Need to understand signals received vs sent What is meant by in the following statement (from the paper titled "Implementing Lightweight Threads"):


  As in singlethreaded processes, the number of signals received by the
  process is less than or equal to the number sent.


Why is the number received less than or equal to the number sent. I don't have enough background in singlethreaded processes I guess.
Suppose I sent you 10 letters. Then the number of letters that you have received is at most 10 (some might still be en route).

The reason that this is stressed is that some of the signals could potentially be received by several threads. The operating system guarantees that each signal is received by at most one thread, chosen arbitrarily among threads which have not masked the signal.