lock_spin
struct mtx lock_spin;
mtx_init(&r->lock_spin, lock_name, NULL, MTX_SPIN);
mtx_lock_spin(&r->lock_spin);
mtx_unlock_spin(&r->lock_spin);
mtx_lock_spin(&r->lock_spin);
mtx_unlock_spin(&r->lock_spin);
mtx_lock_spin(&r->lock_spin);
mtx_unlock_spin(&r->lock_spin);
mtx_lock_spin(&r->lock_spin);
mtx_unlock_spin(&r->lock_spin);
static void lock_spin(struct lock_object *lock, uintptr_t how);
.lc_lock = lock_spin,