[PATCH 0/2] workqueue: fix a bug when numa mapping is changed

[Gu Zheng]

Yasuaki Ishimatsu found that with node online/offline, cpu<->node
relationship is established. Because workqueue uses a info which was
established at boot time, but it may be changed by node hotpluging.

Once pool->node points to a stale node, following allocation failure
happens.
  ==
     SLUB: Unable to allocate memory on node 2 (gfp=0x80d0)
      cache: kmalloc-192, object size: 192, buffer size: 192, default
order:
    1, min order: 0
      node 0: slabs: 6172, objs: 259224, free: 245741
      node 1: slabs: 3261, objs: 136962, free: 127656
  ==

As the apicid <--> node relationship is persistent, so the root cause is the
cpu-id <-> lapicid mapping is not persistent (because the currently implementation
always choose the first free cpu id for the new added cpu), so if we can build
persistent cpu-id <-> lapicid relationship, this problem will be fixed.

Please refer to https://lkml.org/lkml/2015/2/27/145 for the previous discussion.

Gu Zheng (2):
  x86/cpu hotplug: make lapicid <-> cpuid mapping persistent
  workqueue: update per cpu workqueue's numa affinity when cpu
    preparing online

 arch/x86/kernel/apic/apic.c |   31 ++++++++++++++++++++++++++++++-
 kernel/workqueue.c          |    1 +
 2 files changed, 31 insertions(+), 1 deletions(-)

-- 
1.7.7

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