3 files changed, 16 insertions, 7 deletions
diff --git a/arch/um/drivers/chan_kern.c b/arch/um/drivers/chan_kern.c
index c09dbdfa298..db3082b4da4 100644
--- a/arch/um/drivers/chan_kern.c
+++ b/arch/um/drivers/chan_kern.c
@@ -291,6 +291,9 @@ int write_chan(struct list_head *chans, const char *buf, int len,
 	struct chan *chan = NULL;
 	int n, ret = 0;
 
+	if (len == 0)
+		return 0;
+
 	list_for_each(ele, chans) {
 		chan = list_entry(ele, struct chan, list);
 		if (!chan->output || (chan->ops->write == NULL))
diff --git a/arch/um/drivers/chan_user.c b/arch/um/drivers/chan_user.c
index 77557e233f5..d29e56d8ced 100644
--- a/arch/um/drivers/chan_user.c
+++ b/arch/um/drivers/chan_user.c
@@ -38,7 +38,16 @@ int generic_read(int fd, char *c_out, void *unused)
 
 int generic_write(int fd, const char *buf, int n, void *unused)
 {
-	return write(fd, buf, n);
+	int err;
+
+	err = write(fd, buf, n);
+	if (err > 0)
+		return err;
+	else if (errno == EAGAIN)
+		return 0;
+	else if (err == 0)
+		return -EIO;
+	return -errno;
 }
 
 int generic_window_size(int fd, void *unused, unsigned short *rows_out,
diff --git a/arch/um/drivers/line.c b/arch/um/drivers/line.c
index 3e0b68e297f..b4538dfb482 100644
--- a/arch/um/drivers/line.c
+++ b/arch/um/drivers/line.c
@@ -216,18 +216,15 @@ int line_write(struct tty_struct *tty, const unsigned char *buf, int len)
 {
 	struct line *line = tty->driver_data;
 	unsigned long flags;
-	int n, err, ret = 0;
+	int n, ret = 0;
 
 	if(tty->stopped)
 		return 0;
 
 	spin_lock_irqsave(&line->lock, flags);
-	if (line->head != line->tail) {
+	if (line->head != line->tail)
 		ret = buffer_data(line, buf, len);
-		err = flush_buffer(line);
-		if (err <= 0 && (err != -EAGAIN || !ret))
-			ret = err;
-	} else {
+	else {
 		n = write_chan(&line->chan_list, buf, len,
 			       line->driver->write_irq);
 		if (n < 0) {