On Fri, 12 Jul 2024 02:44:28 GMT, David Holmes <dhol...@openjdk.org> wrote:
>> Chris Plummer has updated the pull request incrementally with one additional >> commit since the last revision: >> >> Fix copyright and jcheck error > > test/hotspot/jtreg/vmTestbase/nsk/jdi/ThreadReference/resume/resume001.java > line 382: > >> 380: if (expresult != returnCode0) { >> 381: vm.resume(); >> 382: vm.resume(); // for case error when both >> VirtualMachine and the thread2 were suspended > > Pre-existing but I don't understand the comment. Why would you need 2 > `vm.resume()` here? If `thread2` was suspended directly don't you need a > `thread2.resume()`? First just to clarify a general JDI feature about thread suspending and resuming. You can undo a ThreadReference.suspend() or a thread suspended as the result of an event by dong a vm.resume(). This is documented in the JDI API spec, which talks about suspendCounts and how various APIs and event delivery affect them. I was tempted to clean up these vm.resume() calls but opted not to. The point being made in the comment is that worse case thread2 was suspended by a breakpoint or thread2.suspend() and all threads were suspended by a vm.resume() (meaning thread2 could have a suspendCount of 2). Two vm.resumes() take are done to make sure thread2 gets resumed under this situation. However, one of the vm.resume calls could instead be a thread2.resume(). Doing two vm.resume() calls was probably just laziness by the original authors. It works though. However, by my accounting at any failure point thread2 never has a suspendCount > 1, so really just one vm.resume() would be enough. The original code did these two vm.resume() calls unconditionally, but they are not needed if there was no error. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/20088#discussion_r1675243246