bug#69561: 30.0.50; Freeze from M-x gnus on macOS

["Gerd Möllmann" <gerd.moellmann@gmail.com>]

Gerd Möllmann <gerd.moellmann@gmail.com> writes:
Forgot a sampel C backtrace

(lldb) bt 10
* thread #1, queue = 'com.apple.main-thread', stop reason = signal SIGSTOP
  * frame #0: 0x00007ff81b20f7f2 libsystem_kernel.dylib`__pthread_sigmask + 10
    frame #1: 0x00007ff81b2487f7 libsystem_pthread.dylib`pthread_sigmask + 9
    frame #2: 0x000000010010bc60 emacs`block_interrupt_signal(oldset=<unavailable>) at sysdep.c:891:3 [opt]
    frame #3: 0x00000001002024d0 emacs`really_call_select(arg=0x00007ff7bfef9008) at thread.c:619:3 [opt]
    frame #4: 0x0000000100202490 emacs`thread_select [inlined] flush_stack_call_func(func=<unavailable>, arg=0x00007ff7bfef9008) at lisp.h:4457:3 [opt]
    frame #5: 0x0000000100202480 emacs`thread_select(func=<unavailable>, max_fds=<unavailable>, rfds=<unavailable>, wfds=<unavailable>, efds=<unavailable>, timeout=<unavailable>, sigmask=0x0000000000000000) at thread.c:656:3 [opt]
    frame #6: 0x00000001001d94d2 emacs`wait_reading_process_output(time_limit=<unavailable>, nsecs=<unavailable>, read_kbd=0, do_display=false, wait_for_cell=(struct Lisp_Symbol *) $123 = 0x00000001007d24b0, wait_proc=0x00007fccffdcc9d8, just_wait_proc=0) at process.c:5484:9 [opt]
    frame #7: 0x00000001001d8bdc emacs`Faccept_process_output(process=<unavailable>, seconds=(EMACS_INT) $132 = 1, millisec=<unavailable>, just_this_one=(struct Lisp_Symbol *) $150 = 0x00000001007d24b0) at process.c:4912:7 [opt]
    frame #8: 0x00000001001ce53c emacs`exec_byte_code(fun=<unavailable>, args_template=<unavailable>, nargs=<unavailable>, args=<unavailable>) at bytecode.c:814:14 [opt]
    frame #9: 0x0000000100183d60 emacs`funcall_lambda(fun=<unavailable>, nargs=<unavailable>, arg_vector=<unavailable>) at eval.c:3194:9 [opt] [artificial]