Re: BUG(): sched.c: Line 944 - 2.5.35

Adam J. Richter (adam@yggdrasil.com)
Mon, 16 Sep 2002 09:36:15 -0700


Shawn Starr wrote:

>Kernel 2.5.35:
>
>code resides in main schedule() function:
>
>if (unlikely(in_atomic()))
> BUG();

That line prevously checked in_interrupt (in 2.5.34) instead of
in_atomic. If you have CONFIG_PREEMPT defined, the definition of in_atomic
in linux-2.5.35/include/asm-i386/hardirq.h is:

# define in_atomic() (preempt_count() != kernel_locked())

When I see this problem at boot, preempt_count() returns 0x4000000
(PREEMPT_ACTIVE) and kernel_locked() returns 0.

I don't understand the semantics of PREEMPT_ACTIVE to know
whether to

(1) change the test back to using in_interrupt instead of in_atomic, or
(2) change the definition of in_atomic(), or
(3) look for a bug somewhere else.

However, I know experimentally that changing the test back to
using in_interrupt() results in a possibly unrelated BUG() at line 279
of rmap.c:

void page_remove_rmap(struct page * page, pte_t * ptep)
{
pte_addr_t pte_paddr = ptep_to_paddr(ptep);
struct pte_chain *pc;

if (!page || !ptep)
BUG();
if (!pfn_valid(page_to_pfn(page)) || PageReserved(page))
return;

pte_chain_lock(page);

BUG_ON(page->pte.direct == 0);

Adam J. Richter __ ______________ 575 Oroville Road
adam@yggdrasil.com \ / Milpitas, California 95035
+1 408 309-6081 | g g d r a s i l United States of America
"Free Software For The Rest Of Us."
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/