/* rwsem-any.c: run some threads to do R/W semaphore tests
 *
 * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * 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/config.h>
#include <linux/module.h>
#include <linux/poll.h>
#include <linux/moduleparam.h>
#include <linux/stat.h>
#include <linux/init.h>
#include <asm/atomic.h>
#include <linux/personality.h>
#include <linux/smp_lock.h>
#include <linux/delay.h>
#include <linux/timer.h>
#include <linux/completion.h>
#include "check.h"

#define SCHED

static int numrd = 1, numwr = 1, numdg = 1, elapse = 5;

MODULE_AUTHOR("David Howells");
MODULE_DESCRIPTION("R/W semaphore test demo");
MODULE_LICENSE("GPL");

module_param(numrd, int, 0);
MODULE_PARM_DESC(numrd, "Number of reader threads");

module_param(numwr, int, 0);
MODULE_PARM_DESC(numwr, "Number of writer threads");

module_param(numdg, int, 0);
MODULE_PARM_DESC(numdg, "Number of downgrader threads");

module_param(elapse, int, 0);
MODULE_PARM_DESC(elapse, "Number of seconds to run for");

#ifdef SCHED
static int do_sched = 0;
module_param(do_sched, int, 0);
MODULE_PARM_DESC(numdg, "True if each thread should schedule regularly");
#endif

/* the semaphore under test */
static struct rw_semaphore rwsem_sem;


#ifdef DEBUG_RWSEM
extern struct rw_semaphore *rwsem_to_monitor;
#endif

static atomic_t readers = ATOMIC_INIT(0);
static atomic_t writers = ATOMIC_INIT(0);
static atomic_t do_stuff = ATOMIC_INIT(0);
static atomic_t reads_taken = ATOMIC_INIT(0);
static atomic_t writes_taken = ATOMIC_INIT(0);
static atomic_t downgrades_taken = ATOMIC_INIT(0);

static struct completion rd_comp[20], wr_comp[20], dg_comp[20];

static struct timer_list timer;

static inline void dr(void)
{
	down_read(&rwsem_sem);
	atomic_inc(&readers);
	atomic_inc(&reads_taken);
	CHECKA(writers, 0);
}

static inline void ur(void)
{
	CHECKA(writers, 0);
	atomic_dec(&readers);
	up_read(&rwsem_sem);
}

static inline void dw(void)
{
	down_write(&rwsem_sem);
	atomic_inc(&writers);
	atomic_inc(&writes_taken);
	CHECKA(writers, 1);
	CHECKA(readers, 0);
}

static inline void uw(void)
{
	CHECKA(writers, 1);
	CHECKA(readers, 0);
	atomic_dec(&writers);
	up_write(&rwsem_sem);
}

static inline void dgw(void)
{
	CHECKA(writers, 1);
	CHECKA(readers, 0);
	atomic_dec(&writers);
	atomic_inc(&readers);
	downgrade_write(&rwsem_sem);
	atomic_inc(&downgrades_taken);
}

static inline void sched(void)
{
#ifdef SCHED
	if (do_sched)
		schedule();
#endif
}

int reader(void *arg)
{
	unsigned int N = (unsigned long) arg;

	daemonize("Read%u", N);

	while (atomic_read(&do_stuff)) {
		dr();
		ur();
		sched();
	}

	printk("%s: done\n", current->comm);
	complete_and_exit(&rd_comp[N], 0);
}

int writer(void *arg)
{
	unsigned int N = (unsigned long) arg;

	daemonize("Write%u", N);

	while (atomic_read(&do_stuff)) {
		dw();
		uw();
		sched();
	}

	printk("%s: done\n", current->comm);
	complete_and_exit(&wr_comp[N], 0);
}

int downgrader(void *arg)
{
	unsigned int N = (unsigned long) arg;

	daemonize("Down%u", N);

	while (atomic_read(&do_stuff)) {
		dw();
		dgw();
		ur();
		sched();
	}

	printk("%s: done\n", current->comm);
	complete_and_exit(&dg_comp[N], 0);
}

static void stop_test(unsigned long dummy)
{
	atomic_set(&do_stuff, 0);
}

/*****************************************************************************/
/*
 *
 */
static int __init rwsem_init_module(void)
{
	unsigned long loop;

	printk("\nrwsem_any starting tests...\n");

	init_rwsem(&rwsem_sem);
	atomic_set(&do_stuff, 1);

#ifdef DEBUG_RWSEM
	rwsem_to_monitor = &rwsem_sem;
#endif

	/* kick off all the children */
	for (loop = 0; loop < 20; loop++) {
		if (loop < numrd) {
			init_completion(&rd_comp[loop]);
			kernel_thread(reader, (void *) loop, 0);
		}

		if (loop < numwr) {
			init_completion(&wr_comp[loop]);
			kernel_thread(writer, (void *) loop, 0);
		}

		if (loop < numdg) {
			init_completion(&dg_comp[loop]);
			kernel_thread(downgrader, (void *) loop, 0);
		}
	}

	/* set a stop timer */
	init_timer(&timer);
	timer.function = stop_test;
	timer.expires = jiffies + elapse * HZ;
	add_timer(&timer);

	/* now wait until it's all done */
	for (loop = 0; loop < numrd; loop++)
		wait_for_completion(&rd_comp[loop]);

	for (loop = 0; loop < numwr; loop++)
		wait_for_completion(&wr_comp[loop]);

	for (loop = 0; loop < numdg; loop++)
		wait_for_completion(&dg_comp[loop]);

	atomic_set(&do_stuff, 0);
	del_timer(&timer);

	/* print the results */
#ifdef CONFIG_RWSEM_XCHGADD_ALGORITHM
	printk("rwsem counter = %ld\n", rwsem_sem.count);
#else
	printk("rwsem counter = %d\n", rwsem_sem.activity);
#endif

	printk("reads taken: %d\n", atomic_read(&reads_taken));
	printk("writes taken: %d\n", atomic_read(&writes_taken));
	printk("downgrades taken: %d\n", atomic_read(&downgrades_taken));

#ifdef DEBUG_RWSEM
	rwsem_to_monitor = NULL;
#endif

	/* tell insmod to discard the module */
	return -ENOANO;
} /* end rwsem_init_module() */

module_init(rwsem_init_module);