Root/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/module.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 */
23void 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}
41EXPORT_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 */
51void unuse_mm(struct mm_struct *mm)
52{
53    struct task_struct *tsk = current;
54
55    task_lock(tsk);
56    sync_mm_rss(tsk, mm);
57    tsk->mm = NULL;
58    /* active_mm is still 'mm' */
59    enter_lazy_tlb(mm, tsk);
60    task_unlock(tsk);
61}
62EXPORT_SYMBOL_GPL(unuse_mm);
63

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