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vt: restore tty when console is ungrabbed

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When a break-to-debugger is triggered, kdb will grab the console and vt(4)
will generally switch back to ttyv0. If one issues a continue from the
debugger, then kdb will ungrab the console and the system rolls on.

This change adds a perhaps minor feature: when we're down to grab == 0 and
if vt actually switched away to ttyv0, switch back to the tty it was
previously on before the console was grabbed.

The justification behind this is that a typical flow is to work in
!ttyv0 to avoid console spam while occasionally dropping to ddb to inspect
system state before returning. This could easily enough be tossed behind
a sysctl or something if it's not generally appreciated, but I anticipate
indifference.

Reviewed by:	ray
Differential Revision:	https://reviews.freebsd.org/D27110
This commit is contained in:
Kyle Evans 2020-12-31 10:50:43 -06:00
parent be46634337
commit c4a0333b55
2 changed files with 8 additions and 0 deletions
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1
sys/dev/vt/vt.h
View File

@ -124,6 +124,7 @@ struct vt_device {
struct vt_window *vd_windows[VT_MAXWINDOWS]; /* (c) Windows. */
struct vt_window *vd_curwindow; /* (d) Current window. */
struct vt_window *vd_savedwindow;/* (?) Saved for suspend. */
struct vt_window *vd_grabwindow; /* (?) Saved before cngrab. */
struct vt_pastebuf vd_pastebuf; /* (?) Copy/paste buf. */
const struct vt_driver *vd_driver; /* (c) Graphics driver. */
void *vd_softc; /* (u) Driver data. */

7
sys/dev/vt/vt_core.c
View File

@ -1805,6 +1805,9 @@ vtterm_cngrab(struct terminal *tm)
vw = tm->tm_softc;
vd = vw->vw_device;
/* To be restored after we ungrab. */
if (vd->vd_grabwindow == NULL)
vd->vd_grabwindow = vd->vd_curwindow;
if (!cold)
vt_window_switch(vw);
@ -1821,10 +1824,14 @@ vtterm_cnungrab(struct terminal *tm)
vw = tm->tm_softc;
vd = vw->vw_device;
MPASS(vd->vd_grabwindow != NULL);
if (vtterm_cnungrab_noswitch(vd, vw) != 0)
return;
if (!cold && vd->vd_grabwindow != vw)
vt_window_switch(vd->vd_grabwindow);
vd->vd_grabwindow = NULL;
}
static void