lwlock.h

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/*-------------------------------------------------------------------------
 *
 * lwlock.h
 *    Lightweight lock manager
 *
 *
 * Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/storage/lwlock.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef LWLOCK_H
#define LWLOCK_H

/*
 * It's a bit odd to declare NUM_BUFFER_PARTITIONS and NUM_LOCK_PARTITIONS
 * here, but we need them to set up enum LWLockId correctly, and having
 * this file include lock.h or bufmgr.h would be backwards.
 */

/* Number of partitions of the shared buffer mapping hashtable */
#define NUM_BUFFER_PARTITIONS  16

/* Number of partitions the shared lock tables are divided into */
#define LOG2_NUM_LOCK_PARTITIONS  4
#define NUM_LOCK_PARTITIONS  (1 << LOG2_NUM_LOCK_PARTITIONS)

/* Number of partitions the shared predicate lock tables are divided into */
#define LOG2_NUM_PREDICATELOCK_PARTITIONS  4
#define NUM_PREDICATELOCK_PARTITIONS  (1 << LOG2_NUM_PREDICATELOCK_PARTITIONS)

/*
 * We have a number of predefined LWLocks, plus a bunch of LWLocks that are
 * dynamically assigned (e.g., 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 ...
 *
 * If you remove a lock, please replace it with a placeholder. This retains
 * the lock numbering, which is helpful for DTrace and other external
 * debugging scripts.
 */
typedef enum LWLockId
{
    BufFreelistLock,
    ShmemIndexLock,
    OidGenLock,
    XidGenLock,
    ProcArrayLock,
    SInvalReadLock,
    SInvalWriteLock,
    WALInsertLock,
    WALWriteLock,
    ControlFileLock,
    CheckpointLock,
    CLogControlLock,
    SubtransControlLock,
    MultiXactGenLock,
    MultiXactOffsetControlLock,
    MultiXactMemberControlLock,
    RelCacheInitLock,
    CheckpointerCommLock,
    TwoPhaseStateLock,
    TablespaceCreateLock,
    BtreeVacuumLock,
    AddinShmemInitLock,
    AutovacuumLock,
    AutovacuumScheduleLock,
    SyncScanLock,
    RelationMappingLock,
    AsyncCtlLock,
    AsyncQueueLock,
    SerializableXactHashLock,
    SerializableFinishedListLock,
    SerializablePredicateLockListLock,
    OldSerXidLock,
    SyncRepLock,
    /* Individual lock IDs end here */
    FirstBufMappingLock,
    FirstLockMgrLock = FirstBufMappingLock + NUM_BUFFER_PARTITIONS,
    FirstPredicateLockMgrLock = FirstLockMgrLock + NUM_LOCK_PARTITIONS,

    /* must be last except for MaxDynamicLWLock: */
    NumFixedLWLocks = FirstPredicateLockMgrLock + NUM_PREDICATELOCK_PARTITIONS,

    MaxDynamicLWLock = 1000000000
} LWLockId;


typedef enum LWLockMode
{
    LW_EXCLUSIVE,
    LW_SHARED,
    LW_WAIT_UNTIL_FREE          /* A special mode used in PGPROC->lwlockMode,
                                 * when waiting for lock to become free. Not
                                 * to be used as LWLockAcquire argument */
} 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 bool LWLockAcquireOrWait(LWLockId lockid, LWLockMode mode);
extern void LWLockRelease(LWLockId lockid);
extern void LWLockReleaseAll(void);
extern bool LWLockHeldByMe(LWLockId lockid);

extern int  NumLWLocks(void);
extern Size LWLockShmemSize(void);
extern void CreateLWLocks(void);

extern void RequestAddinLWLocks(int n);

#endif   /* LWLOCK_H */