RFR: 8232592: <Unknown compiled code> is shown in jstack mixed mode

[Chris Plummer]

Hi Yasumasa,

The call to getJavaNames() is not needed if the method is native. It 
should be moved into the else block:

                             if (cb.isNMethod()) {
                                if (cb.isNativeMethod()) {
out.print(((CompiledMethod)cb).getMethod().externalNameAndSignature());
                                   long diff = pc.minus(cb.codeBegin());
                                   if (diff != 0L) {
                                     out.print(" + 0x" + 
Long.toHexString(diff));
                                   }
                                   out.println(" (Native method)");
                                } else {
                                    names = getJavaNames(th, 
f.localVariableBase());
                                    if (names == null || names.length == 
0) {
                                        // just print compiled code, if 
can't determine method
out.println("<Unknown compiled code>");
                                    }
                                }
                             } else if (cb.isBufferBlob()) {

So what does it mean if it is an NMethod but is not native and names != 
null. Should this ever happen? It seems odd that we don't print out the 
frame type in this case, and also don't call printUnknown().

thanks,

Chris

On 10/18/19 1:38 AM, Yasumasa Suenaga wrote:
> Hi all,
>
> Please review this change.
>
>   JBS: https://bugs.openjdk.java.net/browse/JDK-8232592
>   webrev: http://cr.openjdk.java.net/~ysuenaga/JDK-8232592/webrev.00/
>
> I run `jhsdb jstack --mixed` to JShellToolProvider process, then I saw 
> <Unknown compiled code>
> in the stack as below:
>
> ```
> "process reaper" #13 daemon prio=10 tid=0x00007f959c328000 nid=0x1285 
> runnable [0x00007f9578025000]
>    java.lang.Thread.State: RUNNABLE
>    JavaThread state: _thread_in_native
> 0x00007f95a27c5596 __waitpid + 0x56
> 0x00007f958c601d79 <Unknown compiled code>
> 0x00007f9585c5b4ac * java.lang.ProcessHandleImpl$1.run() bci:8 
> line:138 (Compiled frame)
> ```
>
> 0x7f958c601d79 is native method. jstack mixed mode should handle it.
> This patch passed all tests on submit repo 
> (mach5-one-ysuenaga-JDK-8232592-20191018-0600-6011163).
>
>
> Thanks,
>
> Yasumasa