Re: 'scheduling while atomic' during ppp connection on 2.6.37.1 and2.6.38

[Jiri Slaby]

On 03/20/2011 10:58 PM, Alan Cox wrote:
>> +        spin_lock_irqsave(&dc->spin_mutex, flags);
>>           if (port->port.count)
>>               room = kfifo_avail(&port->fifo_ul);
>> -        mutex_unlock(&port->tty_sem);
>> +        spin_unlock_irqrestore(&dc->spin_mutex, flags);
> 
> dc->spin_mutex does not protect port->port.count.

Neither port->tty_sem did.

Anyway is the test needed at all? I.e. could
tty->ops->write/chars_in_buffer/ntty_write_room be called with
port->port.count == 0 at all?

And the lock should not as well be needed. Kfifo assures atomicity where
there is only one reader and one writer which should be the case here.
Unless tty->ops->write can be called in parallel. And it should not,
that's what's tty->atomic_write_lock for.

thanks,
-- 
js
suse labs
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/