tty: hvc: hvc_write() fix break condition

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.

Tested-by: Matteo Croce <mcroce@redhat.com>
Tested-by: Jason Gunthorpe <jgg@mellanox.com>
Tested-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/hvc/hvc_console.c b/drivers/tty/hvc/hvc_console.c
index bacf9b7..27284a2 100644 (file)
--- 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 = 0;
+
                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);