diff options
Diffstat (limited to 'drivers/tty/tty_ioctl.c')
| -rw-r--r-- | drivers/tty/tty_ioctl.c | 64 |
1 files changed, 64 insertions, 0 deletions
diff --git a/drivers/tty/tty_ioctl.c b/drivers/tty/tty_ioctl.c index d58b92cc187..132d452578b 100644 --- a/drivers/tty/tty_ioctl.c +++ b/drivers/tty/tty_ioctl.c @@ -106,6 +106,7 @@ void tty_throttle(struct tty_struct *tty) if (!test_and_set_bit(TTY_THROTTLED, &tty->flags) && tty->ops->throttle) tty->ops->throttle(tty); + tty->flow_change = 0; mutex_unlock(&tty->termios_mutex); } EXPORT_SYMBOL(tty_throttle); @@ -129,11 +130,74 @@ void tty_unthrottle(struct tty_struct *tty) if (test_and_clear_bit(TTY_THROTTLED, &tty->flags) && tty->ops->unthrottle) tty->ops->unthrottle(tty); + tty->flow_change = 0; mutex_unlock(&tty->termios_mutex); } EXPORT_SYMBOL(tty_unthrottle); /** + * tty_throttle_safe - flow control + * @tty: terminal + * + * Similar to tty_throttle() but will only attempt throttle + * if tty->flow_change is TTY_THROTTLE_SAFE. Prevents an accidental + * throttle due to race conditions when throttling is conditional + * on factors evaluated prior to throttling. + * + * Returns 0 if tty is throttled (or was already throttled) + */ + +int tty_throttle_safe(struct tty_struct *tty) +{ + int ret = 0; + + mutex_lock(&tty->termios_mutex); + if (!test_bit(TTY_THROTTLED, &tty->flags)) { + if (tty->flow_change != TTY_THROTTLE_SAFE) + ret = 1; + else { + __set_bit(TTY_THROTTLED, &tty->flags); + if (tty->ops->throttle) + tty->ops->throttle(tty); + } + } + mutex_unlock(&tty->termios_mutex); + + return ret; +} + +/** + * tty_unthrottle_safe - flow control + * @tty: terminal + * + * Similar to tty_unthrottle() but will only attempt unthrottle + * if tty->flow_change is TTY_UNTHROTTLE_SAFE. Prevents an accidental + * unthrottle due to race conditions when unthrottling is conditional + * on factors evaluated prior to unthrottling. + * + * Returns 0 if tty is unthrottled (or was already unthrottled) + */ + +int tty_unthrottle_safe(struct tty_struct *tty) +{ + int ret = 0; + + mutex_lock(&tty->termios_mutex); + if (test_bit(TTY_THROTTLED, &tty->flags)) { + if (tty->flow_change != TTY_UNTHROTTLE_SAFE) + ret = 1; + else { + __clear_bit(TTY_THROTTLED, &tty->flags); + if (tty->ops->unthrottle) + tty->ops->unthrottle(tty); + } + } + mutex_unlock(&tty->termios_mutex); + + return ret; +} + +/** * tty_wait_until_sent - wait for I/O to finish * @tty: tty we are waiting for * @timeout: how long we will wait |