git: c39bfe47139b - stable/13 - vt: call driver's postswitch when panicking on ttyv0

[Toomas Soome]

The branch stable/13 has been updated by tsoome:

URL: https://cgit.FreeBSD.org/src/commit/?id=c39bfe47139bac99e5519c22ccde42b2660b6500

commit c39bfe47139bac99e5519c22ccde42b2660b6500
Author:     Greg V <greg at unrelenting.technology>
AuthorDate: 2021-04-24 11:53:34 +0000
Commit:     Toomas Soome <tsoome at FreeBSD.org>
CommitDate: 2021-10-03 21:46:49 +0000

    vt: call driver's postswitch when panicking on ttyv0
    
    In vt_kms, the postswitch callback restores fbdev mode when
    panicking or entering the debugger. This ensures that even when
    a graphical applicatino was running on the first tty, simple framebuffer
    mode would be restored and the panic would be visible instead
    of the frozen GUI. But vt wouldn't call the postswitch callback
    when we're already on the first tty, so running a GUI on it
    would prevent you from reading any panics.
    
    Reviewed by:    tsoome
    Differential Revision: https://reviews.freebsd.org/D29961
    
    (cherry picked from commit c937a405bdce2fd12c534446a8cc9e5548dd27eb)
---
 sys/dev/vt/vt_core.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/sys/dev/vt/vt_core.c b/sys/dev/vt/vt_core.c
index d4baa65f06c9..884050f4f0c5 100644
--- a/sys/dev/vt/vt_core.c
+++ b/sys/dev/vt/vt_core.c
@@ -595,7 +595,13 @@ vt_window_switch(struct vt_window *vw)
 
 	VT_LOCK(vd);
 	if (curvw == vw) {
-		/* Nothing to do. */
+		/*
+		 * Nothing to do, except ensure the driver has the opportunity to
+		 * switch to console mode when panicking, making sure the panic
+		 * is readable (even when a GUI was using ttyv0).
+		 */
+		if ((kdb_active || panicstr) && vd->vd_driver->vd_postswitch)
+			vd->vd_driver->vd_postswitch(vd);
 		VT_UNLOCK(vd);
 		return (0);
 	}