/*
 * Copyright (c) 2017 Richard Braun.
 *
 * 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 3 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, see <http://www.gnu.org/licenses/>.
 *
 *
 * This module is a stress test of the weak reference implementation
 * of scalable reference counters. Two threads are created. The first
 * periodically allocates a page and initializes a counter inside the
 * page, then immediately decrements the counter. The intended effect
 * is to mark the counter as dying as soon as possible. The second
 * thread continually attempts to obtain a reference, i.e. increment
 * the counter, through a weak reference. Counters are regularly
 * printed to monitor activity. There should be almost as many noref
 * calls as there are iterations in the first thread (a bit lower
 * because of the review delay) and a good amount of revives (at least
 * on multiprocessor machines) caused by successfully getting the counter
 * from the weak reference while it is marked dying but still in review.
 * Iterations in the second thread may spike when obtaining a reference
 * fails, because the error case is much faster and continues until the
 * first thread reinitializes the weak reference.
 */

#include <stddef.h>
#include <stdio.h>

#include <kern/error.h>
#include <kern/init.h>
#include <kern/macros.h>
#include <kern/sref.h>
#include <kern/syscnt.h>
#include <kern/thread.h>
#include <test/test.h>
#include <vm/vm_kmem.h>

static struct sref_weakref test_weakref;

static void
test_noref(struct sref_counter *counter)
{
    vm_kmem_free(counter, sizeof(*counter));
}

static void
test_run(void *arg)
{
    struct sref_counter *counter;
    volatile unsigned long j;
    unsigned long i;

    (void)arg;

    for (i = 1; /* no condition */; i++) {
        counter = vm_kmem_alloc(sizeof(*counter));

        if (counter == NULL) {
            continue;
        }

        sref_counter_init(counter, 1, &test_weakref, test_noref);
        sref_counter_dec(counter);

        for (j = 0; j < 0x20000000; j++);

        printf("run: iterations: %lu\n", i);
        syscnt_info("sref_epoch");
        syscnt_info("sref_dirty_zero");
        syscnt_info("sref_revive");
        syscnt_info("sref_true_zero");
    }
}

static void
test_ref(void *arg)
{
    struct sref_counter *counter;
    unsigned long i;

    (void)arg;

    for (i = 1; /* no condition */; i++) {
        counter = sref_weakref_get(&test_weakref);

        if (counter != NULL) {
            sref_counter_dec(counter);
        }

        if ((i % 100000000) == 0) {
            printf("ref: iterations: %lu\n", i);
        }
    }
}

void __init
test_setup(void)
{
    struct thread_attr attr;
    struct thread *thread;
    int error;

    thread_attr_init(&attr, THREAD_KERNEL_PREFIX "test_run");
    thread_attr_set_detached(&attr);
    error = thread_create(&thread, &attr, test_run, NULL);
    error_check(error, "thread_create");

    thread_attr_init(&attr, THREAD_KERNEL_PREFIX "test_ref");
    thread_attr_set_detached(&attr);
    error = thread_create(&thread, &attr, test_ref, NULL);
    error_check(error, "thread_create");
}