Bug report

Bug description:

Short Version

Adding_clock_resolution in this line has no effect (at least on linux):

Becausetime() returns a float of the current epoch time, and clock resolution is1e-9,self.time() == self.time() + self._clock_resolution, due to floating point precision loss. In a corner case whereself.time() matches the next scheduled timerexactly, it would have to wait for the next iteration of the event loop to get run.

Longer Version

I was writing deterministic unittests involving timers and asyncio. I used a VirtualClock which would mock outloop.time() andloop.select():

https://aiotools.readthedocs.io/en/latest/_modules/aiotools/timer.html#VirtualClock

The internal time does not advance unless a timer is awaited.

Unfortunately when using realistic timestamps, because of the precision loss described above, the event loop gets permanently stuck at the exact time of the next timer, and never advances.

In the snippet below, the problem is thathandle._when >= end_time is always true:

This was introduced in this change:
ed1654f

CPython versions tested on:

3.10

Operating systems tested on:

Linux