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/*-------------------------------------------------------------------------
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* POSTGRES low-level lock mechanism
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* Portions Copyright (c) 1996-2011, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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* src/include/storage/lock.h
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*-------------------------------------------------------------------------
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#include "storage/backendid.h"
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#include "storage/lwlock.h"
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#include "storage/shmem.h"
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/* struct PGPROC is declared in proc.h, but must forward-reference it */
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typedef struct PGPROC PGPROC;
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typedef struct PROC_QUEUE
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SHM_QUEUE links; /* head of list of PGPROC objects */
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int size; /* number of entries in list */
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extern int max_locks_per_xact;
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extern int Trace_lock_oidmin;
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extern bool Trace_locks;
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extern bool Trace_userlocks;
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extern int Trace_lock_table;
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extern bool Debug_deadlocks;
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#endif /* LOCK_DEBUG */
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* Top-level transactions are identified by VirtualTransactionIDs comprising
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* the BackendId of the backend running the xact, plus a locally-assigned
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* LocalTransactionId. These are guaranteed unique over the short term,
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* but will be reused after a database restart; hence they should never
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* Note that struct VirtualTransactionId can not be assumed to be atomically
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* assignable as a whole. However, type LocalTransactionId is assumed to
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* be atomically assignable, and the backend ID doesn't change often enough
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* to be a problem, so we can fetch or assign the two fields separately.
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* We deliberately refrain from using the struct within PGPROC, to prevent
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* coding errors from trying to use struct assignment with it; instead use
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* GET_VXID_FROM_PGPROC().
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BackendId backendId; /* determined at backend startup */
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LocalTransactionId localTransactionId; /* backend-local transaction
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} VirtualTransactionId;
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#define InvalidLocalTransactionId 0
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#define LocalTransactionIdIsValid(lxid) ((lxid) != InvalidLocalTransactionId)
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#define VirtualTransactionIdIsValid(vxid) \
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(((vxid).backendId != InvalidBackendId) && \
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LocalTransactionIdIsValid((vxid).localTransactionId))
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#define VirtualTransactionIdEquals(vxid1, vxid2) \
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((vxid1).backendId == (vxid2).backendId && \
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(vxid1).localTransactionId == (vxid2).localTransactionId)
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#define SetInvalidVirtualTransactionId(vxid) \
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((vxid).backendId = InvalidBackendId, \
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(vxid).localTransactionId = InvalidLocalTransactionId)
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#define GET_VXID_FROM_PGPROC(vxid, proc) \
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((vxid).backendId = (proc).backendId, \
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(vxid).localTransactionId = (proc).lxid)
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* LOCKMODE is an integer (1..N) indicating a lock type. LOCKMASK is a bit
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* mask indicating a set of held or requested lock types (the bit 1<<mode
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* corresponds to a particular lock mode).
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/* MAX_LOCKMODES cannot be larger than the # of bits in LOCKMASK */
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#define MAX_LOCKMODES 10
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#define LOCKBIT_ON(lockmode) (1 << (lockmode))
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#define LOCKBIT_OFF(lockmode) (~(1 << (lockmode)))
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* This data structure defines the locking semantics associated with a
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* "lock method". The semantics specify the meaning of each lock mode
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* (by defining which lock modes it conflicts with), and also whether locks
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* of this method are transactional (ie, are released at transaction end).
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* All of this data is constant and is kept in const tables.
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* numLockModes -- number of lock modes (READ,WRITE,etc) that
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* are defined in this lock method. Must be less than MAX_LOCKMODES.
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* transactional -- TRUE if locks are released automatically at xact end.
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* conflictTab -- this is an array of bitmasks showing lock
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* mode conflicts. conflictTab[i] is a mask with the j-th bit
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* turned on if lock modes i and j conflict. Lock modes are
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* numbered 1..numLockModes; conflictTab[0] is unused.
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* lockModeNames -- ID strings for debug printouts.
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* trace_flag -- pointer to GUC trace flag for this lock method.
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typedef struct LockMethodData
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const LOCKMASK *conflictTab;
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const char *const * lockModeNames;
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const bool *trace_flag;
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typedef const LockMethodData *LockMethod;
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* Lock methods are identified by LOCKMETHODID. (Despite the declaration as
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* uint16, we are constrained to 256 lockmethods by the layout of LOCKTAG.)
