[PATCH 3/3] tty_lock: Localise the lock

From: Alan Cox
Date: Thu May 03 2012 - 17:08:52 EST

From: Alan Cox <alan@xxxxxxxxxxxxxxx>

In each remaining case the tty_lock is associated with a specific tty. This
means we can now lock on a per tty basis. We do need tty_lock_pair() for
the pty case. Uglier but still a step in the right direction.

Signed-off-by: Alan Cox <alan@xxxxxxxxxxxxxxx>
---

drivers/tty/amiserial.c | 12 ++++----
drivers/tty/cyclades.c | 2 +
drivers/tty/n_r3964.c | 11 ++++---
drivers/tty/pty.c | 23 +++++++++------
drivers/tty/synclink.c | 4 +--
drivers/tty/synclink_gt.c | 4 +--
drivers/tty/synclinkmp.c | 4 +--
drivers/tty/tty_io.c | 67 +++++++++++++++++++++++++++------------------
drivers/tty/tty_ldisc.c | 30 ++++++++++----------
drivers/tty/tty_mutex.c | 60 ++++++++++++++++++++++++++++++----------
drivers/tty/tty_port.c | 6 ++--
include/linux/tty.h | 23 +++++++++------
12 files changed, 149 insertions(+), 97 deletions(-)


diff --git a/drivers/tty/amiserial.c b/drivers/tty/amiserial.c
index 6cc4358..b88a65c 100644
--- a/drivers/tty/amiserial.c
+++ b/drivers/tty/amiserial.c
@@ -1033,7 +1033,7 @@ static int get_serial_info(struct tty_struct *tty, struct serial_state *state,
if (!retinfo)
return -EFAULT;
memset(&tmp, 0, sizeof(tmp));
- tty_lock();
+ tty_lock(tty);
tmp.line = tty->index;
tmp.port = state->port;
tmp.flags = state->tport.flags;
@@ -1042,7 +1042,7 @@ static int get_serial_info(struct tty_struct *tty, struct serial_state *state,
tmp.close_delay = state->tport.close_delay;
tmp.closing_wait = state->tport.closing_wait;
tmp.custom_divisor = state->custom_divisor;
- tty_unlock();
+ tty_unlock(tty);
if (copy_to_user(retinfo,&tmp,sizeof(*retinfo)))
return -EFAULT;
return 0;
@@ -1059,12 +1059,12 @@ static int set_serial_info(struct tty_struct *tty, struct serial_state *state,
if (copy_from_user(&new_serial,new_info,sizeof(new_serial)))
return -EFAULT;

- tty_lock();
+ tty_lock(tty);
change_spd = ((new_serial.flags ^ port->flags) & ASYNC_SPD_MASK) ||
new_serial.custom_divisor != state->custom_divisor;
if (new_serial.irq || new_serial.port != state->port ||
new_serial.xmit_fifo_size != state->xmit_fifo_size) {
- tty_unlock();
+ tty_unlock(tty);
return -EINVAL;
}

@@ -1084,7 +1084,7 @@ static int set_serial_info(struct tty_struct *tty, struct serial_state *state,
}

if (new_serial.baud_base < 9600) {
- tty_unlock();
+ tty_unlock(tty);
return -EINVAL;
}

@@ -1116,7 +1116,7 @@ check_and_exit:
}
} else
retval = startup(tty, state);
- tty_unlock();
+ tty_unlock(tty);
return retval;
}

diff --git a/drivers/tty/cyclades.c b/drivers/tty/cyclades.c
index e61cabd..6984e1a 100644
--- a/drivers/tty/cyclades.c
+++ b/drivers/tty/cyclades.c
@@ -1599,7 +1599,7 @@ static int cy_open(struct tty_struct *tty, struct file *filp)
* If the port is the middle of closing, bail out now
*/
if (tty_hung_up_p(filp) || (info->port.flags & ASYNC_CLOSING)) {
- wait_event_interruptible_tty(info->port.close_wait,
+ wait_event_interruptible_tty(tty, info->port.close_wait,
!(info->port.flags & ASYNC_CLOSING));
return (info->port.flags & ASYNC_HUP_NOTIFY) ? -EAGAIN: -ERESTARTSYS;
}
diff --git a/drivers/tty/n_r3964.c b/drivers/tty/n_r3964.c
index 5c6c314..656ad93 100644
--- a/drivers/tty/n_r3964.c
+++ b/drivers/tty/n_r3964.c
@@ -1065,7 +1065,8 @@ static ssize_t r3964_read(struct tty_struct *tty, struct file *file,

