python / python/cpython

`select.BaseSelector.select` do not conform to documentation with regard to signal handling

Open
#120,001 0 comments 0 reactions 0 assignees View on GitHub

Nobody has claimed this yet.

topic-socket type-bug
Dominant language
Python
Stars
77.2k
Forks
36k
PR merge metrics
PR metrics pending

Description

Bug report

Bug description:

According to documentation in https://docs.python.org/3/library/selectors.html#selectors.BaseSelector.select:

      .. versionchanged:: 3.5
         The selector is now retried with a recomputed timeout when interrupted
         by a signal if the signal handler did not raise an exception (see
         :pep:`475` for the rationale), instead of returning an empty list
         of events before the timeout.

However, as of writing this issue, selectors.SelectSelector.select and co can't differentiate between InterruptedError and timeout, as this exceptions is caught in in those methods.

While select.select shouldn't raise InterruptedError, such exception could be raised in a signal handler, therefore causing selectors.SelectSelector.select to return an empty list (instead of the raised exception), as-if it was a timeout.

The behaviour that I would expect has been implemented in https://github.com/python/cpython/commit/f70e1ca0fc30426d12aa8fc6684764ee11a66777, however it has been reverted in a following commit https://github.com/python/cpython/commit/90ecfe65e68#diff-671465c62a2c7c951b397550dc8f2f1c03860af4c089299e6edea29347cf6018 . It is unclear to me if it is an oversight, or if this revert was expected.

I only tested this for selectors.SelectSelector, but looking at the sources, I would expect the same behaviour exist for all select.*Selector classes

CPython versions tested on:

3.12, CPython main branch

Operating systems tested on:

Linux

Linked PRs
  • gh-120002

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with selectors.SelectSelector.select and compare its handling with the documented BaseSelector.select behavior for signal interruptions. Check the linked PR gh-120002 and the referenced commits to understand the intended resolution, then verify whether the select.*Selector classes need consistent treatment and regression coverage.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
operating-systems
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
25/100

Get new issues in your inbox

A short digest of beginner-friendly GitHub issues.