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Add a new GC handle and use it to simplify NativeAOT corelib #99512

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98 changes: 63 additions & 35 deletions src/coreclr/System.Private.CoreLib/src/System/Runtime/DependentHandle.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -52,9 +52,16 @@ public partial struct DependentHandle : IDisposable
//
// This struct intentionally does no self-synchronization. It's up to the caller to
// to use DependentHandles in a thread-safe way.
//
// There are two types of dependant handles: "normal" and "defer finalize". The "defer
// finalize" version promotes the secondary until the primary has been completely collected.
// The low order bit of the handle is stolen to indicate that the handle is the "defer finalize"
// flavor. It should be masked off before using.
// =========================================================================================

private IntPtr _handle;
private const nint IsDeferFinalizeBit = 1;

private nint _taggedHandle;

/// <summary>
/// Initializes a new instance of the <see cref="DependentHandle"/> struct with the specified arguments.
Expand All @@ -63,18 +70,33 @@ public partial struct DependentHandle : IDisposable
/// <param name="dependent">The dependent object instance to associate with <paramref name="target"/>.</param>
public DependentHandle(object? target, object? dependent)
{
IntPtr handle = InternalAlloc(target, dependent);
IntPtr handle = InternalAlloc(false, target, dependent);
if (handle == 0)
handle = InternalAllocWithGCTransition(false, target, dependent);
_taggedHandle = handle;
}

/// <summary>
/// Initializes a new instance of the <see cref="DependentHandle"/> struct with the specified arguments.
/// </summary>
/// <param name="isDeferFinalize">If true, the dependent is not finalized until the target is complexly collected.</param>
/// <param name="target">The target object instance to track.</param>
/// <param name="dependent">The dependent object instance to associate with <paramref name="target"/>.</param>
internal DependentHandle(bool isDeferFinalize, object? target, object? dependent)
{
// no need to check for null result: InternalInitialize expected to throw OOM.
IntPtr handle = InternalAlloc(isDeferFinalize, target, dependent);
if (handle == 0)
handle = InternalAllocWithGCTransition(target, dependent);
_handle = handle;
handle = InternalAllocWithGCTransition(isDeferFinalize, target, dependent);
_taggedHandle = handle | (isDeferFinalize ? IsDeferFinalizeBit : 0);
}

/// <summary>
/// Gets a value indicating whether this instance was constructed with
/// <see cref="DependentHandle(object?, object?)"/> and has not yet been disposed.
/// </summary>
/// <remarks>This property is thread-safe.</remarks>
public readonly bool IsAllocated => _handle != 0;
public readonly bool IsAllocated => _taggedHandle != 0;

/// <summary>
/// Gets or sets the target object instance for the current handle. The target can only be set to a <see langword="null"/> value
Expand All @@ -88,7 +110,7 @@ public object? Target
{
readonly get
{
IntPtr handle = _handle;
nint handle = _taggedHandle & ~IsDeferFinalizeBit;

if (handle == 0)
{
Expand All @@ -99,7 +121,7 @@ readonly get
}
set
{
IntPtr handle = _handle;
nint handle = _taggedHandle & ~IsDeferFinalizeBit;

if (handle == 0 || value is not null)
{
Expand All @@ -125,7 +147,7 @@ public object? Dependent
{
readonly get
{
IntPtr handle = _handle;
nint handle = _taggedHandle & ~IsDeferFinalizeBit;

if (handle == 0)
{
Expand All @@ -136,14 +158,16 @@ readonly get
}
set
{
IntPtr handle = _handle;
nint taggedHandle = _taggedHandle;

if (handle == 0)
if (taggedHandle == 0)
{
ThrowHelper.ThrowInvalidOperationException();
}

InternalSetDependent(handle, value);
nint handle = taggedHandle & ~IsDeferFinalizeBit;
bool isDeferFinalize = (taggedHandle & IsDeferFinalizeBit) != 0;
InternalSetDependent(isDeferFinalize, handle, value);
}
}

