Fix issue 356 - Process.parent: make parent's creation time <= self

3 files changed, 17 insertions, 3 deletions

diff --git a/CREDITS b/CREDITS
index 21f336cf..67c22016 100644
--- a/CREDITS
+++ b/CREDITS
@@ -146,3 +146,7 @@ I: 323
 N: André Oriani
 E: aoriani@gmail.com
 I: 361
+
+N: clackwell
+E: clackwell@gmail.com
+I: 356
diff --git a/HISTORY b/HISTORY
index 3304078a..0d1d833c 100644
--- a/HISTORY
+++ b/HISTORY
@@ -42,6 +42,8 @@ BUG FIXES
          kvm_open(3) not being called. (patch by Jean Sebastien)
  * #338: [Linux] disk_io_counters() fails to find some disks.
  * #353: [OSX] get_users() returns an empty list on OSX 10.8.
+ * #356: Process.parent now checks whether parent PID has been reused in which
+         case returns None.
  * #365: Process wait() and set_nice() methods should check PID has not been
          reused by another process.
 
diff --git a/psutil/__init__.py b/psutil/__init__.py
index c666eeb7..e6eff016 100644
--- a/psutil/__init__.py
+++ b/psutil/__init__.py
@@ -125,6 +125,7 @@ class Process(object):
 
         The only exceptions for which process identity is pre-emptively
         checked are:
+         - parent
          - get_children()
          - set_nice()
          - suspend()
@@ -227,14 +228,18 @@ class Process(object):
         return retdict
 
     @property
+    @_assert_is_running
     def parent(self):
-        """Return the parent process as a Process object. If no parent
-        pid is known return None.
+        """Return the parent process as a Process object.
+        If no parent is known return None.
         """
         ppid = self.ppid
         if ppid is not None:
             try:
-                return Process(ppid)
+                parent = Process(ppid)
+                if parent.create_time <= self.create_time:
+                    return parent
+                # ...else ppid has been reused by another process
             except NoSuchProcess:
                 pass
 
@@ -252,6 +257,9 @@ class Process(object):
         # change to 1 (init) in case this process turns into a zombie:
         # https://code.google.com/p/psutil/issues/detail?id=321
         # http://stackoverflow.com/questions/356722/
+
+        # XXX should we check creation time here rather than in
+        # Process.parent?
         if os.name == 'posix':
             return self._platform_impl.get_process_ppid()
         else: