Re: [BUG][2.6.8.1] serial driver hangs SMP kernel, but not the UPkernel

[Paul Fulghum]

Alan Cox wrote:
> On Gwe, 2005-01-07 at 00:43, Paul Fulghum wrote:
>
> > IIRC that guarantees a deadlock on SMP due to the
> > generic serial layer trying to grab a spinlock
> > that is already held. (Which prompted the original
> > bug report by Tim several months ago)
>
>
> I fixed the tty locking issues with that. If there are any left they
> should be solely in the serial generic code and I've no idea there

Yes, that is where the locking problems were.
When I last looked at it the problem call path was:

serial8250_interrupt();
   spin_lock(port->lock);
   serial8250_handle_port();
      receive_chars();
         flip.work.func(); /* if FLIP buffer full or low_latency set */
             ldisc->receive_buf(); /* N_TTY */
                 tty->driver->flush_chars();
                    uart_start();
                       spin_lock(port->lock); *BANG*

--
Paul Fulghum
Microgate Systems, Ltd

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