PostgreSQL Source Code  git master
lwlock.h File Reference
#include "storage/proclist_types.h"
#include "storage/s_lock.h"
#include "port/atomics.h"
#include "storage/lwlocknames.h"
Include dependency graph for lwlock.h:
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Data Structures

struct  LWLock
 
union  LWLockPadded
 
union  LWLockMinimallyPadded
 
struct  NamedLWLockTranche
 

Macros

#define LWLOCK_PADDED_SIZE   PG_CACHE_LINE_SIZE
 
#define LWLOCK_MINIMAL_SIZE   (sizeof(LWLock) <= 32 ? 32 : 64)
 
#define NUM_BUFFER_PARTITIONS   128
 
#define LOG2_NUM_LOCK_PARTITIONS   4
 
#define NUM_LOCK_PARTITIONS   (1 << LOG2_NUM_LOCK_PARTITIONS)
 
#define LOG2_NUM_PREDICATELOCK_PARTITIONS   4
 
#define NUM_PREDICATELOCK_PARTITIONS   (1 << LOG2_NUM_PREDICATELOCK_PARTITIONS)
 
#define BUFFER_MAPPING_LWLOCK_OFFSET   NUM_INDIVIDUAL_LWLOCKS
 
#define LOCK_MANAGER_LWLOCK_OFFSET   (BUFFER_MAPPING_LWLOCK_OFFSET + NUM_BUFFER_PARTITIONS)
 
#define PREDICATELOCK_MANAGER_LWLOCK_OFFSET   (LOCK_MANAGER_LWLOCK_OFFSET + NUM_LOCK_PARTITIONS)
 
#define NUM_FIXED_LWLOCKS   (PREDICATELOCK_MANAGER_LWLOCK_OFFSET + NUM_PREDICATELOCK_PARTITIONS)
 

Typedefs

typedef struct LWLock LWLock
 
typedef union LWLockPadded LWLockPadded
 
typedef union LWLockMinimallyPadded LWLockMinimallyPadded
 
typedef struct NamedLWLockTranche NamedLWLockTranche
 
typedef enum LWLockMode LWLockMode
 
typedef enum BuiltinTrancheIds BuiltinTrancheIds
 
typedef LWLockLWLockId
 

Enumerations

enum  LWLockMode { LW_EXCLUSIVE, LW_SHARED, LW_WAIT_UNTIL_FREE }
 
enum  BuiltinTrancheIds {
  LWTRANCHE_CLOG_BUFFERS = NUM_INDIVIDUAL_LWLOCKS, LWTRANCHE_COMMITTS_BUFFERS, LWTRANCHE_SUBTRANS_BUFFERS, LWTRANCHE_MXACTOFFSET_BUFFERS,
  LWTRANCHE_MXACTMEMBER_BUFFERS, LWTRANCHE_ASYNC_BUFFERS, LWTRANCHE_OLDSERXID_BUFFERS, LWTRANCHE_WAL_INSERT,
  LWTRANCHE_BUFFER_CONTENT, LWTRANCHE_BUFFER_IO_IN_PROGRESS, LWTRANCHE_REPLICATION_ORIGIN, LWTRANCHE_REPLICATION_SLOT_IO_IN_PROGRESS,
  LWTRANCHE_PROC, LWTRANCHE_BUFFER_MAPPING, LWTRANCHE_LOCK_MANAGER, LWTRANCHE_PREDICATE_LOCK_MANAGER,
  LWTRANCHE_PARALLEL_HASH_JOIN, LWTRANCHE_PARALLEL_QUERY_DSA, LWTRANCHE_SESSION_DSA, LWTRANCHE_SESSION_RECORD_TABLE,
  LWTRANCHE_SESSION_TYPMOD_TABLE, LWTRANCHE_SHARED_TUPLESTORE, LWTRANCHE_TBM, LWTRANCHE_PARALLEL_APPEND,
  LWTRANCHE_FIRST_USER_DEFINED
}
 

Functions

bool LWLockAcquire (LWLock *lock, LWLockMode mode)
 
bool LWLockConditionalAcquire (LWLock *lock, LWLockMode mode)
 
bool LWLockAcquireOrWait (LWLock *lock, LWLockMode mode)
 
void LWLockRelease (LWLock *lock)
 
void LWLockReleaseClearVar (LWLock *lock, uint64 *valptr, uint64 val)
 
void LWLockReleaseAll (void)
 
bool LWLockHeldByMe (LWLock *lock)
 
bool LWLockHeldByMeInMode (LWLock *lock, LWLockMode mode)
 
bool LWLockWaitForVar (LWLock *lock, uint64 *valptr, uint64 oldval, uint64 *newval)
 
void LWLockUpdateVar (LWLock *lock, uint64 *valptr, uint64 value)
 
Size LWLockShmemSize (void)
 
void CreateLWLocks (void)
 
void InitLWLockAccess (void)
 
const char * GetLWLockIdentifier (uint32 classId, uint16 eventId)
 
void RequestNamedLWLockTranche (const char *tranche_name, int num_lwlocks)
 
LWLockPaddedGetNamedLWLockTranche (const char *tranche_name)
 
int LWLockNewTrancheId (void)
 
void LWLockRegisterTranche (int tranche_id, const char *tranche_name)
 
void LWLockInitialize (LWLock *lock, int tranche_id)
 

Variables

PGDLLIMPORT LWLockPaddedMainLWLockArray
 
char * MainLWLockNames []
 
PGDLLIMPORT NamedLWLockTrancheNamedLWLockTrancheArray
 
PGDLLIMPORT int NamedLWLockTrancheRequests
 

Macro Definition Documentation

◆ BUFFER_MAPPING_LWLOCK_OFFSET

#define BUFFER_MAPPING_LWLOCK_OFFSET   NUM_INDIVIDUAL_LWLOCKS

Definition at line 124 of file lwlock.h.

◆ LOCK_MANAGER_LWLOCK_OFFSET

#define LOCK_MANAGER_LWLOCK_OFFSET   (BUFFER_MAPPING_LWLOCK_OFFSET + NUM_BUFFER_PARTITIONS)

Definition at line 125 of file lwlock.h.

◆ LOG2_NUM_LOCK_PARTITIONS

#define LOG2_NUM_LOCK_PARTITIONS   4

Definition at line 116 of file lwlock.h.

Referenced by proclock_hash(), and ProcLockHashCode().

◆ LOG2_NUM_PREDICATELOCK_PARTITIONS

#define LOG2_NUM_PREDICATELOCK_PARTITIONS   4

Definition at line 120 of file lwlock.h.

◆ LWLOCK_MINIMAL_SIZE

#define LWLOCK_MINIMAL_SIZE   (sizeof(LWLock) <= 32 ? 32 : 64)

Definition at line 74 of file lwlock.h.

Referenced by CreateLWLocks().

◆ LWLOCK_PADDED_SIZE

#define LWLOCK_PADDED_SIZE   PG_CACHE_LINE_SIZE

Definition at line 73 of file lwlock.h.

Referenced by CreateLWLocks(), and LWLockShmemSize().

◆ NUM_BUFFER_PARTITIONS

#define NUM_BUFFER_PARTITIONS   128

Definition at line 113 of file lwlock.h.

Referenced by InitBufTable(), InitializeLWLocks(), StrategyInitialize(), and StrategyShmemSize().

◆ NUM_FIXED_LWLOCKS

Definition at line 129 of file lwlock.h.

Referenced by GetNamedLWLockTranche(), InitializeLWLocks(), and LWLockShmemSize().

◆ NUM_LOCK_PARTITIONS

◆ NUM_PREDICATELOCK_PARTITIONS

◆ PREDICATELOCK_MANAGER_LWLOCK_OFFSET

#define PREDICATELOCK_MANAGER_LWLOCK_OFFSET   (LOCK_MANAGER_LWLOCK_OFFSET + NUM_LOCK_PARTITIONS)

Definition at line 127 of file lwlock.h.

Typedef Documentation

◆ BuiltinTrancheIds

◆ LWLock

◆ LWLockId

Definition at line 230 of file lwlock.h.

◆ LWLockMinimallyPadded

◆ LWLockMode

◆ LWLockPadded

◆ NamedLWLockTranche

Enumeration Type Documentation

◆ BuiltinTrancheIds

Enumerator
LWTRANCHE_CLOG_BUFFERS 
LWTRANCHE_COMMITTS_BUFFERS 
LWTRANCHE_SUBTRANS_BUFFERS 
LWTRANCHE_MXACTOFFSET_BUFFERS 
LWTRANCHE_MXACTMEMBER_BUFFERS 
LWTRANCHE_ASYNC_BUFFERS 
LWTRANCHE_OLDSERXID_BUFFERS 
LWTRANCHE_WAL_INSERT 
LWTRANCHE_BUFFER_CONTENT 
LWTRANCHE_BUFFER_IO_IN_PROGRESS 
LWTRANCHE_REPLICATION_ORIGIN 
LWTRANCHE_REPLICATION_SLOT_IO_IN_PROGRESS 
LWTRANCHE_PROC 
LWTRANCHE_BUFFER_MAPPING 
LWTRANCHE_LOCK_MANAGER 
LWTRANCHE_PREDICATE_LOCK_MANAGER 
LWTRANCHE_PARALLEL_HASH_JOIN 
LWTRANCHE_PARALLEL_QUERY_DSA 
LWTRANCHE_SESSION_DSA 
LWTRANCHE_SESSION_RECORD_TABLE 
LWTRANCHE_SESSION_TYPMOD_TABLE 
LWTRANCHE_SHARED_TUPLESTORE 
LWTRANCHE_TBM 
LWTRANCHE_PARALLEL_APPEND 
LWTRANCHE_FIRST_USER_DEFINED 

Definition at line 196 of file lwlock.h.

197 {
198  LWTRANCHE_CLOG_BUFFERS = NUM_INDIVIDUAL_LWLOCKS,
BuiltinTrancheIds
Definition: lwlock.h:196

◆ LWLockMode

enum LWLockMode
Enumerator
LW_EXCLUSIVE 
LW_SHARED 
LW_WAIT_UNTIL_FREE 

Definition at line 132 of file lwlock.h.

