I hit the BUG() in schedule() ...

Jun Sun (julian_sun@yahoo.com)
Tue, 19 Jun 2001 23:30:08 -0700 (PDT)


I am running a MIPS machine and hit the following BUG() in
kernel/sched.c:650:

prepare_to_switch();
{
struct mm_struct *mm = next->mm;
struct mm_struct *oldmm = prev->active_mm;
if (!mm) {
if (next->active_mm) BUG(); <======
next->active_mm = oldmm;
atomic_inc(&oldmm->mm_count);
enter_lazy_tlb(oldmm, next, this_cpu);
} else {
if (next->active_mm != mm) BUG();
switch_mm(oldmm, mm, next, this_cpu);
}

The "next" processor is swapper.

I have not looked at it hard enough, but an initial investigation seems
to reveal the cause trivially.

In include/linux/sched.h, the "swapper" task is set such that 'mm' is
NULL and 'active_mm' is &init_mm. So obviously when we switch back to
"swapper" task, we will hit the BUG().

That sounds little too obvious to be true. What am I missing here?

Thanks in advance. Please cc your reply to this email account. I
appreciate that.

Jun

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