Hi David,
On 2020/09/02 14:00, David Holmes wrote:
Hi Yasumasa,
On 1/09/2020 11:42 pm, Yasumasa Suenaga wrote:
Hi all,
Please review this change:
JBS: https://bugs.openjdk.java.net/browse/JDK-8252657
webrev: http://cr.openjdk.java.net/~ysuenaga/JDK-8252657/webrev.00/
I tried to attach JVMTI agent which returns JNI_ERR in Agent_OnUnload via
JVMTI.agent_load dcmd. I expected the library would be unloaded, but I saw it
in VM.dynlibs dcmd even though it was failed to load.
I'm not so sure there is a bug here. The specification is quite lax:
"Instead the VM ignores the error, or takes some implementation specific action --
for example it might print an error to standard error, or record the error in a system
log. "
I think this spec says about VM behavior only. For example, if Agent_OnAttach
is failed, the action in VM is not specified.
So not unloading the library is not a bug in respect of the specification.
Further by unloading the library do you not now permit it to be re-loaded and
the OnAttach function to be executed repeatedly? That seems wrong to me. It
could also be argued that if you will re-execute onAttach then you should first
have called OnUnload, which you don't do.
Administrator can retry to attach agent with another options if it was failed.
Currently we can attach same agent to one JVM as many times as we like. Of
course Agent_OnAttach would be called in each attach operation.
JVMTI agent might have entry point (e.g. DllMain in Windows) and it might work
something (e.g. multiple launch check). In addition it is strange agent library
exists even if AgentLibrary is discarded when Agent_OnAttach is failed - nobody
would not manage it!
Cheers,
Yasumasa
So while this current behaviour may not meet with your expectations it is not a
bug per-se, and the change in behaviour could have other implications that are
not insignificant.
If the new behaviour is considered desirable then a CSR request should also be
filed for this.
Cheers,
David
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Please see JBS how to reproduce.
Thanks,
Yasumasa