TRACE_L("read()");

- tty_lock();
+ /* FIXME: should use a private lock */
+ tty_lock(tty);

pClient = findClient(pInfo, task_pid(current));
if (pClient) {
@@ -1077,7 +1078,7 @@ static ssize_t r3964_read(struct tty_struct *tty, struct file *file,
goto unlock;
}
/* block until there is a message: */
- wait_event_interruptible_tty(pInfo->read_wait,
+ wait_event_interruptible_tty(tty, pInfo->read_wait,
(pMsg = remove_msg(pInfo, pClient)));
}

@@ -1107,7 +1108,7 @@ static ssize_t r3964_read(struct tty_struct *tty, struct file *file,
}
ret = -EPERM;
unlock:
- tty_unlock();
+ tty_unlock(tty);
return ret;
}

@@ -1156,7 +1157,7 @@ static ssize_t r3964_write(struct tty_struct *tty, struct file *file,
pHeader->locks = 0;
pHeader->owner = NULL;

- tty_lock();
+ tty_lock(tty);

pClient = findClient(pInfo, task_pid(current));
if (pClient) {
@@ -1175,7 +1176,7 @@ static ssize_t r3964_write(struct tty_struct *tty, struct file *file,
add_tx_queue(pInfo, pHeader);
trigger_transmit(pInfo);

- tty_unlock();
+ tty_unlock(tty);

return 0;
}
diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index 5505ffc..d6fa842 100644
--- a/drivers/tty/pty.c
+++ b/drivers/tty/pty.c
@@ -47,6 +47,7 @@ static void pty_close(struct tty_struct *tty, struct file *filp)
wake_up_interruptible(&tty->read_wait);
wake_up_interruptible(&tty->write_wait);
tty->packet = 0;
+ /* Review - krefs on tty_link ?? */
if (!tty->link)
return;
tty->link->packet = 0;
@@ -62,9 +63,7 @@ static void pty_close(struct tty_struct *tty, struct file *filp)
mutex_unlock(&devpts_mutex);
}
#endif
- tty_unlock();
tty_vhangup(tty->link);
- tty_lock();
}
}

@@ -622,26 +621,29 @@ static int ptmx_open(struct inode *inode, struct file *filp)
return retval;

/* find a device that is not in use. */
- tty_lock();
+ mutex_lock(&devpts_mutex);
index = devpts_new_index(inode);
- tty_unlock();
if (index < 0) {
retval = index;
goto err_file;
}

+ mutex_unlock(&devpts_mutex);
+
mutex_lock(&tty_mutex);
mutex_lock(&devpts_mutex);
tty = tty_init_dev(ptm_driver, index);
- mutex_unlock(&devpts_mutex);
- tty_lock();
- mutex_unlock(&tty_mutex);

if (IS_ERR(tty)) {
retval = PTR_ERR(tty);
goto out;
}

+ /* The tty returned here is locked so we can safely
+ drop the mutex */
+ mutex_unlock(&devpts_mutex);
+ mutex_unlock(&tty_mutex);
+
set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */

tty_add_file(tty, filp);
@@ -654,16 +656,17 @@ static int ptmx_open(struct inode *inode, struct file *filp)
if (retval)
goto err_release;

- tty_unlock();
+ tty_unlock(tty);
return 0;
err_release:
- tty_unlock();
+ tty_unlock(tty);
tty_release(inode, filp);
return retval;
out:
+ mutex_unlock(&tty_mutex);
devpts_kill_index(inode, index);
- tty_unlock();
err_file:
+ mutex_unlock(&devpts_mutex);
tty_free_file(filp);
return retval;
}
diff --git a/drivers/tty/synclink.c b/drivers/tty/synclink.c
index d063b7d..bc1ae4a 100644
--- a/drivers/tty/synclink.c
+++ b/drivers/tty/synclink.c
@@ -3338,9 +3338,9 @@ static int block_til_ready(struct tty_struct *tty, struct file * filp,
printk("%s(%d):block_til_ready blocking on %s count=%d\n",
__FILE__,__LINE__, tty->driver->name, port->count );

