On Tue, 1 Dec 2020 01:43:15 GMT, Chris Plummer <cjplum...@openjdk.org> 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. > >> > * 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. > > I don't think that makes sense. If you call it for dynamically linked then > you need to call it for statically linked also. @dholmes-ora Thank you for explanation! I updated [CSR](https://bugs.openjdk.java.net/browse/JDK-8256918). Could you review it? ------------- PR: https://git.openjdk.java.net/jdk/pull/19
