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finalizer.cs
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using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Runtime.InteropServices;
using System.Threading;
namespace Python.Runtime
{
public class Finalizer
{
public class CollectArgs : EventArgs
{
public int ObjectCount { get; set; }
}
public class ErrorArgs : EventArgs
{
public Exception Error { get; set; }
}
public static readonly Finalizer Instance = new Finalizer();
public event EventHandler<CollectArgs> CollectOnce;
public event EventHandler<ErrorArgs> ErrorHandler;
public int Threshold { get; set; }
public bool Enable { get; set; }
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
struct PendingArgs
{
public bool cancelled;
}
[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
private delegate int PendingCall(IntPtr arg);
private readonly PendingCall _collectAction;
private ConcurrentQueue<IPyDisposable> _objQueue = new ConcurrentQueue<IPyDisposable>();
private bool _pending = false;
private readonly object _collectingLock = new object();
private IntPtr _pendingArgs = IntPtr.Zero;
#region FINALIZER_CHECK
#if FINALIZER_CHECK
private readonly object _queueLock = new object();
public bool RefCountValidationEnabled { get; set; } = true;
#else
public readonly bool RefCountValidationEnabled = false;
#endif
// Keep these declarations for compat even no FINALIZER_CHECK
public class IncorrectFinalizeArgs : EventArgs
{
public IntPtr Handle { get; internal set; }
public ICollection<IPyDisposable> ImpactedObjects { get; internal set; }
}
public class IncorrectRefCountException : Exception
{
public IntPtr PyPtr { get; internal set; }
private string _message;
public override string Message => _message;
public IncorrectRefCountException(IntPtr ptr)
{
PyPtr = ptr;
IntPtr pyname = Runtime.PyObject_Unicode(PyPtr);
string name = Runtime.GetManagedString(pyname);
Runtime.XDecref(pyname);
_message = $"{name} may has a incorrect ref count";
}
}
public delegate bool IncorrectRefCntHandler(object sender, IncorrectFinalizeArgs e);
public event IncorrectRefCntHandler IncorrectRefCntResolver;
public bool ThrowIfUnhandleIncorrectRefCount { get; set; } = true;
#endregion
private Finalizer()
{
Enable = true;
Threshold = 200;
_collectAction = OnPendingCollect;
}
public void CallPendingFinalizers()
{
if (Thread.CurrentThread.ManagedThreadId != Runtime.MainManagedThreadId)
{
throw new Exception("PendingCall should execute in main Python thread");
}
Runtime.Py_MakePendingCalls();
}
public void Collect()
{
using (var gilState = new Py.GILState())
{
DisposeAll();
}
}
public List<WeakReference> GetCollectedObjects()
{
return _objQueue.Select(T => new WeakReference(T)).ToList();
}
internal void AddFinalizedObject(IPyDisposable obj)
{
if (!Enable)
{
return;
}
if (Runtime.Py_IsInitialized() == 0)
{
// XXX: Memory will leak if a PyObject finalized after Python shutdown,
// for avoiding that case, user should call GC.Collect manual before shutdown.
return;
}
#if FINALIZER_CHECK
lock (_queueLock)
#endif
{
_objQueue.Enqueue(obj);
}
GC.ReRegisterForFinalize(obj);
if (!_pending && _objQueue.Count >= Threshold)
{
AddPendingCollect();
}
}
internal static void Shutdown()
{
if (Runtime.Py_IsInitialized() == 0)
{
Instance._objQueue = new ConcurrentQueue<IPyDisposable>();
return;
}
Instance.DisposeAll();
if (Thread.CurrentThread.ManagedThreadId != Runtime.MainManagedThreadId)
{
if (Instance._pendingArgs == IntPtr.Zero)
{
Instance.ResetPending();
return;
}
// Not in main thread just cancel the pending operation to avoid error in different domain
// It will make a memory leak
unsafe
{
PendingArgs* args = (PendingArgs*)Instance._pendingArgs;
args->cancelled = true;
}
Instance.ResetPending();
return;
}
Instance.CallPendingFinalizers();
}
private void AddPendingCollect()
{
if(Monitor.TryEnter(_collectingLock))
{
try
{
if (!_pending)
{
_pending = true;
var args = new PendingArgs { cancelled = false };
_pendingArgs = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(PendingArgs)));
Marshal.StructureToPtr(args, _pendingArgs, false);
IntPtr func = Marshal.GetFunctionPointerForDelegate(_collectAction);
if (Runtime.Py_AddPendingCall(func, _pendingArgs) != 0)
{
// Full queue, append next time
FreePendingArgs();
_pending = false;
}
}
}
finally
{
Monitor.Exit(_collectingLock);
}
}
}
private static int OnPendingCollect(IntPtr arg)
{
Debug.Assert(arg == Instance._pendingArgs);
try
{
unsafe
{
PendingArgs* pendingArgs = (PendingArgs*)arg;
if (pendingArgs->cancelled)
{
return 0;
}
}
Instance.DisposeAll();
}
finally
{
Instance.FreePendingArgs();
Instance.ResetPending();
}
return 0;
}
private void DisposeAll()
{
CollectOnce?.Invoke(this, new CollectArgs()
{
ObjectCount = _objQueue.Count
});
#if FINALIZER_CHECK
lock (_queueLock)
#endif
{
#if FINALIZER_CHECK
ValidateRefCount();
#endif
IPyDisposable obj;
while (_objQueue.TryDequeue(out obj))
{
try
{
obj.Dispose();
Runtime.CheckExceptionOccurred();
}
catch (Exception e)
{
// We should not bother the main thread
ErrorHandler?.Invoke(this, new ErrorArgs()
{
Error = e
});
}
}
}
}
private void FreePendingArgs()
{
if (_pendingArgs != IntPtr.Zero)
{
Marshal.FreeHGlobal(_pendingArgs);
_pendingArgs = IntPtr.Zero;
}
}
private void ResetPending()
{
lock (_collectingLock)
{
_pending = false;
}
}
#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<IPyDisposable>>();
foreach (var obj in _objQueue)
{
IntPtr[] handles = obj.GetTrackedHandles();
foreach (var handle in handles)
{
if (handle == IntPtr.Zero)
{
continue;
}
if (!counter.ContainsKey(handle))
{
counter[handle] = 0;
}
counter[handle]++;
if (!holdRefs.ContainsKey(handle))
{
holdRefs[handle] = Runtime.Refcount(handle);
}
List<IPyDisposable> objs;
if (!indexer.TryGetValue(handle, out objs))
{
objs = new List<IPyDisposable>();
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
}
}