diff --git a/arch/sparc/mm/io-unit.c b/arch/sparc/mm/io-unit.c
index 42c1c700c0a70b3c7ca86a13c90b22bf0e84fb5f..2bb1309003dd9e6ba316fdf87df308f2bceb34b5 100644
--- a/arch/sparc/mm/io-unit.c
+++ b/arch/sparc/mm/io-unit.c
@@ -64,6 +64,7 @@ iounit_init(int sbi_node, int io_node, struct sbus_bus *sbus)
 	
 	sbus->iommu = (struct iommu_struct *)iounit;
 	iounit->page_table = xpt;
+	spin_lock_init(&iounit->lock);
 	
 	for (xptend = iounit->page_table + (16 * PAGE_SIZE) / sizeof(iopte_t);
 	     xpt < xptend;)