I have a strange behavior where manpage and google didn't help out.
In my code I want to block / unblock SIGINT when SIGUSR2 is sent. For this I install the signal handler and prepare the set for mask in a function:
void installSignallHandler(){
sBlock.sa_handler = handleBlock;
sigemptyset(&sBlock.sa_mask);
sigaddset(&sBlock.sa_mask, SIGUSR2);
sBlock.sa_flags = 0;
sigaction(SIGUSR2, &sBlock, NULL);
sigemptyset(&signals_protected);
sigaddset(&signals_protected, SIGINT);
// For some reason sigprocmask only works if it is called here the first time
// sigprocmask(SIG_BLOCK, &signals_protected, NULL);
// sigintBlocked = true;
}
Then if SIGUSR2 is sent this function is called:
void handleBlock(int signal){
if(sigintBlocked){
printf("Unblocking SIGINT ...\n");
sigprocmask(SIG_UNBLOCK, &signals_protected, NULL);
sigintBlocked = false;
}
else{
printf("Blocking SIGINT ...\n");
sigprocmask(SIG_BLOCK, &signals_protected, NULL);
sigintBlocked = true;
}
}
For testing I called it like this:
int main(int argc, char **argv) {
installSignallHandler();
while(1){
printf("processing...\n");
sleep(1);
}
return EXIT_SUCCESS;
}
Now the problem: The way I posted the code, sigprocmask takes no effect. But if I uncomment the two lines above, it works. So my two questions:
- Can you explain this behavior?
- What can I do to solve it? - I don't want to start with blocked signal.