alistair23-linux/kernel/torture.c

/*
 * Common functions for in-kernel torture tests.
 *
 * 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.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, you can access it online at
 * http://www.gnu.org/licenses/gpl-2.0.html.
 *
 * Copyright (C) IBM Corporation, 2014
 *
 * Author: Paul E. McKenney <paulmck@us.ibm.com>
 *	Based on kernel/rcu/torture.c.
 */
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/kthread.h>
#include <linux/err.h>
#include <linux/spinlock.h>
#include <linux/smp.h>
#include <linux/interrupt.h>
#include <linux/sched.h>
#include <linux/atomic.h>
#include <linux/bitops.h>
#include <linux/completion.h>
#include <linux/moduleparam.h>
#include <linux/percpu.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/freezer.h>
#include <linux/cpu.h>
#include <linux/delay.h>
#include <linux/stat.h>
#include <linux/slab.h>
#include <linux/trace_clock.h>
#include <asm/byteorder.h>
#include <linux/torture.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Paul E. McKenney <paulmck@us.ibm.com>");

int fullstop = FULLSTOP_RMMOD;
EXPORT_SYMBOL_GPL(fullstop);
DEFINE_MUTEX(fullstop_mutex);
EXPORT_SYMBOL_GPL(fullstop_mutex);

#define TORTURE_RANDOM_MULT	39916801  /* prime */
#define TORTURE_RANDOM_ADD	479001701 /* prime */
#define TORTURE_RANDOM_REFRESH	10000

/*
 * Crude but fast random-number generator.  Uses a linear congruential
 * generator, with occasional help from cpu_clock().
 */
unsigned long
torture_random(struct torture_random_state *trsp)
{
	if (--trsp->trs_count < 0) {
		trsp->trs_state += (unsigned long)local_clock();
		trsp->trs_count = TORTURE_RANDOM_REFRESH;
	}
	trsp->trs_state = trsp->trs_state * TORTURE_RANDOM_MULT +
		TORTURE_RANDOM_ADD;
	return swahw32(trsp->trs_state);
}
EXPORT_SYMBOL_GPL(torture_random);

/*
 * Absorb kthreads into a kernel function that won't return, so that
 * they won't ever access module text or data again.
 */
void torture_shutdown_absorb(const char *title)
{
	while (ACCESS_ONCE(fullstop) == FULLSTOP_SHUTDOWN) {
		pr_notice(
		       "torture thread %s parking due to system shutdown\n",
		       title);
		schedule_timeout_uninterruptible(MAX_SCHEDULE_TIMEOUT);
	}
}
EXPORT_SYMBOL_GPL(torture_shutdown_absorb);