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Add support to lock manager for conditionally locking a lock (ie,

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return without waiting if we can't get the lock immediately).
Not used yet, but will be needed for concurrent VACUUM.
This commit is contained in:
Tom Lane
2001-06-22 00:04:59 +00:00
parent 986915c181
commit d8d9ed931e
6 changed files with 112 additions and 86 deletions
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85
src/backend/storage/lmgr/lmgr.c
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@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/storage/lmgr/lmgr.c,v 1.47 2001/06/19 19:42:16 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/storage/lmgr/lmgr.c,v 1.48 2001/06/22 00:04:59 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -24,45 +24,52 @@
static LOCKMASK LockConflicts[] = {
(int) NULL,
0,
/* AccessShareLock */
/* AccessShareLock */
(1 << AccessExclusiveLock),
/* RowShareLock */
/* RowShareLock */
(1 << ExclusiveLock) | (1 << AccessExclusiveLock),
/* RowExclusiveLock */
/* RowExclusiveLock */
(1 << ExclusiveLock) | (1 << ShareRowExclusiveLock) | (1 << ShareLock) |
(1 << AccessExclusiveLock),
/* ShareLock */
/* ShareLock */
(1 << ExclusiveLock) | (1 << ShareRowExclusiveLock) |
(1 << RowExclusiveLock) | (1 << AccessExclusiveLock),
/* ShareRowExclusiveLock */
/* ShareRowExclusiveLock */
(1 << ExclusiveLock) | (1 << ShareRowExclusiveLock) |
(1 << ShareLock) | (1 << RowExclusiveLock) | (1 << AccessExclusiveLock),
/* ExclusiveLock */
/* ExclusiveLock */
(1 << ExclusiveLock) | (1 << ShareRowExclusiveLock) | (1 << ShareLock) |
(1 << RowExclusiveLock) | (1 << RowShareLock) | (1 << AccessExclusiveLock),
/* AccessExclusiveLock */
/* AccessExclusiveLock */
(1 << ExclusiveLock) | (1 << ShareRowExclusiveLock) | (1 << ShareLock) |
(1 << RowExclusiveLock) | (1 << RowShareLock) | (1 << AccessExclusiveLock) |
(1 << AccessShareLock),
(1 << RowExclusiveLock) | (1 << RowShareLock) |
(1 << AccessExclusiveLock) | (1 << AccessShareLock)
};
static int LockPrios[] = {
(int) NULL,
0,
/* AccessShareLock */
1,
/* RowShareLock */
2,
/* RowExclusiveLock */
3,
/* ShareLock */
4,
/* ShareRowExclusiveLock */
5,
/* ExclusiveLock */
6,
/* AccessExclusiveLock */
7
};
@@ -134,7 +141,8 @@ LockRelation(Relation relation, LOCKMODE lockmode)
tag.dbId = relation->rd_lockInfo.lockRelId.dbId;
tag.objId.blkno = InvalidBlockNumber;
if (!LockAcquire(LockTableId, &tag, GetCurrentTransactionId(), lockmode))
if (!LockAcquire(LockTableId, &tag, GetCurrentTransactionId(),
lockmode, false))
elog(ERROR, "LockRelation: LockAcquire failed");
/*
@@ -148,6 +156,45 @@ LockRelation(Relation relation, LOCKMODE lockmode)
RelationDecrementReferenceCount(relation);
}
/*
* ConditionalLockRelation
*
* 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 the other
* LockXXX routines in this file, but they could easily be added if needed.
*/
bool
ConditionalLockRelation(Relation relation, LOCKMODE lockmode)
{
LOCKTAG tag;
if (LockingDisabled())
return true;
MemSet(&tag, 0, sizeof(tag));
tag.relId = relation->rd_lockInfo.lockRelId.relId;
tag.dbId = relation->rd_lockInfo.lockRelId.dbId;
tag.objId.blkno = InvalidBlockNumber;
if (!LockAcquire(LockTableId, &tag, GetCurrentTransactionId(),
lockmode, true))
return false;
/*
* Check to see if the relcache entry has been invalidated while we
* were waiting to lock it. If so, rebuild it, or elog() trying.
* Increment the refcount to ensure that RelationFlushRelation will
* rebuild it and not just delete it.
*/
RelationIncrementReferenceCount(relation);
AcceptInvalidationMessages();
RelationDecrementReferenceCount(relation);
return true;
}
/*
* UnlockRelation
*/
@@ -192,7 +239,8 @@ LockRelationForSession(LockRelId *relid, LOCKMODE lockmode)
tag.dbId = relid->dbId;
tag.objId.blkno = InvalidBlockNumber;
if (!LockAcquire(LockTableId, &tag, InvalidTransactionId, lockmode))
if (!LockAcquire(LockTableId, &tag, InvalidTransactionId,
lockmode, false))
elog(ERROR, "LockRelationForSession: LockAcquire failed");
}
@@ -231,7 +279,8 @@ LockPage(Relation relation, BlockNumber blkno, LOCKMODE lockmode)
tag.dbId = relation->rd_lockInfo.lockRelId.dbId;
tag.objId.blkno = blkno;
if (!LockAcquire(LockTableId, &tag, GetCurrentTransactionId(), lockmode))
if (!LockAcquire(LockTableId, &tag, GetCurrentTransactionId(),
lockmode, false))
elog(ERROR, "LockPage: LockAcquire failed");
}
@@ -267,7 +316,8 @@ XactLockTableInsert(TransactionId xid)
tag.dbId = InvalidOid; /* xids are globally unique */
tag.objId.xid = xid;
if (!LockAcquire(LockTableId, &tag, xid, ExclusiveLock))
if (!LockAcquire(LockTableId, &tag, xid,
ExclusiveLock, false))
elog(ERROR, "XactLockTableInsert: LockAcquire failed");
}
@@ -303,7 +353,8 @@ XactLockTableWait(TransactionId xid)
tag.dbId = InvalidOid;
tag.objId.xid = xid;
if (!LockAcquire(LockTableId, &tag, GetCurrentTransactionId(), ShareLock))
if (!LockAcquire(LockTableId, &tag, GetCurrentTransactionId(),
ShareLock, false))
elog(ERROR, "XactLockTableWait: LockAcquire failed");
LockRelease(LockTableId, &tag, GetCurrentTransactionId(), ShareLock);