* Added ReaderWriterLockSlim.cs to OpenMetaverseTypes from the Mono SVN
* Prebuild will now define the VISUAL_STUDIO symbol in .csproj files while leaving NAnt files alone * A conditional was added to use the .NET ReaderWriterLockSlim for VS compiles and the one in OpenMetaverseTypes for Mono compiles. This is a kludge until everyone is running Mono 2.6 or later (hah) git-svn-id: http://libopenmetaverse.googlecode.com/svn/libopenmetaverse/trunk@2769 52acb1d6-8a22-11de-b505-999d5b087335
This commit is contained in:
John Hurliman
618
OpenMetaverseTypes/ReaderWriterLockSlim.cs
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618
OpenMetaverseTypes/ReaderWriterLockSlim.cs
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@@ -0,0 +1,618 @@
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//
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// System.Threading.ReaderWriterLockSlim.cs
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//
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// Authors:
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// Miguel de Icaza (miguel@novell.com)
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// Dick Porter (dick@ximian.com)
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// Jackson Harper (jackson@ximian.com)
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// Lluis Sanchez Gual (lluis@ximian.com)
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// Marek Safar (marek.safar@gmail.com)
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//
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// Copyright 2004-2008 Novell, Inc (http://www.novell.com)
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// Copyright 2003, Ximian, Inc.
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//
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// NoRecursion code based on the blog post from Vance Morrison:
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// http://blogs.msdn.com/vancem/archive/2006/03/28/563180.aspx
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//
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// Recursion code based on Mono's implementation of ReaderWriterLock.
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//
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// Permission is hereby granted, free of charge, to any person obtaining
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// a copy of this software and associated documentation files (the
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// "Software"), to deal in the Software without restriction, including
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// without limitation the rights to use, copy, modify, merge, publish,
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// distribute, sublicense, and/or sell copies of the Software, and to
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// permit persons to whom the Software is furnished to do so, subject to
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// the following conditions:
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//
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// The above copyright notice and this permission notice shall be
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// included in all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
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// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
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// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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//
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using System;
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using System.Collections;
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using System.Collections.Generic;
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using System.Security.Permissions;
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using System.Diagnostics;
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using System.Runtime.Serialization;
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using System.Threading;
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namespace OpenMetaverse
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{
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[Serializable]
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public class LockRecursionException : Exception
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{
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public LockRecursionException()
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: base()
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{
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}
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public LockRecursionException(string message)
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: base(message)
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{
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}
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public LockRecursionException(string message, Exception e)
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: base(message, e)
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{
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}
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protected LockRecursionException(SerializationInfo info, StreamingContext sc)
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: base(info, sc)
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{
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}
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}
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//
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// This implementation is based on the light-weight
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// Reader/Writer lock sample from Vance Morrison's blog:
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//
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// http://blogs.msdn.com/vancem/archive/2006/03/28/563180.aspx
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//
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// And in Mono's ReaderWriterLock
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//
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[HostProtectionAttribute(SecurityAction.LinkDemand, MayLeakOnAbort = true)]
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[HostProtectionAttribute(SecurityAction.LinkDemand, Synchronization = true, ExternalThreading = true)]
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public class ReaderWriterLockSlim : IDisposable
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{
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sealed class LockDetails
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{
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public int ThreadId;
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public int ReadLocks;
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}
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// Are we on a multiprocessor?
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static readonly bool smp;
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// Lock specifiation for myLock: This lock protects exactly the local fields associted
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// instance of MyReaderWriterLock. It does NOT protect the memory associted with the
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// the events that hang off this lock (eg writeEvent, readEvent upgradeEvent).
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int myLock;
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// Who owns the lock owners > 0 => readers
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// owners = -1 means there is one writer, Owners must be >= -1.
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int owners;
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Thread upgradable_thread;
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Thread write_thread;
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// These variables allow use to avoid Setting events (which is expensive) if we don't have to.
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uint numWriteWaiters; // maximum number of threads that can be doing a WaitOne on the writeEvent
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uint numReadWaiters; // maximum number of threads that can be doing a WaitOne on the readEvent
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uint numUpgradeWaiters; // maximum number of threads that can be doing a WaitOne on the upgradeEvent (at most 1).
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// conditions we wait on.
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EventWaitHandle writeEvent; // threads waiting to aquire a write lock go here.