- tty_unlock();
+ tty_unlock(tty);
schedule();
- tty_lock();
+ tty_lock(tty);
}

set_current_state(TASK_RUNNING);
diff --git a/drivers/tty/synclink_gt.c b/drivers/tty/synclink_gt.c
index fcde827..df4f0dc 100644
--- a/drivers/tty/synclink_gt.c
+++ b/drivers/tty/synclink_gt.c
@@ -3337,9 +3337,9 @@ static int block_til_ready(struct tty_struct *tty, struct file *filp,
}

DBGINFO(("%s block_til_ready wait\n", tty->driver->name));
- tty_unlock();
+ tty_unlock(tty);
schedule();
- tty_lock();
+ tty_lock(tty);
}

set_current_state(TASK_RUNNING);
diff --git a/drivers/tty/synclinkmp.c b/drivers/tty/synclinkmp.c
index a040a46..845502f 100644
--- a/drivers/tty/synclinkmp.c
+++ b/drivers/tty/synclinkmp.c
@@ -3358,9 +3358,9 @@ static int block_til_ready(struct tty_struct *tty, struct file *filp,
printk("%s(%d):%s block_til_ready() count=%d\n",
__FILE__,__LINE__, tty->driver->name, port->count );

- tty_unlock();
+ tty_unlock(tty);
schedule();
- tty_lock();
+ tty_lock(tty);
}

set_current_state(TASK_RUNNING);
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index b425c79..9e930c0 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -185,6 +185,7 @@ void free_tty_struct(struct tty_struct *tty)
put_device(tty->dev);
kfree(tty->write_buf);
tty_buffer_free_all(tty);
+ tty->magic = 0xDEADDEAD;
kfree(tty);
}

@@ -573,7 +574,7 @@ void __tty_hangup(struct tty_struct *tty)
}
spin_unlock(&redirect_lock);

- tty_lock();
+ tty_lock(tty);

/* some functions below drop BTM, so we need this bit */
set_bit(TTY_HUPPING, &tty->flags);
@@ -666,7 +667,7 @@ void __tty_hangup(struct tty_struct *tty)
clear_bit(TTY_HUPPING, &tty->flags);
tty_ldisc_enable(tty);

- tty_unlock();
+ tty_unlock(tty);

if (f)
fput(f);
@@ -1103,12 +1104,12 @@ void tty_write_message(struct tty_struct *tty, char *msg)
{
if (tty) {
mutex_lock(&tty->atomic_write_lock);
- tty_lock();
+ tty_lock(tty);
if (tty->ops->write && !test_bit(TTY_CLOSING, &tty->flags)) {
- tty_unlock();
+ tty_unlock(tty);
tty->ops->write(tty, msg, strlen(msg));
} else
- tty_unlock();
+ tty_unlock(tty);
tty_write_unlock(tty);
}
return;
@@ -1403,6 +1404,7 @@ struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx)
}
initialize_tty_struct(tty, driver, idx);

+ tty_lock(tty);
retval = tty_driver_install_tty(driver, tty);
if (retval < 0)
goto err_deinit_tty;
@@ -1415,9 +1417,11 @@ struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx)
retval = tty_ldisc_setup(tty, tty->link);
if (retval)
goto err_release_tty;
+ /* Return the tty locked so that it cannot vanish under the caller */
return tty;

err_deinit_tty:
+ tty_unlock(tty);
deinitialize_tty_struct(tty);
free_tty_struct(tty);
err_module_put:
@@ -1426,6 +1430,7 @@ err_module_put:

