Re: [BUG] i386 2.6.18 cpu_up: attempt to bring up CPU 4 failed : kernel BUG at mm/slab.c:2698!

[Andrew Morton <akpm@osdl.org>]

On Fri, 22 Sep 2006 11:24:27 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:

> On Thu, 21 Sep 2006 18:34:03 -0700
> keith mannthey <kmannth@us.ibm.com> wrote:
> 
> > That unhappy caller in the chain is cpuup_callback in mm/slab.c.  I am
> > still working out as to why, there is a lot going on if this function. 
> > 
> > > b) pageset_cpuup_callback()'s CPU_UP_CANCELED path possibly hasn't been
> > >    tested before.  I'd be guessing that we're not zeroing out the
> > >    zone.pageset[] array when the `struct zone' is first allocated, but I
> > >    don't immediately recall where that code lives.
> > 
> 
> How about here ?
> == at boot time in mm/page_alloc.c ==
> free_area_init_core()
> 	->zone_pcp_init(zone);
>         for (cpu = 0; cpu < NR_CPUS; cpu++) {
> #ifdef CONFIG_NUMA
>                 /* Early boot. Slab allocator not functional yet */
>                 zone_pcp(zone, cpu) = &boot_pageset[cpu];
>                 setup_pageset(&boot_pageset[cpu],0);
> #else
>                 setup_pageset(zone_pcp(zone,cpu), batch);
> #endif
>         }
> ==================
> 
> Not zero-cleared.
> 

Actually, I'd point the finger at process_zones().  If that kmalloc()
fails, we leave garbage in the entries for the remaining zones.  But
free_zone_pagesets() kfrees all of them, uncluding the garbage pointers.

So something like...

--- a/mm/page_alloc.c~a
+++ a/mm/page_alloc.c
@@ -1811,11 +1811,14 @@ static struct per_cpu_pageset boot_pages
  */
 static int __cpuinit process_zones(int cpu)
 {
-	struct zone *zone, *dzone;
+	struct zone *zone;
 
-	for_each_zone(zone) {
+	for_each_zone(zone)
+		zone_pcp(zone, cpu) = NULL;
 
-		zone_pcp(zone, cpu) = kmalloc_node(sizeof(struct per_cpu_pageset),
+	for_each_zone(zone) {
+		zone_pcp(zone, cpu) =
+			kmalloc_node(sizeof(struct per_cpu_pageset),
 					 GFP_KERNEL, cpu_to_node(cpu));
 		if (!zone_pcp(zone, cpu))
 			goto bad;
@@ -1824,17 +1827,16 @@ static int __cpuinit process_zones(int c
 
 		if (percpu_pagelist_fraction)
 			setup_pagelist_highmark(zone_pcp(zone, cpu),
-			 	(zone->present_pages / percpu_pagelist_fraction));
+			    (zone->present_pages / percpu_pagelist_fraction));
 	}
 
 	return 0;
 bad:
-	for_each_zone(dzone) {
-		if (dzone == zone)
-			break;
-		kfree(zone_pcp(dzone, cpu));
-		zone_pcp(dzone, cpu) = NULL;
+	for_each_zone(zone) {
+		kfree(zone_pcp(zone, cpu));
+		zone_pcp(zone, cpu) = NULL;
 	}
+	printk(KERN_EMERG "%s: kmalloc() failed\n", __FUNCTION__);
 	return -ENOMEM;
 }
 
_


But why did the kmalloc() fail?