RFR(S): 8200374: Add ThreadsSMRSupport::verify_hazard_pointer_scanned() to verify threads_do()

[Daniel D. Daugherty]

Erik,

Thanks for the quick review!


On 3/29/18 3:00 AM, Erik Österlund wrote:
> Hi Dan,
>
> This looks great.

Good to hear especially since you wrote most of it... :-)


> I will sleep much better at night with this 1:1 verification. :)

It does tighten things up nicely!

Dan


>
> Thanks,
> /Erik
>
>
> On 2018-03-29 03:52, Daniel D. Daugherty wrote:
>> Greetings,
>>
>> I have a (mostly) small enhancement for Thread-SMR:
>>
>> JDK-8200374 Add ThreadsSMRSupport::verify_hazard_pointer_scanned() to 
>> verify threads_do()
>> https://bugs.openjdk.java.net/browse/JDK-8200374
>>
>> Here's the webrev URL:
>>
>> http://cr.openjdk.java.net/~dcubed/8200374-webrev/0_for_jdk_hs_open/
>>
>> This is Erik O's improvement on the assertion added by the following
>> bug fix (with some minor tweaking done by me):
>>
>> JDK-8199813 SIGSEGV in ThreadsList::includes()
>> https://bugs.openjdk.java.net/browse/JDK-8199813
>>
>> Summary of the changes:
>>
>> - Replace the assertion that I added in JDK-8199813 with a closure
>>   based function that verifies the threads_do() contract depended
>>   on by Thread-SMR.
>> - Add ThreadsSMRSupport::verify_hazard_pointer_scanned() to verify
>>   that the calling thread's hazard pointer is scanned by threads_do().
>>   The new function is called from both ThreadsSMRSupport::acquire_*()
>>   functions.
>> - Refactor the non-JavaThread part of Threads::threads_do() into
>>   Threads::non_java_threads_do() so that the non-JavaThread part
>>   can also be called by other threads_do() functions. Yes, the
>>   Threads::threads_do() contract is still to scan every thread in
>>   the system.
>> - Add hooks for a "tracing sampler thread" to be optionally scanned
>>   by Threads::non_java_threads_do().
>>
>> This fix has gone thru a couple of Mach5 builds-tier1, jdk-tier[1-3],
>> and hs-tier[1-3] runs. I've also started my usual 24+ hour Thread-SMR
>> stress testing run on my Solaris-X64 server.
>>
>> Just to be extra sure, I backed out the fix from JDK-8199813 to
>> JavaThread::verify_not_published() (which started this round of
>> Thread-SMR fixes) and we catch the issue in the new function
>> ThreadsSMRSupport::verify_hazard_pointer_scanned().
>>
>> Thanks, in advance, for any comments, suggestions, or feedback.
>>
>> Dan
>>
>