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    Subject[PATCH 4/9] sh: Use clear_tasks_mm_cpumask()
    Checking for process->mm is not enough because process' main
    thread may exit or detach its mm via use_mm(), but other threads
    may still have a valid mm.

    To fix this we would need to use find_lock_task_mm(), which would
    walk up all threads and returns an appropriate task (with task
    lock held).

    clear_tasks_mm_cpumask() has the issue fixed, so let's use it.

    Suggested-by: Oleg Nesterov <oleg@redhat.com>
    Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
    ---
    arch/sh/kernel/smp.c | 7 +------
    1 file changed, 1 insertion(+), 6 deletions(-)

    diff --git a/arch/sh/kernel/smp.c b/arch/sh/kernel/smp.c
    index eaebdf6..4664f76 100644
    --- a/arch/sh/kernel/smp.c
    +++ b/arch/sh/kernel/smp.c
    @@ -123,7 +123,6 @@ void native_play_dead(void)
    int __cpu_disable(void)
    {
    unsigned int cpu = smp_processor_id();
    - struct task_struct *p;
    int ret;

    ret = mp_ops->cpu_disable(cpu);
    @@ -153,11 +152,7 @@ int __cpu_disable(void)
    flush_cache_all();
    local_flush_tlb_all();

    - read_lock(&tasklist_lock);
    - for_each_process(p)
    - if (p->mm)
    - cpumask_clear_cpu(cpu, mm_cpumask(p->mm));
    - read_unlock(&tasklist_lock);
    + clear_tasks_mm_cpumask(cpu);

    return 0;
    }
    --
    1.7.9.2


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