more tty closing fixes

Hi Greg,

These 3 patches are stragglers from the old tty closing series. I'm still working on eliminating ASYNC_CLOSING and the improvements to opening in O_NONBLOCK mode.

Regards,

Peter Hurley (3):
tty: Move tty hung up check from port->lock critical section
tty: Convert tty->closing to int
tty: Flush tty buffers after hardware shutdown

 drivers/tty/tty_port.c | 7 +++----
 include/linux/tty.h    | 2 +-
 2 files changed, 4 insertions(+), 5 deletions(-)

2.1.3

The port->lock does not protect the filp->f_op field; move the tty_hung_up_p() test outside the port->lock critical section in tty_port_close_start().

---
 drivers/tty/tty_port.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

index 1b93357..3b641d1 100644
@@ -473,12 +473,10 @@ int tty_port_close_start(struct tty_port *port,
 {
 	unsigned long flags;
 
-	spin_lock_irqsave(&port->lock, flags);
-	if (tty_hung_up_p(filp)) {
-		spin_unlock_irqrestore(&port->lock, flags);
+	if (tty_hung_up_p(filp))
 		return 0;
-	}
 
+	spin_lock_irqsave(&port->lock, flags);
 	if (tty->count == 1 && port->count != 1) {
 		printk(KERN_WARNING
 		    "tty_port_close_start: tty->count = 1 port count = %d.\n",

2.1.3

tty->closing is a bitfield member; prevent corruption from non-atomic update by assigning a unique memory location.

---
 include/linux/tty.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index c52a689..7d66ae5 100644
@@ -284,7 +284,7 @@ struct tty_struct {
 
 #define N_TTY_BUF_SIZE 4096
 
-	unsigned char closing:1;
+	int closing;
 	unsigned char *write_buf;
 	int write_cnt;
 	/* If the tty has a pending do_SAK, queue it here - akpm */

2.1.3

The line discipline buffer and the tty buffers must be flushed again after hardware shutdown; otherwise, a brief window exists between the ldisc flush in tty_port_close_start() and the subsequent tty_port_shutdown(), during which more data could be received into the tty buffers. A racing open might then be able to receive data from the previous session.

---
 drivers/tty/tty_port.c | 1 +
 1 file changed, 1 insertion(+)

index 3b641d1..4d9abaa 100644
@@ -520,6 +520,7 @@ void tty_port_close_end(struct tty_port *port, struct tty_struct *tty)
 {
 	unsigned long flags;
 
+	tty_ldisc_flush(tty);
 	tty->closing = 0;
 
 	spin_lock_irqsave(&port->lock, flags);

2.1.3