133 {
134  LW_EXCLUSIVE,
135  LW_SHARED,
136  LW_WAIT_UNTIL_FREE /* A special mode used in PGPROC->lwlockMode,
137  * when waiting for lock to become free. Not
138  * to be used as LWLockAcquire argument */
139 } LWLockMode;
LWLockMode
Definition: lwlock.h:132

Function Documentation

◆ CreateLWLocks()

void CreateLWLocks ( void  )

Definition at line 381 of file lwlock.c.

References InitializeLWLocks(), IsUnderPostmaster, LW_VAL_EXCLUSIVE, LWLOCK_MINIMAL_SIZE, LWLOCK_PADDED_SIZE, LWLockShmemSize(), LWTRANCHE_FIRST_USER_DEFINED, MAX_BACKENDS, RegisterLWLockTranches(), ShmemAlloc(), and StaticAssertExpr.

Referenced by CreateSharedMemoryAndSemaphores().

382 {
384  "MAX_BACKENDS too big for lwlock.c");
385 
387  sizeof(LWLock) <= LWLOCK_PADDED_SIZE,
388  "Miscalculated LWLock padding");
389 
390  if (!IsUnderPostmaster)
391  {
392  Size spaceLocks = LWLockShmemSize();
393  int *LWLockCounter;
394  char *ptr;
395 
396  /* Allocate space */
397  ptr = (char *) ShmemAlloc(spaceLocks);
398 
399  /* Leave room for dynamic allocation of tranches */
400  ptr += sizeof(int);
401 
402  /* Ensure desired alignment of LWLock array */
403  ptr += LWLOCK_PADDED_SIZE - ((uintptr_t) ptr) % LWLOCK_PADDED_SIZE;
404 
405  MainLWLockArray = (LWLockPadded *) ptr;
406 
407  /*
408  * Initialize the dynamic-allocation counter for tranches, which is
409  * stored just before the first LWLock.
410  */
411  LWLockCounter = (int *) ((char *) MainLWLockArray - sizeof(int));
412  *LWLockCounter = LWTRANCHE_FIRST_USER_DEFINED;
413 
414  /* Initialize all LWLocks */
416  }
417 
418  /* Register all LWLock tranches */
420 }
Definition: lwlock.h:32
void * ShmemAlloc(Size size)
Definition: shmem.c:157
Size LWLockShmemSize(void)
Definition: lwlock.c:349
static void RegisterLWLockTranches(void)
Definition: lwlock.c:491
#define LWLOCK_MINIMAL_SIZE
Definition: lwlock.h:74
#define MAX_BACKENDS
Definition: postmaster.h:75
bool IsUnderPostmaster
Definition: globals.c:101
unsigned int uint32
Definition: c.h:306
static void InitializeLWLocks(void)
Definition: lwlock.c:426
#define StaticAssertExpr(condition, errmessage)
Definition: c.h:766
size_t Size
Definition: c.h:414
#define LW_VAL_EXCLUSIVE
Definition: lwlock.c:103
#define LWLOCK_PADDED_SIZE
Definition: lwlock.h:73
LWLockPadded * MainLWLockArray
Definition: lwlock.c:125

◆ GetLWLockIdentifier()

const char* GetLWLockIdentifier ( uint32  classId,
uint16  eventId 
)

Definition at line 712 of file lwlock.c.

References Assert, LWLockTrancheArray, LWLockTranchesAllocated, and PG_WAIT_LWLOCK.

Referenced by pgstat_get_wait_event().

713 {
714  Assert(classId == PG_WAIT_LWLOCK);
715 
716  /*
717  * It is quite possible that user has registered tranche in one of the
718  * backends (e.g. by allocating lwlocks in dynamic shared memory) but not
719  * all of them, so we can't assume the tranche is registered here.
720  */
721  if (eventId >= LWLockTranchesAllocated ||
722  LWLockTrancheArray[eventId] == NULL)
723  return "extension";
724 
725  return LWLockTrancheArray[eventId];
726 }
static int LWLockTranchesAllocated
Definition: lwlock.c:115
static const char ** LWLockTrancheArray
Definition: lwlock.c:114
#define Assert(condition)
Definition: c.h:680
#define PG_WAIT_LWLOCK
Definition: pgstat.h:737

◆ GetNamedLWLockTranche()

LWLockPadded* GetNamedLWLockTranche ( const char *  tranche_name)

Definition at line 550 of file lwlock.c.

References elog, ERROR, i, NamedLWLockTrancheRequests, NUM_FIXED_LWLOCKS, and NamedLWLockTrancheRequest::num_lwlocks.

Referenced by pgss_shmem_startup().

551 {
552  int lock_pos;
553  int i;
554 
555  /*
556  * Obtain the position of base address of LWLock belonging to requested
557  * tranche_name in MainLWLockArray. LWLocks for named tranches are placed
558  * in MainLWLockArray after fixed locks.
559  */
560  lock_pos = NUM_FIXED_LWLOCKS;
561  for (i = 0; i < NamedLWLockTrancheRequests; i++)
562  {
563  if (strcmp(NamedLWLockTrancheRequestArray[i].tranche_name,
564  tranche_name) == 0)
565  return &MainLWLockArray[lock_pos];
566 
568  }
569 
570  if (i >= NamedLWLockTrancheRequests)
571  elog(ERROR, "requested tranche is not registered");
572 
573  /* just to keep compiler quiet */
574  return NULL;
575 }
#define NUM_FIXED_LWLOCKS
Definition: lwlock.h:129
#define ERROR
Definition: elog.h:43
int NamedLWLockTrancheRequests
Definition: lwlock.c:154
NamedLWLockTrancheRequest * NamedLWLockTrancheRequestArray
Definition: lwlock.c:152
int i
#define elog
Definition: elog.h:219
LWLockPadded * MainLWLockArray
Definition: lwlock.c:125

◆ InitLWLockAccess()

void InitLWLockAccess ( void  )

Definition at line 534 of file lwlock.c.

Referenced by InitProcess().

535 {
536 #ifdef LWLOCK_STATS
537  init_lwlock_stats();
538 #endif
539 }

◆ LWLockAcquire()

bool LWLockAcquire ( LWLock lock,
LWLockMode  mode 
)

Definition at line 1120 of file lwlock.c.

References Assert, AssertArg, elog, ERROR, HOLD_INTERRUPTS, IsUnderPostmaster, LWLockHandle::lock, LOG_LWDEBUG, LW_EXCLUSIVE, LW_FLAG_RELEASE_OK, LW_SHARED, LWLockAttemptLock(), LWLockDequeueSelf(), LWLockQueueSelf(), LWLockReportWaitEnd(), LWLockReportWaitStart(), PGPROC::lwWaiting, MAX_BACKENDS, MAX_SIMUL_LWLOCKS, LWLockHandle::mode, MyProc, num_held_lwlocks, pg_atomic_fetch_or_u32(), pg_atomic_fetch_sub_u32(), PG_USED_FOR_ASSERTS_ONLY, PGSemaphoreLock(), PGSemaphoreUnlock(), PRINT_LWDEBUG, PGPROC::sem, LWLock::state, and T_NAME.

