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    /* Copyright (C) 2009 Red Hat, Inc.
     *
     * See ../COPYING for licensing terms.
     */
    
    #include <linux/mm.h>
    #include <linux/sched.h>
    #include <linux/mmu_context.h>
    #include <linux/export.h>
    
    #include <asm/mmu_context.h>
    
    /*
     * use_mm
     *	Makes the calling kernel thread take on the specified
     *	mm context.
     *	(Note: this routine is intended to be called only
     *	from a kernel thread context)
     */
    void use_mm(struct mm_struct *mm)
    {
    	struct mm_struct *active_mm;
    	struct task_struct *tsk = current;
    
    	task_lock(tsk);
    	active_mm = tsk->active_mm;
    	if (active_mm != mm) {
    		atomic_inc(&mm->mm_count);
    		tsk->active_mm = mm;
    	}
    	tsk->mm = mm;
    	switch_mm(active_mm, mm, tsk);
    	task_unlock(tsk);
    #ifdef finish_arch_post_lock_switch
    	finish_arch_post_lock_switch();
    #endif
    
    	if (active_mm != mm)
    		mmdrop(active_mm);
    }
    EXPORT_SYMBOL_GPL(use_mm);
    
    /*
     * unuse_mm
     *	Reverses the effect of use_mm, i.e. releases the
     *	specified mm context which was earlier taken on
     *	by the calling kernel thread
     *	(Note: this routine is intended to be called only
     *	from a kernel thread context)
     */
    void unuse_mm(struct mm_struct *mm)
    {
    	struct task_struct *tsk = current;
    
    	task_lock(tsk);
    	sync_mm_rss(mm);
    	tsk->mm = NULL;
    	/* active_mm is still 'mm' */
    	enter_lazy_tlb(mm, tsk);
    	task_unlock(tsk);
    }
    EXPORT_SYMBOL_GPL(unuse_mm);