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    Subject[RFC PATCH 09/10] POWERPC: 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: Benjamin Herrenschmidt <benh@kernel.crashing.org>
    Cc: Paul Mackerras <paulus@samba.org>
    Cc: linuxppc-dev@lists.ozlabs.org
    ---
    arch/powerpc/kernel/smp.c | 2 --
    1 files changed, 0 insertions(+), 2 deletions(-)

    diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
    index e4cb343..e1417c4 100644
    --- a/arch/powerpc/kernel/smp.c
    +++ b/arch/powerpc/kernel/smp.c
    @@ -571,7 +571,6 @@ void __devinit start_secondary(void *unused)
    if (system_state == SYSTEM_RUNNING)
    vdso_data->processorCount++;
    #endif
    - ipi_call_lock();
    notify_cpu_starting(cpu);
    set_cpu_online(cpu, true);
    /* Update sibling maps */
    @@ -601,7 +600,6 @@ void __devinit start_secondary(void *unused)
    of_node_put(np);
    }
    of_node_put(l2_cache);
    - ipi_call_unlock();

    local_irq_enable();

    --
    1.7.5.4


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