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    Subject[PATCH v6 36/46] m32r: 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: Hirokazu Takata <takata@linux-m32r.org>
    Cc: linux-m32r@ml.linux-m32r.org
    Cc: linux-m32r-ja@ml.linux-m32r.org
    Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
    ---

    arch/m32r/kernel/smp.c | 12 ++++++++----
    1 file changed, 8 insertions(+), 4 deletions(-)

    diff --git a/arch/m32r/kernel/smp.c b/arch/m32r/kernel/smp.c
    index ce7aea3..0dad4d7 100644
    --- a/arch/m32r/kernel/smp.c
    +++ b/arch/m32r/kernel/smp.c
    @@ -151,7 +151,7 @@ void smp_flush_cache_all(void)
    cpumask_t cpumask;
    unsigned long *mask;

    - preempt_disable();
    + get_online_cpus_atomic();
    cpumask_copy(&cpumask, cpu_online_mask);
    cpumask_clear_cpu(smp_processor_id(), &cpumask);
    spin_lock(&flushcache_lock);
    @@ -162,7 +162,7 @@ void smp_flush_cache_all(void)
    while (flushcache_cpumask)
    mb();
    spin_unlock(&flushcache_lock);
    - preempt_enable();
    + put_online_cpus_atomic();
    }

    void smp_flush_cache_all_interrupt(void)
    @@ -250,7 +250,7 @@ void smp_flush_tlb_mm(struct mm_struct *mm)
    unsigned long *mmc;
    unsigned long flags;

    - preempt_disable();
    + get_online_cpus_atomic();
    cpu_id = smp_processor_id();
    mmc = &mm->context[cpu_id];
    cpumask_copy(&cpu_mask, mm_cpumask(mm));
    @@ -268,7 +268,7 @@ void smp_flush_tlb_mm(struct mm_struct *mm)
    if (!cpumask_empty(&cpu_mask))
    flush_tlb_others(cpu_mask, mm, NULL, FLUSH_ALL);

    - preempt_enable();
    + put_online_cpus_atomic();
    }

    /*==========================================================================*
    @@ -715,10 +715,12 @@ static void send_IPI_allbutself(int ipi_num, int try)
    {
    cpumask_t cpumask;

    + get_online_cpus_atomic();
    cpumask_copy(&cpumask, cpu_online_mask);
    cpumask_clear_cpu(smp_processor_id(), &cpumask);

    send_IPI_mask(&cpumask, ipi_num, try);
    + put_online_cpus_atomic();
    }

    /*==========================================================================*
    @@ -750,6 +752,7 @@ static void send_IPI_mask(const struct cpumask *cpumask, int ipi_num, int try)
    if (num_cpus <= 1) /* NO MP */
    return;

    + get_online_cpus_atomic();
    cpumask_and(&tmp, cpumask, cpu_online_mask);
    BUG_ON(!cpumask_equal(cpumask, &tmp));

    @@ -760,6 +763,7 @@ static void send_IPI_mask(const struct cpumask *cpumask, int ipi_num, int try)
    }

    send_IPI_mask_phys(&physid_mask, ipi_num, try);
    + put_online_cpus_atomic();
    }

    /*==========================================================================*


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