linux-kernel - Re: [PATCH v3] mm: fix panic in __alloc

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Date:   Fri, 10 Dec 2021 10:11:13 +0100
From:   Michal Hocko <mhocko@...e.com>
To:     Alexey Makhalov <amakhalov@...are.com>
Cc:     Dennis Zhou <dennis@...nel.org>,
        Eric Dumazet <eric.dumazet@...il.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Hildenbrand <david@...hat.com>,
        Oscar Salvador <osalvador@...e.de>, Tejun Heo <tj@...nel.org>,
        Christoph Lameter <cl@...ux.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH v3] mm: fix panic in __alloc_pages

On Thu 09-12-21 19:01:03, Alexey Makhalov wrote:
> 
> 
> > On Dec 9, 2021, at 5:29 AM, Michal Hocko <mhocko@...e.com> wrote:
> > 
> > On Thu 09-12-21 10:23:52, Alexey Makhalov wrote:
> >> 
> >> 
> >>> On Dec 9, 2021, at 1:56 AM, Michal Hocko <mhocko@...e.com> wrote:
> >>> 
> >>> On Thu 09-12-21 09:28:55, Alexey Makhalov wrote:
> >>>> 
> >>>> 
> >>>> [    0.081777] Node 4 uninitialized by the platform. Please report with boot dmesg.
> >>>> [    0.081790] Initmem setup node 4 [mem 0x0000000000000000-0x0000000000000000]
> >>>> ...
> >>>> [    0.086441] Node 127 uninitialized by the platform. Please report with boot dmesg.
> >>>> [    0.086454] Initmem setup node 127 [mem 0x0000000000000000-0x0000000000000000]
> >>> 
> >>> Interesting that only those two didn't get a proper arch specific
> >>> initialization. Could you check why? I assume init_cpu_to_node
> >>> doesn't see any CPU pointing at this node. Wondering why that would be
> >>> the case but that can be a bug in the affinity tables.
> >> 
> >> My bad shrinking. Not just these 2, but all possible and not present nodes from 4 to 127
> >> are having this message.
> > 
> > Does that mean that your possible (but offline) cpus do not set their
> > affinity?
> > 
> Hi Michal,
> 
> I didn’t quite gut a question here. Do you mean scheduler affinity for offlined/not present CPUs?
> From the patch, this message should be printed for every possible offlined node:
> 	for_each_node(nid) {
> ...
> 		if (!node_online(nid)) {
> 			pr_warn("Node %d uninitialized by the platform. Please report with boot dmesg.\n", nid);

Sure, let me expand on this a bit. X86 initialization code
(init_cpu_to_node) does
        for_each_possible_cpu(cpu) {
                int node = numa_cpu_node(cpu);

                if (node == NUMA_NO_NODE)
                        continue;

                if (!node_online(node))
                        init_memory_less_node(node);

                numa_set_node(cpu, node);
        }

which means that a memory less node is not initialized either when
	- your offline CPUs are not listed in possible cpus for some
	  reason
	- or they do not have any node affinity (numa_cpu_node is
	  NUMA_NO_NODE).

Could you check what is the reason in your particular case please?

-- 
Michal Hocko
SUSE Labs