From: Massimo Dal Zotto <dz@cs.unitn.it>

lock.patch

        I have rewritten lock.c cleaning up the code and adding better
        assert checking I have also added some fields to the lock and
        xid tags for better support of user locks. There is also a new
        function which returns an array of pids owning a lock.
        I'm using this code from over six months and it works fine.

src/backend/storage/lmgr/multi.c

@@ -12,7 +12,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/storage/lmgr/Attic/multi.c,v 1.22 1998/08/19 02:02:44 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/storage/lmgr/Attic/multi.c,v 1.23 1998/08/25 21:20:28 scrappy Exp $
  *
  * NOTES:
  *	 (1) The lock.c module assumes that the caller here is doing
@@ -29,12 +29,10 @@
 #include "utils/rel.h"
 #include "miscadmin.h"			/* MyDatabaseId */
 
-static bool
-MultiAcquire(LOCKMETHOD lockmethod, LOCKTAG *tag, LOCKMODE lockmode,
-			 PG_LOCK_LEVEL level);
-static bool
-MultiRelease(LOCKMETHOD lockmethod, LOCKTAG *tag, LOCKMODE lockmode,
-			 PG_LOCK_LEVEL level);
+static bool MultiAcquire(LOCKMETHOD lockmethod, LOCKTAG *tag,
+						 LOCKMODE lockmode, PG_LOCK_LEVEL level);
+static bool MultiRelease(LOCKMETHOD lockmethod, LOCKTAG *tag,
+						 LOCKMODE lockmode, PG_LOCK_LEVEL level);
 
 #ifdef LowLevelLocking
 
@@ -130,6 +128,7 @@ static int	MultiPrios[] = {
  * lock table is ONE lock table, not three.
  */
 LOCKMETHOD MultiTableId = (LOCKMETHOD) NULL;
+LOCKMETHOD LongTermTableId = (LOCKMETHOD) NULL;
 #ifdef NOT_USED
 LOCKMETHOD ShortTermTableId = (LOCKMETHOD) NULL;
 #endif
@@ -150,12 +149,25 @@ InitMultiLevelLocks()
 	/* -----------------------
 	 * No short term lock table for now.  -Jeff 15 July 1991
 	 *
-	 * ShortTermTableId = LockTableRename(lockmethod);
+	 * ShortTermTableId = LockMethodTableRename(lockmethod);
 	 * if (! (ShortTermTableId)) {
 	 *	 elog(ERROR,"InitMultiLocks: couldnt rename lock table");
 	 * }
 	 * -----------------------
 	 */
+
+#ifdef USER_LOCKS
+	/*
+	 * Allocate another tableId for long-term locks
+	 */
+	LongTermTableId = LockMethodTableRename(MultiTableId);
+	if (!(LongTermTableId))
+	{
+		elog(ERROR,
+			 "InitMultiLevelLocks: couldn't rename long-term lock table");
+	}
+#endif
+
 	return MultiTableId;
 }
 

src/backend/storage/lmgr/proc.c

@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/storage/lmgr/proc.c,v 1.40 1998/07/27 19:38:15 vadim Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/storage/lmgr/proc.c,v 1.41 1998/08/25 21:20:29 scrappy Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -46,7 +46,7 @@
  *		This is so that we can support more backends. (system-wide semaphore
  *		sets run out pretty fast.)				  -ay 4/95
  *
- * $Header: /cvsroot/pgsql/src/backend/storage/lmgr/proc.c,v 1.40 1998/07/27 19:38:15 vadim Exp $
+ * $Header: /cvsroot/pgsql/src/backend/storage/lmgr/proc.c,v 1.41 1998/08/25 21:20:29 scrappy Exp $
  */
 #include <sys/time.h>
 #include <unistd.h>
@@ -75,10 +75,13 @@
 #include "storage/shmem.h"
 #include "storage/spin.h"
 #include "storage/proc.h"
+#include "utils/trace.h"
 
 static void HandleDeadLock(int sig);
 static PROC *ProcWakeup(PROC *proc, int errType);
 
