lmgr.c

postgresql8.3.4源码,开源数据库

/*-------------------------------------------------------------------------
 *
 * lmgr.c
 *	  POSTGRES lock manager code
 *
 * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $PostgreSQL: pgsql/src/backend/storage/lmgr/lmgr.c,v 1.96.2.1 2008/03/04 19:54:13 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include "access/subtrans.h"
#include "access/transam.h"
#include "access/xact.h"
#include "catalog/catalog.h"
#include "miscadmin.h"
#include "storage/lmgr.h"
#include "storage/procarray.h"
#include "utils/inval.h"


/*
 * RelationInitLockInfo
 *		Initializes the lock information in a relation descriptor.
 *
 *		relcache.c must call this during creation of any reldesc.
 */
void
RelationInitLockInfo(Relation relation)
{
	Assert(RelationIsValid(relation));
	Assert(OidIsValid(RelationGetRelid(relation)));

	relation->rd_lockInfo.lockRelId.relId = RelationGetRelid(relation);

	if (relation->rd_rel->relisshared)
		relation->rd_lockInfo.lockRelId.dbId = InvalidOid;
	else
		relation->rd_lockInfo.lockRelId.dbId = MyDatabaseId;
}

/*
 * SetLocktagRelationOid
 *		Set up a locktag for a relation, given only relation OID
 */
static inline void
SetLocktagRelationOid(LOCKTAG *tag, Oid relid)
{
	Oid			dbid;

	if (IsSharedRelation(relid))
		dbid = InvalidOid;
	else
		dbid = MyDatabaseId;

	SET_LOCKTAG_RELATION(*tag, dbid, relid);
}

/*
 *		LockRelationOid
 *
 * Lock a relation given only its OID.	This should generally be used
 * before attempting to open the relation's relcache entry.
 */
void
LockRelationOid(Oid relid, LOCKMODE lockmode)
{
	LOCKTAG		tag;
	LockAcquireResult res;

	SetLocktagRelationOid(&tag, relid);

	res = LockAcquire(&tag, lockmode, false, false);

	/*
	 * Now that we have the lock, check for invalidation messages, so that we
	 * will update or flush any stale relcache entry before we try to use it.
	 * We can skip this in the not-uncommon case that we already had the same
	 * type of lock being requested, since then no one else could have
	 * modified the relcache entry in an undesirable way.  (In the case where
	 * our own xact modifies the rel, the relcache update happens via
	 * CommandCounterIncrement, not here.)
	 */
	if (res != LOCKACQUIRE_ALREADY_HELD)
		AcceptInvalidationMessages();
}

/*
 *		ConditionalLockRelationOid
 *
 * As above, but only lock if we can get the lock without blocking.
 * Returns TRUE iff the lock was acquired.
 *
 * NOTE: we do not currently need conditional versions of all the
 * LockXXX routines in this file, but they could easily be added if needed.
 */
bool
ConditionalLockRelationOid(Oid relid, LOCKMODE lockmode)
{
	LOCKTAG		tag;
	LockAcquireResult res;

	SetLocktagRelationOid(&tag, relid);

	res = LockAcquire(&tag, lockmode, false, true);

	if (res == LOCKACQUIRE_NOT_AVAIL)
		return false;

	/*
	 * Now that we have the lock, check for invalidation messages; see notes
	 * in LockRelationOid.
	 */
	if (res != LOCKACQUIRE_ALREADY_HELD)
		AcceptInvalidationMessages();

	return true;
}

/*
 *		UnlockRelationId
 *
 * Unlock, given a LockRelId.  This is preferred over UnlockRelationOid
 * for speed reasons.
 */
void
UnlockRelationId(LockRelId *relid, LOCKMODE lockmode)
{
	LOCKTAG		tag;

	SET_LOCKTAG_RELATION(tag, relid->dbId, relid->relId);

	LockRelease(&tag, lockmode, false);
}

/*
 *		UnlockRelationOid
 *
 * Unlock, given only a relation Oid.  Use UnlockRelationId if you can.
 */
void
UnlockRelationOid(Oid relid, LOCKMODE lockmode)
{
	LOCKTAG		tag;

	SetLocktagRelationOid(&tag, relid);

	LockRelease(&tag, lockmode, false);
}

/*
 *		LockRelation
 *
 * This is a convenience routine for acquiring an additional lock on an
 * already-open relation.  Never try to do "relation_open(foo, NoLock)"
 * and then lock with this.
 */
void
LockRelation(Relation relation, LOCKMODE lockmode)
{
	LOCKTAG		tag;
	LockAcquireResult res;

	SET_LOCKTAG_RELATION(tag,
						 relation->rd_lockInfo.lockRelId.dbId,
						 relation->rd_lockInfo.lockRelId.relId);

	res = LockAcquire(&tag, lockmode, false, false);

	/*
	 * Now that we have the lock, check for invalidation messages; see notes
	 * in LockRelationOid.
	 */
	if (res != LOCKACQUIRE_ALREADY_HELD)
		AcceptInvalidationMessages();
}

/*
 *		ConditionalLockRelation
 *
 * This is a convenience routine for acquiring an additional lock on an
 * already-open relation.  Never try to do "relation_open(foo, NoLock)"
 * and then lock with this.
 */
bool
ConditionalLockRelation(Relation relation, LOCKMODE lockmode)
{
	LOCKTAG		tag;
	LockAcquireResult res;

