[PATCH -next v2 19/26] tty: Preset lock subclass for nested tty locks

Peter Hurley
2014-11-05T17:49:32Z

Eliminate the requirement of specifying the tty lock nesting at
lock time; instead, set the lock subclass for slave ptys at pty
install (normal ttys and master ptys use subclass 0).

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
---
drivers/tty/pty.c | 2 ++
drivers/tty/tty_mutex.c | 19 +++++++++----------
include/linux/tty.h | 1 +
3 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index bdb8fd1..11db7dc 100644
--- a/drivers/tty/pty.c
+++ b/drivers/tty/pty.c
@@ -399,6 +399,8 @@ static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
if (!o_tty)
goto err_put_module;

+ tty_set_lock_subclass(o_tty);
+
if (legacy) {
/* We always use new tty termios data so we can do this
the easy way .. */
diff --git a/drivers/tty/tty_mutex.c b/drivers/tty/tty_mutex.c
index f43e995..4486741 100644
--- a/drivers/tty/tty_mutex.c
+++ b/drivers/tty/tty_mutex.c
@@ -13,15 +13,14 @@

enum {
TTY_MUTEX_NORMAL,
- TTY_MUTEX_NESTED,
+ TTY_MUTEX_SLAVE,
};

/*
* Getting the big tty mutex.
*/

-static void __lockfunc tty_lock_nested(struct tty_struct *tty,
- unsigned int subclass)
+void __lockfunc tty_lock(struct tty_struct *tty)
{
if (tty->magic != TTY_MAGIC) {
pr_err("L Bad %p\n", tty);
@@ -29,12 +28,7 @@ static void __lockfunc tty_lock_nested(struct tty_struct *tty,
return;
}
tty_kref_get(tty);
- mutex_lock_nested(&tty->legacy_mutex, subclass);
-}
-
-void __lockfunc tty_lock(struct tty_struct *tty)
-{
- return tty_lock_nested(tty, TTY_MUTEX_NORMAL);
+ mutex_lock(&tty->legacy_mutex);
}
EXPORT_SYMBOL(tty_lock);

@@ -56,7 +50,7 @@ void __lockfunc tty_lock_slave(struct tty_struct *tty)
WARN_ON(!mutex_is_locked(&tty->link->legacy_mutex) ||
!tty->driver->type == TTY_DRIVER_TYPE_PTY ||
!tty->driver->type == PTY_TYPE_SLAVE);
- tty_lock_nested(tty, TTY_MUTEX_NESTED);
+ tty_lock(tty);
}
}

@@ -65,3 +59,8 @@ void __lockfunc tty_unlock_slave(struct tty_struct *tty)
if (tty && tty != tty->link)
tty_unlock(tty);
}
+
+void tty_set_lock_subclass(struct tty_struct *tty)
+{
+ lockdep_set_subclass(&tty->legacy_mutex, TTY_MUTEX_SLAVE);
+}
diff --git a/include/linux/tty.h b/include/linux/tty.h
index a07b4b4..196c352 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -640,6 +640,7 @@ extern void __lockfunc tty_lock(struct tty_struct *tty);
extern void __lockfunc tty_unlock(struct tty_struct *tty);
extern void __lockfunc tty_lock_slave(struct tty_struct *tty);
extern void __lockfunc tty_unlock_slave(struct tty_struct *tty);
+extern void tty_set_lock_subclass(struct tty_struct *tty);
/*
* this shall be called only from where BTM is held (like close)
*
--
2.1.3