Now let's reconsider the very same scenario, only this time we use the SA_NODEFER signal flag. So, when the first instance of signal n arrives, our process jumps into the signal-handling code (which will take 55 ms to complete). As before, the second signal will arrive just 10 ms into the signal-handling code, but hang on, this time it is not masked; it is not deferred. Thus, we will reenter the signal handler function immediately. Then, 20 ms later (after the signal handler was first entered by signal n instance #1), the third signal instance arrives. Again, we will reenter the signal handler function. Yes, this will happen five times.
Figure 4 shows us this scenario: