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[Rafael David Tinoco <rafael.tinoco@xxxxxxxxxxxxx>]

I'm running the NUMA tests on 3.13 for some time now and it looks like
the change did not introduce any regression...

$ uname -a 
Linux sf00079894trusty 3.13.11-ckt22-201507231149 #2 SMP Thu Jul 23 13:45:04 BRT 2015 x86_64 x86_64 x86_64 GNU/Linux 

I'm using a virtualized 16 Domains / 16 CPUs NUMA environment with the
stress test tool:

$ sudo numactl -H 
available: 16 nodes (0-15) 
node 0 cpus: 0 
node 0 size: 363 MB 
node 0 free: 23 MB 
node 1 cpus: 1 
node 1 size: 121 MB 
node 1 free: 7 MB 
node 2 cpus: 2 
node 2 size: 377 MB 
node 2 free: 23 MB 
node 3 cpus: 3 
node 3 size: 377 MB 
node 3 free: 23 MB 
node 4 cpus: 4 
node 4 size: 377 MB 
node 4 free: 23 MB 
node 5 cpus: 5 
node 5 size: 377 MB 
node 5 free: 23 MB 
node 6 cpus: 6 
node 6 size: 377 MB 
node 6 free: 35 MB 
node 7 cpus: 7 
node 7 size: 313 MB 
node 7 free: 19 MB 
node 8 cpus: 8 
node 8 size: 377 MB 
node 8 free: 61 MB 
node 9 cpus: 9 
node 9 size: 377 MB 
node 9 free: 57 MB 
node 10 cpus: 10 
node 10 size: 377 MB 
node 10 free: 63 MB 
node 11 cpus: 11 
node 11 size: 377 MB 
node 11 free: 30 MB 
node 12 cpus: 12 
node 12 size: 377 MB 
node 12 free: 67 MB 
node 13 cpus: 13 
node 13 size: 377 MB 
node 13 free: 68 MB 
node 14 cpus: 14 
node 14 size: 377 MB 
node 14 free: 68 MB 
node 15 cpus: 15 
node 15 size: 377 MB 
node 15 free: 64 MB 

$ sudo stress --vm 16 --vm-bytes 314572800 --vm-stride 1 --vm-keep &

Causing memory allocations of around 300MB on each node and "touching"
every byte of the allocation (causing all the pages to be "hot" on the
CPU running).

And generating concurrency:

$ sudo stress --cpu 16 &

So kernel scheduler has to migrate tasks, triggering the buggy logic's
fix. I can confirm the logic is being triggered by using ftrace:

$ sudo trace-cmd record -p function -l numa_migrate_preferred -l task_numa_migrate -l migrate_swap -l stop_two_cpus 
$ sudo trace-cmd report | grep stop_two_cpus | wc -l162 

And can't find any regression.

I'll let the tests to run a bit more and will suggest the fix to our
kernel team to merge it as a Stable Release Update for Trusty, Utopic
and Vivid.

-- 
You received this bug notification because you are a member of Kernel
Packages, which is subscribed to linux in Ubuntu.
https://bugs.launchpad.net/bugs/1461620

Title:
  NUMA task migration race condition due to stop task not being  checked
  when balancing happens

Status in linux package in Ubuntu:
  Invalid
Status in linux source package in Trusty:
  In Progress

Bug description:
  It was brought to my attention the follow kernel panic:

