/*------------------------------------------------------------------------- * * lock.c * POSTGRES low-level lock mechanism * * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * * IDENTIFICATION * $PostgreSQL: pgsql/src/backend/storage/lmgr/lock.c,v 1.146 2005/02/04 02:04:53 neilc Exp $ * * NOTES * Outside modules can create a lock table and acquire/release * locks. A lock table is a shared memory hash table. When * a process tries to acquire a lock of a type that conflicts * with existing locks, it is put to sleep using the routines * in storage/lmgr/proc.c. * * For the most part, this code should be invoked via lmgr.c * or another lock-management module, not directly. * * Interface: * * LockAcquire(), LockRelease(), LockMethodTableInit(), * LockMethodTableRename(), LockReleaseAll(), * LockCheckConflicts(), GrantLock() * *------------------------------------------------------------------------- */ #include "postgres.h" #include #include #include "access/xact.h" #include "miscadmin.h" #include "storage/proc.h" #include "utils/memutils.h" #include "utils/ps_status.h" #include "utils/resowner.h" /* This configuration variable is used to set the lock table size */ int max_locks_per_xact; /* set by guc.c */ #define NLOCKENTS(maxBackends) (max_locks_per_xact * (maxBackends)) /* * map from lock method id to the lock table data structures */ static LockMethod LockMethods[MAX_LOCK_METHODS]; static HTAB *LockMethodLockHash[MAX_LOCK_METHODS]; static HTAB *LockMethodProcLockHash[MAX_LOCK_METHODS]; static HTAB *LockMethodLocalHash[MAX_LOCK_METHODS]; /* exported so lmgr.c can initialize it */ int NumLockMethods; /* private state for GrantAwaitedLock */ static LOCALLOCK *awaitedLock; static ResourceOwner awaitedOwner; static const char *const lock_mode_names[] = { "INVALID", "AccessShareLock", "RowShareLock", "RowExclusiveLock", "ShareUpdateExclusiveLock", "ShareLock", "ShareRowExclusiveLock", "ExclusiveLock", "AccessExclusiveLock" }; #ifdef LOCK_DEBUG /*------ * The following configuration options are available for lock debugging: * * TRACE_LOCKS -- give a bunch of output what's going on in this file * TRACE_USERLOCKS -- same but for user locks * TRACE_LOCK_OIDMIN-- do not trace locks for tables below this oid * (use to avoid output on system tables) * TRACE_LOCK_TABLE -- trace locks on this table (oid) unconditionally * DEBUG_DEADLOCKS -- currently dumps locks at untimely occasions ;) * * Furthermore, but in storage/lmgr/lwlock.c: * TRACE_LWLOCKS -- trace lightweight locks (pretty useless) * * Define LOCK_DEBUG at compile time to get all these enabled. * -------- */ int Trace_lock_oidmin = BootstrapObjectIdData; bool Trace_locks = false; bool Trace_userlocks = false; int Trace_lock_table = 0; bool Debug_deadlocks = false; inline static bool LOCK_DEBUG_ENABLED(const LOCK *lock) { return (((LOCK_LOCKMETHOD(*lock) == DEFAULT_LOCKMETHOD && Trace_locks) || (LOCK_LOCKMETHOD(*lock) == USER_LOCKMETHOD && Trace_userlocks)) && (lock->tag.relId >= (Oid) Trace_lock_oidmin)) || (Trace_lock_table && (lock->tag.relId == Trace_lock_table)); } inline static void LOCK_PRINT(const char *where, const LOCK *lock, LOCKMODE type) { if (LOCK_DEBUG_ENABLED(lock)) elog(LOG, "%s: lock(%lx) tbl(%d) rel(%u) db(%u) obj(%u) grantMask(%x) " "req(%d,%d,%d,%d,%d,%d,%d)=%d " "grant(%d,%d,%d,%d,%d,%d,%d)=%d wait(%d) type(%s)", where, MAKE_OFFSET(lock), lock->tag.lockmethodid, lock->tag.relId, lock->tag.dbId, lock->tag.objId.blkno, lock->grantMask, lock->requested[1], lock->requested[2], lock->requested[3], lock->requested[4], lock->requested[5], lock->requested[6], lock->requested[7], lock->nRequested, lock->granted[1], lock->granted[2], lock->granted[3], lock->granted[4], lock->granted[5], lock->granted[6], lock->granted[7], lock->nGranted, lock->waitProcs.size, lock_mode_names[type]); } inline static void PROCLOCK_PRINT(const char *where, const PROCLOCK *proclockP) { if ( (((PROCLOCK_LOCKMETHOD(*proclockP) == DEFAULT_LOCKMETHOD && Trace_locks) || (PROCLOCK_LOCKMETHOD(*proclockP) == USER_LOCKMETHOD && Trace_userlocks)) && (((LOCK *) MAKE_PTR(proclockP->tag.lock))->tag.relId >= (Oid) Trace_lock_oidmin)) || (Trace_lock_table && (((LOCK *) MAKE_PTR(proclockP->tag.lock))->tag.relId == Trace_lock_table)) ) elog(LOG, "%s: proclock(%lx) lock(%lx) tbl(%d) proc(%lx) xid(%u) hold(%x)", where, MAKE_OFFSET(proclockP), proclockP->tag.lock, PROCLOCK_LOCKMETHOD(*(proclockP)), proclockP->tag.proc, proclockP->tag.xid, (int) proclockP->holdMask); } #else /* not LOCK_DEBUG */ #define LOCK_PRINT(where, lock, type) #define PROCLOCK_PRINT(where, proclockP) #endif /* not LOCK_DEBUG */ static void RemoveLocalLock(LOCALLOCK *locallock); static void GrantLockLocal(LOCALLOCK *locallock, ResourceOwner owner); static int WaitOnLock(LOCKMETHODID lockmethodid, LOCALLOCK *locallock, ResourceOwner owner); static void LockCountMyLocks(SHMEM_OFFSET lockOffset, PGPROC *proc, int *myHolding); static bool UnGrantLock(LOCK *lock, LOCKMODE lockmode, PROCLOCK *proclock, LockMethod lockMethodTable); /* * InitLocks -- Init the lock module. Create a private data * structure for constructing conflict masks. */ void InitLocks(void) { /* NOP */ } /* * Fetch the lock method table associated with a given lock */ LockMethod GetLocksMethodTable(LOCK *lock) { LOCKMETHODID lockmethodid = LOCK_LOCKMETHOD(*lock); Assert(0 < lockmethodid && lockmethodid < NumLockMethods); return LockMethods[lockmethodid]; } /* * LockMethodInit -- initialize the lock table's lock type * structures * * Notes: just copying. Should only be called once. */ static void LockMethodInit(LockMethod lockMethodTable, const LOCKMASK *conflictsP, int numModes) { int i; lockMethodTable->numLockModes = numModes; /* copies useless zero element as well as the N lockmodes */ for (i = 0; i <= numModes; i++) lockMethodTable->conflictTab[i] = conflictsP[i]; } /* * LockMethodTableInit -- initialize a lock table structure * * NOTE: data structures allocated here are allocated permanently, using * TopMemoryContext and shared memory. We don't ever release them anyway, * and in normal multi-backend operation the lock table structures set up * by the postmaster are inherited by each backend, so they must be in * TopMemoryContext. */ LOCKMETHODID LockMethodTableInit(const char *tabName, const LOCKMASK *conflictsP, int numModes, int maxBackends) { LockMethod newLockMethod; LOCKMETHODID lockmethodid; char *shmemName; HASHCTL info; int hash_flags; bool found; long init_table_size, max_table_size; if (numModes >= MAX_LOCKMODES) elog(ERROR, "too many lock types %d (limit is %d)", numModes, MAX_LOCKMODES - 1); /* Compute init/max size to request for lock hashtables */ max_table_size = NLOCKENTS(maxBackends); init_table_size = max_table_size / 2; /* Allocate a string for the shmem index table lookups. */ /* This is just temp space in this routine, so palloc is OK. */ shmemName = (char *) palloc(strlen(tabName) + 32); /* each lock table has a header in shared memory */ sprintf(shmemName, "%s (lock method table)", tabName); newLockMethod = (LockMethod) ShmemInitStruct(shmemName, sizeof(LockMethodData), &found); if (!newLockMethod) elog(FATAL, "could not initialize lock table \"%s\"", tabName); /* * we're first - initialize */ if (!found) { MemSet(newLockMethod, 0, sizeof(LockMethodData)); newLockMethod->masterLock = LockMgrLock; LockMethodInit(newLockMethod, conflictsP, numModes); } /* * other modules refer to the lock table by a lockmethod ID */ Assert(NumLockMethods < MAX_LOCK_METHODS); lockmethodid = NumLockMethods++; LockMethods[lockmethodid] = newLockMethod; /* * allocate a hash table for LOCK structs. This is used to store * per-locked-object information. */ MemSet(&info, 0, sizeof(info)); info.keysize = sizeof(LOCKTAG); info.entrysize = sizeof(LOCK); info.hash = tag_hash; hash_flags = (HASH_ELEM | HASH_FUNCTION); sprintf(shmemName, "%s (lock hash)", tabName); LockMethodLockHash[lockmethodid] = ShmemInitHash(shmemName, init_table_size, max_table_size, &info, hash_flags); if (!LockMethodLockHash[lockmethodid]) elog(FATAL, "could not initialize lock table \"%s\"", tabName); /* * allocate a hash table for PROCLOCK structs. This is used to store * per-lock-holder information. */ info.keysize = sizeof(PROCLOCKTAG); info.entrysize = sizeof(PROCLOCK); info.hash = tag_hash; hash_flags = (HASH_ELEM | HASH_FUNCTION); sprintf(shmemName, "%s (proclock hash)", tabName); LockMethodProcLockHash[lockmethodid] = ShmemInitHash(shmemName, init_table_size, max_table_size, &info, hash_flags); if (!LockMethodProcLockHash[lockmethodid]) elog(FATAL, "could not initialize lock table \"%s\"", tabName); /* * allocate a non-shared hash table for LOCALLOCK structs. This is * used to store lock counts and resource owner information. * * The non-shared table could already exist in this process (this occurs * when the postmaster is recreating shared memory after a backend * crash). If so, delete and recreate it. (We could simply leave it, * since it ought to be empty in the postmaster, but for safety let's * zap it.) */ if (LockMethodLocalHash[lockmethodid]) hash_destroy(LockMethodLocalHash[lockmethodid]); info.keysize = sizeof(LOCALLOCKTAG); info.entrysize = sizeof(LOCALLOCK); info.hash = tag_hash; hash_flags = (HASH_ELEM | HASH_FUNCTION); sprintf(shmemName, "%s (locallock hash)", tabName); LockMethodLocalHash[lockmethodid] = hash_create(shmemName, 128, &info, hash_flags); pfree(shmemName); return lockmethodid; } /* * LockMethodTableRename -- allocate another lockmethod ID to the same * lock table. * * NOTES: Both the lock module and the lock chain (lchain.c) * module use table id's to distinguish between different * kinds of locks. Short term and long term locks look * the same to the lock table, but are handled differently * by the lock chain manager. This function allows the * client to use different lockmethods when acquiring/releasing * short term and long term locks, yet store them all in one hashtable. */ LOCKMETHODID LockMethodTableRename(LOCKMETHODID lockmethodid) { LOCKMETHODID newLockMethodId; if (NumLockMethods >= MAX_LOCK_METHODS) return INVALID_LOCKMETHOD; if (LockMethods[lockmethodid] == INVALID_LOCKMETHOD) return INVALID_LOCKMETHOD; /* other modules refer to the lock table by a lockmethod ID */ newLockMethodId = NumLockMethods; NumLockMethods++; LockMethods[newLockMethodId] = LockMethods[lockmethodid]; LockMethodLockHash[newLockMethodId] = LockMethodLockHash[lockmethodid]; LockMethodProcLockHash[newLockMethodId] = LockMethodProcLockHash[lockmethodid]; LockMethodLocalHash[newLockMethodId] = LockMethodLocalHash[lockmethodid]; return newLockMethodId; } /* * 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?) * * Side Effects: The lock is acquired and recorded in lock tables. * * NOTE: if we wait for the lock, there is no way to abort the wait * short of aborting the transaction. * * * Note on User Locks: * * User locks are handled totally on the application side as * long term cooperative locks which extend beyond the normal * transaction boundaries. Their purpose is to indicate to an * application that someone is `working' on an item. So it is * possible to put an user lock on a tuple's oid, retrieve the * tuple, work on it for an hour and then update it and remove * the lock. While the lock is active other clients can still * read and write the tuple but they can be aware that it has * been locked at the application level by someone. * User locks use lock tags made of an uint16 and an uint32, for * example 0 and a tuple oid, or any other arbitrary pair of * numbers following a convention established by the application. * In this sense tags don't refer to tuples or database entities. * User locks and normal locks are completely orthogonal and * they don't interfere with each other, so it is possible * to acquire a normal lock on an user-locked tuple or user-lock * a tuple for which a normal write lock already exists. * User locks are always non blocking, therefore they are never * acquired if already held by another process. They must be * released explicitly by the application but they are released * automatically when a backend terminates. * They are indicated by a lockmethod 2 which is an alias for the * normal lock table, and are distinguished from normal locks * by the following differences: * * normal lock user lock * * lockmethodid 1 2 * tag.dbId database oid database oid * tag.relId rel oid or 0 0 * tag.objId block id lock id2 * or xact id * tag.offnum 0 lock id1 * proclock.xid xid or 0 0 * persistence transaction user or backend * or backend * * The lockmode parameter can have the same values for normal locks * although probably only WRITE_LOCK can have some practical use. * * DZ - 22 Nov 1997 */ bool LockAcquire(LOCKMETHODID lockmethodid, LOCKTAG *locktag, TransactionId xid, LOCKMODE lockmode, bool dontWait) { LOCALLOCKTAG localtag; LOCALLOCK *locallock; LOCK *lock; PROCLOCK *proclock; PROCLOCKTAG proclocktag; bool found; ResourceOwner owner; LWLockId masterLock; LockMethod lockMethodTable; int status; int myHolding[MAX_LOCKMODES]; int i; #ifdef LOCK_DEBUG if (lockmethodid == USER_LOCKMETHOD && Trace_userlocks) elog(LOG, "LockAcquire: user lock [%u] %s", locktag->objId.blkno, lock_mode_names[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, "bad lock table id: %d", lockmethodid); return FALSE; } /* Session locks and user locks are not transactional */ if (xid != InvalidTransactionId && lockmethodid == DEFAULT_LOCKMETHOD) owner = CurrentResourceOwner; else owner = NULL; /* * Find or create a 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_ENTER, &found); if (!locallock) ereport(ERROR, (errcode(ERRCODE_OUT_OF_MEMORY), errmsg("out of memory"))); /* * 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 */