Celery warm shutdown with celery>=5.5.0b3 and eventlet>=0.37.0

# Checklist

- [X] I have verified that the issue exists against the `main` branch of Celery.
- [ ] This has already been asked to the [discussions forum](https://github.com/celery/celery/discussions) first.
- [X] I have read the relevant section in the
 [contribution guide](https://docs.celeryq.dev/en/main/contributing.html#other-bugs)
 on reporting bugs.
- [X] I have checked the [issues list](https://github.com/celery/celery/issues?q=is%3Aissue+label%3A%22Issue+Type%3A+Bug+Report%22+-label%3A%22Category%3A+Documentation%22)
 for similar or identical bug reports.
- [X] I have checked the [pull requests list](https://github.com/celery/celery/pulls?q=is%3Apr+label%3A%22PR+Type%3A+Bugfix%22+-label%3A%22Category%3A+Documentation%22)
 for existing proposed fixes.
- [X] I have checked the [commit log](https://github.com/celery/celery/commits/main)
 to find out if the bug was already fixed in the main branch.
- [X] I have included all related issues and possible duplicate issues
 in this issue (If there are none, check this box anyway).
- [ ] I have tried to reproduce the issue with [pytest-celery](https://docs.celeryq.dev/projects/pytest-celery/en/latest/userguide/celery-bug-report.html) and added the reproduction script below.

## Mandatory Debugging Information

- [X] I have included the output of ``celery -A proj report`` in the issue.
 (if you are not able to do this, then at least specify the Celery
 version affected).
- [X] I have verified that the issue exists against the `main` branch of Celery.
- [ ] I have included the contents of ``pip freeze`` in the issue.
- [X] I have included all the versions of all the external dependencies required
 to reproduce this bug.

## Optional Debugging Information

- [ ] I have tried reproducing the issue on more than one Python version
 and/or implementation.
- [ ] I have tried reproducing the issue on more than one message broker and/or
 result backend.
- [ ] I have tried reproducing the issue on more than one version of the message
 broker and/or result backend.
- [ ] I have tried reproducing the issue on more than one operating system.
- [X] I have tried reproducing the issue on more than one workers pool.
- [ ] I have tried reproducing the issue with autoscaling, retries,
 ETA/Countdown & rate limits disabled.
- [ ] I have tried reproducing the issue after downgrading
 and/or upgrading Celery and its dependencies.

## Related Issues and Possible Duplicates


#### Related Issues

- None

#### Possible Duplicates

- None

## Environment & Settings

**Celery version**:

<details>
<summary><code>celery report</code> Output:</summary>


```
software -> celery:5.6.2 (recovery) kombu:5.6.2 py:3.9.25
 billiard:4.2.4 py-amqp:5.3.1
platform -> system:Linux arch:64bit, ELF
 kernel version:6.10.11-linuxkit imp:CPython
loader -> celery.loaders.app.AppLoader
settings -> transport:amqp results:django-db

```


</details>

# Steps to Reproduce

## Required Dependencies

- **Python Version**: 3.9.25
- **Minimal Celery Version**: 5.5.0b3
- **Minimal Kombu Version**: N/A or Unknown
- **Minimal Broker Version**: N/A or Unknown
- **Minimal Result Backend Version**: N/A or Unknown
- **Minimal OS and/or Kernel Version**: N/A or Unknown
- **Minimal Broker Client Version**: N/A or Unknown
- **Minimal Result Backend Client Version**: N/A or Unknown
- **Minimal Eventlet Version**: 0.37.0

### Python Packages

<details>
<summary><code>pip freeze</code> Output:</summary>


```
```


</details>

### Other Dependencies

<details>

eventlet>=0.37.0

</details>

## Minimally Reproducible Test Case


In https://github.com/celery/celery/pull/9222 print was changed to os.write.
Eventlet in release [0.37.0](https://github.com/eventlet/eventlet/blob/master/NEWS) changed logic of os.read/write https://github.com/eventlet/eventlet/pull/975/changes.
This combination leads to exception during "warm shutdown"

<details>
Run


```
 celery -A myproj worker --pool=eventlet
```


worker will be started


```
 -------------- celery@9be1ca044182 v5.6.2 (recovery)
--- ***** ----- 
-- ******* ---- Linux-6.10.11-linuxkit-aarch64-with-glibc2.36 2026-02-02 17:45:29
- *** --- * --- 
- ** ---------- [config]
- ** ---------- .> app: myproj:0xffff997d2100
- ** ---------- .> transport: amqp://guest:**@rabbitmq:5672//
- ** ---------- .> results: 
- *** --- * --- .> concurrency: 10 (eventlet)
-- ******* ---- .> task events: OFF (enable -E to monitor tasks in this worker)
--- ***** ----- 
 -------------- [queues]
 .> celery exchange=celery(direct) key=celery

```


then hit Ctrl+C. Exception will be raised(see Actual Behavior)
</details>


# Expected Behavior

<details>
No exception. Same as for prefork(for example)


```
celery -A myproj worker --pool=eventlet
```


worker will be started


```
 -------------- celery@9be1ca044182 v5.6.2 (recovery)
--- ***** ----- 
-- ******* ---- Linux-6.10.11-linuxkit-aarch64-with-glibc2.36 2026-02-02 17:45:29
- *** --- * --- 
- ** ---------- [config]
- ** ---------- .> app: myproj:0xffff997d2100
- ** ---------- .> transport: amqp://guest:**@rabbitmq:5672//
- ** ---------- .> results: 
- *** --- * --- .> concurrency: 10 (eventlet)
-- ******* ---- .> task events: OFF (enable -E to monitor tasks in this worker)
--- ***** ----- 
 -------------- [queues]
 .> celery exchange=celery(direct) key=celery

