See the JBS issue for a problem description. This patch changes the shared scope closure handshake to be able to handle 'arbitrary' Java frames on the stack during a scoped memory access.
For the purposes of this change, we assume that 'arbitrary' is limited to the following: 1. Frames added by calling the constructor of `InternalError` as a result of a faulting access to a truncated memory-mapped file (see `HandshakeState::handle_unsafe_access_error`). This is the only handshake operation (i.e. may be triggered during a scoped access) that calls back into Java. 2. Frames added by a JVMTI agent that calls back into Java code while handling a JVMTI event that happens during a scoped access. 3. Any other Java code that runs as part of the linking process. For (1), we set a flag while we are create the `InternalError`. If a thread has that flag set, we know it is in the process of crashing already, so we don't have to inspect the stack at all. For (2), all bets are off, so we have to walk the entire stack. For (3), this patch switches the hard limit of 10 frames for the stack walk to instead bail out at the first frame outside of the `java.base` module. In most cases this speeds up the stack walk as well, if threads are running other code. The test `TestSharedCloseJFR` is added for scenario (1), and the test `TestSharedCloseJvmti` is added for scenario (2). Existing tests already cover scenario (3). Testing: tier 1-4 ------------- Commit messages: - Make JVMTI test reentrant - Remove jdk.jfr vm symbol again - Use _throwing_unsafe_access_error flag to bail out of stack walk - Clarify comment - Merge branch 'master' into NewStackWalk - Whitelist jdk.jfr as well - Simplify BM - Add assert - Add reproducer - Polish - ... and 3 more: https://git.openjdk.org/jdk/compare/a0e0b2d3...fb01850d Changes: https://git.openjdk.org/jdk/pull/27919/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27919&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8370344 Stats: 552 lines in 10 files changed: 534 ins; 5 del; 13 mod Patch: https://git.openjdk.org/jdk/pull/27919.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/27919/head:pull/27919 PR: https://git.openjdk.org/jdk/pull/27919
