Messages in this thread | ![/](/images/icornerl.gif) | | Date | Thu, 25 Nov 2010 14:03:54 +0000 | From | Alan Cox <> | Subject | Re: [PATCHv5 05/17] tty: don't allow ldisc dcd_change() after ldisc halt |
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> Didn't know that current design is crap. :)
It's based on the old big kernel lock and it has lots of horrors when used from interrupt paths as a result. A big chunk of it can in time I think move to just having a per tty ldisc lock that covers all changes etc, but we aren't there yet.
> Ok, I think I'll add a new waitqueue and a new bit (TTY_LDISC_NOREF)
We've got the wait queue already
My first guess would be something like
static struct tty_ldisc *tty_ldisc_irqget(struct tty_struct *tty) { unsigned long flags; struct tty_ldisc *ld; spin_lock_irqsave(&tty_ldisc_lock, flags); ld = NULL; if (test_bit(TTY_LDISC, &tty->flags)) { ld = get_ldisc(tty->ldisc); WARN_ON(test_and_set_bit(TTY_LDISC_IRQ, &tty->flags)); } spin_unlock_irqrestore(&tty_ldisc_lock, flags); return ld; }
static struct tty_ldisc *tty_ldisc_irqput(struct tty_ldisc *ld) { clear_bit(TTY_LDISC_IRQ, &tty->flags); tty_ldisc_put(ld); }
(and I think you can then wait on tty_ldisc_idle for the flag to go clear after clearing TTY_LDISC)
It might be better to make it a count of course in case there are later multiple users of this ?
Alan
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