RFR: 8308745: ObjArrayKlass::allocate_objArray_klass may call into java while holding a lock [v2]

[Coleen Phillimore]

On Thu, 7 Mar 2024 01:44:22 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Dean's comments.
>
> src/hotspot/share/oops/instanceKlass.cpp line 1552:
> 
>> 1550:     RecursiveLocker rl(MultiArray_lock, THREAD);
>> 1551: 
>> 1552:     // This thread is the creator.
> 
> This thread may not be the creator. The original comment was more apt - we typically say something like "Check if another thread beat us to it."

Fixed.

    // Check if another thread created the array klass while we were waiting for the lock.

> src/hotspot/share/prims/jvmtiGetLoadedClasses.cpp line 121:
> 
>> 119:   {
>> 120:     // To get a consistent list of classes we need MultiArray_lock to ensure
>> 121:     // array classes aren't created during this walk. This walks through the
> 
> Just curious but how can walking the set of classes trigger creation of array classes?

It can't.  I'll reword that comment so it's clearer, with just a couple of words.

    // To get a consistent list of classes we need MultiArray_lock to ensure
    // array classes aren't created by another thread this walk. This walks through the
    // InstanceKlass::_array_klasses links.

edit: added "during" to "by another thread during this walk"

> src/hotspot/share/runtime/mutexLocker.hpp line 335:
> 
>> 333: 
>> 334: // Instance of a RecursiveLock that may be held through Java heap allocation, which may include calls to Java,
>> 335: // and JNI event notification for resource exhausted for metaspace or heap.
> 
> s/exhausted/exhaustion/

Fixed.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/17739#discussion_r1516126218
PR Review Comment: https://git.openjdk.org/jdk/pull/17739#discussion_r1516128248
PR Review Comment: https://git.openjdk.org/jdk/pull/17739#discussion_r1516130552