RFR 8159284: bigapps/Jetty - assert(jfa->last_Java_sp() > sp()) failed with tracing code in use

[dean.long at oracle.com]

Hi Coleen.  If I understand correctly, previously we would get 
backtraces that end with the first C frame:

[...]
J 3335 C1 java.lang.Thread.run()V java.base at 9-ea (17 bytes) @ 0xe7fdc480 [0xe7fdc420+0x00000060]
v  ~StubRoutines::call_stub
V  [libjvm.so+0x66fe39]  JavaCalls::call_helper(JavaValue*, methodHandle const&, JavaCallArguments*, Thread*)+0x2b9
V  [libjvm.so+0x931669]  os::os_exception_wrapper(void (*)(JavaValue*, methodHandle const&, JavaCallArguments*, Thread*), JavaValue*, methodHandle const&, JavaCallArguments*, Thread*)+0x19
V  [libjvm.so+0x66eb2b]  JavaCalls::call_virtual(JavaValue*, Handle, KlassHandle, Symbol*, Symbol*, Thread*)+0x13b
V  [libjvm.so+0x708069]  thread_entry(JavaThread*, Thread*)+0x89
V  [libjvm.so+0xaa5434]  JavaThread::thread_main_inner()+0xf4
V  [libjvm.so+0xaa5589]  JavaThread::run()+0x119
V  [libjvm.so+0x933cdc]  thread_native_entry(Thread*)+0x10c
C  [libpthread.so.0+0x6bc9]
C  [libc.so.6+0xe2c9e]  clone+0x5e


but now with your change, won't all backtraces end on the last Java 
frame?  So the above backtrace would be truncated to:

[...]
J 3335 C1 java.lang.Thread.run()V java.base at 9-ea (17 bytes) @ 0xe7fdc480 [0xe7fdc420+0x00000060]


dl

On 8/1/16 4:38 PM, Coleen Phillimore wrote:
> Summary: Test condition in assert in frame::safe_for_sender() for 
> entry frames and return false.
>
> This bug is for a confidential part of the project that needs more 
> robustness checks to verify that frame::sender() can be called.
>
> Also refactored into frame::entry_frame_is_safe() because these 
> platforms had the same code for entry frames to determine whether it 
> is still safe to trust this frame to call sender(). These platforms 
> had also the same assert in sender_for_entry_frame() that the sampling 
> code hit.
>
> Tested with our nightly tests on all platforms and bigapps/Jetty.
>
> open webrev at http://cr.openjdk.java.net/~coleenp/8159284.01/webrev
>
> Thanks,
> Coleen
>