src/include/storage/lock.h

   1 /*-------------------------------------------------------------------------
   2  *
   3  * lock.h
   4  *        POSTGRES low-level lock mechanism
   5  *
   6  *
   7  * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
   8  * Portions Copyright (c) 1994, Regents of the University of California
   9  *
  10  * src/include/storage/lock.h
  11  *
  12  *-------------------------------------------------------------------------
  13  */
  14 #ifndef LOCK_H_
  15 #define LOCK_H_
  16
  17 #ifdef FRONTEND
  18 #error "lock.h may not be included from frontend code"
  19 #endif
  20
  21 #include "storage/backendid.h"
  22 #include "storage/lockdefs.h"
  23 #include "storage/lwlock.h"
  24 #include "storage/shmem.h"
  25 #include "utils/timestamp.h"
  26
  27 /* struct PGPROC is declared in proc.h, but must forward-reference it */
  28 typedef struct PGPROC PGPROC;
  29
  30 typedef struct PROC_QUEUE
  31 {
  32         SHM_QUEUE       links;                  /* head of list of PGPROC objects */
  33         int                     size;                   /* number of entries in list */
  34 } PROC_QUEUE;
  35
  36 /* GUC variables */
  37 extern int      max_locks_per_xact;
  38
  39 #ifdef LOCK_DEBUG
  40 extern int      Trace_lock_oidmin;
  41 extern bool Trace_locks;
  42 extern bool Trace_userlocks;
  43 extern int      Trace_lock_table;
  44 extern bool Debug_deadlocks;
  45 #endif                                                  /* LOCK_DEBUG */
  46
  47
  48 /*
  49  * Top-level transactions are identified by VirtualTransactionIDs comprising
  50  * PGPROC fields backendId and lxid.  For prepared transactions, the
  51  * LocalTransactionId is an ordinary XID.  These are guaranteed unique over
  52  * the short term, but will be reused after a database restart or XID
  53  * wraparound; hence they should never be stored on disk.
  54  *
  55  * Note that struct VirtualTransactionId can not be assumed to be atomically
  56  * assignable as a whole.  However, type LocalTransactionId is assumed to
  57  * be atomically assignable, and the backend ID doesn't change often enough
  58  * to be a problem, so we can fetch or assign the two fields separately.
  59  * We deliberately refrain from using the struct within PGPROC, to prevent
  60  * coding errors from trying to use struct assignment with it; instead use
  61  * GET_VXID_FROM_PGPROC().
  62  */
  63 typedef struct
  64 {
  65         BackendId       backendId;              /* backendId from PGPROC */
  66         LocalTransactionId localTransactionId;  /* lxid from PGPROC */
  67 } VirtualTransactionId;
  68
  69 #define InvalidLocalTransactionId               0
  70 #define LocalTransactionIdIsValid(lxid) ((lxid) != InvalidLocalTransactionId)
  71 #define VirtualTransactionIdIsValid(vxid) \
  72         (LocalTransactionIdIsValid((vxid).localTransactionId))
  73 #define VirtualTransactionIdIsPreparedXact(vxid) \
  74         ((vxid).backendId == InvalidBackendId)
  75 #define VirtualTransactionIdEquals(vxid1, vxid2) \
  76         ((vxid1).backendId == (vxid2).backendId && \
  77          (vxid1).localTransactionId == (vxid2).localTransactionId)
  78 #define SetInvalidVirtualTransactionId(vxid) \
  79         ((vxid).backendId = InvalidBackendId, \
  80          (vxid).localTransactionId = InvalidLocalTransactionId)
  81 #define GET_VXID_FROM_PGPROC(vxid, proc) \
  82         ((vxid).backendId = (proc).backendId, \
  83          (vxid).localTransactionId = (proc).lxid)
  84
  85 /* MAX_LOCKMODES cannot be larger than the # of bits in LOCKMASK */
  86 #define MAX_LOCKMODES           10
  87
  88 #define LOCKBIT_ON(lockmode) (1 << (lockmode))
  89 #define LOCKBIT_OFF(lockmode) (~(1 << (lockmode)))
  90
  91
  92 /*
  93  * This data structure defines the locking semantics associated with a
  94  * "lock method".  The semantics specify the meaning of each lock mode
  95  * (by defining which lock modes it conflicts with).
