tty: replace BKL with a new tty_lock

As a preparation for replacing the big kernel lock
in the TTY layer, wrap all the callers in new
macros tty_lock, tty_lock_nested and tty_unlock.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 64 insertions, 51 deletions

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index 507441ac6edb..5ee9081a560f 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -149,6 +149,7 @@ static long tty_compat_ioctl(struct file *file, unsigned int cmd,
 #else
 #define tty_compat_ioctl NULL
 #endif
+static int __tty_fasync(int fd, struct file *filp, int on);
 static int tty_fasync(int fd, struct file *filp, int on);
 static void release_tty(struct tty_struct *tty, int idx);
 static void __proc_set_tty(struct task_struct *tsk, struct tty_struct *tty);
@@ -483,7 +484,7 @@ EXPORT_SYMBOL_GPL(tty_wakeup);
  *      remains intact.
  *
  *      Locking:
- *              BKL
+ *              BTM
  *                redirect lock for undoing redirection
  *                file list lock for manipulating list of ttys
  *                tty_ldisc_lock from called functions
@@ -513,8 +514,11 @@ static void do_tty_hangup(struct work_struct *work)
         }
         spin_unlock(&redirect_lock);
 
-        /* inuse_filps is protected by the single kernel lock */
-        lock_kernel();
+        /* inuse_filps is protected by the single tty lock,
+           this really needs to change if we want to flush the
+           workqueue with the lock held */
+        tty_lock_nested(); /* called with BTM held from pty_close and
+                                others */
         check_tty_count(tty, "do_tty_hangup");
 
         file_list_lock();
@@ -525,7 +529,7 @@ static void do_tty_hangup(struct work_struct *work)
                 if (filp->f_op->write != tty_write)
                         continue;
                 closecount++;
-                tty_fasync(-1, filp, 0);        /* can't block */
+                __tty_fasync(-1, filp, 0);      /* can't block */
                 filp->f_op = &hung_up_tty_fops;
         }
         file_list_unlock();
@@ -594,7 +598,7 @@ static void do_tty_hangup(struct work_struct *work)
          */
         set_bit(TTY_HUPPED, &tty->flags);
         tty_ldisc_enable(tty);
-        unlock_kernel();
+        tty_unlock();
         if (f)
                 fput(f);
 }
@@ -696,7 +700,8 @@ static void session_clear_tty(struct pid *session)
  *      exiting; it is 0 if called by the ioctl TIOCNOTTY.
  *
  *      Locking:
- *              BKL is taken for hysterical raisins
+ *              BTM is taken for hysterical raisins, and held when
+ *                called from no_tty().
  *                tty_mutex is taken to protect tty
  *                ->siglock is taken to protect ->signal/->sighand
  *                tasklist_lock is taken to walk process list for sessions
@@ -714,10 +719,10 @@ void disassociate_ctty(int on_exit)
         tty = get_current_tty();
         if (tty) {
                 tty_pgrp = get_pid(tty->pgrp);
-                lock_kernel();
+                tty_lock_nested(); /* see above */
                 if (on_exit && tty->driver->type != TTY_DRIVER_TYPE_PTY)
                         tty_vhangup(tty);
-                unlock_kernel();
+                tty_unlock();
                 tty_kref_put(tty);
         } else if (on_exit) {
                 struct pid *old_pgrp;
@@ -774,9 +779,9 @@ void disassociate_ctty(int on_exit)
 void no_tty(void)
 {
         struct task_struct *tsk = current;
-        lock_kernel();
+        tty_lock();
         disassociate_ctty(0);
-        unlock_kernel();
+        tty_unlock();
         proc_clear_tty(tsk);
 }
 
@@ -1013,19 +1018,19 @@ out:
  * We don't put it into the syslog queue right now maybe in the future if
  * really needed.
  *
- * We must still hold the BKL and test the CLOSING flag for the moment.
+ * We must still hold the BTM and test the CLOSING flag for the moment.
  */
 
 void tty_write_message(struct tty_struct *tty, char *msg)
 {
         if (tty) {
                 mutex_lock(&tty->atomic_write_lock);
-                lock_kernel();
+                tty_lock();
                 if (tty->ops->write && !test_bit(TTY_CLOSING, &tty->flags)) {
-                        unlock_kernel();
+                        tty_unlock();
                         tty->ops->write(tty, msg, strlen(msg));
                 } else
-                        unlock_kernel();
+                        tty_unlock();
                 tty_write_unlock(tty);
         }
         return;
@@ -1208,18 +1213,18 @@ static int tty_driver_install_tty(struct tty_driver *driver,
         int ret;
 
         if (driver->ops->install) {
-                lock_kernel();
+                tty_lock_nested(); /* already called with BTM held */
                 ret = driver->ops->install(driver, tty);
-                unlock_kernel();
+                tty_unlock();
                 return ret;
         }
 
         if (tty_init_termios(tty) == 0) {
-                lock_kernel();
+                tty_lock_nested();
                 tty_driver_kref_get(driver);
                 tty->count++;
                 driver->ttys[idx] = tty;
-                unlock_kernel();
+                tty_unlock();
                 return 0;
         }
         return -ENOMEM;
@@ -1312,14 +1317,15 @@ struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx,
         struct tty_struct *tty;
         int retval;
 
