/*-------------------------------------------------------------------------
*
* lock.c--
* simple lock acquisition
*
* Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/storage/lmgr/lock.c,v 1.4 1996/11/03 05:07:29 scrappy 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.
*
* Interface:
*
* LockAcquire(), LockRelease(), LockTabInit().
*
* LockReplace() is called only within this module and by the
* lkchain module. It releases a lock without looking
* the lock up in the lock table.
*
* NOTE: This module is used to define new lock tables. The
* multi-level lock table (multi.c) used by the heap
* access methods calls these routines. See multi.c for
* examples showing how to use this interface.
*
*-------------------------------------------------------------------------
*/
#include <stdio.h> /* for sprintf() */
#include "postgres.h"
#include "storage/shmem.h"
#include "storage/spin.h"
#include "storage/proc.h"
#include "storage/lock.h"
#include "utils/hsearch.h"
#include "utils/palloc.h"
#include "access/xact.h"
/*#define LOCK_MGR_DEBUG*/
#ifndef LOCK_MGR_DEBUG
#define LOCK_PRINT(where,tag,type)
#define LOCK_DUMP(where,lock,type)
#define XID_PRINT(where,xidentP)
#else /* LOCK_MGR_DEBUG */
#define LOCK_PRINT(where,tag,type)\
elog(NOTICE, "%s: rel (%d) dbid (%d) tid (%d,%d) type (%d)\n",where, \
tag->relId, tag->dbId, \
( (tag->tupleId.ip_blkid.data[0] >= 0) ? \
BlockIdGetBlockNumber(&tag->tupleId.ip_blkid) : -1 ), \
tag->tupleId.ip_posid, \
type);
#define LOCK_DUMP(where,lock,type)\
elog(NOTICE, "%s: rel (%d) dbid (%d) tid (%d,%d) nHolding (%d) holders (%d,%d,%d,%d,%d) type (%d)\n",where, \
lock->tag.relId, lock->tag.dbId, \
((lock->tag.tupleId.ip_blkid.data[0] >= 0) ? \
BlockIdGetBlockNumber(&lock->tag.tupleId.ip_blkid) : -1 ), \
lock->tag.tupleId.ip_posid, \
lock->nHolding,\
lock->holders[1],\
lock->holders[2],\
lock->holders[3],\
lock->holders[4],\
lock->holders[5],\
type);
#define XID_PRINT(where,xidentP)\
elog(NOTICE,\
"%s:xid (%d) pid (%d) lock (%x) nHolding (%d) holders (%d,%d,%d,%d,%d)",\
where,\
xidentP->tag.xid,\
xidentP->tag.pid,\
xidentP->tag.lock,\
xidentP->nHolding,\
xidentP->holders[1],\
xidentP->holders[2],\
xidentP->holders[3],\
xidentP->holders[4],\
xidentP->holders[5]);
#endif /* LOCK_MGR_DEBUG */
SPINLOCK LockMgrLock; /* in Shmem or created in CreateSpinlocks() */
/* This is to simplify/speed up some bit arithmetic */
static MASK BITS_OFF[MAX_LOCKTYPES];
static MASK BITS_ON[MAX_LOCKTYPES];
/* -----------------
* XXX Want to move this to this file
* -----------------
*/
static bool LockingIsDisabled;
/* -------------------
* map from tableId to the lock table structure
* -------------------
*/
static LOCKTAB *AllTables[MAX_TABLES];
/* -------------------
* no zero-th table
* -------------------
*/
static int NumTables = 1;
/* -------------------
* InitLocks -- Init the lock module. Create a private data
* structure for constructing conflict masks.
* -------------------
*/
void
InitLocks()
{
int i;
int bit;
bit = 1;
/* -------------------
* remember 0th locktype is invalid
* -------------------
*/
for (i=0;i<MAX_LOCKTYPES;i++,bit <<= 1)
{
BITS_ON[i] = bit;
BITS_OFF[i] = ~bit;
}
}
/* -------------------
* LockDisable -- sets LockingIsDisabled flag to TRUE or FALSE.
* ------------------
*/
void
LockDisable(int status)
{
LockingIsDisabled = status;
}
/*
* LockTypeInit -- initialize the lock table's lock type
* structures
*
* Notes: just copying. Should only be called once.
*/
static void
LockTypeInit(LOCKTAB *ltable,
MASK *conflictsP,
int *prioP,
int ntypes)
{
int i;
ltable->ctl->nLockTypes = ntypes;
ntypes++;
for (i=0;i<ntypes;i++,prioP++,conflictsP++)
{
ltable->ctl->conflictTab[i] = *conflictsP;
ltable->ctl->prio[i] = *prioP;
}
}
/*
* LockTabInit -- initialize a lock table structure
*
* Notes:
* (a) a lock table has four separate entries in the binding
* table. This is because every shared hash table and spinlock
* has its name stored in the binding table at its creation. It
* is wasteful, in this case, but not much space is involved.
