Subject: Re: mm: Initialise per_cpu_nodestats for all online pgdats at boot

From: Mel Gorman <[email-masked]>
Date: Thu, 11 Aug 2016 10:28:08 +0100

On Wed, Aug 10, 2016 at 12:59:40PM -0500, Reza Arbab wrote:
> On Thu, Aug 04, 2016 at 10:24:04AM +0100, Mel Gorman wrote:
> >[    1.713998] Unable to handle kernel paging request for data at address 0xff7a10000
> >[    1.714164] Faulting instruction address: 0xc000000000270cd0
> >[    1.714304] Oops: Kernel access of bad area, sig: 11 [#1]
> >[    1.714414] SMP NR_CPUS=2048 NUMA PowerNV
> >[    1.714530] Modules linked in:
> >[    1.714647] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.7.0-kvm+ #118
> >[    1.714786] task: c000000ff0680010 task.stack: c000000ff0704000
> >[    1.714926] NIP: c000000000270cd0 LR: c000000000270ce8 CTR: 0000000000000000
> >[    1.715093] REGS: c000000ff0707900 TRAP: 0300   Not tainted  (4.7.0-kvm+)
> >[    1.715232] MSR: 9000000102009033 <SF,HV,VEC,EE,ME,IR,DR,RI,LE,TM[E]>  CR: 846b6824  XER: 20000000
> >[    1.715748] CFAR: c000000000008768 DAR: 0000000ff7a10000 DSISR: 42000000 SOFTE: 1
> >GPR00: c000000000270d08 c000000ff0707b80 c0000000011fb200 0000000000000000
> >GPR04: 0000000000000800 0000000000000000 0000000000000000 0000000000000000
> >GPR08: ffffffffffffffff 0000000000000000 0000000ff7a10000 c00000000122aae0
> >GPR12: c000000000a1e440 c00000000fb80000 c00000000000c188 0000000000000000
> >GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> >GPR20: 0000000000000000 0000000000000000 0000000000000000 c000000000cecad0
> >GPR24: c000000000d035b8 c000000000d6cd18 c000000000d6cd18 c000001fffa86300
> >GPR28: 0000000000000000 c000001fffa96300 c000000001230034 c00000000122eb18
> >[    1.717484] NIP [c000000000270cd0] refresh_zone_stat_thresholds+0x80/0x240
> >[    1.717568] LR [c000000000270ce8] refresh_zone_stat_thresholds+0x98/0x240
> >[    1.717648] Call Trace:
> >[    1.717687] [c000000ff0707b80] [c000000000270d08] refresh_zone_stat_thresholds+0xb8/0x240 (unreliable)
> 
> I've been investigating node hotplug. That path is also going to require
> initialization of per_cpu_nodestats. This worked for me:
> 

Fix looks ok. Can you add a proper changelog to it including an example
oops or do you need me to do it?

-- 
Mel Gorman
SUSE Labs