RFR(XL): 8167108 - SMR and JavaThread Lifecycle

David Holmes david.holmes at oracle.com
Tue Nov 28 08:01:27 UTC 2017 

Just for the record ...

On 23/11/2017 6:20 PM, Robbin Ehn wrote:
> Thanks Dan for dragging this freight train to the docks, it's time to 
> ship it!

I agree. The latest delta seems fine to me.

> Created follow-up bug:
> 8191809: Threads::number_of_threads() is not 'MT-safe'
> https://bugs.openjdk.java.net/browse/JDK-8191809

Just updated that bug - I don't see any MT issues there. :)

Cheers,
David

PS. Dan: yes JPRT was still doing 32-bit ARM a "month or two back". 
64-bit atomics should not be a concern. That said I thought all the 
atomic updates were done for ARM etc.

> /Robbin
> 
> On 2017-11-23 03:16, Daniel D. Daugherty wrote:
>> Greetings,
>>
>> I've made minor tweaks to the Thread-SMR project based on the remaining
>> code review comments over the last couple of days. I've also rebased the
>> project to jdk/hs bits as of mid-afternoon (my TZ) on 2017.11.22. I'm
>> running baseline Mach5 Tier[1-5] testing and prototype Mach5 Tier[1-5]
>> testing...
>>
>> Here's a delta webrev for the latest round of tweaks:
>>
>> http://cr.openjdk.java.net/~dcubed/8167108-webrev/jdk10-11-delta
>>
>>
>> Here's the proposed commit message:
>>
>> $ cat SMR_prototype_10/open/commit.txt
>> 8167108: inconsistent handling of SR_lock can lead to crashes
>> Summary: Add Thread Safe Memory Reclamation (Thread-SMR) mechanism.
>> Reviewed-by: coleenp, dcubed, dholmes, eosterlund, gthornbr, kbarrett, 
>> rehn, sspitsyn, stefank
>> Contributed-by: daniel.daugherty at oracle.com, 
>> erik.osterlund at oracle.com, robbin.ehn at oracle.com
>>
>> I've gone through 880+ emails in my archive for this project and added
>> anyone that made a code review comment. Reviewers are not in my usual
>> by-comment-posting order; it was way too hard to figure that out... So
>> reviewers and contributors are simply in alpha-sort order...
>>
>> Here's the collection of follow-up bugs that I filed based on sifting
>> through the email archive:
>>
>> 8191784 JavaThread::collect_counters() should stop using Threads_lock
>> https://bugs.openjdk.java.net/browse/JDK-8191784
>>
>> 8191785 revoke_bias() needs a new assertion
>> https://bugs.openjdk.java.net/browse/JDK-8191785
>>
>> 8191786 Thread-SMR hash table size should be dynamic
>> https://bugs.openjdk.java.net/browse/JDK-8191786
>>
>> 8191787 move private inline functions from thread.inline.hpp -> 
>> thread.cpp
>> https://bugs.openjdk.java.net/browse/JDK-8191787
>>
>> 8191789 migrate more Thread-SMR stuff from thread.[ch]pp -> 
>> threadSMR.[ch]pp
>> https://bugs.openjdk.java.net/browse/JDK-8191789
>>
>> 8191798 redo nested ThreadsListHandle to drop Threads_lock
>> https://bugs.openjdk.java.net/browse/JDK-8191789
>>
>> I have undoubtedly missed at least one future idea that someone had
>> and for that my apologies...
>>
>> Thanks again to everyone who contributed to the Thread-SMR project!!
>>
>> Special thanks goes to Karen Kinnear, Kim Barrett and David Holmes for
>> their rigorous review of the design that we documented on the wiki.
>> Thanks for keeping us honest!
>>
>> I also have to thank my co-contributor Erik Österlund for starting the
>> ball rolling on this crazy project with his presentation on Safe Memory