*
*/
LockTableId
LockTabInit(char *tabName,
MASK *conflictsP,
int *prioP,
int ntypes)
{
LOCKTAB *ltable;
char *shmemName;
HASHCTL info;
int hash_flags;
bool found;
int status = TRUE;
if (ntypes > MAX_LOCKTYPES)
{
elog(NOTICE,"LockTabInit: too many lock types %d greater than %d",
ntypes,MAX_LOCKTYPES);
return(INVALID_TABLEID);
}
if (NumTables > MAX_TABLES)
{
elog(NOTICE,
"LockTabInit: system limit of MAX_TABLES (%d) lock tables",
MAX_TABLES);
return(INVALID_TABLEID);
}
/* allocate a string for the binding table lookup */
shmemName = (char *) palloc((unsigned)(strlen(tabName)+32));
if (! shmemName)
{
elog(NOTICE,"LockTabInit: couldn't malloc string %s \n",tabName);
return(INVALID_TABLEID);
}
/* each lock table has a non-shared header */
ltable = (LOCKTAB *) palloc((unsigned) sizeof(LOCKTAB));
if (! ltable)
{
elog(NOTICE,"LockTabInit: couldn't malloc lock table %s\n",tabName);
(void) pfree (shmemName);
return(INVALID_TABLEID);
}
/* ------------------------
* find/acquire the spinlock for the table
* ------------------------
*/
SpinAcquire(LockMgrLock);
/* -----------------------
* allocate a control structure from shared memory or attach to it
* if it already exists.
* -----------------------
*/
sprintf(shmemName,"%s (ctl)",tabName);
ltable->ctl = (LOCKCTL *)
ShmemInitStruct(shmemName,(unsigned)sizeof(LOCKCTL),&found);
if (! ltable->ctl)
{
elog(FATAL,"LockTabInit: couldn't initialize %s",tabName);
status = FALSE;
}
/* ----------------
* we're first - initialize
* ----------------
*/
if (! found)
{
memset(ltable->ctl, 0, sizeof(LOCKCTL));
ltable->ctl->masterLock = LockMgrLock;
ltable->ctl->tableId = NumTables;
}
/* --------------------
* other modules refer to the lock table by a tableId
* --------------------
*/
AllTables[NumTables] = ltable;
NumTables++;
Assert(NumTables <= MAX_TABLES);
/* ----------------------
* allocate a hash table for the lock tags. This is used
* to find the different locks.
* ----------------------
*/
info.keysize = sizeof(LOCKTAG);
info.datasize = sizeof(LOCK);
info.hash = tag_hash;
hash_flags = (HASH_ELEM | HASH_FUNCTION);
sprintf(shmemName,"%s (lock hash)",tabName);
ltable->lockHash = (HTAB *) ShmemInitHash(shmemName,
INIT_TABLE_SIZE,MAX_TABLE_SIZE,
&info,hash_flags);
Assert( ltable->lockHash->hash == tag_hash);
if (! ltable->lockHash)
{
elog(FATAL,"LockTabInit: couldn't initialize %s",tabName);
status = FALSE;
}
/* -------------------------
* allocate an xid table. When different transactions hold
* the same lock, additional information must be saved (locks per tx).
* -------------------------
*/
info.keysize = XID_TAGSIZE;
info.datasize = sizeof(XIDLookupEnt);
info.hash = tag_hash;
hash_flags = (HASH_ELEM | HASH_FUNCTION);
sprintf(shmemName,"%s (xid hash)",tabName);
ltable->xidHash = (HTAB *) ShmemInitHash(shmemName,
INIT_TABLE_SIZE,MAX_TABLE_SIZE,
&info,hash_flags);
if (! ltable->xidHash)
{
elog(FATAL,"LockTabInit: couldn't initialize %s",tabName);
status = FALSE;
}
/* init ctl data structures */
LockTypeInit(ltable, conflictsP, prioP, ntypes);
SpinRelease(LockMgrLock);
(void) pfree (shmemName);
if (status)
return(ltable->ctl->tableId);
else
return(INVALID_TABLEID);
}
/*
* LockTabRename -- allocate another tableId 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 tableIds when acquiring/releasing
* short term and long term locks.
