2 files changed, 8 insertions, 1 deletions

diff --git a/include/linux/tty.h b/include/linux/tty.h
index 4cfd4a82fc31..fd4148d3a261 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -252,6 +252,7 @@ struct tty_struct {
         struct rw_semaphore termios_rwsem;
         struct mutex winsize_mutex;
         spinlock_t ctrl_lock;
+        spinlock_t flow_lock;
         /* Termios values are protected by the termios rwsem */
         struct ktermios termios, termios_locked;
         struct termiox *termiox;        /* May be NULL for unsupported */
@@ -261,7 +262,7 @@ struct tty_struct {
         unsigned long flags;
         int count;
         struct winsize winsize;         /* winsize_mutex */
-        int stopped;
+        int stopped;                    /* flow_lock */
         int flow_stopped;
         int hw_stopped;
         int packet;
@@ -400,7 +401,9 @@ extern int tty_paranoia_check(struct tty_struct *tty, struct inode *inode,
 extern char *tty_name(struct tty_struct *tty, char *buf);
 extern void tty_wait_until_sent(struct tty_struct *tty, long timeout);
 extern int tty_check_change(struct tty_struct *tty);
+extern void __stop_tty(struct tty_struct *tty);
 extern void stop_tty(struct tty_struct *tty);
+extern void __start_tty(struct tty_struct *tty);
 extern void start_tty(struct tty_struct *tty);
 extern int tty_register_driver(struct tty_driver *driver);
 extern int tty_unregister_driver(struct tty_driver *driver);
diff --git a/include/linux/tty_driver.h b/include/linux/tty_driver.h
index e48c608a8fa8..92e337c18839 100644
--- a/include/linux/tty_driver.h
+++ b/include/linux/tty_driver.h
@@ -152,6 +152,8 @@
  *      This routine notifies the tty driver that it should stop
  *      outputting characters to the tty device.  
  *
+ *      Called with ->flow_lock held. Serialized with start() method.
+ *
  *      Optional:
  *
  *      Note: Call stop_tty not this method.
@@ -161,6 +163,8 @@
  *      This routine notifies the tty driver that it resume sending
  *      characters to the tty device.
  *
+ *      Called with ->flow_lock held. Serialized with stop() method.
+ *
  *      Optional:
  *
  *      Note: Call start_tty not this method.