diff -Nru linux-2.6.12/include/asm-ppc/mmu_context.h linux-2.6.12.new/include/asm-ppc/mmu_context.h
--- linux-2.6.12/include/asm-ppc/mmu_context.h	2005-06-17 15:48:29.000000000 -0400
+++ linux-2.6.12.new/include/asm-ppc/mmu_context.h	2005-07-05 08:58:46.000000000 -0400
@@ -149,6 +149,7 @@
  */
 static inline void destroy_context(struct mm_struct *mm)
 {
+	preempt_disable();
 	if (mm->context != NO_CONTEXT) {
 		clear_bit(mm->context, context_map);
 		mm->context = NO_CONTEXT;
@@ -156,6 +157,7 @@
 		atomic_inc(&nr_free_contexts);
 #endif
 	}
+	preempt_enable();
 }
 
 static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,