Update comments

Author: giampaolo

Lib/subprocess.py

@@ -2152,8 +2152,9 @@ def _wait_kqueue(self, timeout):
                     events = kq.control([kev], 1, timeout)  # wait
                 except OSError as err:  # should never happen
                     return False
-                if not events:
-                    raise TimeoutExpired(self.args, timeout)
+                else:
+                    if not events:
+                        raise TimeoutExpired(self.args, timeout)
                 return True
             finally:
                 kq.close()
@@ -2177,8 +2178,8 @@ def _wait(self, timeout):
                 # Try efficient wait first.
                 if self._wait_pidfd(timeout) or self._wait_kqueue(timeout):
                     # Process is gone. At this point os.waitpid(pid, 0)
-                    # will return immediately, but in very rare races
-                    # the PID may have been reused.
+                    # will return immediately, but in rare races (e.g.
+                    # long running processes) the PID may have been reused.
                     # os.waitpid(pid, WNOHANG) ensures we attempt a
                     # non-blocking reap without blocking indefinitely.
                     with self._waitpid_lock:

Lib/test/test_subprocess.py

@@ -4105,8 +4105,8 @@ class FastWaitTestCase(BaseTestCase):
     CAN_USE_KQUEUE = subprocess._CAN_USE_KQUEUE
 
     def assert_fast_waitpid_error(self, patch_point):
-        # Emulate a case where pidfd_open() (Linux) or kqueue()
-        # (BSD/macOS) fails. Busy-poll wait should be used as fallback.
+        # Emulate a case where pidfd_open() or kqueue() fails.
+        # Busy-poll wait should be used as fallback.
         exc = OSError(errno.EMFILE, os.strerror(errno.EMFILE))
         with mock.patch(patch_point, side_effect=exc) as m:
             p = subprocess.Popen([sys.executable,