mirror of
https://git.postgresql.org/git/postgresql.git
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11635c3f6f
from LockRelease() and LockReleaseAll() into it. From Heikki Linnakangas.
1886 lines
53 KiB
C
1886 lines
53 KiB
C
/*-------------------------------------------------------------------------
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*
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* lock.c
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* POSTGRES low-level lock mechanism
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*
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* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/storage/lmgr/lock.c,v 1.146 2005/02/04 02:04:53 neilc Exp $
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*
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* NOTES
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* Outside modules can create a lock table and acquire/release
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* locks. A lock table is a shared memory hash table. When
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* a process tries to acquire a lock of a type that conflicts
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* with existing locks, it is put to sleep using the routines
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* in storage/lmgr/proc.c.
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*
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* For the most part, this code should be invoked via lmgr.c
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* or another lock-management module, not directly.
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*
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* Interface:
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*
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* LockAcquire(), LockRelease(), LockMethodTableInit(),
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* LockMethodTableRename(), LockReleaseAll(),
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* LockCheckConflicts(), GrantLock()
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include <signal.h>
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#include <unistd.h>
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#include "access/xact.h"
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#include "miscadmin.h"
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#include "storage/proc.h"
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#include "utils/memutils.h"
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#include "utils/ps_status.h"
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#include "utils/resowner.h"
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/* This configuration variable is used to set the lock table size */
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int max_locks_per_xact; /* set by guc.c */
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#define NLOCKENTS(maxBackends) (max_locks_per_xact * (maxBackends))
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/*
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* map from lock method id to the lock table data structures
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*/
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static LockMethod LockMethods[MAX_LOCK_METHODS];
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static HTAB *LockMethodLockHash[MAX_LOCK_METHODS];
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static HTAB *LockMethodProcLockHash[MAX_LOCK_METHODS];
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static HTAB *LockMethodLocalHash[MAX_LOCK_METHODS];
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/* exported so lmgr.c can initialize it */
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int NumLockMethods;
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/* private state for GrantAwaitedLock */
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static LOCALLOCK *awaitedLock;
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static ResourceOwner awaitedOwner;
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static const char *const lock_mode_names[] =
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{
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"INVALID",
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"AccessShareLock",
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"RowShareLock",
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"RowExclusiveLock",
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"ShareUpdateExclusiveLock",
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"ShareLock",
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"ShareRowExclusiveLock",
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"ExclusiveLock",
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"AccessExclusiveLock"
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};
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#ifdef LOCK_DEBUG
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/*------
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* The following configuration options are available for lock debugging:
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*
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* TRACE_LOCKS -- give a bunch of output what's going on in this file
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* TRACE_USERLOCKS -- same but for user locks
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* TRACE_LOCK_OIDMIN-- do not trace locks for tables below this oid
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* (use to avoid output on system tables)
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* TRACE_LOCK_TABLE -- trace locks on this table (oid) unconditionally
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* DEBUG_DEADLOCKS -- currently dumps locks at untimely occasions ;)
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*
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* Furthermore, but in storage/lmgr/lwlock.c:
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* TRACE_LWLOCKS -- trace lightweight locks (pretty useless)
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*
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* Define LOCK_DEBUG at compile time to get all these enabled.
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* --------
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*/
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int Trace_lock_oidmin = BootstrapObjectIdData;
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bool Trace_locks = false;
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bool Trace_userlocks = false;
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int Trace_lock_table = 0;
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bool Debug_deadlocks = false;
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inline static bool
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LOCK_DEBUG_ENABLED(const LOCK *lock)
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{
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return
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(((LOCK_LOCKMETHOD(*lock) == DEFAULT_LOCKMETHOD && Trace_locks)
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|| (LOCK_LOCKMETHOD(*lock) == USER_LOCKMETHOD && Trace_userlocks))
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&& (lock->tag.relId >= (Oid) Trace_lock_oidmin))
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|| (Trace_lock_table && (lock->tag.relId == Trace_lock_table));
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}
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inline static void
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LOCK_PRINT(const char *where, const LOCK *lock, LOCKMODE type)
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{
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if (LOCK_DEBUG_ENABLED(lock))
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elog(LOG,
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"%s: lock(%lx) tbl(%d) rel(%u) db(%u) obj(%u) grantMask(%x) "
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"req(%d,%d,%d,%d,%d,%d,%d)=%d "
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"grant(%d,%d,%d,%d,%d,%d,%d)=%d wait(%d) type(%s)",
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where, MAKE_OFFSET(lock),
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lock->tag.lockmethodid, lock->tag.relId, lock->tag.dbId,
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lock->tag.objId.blkno, lock->grantMask,
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lock->requested[1], lock->requested[2], lock->requested[3],
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lock->requested[4], lock->requested[5], lock->requested[6],
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lock->requested[7], lock->nRequested,
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lock->granted[1], lock->granted[2], lock->granted[3],
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lock->granted[4], lock->granted[5], lock->granted[6],
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lock->granted[7], lock->nGranted,
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lock->waitProcs.size, lock_mode_names[type]);
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}
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inline static void
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PROCLOCK_PRINT(const char *where, const PROCLOCK *proclockP)
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{
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if (
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(((PROCLOCK_LOCKMETHOD(*proclockP) == DEFAULT_LOCKMETHOD && Trace_locks)
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|| (PROCLOCK_LOCKMETHOD(*proclockP) == USER_LOCKMETHOD && Trace_userlocks))
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&& (((LOCK *) MAKE_PTR(proclockP->tag.lock))->tag.relId >= (Oid) Trace_lock_oidmin))
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|| (Trace_lock_table && (((LOCK *) MAKE_PTR(proclockP->tag.lock))->tag.relId == Trace_lock_table))
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)
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elog(LOG,
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"%s: proclock(%lx) lock(%lx) tbl(%d) proc(%lx) xid(%u) hold(%x)",
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where, MAKE_OFFSET(proclockP), proclockP->tag.lock,
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PROCLOCK_LOCKMETHOD(*(proclockP)),
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proclockP->tag.proc, proclockP->tag.xid,
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(int) proclockP->holdMask);
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}
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#else /* not LOCK_DEBUG */
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#define LOCK_PRINT(where, lock, type)
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#define PROCLOCK_PRINT(where, proclockP)
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#endif /* not LOCK_DEBUG */
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static void RemoveLocalLock(LOCALLOCK *locallock);
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static void GrantLockLocal(LOCALLOCK *locallock, ResourceOwner owner);
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static int WaitOnLock(LOCKMETHODID lockmethodid, LOCALLOCK *locallock,
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ResourceOwner owner);
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static void LockCountMyLocks(SHMEM_OFFSET lockOffset, PGPROC *proc,
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int *myHolding);
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static bool UnGrantLock(LOCK *lock, LOCKMODE lockmode,
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PROCLOCK *proclock, LockMethod lockMethodTable);
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/*
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* InitLocks -- Init the lock module. Create a private data
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* structure for constructing conflict masks.
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*/
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void
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InitLocks(void)
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{
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/* NOP */
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}
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/*
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* Fetch the lock method table associated with a given lock
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*/
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LockMethod
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GetLocksMethodTable(LOCK *lock)
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{
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LOCKMETHODID lockmethodid = LOCK_LOCKMETHOD(*lock);
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Assert(0 < lockmethodid && lockmethodid < NumLockMethods);
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return LockMethods[lockmethodid];
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}
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/*
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* LockMethodInit -- initialize the lock table's lock type
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* structures
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*
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* Notes: just copying. Should only be called once.
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*/
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static void
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LockMethodInit(LockMethod lockMethodTable,
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const LOCKMASK *conflictsP,
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int numModes)
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{
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int i;
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lockMethodTable->numLockModes = numModes;
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/* copies useless zero element as well as the N lockmodes */
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for (i = 0; i <= numModes; i++)
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lockMethodTable->conflictTab[i] = conflictsP[i];
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}
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/*
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* LockMethodTableInit -- initialize a lock table structure
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*
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* NOTE: data structures allocated here are allocated permanently, using
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* TopMemoryContext and shared memory. We don't ever release them anyway,
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* and in normal multi-backend operation the lock table structures set up
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* by the postmaster are inherited by each backend, so they must be in
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* TopMemoryContext.
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*/
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LOCKMETHODID
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LockMethodTableInit(const char *tabName,
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const LOCKMASK *conflictsP,
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int numModes,
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int maxBackends)
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{
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LockMethod newLockMethod;
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LOCKMETHODID lockmethodid;
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char *shmemName;
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HASHCTL info;
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int hash_flags;
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bool found;
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long init_table_size,
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max_table_size;
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if (numModes >= MAX_LOCKMODES)
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elog(ERROR, "too many lock types %d (limit is %d)",
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numModes, MAX_LOCKMODES - 1);
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/* Compute init/max size to request for lock hashtables */
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max_table_size = NLOCKENTS(maxBackends);
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init_table_size = max_table_size / 2;
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/* Allocate a string for the shmem index table lookups. */
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/* This is just temp space in this routine, so palloc is OK. */
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shmemName = (char *) palloc(strlen(tabName) + 32);
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/* each lock table has a header in shared memory */
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sprintf(shmemName, "%s (lock method table)", tabName);
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newLockMethod = (LockMethod)
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ShmemInitStruct(shmemName, sizeof(LockMethodData), &found);
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if (!newLockMethod)
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elog(FATAL, "could not initialize lock table \"%s\"", tabName);
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/*
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* we're first - initialize
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*/
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if (!found)
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{
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MemSet(newLockMethod, 0, sizeof(LockMethodData));
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newLockMethod->masterLock = LockMgrLock;
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LockMethodInit(newLockMethod, conflictsP, numModes);
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}
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/*
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* other modules refer to the lock table by a lockmethod ID
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*/
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Assert(NumLockMethods < MAX_LOCK_METHODS);
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lockmethodid = NumLockMethods++;
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LockMethods[lockmethodid] = newLockMethod;
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/*
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* allocate a hash table for LOCK structs. This is used to store
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* per-locked-object information.
