RFR: 8343840: Rewrite the ObjectMonitor lists [v2]

[Fredrik Bredberg]

On Wed, 26 Feb 2025 06:08:14 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> Fredrik Bredberg has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Update after review by David and Coleen.
>
> src/hotspot/share/runtime/objectMonitor.cpp line 232:
> 
>> 230: //   thread notices that the tail of the entry_list is not known, we
>> 231: //   convert the singly-linked entry_list into a doubly linked list by
>> 232: //   assigning the prev pointers and the entry_list_tail pointer.
> 
> Didn't we essentially say all this at the beginning?

This text makes more sense before the newly added "Example:", so I moved it.

> src/hotspot/share/runtime/objectMonitor.cpp line 260:
> 
>> 258: //
>> 259: // * notify() or notifyAll() simply transfers threads from the WaitSet
>> 260: //   to either the entry_list. Subsequent exit() operations will
> 
> Suggestion:
> 
> //   to the entry_list. Subsequent exit() operations will

Fixed

> src/hotspot/share/runtime/objectMonitor.cpp line 704:
> 
>> 702: 
>> 703:   for (;;) {
>> 704:     ObjectWaiter* front = Atomic::load(&_entry_list);
> 
> In comments and code pick "head" or "front" to use to describe what _entry_list points to and use that consistently. I think "front" is much more common.

A `grep -r `suggests that `head` is more common, so I changed to `head`.

> src/hotspot/share/runtime/objectMonitor.cpp line 705:
> 
>> 703:   for (;;) {
>> 704:     ObjectWaiter* front = Atomic::load(&_entry_list);
>> 705: 
> 
> No need for blank line.

Fixed

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

PR Review Comment: https://git.openjdk.org/jdk/pull/23421#discussion_r1974257620
PR Review Comment: https://git.openjdk.org/jdk/pull/23421#discussion_r1974259984
PR Review Comment: https://git.openjdk.org/jdk/pull/23421#discussion_r1974261995
PR Review Comment: https://git.openjdk.org/jdk/pull/23421#discussion_r1974260402