ec3po: quit console & interpreter loop when parent process changes.

Right now, when the parent process dies ungracefully - say kill -9 -
then the interpreter, and console processes remain active.
This leads to bugs in the servod implementation from holding on to
sockets, to reinitialization issues of a new instance on the same servod
device.
This change quits the loops inside console & interpreter as soon as the
parent pid changes (i.e. the parent dies).

BRANCH=None
BUG=chromium:841121
TEST=sudo servod -b soraka
ps aux | grep servod
>xxxxx servod
>xxxxy servod
>xxxyx servod
>xxxaa grep servod
sudo kill -9 xxxxx
ps aux | grep servod
>xxxab grep servod

Before this, just kill -9 on the main thread did not take the children
with it.

Change-Id: I547bd92bf8732bff8aef2b72840417c809ba27d6
Signed-off-by: Ruben Rodriguez Buchillon <coconutruben@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1186299
Reviewed-by: Aseda Aboagye <aaboagye@chromium.org>
Reviewed-by: Nick Sanders <nsanders@chromium.org>

2 files changed, 10 insertions, 6 deletions

diff --git a/util/ec3po/console.py b/util/ec3po/console.py
index 608e1b7cba..0b2b586252 100755
--- a/util/ec3po/console.py
+++ b/util/ec3po/console.py
@@ -817,13 +817,14 @@ def IsPrintable(byte):
   """
   return byte >= ord(' ') and byte <= ord('~')
 
-def StartLoop(console, command_active):
+def StartLoop(console, command_active, ppid = os.getppid()):
   """Starts the infinite loop of console processing.
 
   Args:
     console: A Console object that has been properly initialzed.
     command_active: multiprocessing.Value indicating if servod owns
         the console, or user owns the console. This prevents input collisions.
+    ppid: original parent pid to stop loop when parent dies.
   """
   console.logger.debug('Console is being served on %s.', console.user_pty)
   console.logger.debug('Console master is on %s.', console.master_pty)
@@ -836,7 +837,7 @@ def StartLoop(console, command_active):
     ep = select.epoll()
     ep.register(console.master_pty, select.EPOLLHUP)
 
-    while True:
+    while os.getppid() == ppid:
       # Check to see if pts is connected to anything
       events = ep.poll(0)
       master_connected = not events
@@ -980,7 +981,7 @@ def main(argv):
 
   # Spawn an interpreter process.
   itpr_process = multiprocessing.Process(target=interpreter.StartLoop,
-                                         args=(itpr,))
+                                         args=(itpr,os.getpid()))
   # Make sure to kill the interpreter when we terminate.
   itpr_process.daemon = True
   # Start the interpreter.
diff --git a/util/ec3po/interpreter.py b/util/ec3po/interpreter.py
index 9a0880f49c..6de8ff7a43 100644
--- a/util/ec3po/interpreter.py
+++ b/util/ec3po/interpreter.py
@@ -374,7 +374,7 @@ def Crc8(data):
   return crc >> 8
 
 
-def StartLoop(interp):
+def StartLoop(interp, ppid = os.getppid()):
   """Starts an infinite loop of servicing the user and the EC.
 
   StartLoop checks to see if there are any commands to process, processing them
@@ -389,10 +389,13 @@ def StartLoop(interp):
 
   Args:
     interp: An Interpreter object that has been properly initialised.
+    ppid: original parent pid to stop loop when parent dies.
   """
   try:
-    while True:
-      readable, writeable, _ = select.select(interp.inputs, interp.outputs, [])
+    while os.getppid() == ppid:
+      # Timeout every 100ms to catch if the parent has died.
+      readable, writeable, _ = select.select(interp.inputs, interp.outputs, [],
+                                             0.1)
 
       for obj in readable:
         # Handle any debug prints from the EC.