mmu_context.c revision 3d2d827f5ca5e32816194119d5c980c7e04474a6 
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 */
22void 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	atomic_inc(&mm->mm_count);
30	tsk->mm = mm;
31	tsk->active_mm = mm;
32	switch_mm(active_mm, mm, tsk);
33	task_unlock(tsk);
34
35	mmdrop(active_mm);
36}
37
38/*
39 * unuse_mm
40 *	Reverses the effect of use_mm, i.e. releases the
41 *	specified mm context which was earlier taken on
42 *	by the calling kernel thread
43 *	(Note: this routine is intended to be called only
44 *	from a kernel thread context)
45 */
46void unuse_mm(struct mm_struct *mm)
47{
48	struct task_struct *tsk = current;
49
50	task_lock(tsk);
51	tsk->mm = NULL;
52	/* active_mm is still 'mm' */
53	enter_lazy_tlb(mm, tsk);
54	task_unlock(tsk);
55}
56