postgresql/src/include/storage/lwlock.h

/*-------------------------------------------------------------------------
 *
 * lwlock.h
 *	  Lightweight lock manager
 *
 *
 * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * $Id: lwlock.h,v 1.2 2001/10/25 05:50:10 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */
#ifndef LWLOCK_H
#define LWLOCK_H

/*
 * We have a number of predefined LWLocks, plus a bunch of LWLocks that are
 * dynamically assigned (for shared buffers).  The LWLock structures live
 * in shared memory (since they contain shared data) and are identified by
 * values of this enumerated type.	We abuse the notion of an enum somewhat
 * by allowing values not listed in the enum declaration to be assigned.
 * The extra value MaxDynamicLWLock is there to keep the compiler from
 * deciding that the enum can be represented as char or short ...
 */
typedef enum LWLockId
{
				BufMgrLock,
				LockMgrLock,
				OidGenLock,
				XidGenLock,
				ShmemIndexLock,
				SInvalLock,
				FreeSpaceLock,
				MMCacheLock,
				WALInsertLock,
				WALWriteLock,
				ControlFileLock,
				CheckpointLock,
				CLogControlLock,

				NumFixedLWLocks,/* must be last except for
								 * MaxDynamicLWLock */

				MaxDynamicLWLock = 1000000000
} LWLockId;


typedef enum LWLockMode
{
				LW_EXCLUSIVE,
				LW_SHARED
} LWLockMode;


#ifdef LOCK_DEBUG
extern bool Trace_lwlocks;
#endif

extern LWLockId LWLockAssign(void);
extern void LWLockAcquire(LWLockId lockid, LWLockMode mode);
extern bool LWLockConditionalAcquire(LWLockId lockid, LWLockMode mode);
extern void LWLockRelease(LWLockId lockid);
extern void LWLockReleaseAll(void);

extern int	NumLWLocks(void);
extern int	LWLockShmemSize(void);
extern void CreateLWLocks(void);
#endif	 /* LWLOCK_H */