> Hi, please consider the following changes: > > If suspension is allowed when a thread is re-entering an object monitor (OM), > then a deadlock is possible. There are two places where it can happen: > > 1) The waiting thread is made to be a successor and is unparked. Upon a > suspension request, the thread will suspend itself whilst clearing the > successor. The OM will be left unlocked (not grabbed by any thread), while > the other threads are parked until a thread grabs the OM and the exits it. > The suspended thread is on the entry-list and can be selected as a successor > again. None of other threads can be woken up to grab the OM until the > suspended thread has been resumed and successfully releases the OM. > > 2) The race between suspension and retry: the thread could reacquire the OM > and complete the wait() code in full, but then on return to Java it will be > suspended while holding the OM. > > The issues are addressed by not allowing suspension in case 1, and by > handling the suspension request at a later stage, after the thread has > grabbed the OM in `reenter_internal()` in case 2. In case of a suspension > request, the thread exits the OM and enters it again once resumed. > > The JVMTI `waited` event posting (2nd one) is postponed until the suspended > thread is resumed and has entered the OM again. The `enter` to the OM (in > case `ExitOnSuspend` did exit) is done without posting any events. > > Tests are added for both scenarios. > > Tested in tiers 1 - 7.
Anton Artemov has updated the pull request incrementally with one additional commit since the last revision: 8366659: Added a comment to a boolean arg for enter() ------------- Changes: - all: https://git.openjdk.org/jdk/pull/27040/files - new: https://git.openjdk.org/jdk/pull/27040/files/ba667e37..e84dca9d Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=27040&range=02 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27040&range=01-02 Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod Patch: https://git.openjdk.org/jdk/pull/27040.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/27040/head:pull/27040 PR: https://git.openjdk.org/jdk/pull/27040
