From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 21 Oct 2008 13:19:51 +0200 From: Ingo Molnar Subject: Re: [memcg BUG] unable to handle kernel NULL pointer derefence at 00000000 Message-ID: <20081021111951.GB4476@elte.hu> References: <20081021161621.bb51af90.kamezawa.hiroyu@jp.fujitsu.com> <48FD82E3.9050502@cn.fujitsu.com> <20081021171801.4c16c295.kamezawa.hiroyu@jp.fujitsu.com> <48FD943D.5090709@cn.fujitsu.com> <20081021175735.0c3d3534.kamezawa.hiroyu@jp.fujitsu.com> <48FD9D30.2030500@cn.fujitsu.com> <20081021182551.0158a47b.kamezawa.hiroyu@jp.fujitsu.com> <48FDA6D4.3090809@cn.fujitsu.com> <20081021191417.02ab97cc.kamezawa.hiroyu@jp.fujitsu.com> <48FDB584.7080608@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <48FDB584.7080608@cn.fujitsu.com> Sender: owner-linux-mm@kvack.org Return-Path: To: Li Zefan Cc: KAMEZAWA Hiroyuki , balbir@linux.vnet.ibm.com, Paul Menage , Daisuke Nishimura , linux-mm@kvack.org, mel@csn.ul.ie List-ID: * Li Zefan wrote: > > Oh! thanks...but it seems pc->page is NULL in the middle of ZONE_NORMAL.. > > == > > Normal 0x00001000 -> 0x000373fe > > == > > This is appearently in the range of page_cgroup initialization. > > (if pgdat->node_page_cgroup is initalized correctly...) > > > > I think write to page_cgroup->page happens only at initialization. > > Hmm ? not initilization failure but curruption ? > > > > Yes, curruption. I didn't find informatation about initialization failure. > > > What happens if replacing __alloc_bootmem() with vmalloc() in page_cgroup.c init ? > > > > So I did this change, and the box booted up without any problem. > > diff --git a/mm/page_cgroup.c b/mm/page_cgroup.c > index 5d86550..82a30b1 100644 > --- a/mm/page_cgroup.c > +++ b/mm/page_cgroup.c > @@ -48,8 +48,7 @@ static int __init alloc_node_page_cgroup(int nid) > > table_size = sizeof(struct page_cgroup) * nr_pages; > > - base = __alloc_bootmem_node_nopanic(NODE_DATA(nid), > - table_size, PAGE_SIZE, __pa(MAX_DMA_ADDRESS)); > + base = vmalloc_node(table_size, nid); > if (!base) > return -ENOMEM; i have this: CONFIG_FAILSLAB=y CONFIG_FAIL_PAGE_ALLOC=y # CONFIG_FAIL_MAKE_REQUEST is not set CONFIG_FAIL_IO_TIMEOUT=y so the bug was perhaps that the __alloc_bootmem_node_nopanic() failed and this code continued silently? vmalloc_node() probably is more agressive about allocating memory. Ingo -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org