> This PR adds ranked monitor support to the debug agent. The debug agent has a > large number of monitors, and it's really hard to know which order to grab > them in, and for that matter which monitors might already be held at any > given moment. By imposing a rank on each monitor, we can check to make sure > they are always grabbed in the order of their rank. Having this in place when > I was working on [JDK-8324868](https://bugs.openjdk.org/browse/JDK-8324868) > would have made it much easier to detect a deadlock that was occuring, and > the reason for it. That's what motivated me to do this work > > There were 2 or 3 minor rank issues discovered as a result of these changes. > I also learned a lot about some of the more ugly details of the locking > support in the process. > > Tested with the following on all supported platforms and with virtual threads: > > com/sun/jdi > vmTestbase/nsk/jdi > vmTestbase/nsk/jdb > vmTestbase/nsk/jdwp > > Still need to run tier2 and tier5. > > Details of the changes follow in the first comment.
Chris Plummer has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 24 commits: - merge - add newline before dumping raw monitors - Dump raw monitors as part of JVMTI DataDumpRequest event - Merge - Fix some rank orders after merge with 8332738. - tweak to raw monitor dump output - Merge - Fix a couple of minor typos in comments. - Simplify by getting rid of special logic around leaf monitors. - Flip rank order. Some cleanup and better comments for verifyMonitorRank(). - ... and 14 more: https://git.openjdk.org/jdk/compare/53db5764...f1105055 ------------- Changes: https://git.openjdk.org/jdk/pull/19044/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19044&range=12 Stats: 607 lines in 11 files changed: 544 ins; 2 del; 61 mod Patch: https://git.openjdk.org/jdk/pull/19044.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/19044/head:pull/19044 PR: https://git.openjdk.org/jdk/pull/19044
