BusError in uvloop within loop extract_stack for nested async_generators
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- uvloop version:
- 0.19.0 (tested 0.17.0 to 0.19.0)
- Python version: 3.12.4
- Platform: OSX Ventura 13.4/ Darwin 22.5.0
- Can you reproduce the bug with
PYTHONASYNCIODEBUG
in env?: - This bug only occurs if
-X dev
orPYTHONDEVMODE=1
orPYTHONASYNCIODEBUG=1
orloop.set_debug(True)
- Does uvloop behave differently from vanilla asyncio? How?:
- Vanilla asyncio and uvloop with
loop.set_debug(False)
do not crash in nested async_generator.asend
calls
I have a pattern called DeferredExecutor
which basically allows one to write:
class Foo:
@database(transaction=True, iterable=False)
async def save(self, *args, **kwargs):
# /snip
rows = yield DeferredQuery("some sql")
assert isinstance(rows, tuple)
yield Return(...)
And have it be wrapped by a decorator that will call the async_generator, run the deferred queries against a DB and .asend(
the result back into the generator, which will throw an StopAsyncIteration
at the conclusion of the generator, and allows me to catch it and end the generators execution.
I am getting my database access object library to run on Python 3.12 (jumping from Python 3.7).
However, on Python 3.12, a particular integration test that uses a particularly reduced implementation:
class Tenant:
@database(iterable=False, transaction=True)
async def invite_users(cls, *tenant_user_pairs, instance=None):
invites = (instance or cls).create_invites_for(*tenant_user_pairs)
gen_event_loop = Invite.save.raw_iterable(*invites)
result = None
while True:
result = await gen_event_loop.asend(result)
if isinstance(result, Return):
break
result = yield result
yield result # StopAsyncIteration gets thrown here
causes uvloop to crash with a Bus Error on OSX but only when loop.set_debug(True)
(which is autoset via the environment variables or interpreter devmode)
Regular asyncio, debug or not, works just fine. If I patch the EventLoopPolicy to.set_debug(False)
like:
def patch_uvloop():
if uvloop_version_info < (99, 99, 99) and platform.system() == 'Darwin':
cls = uvloop.EventLoopPolicy
if hasattr(cls, '__patched__'):
return cls
class EventLoopPolicy(cls):
__patched__ = True
# ARJ: so uvloop will crash the entire interpreter sometimes
# and the crash originates on OSX. Disable debug mode
# (which keeps it from touching uvloop's extract_stack() which
# explodes badly)
def _loop_factory(self):
loop = super()._loop_factory()
loop.set_debug(False)
return loop
uvloop.EventLoopPolicy = EventLoopPolicy
asyncio.set_event_loop_policy(uvloop.EventLoopPolicy())
Then the crashes never happen.
I do have lldb/gdb and the patience to recompile things with more debugging information (provided I know -how-) but a careful inspection of the following stack trace shows that it explodes after going into the extract_stack
function of uvloop:
uvloop/uvloop/handles/handle.pyx
Lines 118 to 119 in 6c770dc
Lines 14 to 15 in 6c770dc
This does remind me of python/cpython#94694
I wonder if the extract_stack function is tolerant of encountering negative numbers in the offset extraction of the trace.
Stack report:
stack.txt