Resuming `python -m asyncio` process is not properly handled on Unix-like platforms

[yihong0618]

Bug report

Bug description:

The resumed REPL can't be exited on Unix-like platforms other than through kill:

./python.exe -m asyncio
ctrl + z
fg
# then the terminal boom

>>> 
Traceback (most recent call last):
  File "/Users/hyi/.local/share/uv/python/cpython-3.14.0rc2-macos-aarch64-none/lib/python3.14/_pyrepl/readline.py", line 395, in multiline_input
    return reader.readline()
           ~~~~~~~~~~~~~~~^^
  File "/Users/hyi/.local/share/uv/python/cpython-3.14.0rc2-macos-aarch64-none/lib/python3.14/_pyrepl/reader.py", line 752, in readline
    self.restore()
    ~~~~~~~~~~~~^^
  File "/Users/hyi/.local/share/uv/python/cpython-3.14.0rc2-macos-aarch64-none/lib/python3.14/_pyrepl/reader.py", line 608, in restore
    self.console.restore()
    ~~~~~~~~~~~~~~~~~~~~^^
  File "/Users/hyi/.local/share/uv/python/cpython-3.14.0rc2-macos-aarch64-none/lib/python3.14/_pyrepl/unix_console.py", line 377, in restore
    signal.signal(signal.SIGWINCH, self.old_sigwinch)
    ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/hyi/.local/share/uv/python/cpython-3.14.0rc2-macos-aarch64-none/lib/python3.14/signal.py", line 58, in signal
    handler = _signal.signal(_enum_to_int(signalnum), _enum_to_int(handler))
ValueError: signal only works in main thread of the main interpreter
>>> 
Traceback (most recent call last):
  File "/Users/hyi/.local/share/uv/python/cpython-3.14.0rc2-macos-aarch64-none/lib/python3.14/_pyrepl/readline.py", line 395, in multiline_input
    return reader.readline()
           ~~~~~~~~~~~~~~~^^
  File "/Users/hyi/.local/share/uv/python/cpython-3.14.0rc2-macos-aarch64-none/lib/python3.14/_pyrepl/reader.py", line 752, in readline
    self.restore()
    ~~~~~~~~~~~~^^
  File "/Users/hyi/.local/share/uv/python/cpython-3.14.0rc2-macos-aarch64-none/lib/python3.14/_pyrepl/reader.py", line 608, in restore
    self.console.restore()
    ~~~~~~~~~~~~~~~~~~~~^^
  File "/Users/hyi/.local/share/uv/python/cpython-3.14.0rc2-macos-aarch64-none/lib/python3.14/_pyrepl/unix_console.py", line 377, in restore
    signal.signal(signal.SIGWINCH, self.old_sigwinch)
    ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/hyi/.local/share/uv/python/cpython-3.14.0rc2-macos-aarch64-none/lib/python3.14/signal.py", line 58, in signal
    handler = _signal.signal(_enum_to_int(signalnum), _enum_to_int(handler))
ValueError: signal only works in main thread of the main interpreter
>>> 

CPython versions tested on:

CPython main branch

Operating systems tested on:

macOS

Linked PRs

• gh-139391: properly handle signal.signal() in UnixConsole when called from a non-main thread #139392

[yihong0618]