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EventWaitHandle readEvent; // threads waiting to aquire a read lock go here (will be released in bulk)
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EventWaitHandle upgradeEvent; // thread waiting to upgrade a read lock to a write lock go here (at most one)
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//int lock_owner;
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// Only set if we are a recursive lock
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//Dictionary<int,int> reader_locks;
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LockDetails[] read_locks = new LockDetails[8];
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static ReaderWriterLockSlim()
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{
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smp = Environment.ProcessorCount > 1;
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}
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public ReaderWriterLockSlim()
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{
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// NoRecursion (0) is the default value
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}
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public void EnterReadLock()
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{
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TryEnterReadLock(-1);
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}
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public bool TryEnterReadLock(int millisecondsTimeout)
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{
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if (millisecondsTimeout < Timeout.Infinite)
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throw new ArgumentOutOfRangeException("millisecondsTimeout");
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if (read_locks == null)
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throw new ObjectDisposedException(null);
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if (Thread.CurrentThread == write_thread)
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throw new LockRecursionException("Read lock cannot be acquired while write lock is held");
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EnterMyLock();
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LockDetails ld = GetReadLockDetails(Thread.CurrentThread.ManagedThreadId, true);
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if (ld.ReadLocks != 0)
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{
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ExitMyLock();
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throw new LockRecursionException("Recursive read lock can only be aquired in SupportsRecursion mode");
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}
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++ld.ReadLocks;
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while (true)
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{
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// Easy case, no contention
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// owners >= 0 means there might be readers (but no writer)
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if (owners >= 0 && numWriteWaiters == 0)
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{
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owners++;
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break;
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}
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// If the request is to probe.
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if (millisecondsTimeout == 0)
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{
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ExitMyLock();
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return false;
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}
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// We need to wait. Mark that we have waiters and wait.
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if (readEvent == null)
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{
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LazyCreateEvent(ref readEvent, false);
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// since we left the lock, start over.
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continue;
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}
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if (!WaitOnEvent(readEvent, ref numReadWaiters, millisecondsTimeout))
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return false;
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}
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ExitMyLock();
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return true;
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}
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public bool TryEnterReadLock(TimeSpan timeout)
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{
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return TryEnterReadLock(CheckTimeout(timeout));
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}
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//
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// TODO: What to do if we are releasing a ReadLock and we do not own it?
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//
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public void ExitReadLock()
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{
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EnterMyLock();
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if (owners < 1)
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{
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ExitMyLock();
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throw new SynchronizationLockException("Releasing lock and no read lock taken");
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}
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--owners;
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--GetReadLockDetails(Thread.CurrentThread.ManagedThreadId, false).ReadLocks;
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ExitAndWakeUpAppropriateWaiters();
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}
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public void EnterWriteLock()
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{
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TryEnterWriteLock(-1);
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}
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public bool TryEnterWriteLock(int millisecondsTimeout)
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{
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if (millisecondsTimeout < Timeout.Infinite)
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throw new ArgumentOutOfRangeException("millisecondsTimeout");
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if (read_locks == null)
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throw new ObjectDisposedException(null);
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if (IsWriteLockHeld)
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throw new LockRecursionException();
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EnterMyLock();
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LockDetails ld = GetReadLockDetails(Thread.CurrentThread.ManagedThreadId, false);
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if (ld != null && ld.ReadLocks > 0)
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{
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ExitMyLock();
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throw new LockRecursionException("Write lock cannot be acquired while read lock is held");
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}
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while (true)
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{
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// There is no contention, we are done
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if (owners == 0)
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{
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// Indicate that we have a writer
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owners = -1;
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write_thread = Thread.CurrentThread;
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break;
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}
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// If we are the thread that took the Upgradable read lock
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if (owners == 1 && upgradable_thread == Thread.CurrentThread)
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{
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owners = -1;
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write_thread = Thread.CurrentThread;
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break;
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}
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// If the request is to probe.
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if (millisecondsTimeout == 0)
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{
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ExitMyLock();
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return false;
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}
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// We need to wait, figure out what kind of waiting.
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if (upgradable_thread == Thread.CurrentThread)
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{
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// We are the upgradable thread, register our interest.
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if (upgradeEvent == null)
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{
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LazyCreateEvent(ref upgradeEvent, false);
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// since we left the lock, start over.
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continue;
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}
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if (numUpgradeWaiters > 0)
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{
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ExitMyLock();
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throw new ApplicationException("Upgrading lock to writer lock already in process, deadlock");
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}
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if (!WaitOnEvent(upgradeEvent, ref numUpgradeWaiters, millisecondsTimeout))
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return false;
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}
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else
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{
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if (writeEvent == null)
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{
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LazyCreateEvent(ref writeEvent, true);
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// since we left the lock, retry
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continue;
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}
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if (!WaitOnEvent(writeEvent, ref numWriteWaiters, millisecondsTimeout))
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return false;
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}
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}
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Debug.Assert(owners == -1, "Owners is not -1");
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ExitMyLock();
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return true;
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}
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public bool TryEnterWriteLock(TimeSpan timeout)
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{
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return TryEnterWriteLock(CheckTimeout(timeout));
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}
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public void ExitWriteLock()
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{
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EnterMyLock();
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if (owners != -1)
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{
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ExitMyLock();
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throw new SynchronizationLockException("Calling ExitWriterLock when no write lock is held");
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}
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//Debug.Assert (numUpgradeWaiters > 0);
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write_thread = upgradable_thread = null;
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owners = 0;
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ExitAndWakeUpAppropriateWaiters();
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}
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public void EnterUpgradeableReadLock()
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{
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TryEnterUpgradeableReadLock(-1);
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}
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//
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// Taking the Upgradable read lock is like taking a read lock
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// but we limit it to a single upgradable at a time.