Referenced by _bt_end_vacuum(), _bt_start_vacuum(), _bt_vacuum_cycleid(), AbortBufferIO(), AbsorbFsyncRequests(), ActivateCommitTs(), AdvanceOldestClogXid(), AdvanceOldestCommitTsXid(), AdvanceXLInsertBuffer(), alloc_object(), AlterSystemSetConfigFile(), analyze_rel(), ApplyLauncherMain(), apw_detach_shmem(), apw_dump_now(), apw_init_shmem(), apw_load_buffers(), asyncQueueAddEntries(), asyncQueueAdvanceTail(), asyncQueueReadAllNotifications(), asyncQueueUnregister(), AsyncShmemInit(), AtAbort_Twophase(), AtPrepare_PredicateLocks(), attach_internal(), autoprewarm_main(), autoprewarm_start_worker(), AutoVacLauncherMain(), AutoVacuumRequestWork(), AutoVacWorkerMain(), BackendIdGetProc(), BackendIdGetTransactionIds(), BackendPidGetProc(), BackendXidGetPid(), BecomeLockGroupLeader(), BecomeLockGroupMember(), BootStrapCLOG(), BootStrapMultiXact(), BootStrapSUBTRANS(), BufferAlloc(), CancelDBBackends(), CancelVirtualTransaction(), check_for_freed_segments(), CheckDeadLock(), CheckForSerializableConflictOut(), CheckPointPredicate(), CheckPointRelationMap(), CheckPointReplicationOrigin(), CheckPointReplicationSlots(), CheckPointTwoPhase(), CheckRecoveryConsistency(), CheckTableForSerializableConflictIn(), CheckTargetForConflictsIn(), choose_next_subplan_for_leader(), choose_next_subplan_for_worker(), CleanupInvalidationState(), ClearOldPredicateLocks(), clog_redo(), commit_ts_redo(), CountDBBackends(), CountDBConnections(), CountOtherDBBackends(), CountUserBackends(), CreateCheckPoint(), CreateEndOfRecoveryRecord(), CreateInitDecodingContext(), CreatePredicateLock(), CreateRestartPoint(), DeactivateCommitTs(), DeleteChildTargetLocks(), DeleteLockTarget(), destroy_superblock(), do_autovacuum(), do_pg_start_backup(), do_pg_stop_backup(), do_start_worker(), DropAllPredicateLocksFromTable(), DropSubscription(), DropTableSpace(), dsa_allocate_extended(), dsa_dump(), dsa_free(), dsa_pin(), dsa_release_in_place(), dsa_set_size_limit(), dsa_trim(), dsa_unpin(), dshash_delete_key(), dshash_dump(), dshash_find(), dshash_find_or_insert(), dsm_attach(), dsm_create(), dsm_detach(), dsm_pin_segment(), dsm_unpin_segment(), ensure_active_superblock(), entry_reset(), Exec_ListenPreCommit(), ExecParallelHashMergeCounters(), ExecParallelHashPopChunkQueue(), ExecParallelHashTupleAlloc(), ExecParallelHashTuplePrealloc(), ExpireAllKnownAssignedTransactionIds(), ExpireOldKnownAssignedTransactionIds(), ExpireTreeKnownAssignedTransactionIds(), ExtendCLOG(), ExtendCommitTs(), ExtendMultiXactMember(), ExtendMultiXactOffset(), ExtendSUBTRANS(), FastPathGetRelationLockEntry(), FastPathTransferRelationLocks(), FinishPreparedTransaction(), FlushDatabaseBuffers(), FlushRelationBuffers(), ForceTransactionIdLimitUpdate(), ForwardFsyncRequest(), FreeWorkerInfo(), GetBackgroundWorkerPid(), GetBackgroundWorkerTypeByPid(), GetBlockerStatusData(), GetConflictingVirtualXIDs(), GetCurrentVirtualXIDs(), GetLastImportantRecPtr(), GetLastSegSwitchData(), GetLatestCommitTsData(), GetLockConflicts(), GetLockStatusData(), GetMultiXactIdMembers(), GetNewMultiXactId(), GetNewObjectId(), GetNewTransactionId(), GetOldestActiveTransactionId(), GetOldestMultiXactId(), GetOldestRestartPoint(), GetOldestSafeDecodingTransactionId(), GetOldestXmin(), GetPredicateLockStatusData(), GetPreparedTransactionList(), GetRunningTransactionData(), GetRunningTransactionLocks(), GetSafeSnapshot(), GetSafeSnapshotBlockingPids(), GetSerializableTransactionSnapshotInt(), GetSnapshotData(), GetVirtualXIDsDelayingChkpt(), HaveVirtualXIDsDelayingChkpt(), InstallXLogFileSegment(), InvalidateBuffer(), KnownAssignedXidsAdd(), KnownAssignedXidsReset(), lock_twophase_recover(), LockAcquireExtended(), LockBuffer(), LockErrorCleanup(), LockGXact(), LockHasWaiters(), LockRefindAndRelease(), LockRelease(), LockReleaseAll(), LockWaiterCount(), logicalrep_worker_attach(), logicalrep_worker_detach(), logicalrep_worker_launch(), logicalrep_worker_stop(), logicalrep_worker_wakeup(), MaintainOldSnapshotTimeMapping(), MarkAsPrepared(), MarkAsPreparing(), MaybeExtendOffsetSlru(), multixact_redo(), MultiXactAdvanceNextMXact(), MultiXactGetCheckptMulti(), MultiXactIdSetOldestMember(), MultiXactIdSetOldestVisible(), MultiXactSetNextMXact(), OldSerXidAdd(), OldSerXidGetMinConflictCommitSeqNo(), OldSerXidSetActiveSerXmin(), PageIsPredicateLocked(), perform_relmap_update(), pg_backend_random(), pg_get_replication_slots(), pg_notification_queue_usage(), pg_show_replication_origin_status(), pg_stat_get_subscription(), pg_stat_get_wal_senders(), pg_stat_statements_internal(), pgss_shmem_startup(), pgss_store(), PostPrepare_Locks(), PostPrepare_MultiXact(), PostPrepare_Twophase(), PreCommit_CheckForSerializationFailure(), PreCommit_Notify(), predicatelock_twophase_recover(), PredicateLockPageSplit(), PredicateLockTwoPhaseFinish(), PrefetchBuffer(), PrescanPreparedTransactions(), ProcArrayAdd(), ProcArrayApplyRecoveryInfo(), ProcArrayApplyXidAssignment(), ProcArrayGetReplicationSlotXmin(), ProcArrayGroupClearXid(), ProcArrayInstallImportedXmin(), ProcArrayInstallRestoredXmin(), ProcArrayRemove(), ProcArraySetReplicationSlotXmin(), process_syncing_tables_for_apply(), ProcessTwoPhaseBuffer(), ProcKill(), ProcSleep(), ReadBuffer_common(), ReadMultiXactCounts(), ReadNewTransactionId(), ReadNextMultiXactId(), ReadRecord(), RecordKnownAssignedTransactionIds(), RecordNewMultiXact(), RecoverPreparedTransactions(), RegisterDynamicBackgroundWorker(), RegisterPredicateLockingXid(), RelationCacheInitFilePreInvalidate(), ReleaseOneSerializableXact(), ReleasePredicateLocks(), RemoveScratchTarget(), ReplicationOriginExitCleanup(), ReplicationSlotAcquire(), ReplicationSlotCleanup(), ReplicationSlotCreate(), ReplicationSlotDropPtr(), ReplicationSlotRelease(), ReplicationSlotsComputeLogicalRestartLSN(), ReplicationSlotsComputeRequiredLSN(), ReplicationSlotsComputeRequiredXmin(), ReplicationSlotsCountDBSlots(), ReplicationSlotsDropDBSlots(), replorigin_advance(), replorigin_drop(), replorigin_get_progress(), replorigin_session_advance(), replorigin_session_get_progress(), replorigin_session_reset(), replorigin_session_setup(), resize(), RestoreScratchTarget(), restoreTwoPhaseData(), SaveSlotToPath(), SetCommitTsLimit(), SetMultiXactIdLimit(), SetOffsetVacuumLimit(), SetTransactionIdLimit(), SetXidCommitTsInPage(), SharedInvalBackendInit(), ShmemInitStruct(), SICleanupQueue(), SIGetDataEntries(), SignalBackends(), SIInsertDataEntries(), SimpleLruFlush(), SimpleLruReadPage(), SimpleLruReadPage_ReadOnly(), SimpleLruTruncate(), SimpleLruWaitIO(), SlruDeleteSegment(), SlruInternalWritePage(), SnapBuildInitialSnapshot(), ss_get_location(), StandbyRecoverPreparedTransactions(), StartBufferIO(), StartupCLOG(), StartupDecodingContext(), StartupSUBTRANS(), StartupXLOG(), sts_parallel_scan_next(), SubTransSetParent(), SummarizeOldestCommittedSxact(), SyncOneBuffer(), SyncRepCancelWait(), SyncRepCleanupAtProcExit(), SyncRepInitConfig(), SyncRepReleaseWaiters(), SyncRepUpdateSyncStandbysDefined(), SyncRepWaitForLSN(), TablespaceCreateDbspace(), tbm_shared_iterate(), TerminateBackgroundWorker(), TransactionGroupUpdateXidStatus(), TransactionIdGetCommitTsData(), TransactionIdIsActive(), TransactionIdIsInProgress(), TransactionIdLimitedForOldSnapshots(), TransactionIdSetPageStatus(), TransactionTreeSetCommitTsData(), TransferPredicateLocksToNewTarget(), TrimCLOG(), TrimMultiXact(), TruncateMultiXact(), TwoPhaseGetGXact(), txid_status(), UpdateMinRecoveryPoint(), vacuum_rel(), VirtualXactLock(), VirtualXactLockTableCleanup(), VirtualXactLockTableInsert(), wait_for_relation_state_change(), wait_for_worker_state_change(), WaitForReplicationWorkerAttach(), WaitIO(), WALInsertLockAcquire(), WALInsertLockAcquireExclusive(), write_relcache_init_file(), xact_redo(), xact_redo_abort(), xact_redo_commit(), XidCacheRemoveRunningXids(), xlog_redo(), and XLogBackgroundFlush().

