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Signalfd Is Useless (2015)
UNIX (well, POSIX) signals are probably one of the worst parts of the UNIX API, and that’s a relatively high bar. A signal can be sent to your program at any point when it’s running, and you have to deal with it somehow. Traditionally, there are three ways ...
A standard solution is the “self-pipe trick”: open an unnamed pipe, write a byte to it in your signal handler and return, and read from it in the main loop. So, if you’re in the middle of reading from a network socket, waiting for a timeout, or even closing a file descriptor, that system call gets aborted so that the signal handler can run. Thanks to Nelson Elhage for pointing me at the LWN article, and Alex Chernyakhovsky, David Benjamin, and Yehuda Katz for discussions about all the unfortunate parts of signal handling.
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