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Commit 2276ad97 authored by Peter Hurley's avatar Peter Hurley Committed by Greg Kroah-Hartman
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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: default avatarPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 168942c9

drivers/tty/tty_ldisc.c

+19 −19
Original line number Diff line number Diff line
@@ -558,13 +558,16 @@ static int tty_ldisc_wait_idle(struct tty_struct *tty, long timeout) 
 *	have been halted for this to guarantee it remains idle.

 *

 *	Caller must hold legacy and ->ldisc_mutex.

 *

 *	NB: tty_set_ldisc() is prevented from changing the ldisc concurrently

 *	with this function by checking the TTY_HUPPING flag.

 */

static bool tty_ldisc_hangup_wait_idle(struct tty_struct *tty)

{

	while (tty->ldisc) {	/* Not yet closed */

		if (atomic_read(&tty->ldisc->users) != 1) {

	char cur_n[TASK_COMM_LEN], tty_n[64];

	long timeout = 3 * HZ;



	if (tty->ldisc) {	/* Not yet closed */

		tty_unlock(tty);



		while (tty_ldisc_wait_idle(tty, timeout) == -EBUSY) {
@@ -578,9 +581,6 @@ static bool tty_ldisc_hangup_wait_idle(struct tty_struct *tty) 
		mutex_unlock(&tty->ldisc_mutex);

		tty_lock(tty);

		mutex_lock(&tty->ldisc_mutex);

			continue;

		}

		break;

	}

	return !!tty->ldisc;

}