diff -ru sched-2.5.59-03/kernel/sched.c sched-2.5.59-04/kernel/sched.c
--- sched-2.5.59-03/kernel/sched.c	Tue Feb  4 00:31:43 2003
+++ sched-2.5.59-04/kernel/sched.c	Tue Feb  4 00:40:20 2003
@@ -151,6 +151,7 @@
 	unsigned long nr_running, nr_switches, expired_timestamp,
 			nr_uninterruptible;
 	task_t *curr, *idle;
+	struct mm_struct *prev_mm;
 	prio_array_t *active, *expired, arrays[2];
 	int prev_nr_running[NR_CPUS];
 #ifdef CONFIG_NUMA
@@ -560,7 +561,7 @@
  * context_switch - switch to the new MM and the new
  * thread's register state.
  */
-static inline task_t * context_switch(task_t *prev, task_t *next)
+static inline task_t * context_switch(runqueue_t *rq, task_t *prev, task_t *next)
 {
 	struct mm_struct *mm = next->mm;
 	struct mm_struct *oldmm = prev->active_mm;
@@ -574,7 +575,7 @@
 
 	if (unlikely(!prev->mm)) {
 		prev->active_mm = NULL;
-		mmdrop(oldmm);
+		rq->prev_mm = oldmm;
 	}
 
 	/* Here we just switch the register state and the stack. */
@@ -1213,14 +1214,19 @@
 	RCU_qsctr(prev->thread_info->cpu)++;
 
 	if (likely(prev != next)) {
+		struct mm_struct *prev_mm;
 		rq->nr_switches++;
 		rq->curr = next;
 	
 		prepare_arch_switch(rq, next);
-		prev = context_switch(prev, next);
+		prev = context_switch(rq, prev, next);
 		barrier();
 		rq = this_rq();
+		prev_mm = rq->prev_mm;
+		rq->prev_mm = NULL;
 		finish_arch_switch(rq, prev);
+		if (prev_mm)
+			mmdrop(prev_mm);
 	} else
 		spin_unlock_irq(&rq->lock);