On Mon, 12 May 2025 14:46:44 GMT, Aleksey Shipilev <sh...@openjdk.org> wrote:
>> https://openjdk.org/jeps/483 mentions: >> >>> To enjoy the benefits of the AOT cache generated during a training run, the >>> training run and all subsequent runs must be essentially similar. [...] All >>> runs must not use JVMTI agents that can arbitrarily rewrite classfiles >>> using ClassFileLoadHook. >> >> However, when *any* java agent is specified in the training run, the JVM >> fails at start-up. E.g., >> >> >> $ java -XX:AOTMode=record -javaagent:agent.jar -cp app.jar App >> Error occurred during CDS dumping >> Must enable AllowArchivingWithJavaAgent in order to run Java agent during >> CDS dumping >> >> >> With the AOT cache, the main concern for JVMTI agents is that they can >> modify the contents of loaded Java classes. If we store such modified >> classes into the AOT cache, their contents will no longer match the original >> class files (from application JAR files, etc). As a result, when using the >> AOT cache in production runs, the application may have unexpected behavior. >> >> With this PR, we allow JVMTI agents in the AOT workflow. To address the >> above concern, we ensure that JVMTI agents cannot affect the contents of AOT >> cache: >> >> - In training runs (`java -XX:AOTMode=record`), JVMTI agents are allowed, >> but the AOT configuration file should filter out classes that are >> transformed by the agents. This can be checking >> `InstanceKlass::has_been_redefined()` and >> `ClassFileStream::from_class_file_load_hook()`. >> >> - In the assembly phase (`java -XX:AOTMode=record`), agents can be specified >> in the command-line. However, since the assembly phase doesn't execute any >> application logic, we will also not load any of the specified agents. >> Therefore, the agents cannot affect the contents of the AOT cache created in >> the assembly phase. > > src/hotspot/share/prims/jvmtiAgent.cpp line 588: > >> 586: // Agents are allowed with -XX:AOTMode=record and >> -XX:AOTMode=on/auto. >> 587: // Agents are completely disabled when -XX:AOTMode=create >> 588: assert(!CDSConfig::is_dumping_final_static_archive(), "agents >> should have been disabled with -XX:AOTMode=create"); > > Is there a point in asserting this? I am thinking users would pass the same > command line to `-XX:AOTMode=create` without thinking twice. And since we are > doing the right thing, ignoring the agents, it seems we "only" need to print > the user-visible warning. Maybe not even that, and just return? If someone removes the call to `JvmtiAgentList::disable_agent_list()`, we will come to here and exit the JVM. This assert is to guard against that. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/25170#discussion_r2085127224
