test1.c

#include <errno.h>
#include <unistd.h>
#include <pthread.h>
#include <signal.h>


static pthread_t thr;
static pthread_mutex_t mtx1 = PTHREAD_MUTEX_INITIALIZER;
static pthread_cond_t cond1 = PTHREAD_COND_INITIALIZER;
static pthread_mutex_t mtx2 = PTHREAD_MUTEX_INITIALIZER;


#define print(s) write(2, s, sizeof(s) - 1);


void handler(int sig)
{
    print("HEY\n");
}

void *fn(void *arg)
{
    char buf[1];
    print("thread started\n");
    pthread_mutex_lock(&mtx2);
    pthread_cond_signal(&cond1);
    for (;;) {
        if (read(0, buf, sizeof(buf)) < 0) {
            if (errno == EINVAL) {
                break;
            }
        }
        print("read\n");
    }
}


int main()
{
    {
        struct sigaction act = {
            .sa_handler = handler,
            .sa_mask = SIGINT | SIGTERM,
            .sa_flags = SA_RESTART,
        };
        sigaction(SIGINT, &act, NULL);
    }
    pthread_create(&thr, NULL, fn, NULL);
    pthread_mutex_lock(&mtx1);
    pthread_cond_wait(&cond1, &mtx1);
    pthread_mutex_unlock(&mtx1);
    pthread_mutex_lock(&mtx2);
}

test2.c

#include <stdio.h>
#include <errno.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/ip.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <pthread.h>
#include <signal.h>


static pthread_t thr;
static pthread_mutex_t mtx1 = PTHREAD_MUTEX_INITIALIZER;
static pthread_cond_t cond1 = PTHREAD_COND_INITIALIZER;
static pthread_mutex_t mtx2 = PTHREAD_MUTEX_INITIALIZER;


#define print(s) write(2, s, sizeof(s) - 1);


void handler(int sig)
{
    print("HEY\n");
}

void *fn(void *arg)
{
    int s = *(int *)arg;
    char buf[1];
    print("thread started\n");
    pthread_mutex_lock(&mtx2);
    pthread_cond_signal(&cond1);
    for (;;) {
        if (read(s, buf, sizeof(buf)) < 0) {
            if (errno == EINVAL) {
                break;
            }
        }
        print("read\n");
    }
}


int main()
{
    {
        struct sigaction act = {
            .sa_handler = handler,
            .sa_mask = SIGINT | SIGTERM,
            .sa_flags = SA_RESTART,
        };
        sigaction(SIGINT, &act, NULL);
    }
    int s = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (s < 0) {
        perror("oops");
            return 1;
    }
    {
        struct sockaddr_in addr = {
            .sin_family = AF_INET,
            .sin_port = htons(12346),
            .sin_addr = htonl(0x7f000001),
        };
        if (connect(s, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
            perror("oops");
            return 1;
        }
    }
    pthread_create(&thr, NULL, fn, &s);
    pthread_mutex_lock(&mtx1);
    pthread_cond_wait(&cond1, &mtx1);
    pthread_mutex_unlock(&mtx1);
    pthread_mutex_lock(&mtx2);
    return 0;
}