1. 04 Oct, 2009 1 commit
    • Linus Torvalds's avatar
      tty: Avoid dropping ldisc_mutex over hangup tty re-initialization · 0b5759c6
      Linus Torvalds authored
      A couple of people have hit the WARN_ON() in drivers/char/tty_io.c,
      tty_open() that is unhappy about seeing the tty line discipline go away
      during the tty hangup. See for example
      
      	http://bugzilla.kernel.org/show_bug.cgi?id=14255
      
      and the reason is that we do the tty_ldisc_halt() outside the
      ldisc_mutex in order to be able to flush the scheduled work without a
      deadlock with vhangup_work.
      
      However, it turns out that we can solve this particular case by
      
       - using "cancel_delayed_work_sync()" in tty_ldisc_halt(), which waits
         for just the particular work, rather than synchronizing with any
         random outstanding pending work.
      
         This won't deadlock, since the buf.work we synchronize with doesn't
         care about the ldisc_mutex, it just flushes the tty ldisc buffers.
      
       - realize that for this particular case, we don't need to wait for any
         hangup work, because we are inside the hangup codepaths ourselves.
      
      so as a result we can just drop the flush_scheduled_work() entirely, and
      then move the tty_ldisc_halt() call to inside the mutex.  That way we
      never expose the partially torn down ldisc state to tty_open(), and hold
      the ldisc_mutex over the whole sequence.
      Reported-by: default avatarIngo Molnar <mingo@elte.hu>
      Reported-by: default avatarHeinz Diehl <htd@fancy-poultry.org>
      Cc: stable@kernel.org
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      0b5759c6
  2. 03 Oct, 2009 6 commits
  3. 02 Oct, 2009 27 commits
  4. 01 Oct, 2009 6 commits