RFR: 8259008: ArithmeticException was thrown at "Monitor Cache Dump" on HSDB [v6]

[Daniel D.Daugherty]

On Wed, 27 Jan 2021 05:41:47 GMT, Yasumasa Suenaga <ysuenaga at openjdk.org> wrote:

>> Hi Yasumasa,
>> 
>> I thought the comments regarding the test were to use an if statement to check iter.hasNext() and return after seeing one Monitor, rather than keeping the while-loop and reporting every single Monitor found. The latter seems a waste of timer as we don't know how many Monitors to expect, so it adds no value to report them all.
>> 
>> Cheers,
>> David
>
>> I thought the comments regarding the test were to use an if statement to check iter.hasNext() and return after seeing one Monitor, rather than keeping the while-loop and reporting every single Monitor found. The latter seems a waste of timer as we don't know how many Monitors to expect, so it adds no value to report them all.
> 
> I thought we should test whether we can get ObjectMonitor via SA at first - in other words, the test would pass when we get 1 ObjectMonitor at least.
> However all of information of ObjectMonitors might be useful for diagnostic purposes as @dcubed-ojdk said. In this test, we use LingeredAppWithLock for debugee, so it will not waste time to iterate. (we might estimate num of locks we will observe: we can see 3 ObjectMonitors now)

The number should be small. I typically see 2 or 3 depending on the java
options. If I happen to see more, then that's a clue (to me anyway) that
something has changed and might be amiss.

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PR: https://git.openjdk.java.net/jdk/pull/1910