Re: USB: serial: kfifo_len locking

[Stefani Seibold <stefani@seibold.net>]

Am Dienstag, den 05.01.2010, 12:14 +0100 schrieb Johan Hovold:

> > > 
> > > http://git.kernel.org/?p=linux/kernel/git/gregkh/patches.git;a=blob;f=usb/usb-serial-mct_usb232-add-drain-on-close.patch;h=c464f1a82e93df0dd41762a8cb33b0b22e90cdd7;hb=1ea72e7c40b239c6b6f88a4993196be66fc3d892
> > > 
> > > 38 --- a/drivers/usb/serial/generic.c
> > > 39 +++ b/drivers/usb/serial/generic.c
> > > 40 @@ -369,8 +369,11 @@ int usb_serial_generic_write_room(struct
> > > 41                         room = port->bulk_out_size *
> > > 42                                 (serial->type->max_in_flight_urbs -
> > > 43                                  port->urbs_in_flight);
> > > 44 -       } else if (serial->num_bulk_out)
> > > 45 +       } else if (serial->num_bulk_out) {
> > > 46 +               /* This overcounts badly, but is good enough for drain wait. */
> > > 47                 room = kfifo_avail(&port->write_fifo);
> > > 48 +               room += port->write_urb_busy * port->bulk_out_size;
> > > 49 +       }
> > > 50         spin_unlock_irqrestore(&port->lock, flags);
> > > 51  
> > > 52         dbg("%s - returns %d", __func__, room);
> > > 
> > > 
> > > Which does not make any sense at all. Bad merge? What do you say Greg?
> > > 
> > 
> > I don't know where is your problem? This are two different functions
> > usb_serial_generic_write_room() and usb_serial_generic_chars_in_buffer()
> 
> Exactly my point. 
> 
> The drain patch needed to modify chars_in_buffer, but the patch in Greg's
> tree modifies write_room instead (which does not make sense and was
> neither part of the submitted patch).
> 

Sorry, but i am not sure if i the right address about your complains.
The only thing i have done in the usb serial driver is the port to the
new kfifo API. This is the original patch i had posted:

diff -u -N -r -p old/drivers/usb/serial/generic.c new/drivers/usb/serial/generic.c
--- old/drivers/usb/serial/generic.c	2009-12-23 08:54:06.966476248 +0100
+++ new/drivers/usb/serial/generic.c	2009-12-23 09:06:25.778474708 +0100
@@ -276,7 +276,7 @@ static int usb_serial_generic_write_star
 	if (port->write_urb_busy)
 		start_io = false;
 	else {
-		start_io = (kfifo_len(port->write_fifo) != 0);
+		start_io = (kfifo_len(&port->write_fifo) != 0);
 		port->write_urb_busy = start_io;
 	}
 	spin_unlock_irqrestore(&port->lock, flags);
@@ -285,7 +285,7 @@ static int usb_serial_generic_write_star
 		return 0;
 
 	data = port->write_urb->transfer_buffer;
-	count = kfifo_out_locked(port->write_fifo, data, port->bulk_out_size, &port->lock);
+	count = kfifo_out_locked(&port->write_fifo, data, port->bulk_out_size, &port->lock);
 	usb_serial_debug_data(debug, &port->dev, __func__, count, data);
 
 	/* set up our urb */
@@ -345,7 +345,7 @@ int usb_serial_generic_write(struct tty_
 		return usb_serial_multi_urb_write(tty, port,
 						  buf, count);
 
-	count = kfifo_in_locked(port->write_fifo, buf, count, &port->lock);
+	count = kfifo_in_locked(&port->write_fifo, buf, count, &port->lock);
 	result = usb_serial_generic_write_start(port);
 
 	if (result >= 0)
@@ -370,7 +370,7 @@ int usb_serial_generic_write_room(struct
 				(serial->type->max_in_flight_urbs -
 				 port->urbs_in_flight);
 	} else if (serial->num_bulk_out)
-		room = port->write_fifo->size - kfifo_len(port->write_fifo);
+		room = kfifo_avail(&port->write_fifo);
 	spin_unlock_irqrestore(&port->lock, flags);
 
 	dbg("%s - returns %d", __func__, room);
@@ -391,7 +391,7 @@ int usb_serial_generic_chars_in_buffer(s
 		chars = port->tx_bytes_flight;
 		spin_unlock_irqrestore(&port->lock, flags);
 	} else if (serial->num_bulk_out)
-		chars = kfifo_len(port->write_fifo);
+		chars = kfifo_len(&port->write_fifo);
 
 	dbg("%s - returns %d", __func__, chars);
 	return chars;
@@ -507,7 +507,7 @@ void usb_serial_generic_write_bulk_callb
 		if (status) {
 			dbg("%s - nonzero multi-urb write bulk status "
 				"received: %d", __func__, status);
-			kfifo_reset(port->write_fifo);
+			kfifo_reset_out(&port->write_fifo);
 		} else
 			usb_serial_generic_write_start(port);
 	}
diff -u -N -r -p old/drivers/usb/serial/usb-serial.c new/drivers/usb/serial/usb-serial.c
--- old/drivers/usb/serial/usb-serial.c	2009-12-23 08:54:23.204476351 +0100
+++ new/drivers/usb/serial/usb-serial.c	2009-12-23 09:06:39.664475312 +0100
@@ -595,8 +595,7 @@ static void port_release(struct device *
 	usb_free_urb(port->write_urb);
 	usb_free_urb(port->interrupt_in_urb);
 	usb_free_urb(port->interrupt_out_urb);
-	if (!IS_ERR(port->write_fifo) && port->write_fifo)
-		kfifo_free(port->write_fifo);
+	kfifo_free(&port->write_fifo);
 	kfree(port->bulk_in_buffer);
 	kfree(port->bulk_out_buffer);
 	kfree(port->interrupt_in_buffer);
@@ -939,7 +938,7 @@ int usb_serial_probe(struct usb_interfac
 			dev_err(&interface->dev, "No free urbs available\n");
 			goto probe_error;
 		}
-		if (kfifo_alloc(port->write_fifo, PAGE_SIZE, GFP_KERNEL))
+		if (kfifo_alloc(&port->write_fifo, PAGE_SIZE, GFP_KERNEL))
 			goto probe_error;
 		buffer_size = le16_to_cpu(endpoint->wMaxPacketSize);
 		port->bulk_out_size = buffer_size;
diff -u -N -r -p old/include/linux/usb/serial.h new/include/linux/usb/serial.h
--- old/include/linux/usb/serial.h	2009-12-23 08:54:34.368476110 +0100
+++ new/include/linux/usb/serial.h	2009-12-23 09:06:32.870725683 +0100
@@ -16,6 +16,7 @@
 #include <linux/kref.h>
 #include <linux/mutex.h>
 #include <linux/sysrq.h>
+#include <linux/kfifo.h>
 
 #define SERIAL_TTY_MAJOR	188	/* Nice legal number now */
 #define SERIAL_TTY_MINORS	254	/* loads of devices :) */
@@ -94,7 +95,7 @@ struct usb_serial_port {
 	unsigned char		*bulk_out_buffer;
 	int			bulk_out_size;
 	struct urb		*write_urb;
-	struct kfifo		*write_fifo;
+	struct kfifo		write_fifo;
 	int			write_urb_busy;
 	__u8			bulk_out_endpointAddress;
 

As you can see i didn't changed noting about this drain thing.

Stefani