c - synchronizing 2 processes -

i'm trying make 2 processes start on task @ same time (count number, example). set 2 ready flags, 1 each process, , perform while loop check if both flags up. 2 processes start counting after check passed. here's not working code, don't know why:

int p1ready=0; int p2ready=0; int onebil = 1000000000;  int main(){  int pid; int exit_code;  pid=fork(); if(pid==0){ //child1     int count1=0;     p1ready=1;    //signal     while(!(p1ready&p2ready))'//wait until 2 processes both ready      while(count1!=onebil){         count1++;     }     exit(0); } else{     pid=fork();     if(pid==0){     //child2         int count2=0;         p2ready=1;    //signal         while(!(p1ready&p2ready));//wait until 2 processes both ready         while(count2!=onebil){             count2++;             }         exit(0);     }     else{     //parent        //do stuff     } return 0; } 

the problem code is, in child1 , child2, own ready flag set 1. cannot see flag of other child being set. example, child1 sees p1ready=1, p2ready 0. why so? how can fix this?

thanks in advance!

the way trying synchronize processes not going work every process creating have own copy of p1ready , p2ready.

what seem looking kind of inter process communication. might want take @ http://en.wikipedia.org/wiki/inter-process_communication see list of possible options.

in simple case 1 mentioned in question sending both of child processes signal parent process enough, suggest best take @ that.