https://github.com/python/cpython/commit/8def603d853c7f5e4ff57f95de289f99e1943669
commit: 8def603d853c7f5e4ff57f95de289f99e1943669
branch: 3.14
author: Miss Islington (bot) <[email protected]>
committer: gpshead <[email protected]>
date: 2025-12-28T17:22:47Z
summary:

[3.14] gh-142195: Fixed Popen.communicate indefinite loops (GH-143203) (#143255)

gh-142195: Fixed Popen.communicate indefinite loops (GH-143203)

Changed condition to evaluate if timeout is less than or equals to 0. This is 
needed for simulated time environments such as Shadow where the time will match 
exactly on the boundary.

---------
(cherry picked from commit fa9a4254e81c0abcc3345021c45aaf5f788f9ea9)

Co-authored-by: Prithviraj Chaudhuri <[email protected]>
Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>

files:
A Misc/NEWS.d/next/Library/2025-12-27-00-14-56.gh-issue-142195.UgBEo5.rst
M Lib/subprocess.py

diff --git a/Lib/subprocess.py b/Lib/subprocess.py
index 6911cd8e85973d..578d7b95d05d7b 100644
--- a/Lib/subprocess.py
+++ b/Lib/subprocess.py
@@ -2141,7 +2141,7 @@ def _communicate(self, input, endtime, orig_timeout):
 
                 while selector.get_map():
                     timeout = self._remaining_time(endtime)
-                    if timeout is not None and timeout < 0:
+                    if timeout is not None and timeout <= 0:
                         self._check_timeout(endtime, orig_timeout,
                                             stdout, stderr,
                                             skip_check_and_raise=True)
diff --git 
a/Misc/NEWS.d/next/Library/2025-12-27-00-14-56.gh-issue-142195.UgBEo5.rst 
b/Misc/NEWS.d/next/Library/2025-12-27-00-14-56.gh-issue-142195.UgBEo5.rst
new file mode 100644
index 00000000000000..b2b1ffe7225bd7
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-12-27-00-14-56.gh-issue-142195.UgBEo5.rst
@@ -0,0 +1 @@
+Updated timeout evaluation logic in :mod:`subprocess` to be compatible with 
deterministic environments like Shadow where time moves exactly as requested.

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