sparc64: Need to disable preemption around smp_tsb_sync().

Based upon a bug report by Mariusz Kozlowski

It uses smp_call_function_masked() now, which has a preemption-disabled
requirement.

Signed-off-by: David S. Miller <davem@davemloft.net>

arch/sparc64/mm/tsb.c

@@ -1,9 +1,10 @@
 /* arch/sparc64/mm/tsb.c
  *
- * Copyright (C) 2006 David S. Miller <davem@davemloft.net>
+ * Copyright (C) 2006, 2008 David S. Miller <davem@davemloft.net>
  */
 
 #include <linux/kernel.h>
+#include <linux/preempt.h>
 #include <asm/system.h>
 #include <asm/page.h>
 #include <asm/tlbflush.h>
@@ -415,7 +416,9 @@ retry_tsb_alloc:
 		tsb_context_switch(mm);
 
 		/* Now force other processors to do the same.  */
+		preempt_disable();
 		smp_tsb_sync(mm);
+		preempt_enable();
 
 		/* Now it is safe to free the old tsb.  */
 		kmem_cache_free(tsb_caches[old_cache_index], old_tsb);