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Date: Tue, 5 Jan 2010 12:35:25 +0100
From: Johan Hovold <jhovold@...il.com>
To: Stefani Seibold <stefani@...bold.net>
Cc: Johan Hovold <jhovold@...il.com>,
Pete Zaitcev <zaitcev@...hat.com>, Greg KH <greg@...ah.com>,
Andrew Morton <akpm@...ux-foundation.org>,
linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: USB: serial: kfifo_len locking
> > > > 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:
The drain patch merge was a side-track and you were CC:d as you
were part of the original thread.
You did however remove the locking on kfifo_len that the original author
had put there with the exact patch you're quoting:
> 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);
Here's the change. The fifo used to be protected by a lock, but is no
longer.
>
> 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.
Never say you did.
/Johan
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