+#define DeadlockCheckTimer pg_options[OPT_DEADLOCKTIMEOUT]
+
 /* --------------------
  * Spin lock for manipulating the shared process data structure:
  * ProcGlobal.... Adding an extra spin lock seemed like the smallest
@@ -247,10 +250,7 @@ InitProcess(IPCKey key)
 	 */
 	SpinRelease(ProcStructLock);
 
-	MyProc->pid = 0;
-#if 0
 	MyProc->pid = MyProcPid;
-#endif
 	MyProc->xid = InvalidTransactionId;
 #ifdef LowLevelLocking
 	MyProc->xmin = InvalidTransactionId;
@@ -361,10 +361,13 @@ ProcKill(int exitStatus, int pid)
 	 * ---------------
 	 */
 	ProcReleaseSpins(proc);
-	LockReleaseAll(1, &proc->lockQueue);
+	LockReleaseAll(DEFAULT_LOCKMETHOD, &proc->lockQueue);
 
 #ifdef USER_LOCKS
-	LockReleaseAll(0, &proc->lockQueue);
+	/*
+	 * Assume we have a second lock table.
+	 */
+	LockReleaseAll(USER_LOCKMETHOD, &proc->lockQueue);
 #endif
 
 	/* ----------------
@@ -437,11 +440,12 @@ ProcQueueInit(PROC_QUEUE *queue)
  * NOTES: The process queue is now a priority queue for locking.
  */
 int
-ProcSleep(PROC_QUEUE *waitQueue,
+ProcSleep(PROC_QUEUE *waitQueue,		/* lock->waitProcs */
 		  SPINLOCK spinlock,
-		  int token,
+		  int token,					/* lockmode */
 		  int prio,
-		  LOCK *lock)
+		  LOCK *lock,
+		  TransactionId xid)		    /* needed by user locks, see below */
 {
 	int			i;
 	PROC	   *proc;
@@ -470,7 +474,6 @@ ProcSleep(PROC_QUEUE *waitQueue,
 	proc = (PROC *) MAKE_PTR(waitQueue->links.prev);
 
 	/* If we are a reader, and they are writers, skip past them */
-
 	for (i = 0; i < waitQueue->size && proc->prio > prio; i++)
 		proc = (PROC *) MAKE_PTR(proc->links.prev);
 
@@ -482,12 +485,22 @@ ProcSleep(PROC_QUEUE *waitQueue,
 	MyProc->token = token;
 	MyProc->waitLock = lock;
 
+#ifdef USER_LOCKS
+	/* -------------------
+	 * Currently, we only need this for the ProcWakeup routines.
+	 * This must be 0 for user lock, so we can't just use the value
+	 * from GetCurrentTransactionId().
+	 * -------------------
+	 */
+	TransactionIdStore(xid, &MyProc->xid);
+#else
 #ifndef LowLevelLocking
 	/* -------------------
 	 * currently, we only need this for the ProcWakeup routines
 	 * -------------------
 	 */
 	TransactionIdStore((TransactionId) GetCurrentTransactionId(), &MyProc->xid);
+#endif
 #endif
 
 	/* -------------------
@@ -510,7 +523,8 @@ ProcSleep(PROC_QUEUE *waitQueue,
 	 * --------------
 	 */
 	MemSet(&timeval, 0, sizeof(struct itimerval));
-	timeval.it_value.tv_sec = DEADLOCK_CHECK_TIMER;
+	timeval.it_value.tv_sec = \
+		(DeadlockCheckTimer ? DeadlockCheckTimer : DEADLOCK_CHECK_TIMER);
 
 	do
 	{
@@ -525,7 +539,8 @@ ProcSleep(PROC_QUEUE *waitQueue,
 		 * the semaphore implementation.
 		 * --------------
 		 */
-		IpcSemaphoreLock(MyProc->sem.semId, MyProc->sem.semNum, IpcExclusiveLock);
+		IpcSemaphoreLock(MyProc->sem.semId, MyProc->sem.semNum,
+						 IpcExclusiveLock);
 	} while (MyProc->errType == STATUS_NOT_FOUND);		/* sleep after deadlock
 														 * check */
 
