Two threads here:

"MainThread" #13 prio=5 os_prio=0 cpu=1395.77ms elapsed=494.85s tid=0x00007fcec82ab000 nid=0x503f waiting on condition _threads_hazard_ptr=0x00007fce88002250, _nested_threads_hazard_ptr_cnt=1, _nested_threads_hazard_ptr=0x00007fce88002250 [0x00007fcea52df000]
   java.lang.Thread.State: RUNNABLE
Thread: 0x00007fcec82ab000 [0x503f] State: _running _has_called_back 0 _at_poll_safepoint 0
   JavaThread state: _thread_blocked
at java.lang.Thread.suspend0(java.base@13-internal/Native Method)
at java.lang.Thread.suspend(java.base@13-internal/Thread.java:1086)
at SuspendAtExit.main(SuspendAtExit.java:69)
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(java.base@13-internal/Native Method)
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(java.base@13-internal/NativeMethodAccessorImpl.java:62)
at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(java.base@13-internal/DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(java.base@13-internal/Method.java:567)
at com.sun.javatest.regtest.agent.MainWrapper$MainThread.run(MainWrapper.java:127)
at java.lang.Thread.run(java.base@13-internal/Thread.java:835)

Thread 4 (Thread 0x7fcea52e1700 (LWP 20543)):
#0 0x00007fced0dd1cf2 in pthread_cond_timedwait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0
#1 0x00007fcecfa99bcd in os::PlatformMonitor::wait(long) () from /scratch/opt/mach5/mesos/work_dir/jib-master/install/2019-02-05-1316169.robbin.ehn.safepoint-jdk/linux-x64-debug.jdk/jdk-13/fastdebug/lib/server/libjvm.so
#2 0x00007fcecf9e2fcd in Monitor::wait(bool, long, bool) () from /scratch/opt/mach5/mesos/work_dir/jib-master/install/2019-02-05-1316169.robbin.ehn.safepoint-jdk/linux-x64-debug.jdk/jdk-13/fastdebug/lib/server/libjvm.so
#3 0x00007fcecfd9ad34 in JavaThread::is_ext_suspend_completed(bool, int, unsigned int*) () from /scratch/opt/mach5/mesos/work_dir/jib-master/install/2019-02-05-1316169.robbin.ehn.safepoint-jdk/linux-x64-debug.jdk/jdk-13/fastdebug/lib/server/libjvm.so
#4 0x00007fcecfd9afb5 in JavaThread::java_suspend() () from /scratch/opt/mach5/mesos/work_dir/jib-master/install/2019-02-05-1316169.robbin.ehn.safepoint-jdk/linux-x64-debug.jdk/jdk-13/fastdebug/lib/server/libjvm.so
#5 0x00007fcecf5f173e in JVM_SuspendThread () from /scratch/opt/mach5/mesos/work_dir/jib-master/install/2019-02-05-1316169.robbin.ehn.safepoint-jdk/linux-x64-debug.jdk/jdk-13/fastdebug/lib/server/libjvm.so
#6 0x00007fceb863fd20 in ?? ()
#7 0x00000007460a0918 in ?? ()
#8 0x00007fcea52dffa8 in ?? ()
#9 0x00007fcea52e0028 in ?? ()
#10 0x00007fcec82ab000 in ?? ()
#11 0x00007fcea52dff90 in ?? ()
#12 0x00007fceb863f8a0 in ?? ()
#13 0x00000007460a0918 in ?? ()
#14 0x00007fceb0b9f27f in ?? ()
#15 0x00007fcea52dfff8 in ?? ()
#16 0x00007fceb8640514 in ?? ()
#17 0x0000000000000000 in ?? ()

SR_lock()->wait(!Thread::current()->is_Java_thread(), i * delay);

                threads[i].interrupt();
                for (; late_count <= N_LATE_CALLS; late_count++) {
                    threads[i].suspend();


################################################################################################

