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Subject[PATCH 1/5] vt: perform safe console erase only once
Date
Commit f8df13e0a9 ("tty: Clean console safely") added code to clear
both the scrollback buffer and the screen with "\e[3J", then execution
falls through into the code to simply clear the screen. This means
scr_memsetw() and the console driver update callback is called twice
on the whole screen buffer. Let's reorganize the code so the same work
is not performed twice.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
---
drivers/tty/vt/vt.c | 16 +++++++---------
1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index f97251f39c..1eb1a376a0 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -1178,15 +1178,8 @@ static void csi_J(struct vc_data *vc, int vpar)
count = ((vc->vc_pos - vc->vc_origin) >> 1) + 1;
start = (unsigned short *)vc->vc_origin;
break;
- case 3: /* erase scroll-back buffer (and whole display) */
- scr_memsetw(vc->vc_screenbuf, vc->vc_video_erase_char,
- vc->vc_screenbuf_size);
- flush_scrollback(vc);
- set_origin(vc);
- if (con_is_visible(vc))
- update_screen(vc);
- /* fall through */
case 2: /* erase whole display */
+ case 3: /* (and scrollback buffer later) */
count = vc->vc_cols * vc->vc_rows;
start = (unsigned short *)vc->vc_origin;
break;
@@ -1194,7 +1187,12 @@ static void csi_J(struct vc_data *vc, int vpar)
return;
}
scr_memsetw(start, vc->vc_video_erase_char, 2 * count);
- if (con_should_update(vc))
+ if (vpar == 3) {
+ set_origin(vc);
+ flush_scrollback(vc);
+ if (con_is_visible(vc))
+ update_screen(vc);
+ } else if (con_should_update(vc))
do_update_region(vc, (unsigned long) start, count);
vc->vc_need_wrap = 0;
}
--
2.17.0
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