  96  * All of this data is constant and is kept in const tables.
  97  *
  98  * numLockModes -- number of lock modes (READ,WRITE,etc) that
  99  *              are defined in this lock method.  Must be less than MAX_LOCKMODES.
 100  *
 101  * conflictTab -- this is an array of bitmasks showing lock
 102  *              mode conflicts.  conflictTab[i] is a mask with the j-th bit
 103  *              turned on if lock modes i and j conflict.  Lock modes are
 104  *              numbered 1..numLockModes; conflictTab[0] is unused.
 105  *
 106  * lockModeNames -- ID strings for debug printouts.
 107  *
 108  * trace_flag -- pointer to GUC trace flag for this lock method.  (The
 109  * GUC variable is not constant, but we use "const" here to denote that
 110  * it can't be changed through this reference.)
 111  */
 112 typedef struct LockMethodData
 113 {
 114         int                     numLockModes;
 115         const LOCKMASK *conflictTab;
 116         const char *const *lockModeNames;
 117         const bool *trace_flag;
 118 } LockMethodData;
 119
 120 typedef const LockMethodData *LockMethod;
 121
 122 /*
 123  * Lock methods are identified by LOCKMETHODID.  (Despite the declaration as
 124  * uint16, we are constrained to 256 lockmethods by the layout of LOCKTAG.)
 125  */
 126 typedef uint16 LOCKMETHODID;
 127
 128 /* These identify the known lock methods */
 129 #define DEFAULT_LOCKMETHOD      1
 130 #define USER_LOCKMETHOD         2
 131
 132 /*
 133  * LOCKTAG is the key information needed to look up a LOCK item in the
 134  * lock hashtable.  A LOCKTAG value uniquely identifies a lockable object.
 135  *
 136  * The LockTagType enum defines the different kinds of objects we can lock.
 137  * We can handle up to 256 different LockTagTypes.
 138  */
 139 typedef enum LockTagType
 140 {
 141         LOCKTAG_RELATION,                       /* whole relation */
 142         LOCKTAG_RELATION_EXTEND,        /* the right to extend a relation */
 143         LOCKTAG_DATABASE_FROZEN_IDS,    /* pg_database.datfrozenxid */
 144         LOCKTAG_PAGE,                           /* one page of a relation */
 145         LOCKTAG_TUPLE,                          /* one physical tuple */
 146         LOCKTAG_TRANSACTION,            /* transaction (for waiting for xact done) */
 147         LOCKTAG_VIRTUALTRANSACTION, /* virtual transaction (ditto) */
 148         LOCKTAG_SPECULATIVE_TOKEN,      /* speculative insertion Xid and token */
 149         LOCKTAG_OBJECT,                         /* non-relation database object */
 150         LOCKTAG_USERLOCK,                       /* reserved for old contrib/userlock code */
 151         LOCKTAG_ADVISORY                        /* advisory user locks */
 152 } LockTagType;
 153
 154 #define LOCKTAG_LAST_TYPE       LOCKTAG_ADVISORY
 155
 156 extern const char *const LockTagTypeNames[];
 157
 158 /*
 159  * The LOCKTAG struct is defined with malice aforethought to fit into 16
 160  * bytes with no padding.  Note that this would need adjustment if we were
 161  * to widen Oid, BlockNumber, or TransactionId to more than 32 bits.
 162  *
 163  * We include lockmethodid in the locktag so that a single hash table in
 164  * shared memory can store locks of different lockmethods.
 165  */
 166 typedef struct LOCKTAG
 167 {
 168         uint32          locktag_field1; /* a 32-bit ID field */
 169         uint32          locktag_field2; /* a 32-bit ID field */
 170         uint32          locktag_field3; /* a 32-bit ID field */
 171         uint16          locktag_field4; /* a 16-bit ID field */
 172         uint8           locktag_type;   /* see enum LockTagType */
 173         uint8           locktag_lockmethodid;   /* lockmethod indicator */
 174 } LOCKTAG;
 175
 176 /*
 177  * These macros define how we map logical IDs of lockable objects into
 178  * the physical fields of LOCKTAG.  Use these to set up LOCKTAG values,
 179  * rather than accessing the fields directly.  Note multiple eval of target!
