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    Subject[RFC PATCH 04/10] S390: smp: remove call to ipi_call_lock()/ipi_call_unlock()
    Date
    From: Yong Zhang <yong.zhang@windriver.com>

    1) call_function.lock used in smp_call_function_many() is just to protect
    call_function.queue and &data->refs, cpu_online_mask is outside of the
    lock. And it's not necessary to protect cpu_online_mask,
    because data->cpumask is pre-calculate and even if a cpu is brougt up
    when calling arch_send_call_function_ipi_mask(), it's harmless because
    validation test in generic_smp_call_function_interrupt() will take care
    of it.

    2) For cpu down issue, stop_machine() will guarantee that no concurrent
    smp_call_fuction() is processing.

    Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
    Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
    Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
    Cc: linux390@de.ibm.com
    Cc: linux-s390@vger.kernel.org
    ---
    arch/s390/kernel/smp.c | 2 --
    1 files changed, 0 insertions(+), 2 deletions(-)

    diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
    index 647ba94..14c8a08 100644
    --- a/arch/s390/kernel/smp.c
    +++ b/arch/s390/kernel/smp.c
    @@ -716,9 +716,7 @@ static void __cpuinit smp_start_secondary(void *cpuvoid)
    init_cpu_vtimer();
    pfault_init();
    notify_cpu_starting(smp_processor_id());
    - ipi_call_lock();
    set_cpu_online(smp_processor_id(), true);
    - ipi_call_unlock();
    local_irq_enable();
    /* cpu_idle will call schedule for us */
    cpu_idle();
    --
    1.7.5.4


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