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

KAMEZAWA Hiroyuki
2006-09-22T03:27:46Z

On Thu, 21 Sep 2006 20:08:06 -0700
Andrew Morton <akpm@osdl.org> wrote:

> But why did the kmalloc() fail?
>
>
from this:

==
#define NOTIFY_DONE 0x0000 /* Don't care */
#define NOTIFY_OK 0x0001 /* Suits me */
#define NOTIFY_STOP_MASK 0x8000 /* Don't call further */
#define NOTIFY_BAD (NOTIFY_STOP_MASK|0x0002)
==

I gues someone returns NOTIFY_BAD before pageset_cpuup_callback() is called.
When CPU_UP_CANCELED comes, pageset_cpuup_callback() can't know zone_pcp()
is kmalloced or not. Is this ugly ?

-Kame

Before kfree(), we should check zone_pcp() is not boot_pageset[].

Signed-Off-By KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

Index: linux-2.6.18/mm/page_alloc.c
===================================================================
--- linux-2.6.18.orig/mm/page_alloc.c 2006-09-20 12:42:06.000000000 +0900
+++ linux-2.6.18/mm/page_alloc.c 2006-09-22 12:22:03.000000000 +0900
@@ -1844,9 +1844,11 @@

for_each_zone(zone) {
struct per_cpu_pageset *pset = zone_pcp(zone, cpu);
-
- zone_pcp(zone, cpu) = NULL;
- kfree(pset);
+ /* When canceled, zone_pcp still points to boot_pageset[] */
+ if (zone_pcp(zone, cpu) != &boot_pageset[cpu]) {
+ zone_pcp(zone, cpu) = NULL;
+ kfree(pset);
+ }
}
}