/*
 * Module-based torture test facility for locking
 *
 * 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>");

torture_param(int, nwriters_stress, -1,
             "Number of write-locking stress-test threads");
torture_param(int, onoff_holdoff, 0, "Time after boot before CPU hotplugs (s)");
torture_param(int, onoff_interval, 0,
             "Time between CPU hotplugs (s), 0=disable");
torture_param(int, shuffle_interval, 3,
             "Number of jiffies between shuffles, 0=disable");
torture_param(int, shutdown_secs, 0, "Shutdown time (j), <= zero to disable.");
torture_param(int, stat_interval, 60,
             "Number of seconds between stats printk()s");
torture_param(int, stutter, 5, "Number of jiffies to run/halt test, 0=disable");
torture_param(bool, verbose, true,
             "Enable verbose debugging printk()s");

static char *torture_type = "spin_lock";
module_param(torture_type, charp, 0444);
MODULE_PARM_DESC(torture_type,
                 "Type of lock to torture (spin_lock, spin_lock_irq, ...)");

static atomic_t n_lock_torture_errors;

static struct task_struct *stats_task;
static struct task_struct **writer_tasks;

static int nrealwriters_stress;
static bool lock_is_write_held;

struct lock_writer_stress_stats {
        long n_write_lock_fail;
        long n_write_lock_acquired;
};
static struct lock_writer_stress_stats *lwsa;

#if defined(MODULE)
#define LOCKTORTURE_RUNNABLE_INIT 1
#else
#define LOCKTORTURE_RUNNABLE_INIT 0
#endif
int locktorture_runnable = LOCKTORTURE_RUNNABLE_INIT;
module_param(locktorture_runnable, int, 0444);
MODULE_PARM_DESC(locktorture_runnable, "Start locktorture at module init");

/* Forward reference. */
static void lock_torture_cleanup(void);

/*
 * Operations vector for selecting different types of tests.
 */
struct lock_torture_ops {
        void (*init)(void);
        int (*writelock)(void);
        void (*write_delay)(struct torture_random_state *trsp);
        void (*writeunlock)(void);
        unsigned long flags;
        const char *name;
};

static struct lock_torture_ops *cur_ops;

/*
 * Definitions for lock torture testing.
 */

static int torture_lock_busted_write_lock(void)
{
        return 0;  /* BUGGY, do not use in real life!!! */
}

static void torture_lock_busted_write_delay(struct torture_random_state *trsp)
{
        const unsigned long longdelay_us = 100;

        /* We want a long delay occasionally to force massive contention.  */
        if (!(torture_random(trsp) %
              (nrealwriters_stress * 2000 * longdelay_us)))
                mdelay(longdelay_us);
#ifdef CONFIG_PREEMPT
        if (!(torture_random(trsp) % (nrealwriters_stress * 20000)))
                preempt_schedule();  /* Allow test to be preempted. */
#endif
}

static void torture_lock_busted_write_unlock(void)
{
          /* BUGGY, do not use in real life!!! */
}

static struct lock_torture_ops lock_busted_ops = {
        .writelock      = torture_lock_busted_write_lock,
        .write_delay    = torture_lock_busted_write_delay,
        .writeunlock    = torture_lock_busted_write_unlock,
        .name           = "lock_busted"
};

static DEFINE_SPINLOCK(torture_spinlock);

static int torture_spin_lock_write_lock(void) __acquires(torture_spinlock)
{
        spin_lock(&torture_spinlock);
        return 0;
}

static void torture_spin_lock_write_delay(struct torture_random_state *trsp)
{
        const unsigned long shortdelay_us = 2;
        const unsigned long longdelay_us = 100;

        /* We want a short delay mostly to emulate likely code, and
         * we want a long delay occasionally to force massive contention.
         */
        if (!(torture_random(trsp) %
              (nrealwriters_stress * 2000 * longdelay_us)))
                mdelay(longdelay_us);
        if (!(torture_random(trsp) %
              (nrealwriters_stress * 2 * shortdelay_us)))
                udelay(shortdelay_us);
#ifdef CONFIG_PREEMPT
        if (!(torture_random(trsp) % (nrealwriters_stress * 20000)))
                preempt_schedule();  /* Allow test to be preempted. */
#endif
}

static void torture_spin_lock_write_unlock(void) __releases(torture_spinlock)
{
        spin_unlock(&torture_spinlock);
}

static struct lock_torture_ops spin_lock_ops = {
        .writelock      = torture_spin_lock_write_lock,
        .write_delay    = torture_spin_lock_write_delay,
        .writeunlock    = torture_spin_lock_write_unlock,
        .name           = "spin_lock"
};

