--- zzzz-none-000/linux-2.4.17/include/asm-ppc/mmu_context.h	2001-10-02 16:12:44.000000000 +0000
+++ sangam-fb-322/linux-2.4.17/include/asm-ppc/mmu_context.h	2004-11-24 13:21:50.000000000 +0000
@@ -158,6 +158,10 @@
 static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
 			     struct task_struct *tsk, int cpu)
 {
+#ifdef CONFIG_PREEMPT
+	if (preempt_is_disabled() == 0)
+		BUG();
+#endif
 	tsk->thread.pgdir = next->pgd;
 	get_mmu_context(next);
 	set_context(next->context, next->pgd);