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# Copyright (c) 2010, 2011 Nicira Networks
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at:
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import atexit
import os
import signal
import ovs.vlog
_hooks = []
vlog = ovs.vlog.Vlog("fatal-signal")
def add_hook(hook, cancel, run_at_exit):
_init()
_hooks.append((hook, cancel, run_at_exit))
def fork():
"""Clears all of the fatal signal hooks without executing them. If any of
the hooks passed a 'cancel' function to add_hook(), then those functions
will be called, allowing them to free resources, etc.
Following a fork, one of the resulting processes can call this function to
allow it to terminate without calling the hooks registered before calling
this function. New hooks registered after calling this function will take
effect normally."""
global _hooks
for hook, cancel, run_at_exit in _hooks:
if cancel:
cancel()
_hooks = []
_added_hook = False
_files = {}
def add_file_to_unlink(file):
"""Registers 'file' to be unlinked when the program terminates via
sys.exit() or a fatal signal."""
global _added_hook
if not _added_hook:
_added_hook = True
add_hook(_unlink_files, _cancel_files, True)
_files[file] = None
def remove_file_to_unlink(file):
"""Unregisters 'file' from being unlinked when the program terminates via
sys.exit() or a fatal signal."""
if file in _files:
del _files[file]
def unlink_file_now(file):
"""Like fatal_signal_remove_file_to_unlink(), but also unlinks 'file'.
Returns 0 if successful, otherwise a positive errno value."""
error = _unlink(file)
if error:
vlog.warn("could not unlink \"%s\" (%s)" % (file, os.strerror(error)))
remove_file_to_unlink(file)
return error
def _unlink_files():
for file_ in _files:
_unlink(file_)
def _cancel_files():
global _added_hook
global _files
_added_hook = False
_files = {}
def _unlink(file_):
try:
os.unlink(file_)
return 0
except OSError, e:
return e.errno
def _signal_handler(signr, _):
_call_hooks(signr)
# Re-raise the signal with the default handling so that the program
# termination status reflects that we were killed by this signal.
signal.signal(signr, signal.SIG_DFL)
os.kill(os.getpid(), signr)
def _atexit_handler():
_call_hooks(0)
recurse = False
def _call_hooks(signr):
global recurse
if recurse:
return
recurse = True
for hook, cancel, run_at_exit in _hooks:
if signr != 0 or run_at_exit:
hook()
_inited = False
def _init():
global _inited
if not _inited:
_inited = True
for signr in (signal.SIGTERM, signal.SIGINT,
signal.SIGHUP, signal.SIGALRM):
if signal.getsignal(signr) == signal.SIG_DFL:
signal.signal(signr, _signal_handler)
atexit.register(_atexit_handler)
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