@@ -534,8 +549,6 @@ ProcSleep(PROC_QUEUE *waitQueue,
 	 * ---------------
 	 */
 	timeval.it_value.tv_sec = 0;
-
-
 	if (setitimer(ITIMER_REAL, &timeval, &dummy))
 		elog(FATAL, "ProcSleep: Unable to diable timer for process wakeup");
 
@@ -546,6 +559,11 @@ ProcSleep(PROC_QUEUE *waitQueue,
 	 */
 	SpinAcquire(spinlock);
 
+#ifdef LOCK_MGR_DEBUG
+	/* Just to get meaningful debug messages from DumpLocks() */
+	MyProc->waitLock = (LOCK *)NULL;
+#endif
+
 	return (MyProc->errType);
 }
 
@@ -589,17 +607,39 @@ ProcLockWakeup(PROC_QUEUE *queue, LOCKMETHOD lockmethod, LOCK *lock)
 {
 	PROC	   *proc;
 	int			count;
+	int			trace_flag;
+	int			last_locktype = -1;
+	int			queue_size = queue->size;
+
+	Assert(queue->size >= 0);
 
 	if (!queue->size)
 		return (STATUS_NOT_FOUND);
 
 	proc = (PROC *) MAKE_PTR(queue->links.prev);
 	count = 0;
-	while ((LockResolveConflicts(lockmethod,
+	while ((queue_size--) && (proc))
+	{
+		/*
+		 * This proc will conflict as the previous one did, don't even try.
+		 */
+		if (proc->token == last_locktype)
+		{
+			continue;
+		}
+
+		/*
+		 * This proc conflicts with locks held by others, ignored.
+		 */
+		if (LockResolveConflicts(lockmethod,
 								 lock,
 								 proc->token,
-								 proc->xid) == STATUS_OK))
-	{
+								 proc->xid,
+								 (XIDLookupEnt *) NULL) != STATUS_OK)
+		{
+			last_locktype = proc->token;
+			continue;
+		}
 
 		/*
 		 * there was a waiting process, grant it the lock before waking it
@@ -608,24 +648,34 @@ ProcLockWakeup(PROC_QUEUE *queue, LOCKMETHOD lockmethod, LOCK *lock)
 		 * time that the awoken process begins executing again.
 		 */
 		GrantLock(lock, proc->token);
-		queue->size--;
 
 		/*
 		 * ProcWakeup removes proc from the lock waiting process queue and
 		 * returns the next proc in chain.
 		 */
-		proc = ProcWakeup(proc, NO_ERROR);
 
 		count++;
-		if (!proc || queue->size == 0)
-			break;
+		queue->size--;
+		proc = ProcWakeup(proc, NO_ERROR);
 	}
 
+	Assert(queue->size >= 0);
+
 	if (count)
 		return (STATUS_OK);
-	else
+	else {
 		/* Something is still blocking us.	May have deadlocked. */
+		trace_flag = (lock->tag.lockmethod == USER_LOCKMETHOD) ? \
+			TRACE_USERLOCKS : TRACE_LOCKS;
+		TPRINTF(trace_flag,
+				"ProcLockWakeup: lock(%x) can't wake up any process",
+				MAKE_OFFSET(lock));
+#ifdef DEADLOCK_DEBUG
+		if (pg_options[trace_flag] >= 2)
+			DumpAllLocks();
+#endif
 		return (STATUS_NOT_FOUND);
+	}
 }
 
 void
@@ -685,7 +735,7 @@ HandleDeadLock(int sig)
 	}
 
 #ifdef DEADLOCK_DEBUG
-	DumpLocks();
+	DumpAllLocks();
 #endif
 
 	if (!DeadLockCheck(&(MyProc->lockQueue), MyProc->waitLock, true))
@@ -711,7 +761,8 @@ HandleDeadLock(int sig)
 	 * I was awoken by a signal, not by someone unlocking my semaphore.
 	 * ------------------
 	 */
-	IpcSemaphoreUnlock(MyProc->sem.semId, MyProc->sem.semNum, IpcExclusiveLock);
+	IpcSemaphoreUnlock(MyProc->sem.semId, MyProc->sem.semNum,
+					   IpcExclusiveLock);
 
