No tty driver modifies termios during throttle() or unthrottle(). Therefore, only read safety is required.
However, tty_throttle_safe and tty_unthrottle_safe must still be mutually exclusive; introduce throttle_mutex for that purpose. Signed-off-by: Peter Hurley <[email protected]> --- drivers/tty/n_tty.c | 4 ---- drivers/tty/tty_io.c | 1 + drivers/tty/tty_ioctl.c | 8 ++++---- include/linux/tty.h | 1 + 4 files changed, 6 insertions(+), 8 deletions(-) diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c index 3d334ef..dba7e99 100644 --- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -1519,9 +1519,7 @@ static void __receive_buf(struct tty_struct *tty, const unsigned char *cp, tty_set_flow_change(tty, TTY_THROTTLE_SAFE); if (receive_room(tty) >= TTY_THRESHOLD_THROTTLE) break; - up_read(&tty->termios_rwsem); throttled = tty_throttle_safe(tty); - down_read(&tty->termios_rwsem); if (!throttled) break; } @@ -2084,9 +2082,7 @@ do_it_again: if (!tty->count) break; n_tty_set_room(tty); - up_read(&tty->termios_rwsem); unthrottled = tty_unthrottle_safe(tty); - down_read(&tty->termios_rwsem); if (!unthrottled) break; } diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index 30201e6..55b8594 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -2951,6 +2951,7 @@ void initialize_tty_struct(struct tty_struct *tty, tty->session = NULL; tty->pgrp = NULL; mutex_init(&tty->legacy_mutex); + mutex_init(&tty->throttle_mutex); init_rwsem(&tty->termios_rwsem); init_ldsem(&tty->ldisc_sem); init_waitqueue_head(&tty->write_wait); diff --git a/drivers/tty/tty_ioctl.c b/drivers/tty/tty_ioctl.c index 490e499..5e55ca4 100644 --- a/drivers/tty/tty_ioctl.c +++ b/drivers/tty/tty_ioctl.c @@ -151,7 +151,7 @@ int tty_throttle_safe(struct tty_struct *tty) { int ret = 0; - down_write(&tty->termios_rwsem); + mutex_lock(&tty->throttle_mutex); if (!test_bit(TTY_THROTTLED, &tty->flags)) { if (tty->flow_change != TTY_THROTTLE_SAFE) ret = 1; @@ -161,7 +161,7 @@ int tty_throttle_safe(struct tty_struct *tty) tty->ops->throttle(tty); } } - up_write(&tty->termios_rwsem); + mutex_unlock(&tty->throttle_mutex); return ret; } @@ -182,7 +182,7 @@ int tty_unthrottle_safe(struct tty_struct *tty) { int ret = 0; - down_write(&tty->termios_rwsem); + mutex_lock(&tty->throttle_mutex); if (test_bit(TTY_THROTTLED, &tty->flags)) { if (tty->flow_change != TTY_UNTHROTTLE_SAFE) ret = 1; @@ -192,7 +192,7 @@ int tty_unthrottle_safe(struct tty_struct *tty) tty->ops->unthrottle(tty); } } - up_write(&tty->termios_rwsem); + mutex_unlock(&tty->throttle_mutex); return ret; } diff --git a/include/linux/tty.h b/include/linux/tty.h index 1d1c7c6a..e56ab4c 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -244,6 +244,7 @@ struct tty_struct { struct mutex atomic_write_lock; struct mutex legacy_mutex; + struct mutex throttle_mutex; struct rw_semaphore termios_rwsem; spinlock_t ctrl_lock; /* Termios values are protected by the termios rwsem */ -- 1.8.1.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
