diff --git a/sys/kern/kern_exit.c b/sys/kern/kern_exit.c
index 4ae24bcd7059..25b17ff07e66 100644
--- a/sys/kern/kern_exit.c
+++ b/sys/kern/kern_exit.c
@@ -819,6 +819,7 @@ proc_reap(struct thread *td, struct proc *p, int *status, int options)
 	PROC_LOCK_ASSERT(p, MA_OWNED);
 	KASSERT(p->p_state == PRS_ZOMBIE, ("proc_reap: !PRS_ZOMBIE"));
 
+	mtx_spin_wait_unlocked(&p->p_slock);
 	q = td->td_proc;
 
 	if (status)
diff --git a/sys/kern/kern_mutex.c b/sys/kern/kern_mutex.c
index c652eca064cc..6cf5a2b08b8c 100644
--- a/sys/kern/kern_mutex.c
+++ b/sys/kern/kern_mutex.c
@@ -1226,6 +1226,26 @@ _mtx_lock_indefinite_check(struct mtx *m, struct lock_delay_arg *ldap)
 	cpu_spinwait();
 }
 
+void
+mtx_spin_wait_unlocked(struct mtx *m)
+{
+	struct lock_delay_arg lda;
+
+	lda.spin_cnt = 0;
+	while (atomic_load_acq_ptr(&m->mtx_lock) != MTX_UNOWNED) {
+		if (__predict_true(lda.spin_cnt < 10000000)) {
+			cpu_spinwait();
+			lda.spin_cnt++;
+		} else {
+			_mtx_lock_indefinite_check(m, &lda);
+		}
+	}
+
+	if (lda.spin_cnt != 0) {
+		printf("%s: caught locked, spun for %d loops\n", __func__, lda.spin_cnt);
+	}
+}
+
 #ifdef DDB
 void
 db_show_mtx(const struct lock_object *lock)
diff --git a/sys/sys/mutex.h b/sys/sys/mutex.h
index 805df8adc40a..f9ce4e3bdca7 100644
--- a/sys/sys/mutex.h
+++ b/sys/sys/mutex.h
@@ -125,6 +125,8 @@ int	__mtx_trylock_spin_flags(volatile uintptr_t *c, int opts,
 	     const char *file, int line);
 void	__mtx_unlock_spin_flags(volatile uintptr_t *c, int opts,
 	    const char *file, int line);
+void	mtx_spin_wait_unlocked(struct mtx *m);
+
 #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
 void	__mtx_assert(const volatile uintptr_t *c, int what, const char *file,
 	    int line);