On 07/10/2012 06:54 AM, Shachar Shemesh wrote: > From: Shachar Shemesh > > Commit acfa747b introduced the TTY_HUPPING flag to distinguish > closed TTY from currently closing ones. The test in tty_set_ldisc > still remained pointing at the old flag. This causes pppd to > sometimes lapse into uninterruptible sleep when killed and > restarted. > > Signed-off-by: Shachar Shemesh > --- > Tested with 3.2.20 kernel. > > diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c > index 24b95db..a662a24 100644 > --- a/drivers/tty/tty_ldisc.c > +++ b/drivers/tty/tty_ldisc.c > @@ -658,7 +658,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc) > goto enable; > } > > - if (test_bit(TTY_HUPPED, &tty->flags)) { > + if (test_bit(TTY_HUPPING, &tty->flags)) { > /* We were raced by the hangup method. It will have stomped > the ldisc data and closed the ldisc down */ > clear_bit(TTY_LDISC_CHANGING, &tty->flags); Yes, that makes the issue go away, but does not seem to be right too. There are two issues I see: * TTY_HUPPED has no use now. That is incorrect. Here should be a test for both flags, I think. * The change forces the set_ldisc path to always re-open the ldisc even if it the terminal is HUPPED. The bug is not in the kernel. It was in login(1) (util-linux). And it should be fixed by now. See: http://git.kernel.org/?p=utils/util-linux/util-linux.git;a=commitdiff;h=2e7035646eb85851171cc2e989bfa858a4f00cd4 I'm for an in-fact revert of the patch. But temporarily I would still return EIO. However let's do it even after the reopen is done, so that we get rid of the user-visible regression. Like in the attached patch. The regression was introduced by commit c65c9bc3e (tty: rewrite the ldisc locking). That is !three! years ago. And that is suspicious in itself. BTW Why pppd thinks it is a good idea to ignore EIO from TIOCSETD ioctl? regards, -- js suse labs