> In JDK-8311218, processing of self suspend operations was deferred while > holding the `interruptLock` monitor of a virtual thread to avoid possible > deadlocks. In particular, suspending a thread while holding the > `interruptLock` of a given virtual thread would cause that virtual thread to > block in `VirtualThread.unmount`, preventing it from completing the unmount > transition. That in turn would block the resumer thread, since it needs to > wait until no virtual thread is in a transition, leading to a deadlock. We > need to do the same deferral in `MountUnmountDisabler::start_transition`, as > this is also a suspend-checking point. > > There are no obvious unmount points leading to > `MountUnmountDisabler::start_transition` while in these critical regions. But > with the changes in JDK-8369238, class initialization was added to the set of > possibilities. In fact, I was able to create a test that reproduces the > deadlock by triggering contention during initialization of class > `java.util.Locale` in `appendCarrierInfo`. Regardless of this case though, > the `VirtualThread` code could change so we need to guard against this. > > Together with JDK-8375362, this issue shows that we need to skip the suspend > check for the same cases where we skip processing of self suspend operations > in the handshake code. So I grouped these together under > `should_defer_self_suspend` and updated the relevant call sites. > > The patch includes a test that deadlocks as described above without this fix. > I also tested the changes in mach5 tiers1-6. > > Thanks, > Patricio > > --------- > - [x] I confirm that I make this contribution in accordance with the [OpenJDK > Interim AI Policy](https://openjdk.org/legal/ai).
Patricio Chilano Mateo has updated the pull request incrementally with one additional commit since the last revision: add explicit thread->is_disable_suspend() checks ------------- Changes: - all: https://git.openjdk.org/jdk/pull/31281/files - new: https://git.openjdk.org/jdk/pull/31281/files/6637bbe2..6b9a0a79 Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=31281&range=01 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=31281&range=00-01 Stats: 13 lines in 4 files changed: 4 ins; 4 del; 5 mod Patch: https://git.openjdk.org/jdk/pull/31281.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/31281/head:pull/31281 PR: https://git.openjdk.org/jdk/pull/31281
