I am writing a simple testing program these days, which has the following structure:
================================================
main() {
...
// create a working thread
iRet = pthread_create(&thread_id, NULL, &ThreadFunc, pti);
...
signal(SIGALRM, sig_alrm);
alarm(1);

while(1) {
nanosleep(&tm, NULL); // sleep for 1 millisecond.
}
}

//signal handler for SIGALRM
static void sig_alrm(int signo) {
signal(SIGALRM, sig_alrm);
//now only print the current time
// other codes that do real work are commented
alarm(1);
}

// working thread
void* ThreadFunc (void* arg) {
while(1) {
socket();
bind();
connect();
send();
recv(); // *****
close();// close the socket
}
}
================================================
The problem is that the function sig_alrm() is not called in each second as expected. The time between two consecutive calls to sig_alrm() varies, always several seconds. And I find that sig_alrm() is always invoked when recv() is being called. I am wondering whether calling of recv() within a dedicated thread affects alarm(). Someone here told me that since recv() is a time-consuming function compared to other functions in the thread, as a result, it seems that sig_alrm() is always called when recv() is being called.
Does anyone here know what's wrong with my poor program?

What I want to do is creating some threads to do sth while doing a statistical work periodically(precisely) in the main thread. If alarm() is really not safe for doing this, does anyone have a better solution?

Say thanks in advance.

There is a programming section that's probably better suited for your question.
Report your post (click the report button) and ask a moderator to move it.

Thanks for telling me this. In fact, I have seen the "Programming" section before, however, it is under the sub forum "Non-*NIX Forums" whose name may suggest that it is a place for problems regarding other platforms, such as Windows. I failed to find any other more suitable places, so I posted it here.
Now I am embarrassed by having not found the "Report" button that you mentioned . As a result, I still don't know how to move my post to the right place. I am new here. Would you please help more?

The report button is at the bottom of each post. So there are currently three (and after I've posted this, there are four).

I still cannot find the button you mentioned. :-(

However, I have manually "moved"(modified and pasted) it to "Forums > Non-*NIX Forums > Programming". And after that, I got a reply quickly. It indicates that post must be placed in right place in order to get answers quickly.

Thanks, anyway.

Oh, my god! This time when I view this post, the "Report" buttons finally show up...