icswx_pid.c

Go to the documentation of this file.

/*
 *  ICSWX and ACOP/PID Management
 *
 *  Copyright (C) 2011 Anton Blanchard, IBM Corp. <[email protected]>
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; either version
 *  2 of the License, or (at your option) any later version.
 *
 */

#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/mm.h>
#include <linux/spinlock.h>
#include <linux/idr.h>
#include <linux/module.h>
#include "icswx.h"

#define COP_PID_MIN (COP_PID_NONE + 1)
#define COP_PID_MAX (0xFFFF)

static DEFINE_SPINLOCK(mmu_context_acop_lock);
static DEFINE_IDA(cop_ida);

static int new_cop_pid(struct ida *ida, int min_id, int max_id,
               spinlock_t *lock)
{
    int index;
    int err;

again:
    if (!ida_pre_get(ida, GFP_KERNEL))
        return -ENOMEM;

    spin_lock(lock);
    err = ida_get_new_above(ida, min_id, &index);
    spin_unlock(lock);

    if (err == -EAGAIN)
        goto again;
    else if (err)
        return err;

    if (index > max_id) {
        spin_lock(lock);
        ida_remove(ida, index);
        spin_unlock(lock);
        return -ENOMEM;
    }

    return index;
}

int get_cop_pid(struct mm_struct *mm)
{
    int pid;

    if (mm->context.cop_pid == COP_PID_NONE) {
        pid = new_cop_pid(&cop_ida, COP_PID_MIN, COP_PID_MAX,
                  &mmu_context_acop_lock);
        if (pid >= 0)
            mm->context.cop_pid = pid;
    }
    return mm->context.cop_pid;
}

int disable_cop_pid(struct mm_struct *mm)
{
    int free_pid = COP_PID_NONE;

    if ((!mm->context.acop) && (mm->context.cop_pid != COP_PID_NONE)) {
        free_pid = mm->context.cop_pid;
        mm->context.cop_pid = COP_PID_NONE;
    }
    return free_pid;
}

void free_cop_pid(int free_pid)
{
    spin_lock(&mmu_context_acop_lock);
    ida_remove(&cop_ida, free_pid);
    spin_unlock(&mmu_context_acop_lock);
}