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vt(4): Skip vt_flush() for nested panics

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[Why]
If there is a problem with DRM drivers or in their integration with
vt(4) and displaying something on the console triggers a panic, there is
a high chance that displaying that panic will trigger another one,
recursively.

[How]
If vt_flush() is called and it detects is is called resursively from
another panic, it return immediately, doing nothing, to avoid the risk
of triggering another panic.

Reviewed by:	manu
Approved by:	manu
Differential Revision:  https://reviews.freebsd.org/D42056

(cherry picked from commit 049e3fba04e82f840cc43080edade0ed415fee72)
This commit is contained in:
Jean-Sébastien Pédron 2023-11-24 18:30:33 +01:00 committed by Vladimir Kondratyev
parent bb01efa6f8
commit 608b148760
1 changed files with 15 additions and 0 deletions
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15
sys/dev/vt/vt_core.c
View file

@ -274,6 +274,8 @@ SYSINIT(vt_update_static, SI_SUB_KMEM, SI_ORDER_ANY, vt_update_static,
SYSINIT(vt_early_cons, SI_SUB_INT_CONFIG_HOOKS, SI_ORDER_ANY, vt_upgrade,
&vt_consdev);
static bool inside_vt_flush = false;
/* Initialize locks/mem depended members. */
static void
vt_update_static(void *dummy)
@ -1344,6 +1346,9 @@ vt_flush(struct vt_device *vd)
int cursor_was_shown, cursor_moved;
#endif
if (inside_vt_flush && KERNEL_PANICKED())
return (0);
vw = vd->vd_curwindow;
if (vw == NULL)
return (0);
@ -1357,6 +1362,8 @@ vt_flush(struct vt_device *vd)
vtbuf_lock(&vw->vw_buf);
inside_vt_flush = true;
#ifndef SC_NO_CUTPASTE
cursor_was_shown = vd->vd_mshown;
cursor_moved = (vd->vd_mx != vd->vd_mx_drawn ||
@ -1414,10 +1421,12 @@ vt_flush(struct vt_device *vd)
if (tarea.tr_begin.tp_col < tarea.tr_end.tp_col) {
vd->vd_driver->vd_bitblt_text(vd, vw, &tarea);
inside_vt_flush = false;
vtbuf_unlock(&vw->vw_buf);
return (1);
}
inside_vt_flush = false;
vtbuf_unlock(&vw->vw_buf);
return (0);
}
@ -1444,6 +1453,9 @@ vtterm_pre_input(struct terminal *tm)
{
struct vt_window *vw = tm->tm_softc;
if (inside_vt_flush && KERNEL_PANICKED())
return;
vtbuf_lock(&vw->vw_buf);
}
@ -1452,6 +1464,9 @@ vtterm_post_input(struct terminal *tm)
{
struct vt_window *vw = tm->tm_softc;
if (inside_vt_flush && KERNEL_PANICKED())
return;
vtbuf_unlock(&vw->vw_buf);
vt_resume_flush_timer(vw, 0);
}