summaryrefslogtreecommitdiff
path: root/drivers/tty
diff options
context:
space:
mode:
authorPeter Hurley <peter@hurleysoftware.com>2013-06-15 17:14:31 +0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-07-24 03:43:02 +0400
commitd8c1f929aa8164cd8eaa830068d2fa3159c0764a (patch)
tree1371cfe90fffdcb7115b39c77e0f729c109efc69 /drivers/tty
parentfb7aa03db605e4f0b9a62cd4c77177c2596edd95 (diff)
downloadlinux-d8c1f929aa8164cd8eaa830068d2fa3159c0764a.tar.xz
tty: Only guarantee termios read safety for throttle/unthrottle
No tty driver modifies termios during throttle() or unthrottle(). Therefore, only read safety is required. However, tty_throttle_safe and tty_unthrottle_safe must still be mutually exclusive; introduce throttle_mutex for that purpose. Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty')
-rw-r--r--drivers/tty/n_tty.c4
-rw-r--r--drivers/tty/tty_io.c1
-rw-r--r--drivers/tty/tty_ioctl.c8
3 files changed, 5 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;
}