On Wed, 23 Oct 2024 20:36:23 GMT, Patricio Chilano Mateo <pchilanom...@openjdk.org> wrote:
>> Sorry, I should add context on why this is needed. The problem is that >> inside this temporal transition we could try to acquire some monitor. If the >> monitor is not inflated we will try to use the LockStack, but the LockStack >> might be full from monitors the virtual thread acquired before entering this >> transition. Since the LockStack is full we will try to make room by >> inflating one or more of the monitors in it [1]. But when inflating the >> monitors we would be using the j.l.Thread.tid of the carrier (set into >> _lock_id when switching the identity), which is wrong. We need to use the >> j.l.Thread.tid of the virtual thread, so we need to change _lock_id back. >> We are not really unmounting the virtual thread, the only thing that we want >> is to set the identity to the carrier thread so that we don't end up in this >> nested calls to parkNanos. >> >> [1] >> https://github.com/openjdk/jdk/blob/afb62f73499c09f4a7bde6f522fcd3ef1278e526/src/hotspot/share/runtime/lightweightSynchronizer.cpp#L491 > >> Also JavaThread::_lock_id in the VM means "the java.lang.Thread thread-id to >> use for locking" - correct? >> > Yes. I guess I don't understand where this piece code fits in the overall transition of the virtual thread to being parked. I would have expected the LockStack to already have been moved by the time we switch identities to the carrier thread. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/21565#discussion_r1814167842