*/
LockTableId
LockTabRename(LockTableId tableId)
{
LockTableId newTableId;
if (NumTables >= MAX_TABLES)
{
return(INVALID_TABLEID);
}
if (AllTables[tableId] == INVALID_TABLEID)
{
return(INVALID_TABLEID);
}
/* other modules refer to the lock table by a tableId */
newTableId = NumTables;
NumTables++;
AllTables[newTableId] = AllTables[tableId];
return(newTableId);
}
/*
* LockAcquire -- Check for lock conflicts, sleep if conflict found,
* set lock if/when no conflicts.
*
* Returns: TRUE if parameters are correct, FALSE otherwise.
*
* Side Effects: The lock is always acquired. No way to abort
* a lock acquisition other than aborting the transaction.
* Lock is recorded in the lkchain.
#ifdef USER_LOCKS
* 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 dummy tableId 0 which doesn't have
* any table allocated but uses the normal lock table, and are
* distinguished from normal locks for the following differences:
*
* normal lock user lock
*
* tableId 1 0
* tag.relId rel oid 0
* tag.ItemPointerData.ip_blkid block id lock id2
* tag.ItemPointerData.ip_posid tuple offset lock id1
* xid.pid 0 backend pid
* xid.xid current xid 0
* persistence transaction user or backend
*
* The lockt parameter can have the same values for normal locks
* although probably only WRITE_LOCK can have some practical use.
*
* DZ - 4 Oct 1996
#endif
*/
bool
LockAcquire(LockTableId tableId, LOCKTAG *lockName, LOCKT lockt)
{
XIDLookupEnt *result,item;
HTAB *xidTable;
bool found;
LOCK *lock = NULL;
SPINLOCK masterLock;
LOCKTAB *ltable;
int status;
TransactionId myXid;
#ifdef USER_LOCKS
int is_user_lock;
is_user_lock = (tableId == 0);
if (is_user_lock) {
tableId = 1;
#ifdef USER_LOCKS_DEBUG
elog(NOTICE,"LockAcquire: user lock tag [%u,%u] %d",
lockName->tupleId.ip_posid,
((lockName->tupleId.ip_blkid.bi_hi<<16)+
lockName->tupleId.ip_blkid.bi_lo),
lockt);
#endif
}
#endif
Assert (tableId < NumTables);
ltable = AllTables[tableId];
if (!ltable)
{
elog(NOTICE,"LockAcquire: bad lock table %d",tableId);
return (FALSE);
}
if (LockingIsDisabled)
{
return(TRUE);
}
LOCK_PRINT("Acquire",lockName,lockt);
masterLock = ltable->ctl->masterLock;
SpinAcquire(masterLock);
Assert( ltable->lockHash->hash == tag_hash);
lock = (LOCK *)hash_search(ltable->lockHash,(Pointer)lockName,HASH_ENTER,&found);
if (! lock)
{
SpinRelease(masterLock);
elog(FATAL,"LockAcquire: lock table %d is corrupted",tableId);
return(FALSE);
}
/* --------------------
* if there was nothing else there, complete initialization
* --------------------
*/
if (! found)
{
lock->mask = 0;
ProcQueueInit(&(lock->waitProcs));
memset((char *)lock->holders, 0, sizeof(int)*MAX_LOCKTYPES);
memset((char *)lock->activeHolders, 0, sizeof(int)*MAX_LOCKTYPES);
lock->nHolding = 0;
lock->nActive = 0;
Assert(BlockIdEquals(&(lock->tag.tupleId.ip_blkid),
&(lockName->tupleId.ip_blkid)));
}
/* ------------------
* add an element to the lock queue so that we can clear the
* locks at end of transaction.
* ------------------
*/
xidTable = ltable->xidHash;
myXid = GetCurrentTransactionId();
/* ------------------
* Zero out all of the tag bytes (this clears the padding bytes for long
* word alignment and ensures hashing consistency).
* ------------------
*/
memset(&item, 0, XID_TAGSIZE);
TransactionIdStore(myXid, &item.tag.xid);
item.tag.lock = MAKE_OFFSET(lock);
#if 0
item.tag.pid = MyPid;
#endif
#ifdef USER_LOCKS
if (is_user_lock) {
item.tag.pid = getpid();
item.tag.xid = myXid = 0;
#ifdef USER_LOCKS_DEBUG
elog(NOTICE,"LockAcquire: user lock xid [%d,%d,%d]",
item.tag.lock, item.tag.pid, item.tag.xid);
#endif
}
#endif
result = (XIDLookupEnt *)hash_search(xidTable, (Pointer)&item, HASH_ENTER, &found);
if (!result)
{
elog(NOTICE,"LockAcquire: xid table corrupted");
return(STATUS_ERROR);
}
if (!found)
{
XID_PRINT("queueing XidEnt LockAcquire:", result);
ProcAddLock(&result->queue);
result->nHolding = 0;
memset((char *)result->holders, 0, sizeof(int)*MAX_LOCKTYPES);
}
/* ----------------
* lock->nholding tells us how many processes have _tried_ to
* acquire this lock, Regardless of whether they succeeded or
* failed in doing so.
