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SubjectRe: assert/crash in __rmqueue() when enabling CONFIG_NUMA

* Nick Piggin <npiggin@suse.de> wrote:

> On Wed, Apr 19, 2006 at 01:21:30PM +0200, Ingo Molnar wrote:
> > the 2.6.17-rc2 kernel built with the attached config crashes quite
> > easily under minimal load. Disabling CONFIG_NUMA makes it robust again.
> > Crashlog attached.
>
> It would be interesting to know which assertion failed. I guess it
> might be a zone alignment problem -- it would be interesting to turn
> the 2 HOLES_IN_ZONE tests into BUG_ONs, and enable them (ie. move them
> out of HOLES_IN_ZONE).

ok, i added a couple of printks (see the patch below), and got this:

zone c1f0a600 (HighMem):
pfn: 00037d00
zone->zone_start_pfn: 00037e00
zone->spanned_pages: 00007e00
zone->zone_start_pfn + zone->spanned_pages: 0003fc00
------------[ cut here ]------------
kernel BUG at mm/page_alloc.c:524!
so the pfn is 1MB below the zone's start address - not good. You can
find the full bootup log at:

http://redhat.com/~mingo/misc/crash.log

the log should also give an idea about how the zones are layed out, etc.
Note that this is an ordinary desktop dual-core box with 1GB RAM booting
an allyesconfig NUMA kernel. I suspect this could be some bootup-time
zone sizing problem? The config is at:

http://redhat.com/~mingo/misc/config

(the crash is easy to reproduce, so let me know if i can do anything
else to debug this.)

Ingo

Index: linux/mm/page_alloc.c
===================================================================
--- linux.orig/mm/page_alloc.c
+++ linux/mm/page_alloc.c
@@ -100,17 +100,32 @@ static int page_outside_zone_boundaries(
ret = 1;
} while (zone_span_seqretry(zone, seq));

+#define P(x) printk("%s: %08lx\n", #x, x)
+
+ if (ret) {
+ printk("zone %p (%s):\n", zone, zone->name);
+ P(pfn);
+ P(zone->zone_start_pfn);
+ P(zone->spanned_pages);
+ P(zone->zone_start_pfn + zone->spanned_pages);
+ }
+
return ret;
}

static int page_is_consistent(struct zone *zone, struct page *page)
{
-#ifdef CONFIG_HOLES_IN_ZONE
- if (!pfn_valid(page_to_pfn(page)))
+ if (!pfn_valid(page_to_pfn(page))) {
+ printk("BUG: pfn: %08lx, page: %p\n",
+ page_to_pfn(page), page);
+ dump_stack();
return 0;
-#endif
- if (zone != page_zone(page))
+ }
+ if (zone != page_zone(page)) {
+ printk("zone: %p != %p == page_zone(%p)\n",
+ zone, page_zone(page), page);
return 0;
+ }

return 1;
}
@@ -292,10 +307,12 @@ __find_combined_index(unsigned long page
*/
static inline int page_is_buddy(struct page *page, int order)
{
-#ifdef CONFIG_HOLES_IN_ZONE
- if (!pfn_valid(page_to_pfn(page)))
+ if (!pfn_valid(page_to_pfn(page))) {
+ printk("BUG: pfn: %08lx, page: %p, order: %d\n",
+ page_to_pfn(page), page, order);
+ dump_stack();
return 0;
-#endif
+ }

if (PageBuddy(page) && page_order(page) == order) {
BUG_ON(page_count(page) != 0);
-
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