static int torture_spin_lock_write_lock_irq(void)
__acquires(torture_spinlock_irq)
{
        unsigned long flags;

        spin_lock_irqsave(&torture_spinlock, flags);
        cur_ops->flags = flags;
        return 0;
}

static void torture_lock_spin_write_unlock_irq(void)
__releases(torture_spinlock)
{
        spin_unlock_irqrestore(&torture_spinlock, cur_ops->flags);
}

static struct lock_torture_ops spin_lock_irq_ops = {
        .writelock      = torture_spin_lock_write_lock_irq,
        .write_delay    = torture_spin_lock_write_delay,
        .writeunlock    = torture_lock_spin_write_unlock_irq,
        .name           = "spin_lock_irq"
};

/*
 * Lock torture writer kthread.  Repeatedly acquires and releases
 * the lock, checking for duplicate acquisitions.
 */
static int lock_torture_writer(void *arg)
{
        struct lock_writer_stress_stats *lwsp = arg;
        static DEFINE_TORTURE_RANDOM(rand);

        VERBOSE_TOROUT_STRING("lock_torture_writer task started");
        set_user_nice(current, MAX_NICE);

        do {
                if ((torture_random(&rand) & 0xfffff) == 0)
                        schedule_timeout_uninterruptible(1);
                cur_ops->writelock();
                if (WARN_ON_ONCE(lock_is_write_held))
                        lwsp->n_write_lock_fail++;
                lock_is_write_held = 1;
                lwsp->n_write_lock_acquired++;
                cur_ops->write_delay(&rand);
                lock_is_write_held = 0;
                cur_ops->writeunlock();
                stutter_wait("lock_torture_writer");
        } while (!torture_must_stop());
        torture_kthread_stopping("lock_torture_writer");
        return 0;
}

/*
 * Create an lock-torture-statistics message in the specified buffer.
 */
static void lock_torture_printk(char *page)
{
        bool fail = 0;
        int i;
        long max = 0;
        long min = lwsa[0].n_write_lock_acquired;
        long long sum = 0;

        for (i = 0; i < nrealwriters_stress; i++) {
                if (lwsa[i].n_write_lock_fail)
                        fail = true;
                sum += lwsa[i].n_write_lock_acquired;
                if (max < lwsa[i].n_write_lock_fail)
                        max = lwsa[i].n_write_lock_fail;
                if (min > lwsa[i].n_write_lock_fail)
                        min = lwsa[i].n_write_lock_fail;
        }
        page += sprintf(page, "%s%s ", torture_type, TORTURE_FLAG);
        page += sprintf(page,
                        "Writes:  Total: %lld  Max/Min: %ld/%ld %s  Fail: %d %s\n",
                        sum, max, min, max / 2 > min ? "???" : "",
                        fail, fail ? "!!!" : "");
        if (fail)
                atomic_inc(&n_lock_torture_errors);
}

/*
 * Print torture statistics.  Caller must ensure that there is only one
 * call to this function at a given time!!!  This is normally accomplished
 * by relying on the module system to only have one copy of the module
 * loaded, and then by giving the lock_torture_stats kthread full control
 * (or the init/cleanup functions when lock_torture_stats thread is not
 * running).
 */
static void lock_torture_stats_print(void)
{
        int size = nrealwriters_stress * 200 + 8192;
        char *buf;

        buf = kmalloc(size, GFP_KERNEL);
        if (!buf) {
                pr_err("lock_torture_stats_print: Out of memory, need: %d",
                       size);
                return;
        }
        lock_torture_printk(buf);
        pr_alert("%s", buf);
        kfree(buf);
}

/*
 * Periodically prints torture statistics, if periodic statistics printing
 * was specified via the stat_interval module parameter.
 *
 * No need to worry about fullstop here, since this one doesn't reference
 * volatile state or register callbacks.
 */
static int lock_torture_stats(void *arg)
{
        VERBOSE_TOROUT_STRING("lock_torture_stats task started");
        do {
                schedule_timeout_interruptible(stat_interval * HZ);
                lock_torture_stats_print();
                torture_shutdown_absorb("lock_torture_stats");
        } while (!torture_must_stop());
        torture_kthread_stopping("lock_torture_stats");
        return 0;
}

static inline void
lock_torture_print_module_parms(struct lock_torture_ops *cur_ops,
                                const char *tag)
{
        pr_alert("%s" TORTURE_FLAG
                 "--- %s: nwriters_stress=%d stat_interval=%d verbose=%d shuffle_interval=%d stutter=%d shutdown_secs=%d onoff_interval=%d onoff_holdoff=%d\n",
                 torture_type, tag, nrealwriters_stress, stat_interval, verbose,
                 shuffle_interval, stutter, shutdown_secs,
                 onoff_interval, onoff_holdoff);
}