/* call the tty release_tty routine to clean out this slot */
err_release_tty:
+ tty_unlock(tty);
printk_ratelimited(KERN_INFO "tty_init_dev: ldisc open failed, "
"clearing slot %d\n", idx);
release_tty(tty, idx);
@@ -1628,7 +1633,7 @@ int tty_release(struct inode *inode, struct file *filp)
if (tty_paranoia_check(tty, inode, __func__))
return 0;

- tty_lock();
+ tty_lock(tty);
check_tty_count(tty, __func__);

__tty_fasync(-1, filp, 0);
@@ -1637,10 +1642,11 @@ int tty_release(struct inode *inode, struct file *filp)
pty_master = (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
tty->driver->subtype == PTY_TYPE_MASTER);
devpts = (tty->driver->flags & TTY_DRIVER_DEVPTS_MEM) != 0;
+ /* Review: parallel close */
o_tty = tty->link;

if (tty_release_checks(tty, o_tty, idx)) {
- tty_unlock();
+ tty_unlock(tty);
return 0;
}

@@ -1652,7 +1658,7 @@ int tty_release(struct inode *inode, struct file *filp)
if (tty->ops->close)
tty->ops->close(tty, filp);

- tty_unlock();
+ tty_unlock(tty);
/*
* 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
@@ -1675,7 +1681,7 @@ int tty_release(struct inode *inode, struct file *filp)
opens on /dev/tty */

mutex_lock(&tty_mutex);
- tty_lock();
+ tty_lock_pair(tty, o_tty);
tty_closing = tty->count <= 1;
o_tty_closing = o_tty &&
(o_tty->count <= (pty_master ? 1 : 0));
@@ -1706,7 +1712,7 @@ int tty_release(struct inode *inode, struct file *filp)

printk(KERN_WARNING "%s: %s: read/write wait queue active!\n",
__func__, tty_name(tty, buf));
- tty_unlock();
+ tty_unlock_pair(tty, o_tty);
mutex_unlock(&tty_mutex);
schedule();
}
@@ -1769,7 +1775,7 @@ int tty_release(struct inode *inode, struct file *filp)

/* check whether both sides are closing ... */
if (!tty_closing || (o_tty && !o_tty_closing)) {
- tty_unlock();
+ tty_unlock_pair(tty, o_tty);
return 0;
}

@@ -1782,14 +1788,16 @@ int tty_release(struct inode *inode, struct file *filp)
tty_ldisc_release(tty, o_tty);
/*
* The release_tty function takes care of the details of clearing
- * the slots and preserving the termios structure.
+ * the slots and preserving the termios structure. The tty_unlock_pair
+ * should be safe as we keep a kref while the tty is locked (so the
+ * unlock never unlocks a freed tty).
*/
release_tty(tty, idx);
+ tty_unlock_pair(tty, o_tty);

/* Make this pty number available for reallocation */
if (devpts)
devpts_kill_index(inode, idx);
- tty_unlock();
return 0;
}

@@ -1893,6 +1901,9 @@ static struct tty_driver *tty_lookup_driver(dev_t device, struct file *filp,
* Locking: tty_mutex protects tty, tty_lookup_driver and tty_init_dev.
* tty->count should protect the rest.
* ->siglock protects ->signal/->sighand
+ *
+ * Note: the tty_unlock/lock cases without a ref are only safe due to
+ * tty_mutex
*/

static int tty_open(struct inode *inode, struct file *filp)
@@ -1916,8 +1927,7 @@ retry_open:
retval = 0;

mutex_lock(&tty_mutex);
- tty_lock();
-
+ /* This is protected by the tty_mutex */
tty = tty_open_current_tty(device, filp);
if (IS_ERR(tty)) {
retval = PTR_ERR(tty);
@@ -1938,17 +1948,19 @@ retry_open:
}

if (tty) {
+ tty_lock(tty);
retval = tty_reopen(tty);
- if (retval)
+ if (retval < 0) {
+ tty_unlock(tty);
tty = ERR_PTR(retval);
- } else
+ }
+ } else /* Returns with the tty_lock held for now */
tty = tty_init_dev(driver, index);

