[PATCH 07/11] tty: vt: replace BUG_ON() by WARN_ON_ONCE()

["Jiri Slaby (SUSE)" <jirislaby@kernel.org>]

No need to panic in vc_uniscr_copy_line(), just warn. This should never
happen though, as vc_uniscr_check() is supposed to be called before
vc_uniscr_copy_line(). And the former checks vc->vc_uni_lines already.

In any case, use _ONCE as vc_uniscr_copy_line() is called repeatedly for
each line. So don't flood the logs, just in case.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
---
 drivers/tty/vt/vt.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index 119b3eafef59..db72375141b0 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -535,7 +535,8 @@ void vc_uniscr_copy_line(const struct vc_data *vc, void *dest, bool viewed,
 	int offset = row * vc->vc_size_row + col * 2;
 	unsigned long pos;
 
-	BUG_ON(!uni_lines);
+	if (WARN_ON_ONCE(!uni_lines))
+		return;
 
 	pos = (unsigned long)screenpos(vc, offset, viewed);
 	if (pos >= vc->vc_origin && pos < vc->vc_scr_end) {
-- 
2.39.0