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typedef uint16 LOCKMETHODID;
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/* These identify the known lock methods */
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#define DEFAULT_LOCKMETHOD 1
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#define USER_LOCKMETHOD 2
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* These are the valid values of type LOCKMODE for all the standard lock
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* methods (both DEFAULT and USER).
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/* NoLock is not a lock mode, but a flag value meaning "don't get a lock" */
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#define AccessShareLock 1 /* SELECT */
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#define RowShareLock 2 /* SELECT FOR UPDATE/FOR SHARE */
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#define RowExclusiveLock 3 /* INSERT, UPDATE, DELETE */
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#define ShareUpdateExclusiveLock 4 /* VACUUM (non-FULL),ANALYZE, CREATE
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* INDEX CONCURRENTLY */
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#define ShareLock 5 /* CREATE INDEX (WITHOUT CONCURRENTLY) */
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#define ShareRowExclusiveLock 6 /* like EXCLUSIVE MODE, but allows ROW
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#define ExclusiveLock 7 /* blocks ROW SHARE/SELECT...FOR
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#define AccessExclusiveLock 8 /* ALTER TABLE, DROP TABLE, VACUUM
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* FULL, and unqualified LOCK TABLE */
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* LOCKTAG is the key information needed to look up a LOCK item in the
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* lock hashtable. A LOCKTAG value uniquely identifies a lockable object.
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* The LockTagType enum defines the different kinds of objects we can lock.
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* We can handle up to 256 different LockTagTypes.
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typedef enum LockTagType
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LOCKTAG_RELATION, /* whole relation */
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/* ID info for a relation is DB OID + REL OID; DB OID = 0 if shared */
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LOCKTAG_RELATION_EXTEND, /* the right to extend a relation */
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/* same ID info as RELATION */
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LOCKTAG_PAGE, /* one page of a relation */
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/* ID info for a page is RELATION info + BlockNumber */
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LOCKTAG_TUPLE, /* one physical tuple */
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/* ID info for a tuple is PAGE info + OffsetNumber */
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LOCKTAG_TRANSACTION, /* transaction (for waiting for xact done) */
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/* ID info for a transaction is its TransactionId */
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LOCKTAG_VIRTUALTRANSACTION, /* virtual transaction (ditto) */
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/* ID info for a virtual transaction is its VirtualTransactionId */
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LOCKTAG_OBJECT, /* non-relation database object */
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/* ID info for an object is DB OID + CLASS OID + OBJECT OID + SUBID */
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* Note: object ID has same representation as in pg_depend and
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* pg_description, but notice that we are constraining SUBID to 16 bits.
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* Also, we use DB OID = 0 for shared objects such as tablespaces.
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LOCKTAG_USERLOCK, /* reserved for old contrib/userlock code */
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LOCKTAG_ADVISORY /* advisory user locks */
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#define LOCKTAG_LAST_TYPE LOCKTAG_ADVISORY
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* The LOCKTAG struct is defined with malice aforethought to fit into 16
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* bytes with no padding. Note that this would need adjustment if we were
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* to widen Oid, BlockNumber, or TransactionId to more than 32 bits.
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* We include lockmethodid in the locktag so that a single hash table in
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* shared memory can store locks of different lockmethods.
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typedef struct LOCKTAG
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uint32 locktag_field1; /* a 32-bit ID field */
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uint32 locktag_field2; /* a 32-bit ID field */
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uint32 locktag_field3; /* a 32-bit ID field */
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uint16 locktag_field4; /* a 16-bit ID field */
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uint8 locktag_type; /* see enum LockTagType */
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uint8 locktag_lockmethodid; /* lockmethod indicator */
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* These macros define how we map logical IDs of lockable objects into
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* the physical fields of LOCKTAG. Use these to set up LOCKTAG values,
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* rather than accessing the fields directly. Note multiple eval of target!
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#define SET_LOCKTAG_RELATION(locktag,dboid,reloid) \
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((locktag).locktag_field1 = (dboid), \
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(locktag).locktag_field2 = (reloid), \
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(locktag).locktag_field3 = 0, \
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(locktag).locktag_field4 = 0, \
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(locktag).locktag_type = LOCKTAG_RELATION, \
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(locktag).locktag_lockmethodid = DEFAULT_LOCKMETHOD)
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#define SET_LOCKTAG_RELATION_EXTEND(locktag,dboid,reloid) \
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((locktag).locktag_field1 = (dboid), \
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(locktag).locktag_field2 = (reloid), \
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(locktag).locktag_field3 = 0, \
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(locktag).locktag_field4 = 0, \
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(locktag).locktag_type = LOCKTAG_RELATION_EXTEND, \
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(locktag).locktag_lockmethodid = DEFAULT_LOCKMETHOD)
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#define SET_LOCKTAG_PAGE(locktag,dboid,reloid,blocknum) \
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((locktag).locktag_field1 = (dboid), \
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(locktag).locktag_field2 = (reloid), \
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(locktag).locktag_field3 = (blocknum), \
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(locktag).locktag_field4 = 0, \
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(locktag).locktag_type = LOCKTAG_PAGE, \
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(locktag).locktag_lockmethodid = DEFAULT_LOCKMETHOD)
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#define SET_LOCKTAG_TUPLE(locktag,dboid,reloid,blocknum,offnum) \
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((locktag).locktag_field1 = (dboid), \
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(locktag).locktag_field2 = (reloid), \
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(locktag).locktag_field3 = (blocknum), \
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(locktag).locktag_field4 = (offnum), \
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(locktag).locktag_type = LOCKTAG_TUPLE, \
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(locktag).locktag_lockmethodid = DEFAULT_LOCKMETHOD)
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#define SET_LOCKTAG_TRANSACTION(locktag,xid) \
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((locktag).locktag_field1 = (xid), \
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(locktag).locktag_field2 = 0, \
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(locktag).locktag_field3 = 0, \
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(locktag).locktag_field4 = 0, \
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(locktag).locktag_type = LOCKTAG_TRANSACTION, \
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(locktag).locktag_lockmethodid = DEFAULT_LOCKMETHOD)
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#define SET_LOCKTAG_VIRTUALTRANSACTION(locktag,vxid) \
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((locktag).locktag_field1 = (vxid).backendId, \
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(locktag).locktag_field2 = (vxid).localTransactionId, \
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(locktag).locktag_field3 = 0, \
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(locktag).locktag_field4 = 0, \
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(locktag).locktag_type = LOCKTAG_VIRTUALTRANSACTION, \
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(locktag).locktag_lockmethodid = DEFAULT_LOCKMETHOD)
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#define SET_LOCKTAG_OBJECT(locktag,dboid,classoid,objoid,objsubid) \
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((locktag).locktag_field1 = (dboid), \
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(locktag).locktag_field2 = (classoid), \
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(locktag).locktag_field3 = (objoid), \
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(locktag).locktag_field4 = (objsubid), \
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(locktag).locktag_type = LOCKTAG_OBJECT, \
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(locktag).locktag_lockmethodid = DEFAULT_LOCKMETHOD)
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#define SET_LOCKTAG_ADVISORY(locktag,id1,id2,id3,id4) \
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((locktag).locktag_field1 = (id1), \
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(locktag).locktag_field2 = (id2), \
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(locktag).locktag_field3 = (id3), \
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(locktag).locktag_field4 = (id4), \
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(locktag).locktag_type = LOCKTAG_ADVISORY, \
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(locktag).locktag_lockmethodid = USER_LOCKMETHOD)
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* Per-locked-object lock information:
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* tag -- uniquely identifies the object being locked
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* grantMask -- bitmask for all lock types currently granted on this object.
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* waitMask -- bitmask for all lock types currently awaited on this object.
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* procLocks -- list of PROCLOCK objects for this lock.
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* waitProcs -- queue of processes waiting for this lock.
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* requested -- count of each lock type currently requested on the lock
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* (includes requests already granted!!).
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* nRequested -- total requested locks of all types.
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* granted -- count of each lock type currently granted on the lock.
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* nGranted -- total granted locks of all types.
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* Note: these counts count 1 for each backend. Internally to a backend,
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* there may be multiple grabs on a particular lock, but this is not reflected
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* into shared memory.