1121 {
1122  PGPROC *proc = MyProc;
1123  bool result = true;
1124  int extraWaits = 0;
1125 #ifdef LWLOCK_STATS
1126  lwlock_stats *lwstats;
1127 
1128  lwstats = get_lwlock_stats_entry(lock);
1129 #endif
1130 
1131  AssertArg(mode == LW_SHARED || mode == LW_EXCLUSIVE);
1132 
1133  PRINT_LWDEBUG("LWLockAcquire", lock, mode);
1134 
1135 #ifdef LWLOCK_STATS
1136  /* Count lock acquisition attempts */
1137  if (mode == LW_EXCLUSIVE)
1138  lwstats->ex_acquire_count++;
1139  else
1140  lwstats->sh_acquire_count++;
1141 #endif /* LWLOCK_STATS */
1142 
1143  /*
1144  * We can't wait if we haven't got a PGPROC. This should only occur
1145  * during bootstrap or shared memory initialization. Put an Assert here
1146  * to catch unsafe coding practices.
1147  */
1148  Assert(!(proc == NULL && IsUnderPostmaster));
1149 
1150  /* Ensure we will have room to remember the lock */
1152  elog(ERROR, "too many LWLocks taken");
1153 
1154  /*
1155  * Lock out cancel/die interrupts until we exit the code section protected
1156  * by the LWLock. This ensures that interrupts will not interfere with
1157  * manipulations of data structures in shared memory.
1158  */
1159  HOLD_INTERRUPTS();
1160 
1161  /*
1162  * Loop here to try to acquire lock after each time we are signaled by
1163  * LWLockRelease.
1164  *
1165  * NOTE: it might seem better to have LWLockRelease actually grant us the
1166  * lock, rather than retrying and possibly having to go back to sleep. But
1167  * in practice that is no good because it means a process swap for every
1168  * lock acquisition when two or more processes are contending for the same
1169  * lock. Since LWLocks are normally used to protect not-very-long
1170  * sections of computation, a process needs to be able to acquire and
1171  * release the same lock many times during a single CPU time slice, even
1172  * in the presence of contention. The efficiency of being able to do that
1173  * outweighs the inefficiency of sometimes wasting a process dispatch
1174  * cycle because the lock is not free when a released waiter finally gets
1175  * to run. See pgsql-hackers archives for 29-Dec-01.
1176  */
1177  for (;;)
1178  {
1179  bool mustwait;
1180 
1181  /*
1182  * Try to grab the lock the first time, we're not in the waitqueue
1183  * yet/anymore.
1184  */
1185  mustwait = LWLockAttemptLock(lock, mode);
1186 
1187  if (!mustwait)
1188  {
1189  LOG_LWDEBUG("LWLockAcquire", lock, "immediately acquired lock");
1190  break; /* got the lock */
1191  }
1192 
1193  /*
1194  * Ok, at this point we couldn't grab the lock on the first try. We
1195  * cannot simply queue ourselves to the end of the list and wait to be
1196  * woken up because by now the lock could long have been released.
1197  * Instead add us to the queue and try to grab the lock again. If we
1198  * succeed we need to revert the queuing and be happy, otherwise we
1199  * recheck the lock. If we still couldn't grab it, we know that the
1200  * other locker will see our queue entries when releasing since they
1201  * existed before we checked for the lock.
1202  */
1203 
1204  /* add to the queue */
1205  LWLockQueueSelf(lock, mode);
1206 
1207  /* we're now guaranteed to be woken up if necessary */
1208  mustwait = LWLockAttemptLock(lock, mode);
1209 
1210  /* ok, grabbed the lock the second time round, need to undo queueing */
1211  if (!mustwait)
1212  {
1213  LOG_LWDEBUG("LWLockAcquire", lock, "acquired, undoing queue");
1214 
1215  LWLockDequeueSelf(lock);
1216  break;
1217  }
1218 
1219  /*
1220  * Wait until awakened.
1221  *
1222  * Since we share the process wait semaphore with the regular lock
1223  * manager and ProcWaitForSignal, and we may need to acquire an LWLock
1224  * while one of those is pending, it is possible that we get awakened
1225  * for a reason other than being signaled by LWLockRelease. If so,
1226  * loop back and wait again. Once we've gotten the LWLock,
1227  * re-increment the sema by the number of additional signals received,
1228  * so that the lock manager or signal manager will see the received
1229  * signal when it next waits.
1230  */
1231  LOG_LWDEBUG("LWLockAcquire", lock, "waiting");
1232 
1233 #ifdef LWLOCK_STATS
1234  lwstats->block_count++;
1235 #endif
1236 
1237  LWLockReportWaitStart(lock);
1238  TRACE_POSTGRESQL_LWLOCK_WAIT_START(T_NAME(lock), mode);
1239 
1240  for (;;)
1241  {
1242  PGSemaphoreLock(proc->sem);
1243  if (!proc->lwWaiting)
1244  break;
1245  extraWaits++;
1246  }
1247 
1248  /* Retrying, allow LWLockRelease to release waiters again. */
1250 
1251 #ifdef LOCK_DEBUG
1252  {
1253  /* not waiting anymore */
1254  uint32 nwaiters PG_USED_FOR_ASSERTS_ONLY = pg_atomic_fetch_sub_u32(&lock->nwaiters, 1);
1255 
1256  Assert(nwaiters < MAX_BACKENDS);
1257  }
1258 #endif
1259 
1260  TRACE_POSTGRESQL_LWLOCK_WAIT_DONE(T_NAME(lock), mode);
1262 
1263  LOG_LWDEBUG("LWLockAcquire", lock, "awakened");
1264 
1265  /* Now loop back and try to acquire lock again. */
1266  result = false;
1267  }
1268 
1269  TRACE_POSTGRESQL_LWLOCK_ACQUIRE(T_NAME(lock), mode);
1270 
1271  /* Add lock to list of locks held by this backend */
1274 
1275  /*
1276  * Fix the process wait semaphore's count for any absorbed wakeups.
1277  */
1278  while (extraWaits-- > 0)
1279  PGSemaphoreUnlock(proc->sem);
1280 
1281  return result;
1282 }
#define T_NAME(lock)
Definition: lwlock.c:117
static uint32 pg_atomic_fetch_sub_u32(volatile pg_atomic_uint32 *ptr, int32 sub_)
Definition: atomics.h:354
static bool LWLockAttemptLock(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:738
void PGSemaphoreUnlock(PGSemaphore sema)
Definition: posix_sema.c:323
PGPROC * MyProc
Definition: proc.c:67
bool lwWaiting
Definition: proc.h:127
#define MAX_SIMUL_LWLOCKS
Definition: lwlock.c:133
pg_atomic_uint32 state
Definition: lwlock.h:35
static LWLockHandle held_lwlocks[MAX_SIMUL_LWLOCKS]
Definition: lwlock.c:143
#define ERROR
Definition: elog.h:43
#define MAX_BACKENDS
Definition: postmaster.h:75
LWLockMode mode
Definition: lwlock.c:139
bool IsUnderPostmaster
Definition: globals.c:101
static void LWLockReportWaitEnd(void)
Definition: lwlock.c:703
unsigned int uint32
Definition: c.h:306
static void LWLockDequeueSelf(LWLock *lock)
Definition: lwlock.c:1025
#define AssertArg(condition)
Definition: c.h:682
static void LWLockReportWaitStart(LWLock *lock)
Definition: lwlock.c:694
static void LWLockQueueSelf(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:981
static int num_held_lwlocks
Definition: lwlock.c:142
#define Assert(condition)
Definition: c.h:680
LWLock * lock
Definition: lwlock.c:138
#define PRINT_LWDEBUG(a, b, c)
Definition: lwlock.c:227
#define LW_FLAG_RELEASE_OK
Definition: lwlock.c:100
void PGSemaphoreLock(PGSemaphore sema)
Definition: posix_sema.c:303
#define HOLD_INTERRUPTS()
Definition: miscadmin.h:115
static uint32 pg_atomic_fetch_or_u32(volatile pg_atomic_uint32 *ptr, uint32 or_)
Definition: atomics.h:383
#define elog
Definition: elog.h:219
PGSemaphore sem
Definition: proc.h:101
#define PG_USED_FOR_ASSERTS_ONLY
Definition: c.h:122
Definition: proc.h:95
#define LOG_LWDEBUG(a, b, c)
Definition: lwlock.c:228

◆ LWLockAcquireOrWait()

bool LWLockAcquireOrWait ( LWLock lock,
LWLockMode  mode 
)

Definition at line 1347 of file lwlock.c.

References Assert, elog, ERROR, HOLD_INTERRUPTS, LWLockHandle::lock, LOG_LWDEBUG, LW_EXCLUSIVE, LW_SHARED, LW_WAIT_UNTIL_FREE, LWLockAttemptLock(), LWLockDequeueSelf(), LWLockQueueSelf(), LWLockReportWaitEnd(), LWLockReportWaitStart(), PGPROC::lwWaiting, MAX_BACKENDS, MAX_SIMUL_LWLOCKS, LWLockHandle::mode, MyProc, num_held_lwlocks, pg_atomic_fetch_sub_u32(), PG_USED_FOR_ASSERTS_ONLY, PGSemaphoreLock(), PGSemaphoreUnlock(), PRINT_LWDEBUG, RESUME_INTERRUPTS, PGPROC::sem, and T_NAME.

Referenced by XLogFlush().

1348 {
1349  PGPROC *proc = MyProc;
1350  bool mustwait;
1351  int extraWaits = 0;
1352 #ifdef LWLOCK_STATS
1353  lwlock_stats *lwstats;
1354 
1355  lwstats = get_lwlock_stats_entry(lock);
1356 #endif
1357 
1358  Assert(mode == LW_SHARED || mode == LW_EXCLUSIVE);
1359 
1360  PRINT_LWDEBUG("LWLockAcquireOrWait", lock, mode);
1361 
1362  /* Ensure we will have room to remember the lock */
1364  elog(ERROR, "too many LWLocks taken");
1365 
1366  /*
1367  * Lock out cancel/die interrupts until we exit the code section protected
1368  * by the LWLock. This ensures that interrupts will not interfere with
1369  * manipulations of data structures in shared memory.
1370  */
1371  HOLD_INTERRUPTS();
1372 
1373  /*
1374  * NB: We're using nearly the same twice-in-a-row lock acquisition
1375  * protocol as LWLockAcquire(). Check its comments for details.
1376  */
1377  mustwait = LWLockAttemptLock(lock, mode);
1378 
1379  if (mustwait)
1380  {
1382 
1383  mustwait = LWLockAttemptLock(lock, mode);
1384 
1385  if (mustwait)
1386  {
1387  /*
1388  * Wait until awakened. Like in LWLockAcquire, be prepared for
1389  * bogus wakeups, because we share the semaphore with
1390  * ProcWaitForSignal.
1391  */
1392  LOG_LWDEBUG("LWLockAcquireOrWait", lock, "waiting");
1393 
1394 #ifdef LWLOCK_STATS
1395  lwstats->block_count++;
1396 #endif
1397 
1398  LWLockReportWaitStart(lock);
1399  TRACE_POSTGRESQL_LWLOCK_WAIT_START(T_NAME(lock), mode);
1400 
1401  for (;;)
1402  {
1403  PGSemaphoreLock(proc->sem);
1404  if (!proc->lwWaiting)
1405  break;
1406  extraWaits++;
1407  }
1408 
1409 #ifdef LOCK_DEBUG
1410  {
1411  /* not waiting anymore */
1412  uint32 nwaiters PG_USED_FOR_ASSERTS_ONLY = pg_atomic_fetch_sub_u32(&lock->nwaiters, 1);
1413 
1414  Assert(nwaiters < MAX_BACKENDS);
1415  }
1416 #endif
1417  TRACE_POSTGRESQL_LWLOCK_WAIT_DONE(T_NAME(lock), mode);
1419 
1420  LOG_LWDEBUG("LWLockAcquireOrWait", lock, "awakened");
1421  }
1422  else
1423  {
1424  LOG_LWDEBUG("LWLockAcquireOrWait", lock, "acquired, undoing queue");
1425 
1426  /*
1427  * Got lock in the second attempt, undo queueing. We need to treat
1428  * this as having successfully acquired the lock, otherwise we'd
1429  * not necessarily wake up people we've prevented from acquiring
1430  * the lock.
1431  */
1432  LWLockDequeueSelf(lock);
1433  }
1434  }
1435 
1436  /*
1437  * Fix the process wait semaphore's count for any absorbed wakeups.
1438  */
1439  while (extraWaits-- > 0)
1440  PGSemaphoreUnlock(proc->sem);
1441 
1442  if (mustwait)
1443  {
1444  /* Failed to get lock, so release interrupt holdoff */
1446  LOG_LWDEBUG("LWLockAcquireOrWait", lock, "failed");
1447  TRACE_POSTGRESQL_LWLOCK_ACQUIRE_OR_WAIT_FAIL(T_NAME(lock), mode);
1448  }
1449  else
1450  {
1451  LOG_LWDEBUG("LWLockAcquireOrWait", lock, "succeeded");
1452  /* Add lock to list of locks held by this backend */
1455  TRACE_POSTGRESQL_LWLOCK_ACQUIRE_OR_WAIT(T_NAME(lock), mode);
1456  }
1457 
1458  return !mustwait;
1459 }
#define T_NAME(lock)
Definition: lwlock.c:117
static uint32 pg_atomic_fetch_sub_u32(volatile pg_atomic_uint32 *ptr, int32 sub_)
Definition: atomics.h:354
static bool LWLockAttemptLock(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:738
void PGSemaphoreUnlock(PGSemaphore sema)
Definition: posix_sema.c:323
PGPROC * MyProc
Definition: proc.c:67
bool lwWaiting
Definition: proc.h:127
#define MAX_SIMUL_LWLOCKS
Definition: lwlock.c:133
#define RESUME_INTERRUPTS()
Definition: miscadmin.h:117
static LWLockHandle held_lwlocks[MAX_SIMUL_LWLOCKS]
Definition: lwlock.c:143
#define ERROR
Definition: elog.h:43
#define MAX_BACKENDS
Definition: postmaster.h:75
LWLockMode mode
Definition: lwlock.c:139
static void LWLockReportWaitEnd(void)
Definition: lwlock.c:703
unsigned int uint32
Definition: c.h:306
static void LWLockDequeueSelf(LWLock *lock)
Definition: lwlock.c:1025
static void LWLockReportWaitStart(LWLock *lock)
Definition: lwlock.c:694
static void LWLockQueueSelf(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:981
static int num_held_lwlocks
Definition: lwlock.c:142
#define Assert(condition)
Definition: c.h:680
LWLock * lock
Definition: lwlock.c:138
#define PRINT_LWDEBUG(a, b, c)
Definition: lwlock.c:227
void PGSemaphoreLock(PGSemaphore sema)
Definition: posix_sema.c:303
#define HOLD_INTERRUPTS()
Definition: miscadmin.h:115
#define elog
Definition: elog.h:219
PGSemaphore sem
Definition: proc.h:101
#define PG_USED_FOR_ASSERTS_ONLY
Definition: c.h:122
Definition: proc.h:95
#define LOG_LWDEBUG(a, b, c)
Definition: lwlock.c:228

