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vt: Perform safe console erase only once 

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 are called twice
on the whole screen buffer. Let's reorganize the code so the same work
is not performed twice needlessly.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Nicolas Pitre 2018-05-14 11:53:04 -04:00 committed by Greg Kroah-Hartman
parent 339c7a8757
commit 4b4ecd9cb8
1 changed files with 7 additions and 9 deletions
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16
drivers/tty/vt/vt.c
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@ -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;
}