Merged revisions 78777,78787,78790 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/trunk

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  r78777 | florent.xicluna | 2010-03-08 00:49:03 +0100 (lun, 08 mar 2010) | 4 lines

  Backport the Popen.poll() protection from subprocess to multiprocessing. See #1731717.
  It should fix transient failures on test_multiprocessing.
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  r78787 | florent.xicluna | 2010-03-08 08:21:16 +0100 (lun, 08 mar 2010) | 2 lines

  Don't fail on a debug() statement, if the worker PID is (still) None.
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  r78790 | florent.xicluna | 2010-03-08 12:01:39 +0100 (lun, 08 mar 2010) | 2 lines

  On finalize, don't try to join not started process.
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diff --git a/Lib/multiprocessing/forking.py b/Lib/multiprocessing/forking.py
index 3c0f568..5d66fa3 100644
--- a/Lib/multiprocessing/forking.py
+++ b/Lib/multiprocessing/forking.py
@@ -104,7 +104,12 @@
 
         def poll(self, flag=os.WNOHANG):
             if self.returncode is None:
-                pid, sts = os.waitpid(self.pid, flag)
+                try:
+                    pid, sts = os.waitpid(self.pid, flag)
+                except os.error:
+                    # Child process not yet created. See #1731717
+                    # e.errno == errno.ECHILD == 10
+                    return None
                 if pid == self.pid:
                     if os.WIFSIGNALED(sts):
                         self.returncode = -os.WTERMSIG(sts)