 	/* -------------
 	 * Set MyProc->errType to STATUS_ERROR so that we abort after

src/include/storage/lock.h

@@ -6,7 +6,7 @@
  *
  * Copyright (c) 1994, Regents of the University of California
  *
- * $Id: lock.h,v 1.16 1998/08/01 15:26:37 vadim Exp $
+ * $Id: lock.h,v 1.17 1998/08/25 21:20:31 scrappy Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -15,6 +15,8 @@
 
 #include <storage/shmem.h>
 #include <storage/itemptr.h>
+#include <storage/sinvaladt.h>
+#include <utils/array.h>
 
 extern SPINLOCK LockMgrLock;
 typedef int MASK;
@@ -32,7 +34,7 @@ typedef int MASK;
  * NLOCKENTS - The maximum number of lock entries in the lock table.
  * ----------------------
  */
-#define NBACKENDS 50
+#define NBACKENDS MaxBackendId
 #define NLOCKS_PER_XACT 40
 #define NLOCKENTS NLOCKS_PER_XACT*NBACKENDS
 
@@ -51,9 +53,14 @@ typedef int LOCKMETHOD;
  * CreateSpinLocks() or the number of shared memory locations allocated
  * for lock table spin locks in the case of machines with TAS instructions.
  */
-#define MAX_LOCK_METHODS 2
+#define MAX_LOCK_METHODS 	3
 
-#define INVALID_TABLEID 0
+#define INVALID_TABLEID		0
+
+#define INVALID_LOCKMETHOD	INVALID_TABLEID
+#define DEFAULT_LOCKMETHOD	1
+#define USER_LOCKMETHOD		2
+#define MIN_LOCKMETHOD		DEFAULT_LOCKMETHOD
 
 /*typedef struct LOCK LOCK; */
 
@@ -63,9 +70,11 @@ typedef struct LTAG
 	Oid			relId;
 	Oid			dbId;
 	ItemPointerData tupleId;
+	uint16		lockmethod;				/* needed by user locks */
 } LOCKTAG;
 
 #define TAGSIZE (sizeof(LOCKTAG))
+#define LOCKTAG_LOCKMETHOD(locktag) ((locktag).lockmethod)
 
 /* This is the control structure for a lock table.	It
  * lives in shared memory:
@@ -143,8 +152,18 @@ typedef struct XIDTAG
 	SHMEM_OFFSET lock;
 	int			pid;
 	TransactionId xid;
+#ifdef USE_XIDTAG_LOCKMETHOD
+	uint16		lockmethod;				/* for debug or consistency checking */
+#endif
 } XIDTAG;
 
+#ifdef USE_XIDTAG_LOCKMETHOD
+#define XIDTAG_LOCKMETHOD(xidtag) ((xidtag).lockmethod)
+#else
+#define XIDTAG_LOCKMETHOD(xidtag) \
+		(((LOCK*) MAKE_PTR((xidtag).lock))->tag.lockmethod)
+#endif
+
 typedef struct XIDLookupEnt
 {
 	/* tag */
@@ -157,6 +176,7 @@ typedef struct XIDLookupEnt
 } XIDLookupEnt;
 
 #define XID_TAGSIZE (sizeof(XIDTAG))
+#define XIDENT_LOCKMETHOD(xident) (XIDTAG_LOCKMETHOD((xident).tag))
 
 /* originally in procq.h */
 typedef struct PROC_QUEUE
@@ -191,14 +211,16 @@ typedef struct LOCK
 	int			nActive;
 } LOCK;
 
-#define LockGetLock_nHolders(l) l->nHolders
+#define LOCK_LOCKMETHOD(lock) (LOCKTAG_LOCKMETHOD((lock).tag))
 
