On Fri, 2 Oct 2020 06:30:34 GMT, Serguei Spitsyn <[email protected]> wrote:
> * Q1: Is it necessary to call the Agent_OnUnload()? [JVMTI spec of Agent_OnUnload()](https://docs.oracle.com/en/java/javase/15/docs/specs/jvmti.html#onunload) says this function will be called when the agent library will be unloaded by platform specific mechanism. OTOH it also says `Agent_OnUnload()` will be called both at VM termination and **by other reasons**. The spec don't say for the case if `Agent_OnAttach()` would be failed. IMHO `Agent_OnUnload()` should be called because this PR would unload library if `Agent_OnAttach()` failed. > * Q2: Would it be a JVMTI spec violation to call the Agent_OnAttach() > multiple times? (It seems to be the case to me.) `Agent_OnAttach()` should be called only once per attach request, but VM should accept multiple attach request for same agent library. For example, we can add multiple `-agentlib` and `-agentpath` request as below. JVMTI agent might change behavior due to arguments or configuration file. -agentlib:test=profile=A -agentlib:test=profile=B -agentpath:/path/to/libtest=profile=C Agent developers should have responsibility for the behavior when more than one agent is loaded at a time. > * Q3: What has to be done for statically linked agent? JVMTI spec says "unless it is statically linked into the executable", so I think we can ignore about Agent_OnUnload_L() in this PR. > * Q4: Should the agent be correctly loadable in the first place? What were > the reasons its loading to fail? Agent (`Agent_OnAttach()`) might fail due to error in agent logic. For example, some agents load configuration file at initialization. If the user gives wrong value, it will fail. > Yes, at least, a CSR is needed for this. I will file CSR for this PR after this discussion. ------------- PR: https://git.openjdk.java.net/jdk/pull/19
