process - Synchronization of parent and child with SIGUSR signal in C. Make parent and child read one after the other -

i have created 2 way communication between parent , child processes using 2 pipes. parent , child write data , able make them read data each other. parent writes numbers 1 5, , child writes numbers 6 10. want parent start reading data first, , reading continues in order switching parent child until data read: 6,1,7,2,8,3,9,4,10,5. have tried synchronize reading sigusr1 when parent reading second time program stops. have searched lot find problem can be, , tried tips , alike working examples, nothing seems help. here code:

#include <unistd.h> #include <stdlib.h> #include <stdio.h> #include <string.h> #include <errno.h> #include <signal.h> #include <sys/types.h> #include <sys/wait.h> #include <sys/stat.h>  void paction(int dummy) {    printf("p*************************************************\n"); }   void caction(int dummy) {   printf("c*************************************************\n"); }  int main() {   int pfd[2];   int pfd2[2];   pid_t cfork, pfork;      if (pipe(pfd) == -1 || pipe(pfd2) == -1) {     fprintf(stderr,"pipe failed");     exit(1); }  cfork = fork();  signal(sigusr1, paction);   if (cfork == -1) {      printf("fork failed\n");      exit(1);   }  else if (cfork > 0) { /*parent process*/  int numbers[] = {1, 2,3, 4, 5};  int numbers2[] = {  6, 7,8, 9, 10 };   close(pfd[0]);      /*close read end, write , close write end*/  /*write part*/   int limit = 5;  int i;  (i = 0; < limit; i++) {      printf("parent sends: %d\n", numbers[i]);      write(pfd[1], &numbers[i], sizeof(numbers[i]));       printf("child sends: %d\n", numbers2[i]);      write(pfd2[1], &numbers2[i], sizeof(numbers2[i]));    } printf("***************************************************\n");  close(pfd[1]); close(pfd2[1]); /*read part/////////////////////////////////////////*/     int temp;     int reads = 5;     int j;     (j = 0; j < reads; j++) {     sleep(1);         read(pfd2[0], &temp, sizeof(temp));         printf("parent gets: %d\n", temp);     kill(cfork, sigusr1);         pause();     }  /*printf("***************************************************\n");*/   kill( cfork, sigusr1 );   close(pfd2[0]);        } else { /*child process*/    signal(sigusr1, caction);   close(pfd[1]);   int temp;   int reads = 5;   int j;   pfork = getppid();     (j = 0; j < reads; j++) {           sleep(1);       read(pfd[0], &temp, sizeof(temp));       printf("child gets: %d\n", temp);       kill(getppid(), sigusr1);       pause();     } /*printf("***************************************************\n");*/   close(pfd[0]);   close(pfd2[0]);  }  return 0; 

}

my output looks this:

> parent sends:1  > child sends:6  > parent sends:2  > child sends:7  > parent sends:3  > child sends:8  > parent sends:4  > child sends:9  > parent sends:5 > child sends:10 > **************************************************************    parent gets:6 > c************************************************************ > child gets:1 > p*************************************************************  > parent gets:7 

and here when stops. if can me appreciate because want know problem is, , since beginner in c programming , processes! thank in advance

printf() not async-safe function. calling printf() in both normal code , signal handler cause undefined behavior. in particular, printf() may need take lock on output-stream, while taking locks in signal-handlers very inadvisable (risk of self-deadlock).