RFR: 8371643: Remove ThreadLocalAllocBuffer::_reserve_for_allocation_prefetch [v2]

[Martin Doerr]

On Thu, 13 Nov 2025 11:35:04 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

>> We have seen crashes on many platforms (including x64) while running `make run-test TEST=runtime/cds/appcds/aotClassLinking/LambdaInExcludedClass.java JTREG="VM_OPTIONS=-XX:+UseCompactObjectHeaders"`:
>> 
>> SIGSEGV (0xb) at pc=0x00007f2f95a61e7a, pid=18554, tid=18557
>> V  [libjvm.so+0x15bfe7a]  MemAllocator::finish(HeapWordImpl**) const+0xca  (klass.inline.hpp:72)
>> V  [libjvm.so+0x15c029f]  ObjAllocator::initialize(HeapWordImpl**) const+0x2f  (memAllocator.cpp:391)
>> V  [libjvm.so+0xb0630b]  CollectedHeap::fill_with_object(HeapWordImpl**, unsigned long, bool)+0x27b  (collectedHeap.cpp:491)
>> V  [libjvm.so+0x1c7a0bb]  ThreadLocalAllocBuffer::retire(ThreadLocalAllocStats*)+0x11b  (threadLocalAllocBuffer.cpp:118)
>> V  [libjvm.so+0x15c0b14]  MemAllocator::mem_allocate_inside_tlab_slow(MemAllocator::Allocation&) const+0x84  (memAllocator.cpp:286)
>> V  [libjvm.so+0x15c13ab]  MemAllocator::mem_allocate(MemAllocator::Allocation&) const+0xbb  (memAllocator.cpp:340)
>> V  [libjvm.so+0x15c14f9]  MemAllocator::allocate() const+0xa9  (memAllocator.cpp:353)
>> V  [libjvm.so+0x1cc052e]  TypeArrayKlass::allocate_common(int, bool, JavaThread*)+0x13e  (collectedHeap.inline.hpp:41)
>> V  [libjvm.so+0x16fbc98]  oopFactory::new_typeArray(BasicType, int, JavaThread*)+0x38  (typeArrayKlass.hpp:51)
>> V  [libjvm.so+0x106b0f3]  java_lang_Class::restore_archived_mirror(Klass*, Handle, Handle, Handle, JavaThread*)+0x413  (javaClasses.cpp:1246)
>> V  [libjvm.so+0x14100bc]  Klass::restore_unshareable_info(ClassLoaderData*, Handle, JavaThread*)+0x66c  (klass.cpp:903)
>> V  [libjvm.so+0xfe2cb1]  InstanceKlass::restore_unshareable_info(ClassLoaderData*, Handle, PackageEntry*, JavaThread*)+0x81  (instanceKlass.cpp:2823)
>> V  [libjvm.so+0x1c0f5ad]  SystemDictionary::preload_class(Handle, InstanceKlass*, JavaThread*)+0x1ed  (systemDictionary.cpp:1198)
>> V  [libjvm.so+0x676e83]  AOTLinkedClassBulkLoader::preload_classes_in_table(Array<InstanceKlass*>*, char const*, Handle, JavaThread*)+0x1a3  (aotLinkedClassBulkLoader.cpp:103)
>> V  [libjvm.so+0x679af5]  AOTLinkedClassBulkLoader::preload_classes_impl(JavaThread*)+0x165  (aotLinkedClassBulkLoader.cpp:76)
>> V  [libjvm.so+0x67c371]  AOTLinkedClassBulkLoader::preload_classes(JavaThread*)+0x11  (aotLinkedClassBulkLoader.cpp:61)
>> V  [libjvm.so+0x1d5bf30]  vmClasses::resolve_all(JavaThread*)+0x3e0  (vmClasses.cpp:126)
>> V  [libjvm.so+0x1c0f28c]  SystemDictionary::initialize(JavaThread*)+0x10c  (systemDictionary.cpp:1623)
>> V  [libjvm.so+0x1cc74ca]  Uni...
>
>> ... make run-test TEST=runtime/cds/appcds/aotClassLinking/LambdaInExcludedClass.java JTREG="VM_OPTIONS=-XX:+UseCompactObjectHeaders"
> 
> I suspect the crash is caused by a preexisting issue that is exposed by this patch.
> 
> In `vmClasses::resolve_all`:
> 
> #if INCLUDE_CDS
>   if (CDSConfig::is_using_aot_linked_classes()) {
>     AOTLinkedClassBulkLoader::preload_classes(THREAD);
>   }
> #endif
> 
>   // Preload commonly used klasses
>   vmClassID scan = vmClassID::FIRST;
>   // first do Object, then String, Class
>   resolve_through(VM_CLASS_ID(Object_klass), scan, CHECK);
>   CollectedHeap::set_filler_object_klass(vmClasses::Object_klass());
> 
> 
> The filler-klass is not initialized when `preload_classes` is invoked, but `preload_classes` use heap-allocation, which may require filler-obj.
> 
> @iklam What do you think?

> @albertnetymk I've pushed #28315. Please verify if it fixes the crash before integrating this PR. Thanks!

The crashes are fixed. Thanks!

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

PR Comment: https://git.openjdk.org/jdk/pull/28240#issuecomment-3538748578