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    Subject[PATCH v6 41/46] sh: 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: Paul Mundt <lethal@linux-sh.org>
    Cc: linux-sh@vger.kernel.org
    Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
    ---

    arch/sh/kernel/smp.c | 12 ++++++------
    1 file changed, 6 insertions(+), 6 deletions(-)

    diff --git a/arch/sh/kernel/smp.c b/arch/sh/kernel/smp.c
    index 2062aa8..232fabe 100644
    --- a/arch/sh/kernel/smp.c
    +++ b/arch/sh/kernel/smp.c
    @@ -357,7 +357,7 @@ static void flush_tlb_mm_ipi(void *mm)
    */
    void flush_tlb_mm(struct mm_struct *mm)
    {
    - preempt_disable();
    + get_online_cpus_atomic();

    if ((atomic_read(&mm->mm_users) != 1) || (current->mm != mm)) {
    smp_call_function(flush_tlb_mm_ipi, (void *)mm, 1);
    @@ -369,7 +369,7 @@ void flush_tlb_mm(struct mm_struct *mm)
    }
    local_flush_tlb_mm(mm);

    - preempt_enable();
    + put_online_cpus_atomic();
    }

    struct flush_tlb_data {
    @@ -390,7 +390,7 @@ void flush_tlb_range(struct vm_area_struct *vma,
    {
    struct mm_struct *mm = vma->vm_mm;

    - preempt_disable();
    + get_online_cpus_atomic();
    if ((atomic_read(&mm->mm_users) != 1) || (current->mm != mm)) {
    struct flush_tlb_data fd;

    @@ -405,7 +405,7 @@ void flush_tlb_range(struct vm_area_struct *vma,
    cpu_context(i, mm) = 0;
    }
    local_flush_tlb_range(vma, start, end);
    - preempt_enable();
    + put_online_cpus_atomic();
    }

    static void flush_tlb_kernel_range_ipi(void *info)
    @@ -433,7 +433,7 @@ static void flush_tlb_page_ipi(void *info)

    void flush_tlb_page(struct vm_area_struct *vma, unsigned long page)
    {
    - preempt_disable();
    + get_online_cpus_atomic();
    if ((atomic_read(&vma->vm_mm->mm_users) != 1) ||
    (current->mm != vma->vm_mm)) {
    struct flush_tlb_data fd;
    @@ -448,7 +448,7 @@ void flush_tlb_page(struct vm_area_struct *vma, unsigned long page)
    cpu_context(i, vma->vm_mm) = 0;
    }
    local_flush_tlb_page(vma, page);
    - preempt_enable();
    + put_online_cpus_atomic();
    }

    static void flush_tlb_one_ipi(void *info)


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