mutex_unlock(&tty_mutex);
if (driver)
tty_driver_kref_put(driver);
if (IS_ERR(tty)) {
- tty_unlock();
retval = PTR_ERR(tty);
goto err_file;
}
@@ -1977,7 +1989,7 @@ retry_open:
printk(KERN_DEBUG "%s: error %d in opening %s...\n", __func__,
retval, tty->name);
#endif
- tty_unlock(); /* need to call tty_release without BTM */
+ tty_unlock(tty); /* need to call tty_release without BTM */
tty_release(inode, filp);
if (retval != -ERESTARTSYS)
return retval;
@@ -1989,17 +2001,15 @@ retry_open:
/*
* Need to reset f_op in case a hangup happened.
*/
- tty_lock();
if (filp->f_op == &hung_up_tty_fops)
filp->f_op = &tty_fops;
- tty_unlock();
goto retry_open;
}
- tty_unlock();
+ tty_unlock(tty);


mutex_lock(&tty_mutex);
- tty_lock();
+ tty_lock(tty);
spin_lock_irq(&current->sighand->siglock);
if (!noctty &&
current->signal->leader &&
@@ -2007,11 +2017,10 @@ retry_open:
tty->session == NULL)
__proc_set_tty(current, tty);
spin_unlock_irq(&current->sighand->siglock);
- tty_unlock();
+ tty_unlock(tty);
mutex_unlock(&tty_mutex);
return 0;
err_unlock:
- tty_unlock();
mutex_unlock(&tty_mutex);
/* after locks to avoid deadlock */
if (!IS_ERR_OR_NULL(driver))
@@ -2094,10 +2103,13 @@ out:

static int tty_fasync(int fd, struct file *filp, int on)
{
+ struct tty_struct *tty = file_tty(filp);
int retval;
- tty_lock();
+
+ tty_lock(tty);
retval = __tty_fasync(fd, filp, on);
- tty_unlock();
+ tty_unlock(tty);
+
return retval;
}

@@ -2934,6 +2946,7 @@ void initialize_tty_struct(struct tty_struct *tty,
tty->pgrp = NULL;
tty->overrun_time = jiffies;
tty_buffer_init(tty);
+ mutex_init(&tty->legacy_mutex);
mutex_init(&tty->termios_mutex);
mutex_init(&tty->ldisc_mutex);
init_waitqueue_head(&tty->write_wait);
diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c
index 24b95db..fa65cde 100644
--- a/drivers/tty/tty_ldisc.c
+++ b/drivers/tty/tty_ldisc.c
@@ -567,7 +567,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
if (IS_ERR(new_ldisc))
return PTR_ERR(new_ldisc);

- tty_lock();
+ tty_lock(tty);
/*
* We need to look at the tty locking here for pty/tty pairs
* when both sides try to change in parallel.
@@ -581,12 +581,12 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
*/

if (tty->ldisc->ops->num == ldisc) {
- tty_unlock();
+ tty_unlock(tty);
tty_ldisc_put(new_ldisc);
return 0;
}

- tty_unlock();
+ tty_unlock(tty);
/*
* Problem: What do we do if this blocks ?
* We could deadlock here
@@ -594,7 +594,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)

tty_wait_until_sent(tty, 0);

- tty_lock();
+ tty_lock(tty);
mutex_lock(&tty->ldisc_mutex);

/*
@@ -604,10 +604,10 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)

while (test_bit(TTY_LDISC_CHANGING, &tty->flags)) {
mutex_unlock(&tty->ldisc_mutex);
- tty_unlock();
+ tty_unlock(tty);
wait_event(tty_ldisc_wait,
test_bit(TTY_LDISC_CHANGING, &tty->flags) == 0);
- tty_lock();
+ tty_lock(tty);
mutex_lock(&tty->ldisc_mutex);
}

@@ -622,7 +622,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)

o_ldisc = tty->ldisc;

- tty_unlock();
+ tty_unlock(tty);
/*
* Make sure we don't change while someone holds a
* reference to the line discipline. The TTY_LDISC bit
@@ -649,7 +649,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)

retval = tty_ldisc_wait_idle(tty, 5 * HZ);

- tty_lock();
+ tty_lock(tty);
mutex_lock(&tty->ldisc_mutex);