◆ LWLockConditionalAcquire()

bool LWLockConditionalAcquire ( LWLock lock,
LWLockMode  mode 
)

Definition at line 1292 of file lwlock.c.

References AssertArg, elog, ERROR, HOLD_INTERRUPTS, LWLockHandle::lock, LOG_LWDEBUG, LW_EXCLUSIVE, LW_SHARED, LWLockAttemptLock(), MAX_SIMUL_LWLOCKS, LWLockHandle::mode, num_held_lwlocks, PRINT_LWDEBUG, RESUME_INTERRUPTS, and T_NAME.

Referenced by BufferAlloc(), ConditionalLockBuffer(), ProcArrayEndTransaction(), SimpleLruWaitIO(), ss_report_location(), TransactionIdSetPageStatus(), and XLogNeedsFlush().

1293 {
1294  bool mustwait;
1295 
1296  AssertArg(mode == LW_SHARED || mode == LW_EXCLUSIVE);
1297 
1298  PRINT_LWDEBUG("LWLockConditionalAcquire", lock, mode);
1299 
1300  /* Ensure we will have room to remember the lock */
1302  elog(ERROR, "too many LWLocks taken");
1303 
1304  /*
1305  * Lock out cancel/die interrupts until we exit the code section protected
1306  * by the LWLock. This ensures that interrupts will not interfere with
1307  * manipulations of data structures in shared memory.
1308  */
1309  HOLD_INTERRUPTS();
1310 
1311  /* Check for the lock */
1312  mustwait = LWLockAttemptLock(lock, mode);
1313 
1314  if (mustwait)
1315  {
1316  /* Failed to get lock, so release interrupt holdoff */
1318 
1319  LOG_LWDEBUG("LWLockConditionalAcquire", lock, "failed");
1320  TRACE_POSTGRESQL_LWLOCK_CONDACQUIRE_FAIL(T_NAME(lock), mode);
1321  }
1322  else
1323  {
1324  /* Add lock to list of locks held by this backend */
1327  TRACE_POSTGRESQL_LWLOCK_CONDACQUIRE(T_NAME(lock), mode);
1328  }
1329  return !mustwait;
1330 }
#define T_NAME(lock)
Definition: lwlock.c:117
static bool LWLockAttemptLock(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:738
#define MAX_SIMUL_LWLOCKS
Definition: lwlock.c:133
#define RESUME_INTERRUPTS()
Definition: miscadmin.h:117
static LWLockHandle held_lwlocks[MAX_SIMUL_LWLOCKS]
Definition: lwlock.c:143
#define ERROR
Definition: elog.h:43
LWLockMode mode
Definition: lwlock.c:139
#define AssertArg(condition)
Definition: c.h:682
static int num_held_lwlocks
Definition: lwlock.c:142
LWLock * lock
Definition: lwlock.c:138
#define PRINT_LWDEBUG(a, b, c)
Definition: lwlock.c:227
#define HOLD_INTERRUPTS()
Definition: miscadmin.h:115
#define elog
Definition: elog.h:219
#define LOG_LWDEBUG(a, b, c)
Definition: lwlock.c:228

◆ LWLockHeldByMe()

◆ LWLockHeldByMeInMode()

bool LWLockHeldByMeInMode ( LWLock lock,
LWLockMode  mode 
)

Definition at line 1858 of file lwlock.c.

References i, and num_held_lwlocks.

Referenced by dshash_delete_entry(), dshash_release_lock(), IsBufferCleanupOK(), logicalrep_worker_cleanup(), MarkAsPreparingGuts(), MarkBufferDirty(), PrepareRedoAdd(), PrepareRedoRemove(), ProcessTwoPhaseBuffer(), RemoveGXact(), and TransactionIdSetPageStatusInternal().

1859 {
1860  int i;
1861 
1862  for (i = 0; i < num_held_lwlocks; i++)
1863  {
1864  if (held_lwlocks[i].lock == l && held_lwlocks[i].mode == mode)
1865  return true;
1866  }
1867  return false;
1868 }
static LWLockHandle held_lwlocks[MAX_SIMUL_LWLOCKS]
Definition: lwlock.c:143
static int num_held_lwlocks
Definition: lwlock.c:142
int i

◆ LWLockInitialize()

void LWLockInitialize ( LWLock lock,
int  tranche_id 
)

Definition at line 676 of file lwlock.c.

References LW_FLAG_RELEASE_OK, pg_atomic_init_u32(), proclist_init(), LWLock::state, LWLock::tranche, and LWLock::waiters.

Referenced by apw_init_shmem(), create_internal(), dshash_create(), ExecAppendInitializeDSM(), ExecHashJoinInitializeDSM(), InitBufferPool(), InitializeLWLocks(), InitProcGlobal(), ReplicationOriginShmemInit(), ReplicationSlotsShmemInit(), SimpleLruInit(), sts_initialize(), tbm_prepare_shared_iterate(), and XLOGShmemInit().

677 {
679 #ifdef LOCK_DEBUG
680  pg_atomic_init_u32(&lock->nwaiters, 0);
681 #endif
682  lock->tranche = tranche_id;
683  proclist_init(&lock->waiters);
684 }
proclist_head waiters
Definition: lwlock.h:36
pg_atomic_uint32 state
Definition: lwlock.h:35
uint16 tranche
Definition: lwlock.h:34
#define LW_FLAG_RELEASE_OK
Definition: lwlock.c:100
static void proclist_init(proclist_head *list)
Definition: proclist.h:29
static void pg_atomic_init_u32(volatile pg_atomic_uint32 *ptr, uint32 val)
Definition: atomics.h:234

◆ LWLockNewTrancheId()

int LWLockNewTrancheId ( void  )

Definition at line 581 of file lwlock.c.

References ShmemLock, SpinLockAcquire, and SpinLockRelease.

Referenced by apw_init_shmem(), and InitializeLWLocks().

582 {
583  int result;
584  int *LWLockCounter;
585 
586  LWLockCounter = (int *) ((char *) MainLWLockArray - sizeof(int));
588  result = (*LWLockCounter)++;
590 
591  return result;
592 }
#define SpinLockAcquire(lock)
Definition: spin.h:62
#define SpinLockRelease(lock)
Definition: spin.h:64
slock_t * ShmemLock
Definition: shmem.c:84
LWLockPadded * MainLWLockArray
Definition: lwlock.c:125

◆ LWLockRegisterTranche()

void LWLockRegisterTranche ( int  tranche_id,
const char *  tranche_name 
)

Definition at line 601 of file lwlock.c.

References Assert, i, LWLockTrancheArray, LWLockTranchesAllocated, and repalloc().

Referenced by CreateSharedProcArray(), InitBufferPool(), RegisterLWLockTranches(), ReplicationOriginShmemInit(), ReplicationSlotsShmemInit(), SimpleLruInit(), and XLOGShmemInit().

602 {
603  Assert(LWLockTrancheArray != NULL);
604 
605  if (tranche_id >= LWLockTranchesAllocated)
606  {
608  int j = LWLockTranchesAllocated;
609 
610  while (i <= tranche_id)
611  i *= 2;
612 
613  LWLockTrancheArray = (const char **)
614  repalloc(LWLockTrancheArray, i * sizeof(char *));
616  while (j < LWLockTranchesAllocated)
617  LWLockTrancheArray[j++] = NULL;
618  }
619 
620  LWLockTrancheArray[tranche_id] = tranche_name;
621 }
static int LWLockTranchesAllocated
Definition: lwlock.c:115
static const char ** LWLockTrancheArray
Definition: lwlock.c:114
#define Assert(condition)
Definition: c.h:680
void * repalloc(void *pointer, Size size)
Definition: mcxt.c:949
int i

◆ LWLockRelease()

void LWLockRelease ( LWLock lock)

Definition at line 1724 of file lwlock.c.

References Assert, elog, ERROR, i, LOG_LWDEBUG, LW_EXCLUSIVE, LW_FLAG_HAS_WAITERS, LW_FLAG_RELEASE_OK, LW_LOCK_MASK, LW_VAL_EXCLUSIVE, LW_VAL_SHARED, LWLockWakeup(), LWLockHandle::mode, num_held_lwlocks, pg_atomic_sub_fetch_u32(), PRINT_LWDEBUG, RESUME_INTERRUPTS, and T_NAME.

