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    SubjectRe: [RFC Patch V1 01/30] mm, kernel: Use cpu_to_mem()/numa_mem_id() to support memoryless node
    Hi Paul,

    On 11.07.2014 [08:14:05 -0700], Paul E. McKenney wrote:
    > On Fri, Jul 11, 2014 at 03:37:18PM +0800, Jiang Liu wrote:
    > > When CONFIG_HAVE_MEMORYLESS_NODES is enabled, cpu_to_node()/numa_node_id()
    > > may return a node without memory, and later cause system failure/panic
    > > when calling kmalloc_node() and friends with returned node id.
    > > So use cpu_to_mem()/numa_mem_id() instead to get the nearest node with
    > > memory for the/current cpu.
    > >
    > > If CONFIG_HAVE_MEMORYLESS_NODES is disabled, cpu_to_mem()/numa_mem_id()
    > > is the same as cpu_to_node()/numa_node_id().
    > >
    > > Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
    >
    > For the rcutorture piece:
    >
    > Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    >
    > Or if you separate the kernel/rcu/rcutorture.c portion into a separate
    > patch, I will queue it separately.

    Just FYI, based upon a separate discussion with Tejun and others, it
    seems to be preferred to avoid the proliferation of cpu_to_mem
    throughout the kernel blindly. For kthread_create_on_node(), I'm going
    to try and fix the underlying issue and so you, as the caller, should
    still specify the NUMA node you are running the kthread on
    (cpu_to_node), not where you expect the memory to come from
    (cpu_to_mem).

    Thanks,
    Nish



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