Re: 2.6.16.18 kernel freezes while pppd is exiting

[Paul Fulghum <paulkf@microgate.com>]

Alan Cox wrote:
>> 	spin_unlock_irqrestore(&tty->buf.lock, flags);
>>+	clear_bit(TTY_FLUSHING, &tty->flags);
> 
> 
> Shouldn't those two be reversed if you want to go with this path.

I don't see that is necessary.

 > How is this occuring anyway the flush_to_ldisc path should never re-enter.

If a driver has low_latency set, flush_to_ldisc
can be called from both scheduled work (due to
hitting TTY_DONT_FLIP) and directly from an ISR.
On an SMP system, they can run in parallel.

I don't know for sure that is the path being hit,
it could be some other odd combination.
But there is no inherent serialization
of flush_to_ldisc.

-- 
Paul Fulghum
Microgate Systems, Ltd.