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Python's time.time() function uses the system wall clock. However, if NTP resets the wall clock to be a time in the past, then this causes any applications that poll block based on time, such as ovs-xapi-sync, to poll block indefinitely since the time is unexpectedly negative. This patch fixes the issue by using time.monotonic() if Python's version >= 3.3. Otherwise, the timeval module calls out to the librt C shared library and uses the clock_gettime function with CLOCK_MONOTONIC. Note this is only enabled on Linux-based platforms. This has been tested on Ubuntu 12.04 and Redhat 6.4. Bug #1189434 Signed-off-by: Ryan Wilson <wryan@nicira.com> Acked-by: Ethan Jackson <ethan@nicira.com>
59 lines
1.6 KiB
Python
59 lines
1.6 KiB
Python
# Copyright (c) 2009, 2010 Nicira, Inc.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at:
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import ctypes
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import sys
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import time
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LIBRT = 'librt.so.1'
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CLOCK_MONOTONIC = 1
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class timespec(ctypes.Structure):
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_fields_ = [
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('tv_sec', ctypes.c_long),
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('tv_nsec', ctypes.c_long),
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]
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try:
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librt = ctypes.CDLL(LIBRT)
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clock_gettime = librt.clock_gettime
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clock_gettime.argtypes = [ctypes.c_int, ctypes.POINTER(timespec)]
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except:
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# Librt shared library could not be loaded
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librt = None
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def monotonic():
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if not librt:
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return time.time()
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t = timespec()
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if clock_gettime(CLOCK_MONOTONIC, ctypes.pointer(t)) == 0:
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return t.tv_sec + t.tv_nsec * 1e-9
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# Kernel does not support CLOCK_MONOTONIC
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return time.time()
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# Use time.monotonic() if Python version >= 3.3
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if not hasattr(time, 'monotonic'):
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time.monotonic = monotonic
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def msec():
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"""Returns the current time, as the amount of time since the epoch, in
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milliseconds, as a float."""
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return time.monotonic() * 1000.0
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def postfork():
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# Just a stub for now
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pass
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