 180  */
 181
 182 /* ID info for a relation is DB OID + REL OID; DB OID = 0 if shared */
 183 #define SET_LOCKTAG_RELATION(locktag,dboid,reloid) \
 184         ((locktag).locktag_field1 = (dboid), \
 185          (locktag).locktag_field2 = (reloid), \
 186          (locktag).locktag_field3 = 0, \
 187          (locktag).locktag_field4 = 0, \
 188          (locktag).locktag_type = LOCKTAG_RELATION, \
 189          (locktag).locktag_lockmethodid = DEFAULT_LOCKMETHOD)
 190
 191 /* same ID info as RELATION */
 192 #define SET_LOCKTAG_RELATION_EXTEND(locktag,dboid,reloid) \
 193         ((locktag).locktag_field1 = (dboid), \
 194          (locktag).locktag_field2 = (reloid), \
 195          (locktag).locktag_field3 = 0, \
 196          (locktag).locktag_field4 = 0, \
 197          (locktag).locktag_type = LOCKTAG_RELATION_EXTEND, \
 198          (locktag).locktag_lockmethodid = DEFAULT_LOCKMETHOD)
 199
 200 /* ID info for frozen IDs is DB OID */
 201 #define SET_LOCKTAG_DATABASE_FROZEN_IDS(locktag,dboid) \
 202         ((locktag).locktag_field1 = (dboid), \
 203          (locktag).locktag_field2 = 0, \
 204          (locktag).locktag_field3 = 0, \
 205          (locktag).locktag_field4 = 0, \
 206          (locktag).locktag_type = LOCKTAG_DATABASE_FROZEN_IDS, \
 207          (locktag).locktag_lockmethodid = DEFAULT_LOCKMETHOD)
 208
 209 /* ID info for a page is RELATION info + BlockNumber */
 210 #define SET_LOCKTAG_PAGE(locktag,dboid,reloid,blocknum) \
 211         ((locktag).locktag_field1 = (dboid), \
 212          (locktag).locktag_field2 = (reloid), \
 213          (locktag).locktag_field3 = (blocknum), \
 214          (locktag).locktag_field4 = 0, \
 215          (locktag).locktag_type = LOCKTAG_PAGE, \
 216          (locktag).locktag_lockmethodid = DEFAULT_LOCKMETHOD)
 217
 218 /* ID info for a tuple is PAGE info + OffsetNumber */
 219 #define SET_LOCKTAG_TUPLE(locktag,dboid,reloid,blocknum,offnum) \
 220         ((locktag).locktag_field1 = (dboid), \
 221          (locktag).locktag_field2 = (reloid), \
 222          (locktag).locktag_field3 = (blocknum), \
 223          (locktag).locktag_field4 = (offnum), \
 224          (locktag).locktag_type = LOCKTAG_TUPLE, \
 225          (locktag).locktag_lockmethodid = DEFAULT_LOCKMETHOD)
 226
 227 /* ID info for a transaction is its TransactionId */
 228 #define SET_LOCKTAG_TRANSACTION(locktag,xid) \
 229         ((locktag).locktag_field1 = (xid), \
 230          (locktag).locktag_field2 = 0, \
 231          (locktag).locktag_field3 = 0, \
 232          (locktag).locktag_field4 = 0, \
 233          (locktag).locktag_type = LOCKTAG_TRANSACTION, \
 234          (locktag).locktag_lockmethodid = DEFAULT_LOCKMETHOD)
 235
 236 /* ID info for a virtual transaction is its VirtualTransactionId */
 237 #define SET_LOCKTAG_VIRTUALTRANSACTION(locktag,vxid) \
 238         ((locktag).locktag_field1 = (vxid).backendId, \
 239          (locktag).locktag_field2 = (vxid).localTransactionId, \
 240          (locktag).locktag_field3 = 0, \
 241          (locktag).locktag_field4 = 0, \
 242          (locktag).locktag_type = LOCKTAG_VIRTUALTRANSACTION, \
 243          (locktag).locktag_lockmethodid = DEFAULT_LOCKMETHOD)
 244
 245 /*
 246  * ID info for a speculative insert is TRANSACTION info +
 247  * its speculative insert counter.
