path: root/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);

/*
 * Variables for shuffling.  The idea is to ensure that each CPU stays
 * idle for an extended period to test interactions with dyntick idle,
 * as well as interactions with any per-CPU varibles.
 */
struct shuffle_task {
	struct list_head st_l;
	struct task_struct *st_t;
};

static long shuffle_interval;	/* In jiffies. */
static struct task_struct *shuffler_task;
static cpumask_var_t shuffle_tmp_mask;
static int shuffle_idle_cpu;	/* Force all torture tasks off this CPU */
static struct list_head shuffle_task_list = LIST_HEAD_INIT(shuffle_task_list);
static DEFINE_MUTEX(shuffle_task_mutex);

/*
 * Register a task to be shuffled.  If there is no memory, just splat
 * and don't bother registering.
 */
void torture_shuffle_task_register(struct task_struct *tp)
{
	struct shuffle_task *stp;

	if (WARN_ON_ONCE(tp == NULL))
		return;
	stp = kmalloc(sizeof(*stp), GFP_KERNEL);
	if (WARN_ON_ONCE(stp == NULL))
		return;
	stp->st_t = tp;
	mutex_lock(&shuffle_task_mutex);
	list_add(&stp->st_l, &shuffle_task_list);
	mutex_unlock(&shuffle_task_mutex);
}
EXPORT_SYMBOL_GPL(torture_shuffle_task_register);

/*
 * Unregister all tasks, for example, at the end of the torture run.
 */
static void torture_shuffle_task_unregister_all(void)
{
	struct shuffle_task *stp;
	struct shuffle_task *p;

	mutex_lock(&shuffle_task_mutex);
	list_for_each_entry_safe(stp, p, &shuffle_task_list, st_l) {
		list_del(&stp->st_l);
		kfree(stp);
	}
	mutex_unlock(&shuffle_task_mutex);
}

/* Shuffle tasks such that we allow shuffle_idle_cpu to become idle.
 * A special case is when shuffle_idle_cpu = -1, in which case we allow
 * the tasks to run on all CPUs.
 */
static void torture_shuffle_tasks(void)
{
	struct shuffle_task *stp;

	cpumask_setall(shuffle_tmp_mask);
	get_online_cpus();

	/* No point in shuffling if there is only one online CPU (ex: UP) */
	if (num_online_cpus() == 1) {
		put_online_cpus();
		return;
	}

	/* Advance to the next CPU.  Upon overflow, don't idle any CPUs. */
	shuffle_idle_cpu = cpumask_next(shuffle_idle_cpu, shuffle_tmp_mask);
	if (shuffle_idle_cpu >= nr_cpu_ids)
		shuffle_idle_cpu = -1;
	if (shuffle_idle_cpu != -1) {
		cpumask_clear_cpu(shuffle_idle_cpu, shuffle_tmp_mask);
		if (cpumask_empty(shuffle_tmp_mask)) {
			put_online_cpus();
			return;
		}
	}

	mutex_lock(&shuffle_task_mutex);
	list_for_each_entry(stp, &shuffle_task_list, st_l)
		set_cpus_allowed_ptr(stp->st_t, shuffle_tmp_mask);
	mutex_unlock(&shuffle_task_mutex);

	put_online_cpus();
}

/* Shuffle tasks across CPUs, with the intent of allowing each CPU in the
 * system to become idle at a time and cut off its timer ticks. This is meant
 * to test the support for such tickless idle CPU in RCU.
 */
static int torture_shuffle(void *arg)
{
	VERBOSE_TOROUT_STRING("torture_shuffle task started");
	do {
		schedule_timeout_interruptible(shuffle_interval);
		torture_shuffle_tasks();
		torture_shutdown_absorb("torture_shuffle");
	} while (!torture_must_stop());
	VERBOSE_TOROUT_STRING("torture_shuffle task stopping");
	return 0;
}

/*
 * Start the shuffler, with shuffint in jiffies.
 */
int torture_shuffle_init(long shuffint)
{
	int ret;

	shuffle_interval = shuffint;

	shuffle_idle_cpu = -1;

	if (!alloc_cpumask_var(&shuffle_tmp_mask, GFP_KERNEL)) {
		VERBOSE_TOROUT_ERRSTRING("Failed to alloc mask");
		return -ENOMEM;
	}

	/* Create the shuffler thread */
	shuffler_task = kthread_run(torture_shuffle, NULL, "torture_shuffle");
	if (IS_ERR(shuffler_task)) {
		ret = PTR_ERR(shuffler_task);
		free_cpumask_var(shuffle_tmp_mask);
		VERBOSE_TOROUT_ERRSTRING("Failed to create shuffler");
		shuffler_task = NULL;
		return ret;
	}
	torture_shuffle_task_register(shuffler_task);
	return 0;
}
EXPORT_SYMBOL_GPL(torture_shuffle_init);

/*
 * Stop the shuffling.
 */
void torture_shuffle_cleanup(void)
{
	torture_shuffle_task_unregister_all();
	if (shuffler_task) {
		VERBOSE_TOROUT_STRING("Stopping torture_shuffle task");
		kthread_stop(shuffler_task);
		free_cpumask_var(shuffle_tmp_mask);
	}
	shuffler_task = NULL;
}
EXPORT_SYMBOL_GPL(torture_shuffle_cleanup);

/*
 * 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);