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@xxxxxxxxxxxxxxxxxx>
---
drivers/tty/n_tty.c | 4 ----
drivers/tty/tty_io.c | 1 +
drivers/tty/tty_ioctl.c | 8 ++++----
include/linux/tty.h | 1 +
4 files changed, 6 insertions(+), 8 deletions(-)
diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index d0c8805..b78ee464 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 1cec782..7dbea58 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -3013,6 +3013,7 @@ 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 9ce20df..03ba081 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 d304207..57a70d1 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 */
--
1.8.1.2
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