The ProjectLockService.dgml file tells me I have several clients waiting
on a lock, and one client holding an upgradeable read lock.
I know the lock is involved in the hang because the async state machine responsible for blocking the main thread is blocked because it can't get a read lock.
Who is holding the upgradeable read lock? WinDBG can help us find the answer.
0:000> !dumpheap -stat -type ProjectLockService
Statistics:
MT Count TotalSize Class Name
62d3963c 1 12
System.Lazy`1+Boxed[[Microsoft.VisualStudio.ProjectSystem.IProjectLockServiceInternal,
Microsoft.VisualStudio.ProjectSystem.V14Only]]
62bf05c8 1 12 System.Lazy`1+Boxed[[Microsoft.VisualStudio.ProjectSystem.ProjectLockService,
Microsoft.VisualStudio.ProjectSystem.Implementation]]
62d370d8 1 20 System.Lazy`1[[Microsoft.VisualStudio.ProjectSystem.IProjectLockServiceInternal,
Microsoft.VisualStudio.ProjectSystem.V14Only]]
62be0268 1 20 System.Lazy`1[[Microsoft.VisualStudio.ProjectSystem.ProjectLockService,
Microsoft.VisualStudio.ProjectSystem.Implementation]]
62d379cc 1 32 System.Func`1[[Microsoft.VisualStudio.ProjectSystem.IProjectLockService,
Microsoft.VisualStudio.ProjectSystem.V14Only]]
62d3712c 1 32 System.Func`1[[Microsoft.VisualStudio.ProjectSystem.IProjectLockServiceInternal,
Microsoft.VisualStudio.ProjectSystem.V14Only]]
62be845c 1 32 System.Func`1[[Microsoft.VisualStudio.ProjectSystem.ProjectLockService,
Microsoft.VisualStudio.ProjectSystem.Implementation]]
62a05eac 1 32 Microsoft.VisualStudio.ProjectSystem.ProjectLockService+AccessLockEnforcement
62d395bc 5 60 System.Lazy`1+Boxed[[Microsoft.VisualStudio.ProjectSystem.IProjectLockService,
Microsoft.VisualStudio.ProjectSystem.V14Only]]
62d37978 5 100 System.Lazy`1[[Microsoft.VisualStudio.ProjectSystem.IProjectLockService,
Microsoft.VisualStudio.ProjectSystem.V14Only]]
62a060c4 5 100 Microsoft.VisualStudio.ProjectSystem.ProjectLockService+<>c__DisplayClass4
62a04af0 1 116 Microsoft.VisualStudio.ProjectSystem.ProjectLockService
62a0611c 5 220
Microsoft.VisualStudio.ProjectSystem.ProjectLockService+<>c__DisplayClass4+<<Microsoft_VisualStudio_ProjectSystem_IProjectLockReleaser_OnCompleted>b__6>d__0
Total 29 objects
Fragmented blocks larger than 0.5 MB:
Addr Size Followed by
18aaa760 0.8MB 18b80bf0 System.Byte[]
18b80c48 0.6MB 18c1692c System.Byte[]
18c1aacc 0.8MB 18cea584 System.Byte[]
18cec5a0 0.9MB 18dd7084 System.Byte[]
18dd9090 1.2MB 18f04ea4 System.Byte[]
18f434bc 3.6MB 192d5ff4 System.Byte[]
0:000> !dumpheap -mt 62a04af0
Address MT Size
0bf21e20 62a04af0 116
Statistics:
MT Count TotalSize Class Name
62a04af0 1 116 Microsoft.VisualStudio.ProjectSystem.ProjectLockService
Total 1 objects
Fragmented blocks larger than 0.5 MB:
Addr Size Followed by
18aaa760 0.8MB 18b80bf0 System.Byte[]
18b80c48 0.6MB 18c1692c System.Byte[]
18c1aacc 0.8MB 18cea584 System.Byte[]
18cec5a0 0.9MB 18dd7084 System.Byte[]
18dd9090 1.2MB 18f04ea4 System.Byte[]
18f434bc 3.6MB 192d5ff4 System.Byte[]
0:000> !do 0bf21e20
Name: Microsoft.VisualStudio.ProjectSystem.ProjectLockService
MethodTable: 62a04af0
EEClass: 628c47e8
Size: 116(0x74) bytes
File: C:\Windows\Microsoft.Net\assembly\GAC_MSIL\Microsoft.VisualStudio.ProjectSystem.Implementation\v4.0_14.0.0.0__b03f5f7f11d50a3a\Microsoft.VisualStudio.ProjectSystem.Implementation.dll
Fields:
MT Field Offset Type VT Attr Value Name
7188e0c8 400001e 4 System.Object 0 instance 0bf22720
syncObject
6d51d05c 400001f 8 ...ronizationContext 0 instance 0bf2272c
nonConcurrentSyncContext
6d51d0cc 4000020 c ...tudio.Threading]] 0 instance 0bf22770
topAwaiter
6d4d288c 4000021 10 ...tudio.Threading]] 0 instance 0bf2283c
issuedReadLocks
6d4d288c 4000022 14 ...tudio.Threading]] 0 instance 0bf228a8
issuedUpgradeableReadLocks
6d4d288c 4000023 18 ...tudio.Threading]] 0 instance 0bf228d0
issuedWriteLocks
6d4d2928 4000024 1c ...tudio.Threading]] 0 instance 0bf228f8
waitingReaders
6d4d2928 4000025 20 ...tudio.Threading]] 0 instance 0bf22928
waitingUpgradeableReaders
6d4d2928 4000026 24 ...tudio.Threading]] 0 instance 0bf22948
waitingWriters
…
0:000> !do 0bf228a8
Name: System.Collections.Generic.HashSet`1[[Microsoft.VisualStudio.Threading.AsyncReaderWriterLock+Awaiter,
Microsoft.VisualStudio.Threading]]
MethodTable: 6d4d288c
EEClass: 70497e24
Size: 40(0x28) bytes
File: C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Core\v4.0_4.0.0.0__b77a5c561934e089\System.Core.dll
Fields:
MT Field Offset Type VT Attr Value Name
7188fb80 40006f6 4 System.Int32[] 0 instance 0c55b410
m_buckets
7094cb3c 40006f7 8 ...non, mscorlib]][] 0 instance 0c55b3b0
m_slots
7188fbb8 40006f8 14 System.Int32 1 instance 1
m_count
7188fbb8 40006f9 18 System.Int32 1 instance 1
m_lastIndex
7188fbb8 40006fa 1c System.Int32 1 instance -1
m_freeList
718c7cb0 40006fb c ...Canon, mscorlib]] 0 instance 0bf2289c
m_comparer
7188fbb8 40006fc 20 System.Int32 1 instance 1455
m_version
71893580 40006fd 10 ...SerializationInfo 0 instance 00000000
m_siInfo
0:000> !DumpArray /d 0c55b3b0
Name: System.Collections.Generic.HashSet`1+Slot[[Microsoft.VisualStudio.Threading.AsyncReaderWriterLock+Awaiter,
Microsoft.VisualStudio.Threading]][]
MethodTable: 6d51e134
EEClass: 6d4e26f8
Size: 96(0x60) bytes
Array: Rank 1, Number of elements 7, Type VALUETYPE
Element Methodtable: 6d51e0f4
[0] 0c55b3b8
[1] 0c55b3c4
[2] 0c55b3d0
[3] 0c55b3dc
[4] 0c55b3e8
[5] 0c55b3f4
[6] 0c55b400
I then enumerate the array looking for valid dictionary entries. Because each entry is a value-type, I have to use the appropriate syntax:
0:000> !dumpvc 6d51e0f4 0c55b3b8
Name: System.Collections.Generic.HashSet`1+Slot[[Microsoft.VisualStudio.Threading.AsyncReaderWriterLock+Awaiter,
Microsoft.VisualStudio.Threading]]
MethodTable: 6d51e0f4
EEClass: 70499ff4
Size: 20(0x14) bytes
File: C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Core\v4.0_4.0.0.0__b77a5c561934e089\System.Core.dll
Fields:
MT Field Offset Type VT Attr Value Name
7188fbb8 4000707 4 System.Int32 1 instance 40482544
hashCode
71891178 4000708 0 System.__Canon 0 instance 11b8cfb0 value
7188fbb8 4000709 8 System.Int32 1 instance -1 next
0:000> !do 11b8cfb0
Name: Microsoft.VisualStudio.Threading.AsyncReaderWriterLock+Awaiter
MethodTable: 6d51d124
EEClass: 6d4e22ec
Size: 60(0x3c) bytes
File: C:\Windows\Microsoft.Net\assembly\GAC_MSIL\Microsoft.VisualStudio.Threading\v4.0_14.0.0.0__b03f5f7f11d50a3a\Microsoft.VisualStudio.Threading.dll
Fields:
MT Field Offset Type VT Attr Value Name
6d51cc58 40000ab 4 ...cReaderWriterLock 0 instance 0bf21e20 lck
6d51dfc8 40000ac 20 System.Int32 1 instance 1 kind
6d51d124 40000ad 8 ...riterLock+Awaiter 0 instance 00000000
nestingLock
7189a0c8 40000ae 28 ...CancellationToken 1 instance 11b8cfd8
cancellationToken
718d0a5c 40000af 2c ...TokenRegistration 1 instance 11b8cfdc
cancellationRegistration
6d51e000 40000b0 24 System.Int32 1 instance 0
options
7188de70 40000b1 c System.Exception 0 instance 00000000 fault
7189a934 40000b2 10 System.Action 0 instance 00000000
continuation
718998d0 40000b3 14 ...eading.Tasks.Task 0 instance 00000000
releaseAsyncTask
71898968 40000b4 18 ...ostics.StackTrace 0 instance 00000000
requestingStackTrace
7188e0c8 40000b5 1c System.Object 0 instance 00000000 data
718c826c 40000aa b0 ...bject, mscorlib]] 0 shared static
cancellationResponseAction
>> Domain:Value 013e8c60:0bf3374c <<
71897aa8 40000b6 b4 ...endOrPostCallback 0 shared static
CS$<>9__CachedAnonymousMethodDelegate1
>> Domain:Value 013e8c60:0bf3376c <<
So I've found my awaiter that represents the lock. I need to find out who is holding it.
0:000> !gcroot 11b8cfb0
Thread 1594:
0113e140 6d5068dc Microsoft.VisualStudio.Threading.JoinableTaskFactory.WaitSynchronouslyCore(System.Threading.Tasks.Task)
[f:\dd\vsproject\cps\Microsoft.VisualStudio.Threading\Microsoft.VisualStudio.Threading\JoinableTaskFactory.cs
@ 274]
ebp+50: 0113e140
-> 0bf352c4 Microsoft.VisualStudio.ProjectSystem.Utilities.ProjectLockAwareJoinableTaskFactory
-> 0377c514 Microsoft.VisualStudio.Threading.JoinableTaskContext
-> 0377c648 System.Collections.Generic.HashSet`1[[Microsoft.VisualStudio.Threading.JoinableTask,
Microsoft.VisualStudio.Threading]]
-> 0c2738cc System.Collections.Generic.HashSet`1+Slot[[Microsoft.VisualStudio.Threading.JoinableTask,
Microsoft.VisualStudio.Threading]][]
-> 0ce64e78 Microsoft.VisualStudio.Threading.JoinableTask
-> 0c6b1f68 Microsoft.VisualStudio.ProjectSystem.Utilities.ProjectLockAwareJoinableTaskFactory
-> 0bf21e20 Microsoft.VisualStudio.ProjectSystem.ProjectLockService
-> 0bf2272c Microsoft.VisualStudio.Threading.AsyncReaderWriterLock+NonConcurrentSynchronizationContext
-> 0c5a96d8 System.Threading.Thread
-> 03772fb4 System.Runtime.Remoting.Contexts.Context
-> 037712e4 System.AppDomain
-> 1198eca0 System.AssemblyLoadEventHandler
-> 1198ec80 System.Object[]
-> 0ccaeee0 System.AssemblyLoadEventHandler
-> 0ccaed08 Microsoft.VisualStudio.Design.Toolbox.AutoToolboxManagerService
...
-> 0ce91bf8 Microsoft.VisualStudio.ProjectSystem.Designers.ProjectDirectoryTreeProvider
-> 11bdebfc Microsoft.VisualStudio.ProjectSystem.Designers.ProjectDirectoryTreeProvider+MyConfiguredProjectExports
-> 1142f3b4 Microsoft.VisualStudio.ProjectSystem.PropertyPages.PropertyPagesDataModelProvider
-> 1142f3f8
Microsoft.VisualStudio.ProjectSystem.Utilities.OrderPrecedenceImportCollection`2[[Microsoft.VisualStudio.ProjectSystem.Designers.Properties.IDynamicEnumValuesProvider,
Microsoft.VisualStudio.ProjectSystem.V14Only],[Microsoft.VisualStudio.ProjectSystem.PropertyPages.IDynamicEnumCategoryMetadata,
Microsoft.VisualStudio.ProjectSystem.Implementation]]
-> 1142f428
System.Collections.Generic.List`1[[System.Lazy`2[[Microsoft.VisualStudio.ProjectSystem.Designers.Properties.IDynamicEnumValuesProvider,
Microsoft.VisualStudio.ProjectSystem.V14Only],[Microsoft.VisualStudio.ProjectSystem.PropertyPages.IDynamicEnumCategoryMetadata,
Microsoft.VisualStudio.ProjectSystem.Implementation]],
System.ComponentModel.Composition]]
-> 11430410 System.Object[]
-> 1142fc90 System.Lazy`2[[Microsoft.VisualStudio.ProjectSystem.Designers.Properties.IDynamicEnumValuesProvider,
Microsoft.VisualStudio.ProjectSystem.V14Only],[Microsoft.VisualStudio.ProjectSystem.PropertyPages.IDynamicEnumCategoryMetadata,
Microsoft.VisualStudio.ProjectSystem.Implementation]]
-> 1142fcb4 System.Func`1[[Microsoft.VisualStudio.ProjectSystem.Designers.Properties.IDynamicEnumValuesProvider,
Microsoft.VisualStudio.ProjectSystem.V14Only]]
-> 1142fca8
Microsoft.VisualStudio.Composition.DelegateServices+<>c__DisplayClass0`1[[Microsoft.VisualStudio.ProjectSystem.Designers.Properties.IDynamicEnumValuesProvider,
Microsoft.VisualStudio.ProjectSystem.V14Only]]
-> 1142fc60 System.Func`1[[System.Object, mscorlib]]
-> 1142fc48 Microsoft.VisualStudio.Composition.RuntimeExportProviderFactory+RuntimeExportProvider+<>c__DisplayClass13
-> 11428a68
Microsoft.VisualStudio.Composition.RuntimeExportProviderFactory+RuntimeExportProvider+RuntimePartLifecycleTracker
-> 11428aa8
System.Collections.Generic.HashSet`1[[Microsoft.VisualStudio.Composition.ExportProvider+PartLifecycleTracker,
Microsoft.VisualStudio.Composition]]
-> 1142fa10
System.Collections.Generic.HashSet`1+Slot[[Microsoft.VisualStudio.Composition.ExportProvider+PartLifecycleTracker,
Microsoft.VisualStudio.Composition]][]
-> 1142bc18
Microsoft.VisualStudio.Composition.RuntimeExportProviderFactory+RuntimeExportProvider+RuntimePartLifecycleTracker
-> 1142bc80 Microsoft.VisualStudio.ProjectSystem.Items.ProjectItemSchemaManager
-> 11bc6f20
System.ComponentModel.Composition.ExportLifetimeContext`1[[System.Threading.Tasks.Dataflow.BroadcastBlock`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectVersionedValue`1[[Microsoft.VisualStudio.ProjectSystem.Items.IProjectItemSchema,
Microsoft.VisualStudio.ProjectSystem.V14Only]], Microsoft.VisualStudio.ProjectSystem.V14Only]],
System.Threading.Tasks.Dataflow]]
-> 11bc6f00 System.Action
-> 11bc6100
Microsoft.VisualStudio.ProjectSystem.Utilities.DataflowExtensions+<>c__DisplayClass12`2[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectVersionedValue`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only]],
Microsoft.VisualStudio.ProjectSystem.V14Only],[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectVersionedValue`1[[Microsoft.VisualStudio.ProjectSystem.Items.IProjectItemSchema,
Microsoft.VisualStudio.ProjectSystem.V14Only]], Microsoft.VisualStudio.ProjectSystem.V14Only]]
-> 11bc6ee8 System.Threading.Tasks.Dataflow.Internal.Disposables+Disposable`3[[System.Object,
mscorlib],[System.Threading.Tasks.Dataflow.Internal.TargetRegistry`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectVersionedValue`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only]], Microsoft.VisualStudio.ProjectSystem.V14Only]],
System.Threading.Tasks.Dataflow],[System.Threading.Tasks.Dataflow.ITargetBlock`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectVersionedValue`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only]], Microsoft.VisualStudio.ProjectSystem.V14Only]],
System.Threading.Tasks.Dataflow]]
-> 11bc5058 System.Threading.Tasks.TaskCompletionSource`1[[System.Threading.Tasks.Dataflow.Internal.VoidResult,
System.Threading.Tasks.Dataflow]]
-> 11bc5064 System.Threading.Tasks.Task`1[[System.Threading.Tasks.Dataflow.Internal.VoidResult,
System.Threading.Tasks.Dataflow]]
-> 11bc51dc System.Threading.Tasks.StandardTaskContinuation
-> 11bc50dc System.Threading.Tasks.ContinuationTaskFromTask
-> 11bc4fe4
System.Threading.Tasks.Dataflow.BroadcastBlock`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectVersionedValue`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only]], Microsoft.VisualStudio.ProjectSystem.V14Only]]
-> 11bc4ff8
System.Threading.Tasks.Dataflow.BroadcastBlock`1+BroadcastingSourceCore`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectVersionedValue`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only]],
Microsoft.VisualStudio.ProjectSystem.V14Only],[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectVersionedValue`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only]], Microsoft.VisualStudio.ProjectSystem.V14Only]]
-> 11bc5090
System.Threading.Tasks.Dataflow.Internal.TargetRegistry`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectVersionedValue`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only]], Microsoft.VisualStudio.ProjectSystem.V14Only]]
-> 11bc50ac
System.Collections.Generic.Dictionary`2[[System.Threading.Tasks.Dataflow.ITargetBlock`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectVersionedValue`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only]], Microsoft.VisualStudio.ProjectSystem.V14Only]],
System.Threading.Tasks.Dataflow],[System.Threading.Tasks.Dataflow.Internal.TargetRegistry`1+LinkedTargetInfo[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectVersionedValue`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only]], Microsoft.VisualStudio.ProjectSystem.V14Only]],
System.Threading.Tasks.Dataflow]]
-> 11bdadd4
System.Collections.Generic.Dictionary`2+Entry[[System.Threading.Tasks.Dataflow.ITargetBlock`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectVersionedValue`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only]], Microsoft.VisualStudio.ProjectSystem.V14Only]],
System.Threading.Tasks.Dataflow],[System.Threading.Tasks.Dataflow.Internal.TargetRegistry`1+LinkedTargetInfo[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectVersionedValue`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only]], Microsoft.VisualStudio.ProjectSystem.V14Only]],
System.Threading.Tasks.Dataflow]][]
-> 11bc5290
System.Threading.Tasks.Dataflow.TransformBlock`2[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectVersionedValue`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only]],
Microsoft.VisualStudio.ProjectSystem.V14Only],[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only]]
-> 11bc56c8
System.Threading.Tasks.Dataflow.Internal.TargetCore`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectVersionedValue`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only]], Microsoft.VisualStudio.ProjectSystem.V14Only]]
-> 11bc5800 System.Threading.Tasks.TaskCompletionSource`1[[System.Threading.Tasks.Dataflow.Internal.VoidResult,
System.Threading.Tasks.Dataflow]]
-> 11bc580c System.Threading.Tasks.Task`1[[System.Threading.Tasks.Dataflow.Internal.VoidResult,
System.Threading.Tasks.Dataflow]]
-> 11bc5c68 System.Threading.Tasks.StandardTaskContinuation
-> 11bc5b68 System.Threading.Tasks.ContinuationTaskFromTask
-> 11bc52b8
System.Threading.Tasks.Dataflow.Internal.SourceCore`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only]]
-> 11bc565c
System.Threading.Tasks.Dataflow.Internal.TargetRegistry`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only]]
-> 11bc5678
System.Collections.Generic.Dictionary`2[[System.Threading.Tasks.Dataflow.ITargetBlock`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only]],
System.Threading.Tasks.Dataflow],[System.Threading.Tasks.Dataflow.Internal.TargetRegistry`1+LinkedTargetInfo[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only]], System.Threading.Tasks.Dataflow]]
-> 11bc5fec
System.Collections.Generic.Dictionary`2+Entry[[System.Threading.Tasks.Dataflow.ITargetBlock`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only]],
System.Threading.Tasks.Dataflow],[System.Threading.Tasks.Dataflow.Internal.TargetRegistry`1+LinkedTargetInfo[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only]], System.Threading.Tasks.Dataflow]][]
-> 11bc5dac
System.Threading.Tasks.Dataflow.BroadcastBlock`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only]]
-> 11bc5dc0
System.Threading.Tasks.Dataflow.BroadcastBlock`1+BroadcastingSourceCore`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only],[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only]]
-> 11bc5e58
System.Threading.Tasks.Dataflow.Internal.TargetRegistry`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only]]
-> 11bc5e74
System.Collections.Generic.Dictionary`2[[System.Threading.Tasks.Dataflow.ITargetBlock`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only]],
System.Threading.Tasks.Dataflow],[System.Threading.Tasks.Dataflow.Internal.TargetRegistry`1+LinkedTargetInfo[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only]], System.Threading.Tasks.Dataflow]]
-> 11c0e6c8
System.Collections.Generic.Dictionary`2+Entry[[System.Threading.Tasks.Dataflow.ITargetBlock`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only]],
System.Threading.Tasks.Dataflow],[System.Threading.Tasks.Dataflow.Internal.TargetRegistry`1+LinkedTargetInfo[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only]], System.Threading.Tasks.Dataflow]][]
-> 11c0e194
System.Threading.Tasks.Dataflow.ActionBlock`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only]]
-> 11c0e1d4
System.Threading.Tasks.Dataflow.Internal.TargetCore`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only]]
-> 11c0e1b4
System.Action`1[[System.Collections.Generic.KeyValuePair`2[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only],[System.Int64, mscorlib]],
mscorlib]]
-> 11c0e1a4
