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Avoid rare deadlocks when using TypeDescriptor (#103835)
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@steveharter
steveharter committed Jun 26, 2024
1 parent 9317db0 commit c241cc9
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Showing 2 changed files with 28 additions and 25 deletions.
23 changes: 11 additions & 12 deletions ....ComponentModel.TypeConverter/src/System/ComponentModel/ReflectTypeDescriptionProvider.cs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -82,7 +82,6 @@ private static Type[] InitializeSkipInterfaceAttributeList()

internal static Guid ExtenderProviderKey { get; } = Guid.NewGuid();

private static readonly object s_internalSyncObject = new object();
/// <summary>
/// Creates a new ReflectTypeDescriptionProvider. The type is the
/// type we will obtain type information for.
Expand Down Expand Up @@ -224,7 +223,7 @@ internal static void AddEditorTable(Type editorBaseType, Hashtable table)

Debug.Assert(table != null, "COMPAT: Editor table should not be null"); // don't throw; RTM didn't so we can't do it either.

lock (s_internalSyncObject)
lock (TypeDescriptor.s_commonSyncObject)
{
Hashtable editorTables = EditorTables;
if (!editorTables.ContainsKey(editorBaseType))
Expand Down Expand Up @@ -436,7 +435,7 @@ internal TypeConverter GetConverterFromRegisteredType(Type type, object? instanc
//
if (table == null)
{
lock (s_internalSyncObject)
lock (TypeDescriptor.s_commonSyncObject)
{
table = editorTables[editorBaseType];
if (table == null)
Expand Down Expand Up @@ -863,7 +862,7 @@ internal Type[] GetPopulatedTypes(Module module)
{
List<Type> typeList = new List<Type>();

lock (s_internalSyncObject)
lock (TypeDescriptor.s_commonSyncObject)
{
Dictionary<Type, ReflectedTypeData>? typeData = _typeData;
if (typeData != null)
Expand Down Expand Up @@ -936,7 +935,7 @@ public override Type GetReflectionType(
return td;
}

lock (s_internalSyncObject)
lock (TypeDescriptor.s_commonSyncObject)
{
if (_typeData != null && _typeData.TryGetValue(type, out td))
{
Expand Down Expand Up @@ -999,7 +998,7 @@ private ReflectedTypeData GetTypeDataFromRegisteredType(Type type)
return;
}

lock (s_internalSyncObject)
lock (TypeDescriptor.s_commonSyncObject)
{
if (_typeData != null && _typeData.ContainsKey(componentType))
{
Expand All @@ -1024,7 +1023,7 @@ private ReflectedTypeData GetOrRegisterType(Type type)
return td;
}

lock (s_internalSyncObject)
lock (TypeDescriptor.s_commonSyncObject)
{
if (_typeData != null && _typeData.TryGetValue(type, out td))
{
Expand Down Expand Up @@ -1122,7 +1121,7 @@ internal static Attribute[] ReflectGetAttributes(Type type)
return attrs;
}

lock (s_internalSyncObject)
lock (TypeDescriptor.s_commonSyncObject)
{
attrs = (Attribute[]?)attributeCache[type];
if (attrs == null)
Expand Down Expand Up @@ -1150,7 +1149,7 @@ internal static Attribute[] ReflectGetAttributes(MemberInfo member)
return attrs;
}

lock (s_internalSyncObject)
lock (TypeDescriptor.s_commonSyncObject)
{
attrs = (Attribute[]?)attributeCache[member];
if (attrs == null)
Expand Down Expand Up @@ -1178,7 +1177,7 @@ private static EventDescriptor[] ReflectGetEvents(Type type)
return events;
}

lock (s_internalSyncObject)
lock (TypeDescriptor.s_commonSyncObject)
{
events = (EventDescriptor[]?)eventCache[type];
if (events == null)
Expand Down Expand Up @@ -1275,7 +1274,7 @@ private static PropertyDescriptor[] ReflectGetExtendedProperties(IExtenderProvid
ReflectPropertyDescriptor[]? extendedProperties = (ReflectPropertyDescriptor[]?)extendedPropertyCache[providerType];
if (extendedProperties == null)
{
lock (s_internalSyncObject)
lock (TypeDescriptor.s_commonSyncObject)
{
extendedProperties = (ReflectPropertyDescriptor[]?)extendedPropertyCache[providerType];

Expand Down Expand Up @@ -1363,7 +1362,7 @@ private static PropertyDescriptor[] ReflectGetPropertiesImpl(Type type)
return properties;
}

lock (s_internalSyncObject)
lock (TypeDescriptor.s_commonSyncObject)
{
properties = (PropertyDescriptor[]?)propertyCache[type];