+#define LockGetLock_nHolders(l) l->nHolders
+#ifdef NOT_USED
 #define LockDecrWaitHolders(lock, lockmode) \
 ( \
   lock->nHolding--, \
   lock->holders[lockmode]-- \
 )
-
+#endif
 #define LockLockTable() SpinAcquire(LockMgrLock);
 #define UnlockLockTable() SpinRelease(LockMgrLock);
 
@@ -209,23 +231,27 @@ extern SPINLOCK LockMgrLock;
  */
 extern void InitLocks(void);
 extern void LockDisable(int status);
-extern LOCKMETHOD
-LockMethodTableInit(char *tabName, MASK *conflictsP, int *prioP,
-			int numModes);
-extern bool LockAcquire(LOCKMETHOD lockmethod, LOCKTAG *locktag, LOCKMODE lockmode);
-extern int
-LockResolveConflicts(LOCKMETHOD lockmethod, LOCK *lock, LOCKMODE lockmode,
-					 TransactionId xid);
-extern bool LockRelease(LOCKMETHOD lockmethod, LOCKTAG *locktag, LOCKMODE lockmode);
+extern LOCKMETHOD LockMethodTableInit(char *tabName, MASK *conflictsP,
+									  int *prioP, int numModes);
+extern LOCKMETHOD LockMethodTableRename(LOCKMETHOD lockmethod);
+extern bool LockAcquire(LOCKMETHOD lockmethod, LOCKTAG *locktag,
+						LOCKMODE lockmode);
+extern int LockResolveConflicts(LOCKMETHOD lockmethod, LOCK *lock,
+								LOCKMODE lockmode, TransactionId xid,
+								XIDLookupEnt *xidentP);
+extern bool LockRelease(LOCKMETHOD lockmethod, LOCKTAG *locktag,
+						LOCKMODE lockmode);
 extern void GrantLock(LOCK *lock, LOCKMODE lockmode);
 extern bool LockReleaseAll(LOCKMETHOD lockmethod, SHM_QUEUE *lockQueue);
 extern int	LockShmemSize(void);
 extern bool LockingDisabled(void);
-extern bool DeadLockCheck(SHM_QUEUE *lockQueue, LOCK *findlock, bool skip_check);
+extern bool DeadLockCheck(SHM_QUEUE *lockQueue, LOCK *findlock,
+						  bool skip_check);
+ArrayType* LockOwners(LOCKMETHOD lockmethod, LOCKTAG *locktag);
 
 #ifdef DEADLOCK_DEBUG
 extern void DumpLocks(void);
-
+extern void DumpAllLocks(void);
 #endif
 
 #endif							/* LOCK_H */

src/include/storage/proc.h

@@ -6,7 +6,7 @@
  *
  * Copyright (c) 1994, Regents of the University of California
  *
- * $Id: proc.h,v 1.13 1998/07/27 19:38:38 vadim Exp $
+ * $Id: proc.h,v 1.14 1998/08/25 21:20:32 scrappy Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -105,10 +105,10 @@ extern bool ProcRemove(int pid);
 /* make static in storage/lmgr/proc.c -- jolly */
 
 extern void ProcQueueInit(PROC_QUEUE *queue);
-extern int
-ProcSleep(PROC_QUEUE *queue, SPINLOCK spinlock, int token,
-		  int prio, LOCK *lock);
-extern int	ProcLockWakeup(PROC_QUEUE *queue, LOCKMETHOD lockmethod, LOCK *lock);
+extern int ProcSleep(PROC_QUEUE *queue, SPINLOCK spinlock, int token,
+					 int prio, LOCK *lock, TransactionId xid);
+extern int	ProcLockWakeup(PROC_QUEUE *queue, LOCKMETHOD lockmethod,
+						   LOCK *lock);
 extern void ProcAddLock(SHM_QUEUE *elem);
 extern void ProcReleaseSpins(PROC *proc);
 extern void ProcFreeAllSemaphores(void);