/* handle wait idle failure locked */
@@ -664,7 +664,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
clear_bit(TTY_LDISC_CHANGING, &tty->flags);
mutex_unlock(&tty->ldisc_mutex);
tty_ldisc_put(new_ldisc);
- tty_unlock();
+ tty_unlock(tty);
return -EIO;
}

@@ -707,7 +707,7 @@ enable:
if (o_work)
schedule_work(&o_tty->buf.work);
mutex_unlock(&tty->ldisc_mutex);
- tty_unlock();
+ tty_unlock(tty);
return retval;
}

@@ -815,11 +815,11 @@ void tty_ldisc_hangup(struct tty_struct *tty)
* need to wait for another function taking the BTM
*/
clear_bit(TTY_LDISC, &tty->flags);
- tty_unlock();
+ tty_unlock(tty);
cancel_work_sync(&tty->buf.work);
mutex_unlock(&tty->ldisc_mutex);
retry:
- tty_lock();
+ tty_lock(tty);
mutex_lock(&tty->ldisc_mutex);

/* At this point we have a closed ldisc and we want to
@@ -830,7 +830,7 @@ retry:
if (atomic_read(&tty->ldisc->users) != 1) {
char cur_n[TASK_COMM_LEN], tty_n[64];
long timeout = 3 * HZ;
- tty_unlock();
+ tty_unlock(tty);

while (tty_ldisc_wait_idle(tty, timeout) == -EBUSY) {
timeout = MAX_SCHEDULE_TIMEOUT;
@@ -911,10 +911,10 @@ void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty)
* race with the set_ldisc code path.
*/

- tty_unlock();
+ tty_unlock(tty);
tty_ldisc_halt(tty);
tty_ldisc_flush_works(tty);
- tty_lock();
+ tty_lock(tty);

mutex_lock(&tty->ldisc_mutex);
/*
diff --git a/drivers/tty/tty_mutex.c b/drivers/tty/tty_mutex.c
index 9ff986c..69adc80 100644
--- a/drivers/tty/tty_mutex.c
+++ b/drivers/tty/tty_mutex.c
@@ -4,29 +4,59 @@
#include <linux/semaphore.h>
#include <linux/sched.h>

-/*
- * The 'big tty mutex'
- *
- * This mutex is taken and released by tty_lock() and tty_unlock(),
- * replacing the older big kernel lock.
- * It can no longer be taken recursively, and does not get
- * released implicitly while sleeping.
- *
- * Don't use in new code.
- */
-static DEFINE_MUTEX(big_tty_mutex);
+/* Legacy tty mutex glue */

/*
* Getting the big tty mutex.
*/
-void __lockfunc tty_lock(void)
+
+void __lockfunc tty_lock(struct tty_struct *tty)
{
- mutex_lock(&big_tty_mutex);
+ if (tty->magic != TTY_MAGIC) {
+ printk(KERN_ERR "L Bad %p\n", tty);
+ WARN_ON(1);
+ return;
+ }
+ tty_kref_get(tty);
+ mutex_lock(&tty->legacy_mutex);
}
EXPORT_SYMBOL(tty_lock);

-void __lockfunc tty_unlock(void)
+void __lockfunc tty_unlock(struct tty_struct *tty)
{
- mutex_unlock(&big_tty_mutex);
+ if (tty->magic != TTY_MAGIC) {
+ printk(KERN_ERR "U Bad %p\n", tty);
+ WARN_ON(1);
+ return;
+ }
+ mutex_unlock(&tty->legacy_mutex);
+ tty_kref_put(tty);
}
EXPORT_SYMBOL(tty_unlock);
+
+/*
+ * Getting the big tty mutex for a pair of ttys with lock ordering
+ * On a non pty/tty pair tty2 can be NULL which is just fine.
+ */
+void __lockfunc tty_lock_pair(struct tty_struct *tty,
+ struct tty_struct *tty2)
+{
+ if (tty < tty2) {
+ tty_lock(tty);
+ tty_lock(tty2);
+ } else {
+ if (tty2 && tty2 != tty)
+ tty_lock(tty2);
+ tty_lock(tty);
+ }
+}
+EXPORT_SYMBOL(tty_lock_pair);
+
+void __lockfunc tty_unlock_pair(struct tty_struct *tty,
+ struct tty_struct *tty2)
+{
+ tty_unlock(tty);
+ if (tty2 && tty2 != tty)
+ tty_unlock(tty2);
+}
+EXPORT_SYMBOL(tty_unlock_pair);
diff --git a/drivers/tty/tty_port.c b/drivers/tty/tty_port.c
index d24807a..64f0975 100644
--- a/drivers/tty/tty_port.c
+++ b/drivers/tty/tty_port.c
@@ -237,7 +237,7 @@ int tty_port_block_til_ready(struct tty_port *port,