System.Threading.Tasks.Dataflow.ActionBlock`1+<>c__DisplayClass5[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only]]
-> 11c0e174 System.Action`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only]]
-> 11c0e0d4
Microsoft.VisualStudio.ProjectSystem.Utilities.Designers.ProjectDataSources+<>c__DisplayClass2`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only]]
-> 11c0e704 System.Threading.Tasks.Dataflow.Internal.Disposables+Disposable`3[[System.Object,
mscorlib],[System.Threading.Tasks.Dataflow.Internal.TargetRegistry`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only]],
System.Threading.Tasks.Dataflow],[System.Threading.Tasks.Dataflow.ITargetBlock`1[[Microsoft.VisualStudio.ProjectSystem.Designers.IProjectSnapshot,
Microsoft.VisualStudio.ProjectSystem.V14Only]], System.Threading.Tasks.Dataflow]]
-> 11bc5e20 System.Threading.Tasks.TaskCompletionSource`1[[System.Threading.Tasks.Dataflow.Internal.VoidResult,
System.Threading.Tasks.Dataflow]]
-> 11bc5e2c System.Threading.Tasks.Task`1[[System.Threading.Tasks.Dataflow.Internal.VoidResult,
System.Threading.Tasks.Dataflow]]
-> 11c0e8d4 System.Collections.Generic.List`1[[System.Object,
mscorlib]]
-> 11c0e8ec System.Object[]
-> 11c0e81c System.Threading.Tasks.StandardTaskContinuation
-> 11c0e71c System.Threading.Tasks.ContinuationTaskFromTask
-> 11c0e7f4 System.Threading.Tasks.Task+ContingentProperties
-> 11c0e7d0 System.Threading.ExecutionContext
-> 11c0e748 System.Runtime.Remoting.Messaging.LogicalCallContext
-> 11c0e76c System.Collections.Hashtable
-> 11c0e7a0 System.Collections.Hashtable+bucket[]
-> 11be94a0
Microsoft.VisualStudio.Threading.AsyncLocal`1+IdentityNode[[Microsoft.VisualStudio.Threading.AsyncReaderWriterLock+Awaiter,
Microsoft.VisualStudio.Threading]]
-> 11b8cfb0 Microsoft.VisualStudio.Threading.AsyncReaderWriterLock+Awaiter
(dependent handle)
Thread 1344:
10ebea40 62996a0a Microsoft.VisualStudio.ProjectSystem.ConfiguredProjectCache`1+<GetValueSlowAsync>d__1[[System.__Canon,
mscorlib]].MoveNext() [f:\dd\vsproject\cps\components\implementations\ConfiguredProjectCache.cs
@ 220]
ebp+a8: 10ebea48 (interior)
-> 11b8d024
Microsoft.VisualStudio.ProjectSystem.ConfiguredProjectCache`1+<GetValueSlowAsync>d__1[[System.ComponentModel.ICustomTypeDescriptor,
System]]
-> 11b8cfb0 Microsoft.VisualStudio.Threading.AsyncReaderWriterLock+Awaiter
10ebeb00 7184a467 System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext,
System.Threading.ContextCallback, System.Object, Boolean)
[f:\dd\NDP\clr\src\BCL\System\Threading\ExecutionContext.cs @ 825]
ebp+44: 10ebeb18
-> 11c0dcbc System.Threading.ExecutionContext
-> 11c0dce0 System.Runtime.Remoting.Messaging.LogicalCallContext
-> 11c0dd04 System.Collections.Hashtable
-> 11c0dd38 System.Collections.Hashtable+bucket[]
-> 11be94e8
Microsoft.VisualStudio.Threading.AsyncLocal`1+IdentityNode[[Microsoft.VisualStudio.Threading.AsyncReaderWriterLock+Awaiter,
Microsoft.VisualStudio.Threading]]
-> 11be94ac Microsoft.VisualStudio.Threading.AsyncReaderWriterLock+Awaiter
(dependent handle)
-> 11b8cfb0 Microsoft.VisualStudio.Threading.AsyncReaderWriterLock+Awaiter
Found 3 unique roots (run '!GCRoot -all' to see all roots).
The gcroot #1 is the one pointed to by an ExecutionContext, so that is where we can look to find the async state machine that is doing work that is holding the upgradeable read project lock. Gcroot #3 isn't interesting because it's redundant with #2 (rooted by the same thread).
What's also interesting here is gcroot #2, in that it's a very short chain and tells me there is actually a background thread that holds some relevant code. That suggests this might be a simple deadlock due to a violation of threading rule #1. Using the "Processes and Threads" window, I translate thread 1344 to thread #016 and I switch to it to print the callstack.
0:000> ~16s
eax=00000001 ebx=00000001 ecx=00000000 edx=00000000 esi=00000001 edi=00000001
eip=7763aaac esp=10ebe1b8 ebp=10ebe338 iopl=0 nv up ei pl nz na
pe nc
cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00000206
ntdll!NtWaitForMultipleObjects+0xc:
7763aaac c21400 ret 14h
0:016> k
# ChildEBP RetAddr
00 10ebe1b4 75660927 ntdll!NtWaitForMultipleObjects+0xc
[e:\9151.obj.x86fre\minkernel\ntdll\wow6432\objfre\i386\usrstubs.asm @ 825]
01 10ebe338 748460c0 KERNELBASE!WaitForMultipleObjectsEx+0xcc
[d:\9151\minkernel\kernelbase\synch.c @ 1471]
02 10ebe388 74845f53 clr!WaitForMultipleObjectsEx_SO_TOLERANT+0x3c
[f:\dd\ndp\clr\src\vm\threads.cpp @ 4892]
03 (Inline) -------- clr!Thread::DoAppropriateAptStateWait+0x35
[f:\dd\ndp\clr\src\vm\threads.cpp @ 4926]
04 10ebe414 74846044 clr!Thread::DoAppropriateWaitWorker+0x237
[f:\dd\ndp\clr\src\vm\threads.cpp @ 5066]
05 10ebe480 74846293 clr!Thread::DoAppropriateWait+0x64
[f:\dd\ndp\clr\src\vm\threads.cpp @ 4733]
06 10ebe4cc 74832918 clr!CLREventBase::WaitEx+0x128 [f:\dd\ndp\clr\src\vm\synch.cpp
@ 754]
07 10ebe4e4 748567a7 clr!CLREventBase::Wait+0x1a [f:\dd\ndp\clr\src\vm\synch.cpp
@ 675]
08 (Inline) -------- clr!Thread::Wait+0x17 [f:\dd\ndp\clr\src\vm\threads.cpp
@ 5551]
09 10ebe4f8 748568e5 clr!Thread::Block+0x25 [f:\dd\ndp\clr\src\vm\threads.cpp
@ 5508]