-        lock_kernel();
+        tty_lock_nested(); /* always called with tty lock held already */
+
         /* Check if pty master is being opened multiple times */
         if (driver->subtype == PTY_TYPE_MASTER &&
                 (driver->flags & TTY_DRIVER_DEVPTS_MEM) && !first_ok) {
-                unlock_kernel();
+                tty_unlock();
                 return ERR_PTR(-EIO);
         }
-        unlock_kernel();
+        tty_unlock();
 
         /*
          * First time open is complex, especially for PTY devices.
@@ -1363,9 +1369,9 @@ release_mem_out:
         if (printk_ratelimit())
                 printk(KERN_INFO "tty_init_dev: ldisc open failed, "
                                  "clearing slot %d\n", idx);
-        lock_kernel();
+        tty_lock_nested();
         release_tty(tty, idx);
-        unlock_kernel();
+        tty_unlock();
         return ERR_PTR(retval);
 }
 
@@ -1512,10 +1518,10 @@ int tty_release(struct inode *inode, struct file *filp)
         if (tty_paranoia_check(tty, inode, "tty_release_dev"))
                 return 0;
 
-        lock_kernel();
+        tty_lock();
         check_tty_count(tty, "tty_release_dev");
 
-        tty_fasync(-1, filp, 0);
+        __tty_fasync(-1, filp, 0);
 
         idx = tty->index;
         pty_master = (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
@@ -1527,18 +1533,18 @@ int tty_release(struct inode *inode, struct file *filp)
         if (idx < 0 || idx >= tty->driver->num) {
                 printk(KERN_DEBUG "tty_release_dev: bad idx when trying to "
                                   "free (%s)\n", tty->name);
-                unlock_kernel();
+                tty_unlock();
                 return 0;
         }
         if (!devpts) {
                 if (tty != tty->driver->ttys[idx]) {
-                        unlock_kernel();
+                        tty_unlock();
                         printk(KERN_DEBUG "tty_release_dev: driver.table[%d] not tty "
                                "for (%s)\n", idx, tty->name);
                         return 0;
                 }
                 if (tty->termios != tty->driver->termios[idx]) {
-                        unlock_kernel();
+                        tty_unlock();
                         printk(KERN_DEBUG "tty_release_dev: driver.termios[%d] not termios "
                                "for (%s)\n",
                                idx, tty->name);
@@ -1556,21 +1562,21 @@ int tty_release(struct inode *inode, struct file *filp)
         if (tty->driver->other &&
              !(tty->driver->flags & TTY_DRIVER_DEVPTS_MEM)) {
                 if (o_tty != tty->driver->other->ttys[idx]) {
-                        unlock_kernel();
+                        tty_unlock();
                         printk(KERN_DEBUG "tty_release_dev: other->table[%d] "
                                           "not o_tty for (%s)\n",
                                idx, tty->name);
                         return 0 ;
                 }
                 if (o_tty->termios != tty->driver->other->termios[idx]) {
-                        unlock_kernel();
+                        tty_unlock();
                         printk(KERN_DEBUG "tty_release_dev: other->termios[%d] "
                                           "not o_termios for (%s)\n",
                                idx, tty->name);
                         return 0;
                 }
                 if (o_tty->link != tty) {
-                        unlock_kernel();
+                        tty_unlock();
                         printk(KERN_DEBUG "tty_release_dev: bad pty pointers\n");
                         return 0;
                 }
@@ -1579,7 +1585,7 @@ int tty_release(struct inode *inode, struct file *filp)
         if (tty->ops->close)
                 tty->ops->close(tty, filp);
 
-        unlock_kernel();
+        tty_unlock();
         /*
          * Sanity check: if tty->count is going to zero, there shouldn't be
          * any waiters on tty->read_wait or tty->write_wait.  We test the
@@ -1602,7 +1608,7 @@ int tty_release(struct inode *inode, struct file *filp)
                    opens on /dev/tty */
 
                 mutex_lock(&tty_mutex);
-                lock_kernel();
+                tty_lock();
                 tty_closing = tty->count <= 1;
                 o_tty_closing = o_tty &&
                         (o_tty->count <= (pty_master ? 1 : 0));
@@ -1633,7 +1639,7 @@ int tty_release(struct inode *inode, struct file *filp)
 
                 printk(KERN_WARNING "tty_release_dev: %s: read/write wait queue "
                                     "active!\n", tty_name(tty, buf));
-                unlock_kernel();
+                tty_unlock();
                 mutex_unlock(&tty_mutex);
                 schedule();
         }
@@ -1698,7 +1704,7 @@ int tty_release(struct inode *inode, struct file *filp)
 
