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>

10 files changed, 21 insertions, 61 deletions

diff --git a/drivers/char/pcmcia/synclink_cs.c b/drivers/char/pcmcia/synclink_cs.c
index 8320abd1ef14..a63970f76967 100644
--- a/drivers/char/pcmcia/synclink_cs.c
+++ b/drivers/char/pcmcia/synclink_cs.c
@@ -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) ?
diff --git a/drivers/staging/dgrp/dgrp_tty.c b/drivers/staging/dgrp/dgrp_tty.c
index 30d26029b21e..cdd1a69261dd 100644
--- a/drivers/staging/dgrp/dgrp_tty.c
+++ b/drivers/staging/dgrp/dgrp_tty.c
@@ -632,16 +632,6 @@ static int dgrp_tty_open(struct tty_struct *tty, struct file *file)
         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.
          */
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);
 
diff --git a/net/irda/ircomm/ircomm_tty.c b/net/irda/ircomm/ircomm_tty.c
index 2ba8b9705bb7..61ceb4cdb4a2 100644
--- a/net/irda/ircomm/ircomm_tty.c
+++ b/net/irda/ircomm/ircomm_tty.c
@@ -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?