Referenced by _bt_end_vacuum(), _bt_start_vacuum(), _bt_vacuum_cycleid(), AbsorbFsyncRequests(), ActivateCommitTs(), AdvanceOldestClogXid(), AdvanceOldestCommitTsXid(), AdvanceXLInsertBuffer(), alloc_object(), AlterSystemSetConfigFile(), analyze_rel(), ApplyLauncherMain(), apw_detach_shmem(), apw_dump_now(), apw_init_shmem(), apw_load_buffers(), asyncQueueAddEntries(), asyncQueueAdvanceTail(), asyncQueueReadAllNotifications(), asyncQueueUnregister(), AsyncShmemInit(), AtAbort_Twophase(), AtPrepare_PredicateLocks(), attach_internal(), autoprewarm_main(), autoprewarm_start_worker(), AutoVacLauncherMain(), AutoVacuumRequestWork(), AutoVacWorkerMain(), BackendIdGetProc(), BackendIdGetTransactionIds(), BackendPidGetProc(), BackendXidGetPid(), BecomeLockGroupLeader(), BecomeLockGroupMember(), BootStrapCLOG(), BootStrapMultiXact(), BootStrapSUBTRANS(), BufferAlloc(), CancelDBBackends(), CancelVirtualTransaction(), check_for_freed_segments(), CheckDeadLock(), CheckForSerializableConflictOut(), CheckPointPredicate(), CheckPointRelationMap(), CheckPointReplicationOrigin(), CheckPointReplicationSlots(), CheckPointTwoPhase(), CheckRecoveryConsistency(), CheckTableForSerializableConflictIn(), CheckTargetForConflictsIn(), choose_next_subplan_for_leader(), choose_next_subplan_for_worker(), CleanupInvalidationState(), ClearOldPredicateLocks(), clog_redo(), commit_ts_redo(), CountDBBackends(), CountDBConnections(), CountOtherDBBackends(), CountUserBackends(), CreateCheckPoint(), CreateEndOfRecoveryRecord(), CreateInitDecodingContext(), CreatePredicateLock(), CreateRestartPoint(), DeactivateCommitTs(), DeleteChildTargetLocks(), DeleteLockTarget(), destroy_superblock(), do_autovacuum(), do_pg_start_backup(), do_pg_stop_backup(), do_start_worker(), DropAllPredicateLocksFromTable(), DropSubscription(), DropTableSpace(), dsa_allocate_extended(), dsa_dump(), dsa_free(), dsa_pin(), dsa_release_in_place(), dsa_set_size_limit(), dsa_trim(), dsa_unpin(), dshash_delete_entry(), dshash_delete_key(), dshash_dump(), dshash_find(), dshash_find_or_insert(), dshash_release_lock(), dsm_attach(), dsm_create(), dsm_detach(), dsm_pin_segment(), dsm_unpin_segment(), ensure_active_superblock(), entry_reset(), Exec_ListenPreCommit(), ExecParallelHashMergeCounters(), ExecParallelHashPopChunkQueue(), ExecParallelHashTupleAlloc(), ExecParallelHashTuplePrealloc(), ExpireAllKnownAssignedTransactionIds(), ExpireOldKnownAssignedTransactionIds(), ExpireTreeKnownAssignedTransactionIds(), ExtendCLOG(), ExtendCommitTs(), ExtendMultiXactMember(), ExtendMultiXactOffset(), ExtendSUBTRANS(), FastPathGetRelationLockEntry(), FastPathTransferRelationLocks(), find_multixact_start(), FinishPreparedTransaction(), FlushDatabaseBuffers(), FlushRelationBuffers(), ForceTransactionIdLimitUpdate(), ForwardFsyncRequest(), FreeWorkerInfo(), GetBackgroundWorkerPid(), GetBackgroundWorkerTypeByPid(), GetBlockerStatusData(), GetConflictingVirtualXIDs(), GetCurrentVirtualXIDs(), GetLastImportantRecPtr(), GetLastSegSwitchData(), GetLatestCommitTsData(), GetLockConflicts(), GetLockStatusData(), GetMultiXactIdMembers(), GetNewMultiXactId(), GetNewObjectId(), GetNewTransactionId(), GetOldestActiveTransactionId(), GetOldestMultiXactId(), GetOldestRestartPoint(), GetOldestSafeDecodingTransactionId(), GetOldestXmin(), GetPredicateLockStatusData(), GetPreparedTransactionList(), GetRunningTransactionLocks(), GetSafeSnapshot(), GetSafeSnapshotBlockingPids(), GetSerializableTransactionSnapshotInt(), GetSnapshotData(), GetVirtualXIDsDelayingChkpt(), HaveVirtualXIDsDelayingChkpt(), InstallXLogFileSegment(), InvalidateBuffer(), KnownAssignedXidsAdd(), KnownAssignedXidsReset(), lock_twophase_recover(), LockAcquireExtended(), LockBuffer(), LockErrorCleanup(), LockGXact(), LockHasWaiters(), LockRefindAndRelease(), LockRelease(), LockReleaseAll(), LockWaiterCount(), logicalrep_worker_attach(), logicalrep_worker_detach(), logicalrep_worker_launch(), logicalrep_worker_stop(), logicalrep_worker_wakeup(), LogStandbySnapshot(), LWLockReleaseAll(), LWLockReleaseClearVar(), MaintainOldSnapshotTimeMapping(), MarkAsPrepared(), MarkAsPreparing(), MaybeExtendOffsetSlru(), multixact_redo(), MultiXactAdvanceNextMXact(), MultiXactGetCheckptMulti(), MultiXactIdSetOldestMember(), MultiXactIdSetOldestVisible(), MultiXactSetNextMXact(), OldSerXidAdd(), OldSerXidGetMinConflictCommitSeqNo(), OldSerXidSetActiveSerXmin(), OnConflict_CheckForSerializationFailure(), PageIsPredicateLocked(), perform_relmap_update(), pg_backend_random(), pg_get_replication_slots(), pg_notification_queue_usage(), pg_show_replication_origin_status(), pg_stat_get_subscription(), pg_stat_get_wal_senders(), pg_stat_statements_internal(), pgss_shmem_startup(), pgss_store(), PostPrepare_Locks(), PostPrepare_MultiXact(), PostPrepare_Twophase(), PreCommit_CheckForSerializationFailure(), PreCommit_Notify(), predicatelock_twophase_recover(), PredicateLockPageSplit(), PredicateLockTwoPhaseFinish(), PrefetchBuffer(), PrescanPreparedTransactions(), ProcArrayAdd(), ProcArrayApplyRecoveryInfo(), ProcArrayApplyXidAssignment(), ProcArrayEndTransaction(), ProcArrayGetReplicationSlotXmin(), ProcArrayGroupClearXid(), ProcArrayInstallImportedXmin(), ProcArrayInstallRestoredXmin(), ProcArrayRemove(), ProcArraySetReplicationSlotXmin(), process_syncing_tables_for_apply(), ProcessTwoPhaseBuffer(), ProcKill(), ProcSleep(), ReadMultiXactCounts(), ReadNewTransactionId(), ReadNextMultiXactId(), ReadRecord(), RecordKnownAssignedTransactionIds(), RecordNewMultiXact(), RecoverPreparedTransactions(), RegisterDynamicBackgroundWorker(), RegisterPredicateLockingXid(), RelationCacheInitFilePostInvalidate(), ReleaseOneSerializableXact(), ReleasePredicateLocks(), RemoveScratchTarget(), ReplicationOriginExitCleanup(), ReplicationSlotAcquire(), ReplicationSlotCleanup(), ReplicationSlotCreate(), ReplicationSlotDropPtr(), ReplicationSlotRelease(), ReplicationSlotsComputeLogicalRestartLSN(), ReplicationSlotsComputeRequiredLSN(), ReplicationSlotsComputeRequiredXmin(), ReplicationSlotsCountDBSlots(), ReplicationSlotsDropDBSlots(), replorigin_advance(), replorigin_drop(), replorigin_get_progress(), replorigin_session_advance(), replorigin_session_get_progress(), replorigin_session_reset(), replorigin_session_setup(), resize(), RestoreScratchTarget(), restoreTwoPhaseData(), SaveSlotToPath(), SetCommitTsLimit(), SetMultiXactIdLimit(), SetOffsetVacuumLimit(), SetTransactionIdLimit(), SetXidCommitTsInPage(), SharedInvalBackendInit(), ShmemInitStruct(), SICleanupQueue(), SIGetDataEntries(), SignalBackends(), SIInsertDataEntries(), SimpleLruFlush(), SimpleLruReadPage(), SimpleLruReadPage_ReadOnly(), SimpleLruTruncate(), SimpleLruWaitIO(), SlruDeleteSegment(), SlruInternalWritePage(), SnapBuildInitialSnapshot(), ss_get_location(), ss_report_location(), StandbyRecoverPreparedTransactions(), StartBufferIO(), StartupCLOG(), StartupDecodingContext(), StartupSUBTRANS(), StartupXLOG(), sts_parallel_scan_next(), SubTransGetParent(), SubTransSetParent(), SummarizeOldestCommittedSxact(), SyncOneBuffer(), SyncRepCancelWait(), SyncRepCleanupAtProcExit(), SyncRepInitConfig(), SyncRepReleaseWaiters(), SyncRepUpdateSyncStandbysDefined(), SyncRepWaitForLSN(), TablespaceCreateDbspace(), tbm_shared_iterate(), TerminateBackgroundWorker(), TerminateBufferIO(), TransactionGroupUpdateXidStatus(), TransactionIdGetCommitTsData(), TransactionIdGetStatus(), TransactionIdIsActive(), TransactionIdIsInProgress(), TransactionIdLimitedForOldSnapshots(), TransactionIdSetPageStatus(), TransactionTreeSetCommitTsData(), TransferPredicateLocksToNewTarget(), TrimCLOG(), TrimMultiXact(), TruncateMultiXact(), TwoPhaseGetGXact(), txid_status(), UpdateMinRecoveryPoint(), vacuum_rel(), VirtualXactLock(), VirtualXactLockTableCleanup(), VirtualXactLockTableInsert(), wait_for_relation_state_change(), wait_for_worker_state_change(), WaitForReplicationWorkerAttach(), WaitIO(), WaitOnLock(), write_relcache_init_file(), xact_redo(), xact_redo_abort(), xact_redo_commit(), XidCacheRemoveRunningXids(), xlog_redo(), XLogBackgroundFlush(), XLogFlush(), and XLogNeedsFlush().

