RFR: 8263896: Remove not_suspended parameter from ObjectMonitor::exit() [v3]

[David Holmes]

On Fri, 26 Mar 2021 20:34:43 GMT, Patricio Chilano Mateo <pchilanomate at openjdk.org> wrote:

>> Hi,
>> 
>> Please review the following small patch. The boolean parameter not_suspended is used to detect if we need to set the current JavaThread exiting the monitor as the previous owner (_previous_owner_tid). If not_suspended is true then we set _previous_owner_tid, otherwise we skip the write (modulo the JFR checks). This parameter is always true except when we call exit() from inside enter(). This happens when the JavaThread acquires the monitor but notices that it was suspended while being in the _thread_blocked state. Since in that case the JT was never really "the owner" we skip setting _previous_owner_tid.
>> 
>> This behaviour of releasing the monitor is just an implementation detail of ObjectMonitor::enter() which doesn't need to be exposed in the exit() API. We can identify the same scenario just by checking _current_pending_monitor instead.
>> 
>> Thanks,
>> Patricio
>
> Patricio Chilano Mateo has updated the pull request incrementally with one additional commit since the last revision:
> 
>   restore not_suspended with default argument

This looks good to me - thanks.

Please update the bug and the PR title to reflect that the parameter was not removed.

Thanks,
David

src/hotspot/share/runtime/objectMonitor.cpp line 391:

> 389:     JavaThreadBlockedOnMonitorEnterState jtbmes(current, this);
> 390: 
> 391:     assert(current->current_pending_monitor() == NULL, "invariant");

Really this belongs inside set_current_pending_monitor() where the only allowed transitions are null to non-null, and non-null to null. But that would be a separate RFE.

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Marked as reviewed by dholmes (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/3101