 248  */
 249 #define SET_LOCKTAG_SPECULATIVE_INSERTION(locktag,xid,token) \
 250         ((locktag).locktag_field1 = (xid), \
 251          (locktag).locktag_field2 = (token),            \
 252          (locktag).locktag_field3 = 0, \
 253          (locktag).locktag_field4 = 0, \
 254          (locktag).locktag_type = LOCKTAG_SPECULATIVE_TOKEN, \
 255          (locktag).locktag_lockmethodid = DEFAULT_LOCKMETHOD)
 256
 257 /*
 258  * ID info for an object is DB OID + CLASS OID + OBJECT OID + SUBID
 259  *
 260  * Note: object ID has same representation as in pg_depend and
 261  * pg_description, but notice that we are constraining SUBID to 16 bits.
 262  * Also, we use DB OID = 0 for shared objects such as tablespaces.
 263  */
 264 #define SET_LOCKTAG_OBJECT(locktag,dboid,classoid,objoid,objsubid) \
 265         ((locktag).locktag_field1 = (dboid), \
 266          (locktag).locktag_field2 = (classoid), \
 267          (locktag).locktag_field3 = (objoid), \
 268          (locktag).locktag_field4 = (objsubid), \
 269          (locktag).locktag_type = LOCKTAG_OBJECT, \
 270          (locktag).locktag_lockmethodid = DEFAULT_LOCKMETHOD)
 271
 272 #define SET_LOCKTAG_ADVISORY(locktag,id1,id2,id3,id4) \
 273         ((locktag).locktag_field1 = (id1), \
 274          (locktag).locktag_field2 = (id2), \
 275          (locktag).locktag_field3 = (id3), \
 276          (locktag).locktag_field4 = (id4), \
 277          (locktag).locktag_type = LOCKTAG_ADVISORY, \
 278          (locktag).locktag_lockmethodid = USER_LOCKMETHOD)
 279
 280
 281 /*
 282  * Per-locked-object lock information:
 283  *
 284  * tag -- uniquely identifies the object being locked
 285  * grantMask -- bitmask for all lock types currently granted on this object.
 286  * waitMask -- bitmask for all lock types currently awaited on this object.
 287  * procLocks -- list of PROCLOCK objects for this lock.
 288  * waitProcs -- queue of processes waiting for this lock.
 289  * requested -- count of each lock type currently requested on the lock
 290  *              (includes requests already granted!!).
 291  * nRequested -- total requested locks of all types.
 292  * granted -- count of each lock type currently granted on the lock.
 293  * nGranted -- total granted locks of all types.
 294  *
 295  * Note: these counts count 1 for each backend.  Internally to a backend,
 296  * there may be multiple grabs on a particular lock, but this is not reflected
 297  * into shared memory.
 298  */
 299 typedef struct LOCK
 300 {
 301         /* hash key */
 302         LOCKTAG         tag;                    /* unique identifier of lockable object */
 303
 304         /* data */
 305         LOCKMASK        grantMask;              /* bitmask for lock types already granted */
 306         LOCKMASK        waitMask;               /* bitmask for lock types awaited */
 307         SHM_QUEUE       procLocks;              /* list of PROCLOCK objects assoc. with lock */
 308         PROC_QUEUE      waitProcs;              /* list of PGPROC objects waiting on lock */
 309         int                     requested[MAX_LOCKMODES];       /* counts of requested locks */
 310         int                     nRequested;             /* total of requested[] array */
 311         int                     granted[MAX_LOCKMODES]; /* counts of granted locks */
 312         int                     nGranted;               /* total of granted[] array */
 313 } LOCK;
 314
 315 #define LOCK_LOCKMETHOD(lock) ((LOCKMETHODID) (lock).tag.locktag_lockmethodid)
 316 #define LOCK_LOCKTAG(lock) ((LockTagType) (lock).tag.locktag_type)
 317
 318
 319 /*
 320  * We may have several different backends holding or awaiting locks
 321  * on the same lockable object.  We need to store some per-holder/waiter
 322  * information for each such holder (or would-be holder).  This is kept in
 323  * a PROCLOCK struct.
