hi,
> Hey Yamamoto,
>
> Sorry for the delay, I finally set up my NetBSD environment and tested
> this script. You're right, but NetBSD will actually return an error on
> clock_gettime because of this argument difference. Thus, NetBSD will
> continue to use time.time(), which is as expected.
it returns an error because of a different value of CLOCK_MONOTONIC.
(it's 3 on NetBSD)
however, it's too fragile to pass "random" arguments to a system call
and expect it detect and return errors.
how about having an explicit platform check?
>
> I can add NetBSD functionality such that clock_gettime with
> CLOCK_MONOTONIC can also be used for NetBSD as well. Lemme know!
thanks. please if you can. otherwise i can take a look later.
btw, docstring of msec() needs an update.
YAMAMOTO Takashi
>
> Ryan
>
> On 5/31/14 11:14 PM, "YAMAMOTO Takashi" <yamam...@valinux.co.jp> wrote:
>
>>> 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 <wr...@nicira.com>
>>>
>>> ---
>>> v2: Pre-load librt.so.1 library instead of loading at every function
>>> call. Use only CLOCK_MONOTONIC for consistency with OVS C library.
>>> v3: Edit commit message, remove if-linux check
>>> ---
>>> python/ovs/timeval.py | 34 +++++++++++++++++++++++++++++++++-
>>> 1 file changed, 33 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/python/ovs/timeval.py b/python/ovs/timeval.py
>>> index ba0e54e..f2681ac 100644
>>> --- a/python/ovs/timeval.py
>>> +++ b/python/ovs/timeval.py
>>> @@ -12,13 +12,45 @@
>>> # See the License for the specific language governing permissions and
>>> # limitations under the License.
>>>
>>> +import ctypes
>>> +import sys
>>> import time
>>>
>>> +LIBRT = 'librt.so.1'
>>> +CLOCK_MONOTONIC = 1
>>> +
>>> +class timespec(ctypes.Structure):
>>> + _fields_ = [
>>> + ('tv_sec', ctypes.c_long),
>>
>>on NetBSD, timespec.tv_sec is int64_t, not long.
>>
>>YAMAMOTO Takashi
>>
>>> + ('tv_nsec', ctypes.c_long),
>>> + ]
>>> +
>>> +try:
>>> + librt = ctypes.CDLL(LIBRT)
>>> + clock_gettime = librt.clock_gettime
>>> + clock_gettime.argtypes = [ctypes.c_int, ctypes.POINTER(timespec)]
>>> +except:
>>> + # Librt shared library could not be loaded
>>> + librt = None
>>> +
>>> +def monotonic():
>>> + if not librt:
>>> + return time.time()
>>> +
>>> + t = timespec()
>>> + if clock_gettime(CLOCK_MONOTONIC, ctypes.pointer(t)) == 0:
>>> + return t.tv_sec + t.tv_nsec * 1e-9
>>> + # Kernel does not support CLOCK_MONOTONIC
>>> + return time.time()
>>> +
>>> +# Use time.monotonic() if Python version >= 3.3
>>> +if not hasattr(time, 'monotonic'):
>>> + time.monotonic = monotonic
>>>
>>> def msec():
>>> """Returns the current time, as the amount of time since the
>>>epoch, in
>>> milliseconds, as a float."""
>>> - return time.time() * 1000.0
>>> + return time.monotonic() * 1000.0
>>>
>>>
>>> def postfork():
>>> --
>>> 1.7.9.5
>
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