On Sat, 10 Feb 2024 04:06:37 GMT, Serguei Spitsyn <sspit...@openjdk.org> wrote:
>> The implementation of the JVM TI `GetObjectMonitorUsage` does not match the
>> spec.
>> The function returns the following structure:
>>
>>
>> typedef struct {
>> jthread owner;
>> jint entry_count;
>> jint waiter_count;
>> jthread* waiters;
>> jint notify_waiter_count;
>> jthread* notify_waiters;
>> } jvmtiMonitorUsage;
>>
>>
>> The following four fields are defined this way:
>>
>> waiter_count [jint] The number of threads waiting to own this monitor
>> waiters [jthread*] The waiter_count waiting threads
>> notify_waiter_count [jint] The number of threads waiting to be notified by
>> this monitor
>> notify_waiters [jthread*] The notify_waiter_count threads waiting to be
>> notified
>>
>> The `waiters` has to include all threads waiting to enter the monitor or to
>> re-enter it in `Object.wait()`.
>> The implementation also includes the threads waiting to be notified in
>> `Object.wait()` which is wrong.
>> The `notify_waiters` has to include all threads waiting to be notified in
>> `Object.wait()`.
>> The implementation also includes the threads waiting to re-enter the monitor
>> in `Object.wait()` which is wrong.
>> This update makes it right.
>>
>> The implementation of the JDWP command `ObjectReference.MonitorInfo (5)` is
>> based on the JVM TI `GetObjectMonitorInfo()`. This update has a tweak to
>> keep the existing behavior of this command.
>>
>> The follwoing JVMTI vmTestbase tests are fixed to adopt to the
>> `GetObjectMonitorUsage()` correct behavior:
>>
>> jvmti/GetObjectMonitorUsage/objmonusage001
>> jvmti/GetObjectMonitorUsage/objmonusage003
>>
>>
>> The following JVMTI JCK tests have to be fixed to adopt to correct behavior:
>>
>> vm/jvmti/GetObjectMonitorUsage/gomu001/gomu00101/gomu00101.html
>> vm/jvmti/GetObjectMonitorUsage/gomu001/gomu00101/gomu00101a.html
>> vm/jvmti/GetObjectMonitorUsage/gomu001/gomu00102/gomu00102.html
>> vm/jvmti/GetObjectMonitorUsage/gomu001/gomu00102/gomu00102a.html
>>
>>
>>
>> A JCK bug will be filed and the tests have to be added into the JCK problem
>> list located in the closed repository.
>>
>> Also, please see and review the related CSR:
>> [8324677](https://bugs.openjdk.org/browse/JDK-8324677): incorrect
>> implementation of JVM TI GetObjectMonitorUsage
>>
>> The Release-Note is:
>> [8325314](https://bugs.openjdk.org/browse/JDK-8325314): Release Note:
>> incorrect implementation of JVM TI GetObjectMonitorUsage
>>
>> Testing:
>> - tested with mach5 tiers 1-6
>
> Serguei Spitsyn has updated the pull request incrementally with one
> additional commit since the last revision:
>
> review: fixed issues in get_object_monitor_usage; extended test coverage in
> objmonusage003
I've pushed an update addressing review comments from Dan/David.
This is a short list describing the updates:
- now the function `Threads::get_pending_threads()` in the `threads.cpp` is
supporting the monitor re-enter case
- introduced the function `oop JavaThread::vthread_or_thread()` used in the
function `Threads::get_pending_threads()`
- the fix in `jvmtiEnvBase.cpp` has been re-arranged to calculate early the
right sizes of the `waiters` and `notify_waiters` array
- the NSK test
`test/hotspot/jtreg/vmTestbase/nsk/jvmti/GetObjectMonitorUsage/objmonusage003`
was extended to provide coverage suggested by David. It recreates a scenario
with several threads blocked on the monitor enter, several threads blocked on
re-enter and several thread waiting in the `Object.wait()` to be notified.
- some small test fixes suggested in review
The mach5 tiers 1-6 are all passed except the four known to fail JCK tests in
the tier 6.
-------------
PR Comment: https://git.openjdk.org/jdk/pull/17680#issuecomment-1936927038