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//
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public bool TryEnterUpgradeableReadLock(int millisecondsTimeout)
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{
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if (millisecondsTimeout < Timeout.Infinite)
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throw new ArgumentOutOfRangeException("millisecondsTimeout");
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if (read_locks == null)
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throw new ObjectDisposedException(null);
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if (IsUpgradeableReadLockHeld)
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throw new LockRecursionException();
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if (IsWriteLockHeld)
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throw new LockRecursionException();
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EnterMyLock();
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while (true)
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{
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if (owners == 0 && numWriteWaiters == 0 && upgradable_thread == null)
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{
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owners++;
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upgradable_thread = Thread.CurrentThread;
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break;
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}
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// If the request is to probe
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if (millisecondsTimeout == 0)
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{
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ExitMyLock();
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return false;
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}
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if (readEvent == null)
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{
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LazyCreateEvent(ref readEvent, false);
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// since we left the lock, start over.
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continue;
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}
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if (!WaitOnEvent(readEvent, ref numReadWaiters, millisecondsTimeout))
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return false;
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}
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ExitMyLock();
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return true;
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}
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public bool TryEnterUpgradeableReadLock(TimeSpan timeout)
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{
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return TryEnterUpgradeableReadLock(CheckTimeout(timeout));
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}
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public void ExitUpgradeableReadLock()
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{
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EnterMyLock();
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Debug.Assert(owners > 0, "Releasing an upgradable lock, but there was no reader!");
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--owners;
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upgradable_thread = null;
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ExitAndWakeUpAppropriateWaiters();
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}
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public void Dispose()
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{
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read_locks = null;
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}
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public bool IsReadLockHeld
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{
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get { return RecursiveReadCount != 0; }
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}
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public bool IsWriteLockHeld
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{
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get { return RecursiveWriteCount != 0; }
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}
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public bool IsUpgradeableReadLockHeld
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{
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get { return RecursiveUpgradeCount != 0; }
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}
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public int CurrentReadCount
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{
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get { return owners & 0xFFFFFFF; }
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}
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public int RecursiveReadCount
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{
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get
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{
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EnterMyLock();
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LockDetails ld = GetReadLockDetails(Thread.CurrentThread.ManagedThreadId, false);
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int count = ld == null ? 0 : ld.ReadLocks;
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ExitMyLock();
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return count;
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}
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}
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public int RecursiveUpgradeCount
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{
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get { return upgradable_thread == Thread.CurrentThread ? 1 : 0; }
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}
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public int RecursiveWriteCount
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{
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get { return write_thread == Thread.CurrentThread ? 1 : 0; }
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}
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public int WaitingReadCount
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{
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get { return (int)numReadWaiters; }
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}
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public int WaitingUpgradeCount
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{
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get { return (int)numUpgradeWaiters; }
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}
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public int WaitingWriteCount
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{
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get { return (int)numWriteWaiters; }
|
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}
|
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|
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#region Private methods
|
||||
void EnterMyLock()
|
||||
{
|
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if (Interlocked.CompareExchange(ref myLock, 1, 0) != 0)
|
||||
EnterMyLockSpin();
|
||||
}
|
||||
|
||||
void EnterMyLockSpin()
|
||||
{
|
||||
|
||||
for (int i = 0; ; i++)
|
||||
{
|
||||
if (i < 3 && smp)
|
||||
Thread.SpinWait(20); // Wait a few dozen instructions to let another processor release lock.
|
||||
else
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||||
Thread.Sleep(0); // Give up my quantum.
|
||||
|
||||
if (Interlocked.CompareExchange(ref myLock, 1, 0) == 0)
|
||||
return;
|
||||
}
|
||||
}
|
||||
|
||||
void ExitMyLock()
|
||||
{
|
||||
Debug.Assert(myLock != 0, "Exiting spin lock that is not held");
|
||||
myLock = 0;
|
||||
}
|
||||
|
||||
bool MyLockHeld { get { return myLock != 0; } }
|
||||
|
||||
/// <summary>
|
||||
/// Determines the appropriate events to set, leaves the locks, and sets the events.