1725 {
1726  LWLockMode mode;
1727  uint32 oldstate;
1728  bool check_waiters;
1729  int i;
1730 
1731  /*
1732  * Remove lock from list of locks held. Usually, but not always, it will
1733  * be the latest-acquired lock; so search array backwards.
1734  */
1735  for (i = num_held_lwlocks; --i >= 0;)
1736  if (lock == held_lwlocks[i].lock)
1737  break;
1738 
1739  if (i < 0)
1740  elog(ERROR, "lock %s is not held", T_NAME(lock));
1741 
1742  mode = held_lwlocks[i].mode;
1743 
1744  num_held_lwlocks--;
1745  for (; i < num_held_lwlocks; i++)
1746  held_lwlocks[i] = held_lwlocks[i + 1];
1747 
1748  PRINT_LWDEBUG("LWLockRelease", lock, mode);
1749 
1750  /*
1751  * Release my hold on lock, after that it can immediately be acquired by
1752  * others, even if we still have to wakeup other waiters.
1753  */
1754  if (mode == LW_EXCLUSIVE)
1755  oldstate = pg_atomic_sub_fetch_u32(&lock->state, LW_VAL_EXCLUSIVE);
1756  else
1757  oldstate = pg_atomic_sub_fetch_u32(&lock->state, LW_VAL_SHARED);
1758 
1759  /* nobody else can have that kind of lock */
1760  Assert(!(oldstate & LW_VAL_EXCLUSIVE));
1761 
1762 
1763  /*
1764  * We're still waiting for backends to get scheduled, don't wake them up
1765  * again.
1766  */
1767  if ((oldstate & (LW_FLAG_HAS_WAITERS | LW_FLAG_RELEASE_OK)) ==
1769  (oldstate & LW_LOCK_MASK) == 0)
1770  check_waiters = true;
1771  else
1772  check_waiters = false;
1773 
1774  /*
1775  * As waking up waiters requires the spinlock to be acquired, only do so
1776  * if necessary.
1777  */
1778  if (check_waiters)
1779  {
1780  /* XXX: remove before commit? */
1781  LOG_LWDEBUG("LWLockRelease", lock, "releasing waiters");
1782  LWLockWakeup(lock);
1783  }
1784 
1785  TRACE_POSTGRESQL_LWLOCK_RELEASE(T_NAME(lock));
1786 
1787  /*
1788  * Now okay to allow cancel/die interrupts.
1789  */
1791 }
#define T_NAME(lock)
Definition: lwlock.c:117
LWLockMode
Definition: lwlock.h:132
#define LW_FLAG_HAS_WAITERS
Definition: lwlock.c:99
static uint32 pg_atomic_sub_fetch_u32(volatile pg_atomic_uint32 *ptr, int32 sub_)
Definition: atomics.h:412
#define LW_LOCK_MASK
Definition: lwlock.c:106
#define LW_VAL_SHARED
Definition: lwlock.c:104
#define RESUME_INTERRUPTS()
Definition: miscadmin.h:117
static LWLockHandle held_lwlocks[MAX_SIMUL_LWLOCKS]
Definition: lwlock.c:143
#define ERROR
Definition: elog.h:43
LWLockMode mode
Definition: lwlock.c:139
static void LWLockWakeup(LWLock *lock)
Definition: lwlock.c:874
unsigned int uint32
Definition: c.h:306
static int num_held_lwlocks
Definition: lwlock.c:142
#define Assert(condition)
Definition: c.h:680
#define PRINT_LWDEBUG(a, b, c)
Definition: lwlock.c:227
#define LW_FLAG_RELEASE_OK
Definition: lwlock.c:100
#define LW_VAL_EXCLUSIVE
Definition: lwlock.c:103
int i
#define elog
Definition: elog.h:219
#define LOG_LWDEBUG(a, b, c)
Definition: lwlock.c:228

◆ LWLockReleaseAll()

void LWLockReleaseAll ( void  )

Definition at line 1823 of file lwlock.c.

References HOLD_INTERRUPTS, LWLockRelease(), and num_held_lwlocks.

Referenced by AbortSubTransaction(), AbortTransaction(), AutoVacLauncherMain(), AuxiliaryProcKill(), BackgroundWriterMain(), CheckpointerMain(), ProcKill(), ShutdownAuxiliaryProcess(), WalSndErrorCleanup(), and WalWriterMain().

1824 {
1825  while (num_held_lwlocks > 0)
1826  {
1827  HOLD_INTERRUPTS(); /* match the upcoming RESUME_INTERRUPTS */
1828 
1830  }
1831 }
void LWLockRelease(LWLock *lock)
Definition: lwlock.c:1724
static LWLockHandle held_lwlocks[MAX_SIMUL_LWLOCKS]
Definition: lwlock.c:143
static int num_held_lwlocks
Definition: lwlock.c:142
#define HOLD_INTERRUPTS()
Definition: miscadmin.h:115

◆ LWLockReleaseClearVar()

void LWLockReleaseClearVar ( LWLock lock,
uint64 *  valptr,
uint64  val 
)

Definition at line 1797 of file lwlock.c.

References LWLockRelease(), LWLockWaitListLock(), LWLockWaitListUnlock(), and val.

Referenced by WALInsertLockRelease().

1798 {
1799  LWLockWaitListLock(lock);
1800 
1801  /*
1802  * Set the variable's value before releasing the lock, that prevents race
1803  * a race condition wherein a new locker acquires the lock, but hasn't yet
1804  * set the variables value.
1805  */
1806  *valptr = val;
1807  LWLockWaitListUnlock(lock);
1808 
1809  LWLockRelease(lock);
1810 }
static void LWLockWaitListUnlock(LWLock *lock)
Definition: lwlock.c:861
void LWLockRelease(LWLock *lock)
Definition: lwlock.c:1724
static void LWLockWaitListLock(LWLock *lock)
Definition: lwlock.c:809
long val
Definition: informix.c:689

◆ LWLockShmemSize()

Size LWLockShmemSize ( void  )

Definition at line 349 of file lwlock.c.

References add_size(), i, lock_named_request_allowed, LWLOCK_PADDED_SIZE, mul_size(), NamedLWLockTrancheRequests, NUM_FIXED_LWLOCKS, and NumLWLocksByNamedTranches().

Referenced by CreateLWLocks(), and CreateSharedMemoryAndSemaphores().

350 {
351  Size size;
352  int i;
353  int numLocks = NUM_FIXED_LWLOCKS;
354 
355  numLocks += NumLWLocksByNamedTranches();
356 
357  /* Space for the LWLock array. */
358  size = mul_size(numLocks, sizeof(LWLockPadded));
359 
360  /* Space for dynamic allocation counter, plus room for alignment. */
361  size = add_size(size, sizeof(int) + LWLOCK_PADDED_SIZE);
362 
363  /* space for named tranches. */
365 
366  /* space for name of each tranche. */
367  for (i = 0; i < NamedLWLockTrancheRequests; i++)
368  size = add_size(size, strlen(NamedLWLockTrancheRequestArray[i].tranche_name) + 1);
369 
370  /* Disallow named LWLocks' requests after startup */
372 
373  return size;
374 }
static bool lock_named_request_allowed
Definition: lwlock.c:158
#define NUM_FIXED_LWLOCKS
Definition: lwlock.h:129
int NamedLWLockTrancheRequests
Definition: lwlock.c:154
Size mul_size(Size s1, Size s2)
Definition: shmem.c:492
Size add_size(Size s1, Size s2)
Definition: shmem.c:475
size_t Size
Definition: c.h:414
static int NumLWLocksByNamedTranches(void)
Definition: lwlock.c:334
NamedLWLockTrancheRequest * NamedLWLockTrancheRequestArray
Definition: lwlock.c:152
int i
#define LWLOCK_PADDED_SIZE
Definition: lwlock.h:73

◆ LWLockUpdateVar()

void LWLockUpdateVar ( LWLock lock,
uint64 *  valptr,
uint64  value 
)

Definition at line 1670 of file lwlock.c.

References Assert, proclist_mutable_iter::cur, GetPGProcByNumber, LW_EXCLUSIVE, LW_VAL_EXCLUSIVE, LW_WAIT_UNTIL_FREE, LWLockWaitListLock(), LWLockWaitListUnlock(), PGPROC::lwWaiting, PGPROC::lwWaitMode, pg_atomic_read_u32(), pg_write_barrier, PGSemaphoreUnlock(), PRINT_LWDEBUG, proclist_delete, proclist_foreach_modify, proclist_init(), proclist_push_tail, PGPROC::sem, LWLock::state, val, and LWLock::waiters.

Referenced by WALInsertLockAcquireExclusive(), and WALInsertLockUpdateInsertingAt().

1671 {
1672  proclist_head wakeup;
1673  proclist_mutable_iter iter;
1674 
1675  PRINT_LWDEBUG("LWLockUpdateVar", lock, LW_EXCLUSIVE);
1676 
1677  proclist_init(&wakeup);
1678 
1679  LWLockWaitListLock(lock);
1680 
1682 
1683  /* Update the lock's value */
1684  *valptr = val;
1685 
1686  /*
1687  * See if there are any LW_WAIT_UNTIL_FREE waiters that need to be woken
1688  * up. They are always in the front of the queue.
1689  */
1690  proclist_foreach_modify(iter, &lock->waiters, lwWaitLink)
1691  {
1692  PGPROC *waiter = GetPGProcByNumber(iter.cur);
1693 
1694  if (waiter->lwWaitMode != LW_WAIT_UNTIL_FREE)
1695  break;
1696 
1697  proclist_delete(&lock->waiters, iter.cur, lwWaitLink);
1698  proclist_push_tail(&wakeup, iter.cur, lwWaitLink);
1699  }
1700 
1701  /* We are done updating shared state of the lock itself. */
1702  LWLockWaitListUnlock(lock);
1703 
1704  /*
1705  * Awaken any waiters I removed from the queue.
1706  */
1707  proclist_foreach_modify(iter, &wakeup, lwWaitLink)
1708  {
1709  PGPROC *waiter = GetPGProcByNumber(iter.cur);
1710 
1711  proclist_delete(&wakeup, iter.cur, lwWaitLink);
1712  /* check comment in LWLockWakeup() about this barrier */
1713  pg_write_barrier();
1714  waiter->lwWaiting = false;
1715  PGSemaphoreUnlock(waiter->sem);
1716  }
1717 }
#define GetPGProcByNumber(n)
Definition: proc.h:277
void PGSemaphoreUnlock(PGSemaphore sema)
Definition: posix_sema.c:323
proclist_head waiters
Definition: lwlock.h:36
bool lwWaiting
Definition: proc.h:127
static void LWLockWaitListUnlock(LWLock *lock)
Definition: lwlock.c:861
#define proclist_foreach_modify(iter, lhead, link_member)
Definition: proclist.h:206
uint8 lwWaitMode
Definition: proc.h:128
pg_atomic_uint32 state
Definition: lwlock.h:35
#define proclist_delete(list, procno, link_member)
Definition: proclist.h:187
#define Assert(condition)
Definition: c.h:680
#define PRINT_LWDEBUG(a, b, c)
Definition: lwlock.c:227
#define proclist_push_tail(list, procno, link_member)
Definition: proclist.h:191
static void LWLockWaitListLock(LWLock *lock)
Definition: lwlock.c:809
#define LW_VAL_EXCLUSIVE
Definition: lwlock.c:103
static void proclist_init(proclist_head *list)
Definition: proclist.h:29
#define pg_write_barrier()
Definition: atomics.h:162
PGSemaphore sem
Definition: proc.h:101
Definition: proc.h:95
long val
Definition: informix.c:689
static uint32 pg_atomic_read_u32(volatile pg_atomic_uint32 *ptr)
Definition: atomics.h:252

◆ LWLockWaitForVar()

bool LWLockWaitForVar ( LWLock lock,
uint64 *  valptr,
uint64  oldval,
uint64 *  newval 
)

Definition at line 1531 of file lwlock.c.