/* block if port is in the process of being closed */
if (tty_hung_up_p(filp) || port->flags & ASYNC_CLOSING) {
- wait_event_interruptible_tty(port->close_wait,
+ wait_event_interruptible_tty(tty, port->close_wait,
!(port->flags & ASYNC_CLOSING));
if (port->flags & ASYNC_HUP_NOTIFY)
return -EAGAIN;
@@ -303,9 +303,9 @@ int tty_port_block_til_ready(struct tty_port *port,
retval = -ERESTARTSYS;
break;
}
- tty_unlock();
+ tty_unlock(tty);
schedule();
- tty_lock();
+ tty_lock(tty);
}
finish_wait(&port->open_wait, &wait);

diff --git a/include/linux/tty.h b/include/linux/tty.h
index 9f47ab5..4990ef2 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -268,6 +268,7 @@ struct tty_struct {
struct mutex ldisc_mutex;
struct tty_ldisc *ldisc;

+ struct mutex legacy_mutex;
struct mutex termios_mutex;
spinlock_t ctrl_lock;
/* Termios values are protected by the termios mutex */
@@ -605,8 +606,12 @@ extern long vt_compat_ioctl(struct tty_struct *tty,

/* tty_mutex.c */
/* functions for preparation of BKL removal */
-extern void __lockfunc tty_lock(void) __acquires(tty_lock);
-extern void __lockfunc tty_unlock(void) __releases(tty_lock);
+extern void __lockfunc tty_lock(struct tty_struct *tty);
+extern void __lockfunc tty_unlock(struct tty_struct *tty);
+extern void __lockfunc tty_lock_pair(struct tty_struct *tty,
+ struct tty_struct *tty2);
+extern void __lockfunc tty_unlock_pair(struct tty_struct *tty,
+ struct tty_struct *tty2);

/*
* this shall be called only from where BTM is held (like close)
@@ -621,9 +626,9 @@ extern void __lockfunc tty_unlock(void) __releases(tty_lock);
static inline void tty_wait_until_sent_from_close(struct tty_struct *tty,
long timeout)
{
- tty_unlock(); /* tty->ops->close holds the BTM, drop it while waiting */
+ tty_unlock(tty); /* tty->ops->close holds the BTM, drop it while waiting */
tty_wait_until_sent(tty, timeout);
- tty_lock();
+ tty_lock(tty);
}

/*
@@ -638,16 +643,16 @@ static inline void tty_wait_until_sent_from_close(struct tty_struct *tty,
*
* Do not use in new code.
*/
-#define wait_event_interruptible_tty(wq, condition) \
+#define wait_event_interruptible_tty(tty, wq, condition) \
({ \
int __ret = 0; \
if (!(condition)) { \
- __wait_event_interruptible_tty(wq, condition, __ret); \
+ __wait_event_interruptible_tty(tty, wq, condition, __ret); \
} \
__ret; \
})

-#define __wait_event_interruptible_tty(wq, condition, ret) \
+#define __wait_event_interruptible_tty(tty, wq, condition, ret) \
do { \
DEFINE_WAIT(__wait); \
\
@@ -656,9 +661,9 @@ do { \
if (condition) \
break; \
if (!signal_pending(current)) { \
- tty_unlock(); \
+ tty_unlock(tty); \
schedule(); \
- tty_lock(); \
+ tty_lock(tty); \
continue; \
} \
ret = -ERESTARTSYS; \

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