s390/pgtable: make pgste lock an explicit barrier

Getting and Releasing the pgste lock has lock semantics. Make the
code an explicit barrier.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index f9a0a70..e8b6e5b 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -623,7 +623,7 @@
 		"	csg	%0,%1,%2\n"
 		"	jl	0b\n"
 		: "=&d" (old), "=&d" (new), "=Q" (ptep[PTRS_PER_PTE])
-		: "Q" (ptep[PTRS_PER_PTE]) : "cc");
+		: "Q" (ptep[PTRS_PER_PTE]) : "cc", "memory");
 #endif
 	return __pgste(new);
 }
@@ -635,7 +635,8 @@
 		"	nihh	%1,0xff7f\n"	/* clear RCP_PCL_BIT */
 		"	stg	%1,%0\n"
 		: "=Q" (ptep[PTRS_PER_PTE])
-		: "d" (pgste_val(pgste)), "Q" (ptep[PTRS_PER_PTE]) : "cc");
+		: "d" (pgste_val(pgste)), "Q" (ptep[PTRS_PER_PTE])
+		: "cc", "memory");
 	preempt_enable();
 #endif
 }