On Tue, 6 Apr 2021 11:56:36 GMT, Robbin Ehn <r...@openjdk.org> wrote:
> > > I do not follow, the OM is unrelated. > The suspender do not hold the OM. > > What happens is: > > * Thread A wait on OM X in blocked. > > * Thread Z suspends Thread A, thread Z have no relation to OM X. > > * Thread B unlocks OM X, thread B have no relation to the suspend request. > > * Thread A locks OM X while blocked. > > * Thread A was not allowed to lock OM X due to it is actually suspended. > > * Thread A unlocks OM X and waits until resumed. > > > So while A and B fight over OM X, A is trying to figure out if Z suspended > him while grabbing the lock. If understand the example correctly then the suspend operation and the operations on OM X are unordered with respect to each other. If so, then we can put them into an order where the suspend happens after "Thread A locks OM X while blocked.". We are free to do this; there's no synchronization that would prevent it. Also when the suspend request happened while A was blocked then after `current->set_thread_state_fence(_thread_blocked_trans);` the check of `is_suspended()` will return true even if the handshake state lock is not acquired for the check. And if Z tried to suspend A after the state change then Z will block because A is not safe anymore. Sorry for insisting. I really hope I'm not wrong ;) ------------- PR: https://git.openjdk.java.net/jdk/pull/3191
