[Issue 21686] segfault if daemon thread is killed, interrupts syscall and throws exception

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=21686

--- Comment #1 from Tobias Pankrath <tobias at pankrath.net> ---
adr says:
so what i suspect it is doing is when the main function returns, druntime tries
to do a final garbage collection sweep. part o tht GC sweep is sending SIGUSR1
to interrupt all threads
[4:46 PM]
the syscall then EINTRs. the thread is then put on hold until the GC is done.

then it might be a race condition on the thread resuming and throwing the
exception and the other thread deinitializing druntime
[4:46 PM]
just a guess but an educated guess at least

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