 324  *
 325  * PROCLOCKTAG is the key information needed to look up a PROCLOCK item in the
 326  * proclock hashtable.  A PROCLOCKTAG value uniquely identifies the combination
 327  * of a lockable object and a holder/waiter for that object.  (We can use
 328  * pointers here because the PROCLOCKTAG need only be unique for the lifespan
 329  * of the PROCLOCK, and it will never outlive the lock or the proc.)
 330  *
 331  * Internally to a backend, it is possible for the same lock to be held
 332  * for different purposes: the backend tracks transaction locks separately
 333  * from session locks.  However, this is not reflected in the shared-memory
 334  * state: we only track which backend(s) hold the lock.  This is OK since a
 335  * backend can never block itself.
 336  *
 337  * The holdMask field shows the already-granted locks represented by this
 338  * proclock.  Note that there will be a proclock object, possibly with
 339  * zero holdMask, for any lock that the process is currently waiting on.
 340  * Otherwise, proclock objects whose holdMasks are zero are recycled
 341  * as soon as convenient.
 342  *
 343  * releaseMask is workspace for LockReleaseAll(): it shows the locks due
 344  * to be released during the current call.  This must only be examined or
 345  * set by the backend owning the PROCLOCK.
 346  *
 347  * Each PROCLOCK object is linked into lists for both the associated LOCK
 348  * object and the owning PGPROC object.  Note that the PROCLOCK is entered
 349  * into these lists as soon as it is created, even if no lock has yet been
 350  * granted.  A PGPROC that is waiting for a lock to be granted will also be
 351  * linked into the lock's waitProcs queue.
 352  */
 353 typedef struct PROCLOCKTAG
 354 {
 355         /* NB: we assume this struct contains no padding! */
 356         LOCK       *myLock;                     /* link to per-lockable-object information */
 357         PGPROC     *myProc;                     /* link to PGPROC of owning backend */
 358 } PROCLOCKTAG;
 359
 360 typedef struct PROCLOCK
 361 {
 362         /* tag */
 363         PROCLOCKTAG tag;                        /* unique identifier of proclock object */
 364
 365         /* data */
 366         PGPROC     *groupLeader;        /* proc's lock group leader, or proc itself */
 367         LOCKMASK        holdMask;               /* bitmask for lock types currently held */
 368         LOCKMASK        releaseMask;    /* bitmask for lock types to be released */
 369         SHM_QUEUE       lockLink;               /* list link in LOCK's list of proclocks */
 370         SHM_QUEUE       procLink;               /* list link in PGPROC's list of proclocks */
 371 } PROCLOCK;
 372
 373 #define PROCLOCK_LOCKMETHOD(proclock) \
 374         LOCK_LOCKMETHOD(*((proclock).tag.myLock))
 375
 376 /*
 377  * Each backend also maintains a local hash table with information about each
 378  * lock it is currently interested in.  In particular the local table counts
 379  * the number of times that lock has been acquired.  This allows multiple
 380  * requests for the same lock to be executed without additional accesses to
 381  * shared memory.  We also track the number of lock acquisitions per
 382  * ResourceOwner, so that we can release just those locks belonging to a
 383  * particular ResourceOwner.
 384  *
 385  * When holding a lock taken "normally", the lock and proclock fields always
 386  * point to the associated objects in shared memory.  However, if we acquired
 387  * the lock via the fast-path mechanism, the lock and proclock fields are set
 388  * to NULL, since there probably aren't any such objects in shared memory.
 389  * (If the lock later gets promoted to normal representation, we may eventually
 390  * update our locallock's lock/proclock fields after finding the shared
 391  * objects.)
