I've encountered a situation where signal handlers don't seem to
run. With the following program, sending it SIGINT won't trigger the
handler, however if you remove the system* call, then the handler will
run.

  (use-modules (ice-9 threads))

  (call-with-new-thread
   (lambda ()
     ;; Remove the following system* call to fix the handler
     (system* "echo" "foo")))

  (sigaction SIGINT
    (lambda (sig)
      (peek "SIGINT handler")
      (exit 1)))

  (for-each
   (lambda _
     (sleep 1))
   (iota 30))

  (display "normal exit\n")