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authorPeter Hurley <peter@hurleysoftware.com>2014-06-16 09:17:06 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-07-10 16:06:49 -0700
commite359a4e38d229d53e28905863a1fabf41debd591 (patch)
treec70f7762dac31dad62188b7b8bb2140bea8b311a /drivers/tty
parent5fda7a0e715c32c6dd9a39ebce8429eeafb64b7d (diff)
downloadlinux-e359a4e38d229d53e28905863a1fabf41debd591.tar.bz2
tty: Remove tty_hung_up_p() tests from tty drivers' open()
Since at least before 2.6.30, it has not been possible to observe a hung up file pointer in a tty driver's open() method unless/until the driver open() releases the tty_lock() (eg., before blocking). This is because tty_open() adds the file pointer while holding the tty_lock() _and_ doesn't release the lock until after calling the tty driver's open() method. [ Before tty_lock(), this was lock_kernel(). ] Since __tty_hangup() first waits on the tty_lock() before enumerating and hanging up the open file pointers, either __tty_hangup() will wait for the tty_lock() or tty_open() will not yet have added the file pointer. For example, CPU 0 | CPU 1 | tty_open | __tty_hangup .. | .. tty_lock | .. tty_reopen | tty_lock / blocks .. | tty_add_file(tty, filp) | .. | tty->ops->open(tty, filp) | tty_port_open | tty_port_block_til_ready | .. | while (1) | .. | tty_unlock | / unblocks schedule | for each filp on tty->tty_files | f_ops = tty_hung_up_fops; | .. | tty_unlock tty_lock | .. | tty_unlock | Note that since tty_port_block_til_ready() and similar drop the tty_lock while blocking, when woken, the file pointer must then be tested for having been hung up. Also, fix bit-rotted drivers that used extra_count to track the port->count bump. CC: Mikael Starvik <starvik@axis.com> CC: Samuel Ortiz <samuel@sortiz.org> CC: "David S. Miller" <davem@davemloft.net> Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Acked-by: Jesper Nilsson <jesper.nilsson@axis.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty')
-rw-r--r--drivers/tty/cyclades.c2
-rw-r--r--drivers/tty/serial/crisv10.c15
-rw-r--r--drivers/tty/serial/serial_core.c8
-rw-r--r--drivers/tty/synclink.c10
-rw-r--r--drivers/tty/synclink_gt.c10
-rw-r--r--drivers/tty/synclinkmp.c11
-rw-r--r--drivers/tty/tty_port.c8
7 files changed, 18 insertions, 46 deletions
diff --git a/drivers/tty/cyclades.c b/drivers/tty/cyclades.c
index a57bb5ab761c..fd66f57390d0 100644
--- a/drivers/tty/cyclades.c
+++ b/drivers/tty/cyclades.c
@@ -1579,7 +1579,7 @@ static int cy_open(struct tty_struct *tty, struct file *filp)
/*
* If the port is the middle of closing, bail out now
*/
- if (tty_hung_up_p(filp) || (info->port.flags & ASYNC_CLOSING)) {
+ if (info->port.flags & ASYNC_CLOSING) {
wait_event_interruptible_tty(tty, info->port.close_wait,
!(info->port.flags & ASYNC_CLOSING));
return (info->port.flags & ASYNC_HUP_NOTIFY) ? -EAGAIN: -ERESTARTSYS;
diff --git a/drivers/tty/serial/crisv10.c b/drivers/tty/serial/crisv10.c
index d567ac5d3af4..58e6f61a87e4 100644
--- a/drivers/tty/serial/crisv10.c
+++ b/drivers/tty/serial/crisv10.c
@@ -3831,14 +3831,13 @@ block_til_ready(struct tty_struct *tty, struct file * filp,
DECLARE_WAITQUEUE(wait, current);
unsigned long flags;
int retval;
- int do_clocal = 0, extra_count = 0;
+ int do_clocal = 0;
/*
* If the device is in the middle of being closed, then block
* until it's done, and then try again.
