[PATCH 3/3] tty: hvc: hvc_write() fix break condition

[Nicholas Piggin]

Commit 550ddadcc758 ("tty: hvc: hvc_write() may sleep") broke the
termination condition in case the driver stops accepting characters.
This can result in unnecessary polling of the busy driver.

Restore it by testing the hvc_push return code.

Fixes: 550ddadcc758 ("tty: hvc: hvc_write() may sleep")
Tested-by: Matteo Croce <mcr...@redhat.com>
Tested-by: Leon Romanovsky <leo...@mellanox.com>
Signed-off-by: Nicholas Piggin <npig...@gmail.com>
---
 drivers/tty/hvc/hvc_console.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/hvc/hvc_console.c b/drivers/tty/hvc/hvc_console.c
index bacf9b73ec98..c09a38fb0d66 100644
--- a/drivers/tty/hvc/hvc_console.c
+++ b/drivers/tty/hvc/hvc_console.c
@@ -522,6 +522,8 @@ static int hvc_write(struct tty_struct *tty, const unsigned 
char *buf, int count
                return -EIO;
 
        while (count > 0) {
+               int ret;
+
                spin_lock_irqsave(&hp->lock, flags);
 
                rsize = hp->outbuf_size - hp->n_outbuf;
@@ -537,10 +539,13 @@ static int hvc_write(struct tty_struct *tty, const 
unsigned char *buf, int count
                }
 
                if (hp->n_outbuf > 0)
-                       hvc_push(hp);
+                       ret = hvc_push(hp);
 
                spin_unlock_irqrestore(&hp->lock, flags);
 
+               if (!ret)
+                       break;
+
                if (count) {
                        if (hp->n_outbuf > 0)
                                hvc_flush(hp);
-- 
2.18.0