Code review request: CR 7141259 Native stack is missing in hs_err

[Zhengyu Gu]

Hi David,

Thanks for reviewing. I think I made wrong assumption that the thread is 
the last running thread.

803   // This should be the only running thread, decoder can safely run in
  804   // single threaded mode without acquiring lock
  805   Decoder::set_single_threaded(true);
  806

To avoid locking in error handler, the only solution I can think of, is 
to have its own private decoder.

Please see revised webrev: 
http://cr.openjdk.java.net/~zgu/7141259/webrev.01/

> Later when there are multiple users of the Decoder I don't know how 
> you will fix this because those other users can run concurrently with 
> report_and_die(). That said I'm unclear what it is about the Decoder 
> that requires locking - what state does it maintain? Is there a reason 
> not to create a Decoder only when needed?
>
Decoder is created on demand, but would prefer to be shared, since it 
can consume noticeable amount memory on Unix platform, by loading Elf 
files' symbol tables and string tables into memory (not impact on 
Windows).  The lock is needed to protect a linked list structure in Elf 
decoder, or current file position.

Thanks,

-Zhengyu
> ---
>
> In decoder.cpp you can still use MutexLockerEx and as it will take a 
> null mutex and just act as a no-op eg:
>
>   MutexLockerEx locker( _single_thread ? NULL : _decoder_lock, true);
>
> Cheers,
> David
> -----
>
>>
>> Please review
>> Webrev: http://cr.openjdk.java.net/~zgu/7141259/webrev.00/
>>
>>
>> Thanks,
>>
>> -Zhengyu
>>