Expand Down
30 changes: 17 additions & 13 deletions ...libraries/System.ComponentModel.TypeConverter/src/System/ComponentModel/TypeDescriptor.cs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -48,6 +48,13 @@ public sealed class TypeDescriptor
// class load anyway.
private static readonly WeakHashtable s_providerTable = new WeakHashtable();

// This lock object protects access to several thread-unsafe areas below, and is a single lock object to prevent deadlocks.
// - During s_providerTypeTable access.
// - To act as a mutex for CheckDefaultProvider() when it needs to create the default provider, which may re-enter the above case.
// - For cache access in the ReflectTypeDescriptionProvider class which may re-enter the above case.
// - For logic added by consumers, such as custom provider, constructor and property logic, which may re-enter the above cases in unexpected ways.
internal static readonly object s_commonSyncObject = new object();

// A direct mapping from type to provider.
private static readonly Dictionary<Type, TypeDescriptionNode> s_providerTypeTable = new Dictionary<Type, TypeDescriptionNode>();

Expand Down Expand Up @@ -240,7 +247,7 @@ public static void AddProvider(TypeDescriptionProvider provider, Type type)
ArgumentNullException.ThrowIfNull(provider);
ArgumentNullException.ThrowIfNull(type);

lock (s_providerTable)
lock (s_commonSyncObject)
{
// Get the root node, hook it up, and stuff it back into
// the provider cache.
Expand Down Expand Up @@ -270,7 +277,7 @@ public static void AddProvider(TypeDescriptionProvider provider, object instance

// Get the root node, hook it up, and stuff it back into
// the provider cache.
lock (s_providerTable)
lock (s_commonSyncObject)
{
refreshNeeded = s_providerTable.ContainsKey(instance);
TypeDescriptionNode node = NodeFor(instance, true);
Expand Down Expand Up @@ -331,18 +338,15 @@ private static void CheckDefaultProvider(Type type)
return;
}

// Lock on s_providerTable even though s_providerTable is not modified here.
// Using a single lock prevents deadlocks since other methods that call into or are called
// by this method also lock on s_providerTable and the ordering of the locks may be different.
lock (s_providerTable)
lock (s_commonSyncObject)
{
AddDefaultProvider(type);
}
}

/// <summary>
/// Add the default provider, if it exists.
/// For threading, this is always called under a 'lock (s_providerTable)'.
/// For threading, this is always called under a 'lock (s_commonSyncObject)'.
/// </summary>
private static void AddDefaultProvider(Type type)
{
Expand Down Expand Up @@ -1666,7 +1670,7 @@ private static TypeDescriptionNode NodeFor(Type type, bool createDelegator)

if (searchType == typeof(object) || baseType == null)
{
lock (s_providerTable)
lock (s_commonSyncObject)
{
node = (TypeDescriptionNode?)s_providerTable[searchType];

Expand All @@ -1682,7 +1686,7 @@ private static TypeDescriptionNode NodeFor(Type type, bool createDelegator)
else if (createDelegator)
{
node = new TypeDescriptionNode(new DelegatingTypeDescriptionProvider(baseType));
lock (s_providerTable)
lock (s_commonSyncObject)
{
s_providerTypeTable.TryAdd(searchType, node);
}
Expand Down Expand Up @@ -1793,7 +1797,7 @@ private static TypeDescriptionNode NodeFor(object instance, bool createDelegator
/// </summary>
private static void NodeRemove(object key, TypeDescriptionProvider provider)
{
lock (s_providerTable)
lock (s_commonSyncObject)
{
TypeDescriptionNode? head = (TypeDescriptionNode?)s_providerTable[key];
TypeDescriptionNode? target = head;
Expand Down Expand Up @@ -2314,7 +2318,7 @@ private static void Refresh(object component, bool refreshReflectionProvider)
{
Type type = component.GetType();

lock (s_providerTable)
lock (s_commonSyncObject)
{
// ReflectTypeDescritionProvider is only bound to object, but we
// need go to through the entire table to try to find custom
Expand Down Expand Up @@ -2398,7 +2402,7 @@ public static void Refresh(Type type)

bool found = false;

lock (s_providerTable)
lock (s_commonSyncObject)
{
// ReflectTypeDescritionProvider is only bound to object, but we
// need go to through the entire table to try to find custom
Expand Down Expand Up @@ -2463,7 +2467,7 @@ public static void Refresh(Module module)
// each of these levels.
Hashtable? refreshedTypes = null;

lock (s_providerTable)
lock (s_commonSyncObject)
{
// Manual use of IDictionaryEnumerator instead of foreach to avoid DictionaryEntry box allocations.
IDictionaryEnumerator e = s_providerTable.GetEnumerator();
Expand Down

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