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Improve LockAcquire API per my recent proposal. All error conditions

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are now reported via elog, eliminating the need to test the result code
at most call sites.  Make it possible for the caller to distinguish a
freshly acquired lock from one already held in the current transaction.
Use that capability to avoid redundant AcceptInvalidationMessages() calls
in LockRelation().
REL8_1_STABLE
Tom Lane 21 years ago
parent 299c442077
commit 140b078d2a
4 changed files with 81 additions and 69 deletions
Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL
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  1. 4
      contrib/userlock/user_locks.c
  2. 83
      src/backend/storage/lmgr/lmgr.c
  3. 50
      src/backend/storage/lmgr/lock.c
  4. 13
      src/include/storage/lock.h

4
contrib/userlock/user_locks.c
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@ -33,8 +33,8 @@ user_lock(uint32 id1, uint32 id2, LOCKMODE lockmode)
SET_LOCKTAG_USERLOCK(tag, id1, id2);
return LockAcquire(USER_LOCKMETHOD, &tag, InvalidTransactionId,
lockmode, true);
return (LockAcquire(USER_LOCKMETHOD, &tag, InvalidTransactionId,
lockmode, true) != LOCKACQUIRE_NOT_AVAIL);
}
int

83
src/backend/storage/lmgr/lmgr.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/lmgr/lmgr.c,v 1.74 2005/05/19 21:35:46 tgl Exp $
* $PostgreSQL: pgsql/src/backend/storage/lmgr/lmgr.c,v 1.75 2005/05/29 22:45:02 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -136,24 +136,28 @@ void
LockRelation(Relation relation, LOCKMODE lockmode)
{
LOCKTAG tag;
LockAcquireResult res;
SET_LOCKTAG_RELATION(tag,
relation->rd_lockInfo.lockRelId.dbId,
relation->rd_lockInfo.lockRelId.relId);
if (!LockAcquire(LockTableId, &tag, GetTopTransactionId(),
lockmode, false))
elog(ERROR, "LockAcquire failed");
res = LockAcquire(LockTableId, &tag, GetTopTransactionId(),
lockmode, false);
/*
* Check to see if the relcache entry has been invalidated while we
* were waiting to lock it. If so, rebuild it, or ereport() trying.
* Increment the refcount to ensure that RelationFlushRelation will
* rebuild it and not just delete it.
* rebuild it and not just delete it. We can skip this if the lock
* was already held, however.
*/
RelationIncrementReferenceCount(relation);
AcceptInvalidationMessages();
RelationDecrementReferenceCount(relation);
if (res != LOCKACQUIRE_ALREADY_HELD)
{
RelationIncrementReferenceCount(relation);
AcceptInvalidationMessages();
RelationDecrementReferenceCount(relation);
}
}
/*
@ -169,24 +173,31 @@ bool
ConditionalLockRelation(Relation relation, LOCKMODE lockmode)
{
LOCKTAG tag;
LockAcquireResult res;
SET_LOCKTAG_RELATION(tag,
relation->rd_lockInfo.lockRelId.dbId,
relation->rd_lockInfo.lockRelId.relId);
if (!LockAcquire(LockTableId, &tag, GetTopTransactionId(),
lockmode, true))
res = LockAcquire(LockTableId, &tag, GetTopTransactionId(),
lockmode, true);
if (res == LOCKACQUIRE_NOT_AVAIL)
return false;
/*
* Check to see if the relcache entry has been invalidated while we
* were waiting to lock it. If so, rebuild it, or ereport() trying.
* Increment the refcount to ensure that RelationFlushRelation will
* rebuild it and not just delete it.
* rebuild it and not just delete it. We can skip this if the lock
* was already held, however.
*/
RelationIncrementReferenceCount(relation);
AcceptInvalidationMessages();
RelationDecrementReferenceCount(relation);
if (res != LOCKACQUIRE_ALREADY_HELD)
{
RelationIncrementReferenceCount(relation);
AcceptInvalidationMessages();
RelationDecrementReferenceCount(relation);
}
return true;
}
@ -225,9 +236,8 @@ LockRelationForSession(LockRelId *relid, LOCKMODE lockmode)
SET_LOCKTAG_RELATION(tag, relid->dbId, relid->relId);
if (!LockAcquire(LockTableId, &tag, InvalidTransactionId,
lockmode, false))
elog(ERROR, "LockAcquire failed");
(void) LockAcquire(LockTableId, &tag, InvalidTransactionId,
lockmode, false);
}
/*
@ -262,9 +272,8 @@ LockRelationForExtension(Relation relation, LOCKMODE lockmode)
relation->rd_lockInfo.lockRelId.dbId,
relation->rd_lockInfo.lockRelId.relId);
if (!LockAcquire(LockTableId, &tag, GetTopTransactionId(),
lockmode, false))
elog(ERROR, "LockAcquire failed");
(void) LockAcquire(LockTableId, &tag, GetTopTransactionId(),
lockmode, false);
}
/*
@ -298,9 +307,8 @@ LockPage(Relation relation, BlockNumber blkno, LOCKMODE lockmode)
relation->rd_lockInfo.lockRelId.relId,
blkno);
if (!LockAcquire(LockTableId, &tag, GetTopTransactionId(),
lockmode, false))
elog(ERROR, "LockAcquire failed");
(void) LockAcquire(LockTableId, &tag, GetTopTransactionId(),
lockmode, false);
}
/*
@ -319,8 +327,8 @@ ConditionalLockPage(Relation relation, BlockNumber blkno, LOCKMODE lockmode)
relation->rd_lockInfo.lockRelId.relId,
blkno);
return LockAcquire(LockTableId, &tag, GetTopTransactionId(),
lockmode, true);
return (LockAcquire(LockTableId, &tag, GetTopTransactionId(),
lockmode, true) != LOCKACQUIRE_NOT_AVAIL);
}
/*
@ -357,9 +365,8 @@ LockTuple(Relation relation, ItemPointer tid, LOCKMODE lockmode)
ItemPointerGetBlockNumber(tid),
ItemPointerGetOffsetNumber(tid));
if (!LockAcquire(LockTableId, &tag, GetTopTransactionId(),
lockmode, false))
elog(ERROR, "LockAcquire failed");
(void) LockAcquire(LockTableId, &tag, GetTopTransactionId(),
lockmode, false);
}
/*
@ -393,9 +400,8 @@ XactLockTableInsert(TransactionId xid)
SET_LOCKTAG_TRANSACTION(tag, xid);
if (!LockAcquire(LockTableId, &tag, GetTopTransactionId(),
ExclusiveLock, false))
elog(ERROR, "LockAcquire failed");
(void) LockAcquire(LockTableId, &tag, GetTopTransactionId(),
ExclusiveLock, false);
}
/*
@ -441,8 +447,9 @@ XactLockTableWait(TransactionId xid)
SET_LOCKTAG_TRANSACTION(tag, xid);
if (!LockAcquire(LockTableId, &tag, myxid, ShareLock, false))
elog(ERROR, "LockAcquire failed");
(void) LockAcquire(LockTableId, &tag, myxid,
ShareLock, false);
LockRelease(LockTableId, &tag, myxid, ShareLock);
if (!TransactionIdIsInProgress(xid))
@ -479,9 +486,8 @@ LockDatabaseObject(Oid classid, Oid objid, uint16 objsubid,
objid,
objsubid);
if (!LockAcquire(LockTableId, &tag, GetTopTransactionId(),
lockmode, false))
elog(ERROR, "LockAcquire failed");
(void) LockAcquire(LockTableId, &tag, GetTopTransactionId(),
lockmode, false);
}
/*
@ -519,9 +525,8 @@ LockSharedObject(Oid classid, Oid objid, uint16 objsubid,
objid,
objsubid);
if (!LockAcquire(LockTableId, &tag, GetTopTransactionId(),
lockmode, false))
elog(ERROR, "LockAcquire failed");
(void) LockAcquire(LockTableId, &tag, GetTopTransactionId(),
lockmode, false);
}
/*

50
src/backend/storage/lmgr/lock.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/lmgr/lock.c,v 1.153 2005/05/29 04:23:04 tgl Exp $
* $PostgreSQL: pgsql/src/backend/storage/lmgr/lock.c,v 1.154 2005/05/29 22:45:02 tgl Exp $
*
* NOTES
* Outside modules can create a lock table and acquire/release
@ -160,8 +160,8 @@ PROCLOCK_PRINT(const char *where, const PROCLOCK *proclockP)
static void RemoveLocalLock(LOCALLOCK *locallock);
static void GrantLockLocal(LOCALLOCK *locallock, ResourceOwner owner);
static int WaitOnLock(LOCKMETHODID lockmethodid, LOCALLOCK *locallock,
ResourceOwner owner);
static void WaitOnLock(LOCKMETHODID lockmethodid, LOCALLOCK *locallock,
ResourceOwner owner);
static void LockCountMyLocks(SHMEM_OFFSET lockOffset, PGPROC *proc,
int *myHolding);
static bool UnGrantLock(LOCK *lock, LOCKMODE lockmode,
@ -377,11 +377,14 @@ LockMethodTableRename(LOCKMETHODID lockmethodid)
* LockAcquire -- Check for lock conflicts, sleep if conflict found,
* set lock if/when no conflicts.
*
* Returns: TRUE if lock was acquired, FALSE otherwise. Note that
* a FALSE return is to be expected if dontWait is TRUE;
* but if dontWait is FALSE, only a parameter error can cause
* a FALSE return. (XXX probably we should just ereport on parameter
* errors, instead of conflating this with failure to acquire lock?)
* Returns one of:
* LOCKACQUIRE_NOT_AVAIL lock not available, and dontWait=true
* LOCKACQUIRE_OK lock successfully acquired
* LOCKACQUIRE_ALREADY_HELD incremented count for lock already held
*
* In the normal case where dontWait=false and the caller doesn't need to
* distinguish a freshly acquired lock from one already taken earlier in
* this same transaction, there is no need to examine the return value.
*
* Side Effects: The lock is acquired and recorded in lock tables.
*
@ -416,8 +419,7 @@ LockMethodTableRename(LOCKMETHODID lockmethodid)
*
* DZ - 22 Nov 1997
*/
bool
LockAcquireResult
LockAcquire(LOCKMETHODID lockmethodid, LOCKTAG *locktag,
TransactionId xid, LOCKMODE lockmode, bool dontWait)
{
@ -447,10 +449,7 @@ LockAcquire(LOCKMETHODID lockmethodid, LOCKTAG *locktag,
Assert(lockmethodid < NumLockMethods);
lockMethodTable = LockMethods[lockmethodid];
if (!lockMethodTable)
{
elog(WARNING, "bad lock table id: %d", lockmethodid);
return FALSE;
}
elog(ERROR, "unrecognized lock method: %d", lockmethodid);
/* Session locks and user locks are not transactional */
if (xid != InvalidTransactionId &&
@ -507,7 +506,7 @@ LockAcquire(LOCKMETHODID lockmethodid, LOCKTAG *locktag,
if (locallock->nLocks > 0)
{
GrantLockLocal(locallock, owner);
return TRUE;
return LOCKACQUIRE_ALREADY_HELD;
}
/*
@ -669,7 +668,7 @@ LockAcquire(LOCKMETHODID lockmethodid, LOCKTAG *locktag,
GrantLockLocal(locallock, owner);
PROCLOCK_PRINT("LockAcquire: my other XID owning", proclock);
LWLockRelease(masterLock);
return TRUE;
return LOCKACQUIRE_ALREADY_HELD;
}
/*
@ -696,8 +695,8 @@ LockAcquire(LOCKMETHODID lockmethodid, LOCKTAG *locktag,
/*
* We can't acquire the lock immediately. If caller specified no
* blocking, remove useless table entries and return FALSE without
* waiting.
* blocking, remove useless table entries and return NOT_AVAIL
* without waiting.
*/
if (dontWait)
{
@ -720,7 +719,7 @@ LockAcquire(LOCKMETHODID lockmethodid, LOCKTAG *locktag,
LWLockRelease(masterLock);
if (locallock->nLocks == 0)
RemoveLocalLock(locallock);
return FALSE;
return LOCKACQUIRE_NOT_AVAIL;
}
/*
@ -740,7 +739,7 @@ LockAcquire(LOCKMETHODID lockmethodid, LOCKTAG *locktag,
/*
* Sleep till someone wakes me up.
