10.4/fix-syscons-write-locking-failure.diff

The syscons(4) write should acquire a per-phyical-device lock because some
data that a write operation will manipulating could be shared by many virtual
devices.
Based on revision 330832.

diff -ru --exclude-from freebsd-src-diff-exclude-names --new-file /var/archive3/public/freebsd-releng-10.4-src/sys/dev/syscons/syscons.c freebsd-10.4/sys/dev/syscons/syscons.c
--- /var/archive3/public/freebsd-releng-10.4-src/sys/dev/syscons/syscons.c	2017-09-29 08:19:54.000000000 +0800
+++ freebsd-10.4/sys/dev/syscons/syscons.c	2021-07-19 00:30:56.365556000 +0800
@@ -2689,13 +2689,13 @@
 #endif
 
     if (scp->tsw) {
-	if (!kdb_active && !mtx_owned(&scp->scr_lock)) {
+	if (!kdb_active && !mtx_owned(&scp->sc->write_mtx)) {
 		need_unlock = 1;
-		mtx_lock_spin(&scp->scr_lock);
+		mtx_lock_spin(&scp->sc->write_mtx);
 	}
 	(*scp->tsw->te_puts)(scp, buf, len, kernel);
 	if (need_unlock)
-		mtx_unlock_spin(&scp->scr_lock);
+		mtx_unlock_spin(&scp->sc->write_mtx);
     }
 
     if (scp->sc->delayed_next_scr)
@@ -2854,14 +2854,16 @@
 	sc_get_bios_values(&bios_value);
     init_done = WARM;
 
-    /*
-     * Allocate resources.  Even if we are being called for the second
-     * time, we must allocate them again, because they might have 
-     * disappeared...
-     */
-    sc = sc_get_softc(unit, flags & SC_KERNEL_CONSOLE);
-    if ((sc->flags & SC_INIT_DONE) == 0)
-	SC_VIDEO_LOCKINIT(sc);
+	/*
+	 * Allocate resources.  Even if we are being called for the second
+	 * time, we must allocate them again, because they might have 
+	 * disappeared...
+	 */
+	sc = sc_get_softc(unit, flags & SC_KERNEL_CONSOLE);
+	if ((sc->flags & SC_INIT_DONE) == 0) {
+		mtx_init(&sc->write_mtx, "syscons write lock", NULL, MTX_SPIN);
+		SC_VIDEO_LOCKINIT(sc);
+	}
 
     adp = NULL;
     if (sc->adapter >= 0) {
@@ -3078,7 +3080,8 @@
 	(*scp->tsw->te_term)(scp, &scp->ts);
     if (scp->ts != NULL)
 	free(scp->ts, M_DEVBUF);
-    mtx_destroy(&scp->scr_lock);
+    mtx_destroy(&sc->video_mtx);
+    mtx_destroy(&sc->write_mtx);
 
     /* clear the structure */
     if (!(flags & SC_KERNEL_CONSOLE)) {
@@ -3303,8 +3306,6 @@
     scp->history = NULL;
     scp->history_pos = 0;
     scp->history_size = 0;
-
-    mtx_init(&scp->scr_lock, "scrlock", NULL, MTX_SPIN);
 }
 
 int
diff -ru --exclude-from freebsd-src-diff-exclude-names --new-file /var/archive3/public/freebsd-releng-10.4-src/sys/dev/syscons/syscons.h freebsd-10.4/sys/dev/syscons/syscons.h
--- /var/archive3/public/freebsd-releng-10.4-src/sys/dev/syscons/syscons.h	2017-09-29 08:19:54.000000000 +0800
+++ freebsd-10.4/sys/dev/syscons/syscons.h	2021-07-19 00:27:15.543547000 +0800
@@ -231,6 +231,7 @@
 	char        	write_in_progress;
 	char        	blink_in_progress;
 	struct mtx	video_mtx;
+	struct mtx	write_mtx;		/* mutex for sc_puts() */
 
 	long		scrn_time_stamp;
 
@@ -344,7 +345,6 @@
 
 	int		splash_save_mode;	/* saved mode for splash screen */
 	int		splash_save_status;	/* saved status for splash screen */
-	struct mtx	scr_lock;		/* mutex for sc_puts() */
 #ifdef _SCR_MD_STAT_DECLARED_
 	scr_md_stat_t	md;			/* machine dependent vars */
 #endif