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*/
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MemSet(&info, 0, sizeof(info));
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info.keysize = sizeof(LOCKTAG);
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info.entrysize = sizeof(LOCK);
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info.hash = tag_hash;
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hash_flags = (HASH_ELEM | HASH_FUNCTION);
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sprintf(shmemName, "%s (lock hash)", tabName);
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LockMethodLockHash[lockmethodid] = ShmemInitHash(shmemName,
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init_table_size,
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max_table_size,
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&info,
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hash_flags);
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if (!LockMethodLockHash[lockmethodid])
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elog(FATAL, "could not initialize lock table \"%s\"", tabName);
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/*
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* allocate a hash table for PROCLOCK structs. This is used to store
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* per-lock-holder information.
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*/
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info.keysize = sizeof(PROCLOCKTAG);
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info.entrysize = sizeof(PROCLOCK);
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info.hash = tag_hash;
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hash_flags = (HASH_ELEM | HASH_FUNCTION);
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sprintf(shmemName, "%s (proclock hash)", tabName);
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LockMethodProcLockHash[lockmethodid] = ShmemInitHash(shmemName,
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init_table_size,
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max_table_size,
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&info,
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hash_flags);
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if (!LockMethodProcLockHash[lockmethodid])
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elog(FATAL, "could not initialize lock table \"%s\"", tabName);
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/*
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* allocate a non-shared hash table for LOCALLOCK structs. This is
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* used to store lock counts and resource owner information.
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*
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* The non-shared table could already exist in this process (this occurs
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* when the postmaster is recreating shared memory after a backend
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* crash). If so, delete and recreate it. (We could simply leave it,
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* since it ought to be empty in the postmaster, but for safety let's
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* zap it.)
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*/
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if (LockMethodLocalHash[lockmethodid])
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hash_destroy(LockMethodLocalHash[lockmethodid]);
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info.keysize = sizeof(LOCALLOCKTAG);
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info.entrysize = sizeof(LOCALLOCK);
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info.hash = tag_hash;
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hash_flags = (HASH_ELEM | HASH_FUNCTION);
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sprintf(shmemName, "%s (locallock hash)", tabName);
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LockMethodLocalHash[lockmethodid] = hash_create(shmemName,
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128,
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&info,
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hash_flags);
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pfree(shmemName);
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return lockmethodid;
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}
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/*
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* LockMethodTableRename -- allocate another lockmethod ID to the same
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* lock table.
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*
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* NOTES: Both the lock module and the lock chain (lchain.c)
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* module use table id's to distinguish between different
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* kinds of locks. Short term and long term locks look
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* the same to the lock table, but are handled differently
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* by the lock chain manager. This function allows the
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* client to use different lockmethods when acquiring/releasing
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* short term and long term locks, yet store them all in one hashtable.
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*/
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LOCKMETHODID
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LockMethodTableRename(LOCKMETHODID lockmethodid)
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{
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LOCKMETHODID newLockMethodId;
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if (NumLockMethods >= MAX_LOCK_METHODS)
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return INVALID_LOCKMETHOD;
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if (LockMethods[lockmethodid] == INVALID_LOCKMETHOD)
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return INVALID_LOCKMETHOD;
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/* other modules refer to the lock table by a lockmethod ID */
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newLockMethodId = NumLockMethods;
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NumLockMethods++;
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LockMethods[newLockMethodId] = LockMethods[lockmethodid];
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LockMethodLockHash[newLockMethodId] = LockMethodLockHash[lockmethodid];
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LockMethodProcLockHash[newLockMethodId] = LockMethodProcLockHash[lockmethodid];
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LockMethodLocalHash[newLockMethodId] = LockMethodLocalHash[lockmethodid];
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return newLockMethodId;
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}
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/*
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* LockAcquire -- Check for lock conflicts, sleep if conflict found,
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* set lock if/when no conflicts.
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*
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* Returns: TRUE if lock was acquired, FALSE otherwise. Note that
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* a FALSE return is to be expected if dontWait is TRUE;
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* but if dontWait is FALSE, only a parameter error can cause
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* a FALSE return. (XXX probably we should just ereport on parameter
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* errors, instead of conflating this with failure to acquire lock?)
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*
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* Side Effects: The lock is acquired and recorded in lock tables.
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*
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* NOTE: if we wait for the lock, there is no way to abort the wait
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* short of aborting the transaction.
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*
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*
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* Note on User Locks:
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*
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* User locks are handled totally on the application side as
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* long term cooperative locks which extend beyond the normal
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* transaction boundaries. Their purpose is to indicate to an
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* application that someone is `working' on an item. So it is
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* possible to put an user lock on a tuple's oid, retrieve the
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* tuple, work on it for an hour and then update it and remove
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* the lock. While the lock is active other clients can still
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* read and write the tuple but they can be aware that it has
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* been locked at the application level by someone.
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* User locks use lock tags made of an uint16 and an uint32, for
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* example 0 and a tuple oid, or any other arbitrary pair of
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* numbers following a convention established by the application.
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* In this sense tags don't refer to tuples or database entities.
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* User locks and normal locks are completely orthogonal and
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* they don't interfere with each other, so it is possible
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* to acquire a normal lock on an user-locked tuple or user-lock
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* a tuple for which a normal write lock already exists.
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* User locks are always non blocking, therefore they are never
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* acquired if already held by another process. They must be
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* released explicitly by the application but they are released
|
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* automatically when a backend terminates.
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* They are indicated by a lockmethod 2 which is an alias for the
|
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* normal lock table, and are distinguished from normal locks
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* by the following differences:
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*
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* normal lock user lock
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*
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* lockmethodid 1 2
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* tag.dbId database oid database oid
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* tag.relId rel oid or 0 0
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* tag.objId block id lock id2
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* or xact id
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* tag.offnum 0 lock id1
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* proclock.xid xid or 0 0
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* persistence transaction user or backend
|
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* or backend
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*
|
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* The lockmode parameter can have the same values for normal locks
|
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* although probably only WRITE_LOCK can have some practical use.
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*
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* DZ - 22 Nov 1997
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*/
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|
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bool
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LockAcquire(LOCKMETHODID lockmethodid, LOCKTAG *locktag,
|
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TransactionId xid, LOCKMODE lockmode, bool dontWait)
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{
|
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LOCALLOCKTAG localtag;
|
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LOCALLOCK *locallock;
|
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LOCK *lock;
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PROCLOCK *proclock;
|
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PROCLOCKTAG proclocktag;
|
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bool found;
|
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ResourceOwner owner;
|
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LWLockId masterLock;
|
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LockMethod lockMethodTable;
|
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int status;
|
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int myHolding[MAX_LOCKMODES];
|
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int i;
|
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|
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#ifdef LOCK_DEBUG
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if (lockmethodid == USER_LOCKMETHOD && Trace_userlocks)
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elog(LOG, "LockAcquire: user lock [%u] %s",
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locktag->objId.blkno, lock_mode_names[lockmode]);
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#endif
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|
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/* ???????? This must be changed when short term locks will be used */
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locktag->lockmethodid = lockmethodid;
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|
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Assert(lockmethodid < NumLockMethods);
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lockMethodTable = LockMethods[lockmethodid];
|
|
if (!lockMethodTable)
|
|
{
|
|
elog(WARNING, "bad lock table id: %d", lockmethodid);
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return FALSE;
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|
}
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|
|
/* Session locks and user locks are not transactional */
|
|
if (xid != InvalidTransactionId &&
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lockmethodid == DEFAULT_LOCKMETHOD)
|
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owner = CurrentResourceOwner;
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else
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owner = NULL;
|
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|
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/*
|
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* Find or create a LOCALLOCK entry for this lock and lockmode
|
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*/
|
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MemSet(&localtag, 0, sizeof(localtag)); /* must clear padding */
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localtag.lock = *locktag;
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localtag.xid = xid;
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localtag.mode = lockmode;
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locallock = (LOCALLOCK *) hash_search(LockMethodLocalHash[lockmethodid],
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(void *) &localtag,
|
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HASH_ENTER, &found);
|
|
if (!locallock)
|
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ereport(ERROR,
|
|
(errcode(ERRCODE_OUT_OF_MEMORY),
|
|
errmsg("out of memory")));
|
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|
|
/*
|
|
* if it's a new locallock object, initialize it
|
|
*/
|
|
if (!found)
|
|
{
|
|
locallock->lock = NULL;
|
|
locallock->proclock = NULL;
|
|
locallock->nLocks = 0;
|
|
locallock->numLockOwners = 0;
|
|
locallock->maxLockOwners = 8;
|
|
locallock->lockOwners = NULL;
|
|
locallock->lockOwners = (LOCALLOCKOWNER *)
|
|
MemoryContextAlloc(TopMemoryContext,
|
|
locallock->maxLockOwners * sizeof(LOCALLOCKOWNER));
|
|
}
|
|
else
|
|
{
|
|
/* Make sure there will be room to remember the lock */
|
|
if (locallock->numLockOwners >= locallock->maxLockOwners)
|
|
{
|
|
int newsize = locallock->maxLockOwners * 2;
|
|
|
|
locallock->lockOwners = (LOCALLOCKOWNER *)
|
|
repalloc(locallock->lockOwners,
|
|
newsize * sizeof(LOCALLOCKOWNER));
|
|
locallock->maxLockOwners = newsize;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* If we already hold the lock, we can just increase the count
|
|
* locally.
