ec3po: console: Detect HUP from user console

ec3po writes to the user pty, which may or may not be open.
Since ptys have limited buffer space, we need to avoid
writing to them if they will never be drained.

ec3po now looks for HUP to indicate whether the pts is opened
or closed, and reads/writes accordingly.

BRANCH=None
BUG=b:76111225
TEST=dut-control ec_board:fizz x 400

Change-Id: Icbecb2e42b261659a006eb1b9fc6dd73490a2218
Signed-off-by: Nick Sanders <nsanders@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1014792
Reviewed-by: Aseda Aboagye <aaboagye@chromium.org>

1 files changed, 45 insertions, 13 deletions

diff --git a/util/ec3po/console.py b/util/ec3po/console.py
index cebad3033d..608e1b7cba 100755
--- a/util/ec3po/console.py
+++ b/util/ec3po/console.py
@@ -24,6 +24,7 @@ import re
 import select
 import stat
 import sys
+import traceback
 
 import interpreter
 
@@ -829,23 +830,43 @@ def StartLoop(console, command_active):
   console.logger.debug('Command interface is being served on %s.',
       console.interface_pty)
   console.logger.debug(console)
+
   try:
+    # This checks for HUP to indicate if the user has connected to the pty.
+    ep = select.epoll()
+    ep.register(console.master_pty, select.EPOLLHUP)
+
     while True:
+      # Check to see if pts is connected to anything
+      events = ep.poll(0)
+      master_connected = not events
+
       # Check to see if pipes or the console are ready for reading.
-      read_list = [console.master_pty, console.interface_pty,
+      read_list = [console.interface_pty,
                    console.cmd_pipe, console.dbg_pipe]
-      ready_for_reading = select.select(read_list, [], [])[0]
+      if master_connected:
+        read_list.append(console.master_pty)
+
+      # Check if any input is ready, or wait for .1 sec and re-poll if
+      # a user has connected to the pts.
+      select_output = select.select(read_list, [], [], .1)
+      if not select_output:
+        continue
+      ready_for_reading = select_output[0]
 
       for obj in ready_for_reading:
         if obj is console.master_pty and not command_active.value:
           # Convert to bytes so we can look for non-printable chars such as
           # Ctrl+A, Ctrl+E, etc.
-          line = bytearray(os.read(console.master_pty, CONSOLE_MAX_READ))
-          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:
+            line = bytearray(os.read(console.master_pty, CONSOLE_MAX_READ))
+            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)
+          except OSError:
+            console.logger.debug('Ptm read failed, probably user disconnect.')
 
         if obj is console.interface_pty and command_active.value:
           # Convert to bytes so we can look for non-printable chars such as
@@ -860,8 +881,11 @@ def StartLoop(console, command_active):
         elif obj is console.cmd_pipe:
           data = console.cmd_pipe.recv()
           # Write it to the user console.
-          console.logger.debug('|CMD|->\'%s\'', data.strip())
-          os.write(console.master_pty, data)
+          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)
 
@@ -872,16 +896,24 @@ def StartLoop(console, command_active):
             console.CheckBufferForEnhancedImage(data)
           # Write it to the user console.
           if len(data) > 1:
-            console.logger.debug('|DBG|->\'%s\'', data.strip())
-          os.write(console.master_pty, data)
+            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)
 
       while not console.oobm_queue.empty():
         console.logger.debug('OOBM queue ready for reading.')
         console.ProcessOOBMQueue()
-
+  except KeyboardInterrupt:
+    pass
+  except:
+    traceback.print_exc()
   finally:
+    # Unregister poll.
+    ep.unregister(console.master_pty)
     # Close pipes.
     console.dbg_pipe.close()
     console.cmd_pipe.close()