(10) (M) RFR: 8174231: Factor out and share PlatformEvent and Parker code for POSIX systems

[Robbin Ehn]

On 05/19/2017 11:07 AM, David Holmes wrote:
> 
> They have to be as there are three cases:
> 
> 1. Relative wait using CLOCK_MONOTONIC
> 2. Relative wait using gettimeofday()
> 3. Absolute wait using gettimeofday()
> 
>> Please consider something like:
>>
>> #ifdef SUPPORTS_CLOCK_MONOTONIC
>>    if (_use_clock_monotonic_condattr  && !isAbsolute) { // Why aren't we using this when not isAbsolute is set?
>>                                 // I suggest removing that check from this if and use monotonic for that also.
> 
> Absolute waits have to be based on wall-clock time and follow any adjustments made to wall clock time. In contrast relative waits should never be affected by wall-clock 
> time adjustments hence the use of CLOCK_MONOTONIC when available.
> 
> In Java the relative timed-waits are:
> - Thread.sleep(ms)
> - Object.wait(ms)/wait(ms,ns)
> - LockSupport.parkNanos(ns) (and all the j.u.c blocking methods built on top of it)
> 
> While the only absolute timed-wait we have is the LockSupport.parkUntil method(s).
> 
> Hope that clarifies things.

Yes thanks!

But you can still re-factoring to something similar to what I suggested and two of the calculation should be the same just ns vs us, correct?
Leaving the if statement with the "!isAbsolute" check, in my head calc_time is something like:

void calc_time(...) {
   if (isAbsolute) {
     calc_abs_time(...);
   } else {
     calc_rel_time(...);
   }
}

I do not see a problem with this, only better readability?

/Robbin

> 
> Thanks,
> David
> -----
> 
>>       struct timespec now;
>>       int status = _clock_gettime(CLOCK_MONOTONIC, &now);
>>       assert_status(status == 0, status, "clock_gettime");
>>       calc_time(abstime, timeout, isAbsolute, now.tv_sec, now.tv_nsec, NANOUNITS);
>>    } else {
>> #else
>>    {
>> #endif
>>       struct timeval now;
>>       int status = gettimeofday(&now, NULL);
>>       assert(status == 0, "gettimeofday");
>>       calc_time(abstime, timeout, isAbsolute, now.tv_sec, now.tv_usec, MICROUNITS);
>>    }
>> #endif
>>
>> Thanks for fixing this!
>>
>> /Robbin