         /* check whether both sides are closing ... */
         if (!tty_closing || (o_tty && !o_tty_closing)) {
-                unlock_kernel();
+                tty_unlock();
                 return 0;
         }
 
@@ -1718,7 +1724,7 @@ int tty_release(struct inode *inode, struct file *filp)
         /* Make this pty number available for reallocation */
         if (devpts)
                 devpts_kill_index(inode, idx);
-        unlock_kernel();
+        tty_unlock();
         return 0;
 }
 
@@ -1760,12 +1766,12 @@ retry_open:
         retval = 0;
 
         mutex_lock(&tty_mutex);
-        lock_kernel();
+        tty_lock();
 
         if (device == MKDEV(TTYAUX_MAJOR, 0)) {
                 tty = get_current_tty();
                 if (!tty) {
-                        unlock_kernel();
+                        tty_unlock();
                         mutex_unlock(&tty_mutex);
                         return -ENXIO;
                 }
@@ -1797,14 +1803,14 @@ retry_open:
                                 goto got_driver;
                         }
                 }
-                unlock_kernel();
+                tty_unlock();
                 mutex_unlock(&tty_mutex);
                 return -ENODEV;
         }
 
         driver = get_tty_driver(device, &index);
         if (!driver) {
-                unlock_kernel();
+                tty_unlock();
                 mutex_unlock(&tty_mutex);
                 return -ENODEV;
         }
@@ -1814,7 +1820,7 @@ got_driver:
                 tty = tty_driver_lookup_tty(driver, inode, index);
 
                 if (IS_ERR(tty)) {
-                        unlock_kernel();
+                        tty_unlock();
                         mutex_unlock(&tty_mutex);
                         return PTR_ERR(tty);
                 }
@@ -1830,7 +1836,7 @@ got_driver:
         mutex_unlock(&tty_mutex);
         tty_driver_kref_put(driver);
         if (IS_ERR(tty)) {
-                unlock_kernel();
+                tty_unlock();
                 return PTR_ERR(tty);
         }
 
@@ -1862,11 +1868,11 @@ got_driver:
 #endif
                 tty_release(inode, filp);
                 if (retval != -ERESTARTSYS) {
-                        unlock_kernel();
+                        tty_unlock();
                         return retval;
                 }
                 if (signal_pending(current)) {
-                        unlock_kernel();
+                        tty_unlock();
                         return retval;
                 }
                 schedule();
@@ -1875,14 +1881,14 @@ got_driver:
                  */
                 if (filp->f_op == &hung_up_tty_fops)
                         filp->f_op = &tty_fops;
-                unlock_kernel();
+                tty_unlock();
                 goto retry_open;
         }
-        unlock_kernel();
+        tty_unlock();
 
 
         mutex_lock(&tty_mutex);
-        lock_kernel();
+        tty_lock();
         spin_lock_irq(&current->sighand->siglock);
         if (!noctty &&
             current->signal->leader &&
@@ -1890,7 +1896,7 @@ got_driver:
             tty->session == NULL)
                 __proc_set_tty(current, tty);
         spin_unlock_irq(&current->sighand->siglock);
-        unlock_kernel();
+        tty_unlock();
         mutex_unlock(&tty_mutex);
         return 0;
 }
@@ -1926,13 +1932,12 @@ static unsigned int tty_poll(struct file *filp, poll_table *wait)
         return ret;
 }
 
-static int tty_fasync(int fd, struct file *filp, int on)
+static int __tty_fasync(int fd, struct file *filp, int on)
 {
         struct tty_struct *tty;
         unsigned long flags;
         int retval = 0;
 
-        lock_kernel();
         tty = (struct tty_struct *)filp->private_data;
         if (tty_paranoia_check(tty, filp->f_path.dentry->d_inode, "tty_fasync"))
                 goto out;
@@ -1966,7 +1971,15 @@ static int tty_fasync(int fd, struct file *filp, int on)
         }
         retval = 0;
 out:
-        unlock_kernel();
+        return retval;
+}
+
+static int tty_fasync(int fd, struct file *filp, int on)
+{
+        int retval;
+        tty_lock();
+        retval = __tty_fasync(fd, filp, on);
+        tty_unlock();
         return retval;
 }