u-boot/test/py/u_boot_spawn.py
Stephen Warren 93134e18e8 test/py: handle exceptions in console creation
u_boot_console.exec_attach.get_spawn() performs two steps:
1) Spawn a process to communicate with the serial console.
2) Reset the board so that U-Boot starts running from scratch.

Currently, if an exception happens in step (2), no cleanup is performed on
the process created in step (1). That process stays running and may e.g.
hold serial port locks, or simply continue to read data from the serial
port, thus preventing it from reaching any other process that attempts to
read from the same serial port later. While there is error cleanup code in
u_boot_console_base.ensure_spawned(), this is not triggered since the
exception prevents assignment to self.p there, and hence the exception
handler has no object to operate upon in cleanup_spawn().

Solve this by enhancing u_boot_console.exec_attach.get_spawn() to clean
up any objects it has created.

In theory, u_boot_spawn.Spawn's constructor has a similar issue, so fix
this too.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Simon Glass <sjg@chromium.org>
2016-02-15 20:58:29 +00:00

191 lines
5.4 KiB
Python

# Copyright (c) 2015-2016, NVIDIA CORPORATION. All rights reserved.
#
# SPDX-License-Identifier: GPL-2.0
# Logic to spawn a sub-process and interact with its stdio.
import os
import re
import pty
import signal
import select
import time
class Timeout(Exception):
"""An exception sub-class that indicates that a timeout occurred."""
pass
class Spawn(object):
"""Represents the stdio of a freshly created sub-process. Commands may be
sent to the process, and responses waited for.
"""
def __init__(self, args, cwd=None):
"""Spawn (fork/exec) the sub-process.
Args:
args: array of processs arguments. argv[0] is the command to
execute.
cwd: the directory to run the process in, or None for no change.
Returns:
Nothing.
"""
self.waited = False
self.buf = ''
self.logfile_read = None
self.before = ''
self.after = ''
self.timeout = None
(self.pid, self.fd) = pty.fork()
if self.pid == 0:
try:
# For some reason, SIGHUP is set to SIG_IGN at this point when
# run under "go" (www.go.cd). Perhaps this happens under any
# background (non-interactive) system?
signal.signal(signal.SIGHUP, signal.SIG_DFL)
if cwd:
os.chdir(cwd)
os.execvp(args[0], args)
except:
print 'CHILD EXECEPTION:'
import traceback
traceback.print_exc()
finally:
os._exit(255)
try:
self.poll = select.poll()
self.poll.register(self.fd, select.POLLIN | select.POLLPRI | select.POLLERR | select.POLLHUP | select.POLLNVAL)
except:
self.close()
raise
def kill(self, sig):
"""Send unix signal "sig" to the child process.
Args:
sig: The signal number to send.
Returns:
Nothing.
"""
os.kill(self.pid, sig)
def isalive(self):
"""Determine whether the child process is still running.
Args:
None.
Returns:
Boolean indicating whether process is alive.
"""
if self.waited:
return False
w = os.waitpid(self.pid, os.WNOHANG)
if w[0] == 0:
return True
self.waited = True
return False
def send(self, data):
"""Send data to the sub-process's stdin.
Args:
data: The data to send to the process.
Returns:
Nothing.
"""
os.write(self.fd, data)
def expect(self, patterns):
"""Wait for the sub-process to emit specific data.
This function waits for the process to emit one pattern from the
supplied list of patterns, or for a timeout to occur.
Args:
patterns: A list of strings or regex objects that we expect to
see in the sub-process' stdout.
Returns:
The index within the patterns array of the pattern the process
emitted.
Notable exceptions:
Timeout, if the process did not emit any of the patterns within
the expected time.
"""
for pi in xrange(len(patterns)):
if type(patterns[pi]) == type(''):
patterns[pi] = re.compile(patterns[pi])
tstart_s = time.time()
try:
while True:
earliest_m = None
earliest_pi = None
for pi in xrange(len(patterns)):
pattern = patterns[pi]
m = pattern.search(self.buf)
if not m:
continue
if earliest_m and m.start() >= earliest_m.start():
continue
earliest_m = m
earliest_pi = pi
if earliest_m:
pos = earliest_m.start()
posafter = earliest_m.end()
self.before = self.buf[:pos]
self.after = self.buf[pos:posafter]
self.buf = self.buf[posafter:]
return earliest_pi
tnow_s = time.time()
if self.timeout:
tdelta_ms = (tnow_s - tstart_s) * 1000
poll_maxwait = self.timeout - tdelta_ms
if tdelta_ms > self.timeout:
raise Timeout()
else:
poll_maxwait = None
events = self.poll.poll(poll_maxwait)
if not events:
raise Timeout()
c = os.read(self.fd, 1024)
if not c:
raise EOFError()
if self.logfile_read:
self.logfile_read.write(c)
self.buf += c
finally:
if self.logfile_read:
self.logfile_read.flush()
def close(self):
"""Close the stdio connection to the sub-process.
This also waits a reasonable time for the sub-process to stop running.
Args:
None.
Returns:
Nothing.
"""
os.close(self.fd)
for i in xrange(100):
if not self.isalive():
break
time.sleep(0.1)