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    SubjectRe: Fw: Re: [mm PATCH 4/6] RCU: (now) CPU hotplug
    On Mon, Jan 29, 2007 at 06:45:49PM -0800, Paul E. McKenney wrote:
    >
    > static int _cpu_down(unsigned int cpu)
    > {
    > int err;
    > struct task_struct *p;
    > cpumask_t old_allowed, tmp;
    >
    > if (num_online_cpus() == 1)
    > return -EBUSY;
    >
    > if (!cpu_online(cpu))
    > return -EINVAL;
    >
    > if (freeze_processes()) {
    > err = -EBUSY;
    > goto out_freeze_notify_failed;
    > }
    > err = raw_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE,
    > (void *)(long)cpu);
    > if (err == NOTIFY_BAD) {
    > printk("%s: attempt to take down CPU %u failed\n",
    > __FUNCTION__, cpu);
    > err = -EINVAL;
    > goto out_freeze_notify_failed;
    > }
    >
    > /* Ensure that we are not runnable on dying cpu */
    > old_allowed = current->cpus_allowed;
    > tmp = CPU_MASK_ALL;
    > cpu_clear(cpu, tmp);
    > set_cpus_allowed(current, tmp);
    >
    > mutex_lock(&cpu_bitmask_lock);

    We won't be needing this lock either, since it forms the core of
    the unpopular lock_cpu_hotplug :-)

    > p = __stop_machine_run(take_cpu_down, NULL, cpu);
    > mutex_unlock(&cpu_bitmask_lock);

    Looks good.

    I'm wondering if we'll need to try_to_freeze in the fork and exit code
    as well :?

    Thanks and Regards
    gautham.
    --
    Gautham R Shenoy
    Linux Technology Center
    IBM India.
    "Freedom comes with a price tag of responsibility, which is still a bargain,
    because Freedom is priceless!"
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