RFR: 8339307: jhsdb jstack could not trace FFM upcall frame [v4]

[Chris Plummer]

On Mon, 2 Sep 2024 10:29:40 GMT, Yasumasa Suenaga <ysuenaga at openjdk.org> wrote:

>> I attempted to check stack trace in the core generated by [SEGV example in upcall](https://github.com/YaSuenag/garakuta/blob/841452d9176dab1ddbb552009c180530eb81190b/NativeSEGV/ffm/upcall/src/main/java/com/yasuenag/garakuta/nativesegv/upcall/Main.java) with `jhsdb jstack`, however it failed with following exception.
>> 
>> 
>> Error occurred during stack walking:
>> java.lang.RuntimeException: Couldn't deduce type of CodeBlob @0x00007fa04c265990 for PC=0x00007fa04c265aa6
>>         at jdk.hotspot.agent/sun.jvm.hotspot.code.CodeCache.findBlobUnsafe(CodeCache.java:124)
>>         at jdk.hotspot.agent/sun.jvm.hotspot.code.CodeCache.findBlob(CodeCache.java:83)
>>         at jdk.hotspot.agent/sun.jvm.hotspot.runtime.Frame.cb(Frame.java:119)
>>         at jdk.hotspot.agent/sun.jvm.hotspot.runtime.x86.X86Frame.adjustUnextendedSP(X86Frame.java:334)
>>         at jdk.hotspot.agent/sun.jvm.hotspot.runtime.x86.X86Frame.initFrame(X86Frame.java:137)
>>         at jdk.hotspot.agent/sun.jvm.hotspot.runtime.x86.X86Frame.<init>(X86Frame.java:163)
>>         at jdk.hotspot.agent/sun.jvm.hotspot.runtime.x86.X86Frame.senderForInterpreterFrame(X86Frame.java:361)
>>         at jdk.hotspot.agent/sun.jvm.hotspot.runtime.x86.X86Frame.sender(X86Frame.java:281)
>>         at jdk.hotspot.agent/sun.jvm.hotspot.runtime.Frame.sender(Frame.java:207)
>>         at jdk.hotspot.agent/sun.jvm.hotspot.runtime.Frame.realSender(Frame.java:212)
>>         at jdk.hotspot.agent/sun.jvm.hotspot.runtime.VFrame.sender(VFrame.java:120)
>>         at jdk.hotspot.agent/sun.jvm.hotspot.runtime.VFrame.javaSender(VFrame.java:144)
>>         at jdk.hotspot.agent/sun.jvm.hotspot.tools.StackTrace.run(StackTrace.java:81)
>>         at jdk.hotspot.agent/sun.jvm.hotspot.tools.StackTrace.run(StackTrace.java:45)
>>         at jdk.hotspot.agent/sun.jvm.hotspot.tools.JStack.run(JStack.java:67)
>>         at jdk.hotspot.agent/sun.jvm.hotspot.tools.Tool.startInternal(Tool.java:278)
>>         at jdk.hotspot.agent/sun.jvm.hotspot.tools.Tool.start(Tool.java:241)
>>         at jdk.hotspot.agent/sun.jvm.hotspot.tools.Tool.execute(Tool.java:134)
>>         at jdk.hotspot.agent/sun.jvm.hotspot.tools.JStack.runWithArgs(JStack.java:90)
>>         at jdk.hotspot.agent/sun.jvm.hotspot.SALauncher.runJSTACK(SALauncher.java:302)
>>         at jdk.hotspot.agent/sun.jvm.hotspot.SALauncher.main(SALauncher.java:500)
>> Caused by: sun.jvm.hotspot.types.WrongTypeException: No suitable match for type of address 0x00007fa04c265990 (nearest symbol is _ZTV10Upcall...
>
> Yasumasa Suenaga has updated the pull request incrementally with three additional commits since the last revision:
> 
>  - Update test/hotspot/jtreg/serviceability/sa/LingeredAppWithFFMUpcall.java
>    
>    Co-authored-by: Andrey Turbanov <turbanoff at gmail.com>
>  - Update test/hotspot/jtreg/serviceability/sa/LingeredAppWithFFMUpcall.java
>    
>    Co-authored-by: Andrey Turbanov <turbanoff at gmail.com>
>  - Update test/hotspot/jtreg/serviceability/sa/LingeredAppWithFFMUpcall.java
>    
>    Co-authored-by: Andrey Turbanov <turbanoff at gmail.com>

test/hotspot/jtreg/serviceability/sa/TestJhsdbJstackUpcall.java line 49:

> 47:      * Test should focus JNI call (caller of upcall) because the frame
> 48:      * prior to the upcall cannot be obtained if some exception happens
> 49:      * in during to process upcall.

2 questions here. Shouldn't we also check for the java frame that the upcall was mode to. 2nd is why are we worried about an exception here.

test/hotspot/jtreg/serviceability/sa/TestJhsdbJstackUpcall.java line 51:

> 49:      * in during to process upcall.
> 50:      */
> 51:     private static boolean isJNIFrame(List<String> lines) {

I think this method could use a better name like hasFFMUpcall().

test/hotspot/jtreg/serviceability/sa/TestJhsdbJstackUpcall.java line 57:

> 55: 
> 56:     private static void runJstackInLoop(LingeredApp app) throws Exception {
> 57:         for (int i = 0; i < MAX_ITERATIONS; i++) {

What is the reason for doing 20 iterations. Is it because you are waiting for THREAD_NAME to enter the sleep() call? If so, we've addressed this in the past for the general case of wanting to do a "stable"stack trace by using the LingeredApp's SteadyStateThread. LingeredApp.startApp() will not return until this thread has become stable (blocked). Maybe you can do something similar with THREAD_NAME.

test/hotspot/jtreg/serviceability/sa/TestJhsdbJstackUpcall.java line 76:

> 74:             out.shouldContain(LingeredAppWithFFMUpcall.THREAD_NAME);
> 75:             if (isJNIFrame(out.asLines())) {
> 76:                 System.out.println("DEBUG: Test triggered interesting condition.");

I'm not so sure what is meant by "intersting condition". Perhaps you mean "detected FFM upcall" or something like that.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/20789#discussion_r1742592058
PR Review Comment: https://git.openjdk.org/jdk/pull/20789#discussion_r1742590621
PR Review Comment: https://git.openjdk.org/jdk/pull/20789#discussion_r1742584621
PR Review Comment: https://git.openjdk.org/jdk/pull/20789#discussion_r1742588694