/*
 * Copyright (c) 2014 Remy Noel.
 * Copyright (c) 2014 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 is a stress test for perfmon thread monitoring.
 * The goal is to pass through a maximum of code paths of the perfmon module.
 * We therefore try to get a high migration rate by schedueling at least as
 * many threads as CPUs.
 * Also, we stop and restart some threads along the way in order to check wether
 * stopped threads are propery handled.
 *
 * TODO: replace thread selection with a proper pseudo-random function once we
 * get one.
 */

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

#include <kern/error.h>
#include <kern/kmem.h>
#include <kern/panic.h>
#include <kern/perfmon.h>
#include <kern/thread.h>
#include <test/test.h>

enum test_thread_state {
    TEST_LAUNCHED = 0,
    TEST_RUNNING,
    TEST_STOPPING,
    TEST_STOPPED,
};

struct test_thread {
    struct thread *thread;
    struct perfmon_group *group;
    struct perfmon_event *event;

    bool monitored;
    enum test_thread_state state;
    unsigned long long count;
};

struct threads_stats {
    size_t num_group_start;
    size_t num_group_started;
    size_t num_thread_start;
    size_t num_thread_started;
};

static struct test_thread **test_threads;

static struct thread *test_control;

#define TEST_WAIT_INSTRUCT_COUNT 1000UL
#define TEST_NUM_LOOP_STATUS_PRINT 200000

static void
test_wait(void)
{
    volatile unsigned long i;

    /* TODO: Do something a a bit more clever once timers are here */

    for (i = 0; i < TEST_WAIT_INSTRUCT_COUNT; i++);
}

static void
test_thread_run(void *arg)
{
    struct test_thread *thread = arg;
    unsigned long num_loops;

    assert(thread->state == TEST_LAUNCHED);
    num_loops = 0;

    thread->state = TEST_RUNNING;

    for (;;) {
        barrier();
        if (thread->state == TEST_STOPPING) {
            break;
        }
        /* Invividual threads waits twice as much as control one in order to
         * induce some asynchronism between control and treads.
         */
        test_wait();
        test_wait();
        num_loops++;
    }
    thread->state = TEST_STOPPED;
}

static void
test_thread_toggle_monitor(struct test_thread *thread,
                           struct threads_stats *stats)
{
    int error;
    struct perfmon_group *group;

    group = thread->group;

    if (!thread->monitored) {
        error = perfmon_group_start(group);
        error_check(error, "perfmon_group_start");
        thread->monitored = true;
        stats->num_group_start++;
        stats->num_group_started++;
    } else {
        perfmon_group_update(group);
        thread->count = perfmon_event_read(thread->event);
        error = perfmon_group_stop(group);
        error_check(error, "perfmon_group_stop");
        thread->monitored = false;
        stats->num_group_started--;
    }
}

static int
test_thread_create_monitored_thread(struct thread **thread, size_t index,
                                    void *arg)
{
    struct thread_attr attr;
    char name[THREAD_NAME_SIZE];

    snprintf(name, sizeof(name), THREAD_KERNEL_PREFIX
             "test_monitored_thread:%zu", index);
    thread_attr_init(&attr, name);
    thread_attr_set_detached(&attr);

    return thread_create(thread, &attr, test_thread_run, arg);
}

static void
test_thread_toggle_state(size_t index,
                         struct threads_stats *stats)
{
    int error;
    struct perfmon_group *group;
    struct test_thread *thread;

    thread = test_threads[index];
    group = thread->group;

    switch (thread->state) {
    case TEST_RUNNING:
        thread->state = TEST_STOPPING;
        stats->num_thread_started--;
        break;
    case TEST_STOPPED:
        /* restart thread and attach it to the group of the previous thread.
         */
        if (thread->monitored) {
            test_thread_toggle_monitor(thread, stats);
        }
        error = perfmon_group_detach(group);
        error_check(error, "perfmon_group_detach");
        thread->state = TEST_LAUNCHED;
        error = test_thread_create_monitored_thread(&thread->thread, index,
                                                    thread);
        error_check(error, "thread_recreate monitored");
        error = perfmon_group_attach(group, thread->thread);
        error_check(error, "perfmon_group_attach");
        stats->num_thread_start++;
        stats->num_thread_started++;
        break;
    default:
        /* Do nothing if the thread is not in a stable state */
        break;
    }
}

static void
test_x15_test_control_run(void *arg)
{
    size_t selected_thread;
    size_t stopped_thread;
    struct test_thread *thread;
    size_t nr_threads;
    size_t loop_since_status;
    struct threads_stats stats;

    (void)arg;
    nr_threads = MAX(cpu_count() - 1, 1);
    selected_thread = 0;
    stopped_thread = 0;
    loop_since_status = 0;
    stats.num_group_start = 0;
    stats.num_group_started = 0;
    stats.num_thread_start = nr_threads;
    stats.num_thread_started = nr_threads;

    printf("monitoring %zu threads\n", nr_threads);

    for (;;) {
        /* Dummy `random` thread selection. */
        selected_thread = (selected_thread + 7) % nr_threads;
        thread = test_threads[selected_thread];
        test_thread_toggle_monitor(thread, &stats);

        /* only half of the threads may be stopped / restarted */
        stopped_thread = (stopped_thread + 11) % ((nr_threads  + 1) / 2);
        test_thread_toggle_state(stopped_thread, &stats);

        test_wait();
        if (!(++loop_since_status % TEST_NUM_LOOP_STATUS_PRINT)) {
            printf("===============================\n");
            printf("%zu groups started (%zu total)\n", stats.num_group_started,
                   stats.num_group_start);
            printf("%zu threads started (%zu total)\n",
                   stats.num_thread_started, stats.num_thread_start);
            printf("monitor value: ");
            for (size_t i = 0; i < nr_threads; i++) {
                printf("%zu: %llu, ", i, test_threads[i]->count);
            }
            printf("\n");
        }
    }
}

static struct test_thread *
test_thread_create(size_t index)
{
    struct test_thread *thread;
    int error;

    thread = kmem_zalloc(sizeof(*thread));

    if (thread == NULL) {
        panic("thread allocation failed");
    }

    error = test_thread_create_monitored_thread(&thread->thread, index, thread);
    error_check(error, "thread_create");
    error = perfmon_group_create(&thread->group);
    error_check(error, "perfmon_group_create");
    error = perfmon_event_create(&thread->event, PERFMON_ET_GENERIC,
                                 PERFMON_EV_CYCLE, PERFMON_EF_KERN);
    error_check(error, "perfmon_event_create");

    perfmon_group_add(thread->group, thread->event);
    error = perfmon_group_attach(thread->group, thread->thread);
    error_check(error, "perfmon_group_attach");

    return thread;
}

void
test_setup(void)
{
    struct thread_attr attr;
    size_t nr_threads;
    size_t i;
    int error;

    nr_threads = MAX(cpu_count() - 1, 1);

    test_threads = kmem_alloc(nr_threads * sizeof(*test_threads));
    for (i = 0; i < nr_threads; i++) {
        test_threads[i] =  test_thread_create(i);
    }

    thread_attr_init(&attr, "15_test_control_thread");
    thread_attr_set_detached(&attr);
    error = thread_create(&test_control, &attr, test_x15_test_control_run,
                          NULL);
    error_check(error, "thread_create control");
}