> 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 incrementally with eight additional commits since the last revision: - Minor comment fix in debugMonitorCreate() - Don't do anything in assertIsCurrentThread() if asserts are disabled - Print threads names instead of addresses in assertIsCurrentThread() - Renamed thread -> savedOwnerThread and entryCount -> savedEntryCount. - pass already fetched current_thread to assertIsCurrentThread() - dbgRawMonitor reference should be dbg_monitor->monitor in dumpRawMonitors() - Free localrefs allocated by GetThreadInfo(). - Optimize loop iterations during rank verification. ------------- Changes: - all: https://git.openjdk.org/jdk/pull/19044/files - new: https://git.openjdk.org/jdk/pull/19044/files/bcb92b59..ece5f34f Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=19044&range=01 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=19044&range=00-01 Stats: 46 lines in 1 file changed: 19 ins; 11 del; 16 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
