The failure is very intermittent. Observed in tests:
serviceability/sa/TestJhsdbJstackLock.java
serviceability/sa/TestInstanceKlassSize.java

The log is:
Error attaching to process: Windbg Error: WaitForEvent failed!
sun.jvm.hotspot.debugger.DebuggerException: Windbg Error: WaitForEvent failed!
at jdk.hotspot.agent/sun.jvm.hotspot.debugger.windbg.WindbgDebuggerLocal.attach0(Native Method)
at jdk.hotspot.agent/sun.jvm.hotspot.debugger.windbg.WindbgDebuggerLocal.attach(WindbgDebuggerLocal.java:148)
at jdk.hotspot.agent/sun.jvm.hotspot.HotSpotAgent.attachDebugger(HotSpotAgent.java:672)
at jdk.hotspot.agent/sun.jvm.hotspot.HotSpotAgent.setupDebuggerWin32(HotSpotAgent.java:568)
at jdk.hotspot.agent/sun.jvm.hotspot.HotSpotAgent.setupDebugger(HotSpotAgent.java:336)
at jdk.hotspot.agent/sun.jvm.hotspot.HotSpotAgent.go(HotSpotAgent.java:305)
at jdk.hotspot.agent/sun.jvm.hotspot.HotSpotAgent.attach(HotSpotAgent.java:141)
at jdk.hotspot.agent/sun.jvm.hotspot.tools.Tool.start(Tool.java:185)
at jdk.hotspot.agent/sun.jvm.hotspot.tools.Tool.execute(Tool.java:118)
at jdk.hotspot.agent/sun.jvm.hotspot.tools.JStack.runWithArgs(JStack.java:90)
at jdk.hotspot.agent/sun.jvm.hotspot.SALauncher.runJSTACK(SALauncher.java:259)
at jdk.hotspot.agent/sun.jvm.hotspot.SALauncher.main(SALauncher.java:450)


 stdout: [Attaching to process ID 16284, please wait...
];
 stderr: [Error attaching to process: Windbg Error: WaitForEvent failed!
sun.jvm.hotspot.debugger.DebuggerException: Windbg Error: WaitForEvent failed!
at jdk.hotspot.agent/sun.jvm.hotspot.debugger.windbg.WindbgDebuggerLocal.attach0(Native Method)
at jdk.hotspot.agent/sun.jvm.hotspot.debugger.windbg.WindbgDebuggerLocal.attach(WindbgDebuggerLocal.java:148)
at jdk.hotspot.agent/sun.jvm.hotspot.HotSpotAgent.attachDebugger(HotSpotAgent.java:672)
at jdk.hotspot.agent/sun.jvm.hotspot.HotSpotAgent.setupDebuggerWin32(HotSpotAgent.java:568)
at jdk.hotspot.agent/sun.jvm.hotspot.HotSpotAgent.setupDebugger(HotSpotAgent.java:336)
at jdk.hotspot.agent/sun.jvm.hotspot.HotSpotAgent.go(HotSpotAgent.java:305)
at jdk.hotspot.agent/sun.jvm.hotspot.HotSpotAgent.attach(HotSpotAgent.java:141)
at jdk.hotspot.agent/sun.jvm.hotspot.tools.Tool.start(Tool.java:185)
at jdk.hotspot.agent/sun.jvm.hotspot.tools.Tool.execute(Tool.java:118)
at jdk.hotspot.agent/sun.jvm.hotspot.tools.JStack.runWithArgs(JStack.java:90)
at jdk.hotspot.agent/sun.jvm.hotspot.SALauncher.runJSTACK(SALauncher.java:259)
at jdk.hotspot.agent/sun.jvm.hotspot.SALauncher.main(SALauncher.java:450)

]
 exitValue = 1