|
|
*/
|
|
if (locallock->nLocks > 0)
|
|
{
|
|
GrantLockLocal(locallock, owner);
|
|
return TRUE;
|
|
}
|
|
|
|
/*
|
|
* Otherwise we've got to mess with the shared lock table.
|
|
*/
|
|
masterLock = lockMethodTable->masterLock;
|
|
|
|
LWLockAcquire(masterLock, LW_EXCLUSIVE);
|
|
|
|
/*
|
|
* Find or create a lock with this tag.
|
|
*
|
|
* Note: if the locallock object already existed, it might have a pointer
|
|
* to the lock already ... but we probably should not assume that that
|
|
* pointer is valid, since a lock object with no locks can go away
|
|
* anytime.
|
|
*/
|
|
lock = (LOCK *) hash_search(LockMethodLockHash[lockmethodid],
|
|
(void *) locktag,
|
|
HASH_ENTER, &found);
|
|
if (!lock)
|
|
{
|
|
LWLockRelease(masterLock);
|
|
ereport(ERROR,
|
|
(errcode(ERRCODE_OUT_OF_MEMORY),
|
|
errmsg("out of shared memory"),
|
|
errhint("You may need to increase max_locks_per_transaction.")));
|
|
}
|
|
locallock->lock = lock;
|
|
|
|
/*
|
|
* if it's a new lock object, initialize it
|
|
*/
|
|
if (!found)
|
|
{
|
|
lock->grantMask = 0;
|
|
lock->waitMask = 0;
|
|
SHMQueueInit(&(lock->procLocks));
|
|
ProcQueueInit(&(lock->waitProcs));
|
|
lock->nRequested = 0;
|
|
lock->nGranted = 0;
|
|
MemSet((char *) lock->requested, 0, sizeof(int) * MAX_LOCKMODES);
|
|
MemSet((char *) lock->granted, 0, sizeof(int) * MAX_LOCKMODES);
|
|
LOCK_PRINT("LockAcquire: new", lock, lockmode);
|
|
}
|
|
else
|
|
{
|
|
LOCK_PRINT("LockAcquire: found", lock, lockmode);
|
|
Assert((lock->nRequested >= 0) && (lock->requested[lockmode] >= 0));
|
|
Assert((lock->nGranted >= 0) && (lock->granted[lockmode] >= 0));
|
|
Assert(lock->nGranted <= lock->nRequested);
|
|
}
|
|
|
|
/*
|
|
* Create the hash key for the proclock table.
|
|
*/
|
|
MemSet(&proclocktag, 0, sizeof(PROCLOCKTAG)); /* must clear padding */
|
|
proclocktag.lock = MAKE_OFFSET(lock);
|
|
proclocktag.proc = MAKE_OFFSET(MyProc);
|
|
TransactionIdStore(xid, &proclocktag.xid);
|
|
|
|
/*
|
|
* Find or create a proclock entry with this tag
|
|
*/
|
|
proclock = (PROCLOCK *) hash_search(LockMethodProcLockHash[lockmethodid],
|
|
(void *) &proclocktag,
|
|
HASH_ENTER, &found);
|
|
if (!proclock)
|
|
{
|
|
/* Ooops, not enough shmem for the proclock */
|
|
if (lock->nRequested == 0)
|
|
{
|
|
/*
|
|
* There are no other requestors of this lock, so garbage-collect
|
|
* the lock object. We *must* do this to avoid a permanent leak
|
|
* of shared memory, because there won't be anything to cause
|
|
* anyone to release the lock object later.
|
|
*/
|
|
Assert(SHMQueueEmpty(&(lock->procLocks)));
|
|
lock = (LOCK *) hash_search(LockMethodLockHash[lockmethodid],
|
|
(void *) &(lock->tag),
|
|
HASH_REMOVE, NULL);
|
|
}
|
|
LWLockRelease(masterLock);
|
|
if (!lock) /* hash remove failed? */
|
|
elog(WARNING, "lock table corrupted");
|
|
ereport(ERROR,
|
|
(errcode(ERRCODE_OUT_OF_MEMORY),
|
|
errmsg("out of shared memory"),
|
|
errhint("You may need to increase max_locks_per_transaction.")));
|
|
}
|
|
locallock->proclock = proclock;
|
|
|
|
/*
|
|
* If new, initialize the new entry
|
|
*/
|
|
if (!found)
|
|
{
|
|
proclock->holdMask = 0;
|
|
/* Add proclock to appropriate lists */
|
|
SHMQueueInsertBefore(&lock->procLocks, &proclock->lockLink);
|
|
SHMQueueInsertBefore(&MyProc->procLocks, &proclock->procLink);
|
|
PROCLOCK_PRINT("LockAcquire: new", proclock);
|
|
}
|
|
else
|
|
{
|
|
PROCLOCK_PRINT("LockAcquire: found", proclock);
|
|
Assert((proclock->holdMask & ~lock->grantMask) == 0);
|
|
|
|
#ifdef CHECK_DEADLOCK_RISK
|
|
|
|
/*
|
|
* Issue warning if we already hold a lower-level lock on this
|
|
* object and do not hold a lock of the requested level or higher.
|
|
* This indicates a deadlock-prone coding practice (eg, we'd have
|
|
* a deadlock if another backend were following the same code path
|
|
* at about the same time).
|
|
*
|
|
* This is not enabled by default, because it may generate log
|
|
* entries about user-level coding practices that are in fact safe
|
|
* in context. It can be enabled to help find system-level
|
|
* problems.
|
|
*
|
|
* XXX Doing numeric comparison on the lockmodes is a hack; it'd be
|
|
* better to use a table. For now, though, this works.
|
|
*/
|
|
for (i = lockMethodTable->numLockModes; i > 0; i--)
|
|
{
|
|
if (proclock->holdMask & LOCKBIT_ON(i))
|
|
{
|
|
if (i >= (int) lockmode)
|
|
break; /* safe: we have a lock >= req level */
|
|
elog(LOG, "deadlock risk: raising lock level"
|
|
" from %s to %s on object %u/%u/%u",
|
|
lock_mode_names[i], lock_mode_names[lockmode],
|
|
lock->tag.relId, lock->tag.dbId, lock->tag.objId.blkno);
|
|
break;
|
|
}
|
|
}
|
|
#endif /* CHECK_DEADLOCK_RISK */
|
|
}
|
|
|
|
/*
|
|
* lock->nRequested and lock->requested[] count the total number of
|
|
* requests, whether granted or waiting, so increment those
|
|
* immediately. The other counts don't increment till we get the lock.
|
|
*/
|
|
lock->nRequested++;
|
|
lock->requested[lockmode]++;
|
|
Assert((lock->nRequested > 0) && (lock->requested[lockmode] > 0));
|
|
|
|
/*
|
|
* If this process (under any XID) is a holder of the lock, just grant
|
|
* myself another one without blocking.
|
|
*/
|
|
LockCountMyLocks(proclock->tag.lock, MyProc, myHolding);
|
|
if (myHolding[lockmode] > 0)
|
|
{
|
|
GrantLock(lock, proclock, lockmode);
|
|
GrantLockLocal(locallock, owner);
|
|
PROCLOCK_PRINT("LockAcquire: my other XID owning", proclock);
|
|
LWLockRelease(masterLock);
|
|
return TRUE;
|
|
}
|
|
|
|
/*
|
|
* If lock requested conflicts with locks requested by waiters, must
|
|
* join wait queue. Otherwise, check for conflict with already-held
|
|
* locks. (That's last because most complex check.)
|
|
*/
|
|
if (lockMethodTable->conflictTab[lockmode] & lock->waitMask)
|
|
status = STATUS_FOUND;
|
|
else
|
|
status = LockCheckConflicts(lockMethodTable, lockmode,
|
|
lock, proclock,
|
|
MyProc, myHolding);
|
|
|
|
if (status == STATUS_OK)
|
|
{
|
|
/* No conflict with held or previously requested locks */
|
|
GrantLock(lock, proclock, lockmode);
|
|
GrantLockLocal(locallock, owner);
|
|
}
|
|
else
|
|
{
|
|
Assert(status == STATUS_FOUND);
|
|
|
|
/*
|
|
* We can't acquire the lock immediately. If caller specified no
|
|
* blocking, remove useless table entries and return FALSE without
|
|
* waiting.
