@@ -612,7 +612,7 @@ static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
}
/* no data */
- if (file->f_flags & O_NONBLOCK) {
+ if (tty_io_nonblock(tty, file)) {
ret = -EAGAIN;
break;
}
@@ -679,7 +679,7 @@ static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
if (tbuf)
break;
- if (file->f_flags & O_NONBLOCK) {
+ if (tty_io_nonblock(tty, file)) {
error = -EAGAIN;
break;
}
@@ -1078,7 +1078,7 @@ static ssize_t r3964_read(struct tty_struct *tty, struct file *file,
pMsg = remove_msg(pInfo, pClient);
if (pMsg == NULL) {
/* no messages available. */
- if (file->f_flags & O_NONBLOCK) {
+ if (tty_io_nonblock(tty, file)) {
ret = -EAGAIN;
goto unlock;
}
@@ -1671,7 +1671,7 @@ n_tty_receive_buf_common(struct tty_struct *tty, const unsigned char *cp,
down_read(&tty->termios_rwsem);
- while (1) {
+ do {
/*
* When PARMRK is set, each input char may take up to 3 chars
* in the read buf; reduce the buffer space avail by 3x
@@ -1713,7 +1713,7 @@ n_tty_receive_buf_common(struct tty_struct *tty, const unsigned char *cp,
fp += n;
count -= n;
rcvd += n;
- }
+ } while (!test_bit(TTY_LDISC_CHANGING, &tty->flags));
tty->receive_room = room;
@@ -2188,7 +2188,7 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
break;
if (!timeout)
break;
- if (file->f_flags & O_NONBLOCK) {
+ if (tty_io_nonblock(tty, file)) {
retval = -EAGAIN;
break;
}
@@ -2342,7 +2342,7 @@ static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
}
if (!nr)
break;
- if (file->f_flags & O_NONBLOCK) {
+ if (tty_io_nonblock(tty, file)) {
retval = -EAGAIN;
break;
}
@@ -340,6 +340,11 @@ int tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout)
{
int ret;
+ /* Kindly asking blocked readers to release the read side */
+ set_bit(TTY_LDISC_CHANGING, &tty->flags);
+ wake_up_interruptible_all(&tty->read_wait);
+ wake_up_interruptible_all(&tty->write_wait);
+
ret = __tty_ldisc_lock(tty, timeout);
if (!ret)
return -EBUSY;
@@ -350,6 +355,8 @@ int tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout)
void tty_ldisc_unlock(struct tty_struct *tty)
{
clear_bit(TTY_LDISC_HALTED, &tty->flags);
+ /* Can be cleared here - ldisc_unlock will wake up writers firstly */
+ clear_bit(TTY_LDISC_CHANGING, &tty->flags);
__tty_ldisc_unlock(tty);
}
@@ -365,6 +365,7 @@ struct tty_file_private {
#define TTY_NO_WRITE_SPLIT 17 /* Preserve write boundaries to driver */
#define TTY_HUPPED 18 /* Post driver->hangup() */
#define TTY_HUPPING 19 /* Hangup in progress */
+#define TTY_LDISC_CHANGING 20 /* Change pending - non-block IO */
#define TTY_LDISC_HALTED 22 /* Line discipline is halted */
/* Values for tty->flow_change */
@@ -382,6 +383,12 @@ static inline void tty_set_flow_change(struct tty_struct *tty, int val)
smp_mb();
}
+static inline bool tty_io_nonblock(struct tty_struct *tty, struct file *file)
+{
+ return file->f_flags & O_NONBLOCK ||
+ test_bit(TTY_LDISC_CHANGING, &tty->flags);
+}
+
static inline bool tty_io_error(struct tty_struct *tty)
{
return test_bit(TTY_IO_ERROR, &tty->flags);