tty: Refactor session leader SIGHUP from __tty_hangup()

Reduce complexity of __tty_hangup(); separate SIGHUP signalling
into tty_signal_session_leader().
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Acked-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/tty_io.c

@@ -532,6 +532,51 @@ void tty_wakeup(struct tty_struct *tty)
 
 EXPORT_SYMBOL_GPL(tty_wakeup);
 
+/**
+ *	tty_signal_session_leader	- sends SIGHUP to session leader
+ *
+ *	Send SIGHUP and SIGCONT to the session leader and its
+ *	process group.
+ *
+ *	Returns the number of processes in the session with this tty
+ *	as their controlling terminal. This value is used to drop
+ *	tty references for those processes.
+ */
+static int tty_signal_session_leader(struct tty_struct *tty)
+{
+	struct task_struct *p;
+	unsigned long flags;
+	int refs = 0;
+
+	read_lock(&tasklist_lock);
+	if (tty->session) {
+		do_each_pid_task(tty->session, PIDTYPE_SID, p) {
+			spin_lock_irq(&p->sighand->siglock);
+			if (p->signal->tty == tty) {
+				p->signal->tty = NULL;
+				/* We defer the dereferences outside fo
+				   the tasklist lock */
+				refs++;
+			}
+			if (!p->signal->leader) {
+				spin_unlock_irq(&p->sighand->siglock);
+				continue;
+			}
+			__group_send_sig_info(SIGHUP, SEND_SIG_PRIV, p);
+			__group_send_sig_info(SIGCONT, SEND_SIG_PRIV, p);
+			put_pid(p->signal->tty_old_pgrp);  /* A noop */
+			spin_lock_irqsave(&tty->ctrl_lock, flags);
+			if (tty->pgrp)
+				p->signal->tty_old_pgrp = get_pid(tty->pgrp);
+			spin_unlock_irqrestore(&tty->ctrl_lock, flags);
+			spin_unlock_irq(&p->sighand->siglock);
+		} while_each_pid_task(tty->session, PIDTYPE_SID, p);
+	}
+	read_unlock(&tasklist_lock);
+
+	return refs;
+}
+
 /**
  *	__tty_hangup		-	actual handler for hangup events
  *	@work: tty device
@@ -558,11 +603,10 @@ static void __tty_hangup(struct tty_struct *tty)
 {
 	struct file *cons_filp = NULL;
 	struct file *filp, *f = NULL;
-	struct task_struct *p;
 	struct tty_file_private *priv;
 	int    closecount = 0, n;
 	unsigned long flags;
-	int refs = 0;
+	int refs;
 
 	if (!tty)
 		return;
@@ -605,31 +649,10 @@ static void __tty_hangup(struct tty_struct *tty)
 	 */
 	tty_ldisc_hangup(tty);
 
-	read_lock(&tasklist_lock);
-	if (tty->session) {
-		do_each_pid_task(tty->session, PIDTYPE_SID, p) {
-			spin_lock_irq(&p->sighand->siglock);
-			if (p->signal->tty == tty) {
-				p->signal->tty = NULL;
-				/* We defer the dereferences outside fo
-				   the tasklist lock */
-				refs++;
-			}
-			if (!p->signal->leader) {
-				spin_unlock_irq(&p->sighand->siglock);
-				continue;
-			}
-			__group_send_sig_info(SIGHUP, SEND_SIG_PRIV, p);
-			__group_send_sig_info(SIGCONT, SEND_SIG_PRIV, p);
-			put_pid(p->signal->tty_old_pgrp);  /* A noop */
-			spin_lock_irqsave(&tty->ctrl_lock, flags);
-			if (tty->pgrp)
-				p->signal->tty_old_pgrp = get_pid(tty->pgrp);
-			spin_unlock_irqrestore(&tty->ctrl_lock, flags);
-			spin_unlock_irq(&p->sighand->siglock);
-		} while_each_pid_task(tty->session, PIDTYPE_SID, p);
-	}
-	read_unlock(&tasklist_lock);
+	refs = tty_signal_session_leader(tty);
+	/* Account for the p->signal references we killed */
+	while (refs--)
+		tty_kref_put(tty);
 
 	spin_lock_irqsave(&tty->ctrl_lock, flags);
 	clear_bit(TTY_THROTTLED, &tty->flags);
@@ -642,10 +665,6 @@ static void __tty_hangup(struct tty_struct *tty)
 	tty->ctrl_status = 0;
 	spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 
-	/* Account for the p->signal references we killed */
-	while (refs--)
-		tty_kref_put(tty);
-
 	/*
 	 * If one of the devices matches a console pointer, we
 	 * cannot just call hangup() because that will cause