Re-implement deadlock detection and resolution, per design notes posted

to pghackers on 18-Jan-01.

src/backend/storage/lmgr/Makefile

@@ -4,7 +4,7 @@
 #    Makefile for storage/lmgr
 #
 # IDENTIFICATION
-#    $Header: /cvsroot/pgsql/src/backend/storage/lmgr/Makefile,v 1.14 2000/08/31 16:10:36 petere Exp $
+#    $Header: /cvsroot/pgsql/src/backend/storage/lmgr/Makefile,v 1.15 2001/01/25 03:31:16 tgl Exp $
 #
 #-------------------------------------------------------------------------
 
@@ -12,7 +12,7 @@ subdir = src/backend/storage/lmgr
 top_builddir = ../../../..
 include $(top_builddir)/src/Makefile.global
 
-OBJS = lmgr.o lock.o proc.o
+OBJS = lmgr.o lock.o proc.o deadlock.o
 
 all: SUBSYS.o
 

src/backend/storage/lmgr/README

-$Header: /cvsroot/pgsql/src/backend/storage/lmgr/README,v 1.6 2001/01/22 22:30:06 tgl Exp $
+$Header: /cvsroot/pgsql/src/backend/storage/lmgr/README,v 1.7 2001/01/25 03:31:16 tgl Exp $
 
 There are two fundamental lock structures: the per-lockable-object LOCK
 struct, and the per-lock-holder HOLDER struct.  A LOCK object exists
@@ -373,7 +373,8 @@ time with "C before B", which won't move C far enough up.  So we look for
 soft edges outgoing from C starting at the front of the wait queue.
 
 5. The working data structures needed by the deadlock detection code can
-be proven not to need more than MAXBACKENDS entries.  Therefore the
-working storage can be statically allocated instead of depending on
-palloc().  This is a good thing, since if the deadlock detector could
-fail for extraneous reasons, all the above safety proofs fall down.
+be limited to numbers of entries computed from MaxBackends.  Therefore,
+we can allocate the worst-case space needed during backend startup.
+This seems a safer approach than trying to allocate workspace on the fly;
+we don't want to risk having the deadlock detector run out of memory,
+else we really have no guarantees at all that deadlock will be detected.

src/include/storage/lock.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: lock.h,v 1.43 2001/01/24 19:43:27 momjian Exp $
+ * $Id: lock.h,v 1.44 2001/01/25 03:31:16 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -247,6 +247,7 @@ typedef struct HOLDER
 extern void InitLocks(void);
 extern void LockDisable(bool status);
 extern bool LockingDisabled(void);
+extern LOCKMETHODTABLE *GetLocksMethodTable(LOCK *lock);
 extern LOCKMETHOD LockMethodTableInit(char *tabName, LOCKMASK *conflictsP,
 					int *prioP, int numModes, int maxBackends);
 extern LOCKMETHOD LockMethodTableRename(LOCKMETHOD lockmethod);
@@ -256,12 +257,15 @@ extern bool LockRelease(LOCKMETHOD lockmethod, LOCKTAG *locktag,
 						TransactionId xid, LOCKMODE lockmode);
 extern bool LockReleaseAll(LOCKMETHOD lockmethod, PROC *proc,
 						   bool allxids, TransactionId xid);
-extern int LockResolveConflicts(LOCKMETHOD lockmethod, LOCKMODE lockmode,
-								LOCK *lock, HOLDER *holder, PROC *proc,
-								int *myHolding);
+extern int LockCheckConflicts(LOCKMETHODTABLE *lockMethodTable,
+							  LOCKMODE lockmode,
+							  LOCK *lock, HOLDER *holder, PROC *proc,
+							  int *myHolding);
 extern void GrantLock(LOCK *lock, HOLDER *holder, LOCKMODE lockmode);
+extern void RemoveFromWaitQueue(PROC *proc);
 extern int	LockShmemSize(int maxBackends);
-extern bool DeadLockCheck(PROC *thisProc, LOCK *findlock);
+extern bool DeadLockCheck(PROC *proc);
+extern void InitDeadLockChecking(void);
 
 #ifdef LOCK_DEBUG
 extern void DumpLocks(void);

src/include/storage/proc.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: proc.h,v 1.38 2001/01/24 19:43:28 momjian Exp $
+ * $Id: proc.h,v 1.39 2001/01/25 03:31:16 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -41,7 +41,7 @@ struct proc
 	SHM_QUEUE	links;			/* list link if process is in a list */
 
 	SEMA		sem;			/* ONE semaphore to sleep on */
-	int			errType;		/* error code tells why we woke up */
+	int			errType;		/* STATUS_OK or STATUS_ERROR after wakeup */
 
 	TransactionId xid;			/* transaction currently being executed by
 								 * this proc */
@@ -86,13 +86,6 @@ do { \
 	if (MyProc) (MyProc->sLocks[(lock)])--; \
 } while (0)
 
-/*
- * flags explaining why process woke up
- */
-#define NO_ERROR		0
-#define ERR_TIMEOUT		1
-#define ERR_BUFFER_IO	2
-
 
 /*
  * There is one ProcGlobal struct for the whole installation.
@@ -134,10 +127,10 @@ extern void ProcReleaseLocks(bool isCommit);
 extern bool ProcRemove(int pid);
 
 extern void ProcQueueInit(PROC_QUEUE *queue);
-extern int ProcSleep(LOCKMETHODCTL *lockctl, LOCKMODE lockmode,
+extern int ProcSleep(LOCKMETHODTABLE *lockMethodTable, LOCKMODE lockmode,
 					 LOCK *lock, HOLDER *holder);
 extern PROC *ProcWakeup(PROC *proc, int errType);
-extern int ProcLockWakeup(LOCKMETHOD lockmethod, LOCK *lock);
+extern void ProcLockWakeup(LOCKMETHODTABLE *lockMethodTable, LOCK *lock);
 extern void ProcReleaseSpins(PROC *proc);
 extern bool LockWaitCancel(void);
 extern void HandleDeadLock(SIGNAL_ARGS);