0a 10ebe5a8 748569c6 clr!SyncBlock::Wait+0x18d [f:\dd\ndp\clr\src\vm\syncblk.cpp
@ 3608]
0b (Inline) -------- clr!ObjHeader::Wait+0x24 [f:\dd\ndp\clr\src\vm\syncblk.cpp
@ 2787]
0c (Inline) -------- clr!Object::Wait+0x24 [f:\dd\ndp\clr\src\vm\object.h
@ 532]
0d 10ebe644 717cbbe3 clr!ObjectNative::WaitTimeout+0xcb
[f:\dd\ndp\clr\src\classlibnative\bcltype\objectnative.cpp @ 318]
0e 10ebe654 7180c9e0 mscorlib_ni!System.Threading.Monitor.Wait(System.Object,
Int32, Boolean)+0x17 [f:\dd\NDP\clr\src\BCL\System\Threading\Monitor.cs
@ 215]
0f 10ebe6ac 7182ac32 mscorlib_ni!System.Threading.Monitor.Wait(System.Object,
Int32)+0xc [f:\dd\NDP\clr\src\BCL\System\Threading\Monitor.cs @ 225]
10 10ebe6ac 718233a7 mscorlib_ni!System.Threading.ManualResetEventSlim.Wait(Int32,
System.Threading.CancellationToken)+0x182
[f:\dd\NDP\clr\src\BCL\System\Threading\ManualResetEventSlim.cs @ 657]
11 10ebe6ec 71865870 mscorlib_ni!System.Threading.Tasks.Task.SpinThenBlockingWait(Int32,
System.Threading.CancellationToken)+0x93 [f:\dd\NDP\clr\src\BCL\System\Threading\Tasks\Task.cs
@ 3341]
12 10ebe744 71f60792 mscorlib_ni!System.Threading.Tasks.Task.InternalWait(Int32,
System.Threading.CancellationToken)+0x148 [f:\dd\NDP\clr\src\BCL\System\Threading\Tasks\Task.cs
@ 3282]
13 10ebe754 629d9c1e
mscorlib_ni!System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(System.Threading.Tasks.Task)+0x1e
[f:\dd\NDP\clr\src\BCL\System\Runtime\CompilerServices\TaskAwaiter.cs @
165]
14 10ebe768 62f57322
Microsoft_VisualStudio_ProjectSystem_Implementation_ni!Microsoft.VisualStudio.ProjectSystem.Designers.ProjectSnapshotService.get_ProjectSnapshot()+0x66
[f:\dd\vsproject\cps\components\implementations\Designers\ProjectSnapshotService.cs
@ 111]
15 10ebe7d0 62f571f0
Microsoft_VisualStudio_ProjectSystem_VS_Implementation_ni!Microsoft.VisualStudio.ProjectSystem.VS.Implementation.Package.SimpleItemNode+<GetIsMissingItemAsync>d__1.MoveNext()+0x102
[f:\dd\vsproject\cps\components\VsComponents\Package\Nodes\SimpleItemNode.cs
@ 178]
16 10ebe824 62f571a6 mscorlib_ni!System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1[[System.__Canon,
mscorlib]].Start[[System.__Canon, mscorlib]](System.__Canon ByRef)+0xf0f605f8
[f:\dd\NDP\clr\src\BCL\System\Runtime\CompilerServices\AsyncMethodBuilder.cs
@ 459]
17 10ebe874 62f3242f
Microsoft_VisualStudio_ProjectSystem_VS_Implementation_ni!Microsoft.VisualStudio.ProjectSystem.VS.Implementation.Package.SimpleItemNode.GetIsMissingItemAsync()+0x3e
18 10ebe8ac 62f3239b
Microsoft_VisualStudio_ProjectSystem_VS_Implementation_ni!Microsoft.VisualStudio.ProjectSystem.VS.Implementation.Package.SimpleHierarchyNode+<CreatePropertiesAsync>d__1.MoveNext()+0x5f
[f:\dd\vsproject\cps\components\VsComponents\Package\Nodes\SimpleHierarchyNode.cs
@ 66]
19 10ebe900 62f32351 mscorlib_ni!System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1[[System.__Canon,
mscorlib]].Start[[System.__Canon, mscorlib]](System.__Canon ByRef)+0xf0f3b7a3
[f:\dd\NDP\clr\src\BCL\System\Runtime\CompilerServices\AsyncMethodBuilder.cs
@ 459]
1a 10ebe940 0d959b6d
Microsoft_VisualStudio_ProjectSystem_VS_Implementation_ni!Microsoft.VisualStudio.ProjectSystem.VS.Implementation.Package.SimpleHierarchyNode.CreatePropertiesAsync()+0x49
1b 10ebe97c 7182b89d
Microsoft_VisualStudio_ProjectSystem_Implementation_ni!Microsoft.VisualStudio.ProjectSystem.ConfiguredProjectCache`1+<>c__DisplayClass6+<<UpdateValue>b__8>d__0[[System.__Canon,
mscorlib]].MoveNext()+0xdd [f:\dd\vsproject\cps\components\implementations\ConfiguredProjectCache.cs
@ 296]
1c 10ebe984 7184a467 mscorlib_ni!System.Runtime.CompilerServices.AsyncMethodBuilderCore+MoveNextRunner.InvokeMoveNext(System.Object)+0x19
[f:\dd\NDP\clr\src\BCL\System\Runtime\CompilerServices\AsyncMethodBuilder.cs
@ 1090]
1d 10ebe9e8 7184a3b6 mscorlib_ni!System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext,
System.Threading.ContextCallback, System.Object, Boolean)+0xa7
[f:\dd\NDP\clr\src\BCL\System\Threading\ExecutionContext.cs @ 825]
1e 10ebe9fc 7182b803 mscorlib_ni!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext,
System.Threading.ContextCallback, System.Object, Boolean)+0x16
[f:\dd\NDP\clr\src\BCL\System\Threading\ExecutionContext.cs @ 775]
1f 10ebea34 0d959e4e mscorlib_ni!System.Runtime.CompilerServices.AsyncMethodBuilderCore+MoveNextRunner.Run()+0x5b
[f:\dd\NDP\clr\src\BCL\System\Runtime\CompilerServices\AsyncMethodBuilder.cs
@ 1070]
20 10ebeaf0 62996a0a
Microsoft_VisualStudio_ProjectSystem_Implementation_ni!Microsoft.VisualStudio.ProjectSystem.ConfiguredProjectCache`1+Awaiter[[System.__Canon,
mscorlib]].Complete()+0x16 [f:\dd\vsproject\cps\components\implementations\ConfiguredProjectCache.cs
@ 390]
21 10ebeaf0 7182b89d
Microsoft_VisualStudio_ProjectSystem_Implementation_ni!Microsoft.VisualStudio.ProjectSystem.ConfiguredProjectCache`1+<GetValueSlowAsync>d__1[[System.__Canon,
mscorlib]].MoveNext()+0x612 [f:\dd\vsproject\cps\components\implementations\ConfiguredProjectCache.cs
@ 220]
22 10ebeaf8 7184a467 mscorlib_ni!System.Runtime.CompilerServices.AsyncMethodBuilderCore+MoveNextRunner.InvokeMoveNext(System.Object)+0x19
[f:\dd\NDP\clr\src\BCL\System\Runtime\CompilerServices\AsyncMethodBuilder.cs
