On Tue, 22 Jun 2021 04:09:48 GMT, Thomas Stuefe <stu...@openjdk.org> wrote:
>> I changed the _contentions and _waiters fields from jint to int and ran
>> tests tier1-3. Tested tier1 with linux, mac, windows platforms. Also
>> changed the _previous_owner_tid to unintptr_t from jlong, since that's what
>> the cast did.
>
> src/hotspot/share/runtime/objectMonitor.hpp line 244:
>
>> 242: int cnts = contentions(); // read once
>> 243: if (cnts > 0) {
>> 244: ret_code |= intptr_t(cnts);
>
> I know it has nothing to do with your patch, but I am just curious. IIUC this
> is a strange way of saying "if A!=0 || B!=0 || C!=0..." . Is this for
> performance reasons? Also, why the "if (cnts > 0)", would that not be
> superfluous?
I think this code exists like this from when is_busy returned an uintptr_t. It
should be nicely rewritten with if != 0s now and likely would have better
performance. I won't do it with this change because these fields are volatile
and I think should have Atomic::loads, which would lead to a lot of discussion
that should happen independently. I'll file an RFE.
-------------
PR: https://git.openjdk.java.net/jdk/pull/3980