|
|
*/
|
|
if (dontWait)
|
|
{
|
|
if (proclock->holdMask == 0)
|
|
{
|
|
SHMQueueDelete(&proclock->lockLink);
|
|
SHMQueueDelete(&proclock->procLink);
|
|
proclock = (PROCLOCK *) hash_search(LockMethodProcLockHash[lockmethodid],
|
|
(void *) &(proclock->tag),
|
|
HASH_REMOVE, NULL);
|
|
if (!proclock)
|
|
elog(WARNING, "proclock table corrupted");
|
|
}
|
|
else
|
|
PROCLOCK_PRINT("LockAcquire: NOWAIT", proclock);
|
|
lock->nRequested--;
|
|
lock->requested[lockmode]--;
|
|
LOCK_PRINT("LockAcquire: conditional lock failed", lock, lockmode);
|
|
Assert((lock->nRequested > 0) && (lock->requested[lockmode] >= 0));
|
|
Assert(lock->nGranted <= lock->nRequested);
|
|
LWLockRelease(masterLock);
|
|
if (locallock->nLocks == 0)
|
|
RemoveLocalLock(locallock);
|
|
return FALSE;
|
|
}
|
|
|
|
/*
|
|
* Construct bitmask of locks this process holds on this object.
|
|
*/
|
|
{
|
|
LOCKMASK heldLocks = 0;
|
|
|
|
for (i = 1; i <= lockMethodTable->numLockModes; i++)
|
|
{
|
|
if (myHolding[i] > 0)
|
|
heldLocks |= LOCKBIT_ON(i);
|
|
}
|
|
MyProc->heldLocks = heldLocks;
|
|
}
|
|
|
|
/*
|
|
* Sleep till someone wakes me up.
|
|
*/
|
|
status = WaitOnLock(lockmethodid, locallock, owner);
|
|
|
|
/*
|
|
* NOTE: do not do any material change of state between here and
|
|
* return. All required changes in locktable state must have been
|
|
* done when the lock was granted to us --- see notes in
|
|
* WaitOnLock.
|
|
*/
|
|
|
|
/*
|
|
* Check the proclock entry status, in case something in the ipc
|
|
* communication doesn't work correctly.
|
|
*/
|
|
if (!(proclock->holdMask & LOCKBIT_ON(lockmode)))
|
|
{
|
|
PROCLOCK_PRINT("LockAcquire: INCONSISTENT", proclock);
|
|
LOCK_PRINT("LockAcquire: INCONSISTENT", lock, lockmode);
|
|
/* Should we retry ? */
|
|
LWLockRelease(masterLock);
|
|
return FALSE;
|
|
}
|
|
PROCLOCK_PRINT("LockAcquire: granted", proclock);
|
|
LOCK_PRINT("LockAcquire: granted", lock, lockmode);
|
|
}
|
|
|
|
LWLockRelease(masterLock);
|
|
|
|
return status == STATUS_OK;
|
|
}
|
|
|
|
/*
|
|
* Subroutine to free a locallock entry
|
|
*/
|
|
static void
|
|
RemoveLocalLock(LOCALLOCK *locallock)
|
|
{
|
|
LOCKMETHODID lockmethodid = LOCALLOCK_LOCKMETHOD(*locallock);
|
|
|
|
pfree(locallock->lockOwners);
|
|
locallock->lockOwners = NULL;
|
|
locallock = (LOCALLOCK *) hash_search(LockMethodLocalHash[lockmethodid],
|
|
(void *) &(locallock->tag),
|
|
HASH_REMOVE, NULL);
|
|
if (!locallock)
|
|
elog(WARNING, "locallock table corrupted");
|
|
}
|
|
|
|
/*
|
|
* LockCheckConflicts -- test whether requested lock conflicts
|
|
* with those already granted
|
|
*
|
|
* Returns STATUS_FOUND if conflict, STATUS_OK if no conflict.
|
|
*
|
|
* NOTES:
|
|
* Here's what makes this complicated: one process's locks don't
|
|
* conflict with one another, even if they are held under different
|
|
* transaction IDs (eg, session and xact locks do not conflict).
|
|
* So, we must subtract off our own locks when determining whether the
|
|
* requested new lock conflicts with those already held.
|
|
*
|
|
* The caller can optionally pass the process's total holding counts, if
|
|
* known. If NULL is passed then these values will be computed internally.
|
|
*/
|
|
int
|
|
LockCheckConflicts(LockMethod lockMethodTable,
|
|
LOCKMODE lockmode,
|
|
LOCK *lock,
|
|
PROCLOCK *proclock,
|
|
PGPROC *proc,
|
|
int *myHolding) /* myHolding[] array or NULL */
|
|
{
|
|
int numLockModes = lockMethodTable->numLockModes;
|
|
LOCKMASK bitmask;
|
|
int i;
|
|
int localHolding[MAX_LOCKMODES];
|
|
|
|
/*
|
|
* first check for global conflicts: If no locks conflict with my
|
|
* request, then I get the lock.
|
|
*
|
|
* Checking for conflict: lock->grantMask represents the types of
|
|
* currently held locks. conflictTable[lockmode] has a bit set for
|
|
* each type of lock that conflicts with request. Bitwise compare
|
|
* tells if there is a conflict.
|
|
*/
|
|
if (!(lockMethodTable->conflictTab[lockmode] & lock->grantMask))
|
|
{
|
|
PROCLOCK_PRINT("LockCheckConflicts: no conflict", proclock);
|
|
return STATUS_OK;
|
|
}
|
|
|
|
/*
|
|
* Rats. Something conflicts. But it could still be my own lock. We
|
|
* have to construct a conflict mask that does not reflect our own
|
|
* locks. Locks held by the current process under another XID also
|
|
* count as "our own locks".
|
|
*/
|
|
if (myHolding == NULL)
|
|
{
|
|
/* Caller didn't do calculation of total holding for me */
|
|
LockCountMyLocks(proclock->tag.lock, proc, localHolding);
|
|
myHolding = localHolding;
|
|
}
|
|
|
|
/* Compute mask of lock types held by other processes */
|
|
bitmask = 0;
|
|
for (i = 1; i <= numLockModes; i++)
|
|
{
|
|
if (lock->granted[i] != myHolding[i])
|
|
bitmask |= LOCKBIT_ON(i);
|
|
}
|
|
|
|
/*
|
|
* now check again for conflicts. 'bitmask' describes the types of
|
|
* locks held by other processes. If one of these conflicts with the
|
|
* kind of lock that I want, there is a conflict and I have to sleep.
|
|
*/
|
|
if (!(lockMethodTable->conflictTab[lockmode] & bitmask))
|
|
{
|
|
/* no conflict. OK to get the lock */
|
|
PROCLOCK_PRINT("LockCheckConflicts: resolved", proclock);
|
|
return STATUS_OK;
|
|
}
|
|
|
|
PROCLOCK_PRINT("LockCheckConflicts: conflicting", proclock);
|
|
return STATUS_FOUND;
|
|
}
|
|
|
|
/*
|
|
* LockCountMyLocks --- Count total number of locks held on a given lockable
|
|
* object by a given process (under any transaction ID).
|
|
*
|
|
* XXX This could be rather slow if the process holds a large number of locks.
|
|
* Perhaps it could be sped up if we kept yet a third hashtable of per-
|
|
* process lock information. However, for the normal case where a transaction
|
|
* doesn't hold a large number of locks, keeping such a table would probably
|
|
* be a net slowdown.
|
|
*/
|
|
static void
|
|
LockCountMyLocks(SHMEM_OFFSET lockOffset, PGPROC *proc, int *myHolding)
|
|
{
|
|
SHM_QUEUE *procLocks = &(proc->procLocks);
|
|
PROCLOCK *proclock;
|
|
|
|
MemSet(myHolding, 0, MAX_LOCKMODES * sizeof(int));
|
|
|
|
proclock = (PROCLOCK *) SHMQueueNext(procLocks, procLocks,
|
|
offsetof(PROCLOCK, procLink));
|
|
|
|
while (proclock)
|
|
{
|
|
if (lockOffset == proclock->tag.lock)
|
|
{
|
|
LOCKMASK holdMask = proclock->holdMask;
|
|
int i;
|
|
|
|
for (i = 1; i < MAX_LOCKMODES; i++)
|
|
{
|
|
if (holdMask & LOCKBIT_ON(i))
|
|
myHolding[i]++;
|
|
}
|
|
}
|
|
|
|
proclock = (PROCLOCK *) SHMQueueNext(procLocks, &proclock->procLink,
|
|
offsetof(PROCLOCK, procLink));
|
|
}
|
|
}
|
|
|
|
/*
|
|
* GrantLock -- update the lock and proclock data structures to show
|
|
* the lock request has been granted.
|
|
*
|
|
* NOTE: if proc was blocked, it also needs to be removed from the wait list
|
|
* and have its waitLock/waitProcLock fields cleared. That's not done here.
|
|
*
|
|
* NOTE: the lock grant also has to be recorded in the associated LOCALLOCK
|
|
* table entry; but since we may be awaking some other process, we can't do
|
|
* that here; it's done by GrantLockLocal, instead.
