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>

diff --git a/drivers/char/pcmcia/synclink_cs.c b/drivers/char/pcmcia/synclink_cs.c
index 8320abd..a63970f 100644 (file)
--- 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 30d2602..cdd1a69 100644 (file)
--- a/drivers/staging/dgrp/dgrp_tty.c
+++ b/drivers/staging/dgrp/dgrp_tty.c
@@ -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.

diff --git a/drivers/tty/cyclades.c b/drivers/tty/cyclades.c
index a57bb5a..fd66f57 100644 (file)
--- 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 d567ac5..58e6f61 100644 (file)
--- 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 3e08df5..1a5fbf7 100644 (file)
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -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.
         */

diff --git a/drivers/tty/synclink.c b/drivers/tty/synclink.c
index d48e040..b799170 100644 (file)
--- 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 c359a91..ba1dbcd 100644 (file)
--- 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 53ba853..c3f9091 100644 (file)
--- 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 9209d63..1b93357 100644 (file)
--- 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 2ba8b97..61ceb4c 100644 (file)
--- 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?