Stabilize tests with timeouts to reduce flakiness

[rwgk]

Failures like the one shown below tend to be distracting, and it's probably very easy to avoid the distractions:

xref:

• Test fixes as required for QA #1567 (comment)
• https://github.com/NVIDIA/cuda-python/actions/runs/21995912807/job/63556542405?pr=1621

@Andy-Jost's suggestion:

@pytest.mark.flaky(reruns=2)

Other obvious idea: longer timeout?

Or both?

---

Example of full error for completeness:

=================================== FAILURES ===================================
_____________________ TestIpcReexport.test_main[DeviceMR] ______________________

self = <test_send_buffers.TestIpcReexport object at 0x478595203d0>
ipc_device = <Device 0 (Tesla T4)>
ipc_memory_resource = <cuda.core._memory._device_memory_resource.DeviceMemoryResource object at 0x478594efae0>

    def test_main(self, ipc_device, ipc_memory_resource):
        # Set up the device.
        device = ipc_device
        device.set_current()
    
        # Allocate, fill a buffer.
        mr = ipc_memory_resource
        pgen = PatternGen(device, NBYTES)
        buffer = mr.allocate(NBYTES)
        pgen.fill_buffer(buffer, seed=0)
    
        # Set up communication.
        q_bc = mp.Queue()
        event_b, event_c = [mp.Event() for _ in range(2)]
    
        # Spawn B and C.
        proc_b = mp.Process(target=self.process_b_main, args=(buffer, q_bc, event_b))
        proc_c = mp.Process(target=self.process_c_main, args=(q_bc, event_c))
        proc_b.start()
        proc_c.start()
    
        # Wait for C to signal completion then clean up.
        event_c.wait(timeout=CHILD_TIMEOUT_SEC)
        event_b.set()  # b can finish now
        proc_b.join(timeout=CHILD_TIMEOUT_SEC)
        proc_c.join(timeout=CHILD_TIMEOUT_SEC)
        assert proc_b.exitcode == 0
>       assert proc_c.exitcode == 0
E       AssertionError: assert 1 == 0
E        +  where 1 = <Process name='Process-25' pid=5129 parent=4876 stopped exitcode=1>.exitcode

buffer     = <Buffer ptr=0x316000000 size=64>
device     = <Device 0 (Tesla T4)>
event_b    = <Event at 0x47858f9ab10 set>
event_c    = <Event at 0x4785952cf90 unset>
ipc_device = <Device 0 (Tesla T4)>
ipc_memory_resource = <cuda.core._memory._device_memory_resource.DeviceMemoryResource object at 0x478594efae0>
mr         = <cuda.core._memory._device_memory_resource.DeviceMemoryResource object at 0x478594efae0>
pgen       = <helpers.buffers.PatternGen object at 0x47859dd1e10>
proc_b     = <Process name='Process-24' pid=5128 parent=4876 stopped exitcode=0>
proc_c     = <Process name='Process-25' pid=5129 parent=4876 stopped exitcode=1>
q_bc       = <multiprocessing.queues.Queue object at 0x47859dd1910>
self       = <test_send_buffers.TestIpcReexport object at 0x478595203d0>

tests/memory_ipc/test_send_buffers.py:97: AssertionError
----------------------------- Captured stderr call -----------------------------
Traceback (most recent call last):
  File "/opt/hostedtoolcache/Python/3.14.2/x64-freethreaded/lib/python3.14t/multiprocessing/queues.py", line 262, in _feed
    obj = _ForkingPickler.dumps(obj)
  File "/opt/hostedtoolcache/Python/3.14.2/x64-freethreaded/lib/python3.14t/multiprocessing/reduction.py", line 51, in dumps
    cls(buf, protocol).dump(obj)
    ~~~~~~~~~~~~~~~~~~~~~~~^^^^^
  File "cuda/core/_memory/_buffer.pyx", line 99, in cuda.core._memory._buffer.Buffer.__reduce__
    return Buffer.from_ipc_descriptor, (self.memory_resource, self.get_ipc_descriptor())
  File "cuda/core/_memory/_buffer.pyx", line 139, in cuda.core._memory._buffer.Buffer.get_ipc_descriptor
    self._ipc_data = IPCDataForBuffer(_ipc.Buffer_get_ipc_descriptor(self), False)
  File "cuda/core/_memory/_ipc.pyx", line 160, in cuda.core._memory._ipc.Buffer_get_ipc_descriptor
    if not self.memory_resource.is_ipc_enabled:
AttributeError: 'NoneType' object has no attribute 'is_ipc_enabled'
Process Process-25:
Traceback (most recent call last):
  File "/opt/hostedtoolcache/Python/3.14.2/x64-freethreaded/lib/python3.14t/multiprocessing/process.py", line 320, in _bootstrap
    self.run()
    ~~~~~~~~^^
  File "/opt/hostedtoolcache/Python/3.14.2/x64-freethreaded/lib/python3.14t/multiprocessing/process.py", line 108, in run
    self._target(*self._args, **self._kwargs)
    ~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/__w/cuda-python/cuda-python/cuda_core/tests/memory_ipc/test_send_buffers.py", line 121, in process_c_main
    buffer = q_bc.get(timeout=CHILD_TIMEOUT_SEC)
  File "/opt/hostedtoolcache/Python/3.14.2/x64-freethreaded/lib/python3.14t/multiprocessing/queues.py", line 112, in get
    raise Empty
_queue.Empty