JVM hung from incomplete safepoint pause

Issue

• Our JVM hangs and even a typical thread dump cannot be captured from it. Native traces show the VMThread continually waiting in SafepointSynchronize::begin():

#0  0x00007f71f973e945 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0
#1  0x00007f71f86397e3 in os::PlatformEvent::park() () from /opt/java/jdk/jre/lib/amd64/server/libjvm.so
#2  0x00007f71f85f9748 in Monitor::ILock(Thread*) () from /opt/java/jdk/jre/lib/amd64/server/libjvm.so
#3  0x00007f71f85f98e1 in Monitor::lock(Thread*) () from /opt/java/jdk/jre/lib/amd64/server/libjvm.so
#4  0x00007f71f86d7796 in SafepointSynchronize::begin() () from /opt/java/jdk/jre/lib/amd64/server/libjvm.so
#5  0x00007f71f87e8eaf in VMThread::loop() () from /opt/java/jdk/jre/lib/amd64/server/libjvm.so
#6  0x00007f71f87e9330 in VMThread::run() () from /opt/java/jdk/jre/lib/amd64/server/libjvm.so
#7  0x00007f71f8640568 in java_start(Thread*) () from /opt/java/jdk/jre/lib/amd64/server/libjvm.so
#8  0x00007f71f8d2473f in ?? () from /opt/cylance/desktop/cymemdeflinux_x64.so
#9  0x00007f71f973add5 in start_thread () from /lib64/libpthread.so.0
#10 0x00007f71f904ab3d in clone () from /lib64/libc.so.6