update

linux can also have this problem

./python -m asyncio
>>> 
Traceback (most recent call last):
  File "/home/hyi/cpython/Lib/_pyrepl/readline.py", line 395, in multiline_input
    return reader.readline()
           ~~~~~~~~~~~~~~~^^
  File "/home/hyi/cpython/Lib/_pyrepl/reader.py", line 752, in readline
    self.restore()
    ~~~~~~~~~~~~^^
  File "/home/hyi/cpython/Lib/_pyrepl/reader.py", line 608, in restore
    self.console.restore()
    ~~~~~~~~~~~~~~~~~~~~^^
  File "/home/hyi/cpython/Lib/_pyrepl/unix_console.py", line 393, in restore
    signal.signal(signal.SIGWINCH, self.old_sigwinch)
    ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/hyi/cpython/Lib/signal.py", line 58, in signal
    handler = _signal.signal(_enum_to_int(signalnum), _enum_to_int(handler))
ValueError: signal only works in main thread of the main interpreter
>>> 
Traceback (most recent call last):
  File "/home/hyi/cpython/Lib/_pyrepl/readline.py", line 395, in multiline_input
    return reader.readline()
           ~~~~~~~~~~~~~~~^^
  File "/home/hyi/cpython/Lib/_pyrepl/reader.py", line 752, in readline
    self.restore()
    ~~~~~~~~~~~~^^
  File "/home/hyi/cpython/Lib/_pyrepl/reader.py", line 608, in restore
    self.console.restore()
    ~~~~~~~~~~~~~~~~~~~~^^
  File "/home/hyi/cpython/Lib/_pyrepl/unix_console.py", line 393, in restore
    signal.signal(signal.SIGWINCH, self.old_sigwinch)
    ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/hyi/cpython/Lib/signal.py", line 58, in signal
    handler = _signal.signal(_enum_to_int(signalnum), _enum_to_int(handler))
ValueError: signal only works in main thread of the main interpreter
>>> 
Traceback (most recent call last):
  File "/home/hyi/cpython/Lib/_pyrepl/readline.py", line 395, in multiline_input
    return reader.readline()
           ~~~~~~~~~~~~~~~^^
  File "/home/hyi/cpython/Lib/_pyrepl/reader.py", line 752, in readline
    self.restore()
    ~~~~~~~~~~~~^^
  File "/home/hyi/cpython/Lib/_pyrepl/reader.py", line 608, in restore
    self.console.restore()
    ~~~~~~~~~~~~~~~~~~~~^^
  File "/home/hyi/cpython/Lib/_pyrepl/unix_console.py", line 393, in restore
    signal.signal(signal.SIGWINCH, self.old_sigwinch)
    ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/hyi/cpython/Lib/signal.py", line 58, in signal
    handler = _signal.signal(_enum_to_int(signalnum), _enum_to_int(handler))
ValueError: signal only works in main thread of the main interpreter
>>> 
Traceback (most recent call last):
  File "/home/hyi/cpython/Lib/_pyrepl/reader.py", line 748, in readline
    self.handle1()
    ~~~~~~~~~~~~^^
  File "/home/hyi/cpython/Lib/_pyrepl/reader.py", line 731, in handle1
    self.do_cmd(cmd)
    ~~~~~~~~~~~^^^^^
  File "/home/hyi/cpython/Lib/_pyrepl/reader.py", line 656, in do_cmd
    command.do()
    ~~~~~~~~~~^^
  File "/home/hyi/cpython/Lib/_pyrepl/commands.py", line 430, in do
    raise EOFError
EOFError

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/hyi/cpython/Lib/_pyrepl/readline.py", line 395, in multiline_input
    return reader.readline()
           ~~~~~~~~~~~~~~~^^
  File "/home/hyi/cpython/Lib/_pyrepl/reader.py", line 752, in readline
    self.restore()
    ~~~~~~~~~~~~^^
  File "/home/hyi/cpython/Lib/_pyrepl/reader.py", line 608, in restore
    self.console.restore()
    ~~~~~~~~~~~~~~~~~~~~^^
  File "/home/hyi/cpython/Lib/_pyrepl/unix_console.py", line 393, in restore
    signal.signal(signal.SIGWINCH, self.old_sigwinch)
    ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/hyi/cpython/Lib/signal.py", line 58, in signal
    handler = _signal.signal(_enum_to_int(signalnum), _enum_to_int(handler))
ValueError: signal only works in main thread of the main interpreter
>>> Terminated
[hyi@rocky cpython]$ ^C
[hyi@rocky cpython]$ uname -a
Linux rocky 6.15.11-orbstack-00539-g9885ebd8e3f4 #1 SMP PREEMPT Fri Aug 22 08:24:56 UTC 2025 aarch64 aarch64 aarch64 GNU/Linux