[PATCH] ppp ldisc close deadlock prevention

Jeff Garzik writes:

> So what was the resolution of this?

This patch is what we want.  We don't in fact need to do the read
lock, only the write lock, which is what the original patch did.
However, we need to do it in ppp_synctty.c as well as ppp_async.c.

Thanks to John K Luebs <jkluebs@luebsphoto.com> for pointing out the
problem.
Signed-off-by: Paul Mackerras <paulus@samba.org>

drivers/net/ppp_async.c

@@ -205,10 +205,10 @@ ppp_asynctty_close(struct tty_struct *tty)
 {
 	struct asyncppp *ap;
 
-	write_lock(&disc_data_lock);
+	write_lock_irq(&disc_data_lock);
 	ap = tty->disc_data;
 	tty->disc_data = 0;
-	write_unlock(&disc_data_lock);
+	write_unlock_irq(&disc_data_lock);
 	if (ap == 0)
 		return;
 

drivers/net/ppp_synctty.c

@@ -251,10 +251,10 @@ ppp_sync_close(struct tty_struct *tty)
 {
 	struct syncppp *ap;
 
-	write_lock(&disc_data_lock);
+	write_lock_irq(&disc_data_lock);
 	ap = tty->disc_data;
 	tty->disc_data = 0;
-	write_unlock(&disc_data_lock);
+	write_unlock_irq(&disc_data_lock);
 	if (ap == 0)
 		return;