vt/console: try harder to print output when panicing

Jesse's initial patch commit said:

"At panic time (i.e.  when oops_in_progress is set) we should try a bit
harder to update the screen and make sure output gets to the VT, since
some drivers are capable of flipping back to it.

So make sure we try to unblank and update the display if called from a
panic context."

I've enhanced this to add a flag to the vc that console layer can set to
indicate they want this behaviour to occur.  This also adds support to
fbcon for that flag and adds an fb flag for drivers to indicate they want
to use the support.  It enables this for KMS drivers.

Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Acked-by: James Simmons <jsimmons@infradead.org>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 9 insertions, 4 deletions

diff --git a/drivers/char/vt.c b/drivers/char/vt.c
index 34bfb056d7a6..82f64ac21191 100644
--- a/drivers/char/vt.c
+++ b/drivers/char/vt.c
@@ -705,7 +705,10 @@ void redraw_screen(struct vc_data *vc, int is_switch)
                         update_attr(vc);
                         clear_buffer_attributes(vc);
                 }
-                if (update && vc->vc_mode != KD_GRAPHICS)
+
+                /* Forcibly update if we're panicing */
+                if ((update && vc->vc_mode != KD_GRAPHICS) ||
+                    vt_force_oops_output(vc))
                         do_update_region(vc, vc->vc_origin, vc->vc_screenbuf_size / 2);
         }
         set_cursor(vc);
@@ -743,6 +746,7 @@ static void visual_init(struct vc_data *vc, int num, int init)
         vc->vc_hi_font_mask = 0;
         vc->vc_complement_mask = 0;
         vc->vc_can_do_color = 0;
+        vc->vc_panic_force_write = false;
         vc->vc_sw->con_init(vc, init);
         if (!vc->vc_complement_mask)
                 vc->vc_complement_mask = vc->vc_can_do_color ? 0x7700 : 0x0800;
@@ -2506,7 +2510,7 @@ static void vt_console_print(struct console *co, const char *b, unsigned count)
                 goto quit;
         }
 
-        if (vc->vc_mode != KD_TEXT)
+        if (vc->vc_mode != KD_TEXT && !vt_force_oops_output(vc))
                 goto quit;
 
         /* undraw cursor first */
@@ -3784,7 +3788,8 @@ void do_unblank_screen(int leaving_gfx)
                 return;
         }
         vc = vc_cons[fg_console].d;
-        if (vc->vc_mode != KD_TEXT)
+        /* Try to unblank in oops case too */
+        if (vc->vc_mode != KD_TEXT && !vt_force_oops_output(vc))
                 return; /* but leave console_blanked != 0 */
 
         if (blankinterval) {
@@ -3793,7 +3798,7 @@ void do_unblank_screen(int leaving_gfx)
         }
 
         console_blanked = 0;
-        if (vc->vc_sw->con_blank(vc, 0, leaving_gfx))
+        if (vc->vc_sw->con_blank(vc, 0, leaving_gfx) || vt_force_oops_output(vc))
                 /* Low-level driver cannot restore -> do it ourselves */
                 update_screen(vc);
         if (console_blank_hook)