References Assert, HOLD_INTERRUPTS, LOG_LWDEBUG, LW_EXCLUSIVE, LW_FLAG_RELEASE_OK, LW_WAIT_UNTIL_FREE, LWLockConflictsWithVar(), LWLockDequeueSelf(), LWLockQueueSelf(), LWLockReportWaitEnd(), LWLockReportWaitStart(), PGPROC::lwWaiting, MAX_BACKENDS, MyProc, pg_atomic_fetch_or_u32(), pg_atomic_fetch_sub_u32(), PG_USED_FOR_ASSERTS_ONLY, PGSemaphoreLock(), PGSemaphoreUnlock(), PRINT_LWDEBUG, RESUME_INTERRUPTS, PGPROC::sem, LWLock::state, and T_NAME.

Referenced by WaitXLogInsertionsToFinish().

1532 {
1533  PGPROC *proc = MyProc;
1534  int extraWaits = 0;
1535  bool result = false;
1536 #ifdef LWLOCK_STATS
1537  lwlock_stats *lwstats;
1538 
1539  lwstats = get_lwlock_stats_entry(lock);
1540 #endif
1541 
1542  PRINT_LWDEBUG("LWLockWaitForVar", lock, LW_WAIT_UNTIL_FREE);
1543 
1544  /*
1545  * Lock out cancel/die interrupts while we sleep on the lock. There is no
1546  * cleanup mechanism to remove us from the wait queue if we got
1547  * interrupted.
1548  */
1549  HOLD_INTERRUPTS();
1550 
1551  /*
1552  * Loop here to check the lock's status after each time we are signaled.
1553  */
1554  for (;;)
1555  {
1556  bool mustwait;
1557 
1558  mustwait = LWLockConflictsWithVar(lock, valptr, oldval, newval,
1559  &result);
1560 
1561  if (!mustwait)
1562  break; /* the lock was free or value didn't match */
1563 
1564  /*
1565  * Add myself to wait queue. Note that this is racy, somebody else
1566  * could wakeup before we're finished queuing. NB: We're using nearly
1567  * the same twice-in-a-row lock acquisition protocol as
1568  * LWLockAcquire(). Check its comments for details. The only
1569  * difference is that we also have to check the variable's values when
1570  * checking the state of the lock.
1571  */
1573 
1574  /*
1575  * Set RELEASE_OK flag, to make sure we get woken up as soon as the
1576  * lock is released.
1577  */
1579 
1580  /*
1581  * We're now guaranteed to be woken up if necessary. Recheck the lock
1582  * and variables state.
1583  */
1584  mustwait = LWLockConflictsWithVar(lock, valptr, oldval, newval,
1585  &result);
1586 
1587  /* Ok, no conflict after we queued ourselves. Undo queueing. */
1588  if (!mustwait)
1589  {
1590  LOG_LWDEBUG("LWLockWaitForVar", lock, "free, undoing queue");
1591 
1592  LWLockDequeueSelf(lock);
1593  break;
1594  }
1595 
1596  /*
1597  * Wait until awakened.
1598  *
1599  * Since we share the process wait semaphore with the regular lock
1600  * manager and ProcWaitForSignal, and we may need to acquire an LWLock
1601  * while one of those is pending, it is possible that we get awakened
1602  * for a reason other than being signaled by LWLockRelease. If so,
1603  * loop back and wait again. Once we've gotten the LWLock,
1604  * re-increment the sema by the number of additional signals received,
1605  * so that the lock manager or signal manager will see the received
1606  * signal when it next waits.
1607  */
1608  LOG_LWDEBUG("LWLockWaitForVar", lock, "waiting");
1609 
1610 #ifdef LWLOCK_STATS
1611  lwstats->block_count++;
1612 #endif
1613 
1614  LWLockReportWaitStart(lock);
1615  TRACE_POSTGRESQL_LWLOCK_WAIT_START(T_NAME(lock), LW_EXCLUSIVE);
1616 
1617  for (;;)
1618  {
1619  PGSemaphoreLock(proc->sem);
1620  if (!proc->lwWaiting)
1621  break;
1622  extraWaits++;
1623  }
1624 
1625 #ifdef LOCK_DEBUG
1626  {
1627  /* not waiting anymore */
1628  uint32 nwaiters PG_USED_FOR_ASSERTS_ONLY = pg_atomic_fetch_sub_u32(&lock->nwaiters, 1);
1629 
1630  Assert(nwaiters < MAX_BACKENDS);
1631  }
1632 #endif
1633 
1634  TRACE_POSTGRESQL_LWLOCK_WAIT_DONE(T_NAME(lock), LW_EXCLUSIVE);
1636 
1637  LOG_LWDEBUG("LWLockWaitForVar", lock, "awakened");
1638 
1639  /* Now loop back and check the status of the lock again. */
1640  }
1641 
1642  TRACE_POSTGRESQL_LWLOCK_ACQUIRE(T_NAME(lock), LW_EXCLUSIVE);
1643 
1644  /*
1645  * Fix the process wait semaphore's count for any absorbed wakeups.
1646  */
1647  while (extraWaits-- > 0)
1648  PGSemaphoreUnlock(proc->sem);
1649 
1650  /*
1651  * Now okay to allow cancel/die interrupts.
1652  */
1654 
1655  return result;
1656 }
#define T_NAME(lock)
Definition: lwlock.c:117
static uint32 pg_atomic_fetch_sub_u32(volatile pg_atomic_uint32 *ptr, int32 sub_)
Definition: atomics.h:354
void PGSemaphoreUnlock(PGSemaphore sema)
Definition: posix_sema.c:323
PGPROC * MyProc
Definition: proc.c:67
bool lwWaiting
Definition: proc.h:127
pg_atomic_uint32 state
Definition: lwlock.h:35
#define RESUME_INTERRUPTS()
Definition: miscadmin.h:117
#define MAX_BACKENDS
Definition: postmaster.h:75
static void LWLockReportWaitEnd(void)
Definition: lwlock.c:703
unsigned int uint32
Definition: c.h:306
static void LWLockDequeueSelf(LWLock *lock)
Definition: lwlock.c:1025
static void LWLockReportWaitStart(LWLock *lock)
Definition: lwlock.c:694
static void LWLockQueueSelf(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:981
#define Assert(condition)
Definition: c.h:680
#define newval
#define PRINT_LWDEBUG(a, b, c)
Definition: lwlock.c:227
#define LW_FLAG_RELEASE_OK
Definition: lwlock.c:100
void PGSemaphoreLock(PGSemaphore sema)
Definition: posix_sema.c:303
static bool LWLockConflictsWithVar(LWLock *lock, uint64 *valptr, uint64 oldval, uint64 *newval, bool *result)
Definition: lwlock.c:1471
#define HOLD_INTERRUPTS()
Definition: miscadmin.h:115
static uint32 pg_atomic_fetch_or_u32(volatile pg_atomic_uint32 *ptr, uint32 or_)
Definition: atomics.h:383
PGSemaphore sem
Definition: proc.h:101
#define PG_USED_FOR_ASSERTS_ONLY
Definition: c.h:122
Definition: proc.h:95
#define LOG_LWDEBUG(a, b, c)
Definition: lwlock.c:228

◆ RequestNamedLWLockTranche()

void RequestNamedLWLockTranche ( const char *  tranche_name,
int  num_lwlocks 
)

Definition at line 636 of file lwlock.c.

References Assert, i, IsUnderPostmaster, lock_named_request_allowed, MemoryContextAlloc(), NAMEDATALEN, NamedLWLockTrancheRequests, NamedLWLockTrancheRequestsAllocated, NamedLWLockTrancheRequest::num_lwlocks, repalloc(), StrNCpy, TopMemoryContext, and NamedLWLockTrancheRequest::tranche_name.

Referenced by _PG_init().

637 {
638  NamedLWLockTrancheRequest *request;
639 
641  return; /* too late */
642 
643  if (NamedLWLockTrancheRequestArray == NULL)
644  {
649  * sizeof(NamedLWLockTrancheRequest));
650  }
651 
653  {
655 
656  while (i <= NamedLWLockTrancheRequests)
657  i *= 2;
658 
661  i * sizeof(NamedLWLockTrancheRequest));
663  }
664 
666  Assert(strlen(tranche_name) + 1 < NAMEDATALEN);
667  StrNCpy(request->tranche_name, tranche_name, NAMEDATALEN);
668  request->num_lwlocks = num_lwlocks;
670 }
static bool lock_named_request_allowed
Definition: lwlock.c:158
char tranche_name[NAMEDATALEN]
Definition: lwlock.c:148
#define NAMEDATALEN
int NamedLWLockTrancheRequests
Definition: lwlock.c:154
bool IsUnderPostmaster
Definition: globals.c:101
MemoryContext TopMemoryContext
Definition: mcxt.c:43
static int NamedLWLockTrancheRequestsAllocated
Definition: lwlock.c:153
#define Assert(condition)
Definition: c.h:680
#define StrNCpy(dst, src, len)
Definition: c.h:850
void * repalloc(void *pointer, Size size)
Definition: mcxt.c:949
NamedLWLockTrancheRequest * NamedLWLockTrancheRequestArray
Definition: lwlock.c:152
void * MemoryContextAlloc(MemoryContext context, