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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
//
/*============================================================
**
**
**
** Purpose: Defines the lock that implements
** single-writer/multiple-reader semantics
**
**
===========================================================*/
#if FEATURE_RWLOCK
namespace System.Threading {
using System.Threading;
using System.Security.Permissions;
using System.Runtime.Remoting;
using System;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Runtime.ConstrainedExecution;
using System.Runtime.Versioning;
using System.Diagnostics.Contracts;
[ComVisible(true)]
public sealed class ReaderWriterLock: CriticalFinalizerObject
{
/*
* Constructor
*/
public ReaderWriterLock()
{
PrivateInitialize();
}
/*
* Destructor
*/
~ReaderWriterLock()
{
PrivateDestruct();
}
/*
* Property that returns TRUE if the reader lock is held
* by the current thread
*/
public bool IsReaderLockHeld {
[ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
get {
return(PrivateGetIsReaderLockHeld());
}
}
/*
* Property that returns TRUE if the writer lock is held
* by the current thread
*/
public bool IsWriterLockHeld {
[ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
get {
return(PrivateGetIsWriterLockHeld());
}
}
/*
* Property that returns the current writer sequence number.
* The caller should be a reader or writer for getting
* meaningful results
*/
public int WriterSeqNum {
get {
return(PrivateGetWriterSeqNum());
}
}
/*
* Acquires reader lock. The thread will block if a different
* thread has writer lock.
*/
[MethodImplAttribute(MethodImplOptions.InternalCall)]
private extern void AcquireReaderLockInternal(int millisecondsTimeout);
public void AcquireReaderLock(int millisecondsTimeout)
{
AcquireReaderLockInternal(millisecondsTimeout);
}
public void AcquireReaderLock(TimeSpan timeout)
{
long tm = (long)timeout.TotalMilliseconds;
if (tm < -1 || tm > (long) Int32.MaxValue)
throw new ArgumentOutOfRangeException(nameof(timeout), Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegOrNegative1"));
AcquireReaderLockInternal((int)tm);
}
/*
* Acquires writer lock. The thread will block if a different
* thread has reader lock. It will dead lock if this thread
* has reader lock. Use UpgardeToWriterLock when you are not
* sure if the thread has reader lock
*/
[MethodImplAttribute(MethodImplOptions.InternalCall)]
private extern void AcquireWriterLockInternal(int millisecondsTimeout);
public void AcquireWriterLock(int millisecondsTimeout)
{
AcquireWriterLockInternal(millisecondsTimeout);
}
public void AcquireWriterLock(TimeSpan timeout)
{
long tm = (long)timeout.TotalMilliseconds;
if (tm < -1 || tm > (long) Int32.MaxValue)
throw new ArgumentOutOfRangeException(nameof(timeout), Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegOrNegative1"));
AcquireWriterLockInternal((int)tm);
}
/*
* Releases reader lock.
*/
[MethodImplAttribute(MethodImplOptions.InternalCall)]
[ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
private extern void ReleaseReaderLockInternal();
[ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
public void ReleaseReaderLock()
{
ReleaseReaderLockInternal();
}
/*
* Releases writer lock.
*/
[MethodImplAttribute(MethodImplOptions.InternalCall)]
[ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
private extern void ReleaseWriterLockInternal();
[ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
public void ReleaseWriterLock()
{
ReleaseWriterLockInternal();
}
/*
* Upgardes the thread to a writer. If the thread has is a
* reader, it is possible that the reader lock was
* released before writer lock was acquired.
*/
public LockCookie UpgradeToWriterLock(int millisecondsTimeout)
{
LockCookie result = new LockCookie ();
FCallUpgradeToWriterLock (ref result, millisecondsTimeout);
return result;
}
[MethodImplAttribute(MethodImplOptions.InternalCall)]
private extern void FCallUpgradeToWriterLock(ref LockCookie result, int millisecondsTimeout);
public LockCookie UpgradeToWriterLock(TimeSpan timeout)
{
long tm = (long)timeout.TotalMilliseconds;
if (tm < -1 || tm > (long) Int32.MaxValue)
throw new ArgumentOutOfRangeException(nameof(timeout), Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegOrNegative1"));
return UpgradeToWriterLock((int)tm);
}
/*
* Restores the lock status of the thread to the one it was
* in when it called UpgradeToWriterLock.
*/
[MethodImplAttribute(MethodImplOptions.InternalCall)]
private extern void DowngradeFromWriterLockInternal(ref LockCookie lockCookie);
public void DowngradeFromWriterLock(ref LockCookie lockCookie)
{
DowngradeFromWriterLockInternal(ref lockCookie);
}
/*
* Releases the lock irrespective of the number of times the thread
* acquired the lock
*/
public LockCookie ReleaseLock()
{
LockCookie result = new LockCookie ();
FCallReleaseLock (ref result);
return result;
}
[MethodImplAttribute(MethodImplOptions.InternalCall)]
private extern void FCallReleaseLock(ref LockCookie result);
/*
* Restores the lock status of the thread to the one it was
* in when it called ReleaseLock.
*/
[MethodImplAttribute(MethodImplOptions.InternalCall)]
private extern void RestoreLockInternal(ref LockCookie lockCookie);
public void RestoreLock(ref LockCookie lockCookie)
{
RestoreLockInternal(ref lockCookie);
}
/*
* Internal helper that returns TRUE if the reader lock is held
* by the current thread
*/
[MethodImplAttribute(MethodImplOptions.InternalCall)]
[ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
private extern bool PrivateGetIsReaderLockHeld();
/*
* Internal helper that returns TRUE if the writer lock is held
* by the current thread
*/
[MethodImplAttribute(MethodImplOptions.InternalCall)]
[ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
private extern bool PrivateGetIsWriterLockHeld();
/*
* Internal helper that returns the current writer sequence
* number. The caller should be a reader or writer for getting
* meaningful results
*/
[MethodImplAttribute(MethodImplOptions.InternalCall)]
private extern int PrivateGetWriterSeqNum();
/*
* Returns true if there were intermediate writes since the
* sequence number was obtained. The caller should be
* a reader or writer for getting meaningful results
*/
[MethodImplAttribute(MethodImplOptions.InternalCall)]
public extern bool AnyWritersSince(int seqNum);
// Initialize state kept inside the lock
[MethodImplAttribute(MethodImplOptions.InternalCall)]
private extern void PrivateInitialize();
// Destruct resource associated with the lock
[MethodImplAttribute(MethodImplOptions.InternalCall)]
private extern void PrivateDestruct();
// State
#pragma warning disable 169
#pragma warning disable 414 // These fields are not used from managed.
private IntPtr _hWriterEvent;
private IntPtr _hReaderEvent;
private IntPtr _hObjectHandle;
private int _dwState = 0;
private int _dwULockID = 0;
private int _dwLLockID = 0;
private int _dwWriterID = 0;
private int _dwWriterSeqNum = 0;
private short _wWriterLevel;
#if RWLOCK_STATISTICS
// WARNING: You must explicitly #define RWLOCK_STATISTICS when you
// build in both the VM and BCL directories if you want this.
private int _dwReaderEntryCount = 0;
private int _dwReaderContentionCount = 0;
private int _dwWriterEntryCount = 0;
private int _dwWriterContentionCount = 0;
private int _dwEventsReleasedCount = 0;
#endif // RWLOCK_STATISTICS
#pragma warning restore 414
#pragma warning restore 169
}
}
#endif //FEATURE_RWLOCK
|
