thread pool

threadpool.c

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <unistd.h>

typedef struct tid {
    int n;
    pthread_t *thread;
} tid_t;

typedef struct flag {
    void *(*func)(void *);
    void *param;
} flag_t;

int max;

flag_t **flags;    // flags[スレッドID]に関数ポインタが入っていれば，そのプロセスが関数を実行する
tid_t **queue;    // 暇なスレッド

int head;
int tail;

void *loop(void *param)
{
    int boolean;
    tid_t *self = (tid_t *)param;

    int n = self->n;
    flag_t *flag;
    int _tail;

    pthread_detach(*(self->thread));
    
    while(1) {
        if(flags[n] != (flag_t *)0) {
            flag = flags[n];
            flags[n] = 0;
            (flag->func)(flag->param);

            free(flag);

            // tailを動かす
            do {
                _tail = tail;

                if(tail == max - 1) {
                    boolean = __sync_bool_compare_and_swap(&tail, _tail, 0);
                } else {
                    boolean = __sync_bool_compare_and_swap(&tail, _tail, _tail + 1);
                }
            } while(!boolean);

            queue[_tail + 1] = self;
        }
    }
}

int tp_init(int m)
{
    int i;

    max = m;
    flags = (flag_t **)malloc(sizeof(flag_t *) * m);
    queue = (tid_t **)malloc(sizeof(int) * m);
    head = 0;
    tail = m - 1;

    for(i = 0; i < m; i++) {
        tid_t *p = (tid_t *)malloc(sizeof(tid_t));
        pthread_t *thread = (pthread_t *)malloc(sizeof(pthread_t));

        p->n = i;
        p->thread = thread;

        if(pthread_create(thread, NULL, loop, (void *)p) != 0) {
            perror("pthread_create()");
            return 0;
        }

        flags[i] = 0;
        queue[i] = p;
    }

    return 1;
}

int tp_create(void *(*func)(void *), void *param)
{
    flag_t *flag = (flag_t *)malloc(sizeof(flag_t));

    tid_t *p = queue[head];
    int free_thread_n = p->n;

    head++;

    // TODO: head == tailだったときの処理

    flag->func = func;
    flag->param = param;
    flags[free_thread_n] = flag;

    return 1;
}

void *test(void *param)
{
    printf("hello, world\n");
    return NULL;
}

int main()
{
    tp_init(30);
    tp_create(test, NULL);
    tp_create(test, NULL);
    tp_create(test, NULL);
    tp_create(test, NULL);
    tp_create(test, NULL);
    tp_create(test, NULL);
    tp_create(test, NULL);
    tp_create(test, NULL);
    tp_create(test, NULL);
    tp_create(test, NULL);
    tp_create(test, NULL);

    sleep(3);
    return 0;
}