RFR: 8263551: Provide shared lock-free FIFO queue implementation

[Man Cao]

On Sat, 13 Mar 2021 10:41:44 GMT, Man Cao <manc at openjdk.org> wrote:

> Hi all,
> 
> Could anyone review this change that is mainly code motion? It creates a generalized lock-free queue implementation based on G1DirtyCardQueueSet::Queue, which will be used by JDK-8236485 in the future.
> 
> The shared LockFreeQueue is similar to the existing LockFreeStack. The notable difference is that the LockFreeQueue has an additional template parameter for whether to use GlobalCounter::CriticalSection to avoid ABA problem.
> 
> -Man

src/hotspot/share/utilities/lockFreeQueue.hpp line 99:

> 97:     } else {
> 98:       assert(get_next(*old_tail) == NULL, "invariant");
> 99:       Atomic::store(next_ptr(*old_tail), &first);

I changed this store from a normal store to an Atomic store. Otherwise there is a data race between this store and the load of _head->_next in pop().

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PR: https://git.openjdk.java.net/jdk/pull/2986