timeout */

	struct device		dev;

};

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