Hi Robbin,

Thanks for looking at this.

On 19/05/2017 6:36 PM, Robbin Ehn wrote:
Hi David,

On 05/18/2017 08:25 AM, David Holmes wrote:
Bug: https://bugs.openjdk.java.net/browse/JDK-8174231


Build-related: http://cr.openjdk.java.net/~dholmes/8174231/webrev.top/
hotspot: http://cr.openjdk.java.net/~dholmes/8174231/webrev.hotspot/

I like this, with neg delta of 700 loc, nice!

It's hard to see if you broken anything, since you combined 4 separate implementation into 1.

Well not really. As I said this is basically a cleaned up version of the Linux code. The BSD and AIX versions were already based on earlier versions of the Linux code, minus the proper handling of CLOCK_MONOTONIC and absolute timeouts.

I guess you have tested this proper?

Only JPRT so far. I should have mentioned that I'm not expecting this to be reviewed in pushed within a couple of days, so some refinements and continual testing will occur.

What stands out in os_posix.cpp is the
static void to_abstime(timespec* abstime, jlong timeout, bool isAbsolute)

The ifdef scopes of SUPPORTS_CLOCK_MONOTONIC is large and calculations are repeated 3 times.

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:

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.


      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 {
      struct timeval now;
      int status = gettimeofday(&now, NULL);
      assert(status == 0, "gettimeofday");
calc_time(abstime, timeout, isAbsolute, now.tv_sec, now.tv_usec, MICROUNITS);

Thanks for fixing this!


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