ec3po console and interpreter: Handle EOFError from the pipes.

EOF is expected sometimes upon shutdown, when one thread (console or
interpreter) manages to close its write side of a pipe before the other
thread receives the shutdown pipe unblocked notification.  EOF is now
considered another indication to shutdown.

BRANCH=none
BUG=b:79684405
TEST=With this change plus CL:1279145 to switch to threading, I am no
longer able to reproduce the formerly occasional EOFError tracebacks upon
shutdown, with either ctrl+c or SIGTERM.  Basic servod functionality
continues to work, including dut-control ec_uart_pty, servo_console_pty
(both tested with minicom), dut_i2c_mux, enable_ite_dfu, get_ite_chipid.
Testing performed with a servo_micro connected to an octopus_ite.  I tested
both without and with CL:1279145 i.e. both with subprocesses and with
threads (though I only ever encountered EOFError with the latter).

Change-Id: Iaa1ddc5f05a32ef806fa5f84d0ed0ad4739189ce
Signed-off-by: Matthew Blecker <matthewb@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1284509
Reviewed-by: Nick Sanders <nsanders@chromium.org>
Reviewed-by: Ruben Rodriguez Buchillon <coconutruben@chromium.org>

2 files changed, 70 insertions, 29 deletions

diff --git a/util/ec3po/console.py b/util/ec3po/console.py
index 61d2315e7c..66ed9ea53b 100755
--- a/util/ec3po/console.py
+++ b/util/ec3po/console.py
@@ -443,6 +443,9 @@ class Console(object):
     Returns:
       is_enhanced: A boolean indicating whether the EC responded to the
         interrogation correctly.
+
+    Raises:
+      EOFError: Allowed to propagate through from self.dbg_pipe.recv().
     """
     # Send interrogation byte and wait for the response.
     self.logger.debug('Performing interrogation.')
@@ -476,6 +479,10 @@ class Console(object):
 
     Args:
       byte: An integer representing the character received from the user.
+
+    Raises:
+      EOFError: Allowed to propagate through from self.CheckForEnhancedECImage()
+          i.e. from self.dbg_pipe.recv().
     """
     fd = self.master_pty
 
@@ -876,8 +883,15 @@ def StartLoop(console, command_active, shutdown_pipe=None):
               console.logger.debug('Input from user: %s, locked:%s',
                   str(line).strip(), command_active.value)
               for i in line:
-                # Handle each character as it arrives.
-                console.HandleChar(i)
+                try:
+                  # Handle each character as it arrives.
+                  console.HandleChar(i)
+                except EOFError:
+                  console.logger.debug(
+                      'ec3po console received EOF from dbg_pipe in HandleChar()'
+                      ' while reading console.master_pty')
+                  continue_looping = False
+                  break
             except OSError:
               console.logger.debug('Ptm read failed, probably user disconnect.')
 
@@ -889,34 +903,51 @@ def StartLoop(console, command_active, shutdown_pipe=None):
             console.logger.debug('Input from interface: %s, locked:%s',
                 str(line).strip(), command_active.value)
             for i in line:
-              # Handle each character as it arrives.
-              console.HandleChar(i)
+              try:
+                # Handle each character as it arrives.
+                console.HandleChar(i)
+              except EOFError:
+                console.logger.debug(
+                    'ec3po console received EOF from dbg_pipe in HandleChar()'
+                    ' while reading console.interface_pty')
+                continue_looping = False
+                break
 
         elif obj is console.cmd_pipe:
-          data = console.cmd_pipe.recv()
-          # Write it to the user console.
-          console.logger.debug('|CMD|-%s->\'%s\'',
-              ('u' if master_connected else '') +
-              ('i' if command_active.value else ''), data.strip())
-          if master_connected:
-            os.write(console.master_pty, data)
-          if command_active.value:
-            os.write(console.interface_pty, data)
-
-        elif obj is console.dbg_pipe:
-          data = console.dbg_pipe.recv()
-          if console.interrogation_mode == 'auto':
-            # Search look buffer for enhanced EC image string.
-            console.CheckBufferForEnhancedImage(data)
-          # Write it to the user console.
-          if len(data) > 1:
-            console.logger.debug('|DBG|-%s->\'%s\'',
+          try:
+            data = console.cmd_pipe.recv()
+          except EOFError:
+            console.logger.debug('ec3po console received EOF from cmd_pipe')
+            continue_looping = False
+          else:
+            # Write it to the user console.
+            console.logger.debug('|CMD|-%s->\'%s\'',
                 ('u' if master_connected else '') +
                 ('i' if command_active.value else ''), data.strip())
-          if master_connected:
-            os.write(console.master_pty, data)
-          if command_active.value:
-            os.write(console.interface_pty, data)
+            if master_connected:
+              os.write(console.master_pty, data)
+            if command_active.value:
+              os.write(console.interface_pty, data)
+
+        elif obj is console.dbg_pipe:
+          try:
+            data = console.dbg_pipe.recv()
+          except EOFError:
+            console.logger.debug('ec3po console received EOF from dbg_pipe')
+            continue_looping = False
+          else:
+            if console.interrogation_mode == 'auto':
+              # Search look buffer for enhanced EC image string.
+              console.CheckBufferForEnhancedImage(data)
+            # Write it to the user console.
+            if len(data) > 1:
+              console.logger.debug('|DBG|-%s->\'%s\'',
+                  ('u' if master_connected else '') +
+                  ('i' if command_active.value else ''), data.strip())
+            if master_connected:
+              os.write(console.master_pty, data)
+            if command_active.value:
+              os.write(console.interface_pty, data)
 
         elif obj is shutdown_pipe:
           console.logger.debug(
diff --git a/util/ec3po/interpreter.py b/util/ec3po/interpreter.py
index fd811716de..86272f6646 100644
--- a/util/ec3po/interpreter.py
+++ b/util/ec3po/interpreter.py
@@ -347,7 +347,11 @@ class Interpreter(object):
     self.dbg_pipe.send(data)
 
   def HandleUserData(self):
-    """Handle any incoming commands from the user."""
+    """Handle any incoming commands from the user.
+
+    Raises:
+      EOFError: Allowed to propagate through from self.cmd_pipe.recv().
+    """
     self.logger.log(1, 'Command data available.  Begin processing.')
     data = self.cmd_pipe.recv()
     # Process the command.
@@ -418,11 +422,17 @@ def StartLoop(interp, shutdown_pipe=None):
 
         # Handle any commands from the user.
         elif obj is interp.cmd_pipe:
-          interp.HandleUserData()
+          try:
+            interp.HandleUserData()
+          except EOFError:
+            interp.logger.debug(
+                'ec3po interpreter received EOF from cmd_pipe in '
+                'HandleUserData()')
+            continue_looping = False
 
         elif obj is shutdown_pipe:
           interp.logger.debug(
-              'ec3po console received shutdown pipe unblocked notification')
+              'ec3po interpreter received shutdown pipe unblocked notification')
           continue_looping = False
 
       for obj in writeable: