tty_lock: Localise the lock

In each remaining case the tty_lock is associated with a specific tty. This
means we can now lock on a per tty basis. We do need tty_lock_pair() for
the pty case. Uglier but still a step in the right direction.

[fixed up calls in 3 missing drivers - gregkh]

Signed-off-by: Alan Cox <alan@linux.intel.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 13 insertions, 10 deletions

diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index 5505ffc91da4..d6fa8429f3ff 100644
--- a/drivers/tty/pty.c
+++ b/drivers/tty/pty.c
@@ -47,6 +47,7 @@ static void pty_close(struct tty_struct *tty, struct file *filp)
         wake_up_interruptible(&tty->read_wait);
         wake_up_interruptible(&tty->write_wait);
         tty->packet = 0;
+        /* Review - krefs on tty_link ?? */
         if (!tty->link)
                 return;
         tty->link->packet = 0;
@@ -62,9 +63,7 @@ static void pty_close(struct tty_struct *tty, struct file *filp)
                         mutex_unlock(&devpts_mutex);
                 }
 #endif
-                tty_unlock();
                 tty_vhangup(tty->link);
-                tty_lock();
         }
 }
 
@@ -622,26 +621,29 @@ static int ptmx_open(struct inode *inode, struct file *filp)
                 return retval;
 
         /* find a device that is not in use. */
-        tty_lock();
+        mutex_lock(&devpts_mutex);
         index = devpts_new_index(inode);
-        tty_unlock();
         if (index < 0) {
                 retval = index;
                 goto err_file;
         }
 
+        mutex_unlock(&devpts_mutex);
+
         mutex_lock(&tty_mutex);
         mutex_lock(&devpts_mutex);
         tty = tty_init_dev(ptm_driver, index);
-        mutex_unlock(&devpts_mutex);
-        tty_lock();
-        mutex_unlock(&tty_mutex);
 
         if (IS_ERR(tty)) {
                 retval = PTR_ERR(tty);
                 goto out;
         }
 
+        /* The tty returned here is locked so we can safely
+           drop the mutex */
+        mutex_unlock(&devpts_mutex);
+        mutex_unlock(&tty_mutex);
+
         set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
 
         tty_add_file(tty, filp);
@@ -654,16 +656,17 @@ static int ptmx_open(struct inode *inode, struct file *filp)
         if (retval)
                 goto err_release;
 
-        tty_unlock();
+        tty_unlock(tty);
         return 0;
 err_release:
-        tty_unlock();
+        tty_unlock(tty);
         tty_release(inode, filp);
         return retval;
 out:
+        mutex_unlock(&tty_mutex);
         devpts_kill_index(inode, index);
-        tty_unlock();
 err_file:
+        mutex_unlock(&devpts_mutex);
         tty_free_file(filp);
         return retval;
 }