1. There are some discussion about "sig_atomic_t fd;" in PR 12670. POSIX spec doesn't define its type. In practice, most implementation defines it as int. Go to Atomic-Types So far it works fine on known OSes. However, on VxWorks, sig_atomic_t is defined as 'unsigned char'. Assigning it to -1 will have problem. So we define wakeup.fd as int specially for VxWorks.
2. VxWorks has no getitimer() and setitimer() C api available. So skipping the test on VxWorks.

https://bugs.python.org/issue31904