static void lock_torture_cleanup(void)
{
        int i;

        if (torture_cleanup())
                return;

        if (writer_tasks) {
                for (i = 0; i < nrealwriters_stress; i++)
                        torture_stop_kthread(lock_torture_writer,
                                             writer_tasks[i]);
                kfree(writer_tasks);
                writer_tasks = NULL;
        }

        torture_stop_kthread(lock_torture_stats, stats_task);
        lock_torture_stats_print();  /* -After- the stats thread is stopped! */

        if (atomic_read(&n_lock_torture_errors))
                lock_torture_print_module_parms(cur_ops,
                                                "End of test: FAILURE");
        else if (torture_onoff_failures())
                lock_torture_print_module_parms(cur_ops,
                                                "End of test: LOCK_HOTPLUG");
        else
                lock_torture_print_module_parms(cur_ops,
                                                "End of test: SUCCESS");
}

static int __init lock_torture_init(void)
{
        int i;
        int firsterr = 0;
        static struct lock_torture_ops *torture_ops[] = {
                &lock_busted_ops, &spin_lock_ops, &spin_lock_irq_ops,
        };

        if (!torture_init_begin(torture_type, verbose, &locktorture_runnable))
                return -EBUSY;

        /* Process args and tell the world that the torturer is on the job. */
        for (i = 0; i < ARRAY_SIZE(torture_ops); i++) {
                cur_ops = torture_ops[i];
                if (strcmp(torture_type, cur_ops->name) == 0)
                        break;
        }
        if (i == ARRAY_SIZE(torture_ops)) {
                pr_alert("lock-torture: invalid torture type: \"%s\"\n",
                         torture_type);
                pr_alert("lock-torture types:");
                for (i = 0; i < ARRAY_SIZE(torture_ops); i++)
                        pr_alert(" %s", torture_ops[i]->name);
                pr_alert("\n");
                torture_init_end();
                return -EINVAL;
        }
        if (cur_ops->init)
                cur_ops->init(); /* no "goto unwind" prior to this point!!! */

        if (nwriters_stress >= 0)
                nrealwriters_stress = nwriters_stress;
        else
                nrealwriters_stress = 2 * num_online_cpus();
        lock_torture_print_module_parms(cur_ops, "Start of test");

        /* Initialize the statistics so that each run gets its own numbers. */

        lock_is_write_held = 0;
        lwsa = kmalloc(sizeof(*lwsa) * nrealwriters_stress, GFP_KERNEL);
        if (lwsa == NULL) {
                VERBOSE_TOROUT_STRING("lwsa: Out of memory");
                firsterr = -ENOMEM;
                goto unwind;
        }
        for (i = 0; i < nrealwriters_stress; i++) {
                lwsa[i].n_write_lock_fail = 0;
                lwsa[i].n_write_lock_acquired = 0;
        }

        /* Start up the kthreads. */

        if (onoff_interval > 0) {
                firsterr = torture_onoff_init(onoff_holdoff * HZ,
                                              onoff_interval * HZ);
                if (firsterr)
                        goto unwind;
        }
        if (shuffle_interval > 0) {
                firsterr = torture_shuffle_init(shuffle_interval);
                if (firsterr)
                        goto unwind;
        }
        if (shutdown_secs > 0) {
                firsterr = torture_shutdown_init(shutdown_secs,
                                                 lock_torture_cleanup);
                if (firsterr)
                        goto unwind;
        }
        if (stutter > 0) {
                firsterr = torture_stutter_init(stutter);
                if (firsterr)
                        goto unwind;
        }

        writer_tasks = kzalloc(nrealwriters_stress * sizeof(writer_tasks[0]),
                               GFP_KERNEL);
        if (writer_tasks == NULL) {
                VERBOSE_TOROUT_ERRSTRING("writer_tasks: Out of memory");
                firsterr = -ENOMEM;
                goto unwind;
        }
        for (i = 0; i < nrealwriters_stress; i++) {
                firsterr = torture_create_kthread(lock_torture_writer, &lwsa[i],
                                                  writer_tasks[i]);
                if (firsterr)
                        goto unwind;
        }
        if (stat_interval > 0) {
                firsterr = torture_create_kthread(lock_torture_stats, NULL,
                                                  stats_task);
                if (firsterr)
                        goto unwind;
        }
        torture_init_end();
        return 0;

unwind:
        torture_init_end();
        lock_torture_cleanup();
        return firsterr;
}

module_init(lock_torture_init);
module_exit(lock_torture_cleanup);