* ----------------
*/
lock->nHolding++;
lock->holders[lockt]++;
/* --------------------
* If I'm the only one holding a lock, then there
* cannot be a conflict. Need to subtract one from the
* lock's count since we just bumped the count up by 1
* above.
* --------------------
*/
if (result->nHolding == lock->nActive)
{
result->holders[lockt]++;
result->nHolding++;
GrantLock(lock, lockt);
SpinRelease(masterLock);
return(TRUE);
}
Assert(result->nHolding <= lock->nActive);
status = LockResolveConflicts(ltable, lock, lockt, myXid);
if (status == STATUS_OK)
{
GrantLock(lock, lockt);
}
else if (status == STATUS_FOUND)
{
#ifdef USER_LOCKS
/*
* User locks are non blocking. If we can't acquire a lock
* remove the xid entry and return FALSE without waiting.
*/
if (is_user_lock) {
if (!result->nHolding) {
SHMQueueDelete(&result->queue);
hash_search(xidTable, (Pointer)&item, HASH_REMOVE, &found);
}
lock->nHolding--;
lock->holders[lockt]--;
SpinRelease(masterLock);
#ifdef USER_LOCKS_DEBUG
elog(NOTICE,"LockAcquire: user lock failed");
#endif
return(FALSE);
}
#endif
status = WaitOnLock(ltable, tableId, lock, lockt);
XID_PRINT("Someone granted me the lock", result);
}
SpinRelease(masterLock);
return(status == STATUS_OK);
}
/* ----------------------------
* LockResolveConflicts -- test for lock conflicts
*
* NOTES:
* Here's what makes this complicated: one transaction's
* locks don't conflict with one another. When many processes
* hold locks, each has to subtract off the other's locks when
* determining whether or not any new lock acquired conflicts with
* the old ones.
*
* For example, if I am already holding a WRITE_INTENT lock,
* there will not be a conflict with my own READ_LOCK. If I
* don't consider the intent lock when checking for conflicts,
* I find no conflict.
* ----------------------------
*/
int
LockResolveConflicts(LOCKTAB *ltable,
LOCK *lock,
LOCKT lockt,
TransactionId xid)
{
XIDLookupEnt *result,item;
int *myHolders;
int nLockTypes;
HTAB *xidTable;
bool found;
int bitmask;
int i,tmpMask;
nLockTypes = ltable->ctl->nLockTypes;
xidTable = ltable->xidHash;
/* ---------------------
* read my own statistics from the xid table. If there
* isn't an entry, then we'll just add one.
*
* Zero out the tag, this clears the padding bytes for long
* word alignment and ensures hashing consistency.
* ------------------
*/
memset(&item, 0, XID_TAGSIZE);
TransactionIdStore(xid, &item.tag.xid);
item.tag.lock = MAKE_OFFSET(lock);
#if 0
item.tag.pid = pid;
#endif
if (! (result = (XIDLookupEnt *)
hash_search(xidTable, (Pointer)&item, HASH_ENTER, &found)))
{
elog(NOTICE,"LockResolveConflicts: xid table corrupted");
return(STATUS_ERROR);
}
myHolders = result->holders;
if (! found)
{
/* ---------------
* we're not holding any type of lock yet. Clear
* the lock stats.
* ---------------
*/
memset(result->holders, 0, nLockTypes * sizeof(*(lock->holders)));
result->nHolding = 0;
}
/* ----------------------------
* first check for global conflicts: If no locks conflict
* with mine, then I get the lock.
*
* Checking for conflict: lock->mask represents the types of
* currently held locks. conflictTable[lockt] has a bit
* set for each type of lock that conflicts with mine. Bitwise
* compare tells if there is a conflict.
* ----------------------------
*/
if (! (ltable->ctl->conflictTab[lockt] & lock->mask))
{
result->holders[lockt]++;
result->nHolding++;
XID_PRINT("Conflict Resolved: updated xid entry stats", result);
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.
