tty: Remove unnecessary re-test of ldisc ref count
Since the tty->ldisc is prevented from being changed by tty_set_ldisc() when a tty is being hung up, re-testing the ldisc user count is unnecessary -- ie, it cannot be a different ldisc and the user count cannot have increased (assuming the caller meets the precondition that TTY_LDISC flag is cleared) Removal of the 'early-out' locking optimization is necessary for the subsequent patch 'tty: Fix ldisc halt sequence on hangup'. Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -558,29 +558,29 @@ static int tty_ldisc_wait_idle(struct tty_struct *tty, long timeout)
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* have been halted for this to guarantee it remains idle.
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*
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* Caller must hold legacy and ->ldisc_mutex.
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*
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* NB: tty_set_ldisc() is prevented from changing the ldisc concurrently
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* with this function by checking the TTY_HUPPING flag.
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*/
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static bool tty_ldisc_hangup_wait_idle(struct tty_struct *tty)
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{
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while (tty->ldisc) { /* Not yet closed */
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if (atomic_read(&tty->ldisc->users) != 1) {
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char cur_n[TASK_COMM_LEN], tty_n[64];
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long timeout = 3 * HZ;
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tty_unlock(tty);
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char cur_n[TASK_COMM_LEN], tty_n[64];
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long timeout = 3 * HZ;
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while (tty_ldisc_wait_idle(tty, timeout) == -EBUSY) {
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timeout = MAX_SCHEDULE_TIMEOUT;
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printk_ratelimited(KERN_WARNING
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"%s: waiting (%s) for %s took too long, but we keep waiting...\n",
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__func__, get_task_comm(cur_n, current),
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tty_name(tty, tty_n));
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}
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/* must reacquire both locks and preserve lock order */
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mutex_unlock(&tty->ldisc_mutex);
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tty_lock(tty);
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mutex_lock(&tty->ldisc_mutex);
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continue;
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if (tty->ldisc) { /* Not yet closed */
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tty_unlock(tty);
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while (tty_ldisc_wait_idle(tty, timeout) == -EBUSY) {
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timeout = MAX_SCHEDULE_TIMEOUT;
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printk_ratelimited(KERN_WARNING
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"%s: waiting (%s) for %s took too long, but we keep waiting...\n",
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__func__, get_task_comm(cur_n, current),
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tty_name(tty, tty_n));
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}
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break;
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/* must reacquire both locks and preserve lock order */
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mutex_unlock(&tty->ldisc_mutex);
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tty_lock(tty);
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mutex_lock(&tty->ldisc_mutex);
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}
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return !!tty->ldisc;
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}
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