Using ThreadPoolTaskSupport causes test to hang

[scabug]

While Joel and I bootstrapped and tested Scala on Avian, we both encountered that the test suite hangs in test/files/scalacheck/parallel-collections.

This seems to be an issue on Scala's side: Joel discovered that the same also happens on Hotspot when using ThreadPoolTaskSupport:

Nevermind, I figured it out.  There's a lovely bit of code in   scala/collection/parallel/package.scala:

{code}
private[parallel] def getTaskSupport: TaskSupport =
  if (scala.util.Properties.isJavaAtLeast("1.6")) {
    val vendor = scala.util.Properties.javaVmVendor
    if ((vendor contains "Oracle") || (vendor contains "Sun") || (vendor contains "Apple")) new ForkJoinTaskSupport
    else new ThreadPoolTaskSupport
  } else new ThreadPoolTaskSupport
{code}

If I change that to just
{code}
       private[parallel] def getTaskSupport: TaskSupport = new ForkJoinTaskSupport
{code}

the parallel-collections test passes on Avian and HotSpot. However, if I change it to

{code}
       private[parallel] def getTaskSupport: TaskSupport = new ThreadPoolTaskSupport
{code}

it hangs on both Avian and HotSpot.  In other words, the test simply won't complete when using ThreadPoolTaskSupport, regardless of the VM, which means the test can only pass if the VM vendor is Oracle, Sun, or Apple.

Ouch.

It looks like ThreadPoolTaskSupport is broken on all VMs.

Thread on the Avian mailing list: https://groups.google.com/d/msg/avian/Hugny4JcnDw/shb3r-3BOR8J

Thread on the Scala mailing list: https://groups.google.com/d/msg/scala-internals/7N-7HzoH8tM/9mx4bZd4JfoJ

Joel's thread dump is attached.

I'll open a separate issue for the insufficient task support detection mechanism.

[scabug]

Imported From: https://issues.scala-lang.org/browse/SI-7236?orig=1
Reporter: @soc
Affected Versions: 2.11.0-M1
Attachments:

• parallel-collections-trace.txt (created on Mar 9, 2013 2:52:21 PM UTC, 72398 bytes)

[scabug]

@soc said:
IBM J9 also hangs with ThreadPoolTaskSupport.

[scabug]

@soc said:
Deprecate ThreadPoolTaskSupport and friends.

2.11: scala/scala#2251

[scabug]

@JamesIry said:
I'm leaving open for 2.12 to remind us to delete.

[scabug]

@soc said (edited on Jun 9, 2013 7:42:17 PM UTC):
Merged in scala/scala@27f3a89

I'm closing this, because I created an explicit new ticket for removals in 2.12: #7566