4 files changed, 6 insertions, 8 deletions

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index d0c8805d8131..b78ee464bd09 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -1518,9 +1518,7 @@ static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
                 tty_set_flow_change(tty, TTY_THROTTLE_SAFE);
                 if (receive_room(tty) >= TTY_THRESHOLD_THROTTLE)
                         break;
-                up_read(&tty->termios_rwsem);
                 throttled = tty_throttle_safe(tty);
-                down_read(&tty->termios_rwsem);
                 if (!throttled)
                         break;
         }
@@ -2086,9 +2084,7 @@ do_it_again:
                         if (!tty->count)
                                 break;
                         n_tty_set_room(tty);
-                        up_read(&tty->termios_rwsem);
                         unthrottled = tty_unthrottle_safe(tty);
-                        down_read(&tty->termios_rwsem);
                         if (!unthrottled)
                                 break;
                 }
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 639e24ade9bf..1b32da6f6cdd 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -3015,6 +3015,7 @@ void initialize_tty_struct(struct tty_struct *tty,
         tty->session = NULL;
         tty->pgrp = NULL;
         mutex_init(&tty->legacy_mutex);
+        mutex_init(&tty->throttle_mutex);
         init_rwsem(&tty->termios_rwsem);
         init_ldsem(&tty->ldisc_sem);
         init_waitqueue_head(&tty->write_wait);
diff --git a/drivers/tty/tty_ioctl.c b/drivers/tty/tty_ioctl.c
index 9ce20df8a2c8..03ba081c5772 100644
--- a/drivers/tty/tty_ioctl.c
+++ b/drivers/tty/tty_ioctl.c
@@ -151,7 +151,7 @@ int tty_throttle_safe(struct tty_struct *tty)
 {
         int ret = 0;
 
-        down_write(&tty->termios_rwsem);
+        mutex_lock(&tty->throttle_mutex);
         if (!test_bit(TTY_THROTTLED, &tty->flags)) {
                 if (tty->flow_change != TTY_THROTTLE_SAFE)
                         ret = 1;
@@ -161,7 +161,7 @@ int tty_throttle_safe(struct tty_struct *tty)
                                 tty->ops->throttle(tty);
                 }
         }
-        up_write(&tty->termios_rwsem);
+        mutex_unlock(&tty->throttle_mutex);
 
         return ret;
 }
@@ -182,7 +182,7 @@ int tty_unthrottle_safe(struct tty_struct *tty)
 {
         int ret = 0;
 
-        down_write(&tty->termios_rwsem);
+        mutex_lock(&tty->throttle_mutex);
         if (test_bit(TTY_THROTTLED, &tty->flags)) {
                 if (tty->flow_change != TTY_UNTHROTTLE_SAFE)
                         ret = 1;
@@ -192,7 +192,7 @@ int tty_unthrottle_safe(struct tty_struct *tty)
                                 tty->ops->unthrottle(tty);
                 }
         }
-        up_write(&tty->termios_rwsem);
+        mutex_unlock(&tty->throttle_mutex);
 
         return ret;
 }
diff --git a/include/linux/tty.h b/include/linux/tty.h
index d3042076d163..57a70d1d0412 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -244,6 +244,7 @@ struct tty_struct {
 
         struct mutex atomic_write_lock;
         struct mutex legacy_mutex;
+        struct mutex throttle_mutex;
         struct rw_semaphore termios_rwsem;
         spinlock_t ctrl_lock;
         /* Termios values are protected by the termios rwsem */