  """
  [3367068.076488] Code: 23 66 2e 0f 1f 84 00 00 00 00 00 83 fb 03 75 05 45 84 ed 75 66 f0 41 ff 4c 24 24 74 26 89 da 83 fa 04 74 3d f3 90 41 8b 5c 24 20 <39> d3 74 f0 83 fb 02 75 d7 fa 66 0f 1f 44 00 00 eb d8 66 0f 1f 
  [3367068.092735] BUG: soft lockup - CPU#16 stuck for 22s! [migration/16:153] 
  [3367068.100368] Modules linked in: iptable_raw xt_nat xt_REDIRECT veth openvswitch(OF) gre vxlan ip_tunnel libcrc32c dccp_diag dccp tcp_diag udp_diag inet_diag unix_diag ipt_MASQUERADE iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack nf_conntrack ipt_REJECT xt_CHECKSUM iptable_mangle xt_tcpudp bridge ip6table_filter ip6_tables iptable_filter ip_tables ebtable_nat ebtables x_tables ipmi_devintf 8021q garp stp mrp llc bonding x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel kvm crct10dif_pclmul crc32_pclmul ghash_clmulni_intel aesni_intel gpio_ich joydev aes_x86_64 lrw gf128mul glue_helper ablk_helper ipmi_si cryptd sb_edac wmi lpc_ich edac_core mac_hid acpi_power_meter nfsd auth_rpcgss nfs_acl nfs lockd sunrpc fscache lp parport hid_generic ixgbe fnic libfcoe dca ptp 
  [3367068.100409] libfc megaraid_sas pps_core mdio usbhid scsi_transport_fc hid enic scsi_tgt 
  [3367068.100415] CPU: 16 PID: 153 Comm: migration/16 Tainted: GF O 3.13.0-34-generic #60-Ubuntu 
  [3367068.100417] Hardware name: Cisco Systems Inc UCSC-C220-M3S/UCSC-C220-M3S, BIOS C220M3.1.5.4f.0.111320130449 11/13/2013 
  [3367068.100419] task: ffff881fd2f517f0 ti: ffff881fd2f1c000 task.ti: ffff881fd2f1c000 
  [3367068.100420] RIP: 0010:[<ffffffff810f5944>] [<ffffffff810f5944>] multi_cpu_stop+0x64/0xf0 
  [3367068.100426] RSP: 0000:ffff881fd2f1dd98 EFLAGS: 00000246 
  [3367068.100427] RAX: ffffffff8180af40 RBX: 0000000000000086 RCX: 000000000000a402 
  [3367068.100428] RDX: 0000000000000001 RSI: 0000000000000000 RDI: ffff883e607edb48 
  [3367068.100430] RBP: ffff881fd2f1ddb8 R08: 0000000000000282 R09: 0000000000000001 
  [3367068.100431] R10: 000000000000b6d8 R11: ffff881fc374dc80 R12: 0000000000014440 
  [3367068.100432] R13: ffff881fd291ae00 R14: ffff881fd291ae08 R15: 0000000200000010 
  [3367068.100433] FS: 0000000000000000(0000) GS:ffff881fffd00000(0000) knlGS:0000000000000000 
  [3367068.100434] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 
  [3367068.100435] CR2: 00007f6202134b98 CR3: 0000000001c0e000 CR4: 00000000001407e0 
  [3367068.100437] Stack: 
  [3367068.100438] ffff883e607edb70 ffff881fffd0ede0 ffff881fffd0ede8 ffff883e607edb48 
  [3367068.100441] ffff881fd2f1de78 ffffffff810f5b5e ffffffff8109dfc4 ffff881fffd14440 
  [3367068.100443] ffff881fd2f1de08 ffffffff81097508 0000000000000000 ffff881fffd14440 
  [3367068.100446] Call Trace: 
  [3367068.100450] [<ffffffff810f5b5e>] cpu_stopper_thread+0x7e/0x150 
  [3367068.100454] [<ffffffff8109dfc4>] ? vtime_common_task_switch+0x24/0x40 
  [3367068.100458] [<ffffffff81097508>] ? finish_task_switch+0x128/0x170 
  [3367068.100462] [<ffffffff8171fd41>] ? __schedule+0x381/0x7d0 
  [3367068.100465] [<ffffffff810926af>] smpboot_thread_fn+0xff/0x1b0 
  [3367068.100467] [<ffffffff810925b0>] ? SyS_setgroups+0x1a0/0x1a0 
  [3367068.100470] [<ffffffff8108b3d2>] kthread+0xd2/0xf0 
  [3367068.100473] [<ffffffff8108b300>] ? kthread_create_on_node+0x1d0/0x1d0 
  [3367068.100477] [<ffffffff8172c6bc>] ret_from_fork+0x7c/0xb0 
  [3367068.100479] [<ffffffff8108b300>] ? kthread_create_on_node+0x1d0/0x1d0 
  [3367068.100480] Code: db 85 db 41 0f 95 c5 31 f6 31 d2 eb 23 66 2e 0f 1f 84 00 00 00 00 00 83 fb 03 75 05 45 84 ed 75 66 f0 41 ff 4c 24 24 74 26 89 da <83> fa 04 74 3d f3 90 41 8b 5c 24 20 39 d3 74 f0 83 fb 02 75 d7
  """

  I'm explaining WHY this is happening in the first comments and HOW to
  fix it.

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