mmu_context.c

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/* Copyright (C) 2009 Red Hat, Inc.
 *
 * See ../COPYING for licensing terms.
 */

#include <linux/mm.h>
#include <linux/mmu_context.h>
#include <linux/export.h>
#include <linux/sched.h>

#include <asm/mmu_context.h>

/*
 * use_mm
 *  Makes the calling kernel thread take on the specified
 *  mm context.
 *  Called by the retry thread execute retries within the
 *  iocb issuer's mm context, so that copy_from/to_user
 *  operations work seamlessly for aio.
 *  (Note: this routine is intended to be called only
 *  from a kernel thread context)
 */
void use_mm(struct mm_struct *mm)
{
    struct mm_struct *active_mm;
    struct task_struct *tsk = current;

    task_lock(tsk);
    active_mm = tsk->active_mm;
    if (active_mm != mm) {
        atomic_inc(&mm->mm_count);
        tsk->active_mm = mm;
    }
    tsk->mm = mm;
    switch_mm(active_mm, mm, tsk);
    task_unlock(tsk);

    if (active_mm != mm)
        mmdrop(active_mm);
}
EXPORT_SYMBOL_GPL(use_mm);

/*
 * unuse_mm
 *  Reverses the effect of use_mm, i.e. releases the
 *  specified mm context which was earlier taken on
 *  by the calling kernel thread
 *  (Note: this routine is intended to be called only
 *  from a kernel thread context)
 */
void unuse_mm(struct mm_struct *mm)
{
    struct task_struct *tsk = current;

    task_lock(tsk);
    sync_mm_rss(mm);
    tsk->mm = NULL;
    /* active_mm is still 'mm' */
    enter_lazy_tlb(mm, tsk);
    task_unlock(tsk);
}
EXPORT_SYMBOL_GPL(unuse_mm);