On Thu, 8 Feb 2024 13:46:40 GMT, Markus Grönlund <mgron...@openjdk.org> wrote:
> Greetings, > > The following adjustments fix the intermittent issues with incomplete tag > sets for a chunk. The situations are pretty subtle: > > 1. A situation can occur where an event is emitted during the event > instrumentation callback as part of JVMTI Retransform (ErrorThrownEvent). A > stack trace is captured that marks, or "tags", the existing method(s) of the > klass (i.e. when the scratch class is instrumented). But after the > instrumentation call returns, the set of methods of the klass is exchanged > from the "old" methods (now marked) , to the new set of methods (from the > scratch class, not marked). This means the mark/tag is lost for a method. > Therefore, method tags must be transferred when exchanging methods during > JVMTI redefine / retransform. > 2. OldObjectSample events are emitted at the end of a recording. As part of > writing the events, several checkpoint events are also created and enqueued. > But these checkpoints are incomplete standalone because they need to be > complemented with a typeset checkpoint, which happens just after, as part of > the rotation. But flush() can occur concurrently with OldObjectSample emit, > and can, therefore, serialize these checkpoints to a segment before the > complementary typeset checkpoint has been created. There needs to be mutual > exclusion between OldObjectSample emit() and flush(), now provided by the > JfrRotationLock. > 3. The set of artefacts captured during class unloading is incomplete because > it respects already serialized artefacts. However, because class unloading > typesets are linked to OldObjectSamples and DeprecatedInvocation events, > which survive chunk boundaries, these unloading typesets can be serialized in > later chunks. If the unloading set is incomplete (not transitive), there will > be missing constants. Hence, class unloading typesets require serialization > of the entire transitive set of unloading artefacts, even if they have > already been serialized to the current chunk. > > As part of fixing these issues, the disabled assert is also reactivated. > > Testing: jdk_jfr, stress testing, tier 1-6 > > Thanks > Markus This pull request has now been integrated. Changeset: 737b4c51 Author: Markus Grönlund <mgron...@openjdk.org> URL: https://git.openjdk.org/jdk/commit/737b4c515e082239579369d9806307b9f16c4816 Stats: 166 lines in 15 files changed: 81 ins; 48 del; 37 mod 8323883: JFR AssertionError: Missing object ID 15101 Reviewed-by: egahlin ------------- PR: https://git.openjdk.org/jdk/pull/17771