* ------------------------
*/
bitmask = 0;
tmpMask = 2;
for (i=1;i<=nLockTypes;i++, tmpMask <<= 1)
{
if (lock->activeHolders[i] - myHolders[i])
{
bitmask |= tmpMask;
}
}
/* ------------------------
* 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 (! (ltable->ctl->conflictTab[lockt] & bitmask))
{
/* no conflict. Get the lock and go on */
result->holders[lockt]++;
result->nHolding++;
XID_PRINT("Conflict Resolved: updated xid entry stats", result);
return(STATUS_OK);
}
return(STATUS_FOUND);
}
int
WaitOnLock(LOCKTAB *ltable, LockTableId tableId, LOCK *lock, LOCKT lockt)
{
PROC_QUEUE *waitQueue = &(lock->waitProcs);
int prio = ltable->ctl->prio[lockt];
/* the waitqueue is ordered by priority. I insert myself
* according to the priority of the lock I am acquiring.
*
* SYNC NOTE: I am assuming that the lock table spinlock
* is sufficient synchronization for this queue. That
* will not be true if/when people can be deleted from
* the queue by a SIGINT or something.
*/
LOCK_DUMP("WaitOnLock: sleeping on lock", lock, lockt);
if (ProcSleep(waitQueue,
ltable->ctl->masterLock,
lockt,
prio,
lock) != NO_ERROR)
{
/* -------------------
* This could have happend as a result of a deadlock, see HandleDeadLock()
* Decrement the lock nHolding and holders fields as we are no longer
* waiting on this lock.
* -------------------
*/
lock->nHolding--;
lock->holders[lockt]--;
LOCK_DUMP("WaitOnLock: aborting on lock", lock, lockt);
SpinRelease(ltable->ctl->masterLock);
elog(WARN,"WaitOnLock: error on wakeup - Aborting this transaction");
}
return(STATUS_OK);
}
/*
* LockRelease -- look up 'lockName' in lock table 'tableId' and
* release it.
*
* Side Effects: if the lock no longer conflicts with the highest
* priority waiting process, that process is granted the lock
* and awoken. (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(LockTableId tableId, LOCKTAG *lockName, LOCKT lockt)
{
LOCK *lock = NULL;
SPINLOCK masterLock;
bool found;
LOCKTAB *ltable;
XIDLookupEnt *result,item;
HTAB *xidTable;
bool wakeupNeeded = true;
#ifdef USER_LOCKS
int is_user_lock;
is_user_lock = (tableId == 0);
if (is_user_lock) {
tableId = 1;
#ifdef USER_LOCKS_DEBUG
elog(NOTICE,"LockRelease: user lock tag [%u,%u] %d",
lockName->tupleId.ip_posid,
((lockName->tupleId.ip_blkid.bi_hi<<16)+
lockName->tupleId.ip_blkid.bi_lo),
lockt);
#endif
}
#endif
Assert (tableId < NumTables);
ltable = AllTables[tableId];
if (!ltable) {
elog(NOTICE, "ltable is null in LockRelease");
return (FALSE);
}
if (LockingIsDisabled)
{
return(TRUE);
}
LOCK_PRINT("Release",lockName,lockt);
masterLock = ltable->ctl->masterLock;
xidTable = ltable->xidHash;
SpinAcquire(masterLock);
Assert( ltable->lockHash->hash == tag_hash);
lock = (LOCK *)
hash_search(ltable->lockHash,(Pointer)lockName,HASH_FIND_SAVE,&found);
#ifdef USER_LOCKS
/*
* If the entry is not found hash_search returns TRUE
* instead of NULL, so we must check it explicitly.
*/
if ((is_user_lock) && (lock == (LOCK *)TRUE)) {
SpinRelease(masterLock);
elog(NOTICE,"LockRelease: there are no locks with this tag");
return(FALSE);
}
#endif
/* let the caller print its own error message, too.
* Do not elog(WARN).
*/
if (! lock)
{
SpinRelease(masterLock);
elog(NOTICE,"LockRelease: locktable corrupted");
return(FALSE);
}
if (! found)
{
SpinRelease(masterLock);
elog(NOTICE,"LockRelease: locktable lookup failed, no lock");
return(FALSE);
}
Assert(lock->nHolding > 0);
#ifdef USER_LOCKS
/*
* If this is an user lock it can be removed only after
* checking that it was acquired by the current process,
* so this code is skipped and executed later.
*/
if (!is_user_lock) {
#endif
/*
* fix the general lock stats
*/
lock->nHolding--;
lock->holders[lockt]--;
lock->nActive--;
lock->activeHolders[lockt]--;
Assert(lock->nActive >= 0);
if (! lock->nHolding)
{
/* ------------------
* if there's no one waiting in the queue,
* we just released the last lock.
* Delete it from the lock table.
