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Fixes lock recursion bug in assembly loading #628

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Merged
merged 1 commit into from
Feb 26, 2018
Merged

Fixes lock recursion bug in assembly loading #628

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1 change: 1 addition & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -29,6 +29,7 @@ This document follows the conventions laid out in [Keep a CHANGELOG][].
- Fixed 'clrmethod' for python 2 (#492)
- Fixed double calling of constructor when deriving from .NET class (#495)
- Fixed `clr.GetClrType` when iterating over `System` members (#607)
- Fixed `LockRecursionException` when loading assemblies (#627)


## [2.3.0][] - 2017-03-11
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106 changes: 4 additions & 102 deletions src/runtime/assemblymanager.cs
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Expand Up @@ -26,7 +26,7 @@ internal class AssemblyManager
private static Dictionary<string, int> probed;

// modified from event handlers below, potentially triggered from different .NET threads
private static AssemblyList assemblies;
private static ConcurrentQueue<Assembly> assemblies;
internal static List<string> pypath;

private AssemblyManager()
Expand All @@ -43,7 +43,7 @@ internal static void Initialize()
namespaces = new ConcurrentDictionary<string, ConcurrentDictionary<Assembly, string>>();
probed = new Dictionary<string, int>(32);
//generics = new Dictionary<string, Dictionary<string, string>>();
assemblies = new AssemblyList(16);
assemblies = new ConcurrentQueue<Assembly>();
pypath = new List<string>(16);

AppDomain domain = AppDomain.CurrentDomain;
Expand All @@ -60,7 +60,7 @@ internal static void Initialize()
try
{
ScanAssembly(a);
assemblies.Add(a);
assemblies.Enqueue(a);
}
catch (Exception ex)
{
Expand Down Expand Up @@ -91,7 +91,7 @@ internal static void Shutdown()
private static void AssemblyLoadHandler(object ob, AssemblyLoadEventArgs args)
{
Assembly assembly = args.LoadedAssembly;
assemblies.Add(assembly);
assemblies.Enqueue(assembly);
ScanAssembly(assembly);
}

Expand Down Expand Up @@ -461,103 +461,5 @@ public static Type LookupType(string qname)
}
return null;
}

/// <summary>
/// Wrapper around List&lt;Assembly&gt; for thread safe access
/// </summary>
private class AssemblyList : IEnumerable<Assembly>
{
private readonly List<Assembly> _list;
private readonly ReaderWriterLockSlim _lock;

public AssemblyList(int capacity)
{
_list = new List<Assembly>(capacity);
_lock = new ReaderWriterLockSlim();
}

public int Count
{
get
{
_lock.EnterReadLock();
try
{
return _list.Count;
}
finally
{
_lock.ExitReadLock();
}
}
}

public void Add(Assembly assembly)
{
_lock.EnterWriteLock();
try
{
_list.Add(assembly);
}
finally
{
_lock.ExitWriteLock();
}
}

public IEnumerator GetEnumerator()
{
return ((IEnumerable<Assembly>)this).GetEnumerator();
}

/// <summary>
/// Enumerator wrapping around <see cref="AssemblyList._list" />'s enumerator.
/// Acquires and releases a read lock on <see cref="AssemblyList._lock" /> during enumeration
/// </summary>
private class Enumerator : IEnumerator<Assembly>
{
private readonly AssemblyList _assemblyList;

private readonly IEnumerator<Assembly> _listEnumerator;

public Enumerator(AssemblyList assemblyList)
{
_assemblyList = assemblyList;
_assemblyList._lock.EnterReadLock();
_listEnumerator = _assemblyList._list.GetEnumerator();
}

public void Dispose()
{
_listEnumerator.Dispose();
_assemblyList._lock.ExitReadLock();
}

public bool MoveNext()
{
return _listEnumerator.MoveNext();
}

public void Reset()
{
_listEnumerator.Reset();
}

public Assembly Current
{
get { return _listEnumerator.Current; }
}

object IEnumerator.Current
{
get { return Current; }
}
}

IEnumerator<Assembly> IEnumerable<Assembly>.GetEnumerator()
{
return new Enumerator(this);
}
}
}
}
6 changes: 6 additions & 0 deletions src/tests/test_module.py
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Expand Up @@ -387,3 +387,9 @@ def test_assembly_load_thread_safety():
from System.Collections.Generic import Dictionary
_ = Dictionary[Guid, DateTime]()
ModuleTest.JoinThreads()

def test_assembly_load_recursion_bug():
"""Test fix for recursion bug documented in #627"""
from System.Configuration import ConfigurationManager
content = dir(ConfigurationManager)
assert len(content) > 5, content