Find a strange problem about using project-panama on macos

[David Holmes]

On 14/08/2023 2:45 pm, David Holmes wrote:
> 
> 
> On 14/08/2023 12:42 pm, 刘希晨 wrote:
>>
>> I have found a really strange problem when using project-panama on 
>> macos, and it might be a bug.
>>
>> *Environment*: JDK-21 ea build 34, cpu : M1 Pro, operating system : 
>> Ventura 13.5
>>
>> Here are the minimal reproducible codes:
>>
>> public class SimpleExample {
>>      public static void main(String[] args)throws Throwable {
>>          SymbolLookup crypto = 
>> SymbolLookup.libraryLookup("/Users/liuxichen/workspace/tenet-lib/lib/libcrypto.dylib", Arena.global());
>>          Thread.sleep(Long.MAX_VALUE);
>>      }
>> }
>>
>> The libcrypto.dylib file is the OPENSSL dynamic library file, I think 
>> other libraries probably could cause the same problem.
>>
>> *Problem description*:
>> A normal java program would work fine with *jconsole* and *jmap*, if 
>> running the above code in macos, jconsole won't be able to connect to 
>> the target process, and jmap will give the following error:
>>
>> *~/Dow/jdk-21/C/H/bin  jps*
>>
>> 1665 RemoteMavenServer36
>> 2673 Jps
>> 532
>> 1671 Launcher
>> 1672 SimpleExample
>> 1211
>>
>>
>> * ~/Dow/jdk-21/C/H/bin  ./jmap -histo:live,file=histo5.data 1672*
>>
>> Exception in thread"main" 
>> com.sun.tools.attach.AttachNotSupportedException: Unable to open 
>> socket file 
>> /var/folders/k4/j5wzcbnd3m96s5lmqw_8lh8r0000gn/T/.java_pid1672: target 
>> process1672 doesn't respond within 10500ms or HotSpot VM not loaded
>> at 
>> jdk.attach/sun.tools.attach.VirtualMachineImpl.<init>(VirtualMachineImpl.java:95)
>>      at 
>> jdk.attach/sun.tools.attach.AttachProviderImpl.attachVirtualMachine(AttachProviderImpl.java:58)
>>      at 
>> jdk.attach/com.sun.tools.attach.VirtualMachine.attach(VirtualMachine.java:207)
>>      at jdk.jcmd/sun.tools.jmap.JMap.executeCommandForPid(JMap.java:127)
>>      at jdk.jcmd/sun.tools.jmap.JMap.histo(JMap.java:199)
>>      at jdk.jcmd/sun.tools.jmap.JMap.main(JMap.java:112)
> 
> These problems, and the workaround, suggest that a thread is preventing 
> the VM from going to safepoint, but I can't see why that should be the 
> case. If you apply the StartAttachListener workaround what does jstack 
> show you is happening?

Actually if the VM can't reach a safepoint then jstack won't be able to 
run either. You need to run a native debugger against the process and 
get the stack traces.

David
------

> David
> -----
> 
>>
>> Several tests:
>> 1. The above code runs fine on windows and macos, and the process 
>> could be accessed by jconsole and jmap on windows, only fail on macos
>> 2. The problem could be solved by adding VM options, for jconsole 
>> usable, add -Dcom.sun.management.jmxremote for jmap usable add 
>> -XX:+StartAttachListener , if there is no 
>> *SymbolLookup.libraryLookup*(), then jconsole and jmap would work well 
>> without these two arguments
>>
>> So, I guess there must be some internal logic that blocks the jconsole 
>> and jmap from entering java program inside 
>> *SymbolLookup.libraryLookup*(), please correct me if I am wrong
>>
>>
>>