> On 12-Mar-2020, at 10:57 AM, Srikar Dronamraju <srikar@linux.vnet.ibm.com> wrote:
> 
> * Michal Hocko <mhocko@kernel.org> [2020-03-11 12:57:35]:
> 
>> On Wed 11-03-20 16:32:35, Srikar Dronamraju wrote:
>>> A Powerpc system with multiple possible nodes and with CONFIG_NUMA
>>> enabled always used to have a node 0, even if node 0 does not any cpus
>>> or memory attached to it. As per PAPR, node affinity of a cpu is only
>>> available once its present / online. For all cpus that are possible but
>>> not present, cpu_to_node() would point to node 0.
>>> 
>>> To ensure a cpuless, memoryless dummy node is not online, powerpc need
>>> to make sure all possible but not present cpu_to_node are set to a
>>> proper node.
>> 
>> Just curious, is this somehow related to
>> http://lkml.kernel.org/r/20200227182650.GG3771@dhcp22.suse.cz?
>> 
> 
> The issue I am trying to fix is a known issue in Powerpc since many years.
> So this surely not a problem after a75056fc1e7c (mm/memcontrol.c: allocate
> shrinker_map on appropriate NUMA node"). 
> 
> I tried v5.6-rc4 + a75056fc1e7c but didnt face any issues booting the
> kernel. Will work with Sachin/Abdul (reporters of the issue).
> 

I applied this 3 patch series on top of March 11 next tree (commit d44a64766795 )
The kernel still fails to boot with same call trace.

[    6.159357] BUG: Kernel NULL pointer dereference on read at 0x000073b0
[    6.159363] Faulting instruction address: 0xc0000000003d7174
[    6.159368] Oops: Kernel access of bad area, sig: 11 [#1]
[    6.159372] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
[    6.159378] Modules linked in:
[    6.159382] CPU: 17 PID: 1 Comm: systemd Not tainted 5.6.0-rc5-next-20200311-autotest+ #1
[    6.159388] NIP:  c0000000003d7174 LR: c0000000003d7714 CTR: c000000000400e70
[    6.159393] REGS: c0000008b36836d0 TRAP: 0300   Not tainted  (5.6.0-rc5-next-20200311-autotest+)
[    6.159398] MSR:  8000000000009033 <SF,EE,ME,IR,DR,RI,LE>  CR: 24004848  XER: 00000000
[    6.159406] CFAR: c00000000000dec4 DAR: 00000000000073b0 DSISR: 40000000 IRQMASK: 1
[    6.159406] GPR00: c0000000003d7714 c0000008b3683960 c00000000155e300 c0000008b301f500
[    6.159406] GPR04: 0000000000000dc0 0000000000000000 c0000000003456f8 c0000008bb198620
[    6.159406] GPR08: 00000008ba0f0000 0000000000000001 0000000000000000 0000000000000000
[    6.159406] GPR12: 0000000024004848 c00000001ec55e00 0000000000000000 0000000000000000
[    6.159406] GPR16: c0000008b0a82048 c000000001595898 c000000001750ca8 0000000000000002
[    6.159406] GPR20: c000000001750cb8 c000000001624478 0000000fffffffe0 5deadbeef0000122
[    6.159406] GPR24: 0000000000000001 0000000000000dc0 0000000000000000 c0000000003456f8
[    6.159406] GPR28: c0000008b301f500 c0000008bb198620 0000000000000000 c00c000002285a40
[    6.159453] NIP [c0000000003d7174] ___slab_alloc+0x1f4/0x760
[    6.159458] LR [c0000000003d7714] __slab_alloc+0x34/0x60
[    6.159462] Call Trace:
[    6.159465] [c0000008b3683a40] [c0000008b3683a70] 0xc0000008b3683a70
[    6.159471] [c0000008b3683a70] [c0000000003d8b20] __kmalloc_node+0x110/0x490
[    6.159477] [c0000008b3683af0] [c0000000003456f8] kvmalloc_node+0x58/0x110
[    6.159483] [c0000008b3683b30] [c000000000400f78] mem_cgroup_css_online+0x108/0x270
[    6.159489] [c0000008b3683b90] [c000000000236ed8] online_css+0x48/0xd0
[    6.159494] [c0000008b3683bc0] [c00000000023ffac] cgroup_apply_control_enable+0x2ec/0x4d0
[    6.159501] [c0000008b3683ca0] [c0000000002437c8] cgroup_mkdir+0x228/0x5f0
[    6.159506] [c0000008b3683d10] [c000000000521780] kernfs_iop_mkdir+0x90/0xf0
[    6.159512] [c0000008b3683d50] [c00000000043f670] vfs_mkdir+0x110/0x230
[    6.159517] [c0000008b3683da0] [c000000000443150] do_mkdirat+0xb0/0x1a0
[    6.159523] [c0000008b3683e20] [c00000000000b278] system_call+0x5c/0x68
[    6.159527] Instruction dump:
[    6.159531] 7c421378 e95f0000 714a0001 4082fff0 4bffff64 60000000 60000000 faa10088
[    6.159538] 3ea2000c 3ab56178 7b4a1f24 7d55502a <e94a73b0> 2faa0000 409e0394 3d02002a
[    6.159545] ---[ end trace 36d65cb66091a5b6 ]—

Boot log attached.

Thanks
-Sachin