Expand All @@ -161,7 +185,7 @@ public readonly (object? Target, object? Dependent) TargetAndDependent
{
get
{
IntPtr handle = _handle;
nint handle = _taggedHandle & ~IsDeferFinalizeBit;

if (handle == 0)
{
Expand All @@ -181,7 +205,7 @@ public readonly (object? Target, object? Dependent) TargetAndDependent
/// <remarks>This method mirrors <see cref="Target"/>, but without the allocation check.</remarks>
internal readonly object? UnsafeGetTarget()
{
return InternalGetTarget(_handle);
return InternalGetTarget(_taggedHandle & ~IsDeferFinalizeBit);
}

/// <summary>
Expand All @@ -196,7 +220,7 @@ public readonly (object? Target, object? Dependent) TargetAndDependent
/// </remarks>
internal readonly object? UnsafeGetTargetAndDependent(out object? dependent)
{
return InternalGetTargetAndDependent(_handle, out dependent);
return InternalGetTargetAndDependent(_taggedHandle & ~IsDeferFinalizeBit, out dependent);
}

/// <summary>
Expand All @@ -205,7 +229,7 @@ public readonly (object? Target, object? Dependent) TargetAndDependent
/// <remarks>This method mirrors the <see cref="Target"/> setter, but without allocation and input checks.</remarks>
internal readonly void UnsafeSetTargetToNull()
{
InternalSetTargetToNull(_handle);
InternalSetTargetToNull(_taggedHandle & ~IsDeferFinalizeBit);
}

/// <summary>
Expand All @@ -214,7 +238,9 @@ internal readonly void UnsafeSetTargetToNull()
/// <remarks>This method mirrors <see cref="Dependent"/>, but without the allocation check.</remarks>
internal readonly void UnsafeSetDependent(object? dependent)
{
InternalSetDependent(_handle, dependent);
nint handle = _taggedHandle & ~IsDeferFinalizeBit;
bool isDeferFinalize = (_taggedHandle & IsDeferFinalizeBit) != 0;
InternalSetDependent(isDeferFinalize, handle, dependent);
}

/// <inheritdoc cref="IDisposable.Dispose"/>
Expand All @@ -223,61 +249,63 @@ public void Dispose()
{
// Forces the DependentHandle back to non-allocated state
// (if not already there) and frees the handle if needed.
IntPtr handle = _handle;
nint taggedHandle = _taggedHandle;

if (handle != 0)
if (taggedHandle != 0)
{
_handle = 0;
_taggedHandle = 0;

if (!InternalFree(handle))
nint handle = taggedHandle & ~IsDeferFinalizeBit;
bool isDeferFinalize = (taggedHandle & IsDeferFinalizeBit) != 0;
if (!InternalFree(isDeferFinalize, handle))
{
InternalFreeWithGCTransition(handle);
InternalFreeWithGCTransition(isDeferFinalize, handle);
}
}
}

[MethodImpl(MethodImplOptions.InternalCall)]
private static extern IntPtr InternalAlloc(object? target, object? dependent);
private static extern IntPtr InternalAlloc(bool isDeferFinalize, object? target, object? dependent);

[MethodImpl(MethodImplOptions.NoInlining)]
private static IntPtr InternalAllocWithGCTransition(object? target, object? dependent)
=> _InternalAllocWithGCTransition(ObjectHandleOnStack.Create(ref target), ObjectHandleOnStack.Create(ref dependent));
private static IntPtr InternalAllocWithGCTransition(bool isDeferFinalize, object? target, object? dependent)
=> _InternalAllocWithGCTransition(isDeferFinalize, ObjectHandleOnStack.Create(ref target), ObjectHandleOnStack.Create(ref dependent));

[LibraryImport(RuntimeHelpers.QCall, EntryPoint = "DependentHandle_InternalAllocWithGCTransition")]
private static partial IntPtr _InternalAllocWithGCTransition(ObjectHandleOnStack target, ObjectHandleOnStack dependent);
private static partial IntPtr _InternalAllocWithGCTransition([MarshalAs(UnmanagedType.Bool)] bool isDeferFinalize, ObjectHandleOnStack target, ObjectHandleOnStack dependent);

#if DEBUG
[MethodImpl(MethodImplOptions.InternalCall)]
private static extern object? InternalGetTarget(IntPtr dependentHandle);
private static extern object? InternalGetTarget(nint dependentHandle);
#else
// This optimization is the same that is used in GCHandle in RELEASE mode.
// This is not used in DEBUG builds as the runtime performs additional checks.
// The logic below is the inlined copy of ObjectFromHandle in the unmanaged runtime.
#pragma warning disable 8500 // address of managed types
private static unsafe object? InternalGetTarget(IntPtr dependentHandle) => *(object*)dependentHandle;
private static unsafe object? InternalGetTarget(nint dependentHandle) => *(object*)dependentHandle;
#pragma warning restore 8500
#endif

