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>
diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index 507441a..5ee9081 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -149,6 +149,7 @@
#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 @@
* 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 @@
}
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 @@
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 @@
*/
set_bit(TTY_HUPPED, &tty->flags);
tty_ldisc_enable(tty);
- unlock_kernel();
+ tty_unlock();
if (f)
fput(f);
}
@@ -696,7 +700,8 @@
* 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 @@
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 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 @@
* 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 @@
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;
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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
/* check whether both sides are closing ... */
if (!tty_closing || (o_tty && !o_tty_closing)) {
- unlock_kernel();
+ tty_unlock();
return 0;
}
@@ -1718,7 +1724,7 @@
/* Make this pty number available for reallocation */
if (devpts)
devpts_kill_index(inode, idx);
- unlock_kernel();
+ tty_unlock();
return 0;
}
@@ -1760,12 +1766,12 @@
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 @@
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 @@
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 @@
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 @@
#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 @@
*/
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(¤t->sighand->siglock);
if (!noctty &&
current->signal->leader &&
@@ -1890,7 +1896,7 @@
tty->session == NULL)
__proc_set_tty(current, tty);
spin_unlock_irq(¤t->sighand->siglock);
- unlock_kernel();
+ tty_unlock();
mutex_unlock(&tty_mutex);
return 0;
}
@@ -1926,13 +1932,12 @@
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 @@
}
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;
}