Re: [PATCH v3] mm: fix panic in __alloc_pages

Michal Hocko
2021-12-09T09:56:47Z

On Thu 09-12-21 09:28:55, Alexey Makhalov wrote:
>
>
> > On Dec 9, 2021, at 12:46 AM, Michal Hocko <mhocko@suse.com> wrote:
> >
> > On Thu 09-12-21 02:16:17, Alexey Makhalov wrote:
> >> This patch calls alloc_percpu() from setup_arch() while percpu
> >> allocator is not yet initialized (before setup_per_cpu_areas()).
> >
> > Yeah, I haven't realized the pcp is not available. I was not really sure
> > about that. Could you try with the alloc_percpu dropped?
> >
> > Thanks for testing!
> > --
> > Michal Hocko
> > SUSE Labs
>
> It boots now. dmesg has these new messages:
>
> [ 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.

> vCPU/node hot add works.
> Onlining works as well, but with warning. I do not think it is related to the patch:
> [ 36.838838] CPU4 has been hot-added
> [ 36.838987] acpi_processor_hotadd_init:205 cpu 4, node 4, online 0, ndata 00000000e9c7f79b
> [ 48.480498] Built 4 zonelists, mobility grouping on. Total pages: 961440
> [ 48.480508] Policy zone: Normal
> [ 48.508318] smpboot: Booting Node 4 Processor 4 APIC 0x8
> [ 48.509255] Disabled fast string operations
> [ 48.509807] smpboot: CPU 4 Converting physical 8 to logical package 4
> [ 48.509825] smpboot: CPU 4 Converting physical 0 to logical die 4
> [ 48.510040] WARNING: workqueue cpumask: online intersect > possible intersect

I will double check. There are changes required on the hotplug side. I
would like to see that this one doesn't blow up before diving there.

> [ 48.510324] vmware: vmware-stealtime: cpu 4, pa 3e667000
> [ 48.511311] Will online and init hotplugged CPU: 4
>
> Hot remove does not quite work. It might be issue in ACPI/Firmware code or Hypervisor. Debugging…
>
> Do you want me to perform any specific tests?

No, not really. AFAIU your issue has been reproducible during boot and
that seems to be fixed. I will work on the hotplug side of the things
and post something resembling a real patch soon. That would require also
memory hotplug testing.

Thanks for your help!
--
Michal Hocko
SUSE Labs