tty: remove tty_lock_nested

This changes all remaining users of tty_lock_nested
to be non-recursive, which lets us kill this function.
As a consequence, we won't need to keep the lock count
any more, which allows more simplifications later.

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>

4 files changed, 24 insertions, 26 deletions

diff --git a/drivers/char/pty.c b/drivers/char/pty.c
index de22ea952832..f2d7a76fab54 100644
--- a/drivers/char/pty.c
+++ b/drivers/char/pty.c
@@ -62,7 +62,7 @@ static void pty_close(struct tty_struct *tty, struct file *filp)
                 if (tty->driver == ptm_driver)
                         devpts_pty_kill(tty->link);
 #endif
-                tty_vhangup(tty->link);
+                tty_vhangup_locked(tty->link);
         }
 }
 
diff --git a/drivers/char/selection.c b/drivers/char/selection.c
index 75889cd9375f..ebae344ce910 100644
--- a/drivers/char/selection.c
+++ b/drivers/char/selection.c
@@ -313,7 +313,8 @@ int paste_selection(struct tty_struct *tty)
         struct  tty_ldisc *ld;
         DECLARE_WAITQUEUE(wait, current);
 
-        tty_lock_nested(); /* always called with BTM from vt_ioctl */
+        /* always called with BTM from vt_ioctl */
+        WARN_ON(!tty_locked());
 
         acquire_console_sem();
         poke_blanked_console();
@@ -343,6 +344,5 @@ int paste_selection(struct tty_struct *tty)
         __set_current_state(TASK_RUNNING);
 
         tty_ldisc_deref(ld);
-        tty_unlock();
         return 0;
 }
diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index bb22cf495435..dcf7d368639e 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -492,10 +492,8 @@ EXPORT_SYMBOL_GPL(tty_wakeup);
  *                tasklist_lock to walk task list for hangup event
  *                  ->siglock to protect ->signal/->sighand
  */
-static void do_tty_hangup(struct work_struct *work)
+void tty_vhangup_locked(struct tty_struct *tty)
 {
-        struct tty_struct *tty =
-                container_of(work, struct tty_struct, hangup_work);
         struct file *cons_filp = NULL;
         struct file *filp, *f = NULL;
         struct task_struct *p;
@@ -517,8 +515,6 @@ static void do_tty_hangup(struct work_struct *work)
         /* 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();
@@ -598,11 +594,20 @@ static void do_tty_hangup(struct work_struct *work)
          */
         set_bit(TTY_HUPPED, &tty->flags);
         tty_ldisc_enable(tty);
-        tty_unlock();
         if (f)
                 fput(f);
 }
 
+static void do_tty_hangup(struct work_struct *work)
+{
+        struct tty_struct *tty =
+                container_of(work, struct tty_struct, hangup_work);
+
+        tty_lock();
+        tty_vhangup_locked(tty);
+        tty_unlock();
+}
+
 /**
  *      tty_hangup              -       trigger a hangup event
  *      @tty: tty to hangup
@@ -638,7 +643,9 @@ void tty_vhangup(struct tty_struct *tty)
 
         printk(KERN_DEBUG "%s vhangup...\n", tty_name(tty, buf));
 #endif
-        do_tty_hangup(&tty->hangup_work);
+        tty_lock();
+        tty_vhangup_locked(tty);
+        tty_unlock();
 }
 
 EXPORT_SYMBOL(tty_vhangup);
@@ -719,10 +726,12 @@ void disassociate_ctty(int on_exit)
         tty = get_current_tty();
         if (tty) {
                 tty_pgrp = get_pid(tty->pgrp);
-                tty_lock_nested(); /* see above */
-                if (on_exit && tty->driver->type != TTY_DRIVER_TYPE_PTY)
-                        tty_vhangup(tty);
-                tty_unlock();
+                if (on_exit) {
+                        tty_lock();
+                        if (tty->driver->type != TTY_DRIVER_TYPE_PTY)
+                                tty_vhangup_locked(tty);
+                        tty_unlock();
+                }
                 tty_kref_put(tty);
         } else if (on_exit) {
                 struct pid *old_pgrp;
@@ -1213,18 +1222,14 @@ static int tty_driver_install_tty(struct tty_driver *driver,
         int ret;
 
         if (driver->ops->install) {
-                tty_lock_nested(); /* already called with BTM held */
                 ret = driver->ops->install(driver, tty);
-                tty_unlock();
                 return ret;
         }
 
         if (tty_init_termios(tty) == 0) {
-                tty_lock_nested();
                 tty_driver_kref_get(driver);
                 tty->count++;
                 driver->ttys[idx] = tty;
-                tty_unlock();
                 return 0;
         }
         return -ENOMEM;
@@ -1317,15 +1322,11 @@ struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx,
         struct tty_struct *tty;
         int retval;
 
-        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) {
-                tty_unlock();
                 return ERR_PTR(-EIO);
         }
-        tty_unlock();
 
         /*
          * First time open is complex, especially for PTY devices.
@@ -1369,9 +1370,7 @@ release_mem_out:
         if (printk_ratelimit())
                 printk(KERN_INFO "tty_init_dev: ldisc open failed, "
                                  "clearing slot %d\n", idx);
-        tty_lock_nested();
         release_tty(tty, idx);
-        tty_unlock();
         return ERR_PTR(retval);
 }
 
diff --git a/drivers/char/tty_ldisc.c b/drivers/char/tty_ldisc.c
index 0f494799da89..412f9775d19c 100644
--- a/drivers/char/tty_ldisc.c
+++ b/drivers/char/tty_ldisc.c
@@ -450,9 +450,8 @@ static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld)
         if (ld->ops->open) {
                 int ret;
                 /* BTM here locks versus a hangup event */
-                tty_lock_nested(); /* always held here already */
+                WARN_ON(!tty_locked());
                 ret = ld->ops->open(tty);
-                tty_unlock();
                 return ret;
         }
         return 0;