Rerunning Continuation

[wlruys]

Minimal Reproducer (~every 1 in 10 runs):

from parla import Parla, spawn
from parla.cython.tasks import AtomicTaskSpace

def wrapper_chain(T, i=0):
    @spawn(T[i], dependencies=[T[i-1]])
    async def outer():
        TT = AtomicTaskSpace(f"task_{i}")
        await TT

with Parla():
    T = AtomicTaskSpace("main")
    i = 0
    while i < 30000:
        wrapper_chain(T, i)
        i += 1

Error:

Exception in Task  Task(main_64) :  cannot reuse already awaited coroutine Traceback (most recent call last):

  File "tasks.pyx", line 416, in parla.cython.tasks.Task.run

  File "tasks.pyx", line 566, in parla.cython.tasks.ComputeTask._execute_task

  File "scheduler.pyx", line 494, in parla.cython.scheduler._task_callback

RuntimeError: cannot reuse already awaited coroutine

Hypothesis:

This is behaving like the continuation task is duplicated in the task queue due to a race condition. At a first pass all of the counts look correct. Events are reset to 1 before dependencies are added. Events are either handled by the worker thread or scheduler thread (whichever gets fetch_sub(1) == 1 first)

Adding print statements makes the race condition disappear.

[wlruys]

Everyway I've tried so far to log the cause of this error in the runtime makes it disappear. I may need a better reproduction script or even lighter weight logging.