[MethodImpl(MethodImplOptions.InternalCall)]
private static extern object? InternalGetDependent(IntPtr dependentHandle);
private static extern object? InternalGetDependent(nint dependentHandle);

[MethodImpl(MethodImplOptions.InternalCall)]
private static extern object? InternalGetTargetAndDependent(IntPtr dependentHandle, out object? dependent);
private static extern object? InternalGetTargetAndDependent(nint dependentHandle, out object? dependent);

[MethodImpl(MethodImplOptions.InternalCall)]
private static extern void InternalSetDependent(IntPtr dependentHandle, object? dependent);
private static extern void InternalSetDependent(bool isDeferFinalize, nint dependentHandle, object? dependent);

[MethodImpl(MethodImplOptions.InternalCall)]
private static extern void InternalSetTargetToNull(IntPtr dependentHandle);
private static extern void InternalSetTargetToNull(nint dependentHandle);

[MethodImpl(MethodImplOptions.InternalCall)]
private static extern bool InternalFree(IntPtr dependentHandle);
private static extern bool InternalFree(bool isDeferFinalize, IntPtr dependentHandle);

[MethodImpl(MethodImplOptions.NoInlining)]
private static void InternalFreeWithGCTransition(IntPtr dependentHandle)
=> _InternalFreeWithGCTransition(dependentHandle);
private static void InternalFreeWithGCTransition(bool isDeferFinalize, IntPtr dependentHandle)
=> _InternalFreeWithGCTransition(isDeferFinalize, dependentHandle);

[LibraryImport(RuntimeHelpers.QCall, EntryPoint = "DependentHandle_InternalFreeWithGCTransition")]
private static partial void _InternalFreeWithGCTransition(IntPtr dependentHandle);
private static partial void _InternalFreeWithGCTransition([MarshalAs(UnmanagedType.Bool)] bool isDeferFinalize, IntPtr dependentHandle);
}
}
2 changes: 1 addition & 1 deletion src/coreclr/debug/daccess/daccess.cpp
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Expand Up @@ -7740,7 +7740,7 @@ void CALLBACK DacHandleWalker::EnumCallback(PTR_UNCHECKED_OBJECTREF handle, uint

data.Handle = TO_CDADDR(handle.GetAddr());
data.Type = param->Type;
if (param->Type == HNDTYPE_DEPENDENT)
if (param->Type == HNDTYPE_DEPENDENT || param->Type == HNDTYPE_DEPENDENT_DEFER_FINALIZE)
data.Secondary = GetDependentHandleSecondary(handle.GetAddr()).GetAddr();
else
data.Secondary = 0;
Expand Down
8 changes: 8 additions & 0 deletions src/coreclr/debug/daccess/dacdbiimpl.cpp
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Expand Up @@ -7582,6 +7582,9 @@ UINT32 DacRefWalker::GetHandleWalkerMask()
if (mHandleMask & CorHandleStrongSizedByref)
result |= (1 << HNDTYPE_SIZEDREF);

if (mHandleMask & CorHandleStrongDependentDeferFinalize)
result |= (1 << HNDTYPE_DEPENDENT_DEFER_FINALIZE);

return result;
}

Expand Down Expand Up @@ -7721,6 +7724,11 @@ HRESULT DacHandleWalker::Next(ULONG count, DacGcReference roots[], ULONG *pFetch
case HNDTYPE_SIZEDREF:
roots[i].dwType = (DWORD)CorHandleStrongSizedByref;
break;

case HNDTYPE_DEPENDENT_DEFER_FINALIZE:
roots[i].dwType = (DWORD)CorHandleStrongDependentDeferFinalize;
roots[i].i64ExtraData = GetDependentHandleSecondary(CLRDATA_ADDRESS_TO_TADDR(handle.Handle)).GetAddr();
break;
}
}

