On Thu, 16 Oct 2014 16:24:58 -0400 Peter Hurley <peter@xxxxxxxxxxxxxxxxxx> wrote: > Hi Greg, > > This patch series has 3 major changes to how tty locking behaves: > 1. the lock order of tty_lock() and tty->ldisc_sem is reversed; > this eliminates a bunch of lock drop/reacquire which, in turn, > eliminates tty state tracking that can no longer be observed. > This also allows the pty driver to wait for input processing to > complete while closing before setting TTY_OTHER_CLOSED (which > eliminates the ugliness of checking input twice in n_tty_read() and > n_tty_poll()). > 2. the footprint of tty_mutex is reduced to only adding and removing > ttys and is no longer held to acquire the tty_lock() in tty_open(); > this allows for multiple ttys to be opened concurrently, even if > one open stalls waiting for its tty_lock(). > 3. pty pair locking is reordered to master first, then slave, rather > than by address. This works because, while releasing the master pty, > the slave tty count needs to be changed, whereas, when releasing the > slave, the master pty does not need to be accessed. > This furthur eliminates more lock drop/reacquire. > > The longer-term goals, which this series builds towards, is: > 1. simplifying the tty open/close behavior > 2. eliminating the ASYNC_CLOSING code without breaking existing userspace > 3. eliminating returning -EIO from tty_open(). Not sure if this is possible yet. Reviewed-by: Alan Cox <alan@xxxxxxxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
