Signal catching in Solaris

Question

I tried to catch unique signal(SIGCHLD) from child processes.
A problem is that parent should catch SIGCHLD signals from multiple children simultaneously.
In Solaris 5.5 and 5.8, some of SIGCHLD signals disapear.
But there is no zombie process.
I think while a process catches one signal if the process gets same kind of signal, it blocks that signal in a queue.
But in the real situation, kernel couldn't block same kind of signal.
Plz, let me know why signals disapear.
And how can I do catch all of them.
FYI,
I used sigaction function.
Below, simple test program.
#include <stdio.h>
#include <sys/wait.h>
#include <signal.h>
#include <stdlib.h>
#include <unistd.h>
void child_do();
void usr1_handle(int);
void chld_handle(int);
int main()
int i;
int pid;
struct sigaction chld_act, usr1_act;
printf("sigaction error\n");
exit(1);
for(i=0; i<5; i++)
printf("%d : child create.\n",i+1);
pid = fork();
if (pid == 0)
child_do();
sleep(5);
kill(0, SIGUSR1);
while(1);
return 0;
void child_do()
pause();
void usr1_handle(int signo)
if (getpid()==getpgrp())
return;
printf("receive SIGUSR1\n");
exit(0);
void chld_handle(int signo)
int childPid, childStatus;
childPid = wait(&childStatus);
printf("%d : Child was killed!\n",childPid);

Answer 1

Hope it gives you some clue:
http://docs.sun.com/app/docs/doc/816-5137/6mba5vpju?a=view#gen-10856