|
|
*/
|
|
void
|
|
GrantLock(LOCK *lock, PROCLOCK *proclock, LOCKMODE lockmode)
|
|
{
|
|
lock->nGranted++;
|
|
lock->granted[lockmode]++;
|
|
lock->grantMask |= LOCKBIT_ON(lockmode);
|
|
if (lock->granted[lockmode] == lock->requested[lockmode])
|
|
lock->waitMask &= LOCKBIT_OFF(lockmode);
|
|
proclock->holdMask |= LOCKBIT_ON(lockmode);
|
|
LOCK_PRINT("GrantLock", lock, lockmode);
|
|
Assert((lock->nGranted > 0) && (lock->granted[lockmode] > 0));
|
|
Assert(lock->nGranted <= lock->nRequested);
|
|
}
|
|
|
|
/*
|
|
* UnGrantLock -- opposite of GrantLock.
|
|
*
|
|
* Updates the lock and proclock data structures to show that the lock
|
|
* is no longer held nor requested by the current holder.
|
|
*
|
|
* Returns true if there were any waiters waiting on the lock that
|
|
* should now be woken up with ProcLockWakeup.
|
|
*/
|
|
static bool
|
|
UnGrantLock(LOCK *lock, LOCKMODE lockmode,
|
|
PROCLOCK *proclock, LockMethod lockMethodTable)
|
|
{
|
|
bool wakeupNeeded = false;
|
|
|
|
Assert((lock->nRequested > 0) && (lock->requested[lockmode] > 0));
|
|
Assert((lock->nGranted > 0) && (lock->granted[lockmode] > 0));
|
|
Assert(lock->nGranted <= lock->nRequested);
|
|
|
|
/*
|
|
* fix the general lock stats
|
|
*/
|
|
lock->nRequested--;
|
|
lock->requested[lockmode]--;
|
|
lock->nGranted--;
|
|
lock->granted[lockmode]--;
|
|
|
|
if (lock->granted[lockmode] == 0)
|
|
{
|
|
/* change the conflict mask. No more of this lock type. */
|
|
lock->grantMask &= LOCKBIT_OFF(lockmode);
|
|
}
|
|
|
|
LOCK_PRINT("UnGrantLock: updated", lock, lockmode);
|
|
Assert((lock->nRequested >= 0) && (lock->requested[lockmode] >= 0));
|
|
Assert((lock->nGranted >= 0) && (lock->granted[lockmode] >= 0));
|
|
Assert(lock->nGranted <= lock->nRequested);
|
|
|
|
/*
|
|
* We need only run ProcLockWakeup if the released lock conflicts with
|
|
* at least one of the lock types requested by waiter(s). Otherwise
|
|
* whatever conflict made them wait must still exist. NOTE: before
|
|
* MVCC, we could skip wakeup if lock->granted[lockmode] was still
|
|
* positive. But that's not true anymore, because the remaining
|
|
* granted locks might belong to some waiter, who could now be
|
|
* awakened because he doesn't conflict with his own locks.
|
|
*/
|
|
if (lockMethodTable->conflictTab[lockmode] & lock->waitMask)
|
|
wakeupNeeded = true;
|
|
|
|
/*
|
|
* Now fix the per-proclock state.
|
|
*/
|
|
proclock->holdMask &= LOCKBIT_OFF(lockmode);
|
|
PROCLOCK_PRINT("UnGrantLock: updated", proclock);
|
|
|
|
return wakeupNeeded;
|
|
}
|
|
|
|
/*
|
|
* GrantLockLocal -- update the locallock data structures to show
|
|
* the lock request has been granted.
|
|
*
|
|
* We expect that LockAcquire made sure there is room to add a new
|
|
* ResourceOwner entry.
|
|
*/
|
|
static void
|
|
GrantLockLocal(LOCALLOCK *locallock, ResourceOwner owner)
|
|
{
|
|
LOCALLOCKOWNER *lockOwners = locallock->lockOwners;
|
|
int i;
|
|
|
|
Assert(locallock->numLockOwners < locallock->maxLockOwners);
|
|
/* Count the total */
|
|
locallock->nLocks++;
|
|
/* Count the per-owner lock */
|
|
for (i = 0; i < locallock->numLockOwners; i++)
|
|
{
|
|
if (lockOwners[i].owner == owner)
|
|
{
|
|
lockOwners[i].nLocks++;
|
|
return;
|
|
}
|
|
}
|
|
lockOwners[i].owner = owner;
|
|
lockOwners[i].nLocks = 1;
|
|
locallock->numLockOwners++;
|
|
}
|
|
|
|
/*
|
|
* GrantAwaitedLock -- call GrantLockLocal for the lock we are doing
|
|
* WaitOnLock on.
|
|
*
|
|
* proc.c needs this for the case where we are booted off the lock by
|
|
* timeout, but discover that someone granted us the lock anyway.
|
|
*
|
|
* We could just export GrantLockLocal, but that would require including
|
|
* resowner.h in lock.h, which creates circularity.
|
|
*/
|
|
void
|
|
GrantAwaitedLock(void)
|
|
{
|
|
GrantLockLocal(awaitedLock, awaitedOwner);
|
|
}
|
|
|
|
/*
|
|
* WaitOnLock -- wait to acquire a lock
|
|
*
|
|
* Caller must have set MyProc->heldLocks to reflect locks already held
|
|
* on the lockable object by this process (under all XIDs).
|
|
*
|
|
* The locktable's masterLock must be held at entry.
|
|
*/
|
|
static int
|
|
WaitOnLock(LOCKMETHODID lockmethodid, LOCALLOCK *locallock,
|
|
ResourceOwner owner)
|
|
{
|
|
LockMethod lockMethodTable = LockMethods[lockmethodid];
|
|
char *new_status,
|
|
*old_status;
|
|
|
|
Assert(lockmethodid < NumLockMethods);
|
|
|
|
LOCK_PRINT("WaitOnLock: sleeping on lock",
|
|
locallock->lock, locallock->tag.mode);
|
|
|
|
old_status = pstrdup(get_ps_display());
|
|
new_status = (char *) palloc(strlen(old_status) + 10);
|
|
strcpy(new_status, old_status);
|
|
strcat(new_status, " waiting");
|
|
set_ps_display(new_status);
|
|
|
|
awaitedLock = locallock;
|
|
awaitedOwner = owner;
|
|
|
|
/*
|
|
* NOTE: Think not to put any shared-state cleanup after the call to
|
|
* ProcSleep, in either the normal or failure path. The lock state
|
|
* must be fully set by the lock grantor, or by CheckDeadLock if we
|
|
* give up waiting for the lock. This is necessary because of the
|
|
* possibility that a cancel/die interrupt will interrupt ProcSleep
|
|
* after someone else grants us the lock, but before we've noticed it.
|
|
* Hence, after granting, the locktable state must fully reflect the
|
|
* fact that we own the lock; we can't do additional work on return.
|
|
* Contrariwise, if we fail, any cleanup must happen in xact abort
|
|
* processing, not here, to ensure it will also happen in the
|
|
* cancel/die case.
|
|
*/
|
|
|
|
if (ProcSleep(lockMethodTable,
|
|
locallock->tag.mode,
|
|
locallock->lock,
|
|
locallock->proclock) != STATUS_OK)
|
|
{
|
|
/*
|
|
* We failed as a result of a deadlock, see CheckDeadLock(). Quit
|
|
* now. Removal of the proclock and lock objects, if no longer
|
|
* needed, will happen in xact cleanup (see above for motivation).
|
|
*/
|
|
awaitedLock = NULL;
|
|
LOCK_PRINT("WaitOnLock: aborting on lock",
|
|
locallock->lock, locallock->tag.mode);
|
|
LWLockRelease(lockMethodTable->masterLock);
|
|
|
|
/*
|
|
* Now that we aren't holding the LockMgrLock, we can give an
|
|
* error report including details about the detected deadlock.
|
|
*/
|
|
DeadLockReport();
|
|
/* not reached */
|
|
}
|
|
|
|
awaitedLock = NULL;
|
|
|
|
set_ps_display(old_status);
|
|
pfree(old_status);
|
|
pfree(new_status);
|
|
|
|
LOCK_PRINT("WaitOnLock: wakeup on lock",
|
|
locallock->lock, locallock->tag.mode);
|
|
return STATUS_OK;
|
|
}
|
|
|
|
/*
|
|
* Remove a proc from the wait-queue it is on
|
|
* (caller must know it is on one).
|
|
*
|
|
* Locktable lock must be held by caller.
|
|
*
|
|
* NB: this does not remove the process' proclock object, nor the lock object,
|
|
* even though their counts might now have gone to zero. That will happen
|
|
* during a subsequent LockReleaseAll call, which we expect will happen
|
|
* during transaction cleanup. (Removal of a proc from its wait queue by
|
|
* this routine can only happen if we are aborting the transaction.)
|
|
*/
|
|
void
|
|
RemoveFromWaitQueue(PGPROC *proc)
|
|
{
|
|
LOCK *waitLock = proc->waitLock;
|
|
LOCKMODE lockmode = proc->waitLockMode;
|
|
|
|
/* Make sure proc is waiting */
|
|
Assert(proc->links.next != INVALID_OFFSET);
|
|
Assert(waitLock);
|
|
Assert(waitLock->waitProcs.size > 0);
|
|
|
|
/* Remove proc from lock's wait queue */
|
|
SHMQueueDelete(&(proc->links));
|
|
waitLock->waitProcs.size--;
|
|
|
|
/* Undo increments of request counts by waiting process */
|
|
Assert(waitLock->nRequested > 0);
|
|
Assert(waitLock->nRequested > proc->waitLock->nGranted);
|
|
waitLock->nRequested--;
|
|
Assert(waitLock->requested[lockmode] > 0);
|
|
waitLock->requested[lockmode]--;
|
|
/* don't forget to clear waitMask bit if appropriate */
|
|
if (waitLock->granted[lockmode] == waitLock->requested[lockmode])
|
|
waitLock->waitMask &= LOCKBIT_OFF(lockmode);
|
|
|
|
/* Clean up the proc's own state */
|
|
proc->waitLock = NULL;
|
|
proc->waitProcLock = NULL;
|
|
|
|
/* See if any other waiters for the lock can be woken up now */
|
|
ProcLockWakeup(GetLocksMethodTable(waitLock), waitLock);
|
|
}
|
|
|
|
/*
|
|
* LockRelease -- look up 'locktag' in lock table 'lockmethodid' and
|
|
* release one 'lockmode' lock on it.
|
|
*
|
|
* Side Effects: find any waiting processes that are now wakable,
|
|
* grant them their requested locks and awaken them.
|
|
* (We have to grant the lock here to avoid a race between
|
|
* the waking process and any new process to
|
|
* come along and request the lock.)
|
|
*/
|
|
bool
|
|
LockRelease(LOCKMETHODID lockmethodid, LOCKTAG *locktag,
|
|
TransactionId xid, LOCKMODE lockmode)
|
|
{
|
|
LOCALLOCKTAG localtag;
|
|
LOCALLOCK *locallock;
|
|
LOCK *lock;
|
|
PROCLOCK *proclock;
|
|
LWLockId masterLock;
|
|
LockMethod lockMethodTable;
|
|
bool wakeupNeeded = false;
|
|
|
|
#ifdef LOCK_DEBUG
|
|
if (lockmethodid == USER_LOCKMETHOD && Trace_userlocks)
|
|
elog(LOG, "LockRelease: user lock tag [%u] %d", locktag->objId.blkno, lockmode);
|
|
#endif
|
|
|
|
/* ???????? This must be changed when short term locks will be used */
|
|
locktag->lockmethodid = lockmethodid;
|
|
|
|
Assert(lockmethodid < NumLockMethods);
|
|
lockMethodTable = LockMethods[lockmethodid];
|
|
if (!lockMethodTable)
|
|
{
|
|
elog(WARNING, "lockMethodTable is null in LockRelease");
|
|
return FALSE;
|
|
}
|
|
|
|
/*
|
|
* Find the LOCALLOCK entry for this lock and lockmode
|
|
*/
|
|
MemSet(&localtag, 0, sizeof(localtag)); /* must clear padding */
|
|
localtag.lock = *locktag;
|
|
localtag.xid = xid;
|
|
localtag.mode = lockmode;
|
|
|
|
locallock = (LOCALLOCK *) hash_search(LockMethodLocalHash[lockmethodid],
|
|
(void *) &localtag,
|
|
HASH_FIND, NULL);
|
|
|
|
/*
|
|
* let the caller print its own error message, too. Do not
|
|
* ereport(ERROR).
|
|
*/
|
|
if (!locallock || locallock->nLocks <= 0)
|
|
{
|
|
elog(WARNING, "you don't own a lock of type %s",
|
|
lock_mode_names[lockmode]);
|
|
return FALSE;
|
|
}
|
|
|
|
/*
|
|
* Decrease the count for the resource owner.
|
|
*/
|
|
{
|
|
LOCALLOCKOWNER *lockOwners = locallock->lockOwners;
|
|
ResourceOwner owner;
|
|
int i;
|
|
|
|
/* Session locks and user locks are not transactional */
|
|
if (xid != InvalidTransactionId &&
|
|
lockmethodid == DEFAULT_LOCKMETHOD)
|
|
owner = CurrentResourceOwner;
|
|
else
|
|
owner = NULL;
|
|
|
|
for (i = locallock->numLockOwners - 1; i >= 0; i--)
|
|
{
|
|
if (lockOwners[i].owner == owner)
|
|
{
|
|
Assert(lockOwners[i].nLocks > 0);
|
|
if (--lockOwners[i].nLocks == 0)
|
|
{
|
|
/* compact out unused slot */
|
|
locallock->numLockOwners--;
|
|
if (i < locallock->numLockOwners)
|
|
lockOwners[i] = lockOwners[locallock->numLockOwners];
|
|
}
|
|
break;
|
|
}
|
|
}
|
|
if (i < 0)
|
|
{
|
|
/* don't release a lock belonging to another owner */
|
|
elog(WARNING, "you don't own a lock of type %s",
|
|
lock_mode_names[lockmode]);
|
|
return FALSE;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Decrease the total local count. If we're still holding the lock,
|
|
* we're done.
|
|
*/
|
|
locallock->nLocks--;
|
|
|
|
if (locallock->nLocks > 0)
|
|
return TRUE;
|
|
|
|
/*
|
|
* Otherwise we've got to mess with the shared lock table.
|
|
*/
|
|
masterLock = lockMethodTable->masterLock;
|
|
|
|
LWLockAcquire(masterLock, LW_EXCLUSIVE);
|
|
|
|
/*
|
|
* We don't need to re-find the lock or proclock, since we kept their
|
|
* addresses in the locallock table, and they couldn't have been
|
|
* removed while we were holding a lock on them.
|
|
*/
|
|
lock = locallock->lock;
|
|
LOCK_PRINT("LockRelease: found", lock, lockmode);
|
|
proclock = locallock->proclock;
|
|
PROCLOCK_PRINT("LockRelease: found", proclock);
|
|
|
|
/*
|
|
* Double-check that we are actually holding a lock of the type we
|
|
* want to release.
|
|
*/
|
|
if (!(proclock->holdMask & LOCKBIT_ON(lockmode)))
|
|
{
|
|
PROCLOCK_PRINT("LockRelease: WRONGTYPE", proclock);
|
|
LWLockRelease(masterLock);
|
|
elog(WARNING, "you don't own a lock of type %s",
|
|
lock_mode_names[lockmode]);
|
|
RemoveLocalLock(locallock);
|
|
return FALSE;
|
|
}
|
|
|
|
wakeupNeeded = UnGrantLock(lock, lockmode, proclock, lockMethodTable);
|
|
|
|
/*
|
|
* If this was my last hold on this lock, delete my entry in the
|
|
* proclock table.
|
|
*/
|
|
if (proclock->holdMask == 0)
|
|
{
|
|
PROCLOCK_PRINT("LockRelease: deleting", proclock);
|
|
SHMQueueDelete(&proclock->lockLink);
|
|
SHMQueueDelete(&proclock->procLink);
|
|
proclock = (PROCLOCK *) hash_search(LockMethodProcLockHash[lockmethodid],
|
|
(void *) &(proclock->tag),
|
|
HASH_REMOVE, NULL);
|
|
if (!proclock)
|
|
{
|
|
LWLockRelease(masterLock);
|
|
elog(WARNING, "proclock table corrupted");
|
|
RemoveLocalLock(locallock);
|
|
return FALSE;
|
|
}
|
|
}
|
|
|
|
if (lock->nRequested == 0)
|
|
{
|
|
/*
|
|
* We've just released the last lock, so garbage-collect the lock
|
|
* object.
|
|
*/
|
|
Assert(SHMQueueEmpty(&(lock->procLocks)));
|
|
lock = (LOCK *) hash_search(LockMethodLockHash[lockmethodid],
|
|
(void *) &(lock->tag),
|
|
HASH_REMOVE, NULL);
|
|
if (!lock)
|
|
{
|
|
LWLockRelease(masterLock);
|
|
elog(WARNING, "lock table corrupted");
|
|
RemoveLocalLock(locallock);
|
|
return FALSE;
|
|
}
|
|
}
|
|
else
|
|
{
|
|
/*
|
|
* Wake up waiters if needed.
|
|
*/
|
|
if (wakeupNeeded)
|
|
ProcLockWakeup(lockMethodTable, lock);
|
|
}
|
|
|
|
LWLockRelease(masterLock);
|
|
|
|
RemoveLocalLock(locallock);
|
|
return TRUE;
|
|
}
|
|
|
|
/*
|
|
* LockReleaseAll -- Release all locks of the specified lock method that
|
|
* are held by the current process.
|
|
*
|
|
* Well, not necessarily *all* locks. The available behaviors are:
|
|
*
|
|
* allxids == true: release all locks regardless of transaction
|
|
* affiliation.
|
|
*
|
|
* allxids == false: release all locks with Xid != 0
|
|
* (zero is the Xid used for "session" locks).
