From: Prithviraj Chaudhuri <p.chaudhuri1993@gmail.com>
Date: Sun, 28 Dec 2025 16:57:44 +0000 (-0500)
Subject: gh-142195: Fixed Popen.communicate indefinite loops (GH-143203)
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=fa9a4254e81c0abcc3345021c45aaf5f788f9ea9;p=thirdparty%2FPython%2Fcpython.git

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.

---------

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

diff --git a/Lib/subprocess.py b/Lib/subprocess.py
index 17333d8c0225..3cebd7883fcf 100644
--- a/Lib/subprocess.py
+++ b/Lib/subprocess.py
@@ -2140,7 +2140,7 @@ class Popen:
 
                 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 000000000000..b2b1ffe7225b
--- /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.