*/
- if (tty_hung_up_p(filp) ||
- (info->port.flags & ASYNC_CLOSING)) {
+ if (info->port.flags & ASYNC_CLOSING) {
wait_event_interruptible_tty(tty, info->port.close_wait,
!(info->port.flags & ASYNC_CLOSING));
#ifdef SERIAL_DO_RESTART
@@ -3879,10 +3878,7 @@ block_til_ready(struct tty_struct *tty, struct file * filp,
info->line, info->port.count);
#endif
local_irq_save(flags);
- if (!tty_hung_up_p(filp)) {
- extra_count++;
- info->port.count--;
- }
+ info->port.count--;
local_irq_restore(flags);
info->port.blocked_open++;
while (1) {
@@ -3921,7 +3917,7 @@ block_til_ready(struct tty_struct *tty, struct file * filp,
}
set_current_state(TASK_RUNNING);
remove_wait_queue(&info->port.open_wait, &wait);
- if (extra_count)
+ if (!tty_hung_up_p(filp))
info->port.count++;
info->port.blocked_open--;
#ifdef SERIAL_DEBUG_OPEN
@@ -3976,8 +3972,7 @@ rs_open(struct tty_struct *tty, struct file * filp)
/*
* If the port is in the middle of closing, bail out now
*/
- if (tty_hung_up_p(filp) ||
- (info->port.flags & ASYNC_CLOSING)) {
+ if (info->port.flags & ASYNC_CLOSING) {
wait_event_interruptible_tty(tty, info->port.close_wait,
!(info->port.flags & ASYNC_CLOSING));
#ifdef SERIAL_DO_RESTART
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 3e08df52d68d..1a5fbf7ab347 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -1584,14 +1584,6 @@ static int uart_open(struct tty_struct *tty, struct file *filp)
tty_port_tty_set(port, tty);
/*
- * If the port is in the middle of closing, bail out now.
- */
- if (tty_hung_up_p(filp)) {
- retval = -EAGAIN;
- goto err_dec_count;
- }
-
- /*
* Start up the serial port.
*/
retval = uart_startup(tty, state, 0);
diff --git a/drivers/tty/synclink.c b/drivers/tty/synclink.c
index d48e040cd8c5..b7991707ffc0 100644
--- a/drivers/tty/synclink.c
+++ b/drivers/tty/synclink.c
@@ -3267,7 +3267,6 @@ static int block_til_ready(struct tty_struct *tty, struct file * filp,
DECLARE_WAITQUEUE(wait, current);
int retval;
bool do_clocal = false;
- bool extra_count = false;
unsigned long flags;
int dcd;
struct tty_port *port = &info->port;
@@ -3300,10 +3299,7 @@ static int block_til_ready(struct tty_struct *tty, struct file * filp,
__FILE__,__LINE__, tty->driver->name, port->count );
spin_lock_irqsave(&info->irq_spinlock, flags);
- if (!tty_hung_up_p(filp)) {
- extra_count = true;
- port->count--;
- }
+ port->count--;
spin_unlock_irqrestore(&info->irq_spinlock, flags);
port->blocked_open++;
@@ -3342,7 +3338,7 @@ static int block_til_ready(struct tty_struct *tty, struct file * filp,
remove_wait_queue(&port->open_wait, &wait);
/* FIXME: Racy on hangup during close wait */
- if (extra_count)
+ if (!tty_hung_up_p(filp))
port->count++;
port->blocked_open--;
@@ -3403,7 +3399,7 @@ static int mgsl_open(struct tty_struct *tty, struct file * filp)
__FILE__,__LINE__,tty->driver->name, info->port.count);
/* If port is closing, signal caller to try again */
- if (tty_hung_up_p(filp) || info->port.flags & ASYNC_CLOSING){
+ if (info->port.flags & ASYNC_CLOSING){
wait_event_interruptible_tty(tty, info->port.close_wait,
!(info->port.flags & ASYNC_CLOSING));
retval = ((info->port.flags & ASYNC_HUP_NOTIFY) ?
diff --git a/drivers/tty/synclink_gt.c b/drivers/tty/synclink_gt.c
index c359a91f7346..ba1dbcdf4609 100644
--- a/drivers/tty/synclink_gt.c
+++ b/drivers/tty/synclink_gt.c
@@ -673,7 +673,7 @@ static int open(struct tty_struct *tty, struct file *filp)
DBGINFO(("%s open, old ref count = %d\n", info->device_name, info->port.count));
/* If port is closing, signal caller to try again */
- if (tty_hung_up_p(filp) || info->port.flags & ASYNC_CLOSING){
+ if (info->port.flags & ASYNC_CLOSING){
wait_event_interruptible_tty(tty, info->port.close_wait,
!(info->port.flags & ASYNC_CLOSING));
retval = ((info->port.flags & ASYNC_HUP_NOTIFY) ?
