Project Loom VirtualThreads hang

[robert engels]

Btw, in regards to the timings here, this was for the SpinTest.

> On Dec 28, 2022, at 7:07 AM, Robert Engels <rengels at ix.netcom.com> wrote:
> 
> Alan,
> 
> I tested with JDK 20 and both the VThreadTest and SpinTest complete successfully using Thread.yield!
> 
> Surprisingly, it is slower than using LockSupport.parkNanos(1) - 14 secs vs 7 secs  I am not sure this makes sense - as conceptually a thread yield should be at least as efficient as a 0 time sleep - and probably more efficient.  
> 
>> On Dec 28, 2022, at 6:51 AM, Robert Engels <rengels at ix.netcom.com> wrote:
>> 
>> 
>> Alex,
>> 
>> You write:
>> 
>>> I won't go into detail, but the producers not synchronizing between themselves leads to hangs.
>> 
>> 
>> Can you explain? Im fairly certain the producers do valid synchronization. As I said, using native threads the code runs to completion fine  
>> 
>> Now that I understand the issue I was able to reproduce the issue very simply without any queues. See SpinTest posted to the project. The “starver” thread fails to make any progress - this should not be possible is Thread.yield() was fair. 
>> 
>>> On Dec 27, 2022, at 11:15 PM, Alex Otenko <oleksandr.otenko at gmail.com> wrote:
>>> I won't go into detail, but the producers not synchronizing between themselves leads to hangs.