gistfile1

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

#define THREAD_NUM 10
#define ARRAY_SIZE 100

pthread_rwlock_t lock = PTHREAD_RWLOCK_INITIALIZER;

struct data {
	size_t counter;
	size_t array[ARRAY_SIZE];
};

struct data *ptr[2];
struct data *ptr_writer;
struct data *ptr_collector;

void *writer_func(void *arg)
{
	size_t thread_num = (size_t)arg;

	while (1) {
		struct data *data_ptr;
		/* READ lock, write data */
		pthread_rwlock_rdlock(&lock);
		data_ptr = &ptr_writer[thread_num];
		if (data_ptr->counter < ARRAY_SIZE) {
			data_ptr->array[data_ptr->counter] = 1;              //<--------- write
			data_ptr->counter++;
		}
		pthread_rwlock_unlock(&lock);
		usleep(1000);
	}
}

void *collector_func(void *arg)
{
	struct data *tmp_ptr;
	int i, j;
	size_t num, sum;

	while (1) {
		/* WRITE lock, exchange and release */
		pthread_rwlock_wrlock(&lock);
		tmp_ptr = ptr_writer;
		ptr_writer = ptr_collector;
		ptr_collector = tmp_ptr;
		pthread_rwlock_unlock(&lock);

		num = sum = 0;
		for (i = 0; i < THREAD_NUM; i++) {
			num += ptr_collector[i].counter;
			for (j = 0; j < ptr_collector[i].counter; j ++) { //<----------- read
				sum += ptr_collector[i].array[j];             //<----------- read
			}
			ptr_collector[i].counter = 0;
		}
		printf("num: %zd, sum: %zd\n", num, sum);
		usleep(10000);
	}
}

int main() {
	pthread_t writers[THREAD_NUM];
	pthread_t collector;
	size_t i;

	ptr[0] = calloc(THREAD_NUM, sizeof(struct data));
	ptr[1] = calloc(THREAD_NUM, sizeof(struct data));

	ptr_writer = ptr[0];
	ptr_collector = ptr[1];

	pthread_create(&collector, NULL, collector_func, NULL);
	for (i = 0; i < THREAD_NUM; i++) {
		pthread_create(&writers[i], NULL, writer_func, (void *)i);
	}

	pthread_join(collector, NULL);
	return 0;
}