Find a strange problem about using project-panama on macos

[David Holmes]

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?

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
> 
> 
>