Hi,

2012/9/20 Alan Cox [off-list ref]:

So now when the user sets tty->low_latency on these devices the machine
crashes ?

This is the wrong direction - in fact we have a pile we need to move
the other way !

If they resolve to the same thing in hard RT patches fine, that's a
different question.

Sorry, Allan you are probably right, but I don't get it...

I agree that when the tty->low_latency flag is set on these machines,
the drivers that were modified by my patch will behave differently:
they will call the flush_to_ldisc() function directly instead of using
the work queue. So that indeed introduces different functionality.

But what I don't understand is how this would cause the machine to
crash? Even when the flush_to_ldisc() function is called from hard IRQ
context this would cause no problems: the flush_to_ldisc() function
uses IRQ save spin locks instead of mutexes to protect it's critical
section. Right?

Furthermore the majority of TTY drivers currently already use the
tty_flip_buffer_push() function.

Regards,
Ivo Sieben