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    Subject[patch V2 14/24] cpu/hotplug: Use stop_machine_cpuslocked() in takedown_cpu()
    From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

    takedown_cpu() is a cpu hotplug function invoking stop_machine(). The cpu
    hotplug machinery holds the hotplug lock for write.

    stop_machine() invokes get_online_cpus() as well. This is correct, but
    prevents the conversion of the hotplug locking to a percpu rwsem.

    Use stop_machine_cpuslocked() to avoid the nested call.

    Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

    ---
    kernel/cpu.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/kernel/cpu.c
    +++ b/kernel/cpu.c
    @@ -701,7 +701,7 @@ static int takedown_cpu(unsigned int cpu
    /*
    * So now all preempt/rcu users must observe !cpu_active().
    */
    - err = stop_machine(take_cpu_down, NULL, cpumask_of(cpu));
    + err = stop_machine_cpuslocked(take_cpu_down, NULL, cpumask_of(cpu));
    if (err) {
    /* CPU refused to die */
    irq_unlock_sparse();

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