>> Reclamation, for the initial prototype and for all your patches. Erik,
>> hopefully we got far enough in your crazy vision... :-)
>>
>> Thanks to my co-contributor Robbin Ehn for proposing that we do early
>> code reviews in the form of patches. Don't like something? Fix it with
>> a patch and a new test if appropriate!! A pretty cool way to work that
>> was new to me.
>>
>> Finally, many thanks to Jerry Thornbrugh for all the early code reviews,
>> whiteboard chats and phone calls. Thanks for asking the right questions
>> and pointing out some places where our logic was faulty. Also thanks for
>> keeping me sane when I was literally on my own in Monument, CO.
>>
>> Dan
>>
>>
>> On 11/21/17 7:12 PM, Daniel D. Daugherty wrote:
>>> Greetings,
>>>
>>> *** We are wrapping up code review on this project so it is time ***
>>> *** for the various code reviewers to chime in one last time. ***
>>>
>>> In this latest round, we had three different reviewers chime in so we're
>>> doing delta webrevs for each of those resolutions:
>>>
>>> David H's resolutions:
>>>
>>> http://cr.openjdk.java.net/~dcubed/8167108-webrev/jdk10-10.09,10.10.0-delta/ 
>>>
>>>
>>>   mq comment for dholmes_CR:
>>>     - Fix indents, trailing spaces and various typos.
>>>     - Add descriptions for the '_cnt', '_max' and '_times" fields,
>>>       add impl notes to document the type choices.
>>>
>>>   src/hotspot/share/runtime/globals.hpp change is white-space only so it
>>>   is only visible via the file's patch link.
>>>
>>>
>>> Robin W's resolutions:
>>>
>>> http://cr.openjdk.java.net/~dcubed/8167108-webrev/jdk10-10.10.0,10.10.1-delta/ 
>>>
>>>
>>>   mq comment for robinw_CR:
>>>     - Fix some inefficient code, update some comments, fix some indents,
>>>       and add some 'const' specifiers.
>>>
>>>   src/hotspot/share/runtime/vm_operations.hpp change is white-space 
>>> only so
>>>   it is only visible via the file's patch link.
>>>
>>>
>>> Coleen's resolutions:
>>>
>>> http://cr.openjdk.java.net/~dcubed/8167108-webrev/jdk10-10.10.1,10.10.2-delta/ 
>>>
>>>
>>>   mq comment for coleenp_CR:
>>>     - Change ThreadsList::_threads from 'mtGC' -> 'mtThread',
>>>     - add header comment to threadSMR.hpp file,
>>>     - cleanup JavaThreadIteratorWithHandle ctr,
>>>     - make ErrorHandling more efficient.
>>>
>>>
>>> Some folks prefer to see all of the delta webrevs together so here is
>>> a delta webrev relative to jdk10-09-full:
>>>
>>> http://cr.openjdk.java.net/~dcubed/8167108-webrev/jdk10-10.09,10.10.2-delta/ 
>>>
>>>
>>>   src/hotspot/share/runtime/globals.hpp and
>>>   src/hotspot/share/runtime/vm_operations.hpp changes are white-space 
>>> only
>>>   so they are only visible via the file's patch link.
>>>
>>>
>>> And, of course, some folks prefer to see everything all at once so here
>>> is the latest full webrev:
>>>
>>> http://cr.openjdk.java.net/~dcubed/8167108-webrev/jdk10-10.10-full/
>>>
>>>
>>> Dan has submitted the bits for the usual Mach5 tier[1-5] testing. The
>>> prelim Mach5 tier1 (JPRT equivalent) on these bits passed just fine...
>>>
>>> The project is currently baselined on Jesper's 2017-11-17 PIT snapshot
>>> so there will be some catching up to do before integration...
>>>
>>> We welcome comments, suggestions and feedback.
>>>
>>> Dan, Erik and Robbin
