arch/powerpc/mm/icswx_pid.c

/*
 *  ICSWX and ACOP/PID Management
 *
 *  Copyright (C) 2011 Anton Blanchard, IBM Corp. <anton@samba.org>
 *
 *  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);
}