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    SubjectRe: [Patch] 2.4.28-pre3 tty/ldisc fixes
    On Tue, Nov 02, 2004 at 10:02:44AM -0500, Jason Baron wrote:
    >
    > On Sun, 31 Oct 2004, Krzysztof Taraszka wrote:
    >
    > > Dnia sobota, 30 pa?dziernika 2004 21:19, napisa?e?:
    > > > On Fri, Oct 29, 2004 at 02:29:43PM -0400, Jason Baron wrote:
    > >
    > > > > Here's an updated 2.4 tty patch. I'm not sure if the updated patch would
    > > > > fix the above issue, but it has a lot of changes so it might be worth a
    > > > > try.
    > > >
    > > > This looks better - at least the system boots without hang or oops ;)
    > >
    > > where is an updated 2.4 tty patch ?
    >
    > hmmm...seems like my e-mails keeping getting dropped, perhaps the patch is
    > too large? Here is a link to the patch:
    >
    > http://people.redhat.com/~jbaron/tty/2.4-tty-V5.patch

    Finally I have found the bug which prevented SieFS (slink) from
    working. The bug was in drivers/char/tty_ioctl.c:

    @@ -131,16 +141,20 @@ static void change_termios(struct tty_st
    }
    }

    - if (tty->driver.set_termios)
    - (*tty->driver.set_termios)(tty, &old_termios);
    + ld = tty_ldisc_ref(tty);
    + if (ld != NULL) {
    + if (ld->set_termios)
    + (ld->set_termios)(tty, &old_termios);
    + tty_ldisc_deref(ld);
    + }
    + spin_unlock_irqrestore(&tty_termios_lock, flags);

    - if (tty->ldisc.set_termios)
    - (*tty->ldisc.set_termios)(tty, &old_termios);
    }

    The call to tty->driver.set_termios was lost, therefore the serial
    port speed was not set properly.

    Simply adding this call back does not work, because set_termios
    handlers in usbserial use semaphores for locking, and therefore cannot
    be called while holding the tty_termios_lock spinlock. Because of
    this, some more backporting from 2.6.x is needed - Alan Cox has
    already changed tty_termios_lock to a per-tty semaphore in 2.6.x, this
    change is needed for 2.4.x too.

    The patches are in separate emails: first is the backport of the
    termios locking changes, second patch adds back lost call to
    tty->driver.set_termios (which is safe after first patch).
    [unhandled content-type:application/pgp-signature]
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