tty: replace BKL with a new tty_lock
[linux-2.6-block.git] / drivers / char / tty_io.c
index 507441ac6edbcdb9c8fcb58da5d0ba34383eadbc..5ee9081a560f1278cd565388ca301298993a337b 100644 (file)
@@ -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;
 }