@ -7,7 +7,7 @@
* Portions Copyright ( c ) 1996 - 2003 , PostgreSQL Global Development Group * Portions Copyright ( c ) 1996 - 2003 , PostgreSQL Global Development Group
* Portions Copyright ( c ) 1994 , Regents of the University of California * Portions Copyright ( c ) 1994 , Regents of the University of California
* *
* $ PostgreSQL : pgsql / src / include / storage / lock . h , v 1.80 2004 / 08 / 26 17 : 22 : 28 tgl Exp $ * $ PostgreSQL : pgsql / src / include / storage / lock . h , v 1.81 2004 / 08 / 27 17 : 07 : 42 tgl Exp $
* *
* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - * - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
*/ */
@ -69,15 +69,17 @@ typedef uint16 LOCKMETHODID;
# define LockMethodIsValid(lockmethodid) ((lockmethodid) != INVALID_LOCKMETHOD) # define LockMethodIsValid(lockmethodid) ((lockmethodid) != INVALID_LOCKMETHOD)
extern int NumLockMethods ;
/*
/*
* This is the control structure for a lock table . It lives in shared * This is the control structure for a lock table . It lives in shared
* memory . Currently , none of these fields change after startup . In addition * memory . Currently , none of these fields change after startup . In addition
* to the LockMethodData , a lock table has a " lockHash " table holding * to the LockMethodData , a lock table has a shared " lockHash " table holding
* per - locked - object lock information , and a " proclockHash " table holding * per - locked - object lock information , and a shared " proclockHash " table
* per - lock - holder / waiter lock information . * holding per - lock - holder / waiter lock information .
* *
* lockmethodid - - the handle used by the lock table ' s clients to * masterLock - - LWLock used to synchronize access to the table
* refer to the type of lock table being used .
* *
* numLockModes - - number of lock types ( READ , WRITE , etc ) that * numLockModes - - number of lock types ( READ , WRITE , etc ) that
* are defined on this lock table * are defined on this lock table
@ -85,16 +87,14 @@ typedef uint16 LOCKMETHODID;
* conflictTab - - this is an array of bitmasks showing lock * conflictTab - - this is an array of bitmasks showing lock
* type conflicts . conflictTab [ i ] is a mask with the j - th bit * type conflicts . conflictTab [ i ] is a mask with the j - th bit
* turned on if lock types i and j conflict . * turned on if lock types i and j conflict .
*
* masterLock - - LWLock used to synchronize access to the table
*/ */
typedef struct LockMethodData typedef struct LockMethodData
{ {
LOCKMETHODID lockmethodid ; LWLockId masterLock ;
int numLockModes ; int numLockModes ;
LOCKMASK conflictTab [ MAX_LOCKMODES ] ; LOCKMASK conflictTab [ MAX_LOCKMODES ] ;
LWLockId masterLock ;
} LockMethodData ; } LockMethodData ;
typedef LockMethodData * LockMethod ; typedef LockMethodData * LockMethod ;
@ -113,8 +113,8 @@ typedef struct LOCKTAG
} objId ; } objId ;
/*
/*
* offnum should be part of objId . tupleId above , but would increase * offnum should be part of objId union above , but doing that would
* sizeof ( LOCKTAG ) and so moved here ; c urrentlyused by userlocks * increase sizeof ( LOCKTAG ) due to padding . C urrentlyused by userlocks
* only . * only .
*/ */
OffsetNumber offnum ; OffsetNumber offnum ;
@ -129,7 +129,7 @@ typedef struct LOCKTAG
* tag - - uniquely identifies the object being locked * tag - - uniquely identifies the object being locked
* grantMask - - bitmask for all lock types currently granted on this object . * grantMask - - bitmask for all lock types currently granted on this object .
* waitMask - - bitmask for all lock types currently awaited on this object . * waitMask - - bitmask for all lock types currently awaited on this object .
* lockHolder s- - list of PROCLOCK objects for this lock . * procLock s- - list of PROCLOCK objects for this lock .
* waitProcs - - queue of processes waiting for this lock . * waitProcs - - queue of processes waiting for this lock .