 392  *
 393  * Caution: a locallock object can be left over from a failed lock acquisition
 394  * attempt.  In this case its lock/proclock fields are untrustworthy, since
 395  * the shared lock object is neither held nor awaited, and hence is available
 396  * to be reclaimed.  If nLocks > 0 then these pointers must either be valid or
 397  * NULL, but when nLocks == 0 they should be considered garbage.
 398  */
 399 typedef struct LOCALLOCKTAG
 400 {
 401         LOCKTAG         lock;                   /* identifies the lockable object */
 402         LOCKMODE        mode;                   /* lock mode for this table entry */
 403 } LOCALLOCKTAG;
 404
 405 typedef struct LOCALLOCKOWNER
 406 {
 407         /*
 408          * Note: if owner is NULL then the lock is held on behalf of the session;
 409          * otherwise it is held on behalf of my current transaction.
 410          *
 411          * Must use a forward struct reference to avoid circularity.
 412          */
 413         struct ResourceOwnerData *owner;
 414         int64           nLocks;                 /* # of times held by this owner */
 415 } LOCALLOCKOWNER;
 416
 417 typedef struct LOCALLOCK
 418 {
 419         /* tag */
 420         LOCALLOCKTAG tag;                       /* unique identifier of locallock entry */
 421
 422         /* data */
 423         uint32          hashcode;               /* copy of LOCKTAG's hash value */
 424         LOCK       *lock;                       /* associated LOCK object, if any */
 425         PROCLOCK   *proclock;           /* associated PROCLOCK object, if any */
 426         int64           nLocks;                 /* total number of times lock is held */
 427         int                     numLockOwners;  /* # of relevant ResourceOwners */
 428         int                     maxLockOwners;  /* allocated size of array */
 429         LOCALLOCKOWNER *lockOwners; /* dynamically resizable array */
 430         bool            holdsStrongLockCount;   /* bumped FastPathStrongRelationLocks */
 431         bool            lockCleared;    /* we read all sinval msgs for lock */
 432 } LOCALLOCK;
 433
 434 #define LOCALLOCK_LOCKMETHOD(llock) ((llock).tag.lock.locktag_lockmethodid)
 435 #define LOCALLOCK_LOCKTAG(llock) ((LockTagType) (llock).tag.lock.locktag_type)
 436
 437
 438 /*
 439  * These structures hold information passed from lmgr internals to the lock
 440  * listing user-level functions (in lockfuncs.c).
 441  */
 442
 443 typedef struct LockInstanceData
 444 {
 445         LOCKTAG         locktag;                /* tag for locked object */
 446         LOCKMASK        holdMask;               /* locks held by this PGPROC */
 447         LOCKMODE        waitLockMode;   /* lock awaited by this PGPROC, if any */
 448         BackendId       backend;                /* backend ID of this PGPROC */
 449         LocalTransactionId lxid;        /* local transaction ID of this PGPROC */
 450         TimestampTz waitStart;          /* time at which this PGPROC started waiting
 451                                                                  * for lock */
 452         int                     pid;                    /* pid of this PGPROC */
 453         int                     leaderPid;              /* pid of group leader; = pid if no group */
 454         bool            fastpath;               /* taken via fastpath? */
 455 } LockInstanceData;
 456
 457 typedef struct LockData
 458 {
 459         int                     nelements;              /* The length of the array */
 460         LockInstanceData *locks;        /* Array of per-PROCLOCK information */
 461 } LockData;
 462
 463 typedef struct BlockedProcData
 464 {
 465         int                     pid;                    /* pid of a blocked PGPROC */
 466         /* Per-PROCLOCK information about PROCLOCKs of the lock the pid awaits */
 467         /* (these fields refer to indexes in BlockedProcsData.locks[]) */
 468         int                     first_lock;             /* index of first relevant LockInstanceData */
 469         int                     num_locks;              /* number of relevant LockInstanceDatas */
 470         /* PIDs of PGPROCs that are ahead of "pid" in the lock's wait queue */
 471         /* (these fields refer to indexes in BlockedProcsData.waiter_pids[]) */
 472         int                     first_waiter;   /* index of first preceding waiter */
 473         int                     num_waiters;    /* number of preceding waiters */
 474 } BlockedProcData;
 475
 476 typedef struct BlockedProcsData
 477 {
 478         BlockedProcData *procs;         /* Array of per-blocked-proc information */
 479         LockInstanceData *locks;        /* Array of per-PROCLOCK information */
 480         int                *waiter_pids;        /* Array of PIDs of other blocked PGPROCs */
 481         int                     nprocs;                 /* # of valid entries in procs[] array */
 482         int                     maxprocs;               /* Allocated length of procs[] array */
 483         int                     nlocks;                 /* # of valid entries in locks[] array */
 484         int                     maxlocks;               /* Allocated length of locks[] array */
 485         int                     npids;                  /* # of valid entries in waiter_pids[] array */
 486         int                     maxpids;                /* Allocated length of waiter_pids[] array */
 487 } BlockedProcsData;
 488
 489
 490 /* Result codes for LockAcquire() */
 491 typedef enum
 492 {
 493         LOCKACQUIRE_NOT_AVAIL,          /* lock not available, and dontWait=true */
 494         LOCKACQUIRE_OK,                         /* lock successfully acquired */
 495         LOCKACQUIRE_ALREADY_HELD,       /* incremented count for lock already held */
 496         LOCKACQUIRE_ALREADY_CLEAR       /* incremented count for lock already clear */
 497 } LockAcquireResult;
 498
 499 /* Deadlock states identified by DeadLockCheck() */
 500 typedef enum
 501 {
 502         DS_NOT_YET_CHECKED,                     /* no deadlock check has run yet */
 503         DS_NO_DEADLOCK,                         /* no deadlock detected */
 504         DS_SOFT_DEADLOCK,                       /* deadlock avoided by queue rearrangement */
 505         DS_HARD_DEADLOCK,                       /* deadlock, no way out but ERROR */
 506         DS_BLOCKED_BY_AUTOVACUUM        /* no deadlock; queue blocked by autovacuum
 507                                                                  * worker */
 508 } DeadLockState;
 509
 510 /*
 511  * The lockmgr's shared hash tables are partitioned to reduce contention.
 512  * To determine which partition a given locktag belongs to, compute the tag's
 513  * hash code with LockTagHashCode(), then apply one of these macros.
 514  * NB: NUM_LOCK_PARTITIONS must be a power of 2!
 515  */
 516 #define LockHashPartition(hashcode) \
 517         ((hashcode) % NUM_LOCK_PARTITIONS)
 518 #define LockHashPartitionLock(hashcode) \
 519         (&MainLWLockArray[LOCK_MANAGER_LWLOCK_OFFSET + \
 520                 LockHashPartition(hashcode)].lock)
 521 #define LockHashPartitionLockByIndex(i) \
 522         (&MainLWLockArray[LOCK_MANAGER_LWLOCK_OFFSET + (i)].lock)
 523
 524 /*
 525  * The deadlock detector needs to be able to access lockGroupLeader and
 526  * related fields in the PGPROC, so we arrange for those fields to be protected
 527  * by one of the lock hash partition locks.  Since the deadlock detector
 528  * acquires all such locks anyway, this makes it safe for it to access these
 529  * fields without doing anything extra.  To avoid contention as much as
 530  * possible, we map different PGPROCs to different partition locks.  The lock
 531  * used for a given lock group is determined by the group leader's pgprocno.
 532  */
 533 #define LockHashPartitionLockByProc(leader_pgproc) \
 534         LockHashPartitionLock((leader_pgproc)->pgprocno)
 535
 536 /*
 537  * function prototypes
 538  */
 539 extern void InitLocks(void);
 540 extern LockMethod GetLocksMethodTable(const LOCK *lock);
 541 extern LockMethod GetLockTagsMethodTable(const LOCKTAG *locktag);
 542 extern uint32 LockTagHashCode(const LOCKTAG *locktag);
 543 extern bool DoLockModesConflict(LOCKMODE mode1, LOCKMODE mode2);
 544 extern LockAcquireResult LockAcquire(const LOCKTAG *locktag,
 545                                                                          LOCKMODE lockmode,
 546                                                                          bool sessionLock,
 547                                                                          bool dontWait);
 548 extern LockAcquireResult LockAcquireExtended(const LOCKTAG *locktag,
 549                                                                                          LOCKMODE lockmode,
 550                                                                                          bool sessionLock,
 551                                                                                          bool dontWait,
 552                                                                                          bool reportMemoryError,
 553                                                                                          LOCALLOCK **locallockp);
 554 extern void AbortStrongLockAcquire(void);
 555 extern void MarkLockClear(LOCALLOCK *locallock);
 556 extern bool LockRelease(const LOCKTAG *locktag,
 557                                                 LOCKMODE lockmode, bool sessionLock);
 558 extern void LockReleaseAll(LOCKMETHODID lockmethodid, bool allLocks);
 559 extern void LockReleaseSession(LOCKMETHODID lockmethodid);
 560 extern void LockReleaseCurrentOwner(LOCALLOCK **locallocks, int nlocks);
 561 extern void LockReassignCurrentOwner(LOCALLOCK **locallocks, int nlocks);
 562 extern bool LockHeldByMe(const LOCKTAG *locktag, LOCKMODE lockmode);
 563 #ifdef USE_ASSERT_CHECKING
 564 extern HTAB *GetLockMethodLocalHash(void);
 565 #endif
 566 extern bool LockHasWaiters(const LOCKTAG *locktag,
 567                                                    LOCKMODE lockmode, bool sessionLock);
 568 extern VirtualTransactionId *GetLockConflicts(const LOCKTAG *locktag,
 569                                                                                           LOCKMODE lockmode, int *countp);
 570 extern void AtPrepare_Locks(void);
 571 extern void PostPrepare_Locks(TransactionId xid);
 572 extern bool LockCheckConflicts(LockMethod lockMethodTable,
 573                                                            LOCKMODE lockmode,
 574                                                            LOCK *lock, PROCLOCK *proclock);
 575 extern void GrantLock(LOCK *lock, PROCLOCK *proclock, LOCKMODE lockmode);
 576 extern void GrantAwaitedLock(void);
 577 extern void RemoveFromWaitQueue(PGPROC *proc, uint32 hashcode);
 578 extern Size LockShmemSize(void);
 579 extern LockData *GetLockStatusData(void);
 580 extern BlockedProcsData *GetBlockerStatusData(int blocked_pid);
 581
 582 extern xl_standby_lock *GetRunningTransactionLocks(int *nlocks);
 583 extern const char *GetLockmodeName(LOCKMETHODID lockmethodid, LOCKMODE mode);
 584
 585 extern void lock_twophase_recover(TransactionId xid, uint16 info,
 586                                                                   void *recdata, uint32 len);
 587 extern void lock_twophase_postcommit(TransactionId xid, uint16 info,
 588                                                                          void *recdata, uint32 len);
 589 extern void lock_twophase_postabort(TransactionId xid, uint16 info,
 590                                                                         void *recdata, uint32 len);
 591 extern void lock_twophase_standby_recover(TransactionId xid, uint16 info,
 592                                                                                   void *recdata, uint32 len);
 593
 594 extern DeadLockState DeadLockCheck(PGPROC *proc);
 595 extern PGPROC *GetBlockingAutoVacuumPgproc(void);
 596 extern void DeadLockReport(void) pg_attribute_noreturn();
 597 extern void RememberSimpleDeadLock(PGPROC *proc1,
 598                                                                    LOCKMODE lockmode,
 599                                                                    LOCK *lock,
 600                                                                    PGPROC *proc2);
 601 extern void InitDeadLockChecking(void);
 602
 603 extern int      LockWaiterCount(const LOCKTAG *locktag);
 604
 605 #ifdef LOCK_DEBUG
 606 extern void DumpLocks(PGPROC *proc);
 607 extern void DumpAllLocks(void);
 608 #endif
 609
 610 /* Lock a VXID (used to wait for a transaction to finish) */
 611 extern void VirtualXactLockTableInsert(VirtualTransactionId vxid);
 612 extern void VirtualXactLockTableCleanup(void);
 613 extern bool VirtualXactLock(VirtualTransactionId vxid, bool wait);
 614
 615 #endif                                                  /* LOCK_H_ */