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    SubjectRe: [PATCH 2/5] sched/deadline: Remove cpu_active_mask from cpudl_find()
    On Mon, Jan 19, 2015 at 04:49:37AM +0000, Xunlei Pang wrote:
    > cpu_active_mask is rarely changeable, so remove this operation
    > to gain a little performance.
    >
    > If there is a change in cpu_active_mask, rq_online_dl() and
    > rq_offline_dl() should take care of it normally, so cpudl::
    > free_cpus carries enough information for us.
    >
    > For the rare case(causing a task put onto a dying cpu) which
    > rq_offline_dl() can't handle timely, then it can be handled
    > through _cpu_down()->...->multi_cpu_stop()->migration_call()
    > ->migrate_tasks(), preventing the task from hanging on the
    > dead cpu.

    Maybe; I'll need to go crawl through the long and twisted history of
    active_mask here :/


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