From 3bd459b909a8a5007d069c5f4a59d00c91120e48 Mon Sep 17 00:00:00 2001
From: Ryan Kelly <ryan@rfk.id.au>
Date: Mon, 5 Sep 2011 10:47:03 +1000
Subject: [PATCH] esky.sudo: monitor helper process to avoid deadlock if it
 dies

---
 ChangeLog.txt          |  1 +
 esky/sudo/__init__.py  | 35 ++++++++++++++++++++++++++++++++++-
 esky/sudo/sudo_base.py |  2 +-
 3 files changed, 36 insertions(+), 2 deletions(-)

diff --git a/ChangeLog.txt b/ChangeLog.txt
index 757732c..058224a 100644
--- a/ChangeLog.txt
+++ b/ChangeLog.txt
@@ -7,6 +7,7 @@ v0.9.5
     * Clean up handling of unbuffered mode in py2exe.  (The old code
       never actually worked; the new code works most of the time but
       might give you the wrong mode if running from a partial update)
+    * esky.sudo: avoid deadlocking if the helper process dies.
 
 
 v0.9.4
diff --git a/esky/sudo/__init__.py b/esky/sudo/__init__.py
index 4ded796..791e6c7 100644
--- a/esky/sudo/__init__.py
+++ b/esky/sudo/__init__.py
@@ -32,6 +32,7 @@
 from __future__ import absolute_import
 
 import sys
+import time
 
 from esky.util import lazy_import
 
@@ -48,6 +49,14 @@ def pickle():
         import pickle
     return pickle
 
+@lazy_import
+def threading():
+    try:
+        import threading
+    except ImportError:
+        threading = None
+    return threading
+
 
 if sys.platform == "win32":
     @lazy_import
@@ -114,9 +123,33 @@ def start(self):
         (self.proc,self.pipe) = spawn_sudo(self)
         if self.proc.poll() is not None:
             raise RuntimeError("sudo helper process terminated unexpectedly")
-        if self.pipe.read() != b("READY"):
+        #  If threading is available, run a background thread to monitor
+        #  the sudo process.  If it dies, terminate things immediately.
+        if threading:
+            self._do_monitor_proc = True
+            monitor_thread = threading.Thread(target=self._monitor_proc)
+            monitor_thread.daemon = True
+            monitor_thread.start()
+        #  Try to read initialisation message from the pipe.
+        #  If this fails, the helper program must have died.
+        try:
+            msg = self.pipe.read()
+        except EOFError:
+            msg = b("")
+        if msg != b("READY"):
             self.close()
             raise RuntimeError("failed to spawn helper app")
+        if threading:
+            self._do_monitor_proc = False
+            monitor_thread.join()
+
+    def _monitor_proc(self):
+        while self._do_monitor_proc:
+            if self.proc.poll() is not None:
+                self.pipe._recover()
+                self.pipe.close()
+                break
+            time.sleep(0)
 
     def close(self):
         self.pipe.write(b("CLOSE"))
diff --git a/esky/sudo/sudo_base.py b/esky/sudo/sudo_base.py
index dbc1718..b712f01 100644
--- a/esky/sudo/sudo_base.py
+++ b/esky/sudo/sudo_base.py
@@ -99,7 +99,7 @@ def check_connection(self):
             self.connected = True
 
     def close(self):
-        pass
+        self.connected = False
 
     def read(self):
         """Read the next string from the pipe.