pythonnet/src/runtime/finalizer.cs at skip-while-initializing · Waitingtolearn/pythonnet · GitHub

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using System;

using System.Collections.Concurrent;

using System.Collections.Generic;

using System.ComponentModel;

using System.Diagnostics;

using System.Linq;

using System.Runtime.InteropServices;

using System.Threading;

using System.Threading.Tasks;

namespace Python.Runtime

{

public class Finalizer

{

public class CollectArgs : EventArgs

{

public int ObjectCount { get; set; }

}

public class ErrorArgs : EventArgs

{

public ErrorArgs(Exception error)

{

Error = error ?? throw new ArgumentNullException(nameof(error));

}

public bool Handled { get; set; }

public Exception Error { get; }

}

public static readonly Finalizer Instance = new Finalizer();

public event EventHandler<CollectArgs>? BeforeCollect;

public event EventHandler<ErrorArgs>? ErrorHandler;

const int DefaultThreshold = 200;

[DefaultValue(DefaultThreshold)]

public int Threshold { get; set; } = DefaultThreshold;

bool started;

[DefaultValue(true)]

public bool Enable { get; set; } = true;

private ConcurrentQueue<PendingFinalization> _objQueue = new();

private readonly ConcurrentQueue<PendingFinalization> _derivedQueue = new();

private int _throttled;

#region FINALIZER_CHECK

#if FINALIZER_CHECK

private readonly object _queueLock = new object();

internal bool RefCountValidationEnabled { get; set; } = true;

#else

internal bool RefCountValidationEnabled { get; set; } = false;

#endif

// Keep these declarations for compat even no FINALIZER_CHECK

internal class IncorrectFinalizeArgs : EventArgs

{

public IncorrectFinalizeArgs(IntPtr handle, IReadOnlyCollection<IntPtr> imacted)

{

Handle = handle;

ImpactedObjects = imacted;

}

public IntPtr Handle { get; }

public BorrowedReference Reference => new(Handle);

public IReadOnlyCollection<IntPtr> ImpactedObjects { get; }

}

internal class IncorrectRefCountException : Exception

{

public IntPtr PyPtr { get; internal set; }

string? message;

public override string Message

{

get

{

if (message is not null) return message;

var gil = PythonEngine.AcquireLock();

try

{

using var pyname = Runtime.PyObject_Str(new BorrowedReference(PyPtr));

string name = Runtime.GetManagedString(pyname.BorrowOrThrow()) ?? Util.BadStr;

message = $"<{name}> may has a incorrect ref count";

}

finally

{

PythonEngine.ReleaseLock(gil);

}

return message;

}

internal IncorrectRefCountException(IntPtr ptr)

{

PyPtr = ptr;

}

internal delegate bool IncorrectRefCntHandler(object sender, IncorrectFinalizeArgs e);

#pragma warning disable 414

internal event IncorrectRefCntHandler? IncorrectRefCntResolver = null;

#pragma warning restore 414

internal bool ThrowIfUnhandleIncorrectRefCount { get; set; } = true;

#endregion

public void Collect() => this.DisposeAll();

internal void ThrottledCollect()

{

if (!started) throw new InvalidOperationException($"{nameof(PythonEngine)} is not initialized");

_throttled = unchecked(this._throttled + 1);

if (!started || !Enable || _throttled < Threshold) return;

_throttled = 0;

this.Collect();

}

internal List<IntPtr> GetCollectedObjects()

{

return _objQueue.Select(o => o.PyObj).ToList();

}

internal void AddFinalizedObject(ref IntPtr obj, int run

#if TRACE_ALLOC

, StackTrace stackTrace

#endif

)

{

Debug.Assert(obj != IntPtr.Zero);

if (!Enable)

{

return;

}

Debug.Assert(Runtime.Refcount(new BorrowedReference(obj)) > 0);

#if FINALIZER_CHECK

lock (_queueLock)

#endif

{

this._objQueue.Enqueue(new PendingFinalization {

PyObj = obj, RuntimeRun = run,

#if TRACE_ALLOC

StackTrace = stackTrace.ToString(),

#endif

});

}

obj = IntPtr.Zero;

}

internal void AddDerivedFinalizedObject(ref IntPtr derived, int run)

{

if (derived == IntPtr.Zero)

throw new ArgumentNullException(nameof(derived));

if (!Enable)

{

return;

}

var pending = new PendingFinalization { PyObj = derived, RuntimeRun = run };

derived = IntPtr.Zero;

_derivedQueue.Enqueue(pending);

}

internal static void Initialize()

{

Instance.started = true;

}

internal static void Shutdown()

{

Instance.DisposeAll();

Instance.started = false;

}

internal nint DisposeAll()

{

if (_objQueue.IsEmpty && _derivedQueue.IsEmpty)

return 0;

nint collected = 0;

BeforeCollect?.Invoke(this, new CollectArgs()

{

ObjectCount = _objQueue.Count

});

#if FINALIZER_CHECK

lock (_queueLock)

#endif

{

#if FINALIZER_CHECK

ValidateRefCount();

#endif

Runtime.PyErr_Fetch(out var errType, out var errVal, out var traceback);

