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SubjectRe: USB: serial: kfifo_len locking
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Am Dienstag, den 05.01.2010, 12:04 +0100 schrieb Johan Hovold:
> > This actually was a side effect of the "byte lost on close" patch
> > that I submitted, it should be in Greg's tree. The relevant part goes
> > like this:
> > diff --git a/drivers/usb/serial/generic.c b/drivers/usb/serial/generic.c
> > index f1ea3a3..3372faa 100644
> > --- a/drivers/usb/serial/generic.c
> > +++ b/drivers/usb/serial/generic.c
> > @@ -386,12 +386,15 @@ int usb_serial_generic_chars_in_buffer(struct tty_struct *tty)
> >
> > dbg("%s - port %d", __func__, port->number);
> >
> > + spin_lock_irqsave(&port->lock, flags);
> > if (serial->type->max_in_flight_urbs) {
> > - spin_lock_irqsave(&port->lock, flags);
> > chars = port->tx_bytes_flight;
> > - spin_unlock_irqrestore(&port->lock, flags);
> > - } else if (serial->num_bulk_out)
> > - chars = kfifo_len(&port->write_fifo);
> > + } else if (serial->num_bulk_out) {
> > + /* This overcounts badly, but is good enough for drain wait. */
> > + chars = __kfifo_len(port->write_fifo);
> > + chars += port->write_urb_busy * port->bulk_out_size;
> > + }
> > + spin_unlock_irqrestore(&port->lock, flags);
> >
> > dbg("%s - returns %d", __func__, chars);
> > return chars;
>
> That is indeed what you submitted on Dec 7, but this is what is in
> Greg's tree:
>
> 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()

Stefani




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