Assert failure: m_alignpad == 0 in libraries tests

[jkotas]

Hit in #70226

Dump and logs: https://dev.azure.com/dnceng/public/_build/results?buildId=1806089&view=ms.vss-test-web.build-test-results-tab&runId=48090090&resultId=197319&paneView=dotnet-dnceng.dnceng-build-release-tasks.helix-test-information-tab

Stacktrace:

coreclr!DbgAssertDialog+0x1af [D:\a\_work\1\s\src\coreclr\utilcode\debug.cpp @ 594] 
coreclr!ObjHeader::IllegalAlignPad+0x33 [D:\a\_work\1\s\src\coreclr\vm\syncblk.cpp @ 2952] 
coreclr!ObjHeader::GetBits+0x41 [D:\a\_work\1\s\src\coreclr\vm\syncblk.h @ 1545] 
coreclr!ObjHeader::Validate+0x50 [D:\a\_work\1\s\src\coreclr\vm\syncblk.cpp @ 2042] 
coreclr!Object::ValidateInner+0x493 [D:\a\_work\1\s\src\coreclr\vm\object.cpp @ 581] 
coreclr!Object::Validate+0xa1 [D:\a\_work\1\s\src\coreclr\vm\object.cpp @ 498] 
coreclr!OBJECTREF::operator->+0x21 [D:\a\_work\1\s\src\coreclr\vm\object.cpp @ 1242] 
coreclr!MarshalNative::GCHandleInternalAlloc+0x171 [D:\a\_work\1\s\src\coreclr\vm\marshalnative.cpp @ 492] 
System_Private_CoreLib!System.ReadOnlyMemory`1[[System.Byte, System.Private.CoreLib]].Pin()+0xffffffff`a4114a41

[jkotas]

This is failing in the next-object validation.

m_alignpad is 0 in the dump. It means that it got cleared between the assert condition was checked and the crash dump was taken.

The most likely explanation is that there is a race condition between GCHeap::NextObj and the memory clearing for newly allocated objects in the GC that causes GCHeap::NextObj to return next object that was not cleared yet. @dotnet/gc Could you please take a look?

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Issue Details

---

Hit in #70226

Dump and logs: https://dev.azure.com/dnceng/public/_build/results?buildId=1806089&view=ms.vss-test-web.build-test-results-tab&runId=48090090&resultId=197319&paneView=dotnet-dnceng.dnceng-build-release-tasks.helix-test-information-tab

Stacktrace:

coreclr!DbgAssertDialog+0x1af [D:\a\_work\1\s\src\coreclr\utilcode\debug.cpp @ 594] 
coreclr!ObjHeader::IllegalAlignPad+0x33 [D:\a\_work\1\s\src\coreclr\vm\syncblk.cpp @ 2952] 
coreclr!ObjHeader::GetBits+0x41 [D:\a\_work\1\s\src\coreclr\vm\syncblk.h @ 1545] 
coreclr!ObjHeader::Validate+0x50 [D:\a\_work\1\s\src\coreclr\vm\syncblk.cpp @ 2042] 
coreclr!Object::ValidateInner+0x493 [D:\a\_work\1\s\src\coreclr\vm\object.cpp @ 581] 
coreclr!Object::Validate+0xa1 [D:\a\_work\1\s\src\coreclr\vm\object.cpp @ 498] 
coreclr!OBJECTREF::operator->+0x21 [D:\a\_work\1\s\src\coreclr\vm\object.cpp @ 1242] 
coreclr!MarshalNative::GCHandleInternalAlloc+0x171 [D:\a\_work\1\s\src\coreclr\vm\marshalnative.cpp @ 492] 
System_Private_CoreLib!System.ReadOnlyMemory`1[[System.Byte, System.Private.CoreLib]].Pin()+0xffffffff`a4114a41

Author:	jkotas
Assignees:	-
Labels:	area-GC-coreclr, area-Interop-coreclr, untriaged
Milestone:	-

[BruceForstall]

Same assert here: #68511

[BruceForstall]

The same assert happened for jitminopts in System.Text.RegularExpressions.Unit.Tests on win-x64:

https://dev.azure.com/dnceng/public/_build/results?buildId=1807559&view=ms.vss-test-web.build-test-results-tab&runId=48105794&resultId=197597&paneView=dotnet-dnceng.dnceng-build-release-tasks.helix-test-information-tab

[mdh1418]

Same assert failed on System.Buffers.Tests https://dev.azure.com/dnceng/public/_build/results?buildId=1809197&view=ms.vss-test-web.build-test-results-tab&runId=48130508&resultId=197594&paneView=debug in this unrelated PR #70194