RFR: 8274245: sun/tools/jmap/BasicJMapTest.java Mutex rank failures [v2]

[David Holmes]

On Fri, 24 Sep 2021 01:38:21 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> This test fails due to Mutex rank assertions that I just added.  The new mutexes in the heapDumper needs to be ranked 'nosafepoint' and 'nosafepoint-1' since they don't cause safepoint checks.
>> This code also holds two no-safepoint checking locks and waits on the second.  This doesn't break rank ordering but does run afoul of an old assert that we had in the code, that is no longer has meaning.
>> 
>> The test still fails because of other bugs like JDK-8274196 but it doesn't get the mutex rank assertions anymore.
>> 
>> Testing with tier 5 and 6, where the failure was observed, in progress.
>
> Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Remove tests for special wait assert.

Hi Coleen,

These assertions have lost their context over time as the mutex susbsystem has been changed. This one used to check for rank "special and that (once upon a time) was defined as:

 // A special lock: Is a lock where you are guaranteed not to block while you are
 // holding it, i.e., no vm operation can happen, taking other locks, etc.

Hence the check that you don't wait() while holding one. But "special" is no more and the check makes no sense for general nosafepoint mutex/monitors.

So I think your changes are fine.

Thanks,
David

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Marked as reviewed by dholmes (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/5669