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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.
//
//
//+-------------------------------------------------------------------
//
// File: RWLock.h
//
// Contents: Reader writer lock implementation that supports the
// following features
// 1. Cheap enough to be used in large numbers
// such as per object synchronization.
// 2. Supports timeout. This is a valuable feature
// to detect deadlocks
// 3. Supports caching of events. The allows
// the events to be moved from least contentious
// regions to the most contentious regions.
// In other words, the number of events needed by
// Reader-Writer lockls is bounded by the number
// of threads in the process.
// 4. Supports nested locks by readers and writers
// 5. Supports spin counts for avoiding context switches
// on multi processor machines.
// 6. Supports functionality for upgrading to a writer
// lock with a return argument that indicates
// intermediate writes. Downgrading from a writer
// lock restores the state of the lock.
// 7. Supports functionality to Release Lock for calling
// app code. RestoreLock restores the lock state and
// indicates intermediate writes.
// 8. Recovers from most common failures such as creation of
// events. In other words, the lock mainitains consistent
// internal state and remains usable
//
// Classes: CRWLock,
// CStaticRWLock
//
//--------------------------------------------------------------------
#ifdef FEATURE_RWLOCK
#ifndef _RWLOCK_H_
#define _RWLOCK_H_
#include "common.h"
#include "threads.h"
// If you do define this, make sure you define this in managed as well.
//#define RWLOCK_STATISTICS 0
extern DWORD gdwDefaultTimeout;
extern DWORD gdwDefaultSpinCount;
//+-------------------------------------------------------------------
//
// Struct: LockCookie
//
// Synopsis: Lock cookies returned to the client
//
//+-------------------------------------------------------------------
typedef struct {
DWORD dwFlags;
DWORD dwWriterSeqNum;
WORD wReaderLevel;
WORD wWriterLevel;
DWORD dwThreadID;
} LockCookie;
#endif // _RWLOCK_H_
#endif // FEATURE_RWLOCK
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