>>>
>>>
>>> On 11/18/17 8:49 PM, Daniel D. Daugherty wrote:
>>>> Greetings,
>>>>
>>>> Testing of the last round of changes revealed a hang in one of the new
>>>> TLH tests. Robbin has fixed the hang, updated the existing TLH test, 
>>>> and
>>>> added another TLH test for good measure.
>>>>
>>>> Here is the updated full webrev:
>>>>
>>>> http://cr.openjdk.java.net/~dcubed/8167108-webrev/jdk10-09-full/
>>>>
>>>> Here is the updated delta webrev:
>>>>
>>>> http://cr.openjdk.java.net/~dcubed/8167108-webrev/jdk10-09-delta/
>>>>
>>>> Dan ran the bits thru the usual Mach5 tier[1-5] testing and there are
>>>> no unexpected failures.
>>>>
>>>> We welcome comments, suggestions and feedback.
>>>>
>>>> Dan, Erik and Robbin
>>>>
>>>>
>>>> On 11/15/17 3:32 PM, Daniel D. Daugherty wrote:
>>>>> Greetings,
>>>>>
>>>>> Robbin rebased the project last night/this morning to merge with 
>>>>> Thread
>>>>> Local Handshakes (TLH) and also picked up additional changesets up 
>>>>> thru:
>>>>>
>>>>>> Changeset: fa736014cf28
>>>>>> Author:    cjplummer
>>>>>> Date:      2017-11-14 18:08 -0800
>>>>>> URL:http://hg.openjdk.java.net/jdk/hs/rev/fa736014cf28
>>>>>>
>>>>>> 8191049: Add alternate version of pns() that is callable from 
>>>>>> within hotspot source
>>>>>> Summary: added pns2() to debug.cpp
>>>>>> Reviewed-by: stuefe, gthornbr
>>>>>
>>>>> This is the first time we've rebased the project to bits that are this
>>>>> fresh (< 12 hours old at rebase time). We've done this because we 
>>>>> think
>>>>> we're done with this project and are in the final review-change-retest
>>>>> cycle(s)... In other words, we're not planning on making any more 
>>>>> major
>>>>> changes for this project... :-)
>>>>>
>>>>> *** Time for code reviewers to chime in on this thread! ***
>>>>>
>>>>> Here is the updated full webrev:
>>>>>
>>>>> http://cr.openjdk.java.net/~dcubed/8167108-webrev/jdk10-08-full/
>>>>>
>>>>> Here's is the delta webrev from the 2017.11.10 rebase:
>>>>>
>>>>> http://cr.openjdk.java.net/~dcubed/8167108-webrev/jdk10-08-delta/
>>>>>
>>>>> Dan has submitted the bits for the usual Mach5 tier[1-5] testing
>>>>> (and the new baseline also)...
>>>>>
>>>>> We're expecting this round to be a little noisier than usual because
>>>>> we did not rebase on a PIT snapshot so the new baseline has not been
>>>>> through Jesper's usual care-and-feeding of integration_blockers, etc.
>>>>>
>>>>> We welcome comments, suggestions and feedback.
>>>>>
>>>>> Dan, Erik and Robbin
>>>>>
>>>>>
>>>>> On 11/14/17 4:48 PM, Daniel D. Daugherty wrote:
>>>>>> Greetings,
>>>>>>
>>>>>> I rebased the project to the 2017.11.10 jdk/hs PIT snapshot.
>>>>>> (Yes, we're playing chase-the-repo...)
>>>>>>
>>>>>> Here is the updated full webrev:
>>>>>>
>>>>>> http://cr.openjdk.java.net/~dcubed/8167108-webrev/jdk10-07-full/
>>>>>>
>>>>>> Unlike the previous rebase, there were no changes required to the
>>>>>> open code to get the rebased bits to build so there is no delta
>>>>>> webrev.
>>>>>>
>>>>>> These bits have been run through JPRT and I've submitted the usual
>>>>>> Mach5 tier[1-5] test run...
>>>>>>
>>>>>> We welcome comments, suggestions and feedback.
>>>>>>
>>>>>> Dan, Erik and Robbin
>>>>>>
>>>>>>
>>>>>> On 11/13/17 12:30 PM, Daniel D. Daugherty wrote:
>>>>>>> Greetings,
>>>>>>>
