linux 异步信号的同步处理方式

     rlen = recv(sock_fd, buf, len, MSG_WAITALL); 
     if ((rlen == -1) && (errno == EINTR)){
         // this kind of error is recoverable, we can set the offset change 
         //‘rlen’ as 0 and continue to recv
     }

#include <signal.h>
#include <errno.h>
#include <pthread.h>
#include <unistd.h>
#include <sys/types.h>

void sig_handler(int signum)
{
    printf("Receive signal. %d\n", signum);
}

void* sigmgr_thread()
{
    sigset_t   waitset, oset;
    int        sig;
    int        rc;
    pthread_t  ppid = pthread_self();

    pthread_detach(ppid);

    sigemptyset(&waitset);
    sigaddset(&waitset, SIGRTMIN);
    sigaddset(&waitset, SIGRTMIN+2);
    sigaddset(&waitset, SIGRTMAX);
    sigaddset(&waitset, SIGUSR1);
    sigaddset(&waitset, SIGUSR2);

    while (1)  {
        rc = sigwait(&waitset, &sig);
        if (rc != -1) {
            sig_handler(sig);
        } else {
            printf("sigwaitinfo() returned err: %d; %s\n", errno, strerror(errno));
        }
    }
}


int main()
{
    sigset_t bset, oset;
    int             i;
    pid_t           pid = getpid();
    pthread_t       ppid;

    sigemptyset(&bset);
    sigaddset(&bset, SIGRTMIN);
    sigaddset(&bset, SIGRTMIN+2);
    sigaddset(&bset, SIGRTMAX);
    sigaddset(&bset, SIGUSR1);
    sigaddset(&bset, SIGUSR2);

    if (pthread_sigmask(SIG_BLOCK, &bset, &oset) != 0)
        printf("!! Set pthread mask failed\n");

    kill(pid, SIGRTMAX);
    kill(pid, SIGRTMAX);
    kill(pid, SIGRTMIN+2);
    kill(pid, SIGRTMIN);
    kill(pid, SIGRTMIN+2);
    kill(pid, SIGRTMIN);
    kill(pid, SIGUSR2);
    kill(pid, SIGUSR2);
    kill(pid, SIGUSR1);
kill(pid, SIGUSR1);

    // Create the dedicated thread sigmgr_thread() which will handle signals synchronously
    pthread_create(&ppid, NULL, sigmgr_thread, NULL);

    sleep(10);

    exit (0);
}

#include <signal.h>
#include <errno.h>
#include <pthread.h>
#include <unistd.h>
#include <sys/types.h>
 
void sig_handler(int signum)
{
    static int j = 0;
    static int k = 0;
    pthread_t  sig_ppid = pthread_self(); 
    // used to show which thread the signal is handled in.
   
    if (signum == SIGUSR1) {
        printf("thread %d, receive SIGUSR1 No. %d\n", sig_ppid, j);
        j++;
    //SIGRTMIN should not be considered constants from userland, 
    //there is compile error when use switch case
    } else if (signum == SIGRTMIN) {
        printf("thread %d, receive SIGRTMIN No. %d\n", sig_ppid, k);
        k++;
    }
}

void* worker_thread()
{
    pthread_t  ppid = pthread_self();
    pthread_detach(ppid);
    while (1) {
        printf("I‘m thread %d, I‘m alive\n", ppid);
        sleep(10);
    }
}

void* sigmgr_thread()
{
    sigset_t   waitset, oset;
    siginfo_t  info;
    int        rc;
    pthread_t  ppid = pthread_self();

    pthread_detach(ppid);

    sigemptyset(&waitset);
    sigaddset(&waitset, SIGRTMIN);
    sigaddset(&waitset, SIGUSR1);

    while (1)  {
        rc = sigwaitinfo(&waitset, &info);
        if (rc != -1) {
            printf("sigwaitinfo() fetch the signal - %d\n", rc);
            sig_handler(info.si_signo);
        } else {
            printf("sigwaitinfo() returned err: %d; %s\n", errno, strerror(errno));
        }
    }
}


int main()
{
    sigset_t bset, oset;
    int             i;
    pid_t           pid = getpid();
    pthread_t       ppid;
    

    // Block SIGRTMIN and SIGUSR1 which will be handled in 
    //dedicated thread sigmgr_thread()
    // Newly created threads will inherit the pthread mask from its creator 
    sigemptyset(&bset);
    sigaddset(&bset, SIGRTMIN);
    sigaddset(&bset, SIGUSR1);
    if (pthread_sigmask(SIG_BLOCK, &bset, &oset) != 0)
        printf("!! Set pthread mask failed\n");
    
    // Create the dedicated thread sigmgr_thread() which will handle 
    // SIGUSR1 and SIGRTMIN synchronously
    pthread_create(&ppid, NULL, sigmgr_thread, NULL);
  
    // Create 5 worker threads, which will inherit the thread mask of
    // the creator main thread
    for (i = 0; i < 5; i++) {
        pthread_create(&ppid, NULL, worker_thread, NULL);
    }

    // send out 50 SIGUSR1 and SIGRTMIN signals
    for (i = 0; i < 50; i++) {
        kill(pid, SIGUSR1);
        printf("main thread, send SIGUSR1 No. %d\n", i);
        kill(pid, SIGRTMIN);
        printf("main thread, send SIGRTMIN No. %d\n", i);
        sleep(10);
    }
    exit (0);
}