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/export.h>
   9 #include <linux/sched.h>
  10
  11 #include <asm/mmu_context.h>
  12
  13 /*
  14  * use_mm
  15  *      Makes the calling kernel thread take on the specified
  16  *      mm context.
  17  *      Called by the retry thread execute retries within the
  18  *      iocb issuer's mm context, so that copy_from/to_user
  19  *      operations work seamlessly for aio.
  20  *      (Note: this routine is intended to be called only
  21  *      from a kernel thread context)
  22  */
  23 void use_mm(struct mm_struct *mm)
  24 {
  25         struct mm_struct *active_mm;
  26         struct task_struct *tsk = current;
  27
  28         task_lock(tsk);
  29         active_mm = tsk->active_mm;
  30         if (active_mm != mm) {
  31                 atomic_inc(&mm->mm_count);
  32                 tsk->active_mm = mm;
  33         }
  34         tsk->mm = mm;
  35         switch_mm(active_mm, mm, tsk);
  36         task_unlock(tsk);
  37
  38         if (active_mm != mm)
  39                 mmdrop(active_mm);
  40 }
  41 EXPORT_SYMBOL_GPL(use_mm);
  42
  43 /*
  44  * unuse_mm
  45  *      Reverses the effect of use_mm, i.e. releases the
  46  *      specified mm context which was earlier taken on
  47  *      by the calling kernel thread
  48  *      (Note: this routine is intended to be called only
  49  *      from a kernel thread context)
  50  */
  51 void unuse_mm(struct mm_struct *mm)
  52 {
  53         struct task_struct *tsk = current;
  54
  55         task_lock(tsk);
  56         sync_mm_rss(mm);
  57         tsk->mm = NULL;
  58         /* active_mm is still 'mm' */
  59         enter_lazy_tlb(mm, tsk);
  60         task_unlock(tsk);
  61 }
  62 EXPORT_SYMBOL_GPL(unuse_mm);