RFR: 8273300: Check Mutex ranking during a safepoint [v4]

[David Holmes]

On Tue, 14 Sep 2021 15:21:19 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> This change checks lock ranking during a safepoint.  For some reason, safepoint checking was excluded, probably from the days where Safepoint_lock and Threads_lock were used.
>> Because of checking during a safepoint, some locks had to get lower ranks.  The CR has the details of which locks these were.  The Service_lock complicates things because it's held during oops_do, which may take out other G1 locks.
>> This was built and tested with Shenandoah.  Thanks to @zhengyu123 for the changes in Shenandoah.
>> Tests run tier1-8.
>
> Coleen Phillimore has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains four commits:
> 
>  - Fix Shenandoah mismerge
>  - Merge branch 'master' into checkrank
>  - Fix Shenandoah mismerge
>  - 8273300: Check Mutex ranking during a safepoint

Hi Coleen,

It wasn't clear if you thought you had already fixed the incorrect copyright notices so I flagged the two I saw.

I still have some queries about this - see comment below - but nothing that would stop it from being pushed as-is.

Thanks,
David

src/hotspot/cpu/zero/vm_version_zero.cpp line 2:

> 1: /*
> 2:  * Copyright (c) 1997, 2021, Oracle and/or its affiliates. All rights reserved.

Unwanted copyright date change.

src/hotspot/share/runtime/mutex.hpp line 53:

> 51:        special        = tty            +   3,
> 52:        oopstorage     = special        +   3,
> 53:        leaf           = oopstorage     +  10,

Why do we need such a big gap here? Is there any reason we can't just use the same gap between all named rankings? As it is there seems to be no rationale for the  "+ N" value used.

src/hotspot/share/utilities/growableArray.hpp line 2:

> 1: /*
> 2:  * Copyright (c) 1997, 2021, Oracle and/or its affiliates. All rights reserved.

Unwanted copyright change.

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

Marked as reviewed by dholmes (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/5467