RFR: 8154715: Missing destructor and/or TLS clearing calls for terminating threads

[Stefan Karlsson]

Hi David,

On 10/05/16 02:33, David Holmes wrote:
> Okay here is version 2:
>
> http://cr.openjdk.java.net/~dholmes/8154715/webrev.v2/
>
> Lots of cosmetic changes but only a couple of functional ones:
>
> -  After thread->run() returns we clear the TLS by calling 
> clear_thread_current(), but only for threads where it has not already 
> been cleared - as those threads may already have been deleted so we 
> can't dereference 'thread'
>
> - No asynchronous thread deletion is permitted, and we avoid races 
> with VM termination. This means the VMThread no longer gets deleted - 
> that should not be an issue as many threads do not get deleted when 
> the VM terminates. I added destructors for the VMThread and 
> WatcherThread so anyone introducing their deletion is informed by a 
> guarantee(false)

This makes the model easier to understand, IMHO. Either you delete the 
thread from the run() method, or you don't delete it at all.

I's there a way to determine how much memory we leak by not deleting the 
memory owned by the VMThread instance? I'm a bit worried that the 
VMThread might use more resources than the other threads we don't delete.

Thanks,
StefanK

>
>
> Cosmetic changes:
>
> - renamed java_start to thread_native_entry (it is used by all threads 
> not just "java" ones, so this avoids potential confusion)
>
> - updated os::free_thread to always assume it works on the current 
> thread (and add assert to verify that)
>
> Thanks,
> David