|
||||
/// </summary>
|
||||
private void ExitAndWakeUpAppropriateWaiters()
|
||||
{
|
||||
Debug.Assert(MyLockHeld);
|
||||
|
||||
// First a writing thread waiting on being upgraded
|
||||
if (owners == 1 && numUpgradeWaiters != 0)
|
||||
{
|
||||
// Exit before signaling to improve efficiency (wakee will need the lock)
|
||||
ExitMyLock();
|
||||
// release all upgraders (however there can be at most one).
|
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upgradeEvent.Set();
|
||||
//
|
||||
// TODO: What does the following comment mean?
|
||||
// two threads upgrading is a guarenteed deadlock, so we throw in that case.
|
||||
}
|
||||
else if (owners == 0 && numWriteWaiters > 0)
|
||||
{
|
||||
// Exit before signaling to improve efficiency (wakee will need the lock)
|
||||
ExitMyLock();
|
||||
// release one writer.
|
||||
writeEvent.Set();
|
||||
}
|
||||
else if (owners >= 0 && numReadWaiters != 0)
|
||||
{
|
||||
// Exit before signaling to improve efficiency (wakee will need the lock)
|
||||
ExitMyLock();
|
||||
// release all readers.
|
||||
readEvent.Set();
|
||||
}
|
||||
else
|
||||
ExitMyLock();
|
||||
}
|
||||
|
||||
/// <summary>
|
||||
/// A routine for lazily creating a event outside the lock (so if errors
|
||||
/// happen they are outside the lock and that we don't do much work
|
||||
/// while holding a spin lock). If all goes well, reenter the lock and
|
||||
/// set 'waitEvent'
|
||||
/// </summary>
|
||||
void LazyCreateEvent(ref EventWaitHandle waitEvent, bool makeAutoResetEvent)
|
||||
{
|
||||
Debug.Assert(MyLockHeld);
|
||||
Debug.Assert(waitEvent == null);
|
||||
|
||||
ExitMyLock();
|
||||
EventWaitHandle newEvent;
|
||||
if (makeAutoResetEvent)
|
||||
newEvent = new AutoResetEvent(false);
|
||||
else
|
||||
newEvent = new ManualResetEvent(false);
|
||||
|
||||
EnterMyLock();
|
||||
|
||||
// maybe someone snuck in.
|
||||
if (waitEvent == null)
|
||||
waitEvent = newEvent;
|
||||
}
|
||||
|
||||
/// <summary>
|
||||
/// Waits on 'waitEvent' with a timeout of 'millisceondsTimeout.
|
||||
/// Before the wait 'numWaiters' is incremented and is restored before leaving this routine.
|
||||
/// </summary>
|
||||
bool WaitOnEvent(EventWaitHandle waitEvent, ref uint numWaiters, int millisecondsTimeout)
|
||||
{
|
||||
Debug.Assert(MyLockHeld);
|
||||
|
||||
waitEvent.Reset();
|
||||
numWaiters++;
|
||||
|
||||
bool waitSuccessful = false;
|
||||
|
||||
// Do the wait outside of any lock
|
||||
ExitMyLock();
|
||||
try
|
||||
{
|
||||
waitSuccessful = waitEvent.WaitOne(millisecondsTimeout, false);
|
||||
}
|
||||
finally
|
||||
{
|
||||
EnterMyLock();
|
||||
--numWaiters;
|
||||
if (!waitSuccessful)
|
||||
ExitMyLock();
|
||||
}
|
||||
return waitSuccessful;
|
||||
}
|
||||
|
||||
static int CheckTimeout(TimeSpan timeout)
|
||||
{
|
||||
try
|
||||
{
|
||||
return checked((int)timeout.TotalMilliseconds);
|
||||
}
|
||||
catch (System.OverflowException)
|
||||
{
|
||||
throw new ArgumentOutOfRangeException("timeout");
|
||||
}
|
||||
}
|
||||
|
||||
LockDetails GetReadLockDetails(int threadId, bool create)
|
||||
{
|
||||
int i;
|
||||
LockDetails ld;
|
||||
for (i = 0; i < read_locks.Length; ++i)
|
||||
{
|
||||
ld = read_locks[i];
|
||||
if (ld == null)
|
||||
break;
|
||||
|
||||
if (ld.ThreadId == threadId)
|
||||
return ld;
|
||||
}
|
||||
|
||||
if (!create)
|
||||
return null;
|
||||
|
||||
if (i == read_locks.Length)
|
||||
Array.Resize(ref read_locks, read_locks.Length * 2);
|
||||
|
||||
ld = read_locks[i] = new LockDetails();
|
||||
ld.ThreadId = threadId;
|
||||
return ld;
|
||||
}
|
||||
#endregion
|
||||
}
|
||||
}
|
||||
Reference in New Issue
Block a user