diff -Nru link/arch/mips/mm/tlb-sb1.c.orig link/arch/mips/mm/tlb-sb1.c
--- link/arch/mips/mm/tlb-sb1.c.orig	Tue Jan 21 13:54:59 2003
+++ link/arch/mips/mm/tlb-sb1.c	Tue Jan 21 13:58:50 2003
@@ -172,9 +172,13 @@
 			}
 			write_c0_entryhi(oldpid);
 		} else {
-			get_new_mmu_context(mm, cpu);
-			if (mm == current->active_mm)
+			if (mm == current->active_mm) {
+				get_new_mmu_context(mm, cpu);
 				write_c0_entryhi(cpu_asid(cpu, mm));
+			} else {
+				/* drop the current context completely */
+				CPU_CONTEXT(cpu, mm) = 0;
+			}
 		}
 	}
 	__restore_flags(flags);
@@ -258,9 +262,12 @@
 	__save_and_cli(flags);
 	cpu = smp_processor_id();
 	if (cpu_context(cpu, mm) != 0) {
-		get_new_mmu_context(mm, smp_processor_id());
 		if (mm == current->active_mm) {
+			get_new_mmu_context(mm, smp_processor_id());
 			write_c0_entryhi(cpu_asid(cpu, mm));
+		} else {
+			/* drop the current context completely */
+			CPU_CONTEXT(cpu, mm) = 0;
 		}
 	}
 	__restore_flags(flags);
diff -Nru link/include/asm-mips/mmu_context.h.orig link/include/asm-mips/mmu_context.h
--- link/include/asm-mips/mmu_context.h.orig	Tue Jan 21 13:55:43 2003
+++ link/include/asm-mips/mmu_context.h	Tue Jan 21 14:01:19 2003
@@ -89,12 +89,25 @@
 static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
                              struct task_struct *tsk, unsigned cpu)
 {
+	unsigned long flags;
+
+	__save_and_cli(flags);
+
 	/* Check if our ASID is of an older version and thus invalid */
 	if ((cpu_context(cpu, next) ^ asid_cache(cpu)) & ASID_VERSION_MASK)
 		get_new_mmu_context(next, cpu);
 
 	write_c0_entryhi(cpu_context(cpu, next));
 	TLBMISS_HANDLER_SETUP_PGD(next->pgd);
+
+	/*
+	 * Mark current->active_mm as not "active" anymore.
+	 * We don't want to mislead possible IPI tlb flush routines.
+	 */
+	clear_bit(cpu, &prev->cpu_vm_mask);
+	set_bit(cpu, &next->cpu_vm_mask);
+
+	__restore_flags(flags);
 }
 
 /*
@@ -112,11 +125,17 @@
 static inline void
 activate_mm(struct mm_struct *prev, struct mm_struct *next)
 {
+	unsigned long flags;
+
+	__save_and_cli(flags);
+
 	/* Unconditionally get a new ASID.  */
 	get_new_mmu_context(next, smp_processor_id());
 
 	write_c0_entryhi(cpu_context(smp_processor_id(), next));
 	TLBMISS_HANDLER_SETUP_PGD(next->pgd);
+	
+	__restore_flags(flags);
 }
 
 #endif /* _ASM_MMU_CONTEXT_H */