* requested - - count of each lock type currently requested on the lock * requested - - count of each lock type currently requested on the lock
* ( includes requests already granted ! ! ) . * ( includes requests already granted ! ! ) .
@ -145,7 +145,7 @@ typedef struct LOCK
/* data */ /* data */
LOCKMASK grantMask ; /* bitmask for lock types already granted */ LOCKMASK grantMask ; /* bitmask for lock types already granted */
LOCKMASK waitMask ; /* bitmask for lock types awaited */ LOCKMASK waitMask ; /* bitmask for lock types awaited */
SHM_QUEUE lockHolders ; /* list of PROCLOCK objects assoc. with
SHM_QUEUE procLocks ; /* list of PROCLOCK objects assoc. with
* lock */ * lock */
PROC_QUEUE waitProcs ; /* list of PGPROC objects waiting on lock */ PROC_QUEUE waitProcs ; /* list of PGPROC objects waiting on lock */
int requested [ MAX_LOCKMODES ] ; /* counts of requested
int requested [ MAX_LOCKMODES ] ; /* counts of requested
@ -168,7 +168,7 @@ typedef struct LOCK
* proclock hashtable . A PROCLOCKTAG value uniquely identifies the combination * proclock hashtable . A PROCLOCKTAG value uniquely identifies the combination
* of a lockable object and a holder / waiter for that object . * of a lockable object and a holder / waiter for that object .
* *
* There are two possible kinds of proclock tag s: a transaction ( identified * There are two possible kinds of proclock owner s: a transaction ( identified
* both by the PGPROC of the backend running it , and the xact ' s own ID ) and * both by the PGPROC of the backend running it , and the xact ' s own ID ) and
* a session ( identified by backend PGPROC , with XID = InvalidTransactionId ) . * a session ( identified by backend PGPROC , with XID = InvalidTransactionId ) .
* *
@ -177,10 +177,10 @@ typedef struct LOCK
* under several different XIDs at once ( including session locks ) . We treat * under several different XIDs at once ( including session locks ) . We treat
* such locks as never conflicting ( a backend can never block itself ) . * such locks as never conflicting ( a backend can never block itself ) .
* *
* The holding [ ] array counts the granted locks ( of each type ) represented * The holdMask field shows the already - granted locks represented by this
* by this proclock . Note that there will be a proclock object , possibly with * proclock . Note that there will be a proclock object , possibly with
* zero holding [ ] , for any lock that the process is currently waiting on . * zero holdMask , for any lock that the process is currently waiting on .
* Otherwise , proclock objects whose counts have gone to zero are recycled * Otherwise , proclock objects whose holdMasks are zero are recycled
* as soon as convenient . * as soon as convenient .
* *
* Each PROCLOCK object is linked into lists for both the associated LOCK * Each PROCLOCK object is linked into lists for both the associated LOCK
@ -202,8 +202,7 @@ typedef struct PROCLOCK
PROCLOCKTAG tag ; /* unique identifier of proclock object */ PROCLOCKTAG tag ; /* unique identifier of proclock object */
/* data */ /* data */
int holding [ MAX_LOCKMODES ] ; /* count of locks currently held */ LOCKMASK holdMask ; /* bitmask for lock types currently held */
int nHolding ; /* total of holding[] array */
SHM_QUEUE lockLink ; /* list link for lock's list of proclocks */ SHM_QUEUE lockLink ; /* list link for lock's list of proclocks */
SHM_QUEUE procLink ; /* list link for process's list of
SHM_QUEUE procLink ; /* list link for process's list of
* proclocks */ * proclocks */
@ -212,6 +211,49 @@ typedef struct PROCLOCK
# define PROCLOCK_LOCKMETHOD(proclock) \ # define PROCLOCK_LOCKMETHOD(proclock) \
( ( ( LOCK * ) MAKE_PTR ( ( proclock ) . tag . lock ) ) - > tag . lockmethodid ) ( ( ( LOCK * ) MAKE_PTR ( ( proclock ) . tag . lock ) ) - > tag . lockmethodid )
/*
* Each backend also maintains a local hash table with information about each
* lock it is currently interested in . In particular the local table counts
* the number of times that lock has been acquired . This allows multiple
* requests for the same lock to be executed without additional accesses to
* shared memory . We also track the number of lock acquisitions per
* ResourceOwner , so that we can release just those locks belonging to a
* particular ResourceOwner .
