multithreading - C pthreads and signaling -

i'm having alot of trouble on assignment class, , great. need code create 4 producer threads continuously loop , send sigusr1 or sigusr2 4 consumer threads. 2 respond sigusr1, , 2 respond sigusr2. signals being sent producers, , received consumers, nothing happens after , program crashes. below program, , output gdb when ran.

  #include <pthread.h> #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <semaphore.h> #include <signal.h> #include <time.h>  #define np  4 #define nc1 2 #define nc2 2 #define cnt 10  void handler1(int); void handler2(int);  typedef struct {     int sent;     int received;     int buf[1];        int sig1;                   int sig2;                   sem_t con;              sem_t prod;           } sbuf_t;  sbuf_t buff; pthread_t threads[9];  void *producer() {     srand(time(0));     int s,i;     while(1){          sem_wait(&buff.prod);         s=(rand()%2)+1;         //printf("prod ready \n");         if(s==1){             buff.sent++;             for(i=0;i<4;i++){             pthread_kill(threads[i],sigusr1);}         }         else if(s==2){             buff.sent++;             for(i=0;i<4;i++){             pthread_kill(threads[i],sigusr1);}         }         usleep(rand()%100000);         sem_post(&buff.prod);     }   }  void *consumer1() {     signal(sigusr1, handler1);     //printf("waiting 1\n");     while(1){      } }  void *consumer2() {     signal(sigusr2, handler2);     //printf("waiting 2\n");     while(1){      } }  void handler1(int signum){     printf("caught 1\n");     if(signum==sigusr1){         sem_wait(&buff.con);         buff.received++;         buff.sig1++;          sem_post(&buff.con);     } }  void handler2(int signum){     printf("caught 2 \n");     if(signum==sigusr2){         sem_wait(&buff.con);         buff.received++;         buff.sig2++;          sem_post(&buff.con);     } }  void main(){     buff.sig1=0;     buff.sig2=0;     buff.sent=0;     buff.received=0;     int index;           sem_init(&buff.con, 0, 1);     sem_init(&buff.prod, 0, 1);          (index = 0;index < nc1;index++) {             pthread_create(&threads[index], null, consumer1,null);         }     (index = 0;index < nc2;index++) {             pthread_create(&threads[index+2], null, consumer2,null);         }     (index = 0; index < np; index++) {             pthread_create(&threads[index+4], null, producer,null);         } 

and gdb

(gdb) run starting program: /home/eric/a.out  [thread debugging using libthread_db enabled] using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1". [new thread 0x7ffff77f6700 (lwp 4944)] [new thread 0x7ffff6ff5700 (lwp 4945)] [new thread 0x7ffff67f4700 (lwp 4946)] [new thread 0x7ffff5ff3700 (lwp 4947)] [new thread 0x7ffff57f2700 (lwp 4948)]  program received signal sigusr1, user defined signal 1. [switching thread 0x7ffff5ff3700 (lwp 4947)] consumer2 () @ lab3.c:68 68      } (gdb) continue continuing.  program received signal sigusr1, user defined signal 1. [switching thread 0x7ffff67f4700 (lwp 4946)] consumer2 () @ lab3.c:68 68      } (gdb)  continuing.  program received signal sigusr1, user defined signal 1. [switching thread 0x7ffff6ff5700 (lwp 4945)] consumer1 () @ lab3.c:60 60      } (gdb)  continuing. [new thread 0x7ffff4ff1700 (lwp 4949)]  program received signal sigusr1, user defined signal 1. [switching thread 0x7ffff77f6700 (lwp 4944)] consumer1 () @ lab3.c:60 60      } (gdb)  continuing. caught 1 caught 1 caught 1  program received signal sigusr1, user defined signal 1. [switching thread 0x7ffff5ff3700 (lwp 4947)] consumer2 () @ lab3.c:68 68      } (gdb)  continuing. caught 1 [new thread 0x7ffff47f0700 (lwp 4950)] caught 1  program received signal sigusr1, user defined signal 1. [switching thread 0x7ffff67f4700 (lwp 4946)] consumer2 () @ lab3.c:68 68      } (gdb)  continuing.  program received signal sigusr1, user defined signal 1. [switching thread 0x7ffff6ff5700 (lwp 4945)] consumer1 () @ lab3.c:60 60      } (gdb)  continuing. caught 1  program received signal sigusr1, user defined signal 1. [switching thread 0x7ffff77f6700 (lwp 4944)] consumer1 () @ lab3.c:60 60      } (gdb)  continuing. caught 1 [new thread 0x7ffff3fef700 (lwp 4951)] caught 1  program received signal sigusr1, user defined signal 1. [switching thread 0x7ffff5ff3700 (lwp 4947)] consumer2 () @ lab3.c:68 68      } (gdb)  continuing.  program received signal sigusr1, user defined signal 1. [switching thread 0x7ffff67f4700 (lwp 4946)] consumer2 () @ lab3.c:68 68      } (gdb)  continuing. caught 1 [thread 0x7ffff3fef700 (lwp 4951) exited] [thread 0x7ffff47f0700 (lwp 4950) exited] [thread 0x7ffff4ff1700 (lwp 4949) exited] [thread 0x7ffff57f2700 (lwp 4948) exited] [thread 0x7ffff5ff3700 (lwp 4947) exited] [thread 0x7ffff67f4700 (lwp 4946) exited] [thread 0x7ffff7fda740 (lwp 4940) exited] cannot find user-level thread lwp 4945: generic error (gdb)  continuing. cannot execute command without live selected thread. (gdb)  

take at: sigemptyset,sigaddset maybe helps you