@ 1090]
23 10ebeb5c 7184a3b6 mscorlib_ni!System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext,
System.Threading.ContextCallback, System.Object, Boolean)+0xa7
[f:\dd\NDP\clr\src\BCL\System\Threading\ExecutionContext.cs @ 825]
24 10ebeb70 7182b803 mscorlib_ni!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext,
System.Threading.ContextCallback, System.Object, Boolean)+0x16
[f:\dd\NDP\clr\src\BCL\System\Threading\ExecutionContext.cs @ 775]
25 10ebeba8 7182b7a7 mscorlib_ni!System.Runtime.CompilerServices.AsyncMethodBuilderCore+MoveNextRunner.Run()+0x5b
[f:\dd\NDP\clr\src\BCL\System\Runtime\CompilerServices\AsyncMethodBuilder.cs
@ 1070]
26 10ebebfc 6d50f6e1 mscorlib_ni!System.Threading.Tasks.SynchronizationContextAwaitTaskContinuation.<.cctor>b__6(System.Object)+0x2b
[f:\dd\NDP\clr\src\BCL\System\Threading\Tasks\TaskContinuation.cs @ 491]
27 10ebebfc 6d50f5cc
Microsoft_VisualStudio_Threading_ni!Microsoft.VisualStudio.Threading.AsyncReaderWriterLock+NonConcurrentSynchronizationContext+<PostHelper>d__1.MoveNext()+0xe1
[f:\dd\vsproject\cps\Microsoft.VisualStudio.Threading\Microsoft.VisualStudio.Threading\AsyncReaderWriterLock.cs
@ 1874]
28 10ebec50 6d50f588 mscorlib_ni!System.Runtime.CompilerServices.AsyncVoidMethodBuilder.Start[[System.__Canon,
mscorlib]](System.__Canon ByRef)+0xfb518dfc
[f:\dd\NDP\clr\src\BCL\System\Runtime\CompilerServices\AsyncMethodBuilder.cs
@ 72]
29 10ebec9c 6d50f533
Microsoft_VisualStudio_Threading_ni!Microsoft.VisualStudio.Threading.AsyncReaderWriterLock+NonConcurrentSynchronizationContext.PostHelper(System.Threading.SendOrPostCallback,
System.Object)+0x48
2a 10ebed14 717ef226
Microsoft_VisualStudio_Threading_ni!Microsoft.VisualStudio.Threading.AsyncReaderWriterLock+NonConcurrentSynchronizationContext.<Post>b__0(System.Object)+0x33
[f:\dd\vsproject\cps\Microsoft.VisualStudio.Threading\Microsoft.VisualStudio.Threading\AsyncReaderWriterLock.cs
@ 1832]
2b 10ebed14 7184a467 mscorlib_ni!System.Threading.QueueUserWorkItemCallback.WaitCallback_Context(System.Object)+0x42
[f:\dd\NDP\clr\src\BCL\System\Threading\ThreadPool.cs @ 1274]
2c 10ebed14 7184a3b6 mscorlib_ni!System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext,
System.Threading.ContextCallback, System.Object, Boolean)+0xa7
[f:\dd\NDP\clr\src\BCL\System\Threading\ExecutionContext.cs @ 825]
2d 10ebed28 71810470 mscorlib_ni!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext,
System.Threading.ContextCallback, System.Object, Boolean)+0x16
[f:\dd\NDP\clr\src\BCL\System\Threading\ExecutionContext.cs @ 775]
2e 10ebed44 7180fc6b mscorlib_ni!System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem()+0x60
[f:\dd\NDP\clr\src\BCL\System\Threading\ThreadPool.cs @ 1252]
2f 10ebed94 7180fb1a mscorlib_ni!System.Threading.ThreadPoolWorkQueue.Dispatch()+0x14b
[f:\dd\NDP\clr\src\BCL\System\Threading\ThreadPool.cs @ 820]
30 10ebeda4 748313b6 mscorlib_ni!System.Threading._ThreadPoolWaitCallback.PerformWaitCallback()+0xa
[f:\dd\NDP\clr\src\BCL\System\Threading\ThreadPool.cs @ 1161]
31 10ebeda4 74846970 clr!CallDescrWorkerInternal+0x34
[f:\dd\ndp\clr\src\vm\i386\asmhelpers.asm @ 732]
32 10ebedf8 74847f65 clr!CallDescrWorkerWithHandler+0x6b
[f:\dd\ndp\clr\src\vm\callhelpers.cpp @ 91]
33 10ebee6c 7491b094 clr!MethodDescCallSite::CallTargetWorker+0x152
[f:\dd\ndp\clr\src\vm\callhelpers.cpp @ 649]
34 (Inline) -------- clr!MethodDescCallSite::Call_RetBool+0xb
[f:\dd\ndp\clr\src\vm\callhelpers.h @ 423]
35 10ebeeec 74847fb5 clr!QueueUserWorkItemManagedCallback+0x23
[f:\dd\ndp\clr\src\vm\comthreadpool.cpp @ 513]
36 10ebef04 74848023 clr!ManagedThreadBase_DispatchInner+0x67
[f:\dd\ndp\clr\src\vm\threads.cpp @ 18093]
37 10ebefa8 748480f0 clr!ManagedThreadBase_DispatchMiddle+0x82
[f:\dd\ndp\clr\src\vm\threads.cpp @ 18143]
38 10ebf004 7484815f clr!ManagedThreadBase_DispatchOuter+0x5b
[f:\dd\ndp\clr\src\vm\threads.cpp @ 18397]
39 10ebf028 7491b028 clr!ManagedThreadBase_FullTransitionWithAD+0x2f
[f:\dd\ndp\clr\src\vm\threads.cpp @ 18461]
3a (Inline) -------- clr!ManagedThreadBase::ThreadPool+0x10
[f:\dd\ndp\clr\src\vm\threads.cpp @ 18502]
3b 10ebf0d8 7491ce3f clr!ManagedPerAppDomainTPCount::DispatchWorkItem+0xc4
[f:\dd\ndp\clr\src\vm\threadpoolrequest.cpp @ 760]
3c 10ebf0ec 7491cbd2 clr!ThreadpoolMgr::ExecuteWorkRequest+0x42
[f:\dd\ndp\clr\src\vm\win32threadpool.cpp @ 1863]
3d 10ebf154 74846b2c clr!ThreadpoolMgr::WorkerThreadStart+0x36b
[f:\dd\ndp\clr\src\vm\win32threadpool.cpp @ 2330]
3e 10ebfaf4 757f919f clr!Thread::intermediateThreadProc+0x4d
[f:\dd\ndp\clr\src\vm\threads.cpp @ 3478]
3f 10ebfb00 77650bbb kernel32!BaseThreadInitThunk+0xe
[d:\blue_gdr\base\win32\client\thread.c @ 72]
40 10ebfb44 77650b91 ntdll!__RtlUserThreadStart+0x20 [d:\9151\minkernel\ntdll\rtlstrt.c
@ 1024]
41 10ebfb54 00000000 ntdll!_RtlUserThreadStart+0x1b [d:\9151\minkernel\ntdll\rtlstrt.c
@ 939]
Sure enough, we have a call that synchronously blocking piece of code in ProjectSnapshotService.ProjectSnapshot that isn't using the JoinableTaskFactory. This is a really bad thing and can lead to deadlocks (perhaps this very one!). We should fix this.