|
|
*/
|
|
bool
|
|
LockReleaseAll(LOCKMETHODID lockmethodid, bool allxids)
|
|
{
|
|
HASH_SEQ_STATUS status;
|
|
SHM_QUEUE *procLocks = &(MyProc->procLocks);
|
|
LWLockId masterLock;
|
|
LockMethod lockMethodTable;
|
|
int i,
|
|
numLockModes;
|
|
LOCALLOCK *locallock;
|
|
PROCLOCK *proclock;
|
|
LOCK *lock;
|
|
|
|
#ifdef LOCK_DEBUG
|
|
if (lockmethodid == USER_LOCKMETHOD ? Trace_userlocks : Trace_locks)
|
|
elog(LOG, "LockReleaseAll: lockmethod=%d", lockmethodid);
|
|
#endif
|
|
|
|
Assert(lockmethodid < NumLockMethods);
|
|
lockMethodTable = LockMethods[lockmethodid];
|
|
if (!lockMethodTable)
|
|
{
|
|
elog(WARNING, "bad lock method: %d", lockmethodid);
|
|
return FALSE;
|
|
}
|
|
|
|
numLockModes = lockMethodTable->numLockModes;
|
|
masterLock = lockMethodTable->masterLock;
|
|
|
|
/*
|
|
* First we run through the locallock table and get rid of unwanted
|
|
* entries, then we scan the process's proclocks and get rid of those.
|
|
* We do this separately because we may have multiple locallock
|
|
* entries pointing to the same proclock, and we daren't end up with
|
|
* any dangling pointers.
|
|
*/
|
|
hash_seq_init(&status, LockMethodLocalHash[lockmethodid]);
|
|
|
|
while ((locallock = (LOCALLOCK *) hash_seq_search(&status)) != NULL)
|
|
{
|
|
if (locallock->proclock == NULL || locallock->lock == NULL)
|
|
{
|
|
/*
|
|
* We must've run out of shared memory while trying to set up
|
|
* this lock. Just forget the local entry.
|
|
*/
|
|
Assert(locallock->nLocks == 0);
|
|
RemoveLocalLock(locallock);
|
|
continue;
|
|
}
|
|
|
|
/* Ignore items that are not of the lockmethod to be removed */
|
|
if (LOCALLOCK_LOCKMETHOD(*locallock) != lockmethodid)
|
|
continue;
|
|
|
|
/*
|
|
* Ignore locks with Xid=0 unless we are asked to release all
|
|
* locks
|
|
*/
|
|
if (TransactionIdEquals(locallock->tag.xid, InvalidTransactionId)
|
|
&& !allxids)
|
|
continue;
|
|
|
|
RemoveLocalLock(locallock);
|
|
}
|
|
|
|
LWLockAcquire(masterLock, LW_EXCLUSIVE);
|
|
|
|
proclock = (PROCLOCK *) SHMQueueNext(procLocks, procLocks,
|
|
offsetof(PROCLOCK, procLink));
|
|
|
|
while (proclock)
|
|
{
|
|
bool wakeupNeeded = false;
|
|
PROCLOCK *nextHolder;
|
|
|
|
/* Get link first, since we may unlink/delete this proclock */
|
|
nextHolder = (PROCLOCK *) SHMQueueNext(procLocks, &proclock->procLink,
|
|
offsetof(PROCLOCK, procLink));
|
|
|
|
Assert(proclock->tag.proc == MAKE_OFFSET(MyProc));
|
|
|
|
lock = (LOCK *) MAKE_PTR(proclock->tag.lock);
|
|
|
|
/* Ignore items that are not of the lockmethod to be removed */
|
|
if (LOCK_LOCKMETHOD(*lock) != lockmethodid)
|
|
goto next_item;
|
|
|
|
/*
|
|
* Ignore locks with Xid=0 unless we are asked to release all
|
|
* locks
|
|
*/
|
|
if (TransactionIdEquals(proclock->tag.xid, InvalidTransactionId)
|
|
&& !allxids)
|
|
goto next_item;
|
|
|
|
PROCLOCK_PRINT("LockReleaseAll", proclock);
|
|
LOCK_PRINT("LockReleaseAll", lock, 0);
|
|
Assert(lock->nRequested >= 0);
|
|
Assert(lock->nGranted >= 0);
|
|
Assert(lock->nGranted <= lock->nRequested);
|
|
Assert((proclock->holdMask & ~lock->grantMask) == 0);
|
|
|
|
/*
|
|
* fix the general lock stats
|
|
*/
|
|
if (proclock->holdMask)
|
|
{
|
|
for (i = 1; i <= numLockModes; i++)
|
|
{
|
|
if (proclock->holdMask & LOCKBIT_ON(i))
|
|
wakeupNeeded |= UnGrantLock(lock, i, proclock,
|
|
lockMethodTable);
|
|
}
|
|
}
|
|
Assert((lock->nRequested >= 0) && (lock->nGranted >= 0));
|
|
Assert(lock->nGranted <= lock->nRequested);
|
|
LOCK_PRINT("LockReleaseAll: updated", lock, 0);
|
|
|
|
PROCLOCK_PRINT("LockReleaseAll: deleting", proclock);
|
|
|
|
/*
|
|
* Remove the proclock entry from the linked lists
|
|
*/
|
|
SHMQueueDelete(&proclock->lockLink);
|
|
SHMQueueDelete(&proclock->procLink);
|
|
|
|
/*
|
|
* remove the proclock entry from the hashtable
|
|
*/
|
|
proclock = (PROCLOCK *) hash_search(LockMethodProcLockHash[lockmethodid],
|
|
(void *) &(proclock->tag),
|
|
HASH_REMOVE,
|
|
NULL);
|
|
if (!proclock)
|
|
{
|
|
LWLockRelease(masterLock);
|
|
elog(WARNING, "proclock table corrupted");
|
|
return FALSE;
|
|
}
|
|
|
|
if (lock->nRequested == 0)
|
|
{
|
|
/*
|
|
* We've just released the last lock, so garbage-collect the
|
|
* lock object.
|
|
*/
|
|
LOCK_PRINT("LockReleaseAll: deleting", lock, 0);
|
|
Assert(SHMQueueEmpty(&(lock->procLocks)));
|
|
lock = (LOCK *) hash_search(LockMethodLockHash[lockmethodid],
|
|
(void *) &(lock->tag),
|
|
HASH_REMOVE, NULL);
|
|
if (!lock)
|
|
{
|
|
LWLockRelease(masterLock);
|
|
elog(WARNING, "lock table corrupted");
|
|
return FALSE;
|
|
}
|
|
}
|
|
else if (wakeupNeeded)
|
|
ProcLockWakeup(lockMethodTable, lock);
|
|
|
|
next_item:
|
|
proclock = nextHolder;
|
|
}
|
|
|
|
LWLockRelease(masterLock);
|
|
|
|
#ifdef LOCK_DEBUG
|
|
if (lockmethodid == USER_LOCKMETHOD ? Trace_userlocks : Trace_locks)
|
|
elog(LOG, "LockReleaseAll done");
|
|
#endif
|
|
|
|
return TRUE;
|
|
}
|
|
|
|
/*
|
|
* LockReleaseCurrentOwner
|
|
* Release all locks belonging to CurrentResourceOwner
|
|
*
|
|
* Only DEFAULT_LOCKMETHOD locks can belong to a resource owner.
|
|
*/
|
|
void
|
|
LockReleaseCurrentOwner(void)
|
|
{
|
|
HASH_SEQ_STATUS status;
|
|
LOCALLOCK *locallock;
|
|
LOCALLOCKOWNER *lockOwners;
|
|
int i;
|
|
|
|
hash_seq_init(&status, LockMethodLocalHash[DEFAULT_LOCKMETHOD]);
|
|
|
|
while ((locallock = (LOCALLOCK *) hash_seq_search(&status)) != NULL)
|
|
{
|
|
/* Ignore items that must be nontransactional */
|
|
if (LOCALLOCK_LOCKMETHOD(*locallock) != DEFAULT_LOCKMETHOD)
|
|
continue;
|
|
if (TransactionIdEquals(locallock->tag.xid, InvalidTransactionId))
|
|
continue;
|
|
|
|
/* Scan to see if there are any locks belonging to current owner */
|
|
lockOwners = locallock->lockOwners;
|
|
for (i = locallock->numLockOwners - 1; i >= 0; i--)
|
|
{
|
|
if (lockOwners[i].owner == CurrentResourceOwner)
|
|
{
|
|
Assert(lockOwners[i].nLocks > 0);
|
|
if (lockOwners[i].nLocks < locallock->nLocks)
|
|
{
|
|
/*
|
|
* We will still hold this lock after forgetting this
|
|
* ResourceOwner.
