RFR: JDK-8265298: Hard VM crash when deadlock between "access" and higher ranked lock is detected

[Xin Liu]

On Thu, 15 Apr 2021 16:56:31 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> I stumbled upon this when doing some Shenandoah work. The development code tried to lock the `leaf` lock, while already holding the `access` lock. Normally it would have been detected by VM, but instead, we tried to recursively acquire `tty_lock` for `Thread::print_owned_locks`. But that `tty` lock is still ranked higher than `access`, so deadlock detection triggers over and over again until we run out of stack and crash hard. `tty` and `access` are ranked this way because of [JDK-8214315](https://bugs.openjdk.java.net/browse/JDK-8214315). Read the rest in the bug.  
> 
> I believe the way out is to only enter `Thread::print_owned_locks` when we know deadlock detection code would not run in circles. New test for `access` and `leaf` shows the original failure. Another new test checks `tty` and `special` to verify that the check should be `> tty`, not `>= tty`.
> 
> Additional testing:
>  - [x] Linux x86_64 fastdebug tier1
>  - [x] New regression tests (fail without the patch, pass wit it)

src/hotspot/share/runtime/mutex.cpp line 416:

> 414:     if (least != NULL && least->rank() <= this->rank()) {
> 415:       if (least->rank() > Mutex::tty) {
> 416:         // Printing owned locks acquires tty lock. If lowest rank is below or equal

If the least* rank was* below or equal tty,

-------------

PR: https://git.openjdk.java.net/jdk/pull/3524