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

prithviraj-chaudhuri · blurb-it[bot] · miss-islington · commit 7a6dfaaded26 · 2025-12-28T16:57:57.000Z
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 fa9a425) Co-authored-by: Prithviraj Chaudhuri <p.chaudhuri1993@gmail.com> Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>
diff --git 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
@@ -0,0 +1 @@
+Updated timeout evaluation logic in :mod:`subprocess` to be compatible with deterministic environments like Shadow where time moves exactly as requested.

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1 @@`
	`1`	+Updated timeout evaluation logic in :mod:`subprocess` to be compatible with deterministic environments like Shadow where time moves exactly as requested.