Expand Down
4 changes: 2 additions & 2 deletions src/coreclr/debug/daccess/request.cpp
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Expand Up @@ -3255,7 +3255,7 @@ ClrDataAccess::GetThreadLocalModuleData(CLRDATA_ADDRESS thread, unsigned int ind
HRESULT ClrDataAccess::GetHandleEnum(ISOSHandleEnum **ppHandleEnum)
{
unsigned int types[] = {HNDTYPE_WEAK_SHORT, HNDTYPE_WEAK_LONG, HNDTYPE_STRONG, HNDTYPE_PINNED, HNDTYPE_DEPENDENT,
HNDTYPE_SIZEDREF,
HNDTYPE_SIZEDREF, HNDTYPE_DEPENDENT_DEFER_FINALIZE,
#if defined(FEATURE_COMINTEROP) || defined(FEATURE_COMWRAPPERS) || defined(FEATURE_OBJCMARSHAL)
HNDTYPE_REFCOUNTED,
#endif // FEATURE_COMINTEROP || FEATURE_COMWRAPPERS || FEATURE_OBJCMARSHAL
Expand Down Expand Up @@ -3293,7 +3293,7 @@ HRESULT ClrDataAccess::GetHandleEnumForGC(unsigned int gen, ISOSHandleEnum **ppH
SOSDacEnter();

unsigned int types[] = {HNDTYPE_WEAK_SHORT, HNDTYPE_WEAK_LONG, HNDTYPE_STRONG, HNDTYPE_PINNED, HNDTYPE_DEPENDENT,
HNDTYPE_SIZEDREF,
HNDTYPE_SIZEDREF, HNDTYPE_DEPENDENT_DEFER_FINALIZE,
#if defined(FEATURE_COMINTEROP) || defined(FEATURE_COMWRAPPERS) || defined(FEATURE_OBJCMARSHAL)
HNDTYPE_REFCOUNTED,
#endif // FEATURE_COMINTEROP || FEATURE_COMWRAPPERS || FEATURE_OBJCMARSHAL
Expand Down
14 changes: 8 additions & 6 deletions src/coreclr/gc/gchandletable.cpp
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Expand Up @@ -89,16 +89,18 @@ OBJECTHANDLE GCHandleStore::CreateHandleWithExtraInfo(Object* object, HandleType
return ::HndCreateHandle(handletable, type, ObjectToOBJECTREF(object), reinterpret_cast<uintptr_t>(pExtraInfo));
}

OBJECTHANDLE GCHandleStore::CreateDependentHandle(Object* primary, Object* secondary)
OBJECTHANDLE GCHandleStore::CreateDependentHandle(HandleType type, Object* primary, Object* secondary)
{
_ASSERTE(type == HNDTYPE_DEPENDENT || type == HNDTYPE_DEPENDENT_DEFER_FINALIZE);

HHANDLETABLE handletable = _underlyingBucket.pTable[GetCurrentThreadHomeHeapNumber()];
OBJECTHANDLE handle = ::HndCreateHandle(handletable, HNDTYPE_DEPENDENT, ObjectToOBJECTREF(primary));
OBJECTHANDLE handle = ::HndCreateHandle(handletable, type, ObjectToOBJECTREF(primary));
if (!handle)
{
return nullptr;
}

::SetDependentHandleSecondary(handle, ObjectToOBJECTREF(secondary));
::SetDependentHandleSecondary(type, handle, ObjectToOBJECTREF(secondary));
return handle;
}

Expand Down Expand Up @@ -195,9 +197,9 @@ bool GCHandleManager::StoreObjectInHandleIfNull(OBJECTHANDLE handle, Object* obj
return !!::HndFirstAssignHandle(handle, ObjectToOBJECTREF(object));
}

void GCHandleManager::SetDependentHandleSecondary(OBJECTHANDLE handle, Object* object)
void GCHandleManager::SetDependentHandleSecondary(HandleType type, OBJECTHANDLE handle, Object* object)
{
::SetDependentHandleSecondary(handle, ObjectToOBJECTREF(object));
::SetDependentHandleSecondary(type, handle, ObjectToOBJECTREF(object));
}

