incorrect main thread definition in subprocess

[horpto]

Hi, I have program with main process and a bunch subprocesses. Main process sends tasks via pipe to some subprocesses. Each subprocess are getting task synchronously in a separate thread and then process (send http query) in main thread of subprocess. I wanted to make add_signal_handler in main thread of each subprocess. But I got ValueError: add_signal_handler() can only be called from the main thread with uvloop. Asyncio works correctly. I think the main problem in MAIN_THREAD_ID. It's initialized only once.

• uvloop version: 0.16.0

• Python version: 3.8.10

• Platform: Linux devvoip 5.4.0-91-generic #102-Ubuntu SMP Fri Nov 5 16:31:28 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

• Can you reproduce the bug with PYTHONASYNCIODEBUG in env?: yes

• Does uvloop behave differently from vanilla asyncio? How?: uvloop raises ValueError, asyncio works fine