* ------------------
*/
Assert( ltable->lockHash->hash == tag_hash);
lock = (LOCK *) hash_search(ltable->lockHash,
(Pointer) &(lock->tag),
HASH_REMOVE_SAVED,
&found);
Assert(lock && found);
wakeupNeeded = false;
}
#ifdef USER_LOCKS
}
#endif
/* ------------------
* Zero out all of the tag bytes (this clears the padding bytes for long
* word alignment and ensures hashing consistency).
* ------------------
*/
memset(&item, 0, XID_TAGSIZE);
TransactionIdStore(GetCurrentTransactionId(), &item.tag.xid);
item.tag.lock = MAKE_OFFSET(lock);
#if 0
item.tag.pid = MyPid;
#endif
#ifdef USER_LOCKS
if (is_user_lock) {
item.tag.pid = getpid();
item.tag.xid = 0;
#ifdef USER_LOCKS_DEBUG
elog(NOTICE,"LockRelease: user lock xid [%d,%d,%d]",
item.tag.lock, item.tag.pid, item.tag.xid);
#endif
}
#endif
if (! ( result = (XIDLookupEnt *) hash_search(xidTable,
(Pointer)&item,
HASH_FIND_SAVE,
&found) )
|| !found)
{
SpinRelease(masterLock);
#ifdef USER_LOCKS
if ((is_user_lock) && (result)) {
elog(NOTICE,"LockRelease: you don't have a lock on this tag");
} else {
elog(NOTICE,"LockRelease: find xid, table corrupted");
}
#else
elog(NOTICE,"LockReplace: xid table corrupted");
#endif
return(FALSE);
}
/*
* now check to see if I have any private locks. If I do,
* decrement the counts associated with them.
*/
result->holders[lockt]--;
result->nHolding--;
XID_PRINT("LockRelease updated xid stats", result);
/*
* If this was my last hold on this lock, delete my entry
* in the XID table.
*/
if (! result->nHolding)
{
#ifdef USER_LOCKS
if (result->queue.prev == INVALID_OFFSET) {
elog(NOTICE,"LockRelease: xid.prev == INVALID_OFFSET");
}
if (result->queue.next == INVALID_OFFSET) {
elog(NOTICE,"LockRelease: xid.next == INVALID_OFFSET");
}
#endif
if (result->queue.next != INVALID_OFFSET)
SHMQueueDelete(&result->queue);
if (! (result = (XIDLookupEnt *)
hash_search(xidTable, (Pointer)&item, HASH_REMOVE_SAVED, &found)) ||
! found)
{
SpinRelease(masterLock);
#ifdef USER_LOCKS
elog(NOTICE,"LockRelease: remove xid, table corrupted");
#else
elog(NOTICE,"LockReplace: xid table corrupted");
#endif
return(FALSE);
}
}
#ifdef USER_LOCKS
/*
* If this is an user lock remove it now, after the
* corresponding xid entry has been found and deleted.
*/
if (is_user_lock) {
/*
* fix the general lock stats
*/
lock->nHolding--;
lock->holders[lockt]--;
lock->nActive--;
lock->activeHolders[lockt]--;
Assert(lock->nActive >= 0);
if (! lock->nHolding)
{
/* ------------------
* if there's no one waiting in the queue,
* we just released the last lock.
* Delete it from the lock table.
* ------------------
*/
Assert( ltable->lockHash->hash == tag_hash);
lock = (LOCK *) hash_search(ltable->lockHash,
(Pointer) &(lock->tag),
HASH_REMOVE,
&found);
Assert(lock && found);
wakeupNeeded = false;
}
}
#endif
/* --------------------------
* If there are still active locks of the type I just released, no one
* should be woken up. Whoever is asleep will still conflict
* with the remaining locks.
* --------------------------
*/
if (! (lock->activeHolders[lockt]))
{
/* change the conflict mask. No more of this lock type. */
lock->mask &= BITS_OFF[lockt];
}
if (wakeupNeeded)
{
/* --------------------------
* Wake the first waiting process and grant him the lock if it
* doesn't conflict. The woken process must record the lock
* himself.
* --------------------------
*/
(void) ProcLockWakeup(&(lock->waitProcs), (char *) ltable, (char *) lock);
}
SpinRelease(masterLock);
return(TRUE);
}
/*
* GrantLock -- udpate the lock data structure to show
* the new lock holder.
*/
void
GrantLock(LOCK *lock, LOCKT lockt)
{
lock->nActive++;
lock->activeHolders[lockt]++;
lock->mask |= BITS_ON[lockt];
}
#ifdef USER_LOCKS
/*
* LockReleaseAll -- Release all locks in a process lock queue.
