BUG: at kernel/sched.c:4031 __schedule()

Hi
I run 2.6.20-rt8 kernel on board like innovator1510 (OMAP5910 cpu)
I notice in boot string:
BUG: at kernel/sched.c:4031 __schedule()
kernel complain interrupts are enabled after schedule.

digging in sched.c I figured out that interrupts are disabled when cpu 
enter __sched(),
but are enabled when it went out.
Playing with the code i can find out, that problem is in the next 
fragment: (line 4024)

   if (likely(prev != next)) {
       next->timestamp = now;
       rq->nr_switches++;
       rq->curr = next;
       ++*switch_count;

       prepare_task_switch(rq, next);
       prev = context_switch(rq, prev, next);
       barrier();
       trace_special_pid(prev->pid, PRIO(prev), PRIO(current));
       /*
        * this_rq must be evaluated again because prev may have moved
        * CPUs since it called schedule(), thus the 'rq' on its stack
        * frame will be invalid.
        */
       finish_task_switch(this_rq(), prev);
       __preempt_enable_no_resched();
   } else {

in prepare_task_switch(rq, next); interrupts are enabled,
but in finish_task_switch(this_rq(), prev); interrupts not disabled
(it look not symmetrical for me).

Can anybody tell - is this right behavior?
I think interrupts should be disabled somewhere in this fragment,
or may be, scheduler should not complain?

Oleg Kechin.