Problem with time.time() standing still

[Bob Cowdery]

Thanks Daniel, that's interesting. Unfortunately there is no sensible
code I can post because this only happens when I make a specific call
into the vendors SDK. I can exercise my own code in the extension
without a problem. The python test calling code is doing practically
nothing. I make 3 calls to the extension to set things going and then
loop every 5 seconds and print the time. I know Pythons own threading
model is cooperative because of the GIL and therefore one thread can hog
the show but I've never had issues with threads running in a C extension
messing up a Python thread. I really need to understand what mechanism
is at play here rather than work around it.

Bob

The time.clock() function does increment correctly. CPU is around 30%
On 05/05/2012 21:17, Danyel Lawson wrote:
> Add a time.sleep(0) call to all your loops. Multithreading in Python
> is a cooperative cross platform threading simulation if you have tight
> loops Python won't task switch until you make a system call.
> Potentially preventing internal library variables from being updated.
>
> Your five minute interval may be almost exactly how long it takes to
> process a flooded queue in a tight loop in your program and it may be
> why it continues to happen as the queue waits to fill again while
> processing happens.
>
> You can simulate the progression of time by overriding the time.time
> function by simply setting it to a function that just increments a
> module level or function property variable. You can also override the
> time.time function to return the posix time function's value to maybe
> get around whatever optimization is happening in the time.time
> function to pass back the same value.
>
> If you post your sample code that exhibits the same behavior it may be
> obvious to someone on the list as to what is the problem.
>
>
>
> On Sat, May 5, 2012 at 3:33 PM, Bob Cowdery <bob at bobcowdery.plus.com> wrote:
>> Hi all,
>>
>> I've been a long time user of Python and written many extensions but
>> this problem has me stumped.
>>
>> I've written a straight forward extension that wraps a vendors SDK for a
>> video capture card. All works well except that in the Python thread on
>> which I call the extension, after certain calls that I believe are using
>> DirectShow,  time stands still. The thread returns fine as the extension
>> does its stuff in its own threads. In all other respects the Python
>> thread seems unaffected but calls to time.time() always return the same
>> time which is usually several seconds in the past or future and always
>> has no fractional part. If I leave it long enough time will suddently
>> jump forward after a few minutes, then again after a few minutes more.
>>
>> I've never encountered this behaviour before and can't understand what
>> on earth is going on. If I call the 'C' time() function just the other
>> side of my call to the extension the time is ticking along fine. It's
>> just the one Python thread that is affected. If I call from the main
>> thread then the main thread is affected. The calling program I've used
>> to test this is just a few lines long.
>>
>> I believe the time function is a thin wrapper over the 'C' runtime so
>> its very odd that time only stands still on the Python side but not on
>> the 'C' side. As time is built in I've not looked at the code as its not
>> in the distribution. Don't know if it would help to do that.
>>
>> This also can affect the time.sleep() function making it return
>> immediately but that only seems to happen in my full application.
>>
>> Any ideas would be very greatly received.
>>
>> Bob
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