[Bug 54807] Keil UV4 C51 9.03 (demo) hangs on exit

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=54807

--- Comment #18 from Zeb Figura  ---
I see the problem now. It *is* related to killing threads while they're holding
the mutex.

The reason that adding SIGQUIT to the set isn't enough to fix it, is that the
server closes the remote end of the socket, which generates EPIPE, which in
turn causes wine_server_call() to abort_thread() with the mutex still held.