>>>>>>> I rebased the project to the 2017.10.26 jdk10/hs PIT snapshot.
>>>>>>>
>>>>>>> Here are the updated webrevs:
>>>>>>>
>>>>>>> Here's the mq comment for the change:
>>>>>>>
>>>>>>>   Rebase to 2017.10.25 PIT snapshot.
>>>>>>>
>>>>>>> Here is the full webrev:
>>>>>>>
>>>>>>> http://cr.openjdk.java.net/~dcubed/8167108-webrev/jdk10-06-full/
>>>>>>>
>>>>>>> And here is the delta webrev:
>>>>>>>
>>>>>>> http://cr.openjdk.java.net/~dcubed/8167108-webrev/jdk10-06-delta/
>>>>>>>
>>>>>>> I ran the above bits throught Mach5 tier[1-5] testing over the 
>>>>>>> holiday
>>>>>>> weekend. Didn't see any issues in a quick look. Going to take a 
>>>>>>> closer
>>>>>>> look today.
>>>>>>>
>>>>>>> We welcome comments, suggestions and feedback.
>>>>>>>
>>>>>>> Dan, Erik and Robbin
>>>>>>>
>>>>>>>
>>>>>>> On 11/8/17 1:05 PM, Daniel D. Daugherty wrote:
>>>>>>>> Greetings,
>>>>>>>>
>>>>>>>> Resolving one of the code review comments (from both Stefan K 
>>>>>>>> and Coleen)
>>>>>>>> on jdk10-04-full required quite a few changes so it is being 
>>>>>>>> done as a
>>>>>>>> standalone patch and corresponding webrevs:
>>>>>>>>
>>>>>>>> Here's the mq comment for the change:
>>>>>>>>
>>>>>>>>   stefank, coleenp CR - refactor most JavaThreadIterator usage 
>>>>>>>> to use
>>>>>>>>     JavaThreadIteratorWithHandle.
>>>>>>>>
>>>>>>>> Here is the full webrev:
>>>>>>>>
>>>>>>>> http://cr.openjdk.java.net/~dcubed/8167108-webrev/jdk10-05-full/
>>>>>>>>
>>>>>>>> And here is the delta webrev:
>>>>>>>>
>>>>>>>> http://cr.openjdk.java.net/~dcubed/8167108-webrev/jdk10-05-delta/
>>>>>>>>
>>>>>>>> We welcome comments, suggestions and feedback.
>>>>>>>>
>>>>>>>> Dan, Erik and Robbin
>>>>>>>>
>>>>>>>>
>>>>>>>> On 10/9/17 3:41 PM, Daniel D. Daugherty wrote:
>>>>>>>>> Greetings,
>>>>>>>>>
>>>>>>>>> We have a (eXtra Large) fix for the following bug:
>>>>>>>>>
>>>>>>>>> 8167108 inconsistent handling of SR_lock can lead to crashes
>>>>>>>>> https://bugs.openjdk.java.net/browse/JDK-8167108
>>>>>>>>>
>>>>>>>>> This fix adds a Safe Memory Reclamation (SMR) mechanism based on
>>>>>>>>> Hazard Pointers to manage JavaThread lifecycle.
>>>>>>>>>
>>>>>>>>> Here's a PDF for the internal wiki that we've been using to 
>>>>>>>>> describe
>>>>>>>>> and track the work on this project:
>>>>>>>>>
>>>>>>>>> http://cr.openjdk.java.net/~dcubed/8167108-webrev/SMR_and_JavaThread_Lifecycle-JDK10-04.pdf 
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Dan has noticed that the indenting is wrong in some of the code 
>>>>>>>>> quotes
>>>>>>>>> in the PDF that are not present in the internal wiki. We don't 
>>>>>>>>> have a
>>>>>>>>> solution for that problem yet.
>>>>>>>>>
>>>>>>>>> Here's the webrev for current JDK10 version of this fix:
>>>>>>>>>
>>>>>>>>> http://cr.openjdk.java.net/~dcubed/8167108-webrev/jdk10-04-full
>>>>>>>>>
>>>>>>>>> This fix has been run through many rounds of JPRT and Mach5 
>>>>>>>>> tier[2-5]
>>>>>>>>> testing, additional stress testing on Dan's Solaris X64 server, 
>>>>>>>>> and
>>>>>>>>> additional testing on Erik and Robbin's machines.
>>>>>>>>>
>>>>>>>>> We welcome comments, suggestions and feedback.
>>>>>>>>>
>>>>>>>>> Daniel Daugherty
>>>>>>>>> Erik Osterlund
>>>>>>>>> Robbin Ehn
>>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>
>>>
>>

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