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  1. JDK
  2. JDK-8213574

Deadlock in string table expansion when dumping lots of CDS classes

    Details

    • Subcomponent:
    • Resolved In Build:
      b20
    • Verification:
      Verified

      Backports

        Description

        Test case:

        i=0; while java \
            -XX:MaxRAM=8g -Xshare:dump \
            -Xlog:cds,cds+hashtables -Xlog:hashtables \
            -XX:SharedArchiveFile=LotsOfClasses.jsa \
            -XX:ExtraSharedClassListFile=LotsOfClasses.classlist \
            --add-modules ALL-SYSTEM; do
            i=$(expr $i + 1);
            echo ========================================$i;
        done

        (See LotsOfClasses.classlist in attachment of this bug)

        A deadlock happens between the service thread, which tries to expand the string table, and the VM thread, which tries to iterate over all entries in the string table.

        (Note -- VM_PopulateDumpSharedSpace::doit runs inside the VM thread because it wants work on various data structures without worrying about concurrent modifications.)

        SERVICE THREAD

        #1 os::PlatformEvent::park (this=0x7fcb3c814800)
        #2 ParkCommon (timo=0, ev=0x7fcb3c814800)
        #3 Monitor::ILock (this=0x7fcb3c016a00, Self=0x7fcb3c8132b0)
        #4 Monitor::lock_without_safepoint_check (Self=0x7fcb3c8132b0, this=0x7fcb3c016a00)
        #5 Monitor::lock_without_safepoint_check (this=0x7fcb3c016a00)
        #6 SafepointSynchronize::block (thread=0x7fcb3c8132b0)
        #7 SafepointMechanism::block_if_requested_local_poll (thread=0x7fcb3c8132b0)
        #8 SafepointMechanism::block_if_requested (thread=0x7fcb3c8132b0)
        #9 ThreadStateTransition::transition_and_fence (to=_thread_blocked, from=_thread_in_vm, thread=0x7fcb3c8132b0)
        #10 ThreadStateTransition::trans_and_fence (this=<synthetic pointer>, to=_thread_blocked, from=_thread_in_vm)
        #11 ThreadBlockInVM::ThreadBlockInVM (thread=0x7fcb3c8132b0, this=<synthetic pointer>)
        #12 StringTable::grow (this=0x7fcb3c161920, jt=jt@entry=0x7fcb3c8132b0)
        #13 StringTable::concurrent_work (jt=0x7fcb3c8132b0, this=<optimized out>)
        #14 StringTable::do_concurrent_work (jt=jt@entry=0x7fcb3c8132b0)
        #15 ServiceThread::service_thread_entry (jt=0x7fcb3c8132b0, __the_thread__=0x7fcb3c8132b0)
        #16 JavaThread::thread_main_inner (this=this@entry=0x7fcb3c8132b0)
        #17 JavaThread::run (this=0x7fcb3c8132b0)
        #18 Thread::call_run (this=0x7fcb3c8132b0)
        #19 thread_native_entry (thread=0x7fcb3c8132b0)
        #20 start_thread (arg=0x7fcb18b9d700)
        #21 clone ()

        VM THREAD

        #0 ConcurrentHashTable<WeakHandle<(WeakHandleType)2>, StringTableConfig, (MemoryType)9>::lock_resize_lock (locker=0x7fcb3c38db80, this=0x7fcb3c161c30)
        #1 ConcurrentHashTable<WeakHandle<(WeakHandleType)2>, StringTableConfig, (MemoryType)9>::do_scan<CopyToArchive> (scan_f=..., thread=0x7fcb3c38db80,
            this=0x7fcb3c161c30)
        #2 StringTable::copy_shared_string_table (writer=writer@entry=0x7fcb19379820)
        #3 StringTable::write_to_archive ()
        #4 HeapShared::copy_closed_archive_heap_objects (closed_archive=closed_archive@entry=0x7fcac0f314f0)
        #5 HeapShared::archive_java_heap_objects (closed=0x7fcac0f314f0, open=open@entry=0x7fcac0f31550)
        #6 VM_PopulateDumpSharedSpace::dump_java_heap_objects (this=this@entry=0x7fcb436c7b90)
        #7 VM_PopulateDumpSharedSpace::doit (this=<optimized out>)
        #8 VM_Operation::evaluate (this=this@entry=0x7fcb436c7b90)
        #9 VMThread::evaluate_operation (this=this@entry=0x7fcb3c38db80, op=0x7fcb436c7b90)
        #10 VMThread::loop (this=this@entry=0x7fcb3c38db80)
        #11 VMThread::run (this=0x7fcb3c38db80)
        #12 Thread::call_run (this=0x7fcb3c38db80)
        #13 thread_native_entry (thread=0x7fcb3c38db80)
        #14 start_thread (arg=0x7fcb1937a700)

          Attachments

          1. diff.txt
            1 kB
            Ioi Lam
          2. LotsOfClasses.classlist
            1.31 MB
            Ioi Lam

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                • Assignee:
                  rehn Robbin Ehn
                  Reporter:
                  iklam Ioi Lam
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                  Dates

                  • Created:
                    Updated:
                    Resolved: