rwlock.c

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/* -*- C -*- */
/*
 * Copyright (c) 2011-2020 Seagate Technology LLC and/or its Affiliates
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * For any questions about this software or licensing,
 * please email opensource@seagate.com or cortx-questions@seagate.com.
 *
 */


#include "ut/ut.h"
#include "lib/thread.h"
#include "lib/rwlock.h"
#include "lib/assert.h"
#include "lib/semaphore.h"

enum {
        NR = 255,

        /*
         * Starvation tests.
         */

        /* A number of "starvers" acquiring and releasing the lock (in the
           required mode) in an infinite loop. */
        S = 8,
        /* A number of "checkers" which try to squeeze between starvers and
           acquire the lock in a different mode at least once. */
        C = 3
};

M0_BASSERT(S + C <= NR);

static int counter;
static struct m0_thread t[NR];
static struct m0_rwlock m;
static int sum;
static struct m0_semaphore p;
static struct m0_semaphore q;
static int stop;
static int i;

static void writer(int n)
{
        int i;

        for (i = 0; i < NR; ++i) {
                m0_rwlock_write_lock(&m);
                counter += n;
                m0_rwlock_write_unlock(&m);
        }
}

static void reader(int n)
{
        m0_rwlock_read_lock(&m);
        m0_semaphore_up(&p);
        m0_semaphore_down(&q);
        M0_UT_ASSERT(counter == 0);
        m0_rwlock_read_unlock(&m);
}

static void wstarver(int x)
{
        m0_rwlock_write_lock(&m);
        while (!stop) {
                m0_rwlock_write_unlock(&m);
                m0_rwlock_write_lock(&m);
        }
        m0_rwlock_write_unlock(&m);
}

static void rstarver(int x)
{
        m0_rwlock_read_lock(&m);
        while (!stop) {
                m0_rwlock_read_unlock(&m);
                m0_rwlock_read_lock(&m);
        }
        m0_rwlock_read_unlock(&m);
}


static void rcheck(int x)
{
        m0_rwlock_read_lock(&m);
        m0_rwlock_read_unlock(&m);
}

static void wcheck(int x)
{
        m0_rwlock_write_lock(&m);
        m0_rwlock_write_unlock(&m);
}

static void test_rw_writers(void)
{
        int result;

        counter = 0;

        for (sum = 0, i = 0; i < NR; ++i) {
                result = M0_THREAD_INIT(&t[i], int, NULL, &writer, i,
                                        "writer[%i]", i);
                M0_UT_ASSERT(result == 0);
                sum += i * NR;
        }

        for (i = 0; i < NR; ++i) {
                m0_thread_join(&t[i]);
                m0_thread_fini(&t[i]);
        }

        M0_UT_ASSERT(counter == sum);
}

static void test_rw_readers(void)
{
        int result;

        counter = 0;

        for (i = 0; i < NR; ++i) {
                result = M0_THREAD_INIT(&t[i], int, NULL, &reader, i,
                                        "reader[%i]", i);
                M0_UT_ASSERT(result == 0);
                m0_semaphore_down(&p);
        }

        for (i = 0; i < NR; ++i)
                m0_semaphore_up(&q);

        for (i = 0; i < NR; ++i) {
                m0_thread_join(&t[i]);
                m0_thread_fini(&t[i]);
        }
}

static void test_rw_excl(void)
{
        int result;

        for (i = 0; i < NR / 2; ++i) {
                result = M0_THREAD_INIT(&t[i], int, NULL, &reader, i,
                                        "reader[%i]", i);
                M0_UT_ASSERT(result == 0);
                m0_semaphore_down(&p);
        }

        for (sum = 0; i < NR; ++i) {
                result = M0_THREAD_INIT(&t[i], int, NULL, &writer, i,
                                        "writer[%i]", i);
                M0_UT_ASSERT(result == 0);
                sum += i * NR;
        }

        for (i = 0; i < NR / 2; ++i) {
                M0_UT_ASSERT(counter == 0);
                m0_semaphore_up(&q);
        }

        for (i = 0; i < NR; ++i) {
                m0_thread_join(&t[i]);
                m0_thread_fini(&t[i]);
        }
        M0_UT_ASSERT(counter == sum);
}

static void test_rw_rstarve(void)
{
        int result;

        stop = false;

        for (i = 0; i < S; ++i) {
                result = M0_THREAD_INIT(&t[i], int, NULL, &wstarver, 0,
                                        "wstarver[%i]", i);
                M0_UT_ASSERT(result == 0);
        }

        for (i = S; i < S + C; ++i) {
                result = M0_THREAD_INIT(&t[i], int, NULL, &rcheck, 0,
                                        "rcheck[%i]", i);
                M0_UT_ASSERT(result == 0);
        }

        for (i = S; i < S + C; ++i) {
                m0_thread_join(&t[i]);
                m0_thread_fini(&t[i]);
        }

        stop = true;

        for (i = 0; i < S; ++i) {
                m0_thread_join(&t[i]);
                m0_thread_fini(&t[i]);
        }
}

static void test_rw_wstarve(void)
{
        int result;

        for (i = 0; i < S; ++i) {
                result = M0_THREAD_INIT(&t[i], int, NULL, &rstarver, 0,
                                        "rstarver[%i]", i);
                M0_UT_ASSERT(result == 0);
        }

        for (i = S; i < S + C; ++i) {
                result = M0_THREAD_INIT(&t[i], int, NULL, &wcheck, 0,
                                        "wcheck[%i]", i);
                M0_UT_ASSERT(result == 0);
        }

        for (i = S; i < S + C; ++i) {
                m0_thread_join(&t[i]);
                m0_thread_fini(&t[i]);
        }

        stop = true;

        for (i = 0; i < S; ++i) {
                m0_thread_join(&t[i]);
                m0_thread_fini(&t[i]);
        }
}

void test_rw(void)
{
        m0_rwlock_init(&m);
        m0_semaphore_init(&p, 0);
        m0_semaphore_init(&q, 0);

        test_rw_writers();
        test_rw_readers();
        test_rw_excl();
        test_rw_rstarve();
        test_rw_wstarve();

        m0_semaphore_fini(&q);
        m0_semaphore_fini(&p);
        m0_rwlock_fini(&m);
}


/*
 *  Local variables:
 *  c-indentation-style: "K&R"
 *  c-basic-offset: 8
 *  tab-width: 8
 *  fill-column: 80
 *  scroll-step: 1
 *  End:
 */