[bleeep]

If I do "kill -HUP <pid>", the SIGHUP is delivered to a process. Each thread in the process has a separate mask of signals its willing to handle. One of those threads that have SIGHUP unmasked will have the signal delivered to it.

If a thread dereferences a null pointer, the sigsegv is only relevant to the thread that dereffed the NULL pointer - that's the only thing that can do anything with it. It makes no sense to send that signal to another thread - it's a signal generated synchronously by the thread itself, rather than asynchronously from anywhere else.