*/
typedef struct LOCALLOCKTAG
{
LOCKTAG lock ; /* identifies the lockable object */
TransactionId xid ; /* xact ID, or InvalidTransactionId */
LOCKMODE mode ; /* lock mode for this table entry */
} LOCALLOCKTAG ;
typedef struct LOCALLOCKOWNER
{
/*
* Note : owner can be NULL to indicate a non - transactional lock .
* Must use a forward struct reference to avoid circularity .
*/
struct ResourceOwnerData * owner ;
int nLocks ; /* # of times held by this owner */
} LOCALLOCKOWNER ;
typedef struct LOCALLOCK
{
/* tag */
LOCALLOCKTAG tag ; /* unique identifier of locallock entry */
/* data */
LOCK * lock ; /* associated LOCK object in shared mem */
PROCLOCK * proclock ; /* associated PROCLOCK object in shmem */
int nLocks ; /* total number of times lock is held */
int numLockOwners ; /* # of relevant ResourceOwners */
int maxLockOwners ; /* allocated size of array */
LOCALLOCKOWNER * lockOwners ; /* dynamically resizable array */
} LOCALLOCK ;
# define LOCALLOCK_LOCKMETHOD(llock) ((llock).tag.lock.lockmethodid)
/*
/*
* This struct holds information passed from lmgr internals to the lock * This struct holds information passed from lmgr internals to the lock
* listing user - level functions ( lockfuncs . c ) . For each PROCLOCK in the * listing user - level functions ( lockfuncs . c ) . For each PROCLOCK in the
@ -229,7 +271,6 @@ typedef struct
LOCK * locks ; LOCK * locks ;
} LockData ; } LockData ;
extern int NumLockMethods ;
/*
/*
* function prototypes * function prototypes
@ -244,13 +285,15 @@ extern bool LockAcquire(LOCKMETHODID lockmethodid, LOCKTAG *locktag,
TransactionId xid , LOCKMODE lockmode , bool dontWait ) ; TransactionId xid , LOCKMODE lockmode , bool dontWait ) ;
extern bool LockRelease ( LOCKMETHODID lockmethodid , LOCKTAG * locktag , extern bool LockRelease ( LOCKMETHODID lockmethodid , LOCKTAG * locktag ,
TransactionId xid , LOCKMODE lockmode ) ; TransactionId xid , LOCKMODE lockmode ) ;
extern bool LockReleaseAll ( LOCKMETHODID lockmethodid , PGPROC * proc , extern bool LockReleaseAll ( LOCKMETHODID lockmethodid , bool allxids ) ;
bool allxids ) ; extern void LockReleaseCurrentOwner ( void ) ;
extern void LockReassignCurrentOwner ( void ) ;
extern int LockCheckConflicts ( LockMethod lockMethodTable , extern int LockCheckConflicts ( LockMethod lockMethodTable ,
LOCKMODE lockmode , LOCKMODE lockmode ,
LOCK * lock , PROCLOCK * proclock , PGPROC * proc , LOCK * lock , PROCLOCK * proclock , PGPROC * proc ,
int * myHolding ) ; int * myHolding ) ;
extern void GrantLock ( LOCK * lock , PROCLOCK * proclock , LOCKMODE lockmode ) ; extern void GrantLock ( LOCK * lock , PROCLOCK * proclock , LOCKMODE lockmode ) ;
extern void GrantAwaitedLock ( void ) ;
extern void RemoveFromWaitQueue ( PGPROC * proc ) ; extern void RemoveFromWaitQueue ( PGPROC * proc ) ;
extern int LockShmemSize ( int maxBackends ) ; extern int LockShmemSize ( int maxBackends ) ;
extern bool DeadLockCheck ( PGPROC * proc ) ; extern bool DeadLockCheck ( PGPROC * proc ) ;
Tom Lane
21 years ago