	SET_LOCKTAG_RELATION(tag,
						 relation->rd_lockInfo.lockRelId.dbId,
						 relation->rd_lockInfo.lockRelId.relId);

	res = LockAcquire(&tag, lockmode, false, true);

	if (res == LOCKACQUIRE_NOT_AVAIL)
		return false;

	/*
	 * Now that we have the lock, check for invalidation messages; see notes
	 * in LockRelationOid.
	 */
	if (res != LOCKACQUIRE_ALREADY_HELD)
		AcceptInvalidationMessages();

	return true;
}

/*
 *		UnlockRelation
 *
 * This is a convenience routine for unlocking a relation without also
 * closing it.
 */
void
UnlockRelation(Relation relation, LOCKMODE lockmode)
{
	LOCKTAG		tag;

	SET_LOCKTAG_RELATION(tag,
						 relation->rd_lockInfo.lockRelId.dbId,
						 relation->rd_lockInfo.lockRelId.relId);

	LockRelease(&tag, lockmode, false);
}

/*
 *		LockRelationIdForSession
 *
 * This routine grabs a session-level lock on the target relation.	The
 * session lock persists across transaction boundaries.  It will be removed
 * when UnlockRelationIdForSession() is called, or if an ereport(ERROR) occurs,
 * or if the backend exits.
 *
 * Note that one should also grab a transaction-level lock on the rel
 * in any transaction that actually uses the rel, to ensure that the
 * relcache entry is up to date.
 */
void
LockRelationIdForSession(LockRelId *relid, LOCKMODE lockmode)
{
	LOCKTAG		tag;

	SET_LOCKTAG_RELATION(tag, relid->dbId, relid->relId);

	(void) LockAcquire(&tag, lockmode, true, false);
}

/*
 *		UnlockRelationIdForSession
 */
void
UnlockRelationIdForSession(LockRelId *relid, LOCKMODE lockmode)
{
	LOCKTAG		tag;

	SET_LOCKTAG_RELATION(tag, relid->dbId, relid->relId);

	LockRelease(&tag, lockmode, true);
}

/*
 *		LockRelationForExtension
 *
 * This lock tag is used to interlock addition of pages to relations.
 * We need such locking because bufmgr/smgr definition of P_NEW is not
 * race-condition-proof.
 *
 * We assume the caller is already holding some type of regular lock on
 * the relation, so no AcceptInvalidationMessages call is needed here.
 */
void
LockRelationForExtension(Relation relation, LOCKMODE lockmode)
{
	LOCKTAG		tag;

	SET_LOCKTAG_RELATION_EXTEND(tag,
								relation->rd_lockInfo.lockRelId.dbId,
								relation->rd_lockInfo.lockRelId.relId);

	(void) LockAcquire(&tag, lockmode, false, false);
}

/*
 *		UnlockRelationForExtension
 */
void
UnlockRelationForExtension(Relation relation, LOCKMODE lockmode)
{
	LOCKTAG		tag;

	SET_LOCKTAG_RELATION_EXTEND(tag,
								relation->rd_lockInfo.lockRelId.dbId,
								relation->rd_lockInfo.lockRelId.relId);

	LockRelease(&tag, lockmode, false);
}

/*
 *		LockPage
 *
 * Obtain a page-level lock.  This is currently used by some index access
 * methods to lock individual index pages.
 */
void
LockPage(Relation relation, BlockNumber blkno, LOCKMODE lockmode)
{
	LOCKTAG		tag;

	SET_LOCKTAG_PAGE(tag,
					 relation->rd_lockInfo.lockRelId.dbId,
					 relation->rd_lockInfo.lockRelId.relId,
					 blkno);

	(void) LockAcquire(&tag, lockmode, false, false);
}

/*
 *		ConditionalLockPage
 *
 * As above, but only lock if we can get the lock without blocking.
 * Returns TRUE iff the lock was acquired.
 */
bool
ConditionalLockPage(Relation relation, BlockNumber blkno, LOCKMODE lockmode)
{
	LOCKTAG		tag;

	SET_LOCKTAG_PAGE(tag,
					 relation->rd_lockInfo.lockRelId.dbId,
					 relation->rd_lockInfo.lockRelId.relId,
					 blkno);

	return (LockAcquire(&tag, lockmode, false, true) != LOCKACQUIRE_NOT_AVAIL);
}

/*
 *		UnlockPage
 */
void
UnlockPage(Relation relation, BlockNumber blkno, LOCKMODE lockmode)
{
	LOCKTAG		tag;

	SET_LOCKTAG_PAGE(tag,
					 relation->rd_lockInfo.lockRelId.dbId,
					 relation->rd_lockInfo.lockRelId.relId,
					 blkno);

	LockRelease(&tag, lockmode, false);
}

/*
 *		LockTuple
 *
 * Obtain a tuple-level lock.  This is used in a less-than-intuitive fashion
 * because we can't afford to keep a separate lock in shared memory for every
 * tuple.  See heap_lock_tuple before using this!
 */
void
LockTuple(Relation relation, ItemPointer tid, LOCKMODE lockmode)
{
	LOCKTAG		tag;

	SET_LOCKTAG_TUPLE(tag,