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Eric Eastwood
7da21a715d
This means you can use `get_success(...)` anywhere regardless of what kind of work needs to be done. Spawning from adding some more async Rust things in https://github.com/element-hq/synapse/pull/19846 and wanting something more standard instead of the custom `till_deferred_has_result(...)` that has crept in to a few files. Alternative to https://github.com/element-hq/synapse/pull/19867 spurred on by [this comment](https://github.com/element-hq/synapse/pull/19867#discussion_r3441774685) from @erikjohnston ### How does this work? Previously, `get_success(...)` just ran in a hot-loop advancing the Twisted reactor clock which didn't give any time for other threads to do some work or acquire the GIL if necessary (whenever there is a hand-off from Rust to Python, we need the GIL). Now, `get_success(...)` loops until we see a result (until we hit the ~0.1s real-time timeout). In the loop, we call [`time.sleep(0)`](https://docs.python.org/3/library/time.html#time.sleep) which will "Suspend execution of the calling thread [...]" (CPU and GIL) to allow other threads to do some work. Then like before, we advance the Twisted reactor clock to run any scheduled callbacks which includes anything the other threads may have scheduled. ### Does this slow down the entire test suite? Seems just as fast as before. There is minutes variance in what we had before and after but both are within the same range of each other. (see PR for actual before/after timings)