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    Subject[PATCH v5 33/45] hexagon/smp: Use get/put_online_cpus_atomic() to prevent CPU offline
    Date
    Once stop_machine() is gone from the CPU offline path, we won't be able to
    depend on preempt_disable() or local_irq_disable() to prevent CPUs from
    going offline from under us.

    Use the get/put_online_cpus_atomic() APIs to prevent CPUs from going offline,
    while invoking from atomic context.

    Cc: Richard Kuo <rkuo@codeaurora.org>
    Cc: linux-hexagon@vger.kernel.org
    Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
    ---

    arch/hexagon/kernel/smp.c | 5 +++++
    1 file changed, 5 insertions(+)

    diff --git a/arch/hexagon/kernel/smp.c b/arch/hexagon/kernel/smp.c
    index 8e095df..ec87de9 100644
    --- a/arch/hexagon/kernel/smp.c
    +++ b/arch/hexagon/kernel/smp.c
    @@ -112,6 +112,7 @@ void send_ipi(const struct cpumask *cpumask, enum ipi_message_type msg)
    unsigned long cpu;
    unsigned long retval;

    + get_online_cpus_atomic();
    local_irq_save(flags);

    for_each_cpu(cpu, cpumask) {
    @@ -128,6 +129,7 @@ void send_ipi(const struct cpumask *cpumask, enum ipi_message_type msg)
    }

    local_irq_restore(flags);
    + put_online_cpus_atomic();
    }

    static struct irqaction ipi_intdesc = {
    @@ -241,9 +243,12 @@ void smp_send_reschedule(int cpu)
    void smp_send_stop(void)
    {
    struct cpumask targets;
    +
    + get_online_cpus_atomic();
    cpumask_copy(&targets, cpu_online_mask);
    cpumask_clear_cpu(smp_processor_id(), &targets);
    send_ipi(&targets, IPI_CPU_STOP);
    + put_online_cpus_atomic();
    }

    void arch_send_call_function_single_ipi(int cpu)


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