import PULS_20160108

[GitHub/mt8127/android_kernel_alcatel_ttab.git] / drivers / tty / n_tty.c

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index 6cfe4019abc63b3f3321df606e57bdd38ed6be72..ee59998437af8c703431f860b5b81b092751cdb3 100644 (file)
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -114,13 +114,14 @@ static inline int tty_put_user(struct tty_struct *tty, unsigned char x,
 }
 
 /**
- *     n_tty_set__room -       receive space
+ *     n_tty_set_room  -       receive space
  *     @tty: terminal
  *
- *     Called by the driver to find out how much data it is
- *     permitted to feed to the line discipline without any being lost
- *     and thus to manage flow control. Not serialized. Answers for the
- *     "instant".
+ *     Sets tty->receive_room to reflect the currently available space
+ *     in the input buffer, and re-schedules the flip buffer work if space
+ *     just became available.
+ *
+ *     Locks: Concurrent update is protected with read_lock
  */
 
 static void n_tty_set_room(struct tty_struct *tty)
@@ -128,8 +129,10 @@ static void n_tty_set_room(struct tty_struct *tty)
        struct n_tty_data *ldata = tty->disc_data;
        int left;
        int old_left;
+       unsigned long flags;
+
+       raw_spin_lock_irqsave(&ldata->read_lock, flags);
 
-       /* ldata->read_cnt is not read locked ? */
        if (I_PARMRK(tty)) {
                /* Multiply read_cnt by 3, since each byte might take up to
                 * three times as many spaces when PARMRK is set (depending on
@@ -149,6 +152,8 @@ static void n_tty_set_room(struct tty_struct *tty)
        old_left = tty->receive_room;
        tty->receive_room = left;
 
+       raw_spin_unlock_irqrestore(&ldata->read_lock, flags);
+
        /* Did this open up the receive buffer? We may need to flip */
        if (left && !old_left) {
                WARN_RATELIMIT(tty->port->itty == NULL,
@@ -1881,7 +1886,6 @@ do_it_again:
                                retval = -ERESTARTSYS;
                                break;
                        }
-                       /* FIXME: does n_tty_set_room need locking ? */
                        n_tty_set_room(tty);
                        timeout = schedule_timeout(timeout);
                        continue;