"Thread-10" #23 prio=5 os_prio=0 cpu=33.31ms elapsed=493.02s tid=0x00007fce74071800 nid=0x5092 runnable [0x00007fcea51df000]
   java.lang.Thread.State: RUNNABLE
Thread: 0x00007fce74071800 [0x5092] State: _running _has_called_back 0 _at_poll_safepoint 0
   JavaThread state: _thread_in_native_trans
at jdk.internal.misc.Unsafe.compareAndSetReference(java.base@13-internal/Native Method)
at java.lang.invoke.VarHandleReferences$FieldInstanceReadWrite.compareAndSet(java.base@13-internal/VarHandleReferences.java:138)
at java.lang.invoke.VarHandleGuards.guard_LLL_Z(java.base@13-internal/VarHandleGuards.java:77)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.initializeSyncQueue(java.base@13-internal/AbstractQueuedSynchronizer.java:2324)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.addWaiter(java.base@13-internal/AbstractQueuedSynchronizer.java:662)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireSharedInterruptibly(java.base@13-internal/AbstractQueuedSynchronizer.java:1026)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireSharedInterruptibly(java.base@13-internal/AbstractQueuedSynchronizer.java:1345)
at java.util.concurrent.CountDownLatch.await(java.base@13-internal/CountDownLatch.java:232)
at SuspendAtExit.run(SuspendAtExit.java:47)

Thread 3 (Thread 0x7fcea51e0700 (LWP 20626)):
#0 0x00007fced0dd1945 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0
#1 0x00007fcecfa99c8f in os::PlatformMonitor::wait(long) () from /scratch/opt/mach5/mesos/work_dir/jib-master/install/2019-02-05-1316169.robbin.ehn.safepoint-jdk/linux-x64-debug.jdk/jdk-13/fastdebug/lib/server/libjvm.so
#2 0x00007fcecf9e34a4 in Monitor::wait(bool, long, bool) () from /scratch/opt/mach5/mesos/work_dir/jib-master/install/2019-02-05-1316169.robbin.ehn.safepoint-jdk/linux-x64-debug.jdk/jdk-13/fastdebug/lib/server/libjvm.so
#3 0x00007fcecfd93025 in JavaThread::java_suspend_self() [clone .part.200] () from /scratch/opt/mach5/mesos/work_dir/jib-master/install/2019-02-05-1316169.robbin.ehn.safepoint-jdk/linux-x64-debug.jdk/jdk-13/fastdebug/lib/server/libjvm.so
#4 0x00007fcecfda3088 in JavaThread::handle_special_runtime_exit_condition(bool) () from /scratch/opt/mach5/mesos/work_dir/jib-master/install/2019-02-05-1316169.robbin.ehn.safepoint-jdk/linux-x64-debug.jdk/jdk-13/fastdebug/lib/server/libjvm.so
#5 0x00007fcecfc1482a in SafepointMechanism::block_if_requested_slow(JavaThread*) () from /scratch/opt/mach5/mesos/work_dir/jib-master/install/2019-02-05-1316169.robbin.ehn.safepoint-jdk/linux-x64-debug.jdk/jdk-13/fastdebug/lib/server/libjvm.so
#6 0x00007fcecfd99440 in JavaThread::check_safepoint_and_suspend_for_native_trans(JavaThread*) () from /scratch/opt/mach5/mesos/work_dir/jib-master/install/2019-02-05-1316169.robbin.ehn.safepoint-jdk/linux-x64-debug.jdk/jdk-13/fastdebug/lib/server/libjvm.so
#7 0x00007fcecfda3fa1 in JavaThread::check_special_condition_for_native_trans(JavaThread*) () from /scratch/opt/mach5/mesos/work_dir/jib-master/install/2019-02-05-1316169.robbin.ehn.safepoint-jdk/linux-x64-debug.jdk/jdk-13/fastdebug/lib/server/libjvm.so
#8 0x00007fceb863a23e in ?? ()
#9 0x0000000745f99b60 in ?? ()
#10 0x00000007460a0b40 in ?? ()
#11 0x0000000000000000 in ?? ()


    while (is_ext_suspended()) {
      this->SR_lock()->wait(Mutex::_no_safepoint_check_flag);
    }

    public void run() {
        // Tell main thread we have started.
        startSyncObj.countDown();