text: #ifndef __PARISC_MMU_CONTEXT_H
  #define __PARISC_MMU_CONTEXT_H
  
  #include <linux/mm.h>
  #include <linux/sched.h>
  #include <asm/atomic.h>
  #include <asm/pgalloc.h>
  #include <asm/pgtable.h>
  #include <asm-generic/mm_hooks.h>
  
  static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
  {
  }
  
  /* on PA-RISC, we actually have enough contexts to justify an allocator
   * for them.  prumpf */
  
  extern unsigned long alloc_sid(void);
  extern void free_sid(unsigned long);
  
  static inline int
  init_new_context(struct task_struct *tsk, struct mm_struct *mm)
  {
  	BUG_ON(atomic_read(&mm->mm_users) != 1);
  
  	mm->context = alloc_sid();
  	return 0;
  }
  
  static inline void
  destroy_context(struct mm_struct *mm)
  {
  	free_sid(mm->context);
  	mm->context = 0;
  }
  
  static inline unsigned long __space_to_prot(mm_context_t context)
  {
  #if SPACEID_SHIFT == 0
  	return context << 1;
  #else
  	return context >> (SPACEID_SHIFT - 1);
  #endif
  }
  
  static inline void load_context(mm_context_t context)
  {
  	mtsp(context, 3);
  	mtctl(__space_to_prot(context), 8);
  }
  
  static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next, struct task_struct *tsk)
  {
  
  	if (prev != next) {
  		mtctl(__pa(next->pgd), 25);
  		load_context(next->context);
  	}
  }
  
  #define deactivate_mm(tsk,mm)	do { } while (0)
  
  static inline void activate_mm(struct mm_struct *prev, struct mm_struct *next)
  {
  	/*
  	 * Activate_mm is our one chance to allocate a space id
  	 * for a new mm created in the exec path. There's also
  	 * some lazy tlb stuff, which is currently dead code, but
  	 * we only allocate a space id if one hasn't been allocated
  	 * already, so we should be OK.
  	 */
  
  	BUG_ON(next == &init_mm); /* Should never happen */
  
  	if (next->context == 0)
  	    next->context = alloc_sid();
  
  	switch_mm(prev,next,current);
  }
  #endif
  