Let's move on to find who actually acquired the project upgradeable read lock though. From GCRoot#2, which is conveniently short, we see ConfiguredProjectCache.GetValueSlowAsync is holding it. We learn by code inspection that this method may take either an upgradeable read or a read lock. Let's inspect the fields of this object to determine which one it would have taken to verify. Copied from above, the gcroot is:
10ebea40 62996a0a Microsoft.VisualStudio.ProjectSystem.ConfiguredProjectCache`1+<GetValueSlowAsync>d__1[[System.__Canon,
mscorlib]].MoveNext() [f:\dd\vsproject\cps\components\implementations\ConfiguredProjectCache.cs
@ 220]
ebp+a8: 10ebea48 (interior)
-> 11b8d024
Microsoft.VisualStudio.ProjectSystem.ConfiguredProjectCache`1+<GetValueSlowAsync>d__1[[System.ComponentModel.ICustomTypeDescriptor,
System]]
-> 11b8cfb0 Microsoft.VisualStudio.Threading.AsyncReaderWriterLock+Awaiter
0:016> !do 11b8d024
Name: Microsoft.VisualStudio.ProjectSystem.ConfiguredProjectCache`1+<GetValueSlowAsync>d__1[[System.ComponentModel.ICustomTypeDescriptor,
System]]
MethodTable: 62a1618c
EEClass: 628c6310
Size: 72(0x48) bytes
File: C:\Windows\Microsoft.Net\assembly\GAC_MSIL\Microsoft.VisualStudio.ProjectSystem.Implementation\v4.0_14.0.0.0__b03f5f7f11d50a3a\Microsoft.VisualStudio.ProjectSystem.Implementation.dll
Fields:
MT Field Offset Type VT Attr Value Name
7188fbb8 40006db 10 System.Int32 1 instance -1
<>1__state
718a6778 40006dc 18 ...Canon, mscorlib]] 1 instance 11b8d03c
<>t__builder
62d3a5d8 40006dd 24 ...ojectLockReleaser 1 instance 11b8d048
<access>5__1
62befc34 40006de 4 ...Canon, mscorlib]] 0 instance 11b8cfa0
CS$<>8__locals1
71896038 40006df 14 System.Boolean 1 instance 0
isWriteLockHeld
62a0bd7c 40006e0 8 ...Canon, mscorlib]] 0 instance 11b8cf60
<>4__this
6d51c598 40006e1 c ...Canon, mscorlib]] 0 instance 11c0de0c
<valueTask>5__3
62d3a658 40006e2 30 ...rojectLockAwaiter 1 instance 11b8d054
<>u__$awaiter3
634e4ec0 40006e3 3c ...Microsoft.Build]] 1 instance 11b8d060
<>u__$awaiter4
718a6818 40006e4 40 ...Canon, mscorlib]] 1 instance 11b8d064
<>u__$awaiter5
0:016> !DumpObj /d 11b8cf60
Name: Microsoft.VisualStudio.ProjectSystem.ConfiguredProjectCache`1[[System.ComponentModel.ICustomTypeDescriptor,
System]]
MethodTable: 62a1f170
EEClass: 628c5868
Size: 52(0x34) bytes
File: C:\Windows\Microsoft.Net\assembly\GAC_MSIL\Microsoft.VisualStudio.ProjectSystem.Implementation\v4.0_14.0.0.0__b03f5f7f11d50a3a\Microsoft.VisualStudio.ProjectSystem.Implementation.dll
Fields:
MT Field Offset Type VT Attr Value Name
62a0a174 4000041 4 ...ojectCacheFactory 0 instance 11427f7c
factory
7188e0c8 4000042 8 System.Object 0 instance 11b8cf94
syncObject
00000000 4000043 c 0 instance 11b8cf40
cacheUpdateDelegate
62d1b24c 4000044 20 System.Int32 1 instance 2
options
6d51c598 4000045 10 ...Canon, mscorlib]] 0 instance 11c0de0c cache
6d51c598 4000046 14 ...Canon, mscorlib]] 0 instance 00000000
cacheUnderWriteLock
71892d34 4000047 18 System.IComparable 0 instance 1142620c
projectVersion
7188fbb8 4000048 24 System.Int32 1 instance 71
evaluationCounter
7188fbb8 4000049 28 System.Int32 1 instance -1
evaluationCounterUnderWriteLock
714c01c8 400004a 1c ...tring, mscorlib]] 0 instance 00000000
globalPropertiesAtCacheRefresh
71896038 400004b 2c System.Boolean 1 instance 0
explicitlyInvalidated
71896038 400004c 2d System.Boolean 1 instance 0
explicitlyInvalidatedUnderWriteLock
And we see from code inspection that for ConfiguredProjectCacheOptions,
a value of 2 means ValueFactoryRequiresUpgradeableRead.
Q.E.D. we have identified the holder of the upgradeable read lock.