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LOCKTAG tag; /* unique identifier of lockable object */
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LOCKMASK grantMask; /* bitmask for lock types already granted */
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LOCKMASK waitMask; /* bitmask for lock types awaited */
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SHM_QUEUE procLocks; /* list of PROCLOCK objects assoc. with lock */
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PROC_QUEUE waitProcs; /* list of PGPROC objects waiting on lock */
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int requested[MAX_LOCKMODES]; /* counts of requested locks */
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int nRequested; /* total of requested[] array */
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int granted[MAX_LOCKMODES]; /* counts of granted locks */
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int nGranted; /* total of granted[] array */
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#define LOCK_LOCKMETHOD(lock) ((LOCKMETHODID) (lock).tag.locktag_lockmethodid)
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* We may have several different backends holding or awaiting locks
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* on the same lockable object. We need to store some per-holder/waiter
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* information for each such holder (or would-be holder). This is kept in
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* PROCLOCKTAG is the key information needed to look up a PROCLOCK item in the
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* proclock hashtable. A PROCLOCKTAG value uniquely identifies the combination
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* of a lockable object and a holder/waiter for that object. (We can use
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* pointers here because the PROCLOCKTAG need only be unique for the lifespan
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* of the PROCLOCK, and it will never outlive the lock or the proc.)
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* Internally to a backend, it is possible for the same lock to be held
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* for different purposes: the backend tracks transaction locks separately
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* from session locks. However, this is not reflected in the shared-memory
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* state: we only track which backend(s) hold the lock. This is OK since a
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* backend can never block itself.
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* The holdMask field shows the already-granted locks represented by this
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* proclock. Note that there will be a proclock object, possibly with
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* zero holdMask, for any lock that the process is currently waiting on.
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* Otherwise, proclock objects whose holdMasks are zero are recycled
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* as soon as convenient.
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* releaseMask is workspace for LockReleaseAll(): it shows the locks due
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* to be released during the current call. This must only be examined or
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* set by the backend owning the PROCLOCK.
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* Each PROCLOCK object is linked into lists for both the associated LOCK
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* object and the owning PGPROC object. Note that the PROCLOCK is entered
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* into these lists as soon as it is created, even if no lock has yet been
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* granted. A PGPROC that is waiting for a lock to be granted will also be
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* linked into the lock's waitProcs queue.
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typedef struct PROCLOCKTAG
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/* NB: we assume this struct contains no padding! */
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LOCK *myLock; /* link to per-lockable-object information */
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PGPROC *myProc; /* link to PGPROC of owning backend */
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typedef struct PROCLOCK
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PROCLOCKTAG tag; /* unique identifier of proclock object */
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LOCKMASK holdMask; /* bitmask for lock types currently held */
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LOCKMASK releaseMask; /* bitmask for lock types to be released */
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SHM_QUEUE lockLink; /* list link in LOCK's list of proclocks */
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SHM_QUEUE procLink; /* list link in PGPROC's list of proclocks */
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#define PROCLOCK_LOCKMETHOD(proclock) \
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LOCK_LOCKMETHOD(*((proclock).tag.myLock))
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* Each backend also maintains a local hash table with information about each
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* lock it is currently interested in. In particular the local table counts
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* the number of times that lock has been acquired. This allows multiple
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* requests for the same lock to be executed without additional accesses to
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* shared memory. We also track the number of lock acquisitions per
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* ResourceOwner, so that we can release just those locks belonging to a
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* particular ResourceOwner.
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typedef struct LOCALLOCKTAG
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LOCKTAG lock; /* identifies the lockable object */
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LOCKMODE mode; /* lock mode for this table entry */
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typedef struct LOCALLOCKOWNER
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* Note: if owner is NULL then the lock is held on behalf of the session;
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* otherwise it is held on behalf of my current transaction.
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* Must use a forward struct reference to avoid circularity.
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struct ResourceOwnerData *owner;
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int64 nLocks; /* # of times held by this owner */
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typedef struct LOCALLOCK
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LOCALLOCKTAG tag; /* unique identifier of locallock entry */
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LOCK *lock; /* associated LOCK object in shared mem */
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PROCLOCK *proclock; /* associated PROCLOCK object in shmem */
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uint32 hashcode; /* copy of LOCKTAG's hash value */
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int64 nLocks; /* total number of times lock is held */
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int numLockOwners; /* # of relevant ResourceOwners */
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int maxLockOwners; /* allocated size of array */
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LOCALLOCKOWNER *lockOwners; /* dynamically resizable array */
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#define LOCALLOCK_LOCKMETHOD(llock) ((llock).tag.lock.locktag_lockmethodid)
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* This struct holds information passed from lmgr internals to the lock
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* listing user-level functions (in lockfuncs.c). For each PROCLOCK in
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* the system, copies of the PROCLOCK object and associated PGPROC and
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* LOCK objects are stored. Note there will often be multiple copies
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* of the same PGPROC or LOCK --- to detect whether two are the same,
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* compare the PROCLOCK tag fields.