@@ -3273,7 +3273,6 @@ static int block_til_ready(struct tty_struct *tty, struct file *filp,
DECLARE_WAITQUEUE(wait, current);
int retval;
bool do_clocal = false;
- bool extra_count = false;
unsigned long flags;
int cd;
struct tty_port *port = &info->port;
@@ -3300,10 +3299,7 @@ static int block_til_ready(struct tty_struct *tty, struct file *filp,
add_wait_queue(&port->open_wait, &wait);
spin_lock_irqsave(&info->lock, flags);
- if (!tty_hung_up_p(filp)) {
- extra_count = true;
- port->count--;
- }
+ port->count--;
spin_unlock_irqrestore(&info->lock, flags);
port->blocked_open++;
@@ -3338,7 +3334,7 @@ static int block_til_ready(struct tty_struct *tty, struct file *filp,
set_current_state(TASK_RUNNING);
remove_wait_queue(&port->open_wait, &wait);
- if (extra_count)
+ if (!tty_hung_up_p(filp))
port->count++;
port->blocked_open--;
diff --git a/drivers/tty/synclinkmp.c b/drivers/tty/synclinkmp.c
index 53ba8537de8d..c3f90910fed9 100644
--- a/drivers/tty/synclinkmp.c
+++ b/drivers/tty/synclinkmp.c
@@ -753,7 +753,7 @@ static int open(struct tty_struct *tty, struct file *filp)
__FILE__,__LINE__,tty->driver->name, info->port.count);
/* If port is closing, signal caller to try again */
- if (tty_hung_up_p(filp) || info->port.flags & ASYNC_CLOSING){
+ if (info->port.flags & ASYNC_CLOSING){
wait_event_interruptible_tty(tty, info->port.close_wait,
!(info->port.flags & ASYNC_CLOSING));
retval = ((info->port.flags & ASYNC_HUP_NOTIFY) ?
@@ -3288,7 +3288,6 @@ static int block_til_ready(struct tty_struct *tty, struct file *filp,
DECLARE_WAITQUEUE(wait, current);
int retval;
bool do_clocal = false;
- bool extra_count = false;
unsigned long flags;
int cd;
struct tty_port *port = &info->port;
@@ -3322,10 +3321,7 @@ static int block_til_ready(struct tty_struct *tty, struct file *filp,
__FILE__,__LINE__, tty->driver->name, port->count );
spin_lock_irqsave(&info->lock, flags);
- if (!tty_hung_up_p(filp)) {
- extra_count = true;
- port->count--;
- }
+ port->count--;
spin_unlock_irqrestore(&info->lock, flags);
port->blocked_open++;
@@ -3362,8 +3358,7 @@ static int block_til_ready(struct tty_struct *tty, struct file *filp,
set_current_state(TASK_RUNNING);
remove_wait_queue(&port->open_wait, &wait);
-
- if (extra_count)
+ if (!tty_hung_up_p(filp))
port->count++;
port->blocked_open--;
diff --git a/drivers/tty/tty_port.c b/drivers/tty/tty_port.c
index 9209d6331b8e..1b9335796da4 100644
--- a/drivers/tty/tty_port.c
+++ b/drivers/tty/tty_port.c
@@ -365,7 +365,7 @@ int tty_port_block_til_ready(struct tty_port *port,
DEFINE_WAIT(wait);
/* block if port is in the process of being closed */
- if (tty_hung_up_p(filp) || port->flags & ASYNC_CLOSING) {
+ if (port->flags & ASYNC_CLOSING) {
wait_event_interruptible_tty(tty, port->close_wait,
!(port->flags & ASYNC_CLOSING));
if (port->flags & ASYNC_HUP_NOTIFY)
@@ -399,8 +399,7 @@ int tty_port_block_til_ready(struct tty_port *port,
/* The port lock protects the port counts */
spin_lock_irqsave(&port->lock, flags);
- if (!tty_hung_up_p(filp))
- port->count--;
+ port->count--;
port->blocked_open++;
spin_unlock_irqrestore(&port->lock, flags);
@@ -593,8 +592,7 @@ int tty_port_open(struct tty_port *port, struct tty_struct *tty,
struct file *filp)
{
spin_lock_irq(&port->lock);
- if (!tty_hung_up_p(filp))
- ++port->count;
+ ++port->count;
spin_unlock_irq(&port->lock);
tty_port_tty_set(port, tty);