Re: RFR (XS) 8047212: fix race between ObjectMonitor alloc and verification code

[Daniel D. Daugherty]

Thanks for the re-review!

Current stress test results:

$ grep -v PASS doit_loop.fast_?.log
doit_loop.fast_0.log:Copy fast_0: loop #271077...
doit_loop.fast_1.log:Copy fast_1: loop #271178...
doit_loop.fast_2.log:Copy fast_2: loop #271217...
doit_loop.fast_3.log:Copy fast_3: loop #271223...

$ elapsed_times mark.start_test_run doit_loop.fast_0.log
mark.start_test_run                                0 seconds
doit_loop.fast_0.log   1 days 19 hours 30 minutes 39 seconds

The typical failure rate for this bug is 1-3 failures in 3 days
with some other failure modes (in C2 or G1) popping in for a visit.

So far... no failures...

Dan

On 10/22/15, 9:30 AM, Carsten Varming wrote:

Dear Dan,

I reviewed round 1. Looks good to me.

Thank you for the updated webbrew.

Carsten

On Tue, Oct 20, 2015 at 2:15 PM, Daniel D. Daugherty <daniel.daughe...@oracle.com <mailto:daniel.daughe...@oracle.com>> wrote:

    Greetings,

    I've updated the fix based on feedback from Carsten V and David H.

    Webrev URL:
    http://cr.openjdk.java.net/~dcubed/8047212-webrev/1-jdk9-hs-rt/
    <http://cr.openjdk.java.net/%7Edcubed/8047212-webrev/1-jdk9-hs-rt/>

    Changes relative to round 0:

    - only src/share/vm/runtime/synchronizer.cpp has changed
    - reads of gBlockList now use OrderAccess::load_ptr_acquire()

    code style cleanups:

    - only cleaned up the functions that I touched to make the
      OrderAccess::load_ptr_acquire() changes
    - changed implied booleans into real boolean expressions
    - moved some locals to narrower context
    - added/removed some blank lines
    - made casts consistent with the majority style in this file

    I'm repeating all of the same testing that I did for round 0. The
    round 1 bits have not yet made it through JPRT-west, but the jobs
    are mostly done.

    Thanks, in advance, for any comments, questions or suggestions.

    Dan





    On 10/19/15, 9:02 PM, Daniel D. Daugherty wrote:

        Greetings,

        I have a fix for a long standing race between the lock-free
        ObjectMonitor
        verification code and the normal (locked) ObjectMonitor block
        allocation
        code path. For this fix, I would like at least a Runtime team
        reviewer
        and a Serviceability team reviewer. Thanks!

        JDK-8047212
        runtime/ParallelClassLoading/bootstrap/random/inner-complex

assert(ObjectSynchronizer::verify_objmon_isinpool(inf)) failed:

                    monitor is invalid
        https://bugs.openjdk.java.net/browse/JDK-8047212

        Webrev URL:
        http://cr.openjdk.java.net/~dcubed/8047212-webrev/0-jdk9-hs-rt/ 
<http://cr.openjdk.java.net/%7Edcubed/8047212-webrev/0-jdk9-hs-rt/>

        Testing: Aurora Adhoc RT-SVC nightly batch
                 4 inner-complex fastdebug parallel runs for 4+ days and
                   600K iterations without seeing this failure; the
        experiment
                   is still running; final results to be reported at
        the end
                   of the review cycle
                 JPRT -testset hotspot

        This fix:

        - makes ObjectMonitor::gBlockList volatile
        - uses "OrderAccess::release_store_ptr(&gBlockList, temp)" to
          make sure the new block updates _happen before_ gBlockList is
          changed to refer to the new block
        - add SA support for a "static pointer volatile" field like:

            static ObjectMonitor * volatile gBlockList;

        See the following link for a nice description of what "volatile"
        means in the different positions on a variable/parameter decl
        line:

        
http://www.embedded.com/electronics-blogs/beginner-s-corner/4023801/Introduction-to-the-Volatile-Keyword


        Thanks, in advance, for any comments, questions or suggestions.

        Dan