*
* Note: This code is a little complicated by the presence in the
* same queue of user locks which can't be removed from the
* normal lock queue at the end of a transaction. They must
* however be removed when the backend exits.
* A dummy tableId 0 is used to indicate that we are releasing
* the user locks, from the code added to ProcKill().
*/
#endif
bool
LockReleaseAll(LockTableId tableId, SHM_QUEUE *lockQueue)
{
PROC_QUEUE *waitQueue;
int done;
XIDLookupEnt *xidLook = NULL;
XIDLookupEnt *tmp = NULL;
SHMEM_OFFSET end = MAKE_OFFSET(lockQueue);
SPINLOCK masterLock;
LOCKTAB *ltable;
int i,nLockTypes;
LOCK *lock;
bool found;
#ifdef USER_LOCKS
int is_user_lock_table, my_pid, count, nskip;
is_user_lock_table = (tableId == 0);
my_pid = getpid();
#ifdef USER_LOCKS_DEBUG
elog(NOTICE,"LockReleaseAll: tableId=%d, pid=%d", tableId, my_pid);
#endif
if (is_user_lock_table) {
tableId = 1;
}
#endif
Assert (tableId < NumTables);
ltable = AllTables[tableId];
if (!ltable)
return (FALSE);
nLockTypes = ltable->ctl->nLockTypes;
masterLock = ltable->ctl->masterLock;
if (SHMQueueEmpty(lockQueue))
return TRUE;
#ifdef USER_LOCKS
SpinAcquire(masterLock);
#endif
SHMQueueFirst(lockQueue,(Pointer*)&xidLook,&xidLook->queue);
XID_PRINT("LockReleaseAll:", xidLook);
#ifndef USER_LOCKS
SpinAcquire(masterLock);
#else
count = nskip = 0;
#endif
for (;;)
{
/* ---------------------------
* XXX Here we assume the shared memory queue is circular and
* that we know its internal structure. Should have some sort of
* macros to allow one to walk it. mer 20 July 1991
* ---------------------------
*/
done = (xidLook->queue.next == end);
lock = (LOCK *) MAKE_PTR(xidLook->tag.lock);
LOCK_PRINT("ReleaseAll",(&lock->tag),0);
#ifdef USER_LOCKS
/*
* Sometimes the queue appears to be messed up.
*/
if (count++ > 2000) {
elog(NOTICE,"LockReleaseAll: xid loop detected, giving up");
nskip = 0;
break;
}
if (is_user_lock_table) {
if ((xidLook->tag.pid == 0) || (xidLook->tag.xid != 0)) {
#ifdef USER_LOCKS_DEBUG
elog(NOTICE,"LockReleaseAll: skip normal lock [%d,%d,%d]",
xidLook->tag.lock,xidLook->tag.pid,xidLook->tag.xid);
#endif
nskip++;
goto next_item;
}
if (xidLook->tag.pid != my_pid) {
/* This should never happen */
#ifdef USER_LOCKS_DEBUG
elog(NOTICE,
"LockReleaseAll: skip other pid [%u,%u] [%d,%d,%d]",
lock->tag.tupleId.ip_posid,
((lock->tag.tupleId.ip_blkid.bi_hi<<16)+
lock->tag.tupleId.ip_blkid.bi_lo),
xidLook->tag.lock,xidLook->tag.pid,xidLook->tag.xid);
#endif
nskip++;
goto next_item;
}
#ifdef USER_LOCKS_DEBUG
elog(NOTICE,
"LockReleaseAll: release user lock [%u,%u] [%d,%d,%d]",
lock->tag.tupleId.ip_posid,
((lock->tag.tupleId.ip_blkid.bi_hi<<16)+
lock->tag.tupleId.ip_blkid.bi_lo),
xidLook->tag.lock,xidLook->tag.pid,xidLook->tag.xid);
#endif
} else {
if ((xidLook->tag.pid != 0) || (xidLook->tag.xid == 0)) {
#ifdef USER_LOCKS_DEBUG
elog(NOTICE,
"LockReleaseAll: skip user lock [%u,%u] [%d,%d,%d]",
lock->tag.tupleId.ip_posid,
((lock->tag.tupleId.ip_blkid.bi_hi<<16)+
lock->tag.tupleId.ip_blkid.bi_lo),
xidLook->tag.lock,xidLook->tag.pid,xidLook->tag.xid);
#endif
nskip++;
goto next_item;
}
#ifdef USER_LOCKS_DEBUG
elog(NOTICE,"LockReleaseAll: release normal lock [%d,%d,%d]",
xidLook->tag.lock,xidLook->tag.pid,xidLook->tag.xid);
#endif
}
#endif
/* ------------------
* fix the general lock stats
* ------------------
*/
if (lock->nHolding != xidLook->nHolding)
{
lock->nHolding -= xidLook->nHolding;
lock->nActive -= xidLook->nHolding;
Assert(lock->nActive >= 0);
for (i=1; i<=nLockTypes; i++)
{
lock->holders[i] -= xidLook->holders[i];
lock->activeHolders[i] -= xidLook->holders[i];
if (! lock->activeHolders[i])
lock->mask &= BITS_OFF[i];
}
}
else
{
/* --------------
* set nHolding to zero so that we can garbage collect the lock
* down below...
