Problem is Linux ptrace() to get register values fails intermittently.
Opening this bug to track the Linux problem.

Following nsk sajdi test fails:

nsk/sajdi/ThreadReference/frame/frame002
nsk/sajdi/ThreadReference/frames/frames002
nsk/sajdi/ThreadReference/frames_ii/frames_ii002
nsk/sajdi/StackFrame/getValues/getvalues001
nsk/sajdi/StackFrame/thisObject/thisobj001
nsk/sajdi/StackFrame/visibleVariables/visibvars001
nsk/sajdi/VMCannotBeModifiedException/thrown/thrown003

And any other tests which tries to get thread register values
will fail with same error.
#Find frame of tested method on the thread stack
#sun.jvm.hotspot.debugger.DebuggerException: sun.jvm.hotspot.debugger.DebuggerException: get_thread_regs failed for a lwp
# at sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal$LinuxDebuggerLocalWorkerThread.execute(LinuxDebuggerLocal.java:134)
# at sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal.getThreadIntegerRegisterSet(LinuxDebuggerLocal.java:437)
# at sun.jvm.hotspot.debugger.linux.LinuxThread.getContext(LinuxThread.java:48)
# at sun.jvm.hotspot.runtime.linux_x86.LinuxX86JavaThreadPDAccess.getCurrentFrameGuess(LinuxX86JavaThreadPDAccess.java:75)
# at sun.jvm.hotspot.runtime.JavaThread.getCurrentFrameGuess(JavaThread.java:238)
# at sun.jvm.hotspot.runtime.JavaThread.getLastJavaVFrameDbg(JavaThread.java:197)
# at sun.jvm.hotspot.jdi.ThreadReferenceImpl.privateFrames(ThreadReferenceImpl.java:197)
# at sun.jvm.hotspot.jdi.ThreadReferenceImpl.frames(ThreadReferenceImpl.java:167)
# at nsk.sajdi.VMCannotBeModifiedException.thrown.thrown003.runIt(thrown003.java:118)
# at nsk.sajdi.VMCannotBeModifiedException.thrown.thrown003.run(thrown003.java:26)
# at nsk.sajdi.VMCannotBeModifiedException.thrown.thrown003.main(thrown003.java:21)