mm/mmu_context.c

   1 /* Copyright (C) 2009 Red Hat, Inc.
   2  *
   3  * See ../COPYING for licensing terms.
   4  */
   5
   6 #include <linux/mm.h>
   7 #include <linux/mmu_context.h>
   8 #include <linux/sched.h>
   9
  10 #include <asm/mmu_context.h>
  11
  12 /*
  13  * use_mm
  14  *      Makes the calling kernel thread take on the specified
  15  *      mm context.
  16  *      Called by the retry thread execute retries within the
  17  *      iocb issuer's mm context, so that copy_from/to_user
  18  *      operations work seamlessly for aio.
  19  *      (Note: this routine is intended to be called only
  20  *      from a kernel thread context)
  21  */
  22 void use_mm(struct mm_struct *mm)
  23 {
  24         struct mm_struct *active_mm;
  25         struct task_struct *tsk = current;
  26
  27         task_lock(tsk);
  28         active_mm = tsk->active_mm;
  29         if (active_mm != mm) {
  30                 atomic_inc(&mm->mm_count);
  31                 tsk->active_mm = mm;
  32         }
  33         tsk->mm = mm;
  34         switch_mm(active_mm, mm, tsk);
  35         task_unlock(tsk);
  36
  37         if (active_mm != mm)
  38                 mmdrop(active_mm);
  39 }
  40
  41 /*
  42  * unuse_mm
  43  *      Reverses the effect of use_mm, i.e. releases the
  44  *      specified mm context which was earlier taken on
  45  *      by the calling kernel thread
  46  *      (Note: this routine is intended to be called only
  47  *      from a kernel thread context)
  48  */
  49 void unuse_mm(struct mm_struct *mm)
  50 {
  51         struct task_struct *tsk = current;
  52
  53         task_lock(tsk);
  54         tsk->mm = NULL;
  55         /* active_mm is still 'mm' */
  56         enter_lazy_tlb(mm, tsk);
  57         task_unlock(tsk);
  58 }