diff --git a/sys/kern/kern_exit.c b/sys/kern/kern_exit.c
--- a/sys/kern/kern_exit.c
+++ b/sys/kern/kern_exit.c
@@ -251,6 +251,8 @@
 	 * MUST abort all other threads before proceeding past here.
 	 */
 	PROC_LOCK(p);
+	p->p_flag2 |= P2_WEXIT;
+
 	/*
 	 * First check if some other thread or external request got
 	 * here before us.  If so, act appropriately: exit or suspend.
diff --git a/sys/kern/kern_proc.c b/sys/kern/kern_proc.c
--- a/sys/kern/kern_proc.c
+++ b/sys/kern/kern_proc.c
@@ -3446,7 +3446,7 @@
 			PROC_UNLOCK(p);
 			continue;
 		}
-		if ((p->p_flag & P_WEXIT) != 0) {
+		if ((p->p_flag2 & P2_WEXIT) != 0) {
 			seen_exiting = true;
 			PROC_UNLOCK(p);
 			continue;
diff --git a/sys/kern/kern_procctl.c b/sys/kern/kern_procctl.c
--- a/sys/kern/kern_procctl.c
+++ b/sys/kern/kern_procctl.c
@@ -325,7 +325,7 @@
 
 	res = true;
 	PROC_LOCK(p2);
-	if ((p2->p_flag & P_WEXIT) == 0) {
+	if ((p2->p_flag2 & P2_WEXIT) == 0) {
 		_PHOLD_LITE(p2);
 		res = reap_kill_proc_locked(td, p2, ksi, rk, error);
 		_PRELE(p2);
diff --git a/sys/kern/kern_sig.c b/sys/kern/kern_sig.c
--- a/sys/kern/kern_sig.c
+++ b/sys/kern/kern_sig.c
@@ -3406,6 +3406,7 @@
 	struct proc *p = td->td_proc;
 
 	PROC_LOCK_ASSERT(p, MA_OWNED);
+	p->p_flag2 |= P2_WEXIT;
 	p->p_acflag |= AXSIG;
 	/*
 	 * We must be single-threading to generate a core dump.  This
diff --git a/sys/sys/proc.h b/sys/sys/proc.h
--- a/sys/sys/proc.h
+++ b/sys/sys/proc.h
@@ -847,6 +847,9 @@
 #define	P2_NO_NEW_PRIVS		0x00008000	/* Ignore setuid */
 #define	P2_WXORX_DISABLE	0x00010000	/* WX mappings enabled */
 #define	P2_WXORX_ENABLE_EXEC	0x00020000	/* WXORX enabled after exec */
+#define	P2_WEXIT		0x00040000	/* exit just started, no
+						   external thread_single() is
+						   permitted */
 
 /* Flags protected by proctree_lock, kept in p_treeflags. */
 #define	P_TREE_ORPHANED		0x00000001	/* Reparented, on orphan list */