```


then hit Ctrl+C. No exception after this. Result should look like


```
^C
worker: Hitting Ctrl+C again will initiate cold shutdown, terminating all running tasks!

worker: Warm shutdown (MainProcess)

```


</details>

# Actual Behavior


<details>


```
^C[2026-02-02 17:54:32,127: CRITICAL/MainProcess] Unrecoverable error: RuntimeError('do not call blocking functions from the mainloop')
Traceback (most recent call last):
 File "/usr/local/lib/python3.9/site-packages/celery/worker/worker.py", line 203, in start
 self.blueprint.start(self)
 File "/usr/local/lib/python3.9/site-packages/celery/bootsteps.py", line 116, in start
 step.start(parent)
 File "/usr/local/lib/python3.9/site-packages/celery/bootsteps.py", line 365, in start
 return self.obj.start()
 File "/usr/local/lib/python3.9/site-packages/celery/worker/consumer/consumer.py", line 346, in start
 blueprint.start(self)
 File "/usr/local/lib/python3.9/site-packages/celery/bootsteps.py", line 116, in start
 step.start(parent)
 File "/usr/local/lib/python3.9/site-packages/celery/worker/consumer/consumer.py", line 788, in start
 c.loop(*c.loop_args())
 File "/usr/local/lib/python3.9/site-packages/celery/worker/loops.py", line 136, in synloop
 _loop_cycle()
 File "/usr/local/lib/python3.9/site-packages/celery/worker/loops.py", line 125, in _loop_cycle
 connection.drain_events(timeout=2.0)
 File "/usr/local/lib/python3.9/site-packages/kombu/connection.py", line 343, in drain_events
 return self.transport.drain_events(self.connection, **kwargs)
 File "/usr/local/lib/python3.9/site-packages/kombu/transport/pyamqp.py", line 171, in drain_events
 return connection.drain_events(**kwargs)
 File "/usr/local/lib/python3.9/site-packages/amqp/connection.py", line 526, in drain_events
 while not self.blocking_read(timeout):
 File "/usr/local/lib/python3.9/site-packages/amqp/connection.py", line 531, in blocking_read
 frame = self.transport.read_frame()
 File "/usr/local/lib/python3.9/site-packages/amqp/transport.py", line 297, in read_frame
 frame_header = read(7, True)
 File "/usr/local/lib/python3.9/site-packages/amqp/transport.py", line 632, in _read
 s = recv(n - len(rbuf))
 File "/usr/local/lib/python3.9/site-packages/eventlet/greenio/base.py", line 352, in recv
 return self._recv_loop(self.fd.recv, b'', bufsize, flags)
 File "/usr/local/lib/python3.9/site-packages/eventlet/greenio/base.py", line 346, in _recv_loop
 self._read_trampoline()
 File "/usr/local/lib/python3.9/site-packages/eventlet/greenio/base.py", line 314, in _read_trampoline
 self._trampoline(
 File "/usr/local/lib/python3.9/site-packages/eventlet/greenio/base.py", line 206, in _trampoline
 return trampoline(fd, read=read, write=write, timeout=timeout,
 File "/usr/local/lib/python3.9/site-packages/eventlet/hubs/__init__.py", line 157, in trampoline
 return hub.switch()
 File "/usr/local/lib/python3.9/site-packages/eventlet/hubs/hub.py", line 310, in switch
 return self.greenlet.switch()
 File "/usr/local/lib/python3.9/site-packages/eventlet/hubs/hub.py", line 362, in run
 self.wait(sleep_time)
 File "/usr/local/lib/python3.9/site-packages/eventlet/hubs/poll.py", line 80, in wait
 presult = self.do_poll(seconds)
 File "/usr/local/lib/python3.9/site-packages/eventlet/hubs/epolls.py", line 31, in do_poll
 return self.poll.poll(seconds)
 File "/usr/local/lib/python3.9/site-packages/celery/apps/worker.py", line 300, in _handle_request
 callback(worker)
 File "/usr/local/lib/python3.9/site-packages/celery/apps/worker.py", line 448, in on_SIGINT
 safe_say('worker: Hitting Ctrl+C again will initiate cold shutdown, terminating all running tasks!',
 File "/usr/local/lib/python3.9/site-packages/celery/apps/worker.py", line 82, in safe_say
 os.write(f.fileno(), f'\n{msg}\n'.encode())
 File "/usr/local/lib/python3.9/site-packages/eventlet/green/os.py", line 74, in write
 hubs.trampoline(fd, write=True)
 File "/usr/local/lib/python3.9/site-packages/eventlet/hubs/__init__.py", line 139, in trampoline
 raise RuntimeError('do not call blocking functions from the mainloop')
RuntimeError: do not call blocking functions from the mainloop
```


</details>

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Celery warm shutdown with celery>=5.5.0b3 and eventlet>=0.37.0 #10083

Checklist

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Optional Debugging Information

Related Issues and Possible Duplicates

Related Issues

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Uh oh!

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Celery warm shutdown with celery>=5.5.0b3 and eventlet>=0.37.0 #10083

Description

Checklist

Mandatory Debugging Information

Optional Debugging Information

Related Issues and Possible Duplicates

Related Issues

Possible Duplicates

Environment & Settings

Steps to Reproduce

Required Dependencies

Python Packages

Other Dependencies

Minimally Reproducible Test Case

Expected Behavior

Actual Behavior

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

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