Object* GCHandleManager::GetDependentHandleSecondary(OBJECTHANDLE handle)
Expand All @@ -213,7 +215,7 @@ Object* GCHandleManager::InterlockedCompareExchangeObjectInHandle(OBJECTHANDLE h
HandleType GCHandleManager::HandleFetchType(OBJECTHANDLE handle)
{
uint32_t type = ::HandleFetchType(handle);
assert(type >= HNDTYPE_WEAK_SHORT && type <= HNDTYPE_WEAK_NATIVE_COM);
assert(type >= HNDTYPE_WEAK_SHORT && type <= HNDTYPE_DEPENDENT_DEFER_FINALIZE);
return static_cast<HandleType>(type);
}

Expand Down
4 changes: 2 additions & 2 deletions src/coreclr/gc/gchandletableimpl.h
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Expand Up @@ -20,7 +20,7 @@ class GCHandleStore : public IGCHandleStore

virtual OBJECTHANDLE CreateHandleWithExtraInfo(Object* object, HandleType type, void* pExtraInfo);

virtual OBJECTHANDLE CreateDependentHandle(Object* primary, Object* secondary);
virtual OBJECTHANDLE CreateDependentHandle(HandleType type, Object* primary, Object* secondary);

virtual ~GCHandleStore();

Expand Down Expand Up @@ -61,7 +61,7 @@ class GCHandleManager : public IGCHandleManager

virtual bool StoreObjectInHandleIfNull(OBJECTHANDLE handle, Object* object);

virtual void SetDependentHandleSecondary(OBJECTHANDLE handle, Object* object);
virtual void SetDependentHandleSecondary(HandleType type, OBJECTHANDLE handle, Object* object);

virtual Object* GetDependentHandleSecondary(OBJECTHANDLE handle);

Expand Down
18 changes: 14 additions & 4 deletions src/coreclr/gc/gcinterface.h
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Expand Up @@ -6,7 +6,7 @@

// The major version of the IGCHeap interface. Breaking changes to this interface
// require bumps in the major version number.
#define GC_INTERFACE_MAJOR_VERSION 5
#define GC_INTERFACE_MAJOR_VERSION 6

// The minor version of the IGCHeap interface. Non-breaking changes are required
// to bump the minor version number. GCs and EEs with minor version number
Expand Down Expand Up @@ -502,7 +502,17 @@ typedef enum
* but we are keeping it here for backward compatibility purposes"
*
*/
HNDTYPE_WEAK_NATIVE_COM = 9
HNDTYPE_WEAK_NATIVE_COM = 9,

/*
* DEPENDENT DEFER FINIALIZE HANDLES
*
* Like HNDTYPE_DEPENDENT, but the secondary is always promoted until
* the primary is collected.
*
*
*/
HNDTYPE_DEPENDENT_DEFER_FINALIZE = 10
} HandleType;

typedef enum
Expand Down Expand Up @@ -543,7 +553,7 @@ class IGCHandleStore {

virtual OBJECTHANDLE CreateHandleWithExtraInfo(Object* object, HandleType type, void* pExtraInfo) PURE_VIRTUAL

virtual OBJECTHANDLE CreateDependentHandle(Object* primary, Object* secondary) PURE_VIRTUAL
virtual OBJECTHANDLE CreateDependentHandle(HandleType type, Object* primary, Object* secondary) PURE_VIRTUAL

virtual ~IGCHandleStore() {};
};
Expand Down Expand Up @@ -577,7 +587,7 @@ class IGCHandleManager {

virtual bool StoreObjectInHandleIfNull(OBJECTHANDLE handle, Object* object) PURE_VIRTUAL

virtual void SetDependentHandleSecondary(OBJECTHANDLE handle, Object* object) PURE_VIRTUAL
virtual void SetDependentHandleSecondary(HandleType type, OBJECTHANDLE handle, Object* object) PURE_VIRTUAL

virtual Object* GetDependentHandleSecondary(OBJECTHANDLE handle) PURE_VIRTUAL

Expand Down
2 changes: 1 addition & 1 deletion src/coreclr/gc/handletable.cpp
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Expand Up @@ -597,7 +597,7 @@ void HndWriteBarrierWorker(OBJECTHANDLE handle, _UNCHECKED_OBJECTREF value)
}
#endif

if (uType == HNDTYPE_DEPENDENT)
if (uType == HNDTYPE_DEPENDENT || uType == HNDTYPE_DEPENDENT_DEFER_FINALIZE)
{
generation = 0;
}
Expand Down
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