From ddc7b758a6765bd7f853b829104bb7a486a304ad Mon Sep 17 00:00:00 2001
From: Peter Hurley <peter@hurleysoftware.com>
Date: Mon, 16 Jun 2014 09:17:03 -0400
Subject: [PATCH] tty: Move tty->closing from port lock critical section
tty->closing informs the line discipline that the hardware will
be shutting down imminently, and to disable further input other
than soft flow control (but to still allow additional output).
However, the tty lock is the necessary lock for preventing
concurrent changes to tty->closing. As shown by the call-tree
audit [1] of functions that modify tty->closing, the tty lock
is already held for those functions.
[1]
Call-tree audit of functions that modify tty->closing
* does not include call tree to tty_port_close(), tty_port_close_start(),
or tty_port_close_end() which is already documented in
'tty: Document locking for tty_port_close{,start,end}' that shows
callers to those 3 functions hold the tty lock
tty_release()
tty->ops->close() --+
|
__tty_hangup() |
tty->ops->close() --+
|
mp_close():drivers/staging/sb105x/sb_pci_mp.c
dngc_tty_close():drivers/staging/dgnc/dgnc_tty.c
dgap_tty_close():drivers/staging/dgap/dgap_tty.c
dgrp_tty_close():drivers/staging/dgrp/dgrp_tty.c
rp_close():drivers/tty/rocket.c
hvsi_close():drivers/tty/hvc/hvsi.c
rs_close():drivers/tty/serial/68328serial.c
rs_close():drivers/tty/serial/crisv10.c
uart_close():drivers/tty/serial/serial_core.c
isdn_tty_close():drivers/isdn/i4l/isdn_tty.c
tty3215_close():drivers/s390/char/con3215.c
tty_open()
tty_ldisc_setup() ----+
|
__tty_hangup() |
tty_ldisc_hangup() ---+
|
tty_set_ldisc() --------+
tty_ldisc_restore() --+
|
+- tty_ldisc_open()
ld->ops->open() --+
|
+- n_tty_open()
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/tty/serial/serial_core.c | 2 +-
drivers/tty/tty_port.c | 6 ++++--
2 files changed, 5 insertions(+), 3 deletions(-)
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 127ac6c8fd400..3e08df52d68de 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -1368,8 +1368,8 @@ static void uart_close(struct tty_struct *tty, struct file *filp)
tty_ldisc_flush(tty);
tty_port_tty_set(port, NULL);
- spin_lock_irqsave(&port->lock, flags);
tty->closing = 0;
+ spin_lock_irqsave(&port->lock, flags);
if (port->blocked_open) {
spin_unlock_irqrestore(&port->lock, flags);
diff --git a/drivers/tty/tty_port.c b/drivers/tty/tty_port.c
index 7309594e1c12d..9209d6331b8ee 100644
--- a/drivers/tty/tty_port.c
+++ b/drivers/tty/tty_port.c
@@ -497,9 +497,10 @@ int tty_port_close_start(struct tty_port *port,
return 0;
}
set_bit(ASYNCB_CLOSING, &port->flags);
- tty->closing = 1;
spin_unlock_irqrestore(&port->lock, flags);
+ tty->closing = 1;
+
if (test_bit(ASYNCB_INITIALIZED, &port->flags)) {
/* Don't block on a stalled port, just pull the chain */
if (tty->flow_stopped)
@@ -522,9 +523,10 @@ void tty_port_close_end(struct tty_port *port, struct tty_struct *tty)
{
unsigned long flags;
- spin_lock_irqsave(&port->lock, flags);
tty->closing = 0;
+ spin_lock_irqsave(&port->lock, flags);
+
if (port->blocked_open) {
spin_unlock_irqrestore(&port->lock, flags);
if (port->close_delay) {