Debug.Assert(errType.IsNull());

int run = Runtime.GetRun();

try

{

while (!_objQueue.IsEmpty)

{

if (!_objQueue.TryDequeue(out var obj))

continue;

if (obj.RuntimeRun != run)

{

HandleFinalizationException(obj.PyObj, new RuntimeShutdownException(obj.PyObj));

continue;

}

IntPtr copyForException = obj.PyObj;

Runtime.XDecref(StolenReference.Take(ref obj.PyObj));

collected++;

try

{

Runtime.CheckExceptionOccurred();

}

catch (Exception e)

{

HandleFinalizationException(obj.PyObj, e);

}

while (!_derivedQueue.IsEmpty)

{

if (!_derivedQueue.TryDequeue(out var derived))

continue;

if (derived.RuntimeRun != run)

{

HandleFinalizationException(derived.PyObj, new RuntimeShutdownException(derived.PyObj));

continue;

}

#pragma warning disable CS0618 // Type or member is obsolete. OK for internal use

PythonDerivedType.Finalize(derived.PyObj);

#pragma warning restore CS0618 // Type or member is obsolete

collected++;

}

finally

{

// Python requires finalizers to preserve exception:

// https://docs.python.org/3/extending/newtypes.html#finalization-and-de-allocation

Runtime.PyErr_Restore(errType.StealNullable(), errVal.StealNullable(), traceback.StealNullable());

}

return collected;

}

void HandleFinalizationException(IntPtr obj, Exception cause)

{

var errorArgs = new ErrorArgs(cause);

ErrorHandler?.Invoke(this, errorArgs);

if (!errorArgs.Handled)

{

throw new FinalizationException(

"Python object finalization failed",

disposable: obj, innerException: cause);

}

#if FINALIZER_CHECK

private void ValidateRefCount()

{

if (!RefCountValidationEnabled)

{

return;

}

var counter = new Dictionary<IntPtr, long>();

var holdRefs = new Dictionary<IntPtr, long>();

var indexer = new Dictionary<IntPtr, List<IntPtr>>();

foreach (var obj in _objQueue)

{

var handle = obj;

if (!counter.ContainsKey(handle))

{

counter[handle] = 0;

}

counter[handle]++;

if (!holdRefs.ContainsKey(handle))

{

holdRefs[handle] = Runtime.Refcount(handle);

}

List<IntPtr> objs;

if (!indexer.TryGetValue(handle, out objs))

{

objs = new List<IntPtr>();

indexer.Add(handle, objs);

}

objs.Add(obj);

}

foreach (var pair in counter)

{

IntPtr handle = pair.Key;

long cnt = pair.Value;

// Tracked handle's ref count is larger than the object's holds

// it may take an unspecified behaviour if it decref in Dispose

if (cnt > holdRefs[handle])

{

var args = new IncorrectFinalizeArgs()

{

Handle = handle,

ImpactedObjects = indexer[handle]

};

bool handled = false;

if (IncorrectRefCntResolver != null)

{

var funcList = IncorrectRefCntResolver.GetInvocationList();

foreach (IncorrectRefCntHandler func in funcList)

{

if (func(this, args))

{

handled = true;

break;

}

if (!handled && ThrowIfUnhandleIncorrectRefCount)

{

throw new IncorrectRefCountException(handle);

}

// Make sure no other references for PyObjects after this method

indexer[handle].Clear();

}

indexer.Clear();

}

#endif

}

struct PendingFinalization

{

public IntPtr PyObj;

public BorrowedReference Ref => new(PyObj);

public int RuntimeRun;

#if TRACE_ALLOC

public string StackTrace;

#endif

}

public class FinalizationException : Exception

{

public IntPtr Handle { get; }

/// <summary>

/// Gets the object, whose finalization failed.

///

/// <para>If this function crashes, you can also try <see cref="DebugGetObject"/>,

/// which does not attempt to increase the object reference count.</para>

/// </summary>

public PyObject GetObject() => new(new BorrowedReference(this.Handle));

/// <summary>

/// Gets the object, whose finalization failed without incrementing

/// its reference count. This should only ever be called during debugging.

/// When the result is disposed or finalized, the program will crash.

/// </summary>

public PyObject DebugGetObject()

{

IntPtr dangerousNoIncRefCopy = this.Handle;

return new(StolenReference.Take(ref dangerousNoIncRefCopy));

}

public FinalizationException(string message, IntPtr disposable, Exception innerException)

: base(message, innerException)

{

if (disposable == IntPtr.Zero) throw new ArgumentNullException(nameof(disposable));

this.Handle = disposable;

}

protected FinalizationException(string message, IntPtr disposable)

: base(message)

{

if (disposable == IntPtr.Zero) throw new ArgumentNullException(nameof(disposable));

this.Handle = disposable;

}

public class RuntimeShutdownException : FinalizationException

{

public RuntimeShutdownException(IntPtr disposable)

: base("Python runtime was shut down after this object was created." +

" It is an error to attempt to dispose or to continue using it even after restarting the runtime.", disposable)

{

}

pythonnet/src/runtime/finalizer.cs at skip-while-initializing · Waitingtolearn/pythonnet · GitHub

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