* --------------
*/
lock->nHolding = 0;
}
/* ----------------
* always remove the xidLookup entry, we're done with it now
* ----------------
*/
#ifdef USER_LOCKS
SHMQueueDelete(&xidLook->queue);
#endif
if ((! hash_search(ltable->xidHash, (Pointer)xidLook, HASH_REMOVE, &found))
|| !found)
{
SpinRelease(masterLock);
#ifdef USER_LOCKS
elog(NOTICE,"LockReleaseAll: xid table corrupted");
#else
elog(NOTICE,"LockReplace: xid table corrupted");
#endif
return(FALSE);
}
if (! lock->nHolding)
{
/* --------------------
* if there's no one waiting in the queue, we've just released
* the last lock.
* --------------------
*/
Assert( ltable->lockHash->hash == tag_hash);
lock = (LOCK *)
hash_search(ltable->lockHash,(Pointer)&(lock->tag),HASH_REMOVE, &found);
if ((! lock) || (!found))
{
SpinRelease(masterLock);
#ifdef USER_LOCKS
elog(NOTICE,"LockReleaseAll: cannot remove lock from HTAB");
#else
elog(NOTICE,"LockReplace: cannot remove lock from HTAB");
#endif
return(FALSE);
}
}
else
{
/* --------------------
* Wake the first waiting process and grant him the lock if it
* doesn't conflict. The woken process must record the lock
* him/herself.
* --------------------
*/
waitQueue = &(lock->waitProcs);
(void) ProcLockWakeup(waitQueue, (char *) ltable, (char *) lock);
}
#ifdef USER_LOCKS
next_item:
#endif
if (done)
break;
SHMQueueFirst(&xidLook->queue,(Pointer*)&tmp,&tmp->queue);
xidLook = tmp;
}
SpinRelease(masterLock);
#ifdef USER_LOCKS
/*
* Reinitialize the queue only if nothing has been left in.
*/
if (nskip == 0)
#endif
SHMQueueInit(lockQueue);
return TRUE;
}
int
LockShmemSize()
{
int size = 0;
int nLockBuckets, nLockSegs;
int nXidBuckets, nXidSegs;
nLockBuckets = 1 << (int)my_log2((NLOCKENTS - 1) / DEF_FFACTOR + 1);
nLockSegs = 1 << (int)my_log2((nLockBuckets - 1) / DEF_SEGSIZE + 1);
nXidBuckets = 1 << (int)my_log2((NLOCKS_PER_XACT-1) / DEF_FFACTOR + 1);
nXidSegs = 1 << (int)my_log2((nLockBuckets - 1) / DEF_SEGSIZE + 1);
size += MAXALIGN(NBACKENDS * sizeof(PROC)); /* each MyProc */
size += MAXALIGN(NBACKENDS * sizeof(LOCKCTL)); /* each ltable->ctl */
size += MAXALIGN(sizeof(PROC_HDR)); /* ProcGlobal */
size += MAXALIGN(my_log2(NLOCKENTS) * sizeof(void *));
size += MAXALIGN(sizeof(HHDR));
size += nLockSegs * MAXALIGN(DEF_SEGSIZE * sizeof(SEGMENT));
size += NLOCKENTS * /* XXX not multiple of BUCKET_ALLOC_INCR? */
(MAXALIGN(sizeof(BUCKET_INDEX)) +
MAXALIGN(sizeof(LOCK))); /* contains hash key */
size += MAXALIGN(my_log2(NBACKENDS) * sizeof(void *));
size += MAXALIGN(sizeof(HHDR));
size += nXidSegs * MAXALIGN(DEF_SEGSIZE * sizeof(SEGMENT));
size += NBACKENDS * /* XXX not multiple of BUCKET_ALLOC_INCR? */
(MAXALIGN(sizeof(BUCKET_INDEX)) +
MAXALIGN(sizeof(XIDLookupEnt))); /* contains hash key */
return size;
}
/* -----------------
* Boolean function to determine current locking status
* -----------------
*/
bool
LockingDisabled()
{
return LockingIsDisabled;
}