*/
status = WaitOnLock(lockmethodid, locallock, owner);
WaitOnLock(lockmethodid, locallock, owner);
/*
* NOTE: do not do any material change of state between here and
@ -759,7 +758,7 @@ LockAcquire(LOCKMETHODID lockmethodid, LOCKTAG *locktag,
LOCK_PRINT("LockAcquire: INCONSISTENT", lock, lockmode);
/* Should we retry ? */
LWLockRelease(masterLock);
return FALSE;
elog(ERROR, "LockAcquire failed");
}
PROCLOCK_PRINT("LockAcquire: granted", proclock);
LOCK_PRINT("LockAcquire: granted", lock, lockmode);
@ -767,7 +766,7 @@ LockAcquire(LOCKMETHODID lockmethodid, LOCKTAG *locktag,
LWLockRelease(masterLock);
return status == STATUS_OK;
return LOCKACQUIRE_OK;
}
/*
@ -1091,7 +1090,7 @@ GrantAwaitedLock(void)
*
* The locktable's masterLock must be held at entry.
*/
static int
static void
WaitOnLock(LOCKMETHODID lockmethodid, LOCALLOCK *locallock,
ResourceOwner owner)
{
@ -1159,7 +1158,6 @@ WaitOnLock(LOCKMETHODID lockmethodid, LOCALLOCK *locallock,
LOCK_PRINT("WaitOnLock: wakeup on lock",
locallock->lock, locallock->tag.mode);
return STATUS_OK;
}
/*
@ -1247,7 +1245,7 @@ LockRelease(LOCKMETHODID lockmethodid, LOCKTAG *locktag,
Assert(lockmethodid < NumLockMethods);
lockMethodTable = LockMethods[lockmethodid];
if (!lockMethodTable)
elog(ERROR, "bad lock method: %d", lockmethodid);
elog(ERROR, "unrecognized lock method: %d", lockmethodid);
/*
* Find the LOCALLOCK entry for this lock and lockmode
@ -1397,7 +1395,7 @@ LockReleaseAll(LOCKMETHODID lockmethodid, bool allxids)
Assert(lockmethodid < NumLockMethods);
lockMethodTable = LockMethods[lockmethodid];
if (!lockMethodTable)
elog(ERROR, "bad lock method: %d", lockmethodid);
elog(ERROR, "unrecognized lock method: %d", lockmethodid);
numLockModes = lockMethodTable->numLockModes;
masterLock = lockMethodTable->masterLock;

13
src/include/storage/lock.h
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@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/storage/lock.h,v 1.86 2005/05/19 23:30:18 tgl Exp $
* $PostgreSQL: pgsql/src/include/storage/lock.h,v 1.87 2005/05/29 22:45:02 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -348,6 +348,15 @@ typedef struct
} LockData;
/* Result codes for LockAcquire() */
typedef enum
{
LOCKACQUIRE_NOT_AVAIL, /* lock not available, and dontWait=true */
LOCKACQUIRE_OK, /* lock successfully acquired */
LOCKACQUIRE_ALREADY_HELD /* incremented count for lock already held */
} LockAcquireResult;
/*
* function prototypes
*/
@ -357,7 +366,7 @@ extern LOCKMETHODID LockMethodTableInit(const char *tabName,
const LOCKMASK *conflictsP,
int numModes, int maxBackends);
extern LOCKMETHODID LockMethodTableRename(LOCKMETHODID lockmethodid);
extern bool LockAcquire(LOCKMETHODID lockmethodid, LOCKTAG *locktag,
extern LockAcquireResult LockAcquire(LOCKMETHODID lockmethodid, LOCKTAG *locktag,
TransactionId xid, LOCKMODE lockmode, bool dontWait);
extern bool LockRelease(LOCKMETHODID lockmethodid, LOCKTAG *locktag,
TransactionId xid, LOCKMODE lockmode);

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