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typedef struct LockData
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int nelements; /* The length of each of the arrays */
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/* Result codes for LockAcquire() */
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LOCKACQUIRE_NOT_AVAIL, /* lock not available, and dontWait=true */
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LOCKACQUIRE_OK, /* lock successfully acquired */
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LOCKACQUIRE_ALREADY_HELD /* incremented count for lock already held */
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/* Deadlock states identified by DeadLockCheck() */
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DS_NOT_YET_CHECKED, /* no deadlock check has run yet */
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DS_NO_DEADLOCK, /* no deadlock detected */
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DS_SOFT_DEADLOCK, /* deadlock avoided by queue rearrangement */
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DS_HARD_DEADLOCK, /* deadlock, no way out but ERROR */
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DS_BLOCKED_BY_AUTOVACUUM /* no deadlock; queue blocked by autovacuum
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* The lockmgr's shared hash tables are partitioned to reduce contention.
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* To determine which partition a given locktag belongs to, compute the tag's
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* hash code with LockTagHashCode(), then apply one of these macros.
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* NB: NUM_LOCK_PARTITIONS must be a power of 2!
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#define LockHashPartition(hashcode) \
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((hashcode) % NUM_LOCK_PARTITIONS)
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#define LockHashPartitionLock(hashcode) \
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((LWLockId) (FirstLockMgrLock + LockHashPartition(hashcode)))
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* function prototypes
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extern void InitLocks(void);
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extern LockMethod GetLocksMethodTable(const LOCK *lock);
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extern uint32 LockTagHashCode(const LOCKTAG *locktag);
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extern LockAcquireResult LockAcquire(const LOCKTAG *locktag,
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extern LockAcquireResult LockAcquireExtended(const LOCKTAG *locktag,
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bool report_memory_error);
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extern bool LockRelease(const LOCKTAG *locktag,
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LOCKMODE lockmode, bool sessionLock);
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extern void LockReleaseSession(LOCKMETHODID lockmethodid);
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extern void LockReleaseAll(LOCKMETHODID lockmethodid, bool allLocks);
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extern void LockReleaseCurrentOwner(void);
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extern void LockReassignCurrentOwner(void);
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extern VirtualTransactionId *GetLockConflicts(const LOCKTAG *locktag,
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extern void AtPrepare_Locks(void);
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extern void PostPrepare_Locks(TransactionId xid);
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extern int LockCheckConflicts(LockMethod lockMethodTable,
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LOCK *lock, PROCLOCK *proclock, PGPROC *proc);
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extern void GrantLock(LOCK *lock, PROCLOCK *proclock, LOCKMODE lockmode);
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extern void GrantAwaitedLock(void);
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extern void RemoveFromWaitQueue(PGPROC *proc, uint32 hashcode);
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extern Size LockShmemSize(void);
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extern LockData *GetLockStatusData(void);
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extern void ReportLockTableError(bool report);
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typedef struct xl_standby_lock
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TransactionId xid; /* xid of holder of AccessExclusiveLock */
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extern xl_standby_lock *GetRunningTransactionLocks(int *nlocks);
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extern const char *GetLockmodeName(LOCKMETHODID lockmethodid, LOCKMODE mode);
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extern void lock_twophase_recover(TransactionId xid, uint16 info,
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void *recdata, uint32 len);
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extern void lock_twophase_postcommit(TransactionId xid, uint16 info,
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void *recdata, uint32 len);
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extern void lock_twophase_postabort(TransactionId xid, uint16 info,
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void *recdata, uint32 len);
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extern void lock_twophase_standby_recover(TransactionId xid, uint16 info,
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void *recdata, uint32 len);
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extern DeadLockState DeadLockCheck(PGPROC *proc);
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extern PGPROC *GetBlockingAutoVacuumPgproc(void);
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extern void DeadLockReport(void);
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extern void RememberSimpleDeadLock(PGPROC *proc1,
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extern void InitDeadLockChecking(void);
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extern void DumpLocks(PGPROC *proc);
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extern void DumpAllLocks(void);
added
removed
src/include/storage/lock.h
