Re: Serial driver hangs

["Roland Caßebohm" <roland.cassebohm@VisionSystems.de>]

Am Mittwoch, 29. September 2004 15:17 schrieb Paul Fulghum:
> Roland Caßebohm wrote:
> > I have made a little test, at which the receive interrupt
> > is disabled in that state. It seems to be no improvement
> > to the solution of just trow away the bytes of the FIFO.
> > In both cases characters got lost.
>
> How did you reenable the receive interrupt in your test?

I have added a routine to "struct tty_driver" for restarting 
the RX interrupt after TTY_DONT_FLIP bit is cleared in 
read_chan().

>>>>>>>>>>>>
        clear_bit(TTY_DONT_FLIP, &tty->flags);
       	if (tty->driver.restart_rx)
               tty->driver.restart_rx(tty);
>>>>>>>>>>>>

and in the interrupt routine I have disabled the RX interrupt, 
if TTY_DONT_FLIP is set.

>>>>>>>>>>>>
            if (tty->flip.count >= TTY_FLIPBUF_SIZE)
            {
                info->IER &= ~UART_IER_RDI;
                serial_outp(info, UART_IER, info->IER);
                return;     // if TTY_DONT_FLIP is set
            }
>>>>>>>>>>>>

and tty->driver.restart_rx() is:

>>>>>>>>>>>>
static void rs_restart_rx(struct tty_struct *tty)
{
    struct async_struct *info = (struct async_struct 
*)tty->driver_data;
    unsigned long flags;

    if (serial_paranoia_check(info, tty->device, 
"rs_restart_rx"))
        return;

    save_flags(flags); cli();
    if (!(info->IER & UART_IER_RDI)) {
        info->IER |= UART_IER_RDI;
        serial_out(info, UART_IER, info->IER);
    }
    restore_flags(flags);
}
>>>>>>>>>>>>

It seems to take to long time in read_chan(). Do you now what 
is the exact reason of locking the filp buffer with the 
TTY_DONT_FLIP flag? For a short look I would say the buffers 
are safe locked by the spinlock tty->read_lock.

Roland
-- 
___________________________________________________

VS Vision Systems GmbH, Industrial Image Processing
Dipl.-Ing. Roland Caßebohm
Aspelohe 27A, D-22848 Norderstedt, Germany
Mail: roland.cassebohm@visionsystems.de
http://www.visionsystems.de
___________________________________________________