> > I can't help feeling a mutex might be simpler. It would also then fix > > tiocsti() which is most definitely broken right now and documented as > > racing. > > Hmm. Those tty's have too many different locks already. > > But maybe we could just have one generic mutex, and use it for termios and > IO locking. It makes perfect sense to serialize the ->receive_buf() code > with any termios changes, since termios is what affects _how_ that > ->receive_buf() function works. You cannot trivially just take the same lock for receive_buf and termios locking at the moment. The reason is that receive_buf can cause the tty to throttle which causes us to call the throttle methods which take the lock. tty_throttle() and tty_unthrottle() can be called from both receive_buf and non receive_buf paths so you can't just remove it. The better existing lock is probably tty->ldisc_mutex which we take when doing ldisc changes (which are an even more dramatic change during receive_buf). We don't do ldisc changes from the receive_buf path and it opens a path for further simplification of the ldisc logic if we can get to the point where the ldisc doesn't get called randomly from the tty layer when changing. > I do wonder why tiocsti() doesn't just use the tty buffering layer, > though? Maybe that harks back to the whole "pty's did things differently" > thing? Why does it go directly to ->receive_buf() in the first place? Historical question - I don't know - and at the time I commented it there was no quick fix and bigger problems to sort first Alan -- To unsubscribe from this list: send the line "unsubscribe kernel-testers" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
