I'm happy with this. It's been merged.
Ethan
On Fri, May 30, 2014 at 3:38 PM, Ryan Wilson <wr...@nicira.com> 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),
> + ('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
>
> _______________________________________________
> dev mailing list
> dev@openvswitch.org
> http://openvswitch.org/mailman/listinfo/dev
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