|
|
*/
|
|
locallock->nLocks -= lockOwners[i].nLocks;
|
|
/* compact out unused slot */
|
|
locallock->numLockOwners--;
|
|
if (i < locallock->numLockOwners)
|
|
lockOwners[i] = lockOwners[locallock->numLockOwners];
|
|
}
|
|
else
|
|
{
|
|
Assert(lockOwners[i].nLocks == locallock->nLocks);
|
|
/* We want to call LockRelease just once */
|
|
lockOwners[i].nLocks = 1;
|
|
locallock->nLocks = 1;
|
|
if (!LockRelease(DEFAULT_LOCKMETHOD,
|
|
&locallock->tag.lock,
|
|
locallock->tag.xid,
|
|
locallock->tag.mode))
|
|
elog(WARNING, "LockReleaseCurrentOwner: failed??");
|
|
}
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/*
|
|
* LockReassignCurrentOwner
|
|
* Reassign all locks belonging to CurrentResourceOwner to belong
|
|
* to its parent resource owner
|
|
*/
|
|
void
|
|
LockReassignCurrentOwner(void)
|
|
{
|
|
ResourceOwner parent = ResourceOwnerGetParent(CurrentResourceOwner);
|
|
HASH_SEQ_STATUS status;
|
|
LOCALLOCK *locallock;
|
|
LOCALLOCKOWNER *lockOwners;
|
|
|
|
Assert(parent != NULL);
|
|
|
|
hash_seq_init(&status, LockMethodLocalHash[DEFAULT_LOCKMETHOD]);
|
|
|
|
while ((locallock = (LOCALLOCK *) hash_seq_search(&status)) != NULL)
|
|
{
|
|
int i;
|
|
int ic = -1;
|
|
int ip = -1;
|
|
|
|
/* Ignore items that must be nontransactional */
|
|
if (LOCALLOCK_LOCKMETHOD(*locallock) != DEFAULT_LOCKMETHOD)
|
|
continue;
|
|
if (TransactionIdEquals(locallock->tag.xid, InvalidTransactionId))
|
|
continue;
|
|
|
|
/*
|
|
* Scan to see if there are any locks belonging to current owner
|
|
* or its parent
|
|
*/
|
|
lockOwners = locallock->lockOwners;
|
|
for (i = locallock->numLockOwners - 1; i >= 0; i--)
|
|
{
|
|
if (lockOwners[i].owner == CurrentResourceOwner)
|
|
ic = i;
|
|
else if (lockOwners[i].owner == parent)
|
|
ip = i;
|
|
}
|
|
|
|
if (ic < 0)
|
|
continue; /* no current locks */
|
|
|
|
if (ip < 0)
|
|
{
|
|
/* Parent has no slot, so just give it child's slot */
|
|
lockOwners[ic].owner = parent;
|
|
}
|
|
else
|
|
{
|
|
/* Merge child's count with parent's */
|
|
lockOwners[ip].nLocks += lockOwners[ic].nLocks;
|
|
/* compact out unused slot */
|
|
locallock->numLockOwners--;
|
|
if (ic < locallock->numLockOwners)
|
|
lockOwners[ic] = lockOwners[locallock->numLockOwners];
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
/*
|
|
* Estimate shared-memory space used for lock tables
|
|
*/
|
|
int
|
|
LockShmemSize(int maxBackends)
|
|
{
|
|
int size = 0;
|
|
long max_table_size = NLOCKENTS(maxBackends);
|
|
|
|
/* lock method headers */
|
|
size += MAX_LOCK_METHODS * MAXALIGN(sizeof(LockMethodData));
|
|
|
|
/* lockHash table */
|
|
size += hash_estimate_size(max_table_size, sizeof(LOCK));
|
|
|
|
/* proclockHash table */
|
|
size += hash_estimate_size(max_table_size, sizeof(PROCLOCK));
|
|
|
|
/*
|
|
* Note we count only one pair of hash tables, since the userlocks
|
|
* table actually overlays the main one.
|
|
*
|
|
* Since the lockHash entry count above is only an estimate, add 10%
|
|
* safety margin.
|
|
*/
|
|
size += size / 10;
|
|
|
|
return size;
|
|
}
|
|
|
|
/*
|
|
* GetLockStatusData - Return a summary of the lock manager's internal
|
|
* status, for use in a user-level reporting function.
|
|
*
|
|
* The return data consists of an array of PROCLOCK objects, with the
|
|
* associated PGPROC and LOCK objects for each. Note that multiple
|
|
* copies of the same PGPROC and/or LOCK objects are likely to appear.
|
|
* It is the caller's responsibility to match up duplicates if wanted.
|
|
*
|
|
* The design goal is to hold the LockMgrLock for as short a time as possible;
|
|
* thus, this function simply makes a copy of the necessary data and releases
|
|
* the lock, allowing the caller to contemplate and format the data for as
|
|
* long as it pleases.
|
|
*/
|
|
LockData *
|
|
GetLockStatusData(void)
|
|
{
|
|
LockData *data;
|
|
HTAB *proclockTable;
|
|
PROCLOCK *proclock;
|
|
HASH_SEQ_STATUS seqstat;
|
|
int i;
|
|
|
|
data = (LockData *) palloc(sizeof(LockData));
|
|
|
|
LWLockAcquire(LockMgrLock, LW_EXCLUSIVE);
|
|
|
|
proclockTable = LockMethodProcLockHash[DEFAULT_LOCKMETHOD];
|
|
|
|
data->nelements = i = proclockTable->hctl->nentries;
|
|
|
|
data->proclockaddrs = (SHMEM_OFFSET *) palloc(sizeof(SHMEM_OFFSET) * i);
|
|
data->proclocks = (PROCLOCK *) palloc(sizeof(PROCLOCK) * i);
|
|
data->procs = (PGPROC *) palloc(sizeof(PGPROC) * i);
|
|
data->locks = (LOCK *) palloc(sizeof(LOCK) * i);
|
|
|
|
hash_seq_init(&seqstat, proclockTable);
|
|
|
|
i = 0;
|
|
while ((proclock = hash_seq_search(&seqstat)))
|
|
{
|
|
PGPROC *proc = (PGPROC *) MAKE_PTR(proclock->tag.proc);
|
|
LOCK *lock = (LOCK *) MAKE_PTR(proclock->tag.lock);
|
|
|
|
data->proclockaddrs[i] = MAKE_OFFSET(proclock);
|
|
memcpy(&(data->proclocks[i]), proclock, sizeof(PROCLOCK));
|
|
memcpy(&(data->procs[i]), proc, sizeof(PGPROC));
|
|
memcpy(&(data->locks[i]), lock, sizeof(LOCK));
|
|
|
|
i++;
|
|
}
|
|
|
|
LWLockRelease(LockMgrLock);
|
|
|
|
Assert(i == data->nelements);
|
|
|
|
return data;
|
|
}
|
|
|
|
/* Provide the textual name of any lock mode */
|
|
const char *
|
|
GetLockmodeName(LOCKMODE mode)
|
|
{
|
|
Assert(mode <= MAX_LOCKMODES);
|
|
return lock_mode_names[mode];
|
|
}
|
|
|
|
#ifdef LOCK_DEBUG
|
|
/*
|
|
* Dump all locks in the MyProc->procLocks list.
|
|
*
|
|
* Must have already acquired the masterLock.
|
|
*/
|
|
void
|
|
DumpLocks(void)
|
|
{
|
|
PGPROC *proc;
|
|
SHM_QUEUE *procLocks;
|
|
PROCLOCK *proclock;
|
|
LOCK *lock;
|
|
int lockmethodid = DEFAULT_LOCKMETHOD;
|
|
LockMethod lockMethodTable;
|
|
|
|
proc = MyProc;
|
|
if (proc == NULL)
|
|
return;
|
|
|
|
procLocks = &proc->procLocks;
|
|
|
|
Assert(lockmethodid < NumLockMethods);
|
|
lockMethodTable = LockMethods[lockmethodid];
|
|
if (!lockMethodTable)
|
|
return;
|
|
|
|
if (proc->waitLock)
|
|
LOCK_PRINT("DumpLocks: waiting on", proc->waitLock, 0);
|
|
|
|
proclock = (PROCLOCK *) SHMQueueNext(procLocks, procLocks,
|
|
offsetof(PROCLOCK, procLink));
|
|
|
|
while (proclock)
|
|
{
|
|
Assert(proclock->tag.proc == MAKE_OFFSET(proc));
|
|
|
|
lock = (LOCK *) MAKE_PTR(proclock->tag.lock);
|
|
|
|
PROCLOCK_PRINT("DumpLocks", proclock);
|
|
LOCK_PRINT("DumpLocks", lock, 0);
|
|
|
|
proclock = (PROCLOCK *) SHMQueueNext(procLocks, &proclock->procLink,
|
|
offsetof(PROCLOCK, procLink));
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Dump all postgres locks. Must have already acquired the masterLock.
|
|
*/
|
|
void
|
|
DumpAllLocks(void)
|
|
{
|
|
PGPROC *proc;
|
|
PROCLOCK *proclock;
|
|
LOCK *lock;
|
|
int lockmethodid = DEFAULT_LOCKMETHOD;
|
|
LockMethod lockMethodTable;
|
|
HTAB *proclockTable;
|
|
HASH_SEQ_STATUS status;
|
|
|
|
proc = MyProc;
|
|
if (proc == NULL)
|
|
return;
|
|
|
|
Assert(lockmethodid < NumLockMethods);
|
|
lockMethodTable = LockMethods[lockmethodid];
|
|
if (!lockMethodTable)
|
|
return;
|
|
|
|
proclockTable = LockMethodProcLockHash[lockmethodid];
|
|
|
|
if (proc->waitLock)
|
|
LOCK_PRINT("DumpAllLocks: waiting on", proc->waitLock, 0);
|
|
|
|
hash_seq_init(&status, proclockTable);
|
|
while ((proclock = (PROCLOCK *) hash_seq_search(&status)) != NULL)
|
|
{
|
|
PROCLOCK_PRINT("DumpAllLocks", proclock);
|
|
|
|
if (proclock->tag.lock)
|
|
{
|
|
lock = (LOCK *) MAKE_PTR(proclock->tag.lock);
|
|
LOCK_PRINT("DumpAllLocks", lock, 0);
|
|
}
|
|
else
|
|
elog(LOG, "DumpAllLocks: proclock->tag.lock = NULL");
|
|
}
|
|
}
|
|
|
|
#endif /* LOCK_DEBUG */
|