RFR(XS): 8205195 NestedThreadsListHandleInErrorHandlingTest fails because hs_err doesn't contain _nested_thread_list_max

[Daniel D. Daugherty]

On 6/25/18 1:57 AM, David Holmes wrote:
> Hi Dan,
>
> On 21/06/2018 10:18 AM, Daniel D. Daugherty wrote:
>> Greetings,
>>
>> I have a fix for a recent (very rare) Thread-SMR related test failure.
>>
>> Since the fix is related to the ErrorHandling tests and affects 
>> hs_err_pid
>> file generation, this code review is being sent to both the Runtime and
>> the Serviceability teams. Please make sure you reply-all to any 
>> responses
>> so we have complete review threads on both aliases.
>>
>> Bug URL: https://bugs.openjdk.java.net/browse/JDK-8205195
>>
>> Webrev URL: 
>> http://cr.openjdk.java.net/~dcubed/8205195-webrev/0-for-jdk-jdk/
>>
>> The bug itself contains analysis about the root cause of the bug and
>> the comment updates to the code describes the no win scenario that the
>> hs_err_pid file generation code is in. Of course, I also have a comment
>> where I was able to harden the ErrorHandling tests. I did manage to
>> resist the urge to mention the "Kobiyashi Maru" [1] in the new comments.
>>
>> Testing: Mach5 
>> builds-tier1,jdk-tier1,jdk-tier2,hs-tier1,hs-tier2,hs-tier3
>>           on the usual Oracle platforms.
>>
>> Thanks, in advance, for any comments, questions or suggestions.
>
> I don't quite follow the fix.

I think this comment explains what the fix is _trying_ to do:

1702   // We grab Threads_lock to keep ThreadsSMRSupport::print_info_on()
1703   // from racing with Threads::add() or Threads::remove() as we
1704   // generate the hs_err_pid file. This makes our ErrorHandling tests
1705   // more stable.


> Won't you self-deadlock on acquiring the Threads_lock in the secondary 
> error handler test, due to the recursive call to controlled_crash ?

I missed that possibility, but now I'm puzzled why my testing didn't
reveal this situation. We have a test for secondary error handling
and it should have self-deadlocked (and failed). I'll investigate.

Dan


>
> David
>
>> Dan
>>
>> [1] https://www.urbandictionary.com/define.php?term=Kobayashi%20Maru
>>