Messages in this thread Patch in this message | | | From | Lukas Wunner <> | Date | Wed, 22 Jan 2020 15:17:30 +0100 | Subject | [PATCH] vt: Fix non-blinking cursor regression |
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Since commit a6dbe4427559 ("vt: perform safe console erase in the right order"), when userspace clears both the scrollback buffer and the screen by writing "\e[3J" to an fbdev virtual console, the cursor stops blinking if that virtual console is not in the foreground. I'm witnessing this on every boot of Raspbian since updating to v4.19.37+ because agetty writes the sequence to /dev/tty6 while the console is still switched to /dev/tty1. Switching consoles once makes the cursor blink again.
The commit added an invocation of ->con_switch() to flush_scrollback(). Normally this is only invoked from switch_screen() to switch consoles. switch_screen() updates *vc->vc_display_fg to the new console and fbcon_switch() updates ops->currcon. Because the commit only invokes fbcon_switch() but doesn't update *vc->vc_display_fg, it performs an incomplete console switch.
When fb_flashcursor() subsequently blinks the cursor, it retrieves the foreground console from ops->currcon. Because *vc->vc_display_fg wasn't updated, con_is_visible() incorrectly returns false and as a result, fb_flashcursor() bails out without blinking the cursor.
The invocation of ->con_switch() appears to have been erroneous. After all, why should a console switch be performed when clearing the screen? The commit message doesn't provide a rationale either. So delete it.
Fixes: a6dbe4427559 ("vt: perform safe console erase in the right order") Signed-off-by: Lukas Wunner <lukas@wunner.de> Cc: stable@vger.kernel.org # v5.1+ Cc: Nicolas Pitre <nico@fluxnic.net> Cc: Mikulas Patocka <mpatocka@redhat.com> Cc: Matthew Whitehead <tedheadster@gmail.com> --- drivers/tty/vt/vt.c | 2 -- 1 file changed, 2 deletions(-)
diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c index 35d21cdb60d0..eb25fb4ca05f 100644 --- a/drivers/tty/vt/vt.c +++ b/drivers/tty/vt/vt.c @@ -938,8 +938,6 @@ static void flush_scrollback(struct vc_data *vc) set_origin(vc); if (vc->vc_sw->con_flush_scrollback) vc->vc_sw->con_flush_scrollback(vc); - else - vc->vc_sw->con_switch(vc); } /* -- 2.24.0
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