uasyncio: Handle colliding sleep_ms calls.

smurfix · smurfix · commit 42f40b453cc8 · 2023-02-17T11:09:44.000+01:00
If two tasks try to start sleeping at the same time, the SingletonGenerator will be in use, thus we need to allocate a new temporary handler on the heap. As the singleton isn't that single any more, it gets renamed. Found by taskgroup test micropython#12.
diff --git a/extmod/uasyncio/core.py b/extmod/uasyncio/core.py
@@ -40,7 +40,7 @@ class TimeoutError(Exception):
 
 
 # "Yield" once, then raise StopIteration
-class SingletonGenerator:
+class SleepHandler:
     def __init__(self):
         self.state = None
         self.exc = StopIteration()
@@ -59,9 +59,10 @@ def __next__(self):
 
 
 # Pause task execution for the given time (integer in milliseconds, uPy extension)
-# Use a SingletonGenerator to do it without allocating on the heap
-def sleep_ms(t, sgen=SingletonGenerator()):
-    assert sgen.state is None
+# Try not to allocate a SleepHandler on the heap if possible
+def sleep_ms(t, sgen=SleepHandler()):
+    if sgen.state is not None:  # the static one is busy
+        sgen = SleepHandler()
     sgen.state = ticks_add(ticks(), max(0, t))
     return sgen
 
