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tty: Remove tty_hung_up_p() tests from tty drivers' open()

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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>
This commit is contained in:
Peter Hurley 2014-06-16 09:17:06 -04:00 committed by Greg Kroah-Hartman
parent 5fda7a0e71
commit e359a4e38d
10 changed files with 21 additions and 61 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
drivers/char/pcmcia/synclink_cs.c
View file

@ -2510,7 +2510,7 @@ static int mgslpc_open(struct tty_struct *tty, struct file * filp)
__FILE__, __LINE__, tty->driver->name, port->count);
/* If port is closing, signal caller to try again */
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));
retval = ((port->flags & ASYNC_HUP_NOTIFY) ?

10
drivers/staging/dgrp/dgrp_tty.c
View file

@ -631,16 +631,6 @@ static int dgrp_tty_open(struct tty_struct *tty, struct file *file)
un->un_tty = tty;
tty->driver_data = un;
/*
* If we are in the middle of hanging up,
* then return an error
*/
if (tty_hung_up_p(file)) {
retval = ((un->un_flag & UN_HUP_NOTIFY) ?
-EAGAIN : -ERESTARTSYS);
goto done;
}
/*
* If the port is in the middle of closing, then block
* until it is done, then try again.

2
drivers/tty/cyclades.c
View file

@ -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;

15
drivers/tty/serial/crisv10.c
View file

@ -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

8
drivers/tty/serial/serial_core.c
View file

@ -1583,14 +1583,6 @@ static int uart_open(struct tty_struct *tty, struct file *filp)
(state->uart_port->flags & UPF_LOW_LATENCY) ? 1 : 0;
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.
*/

10
drivers/tty/synclink.c
View file

@ -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) ?

10
drivers/tty/synclink_gt.c
View file

@ -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--;

11
drivers/tty/synclinkmp.c
View file

@ -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--;

8
drivers/tty/tty_port.c
View file

@ -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);

6
net/irda/ircomm/ircomm_tty.c
View file

@ -320,8 +320,7 @@ static int ircomm_tty_block_til_ready(struct ircomm_tty_cb *self,
__FILE__, __LINE__, tty->driver->name, port->count);
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);
@ -458,8 +457,7 @@ static int ircomm_tty_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) ||
test_bit(ASYNCB_CLOSING, &self->port.flags)) {
if (test_bit(ASYNCB_CLOSING, &self->port.flags)) {
/* Hm, why are we blocking on ASYNC_CLOSING if we
* do return -EAGAIN/-ERESTARTSYS below anyway?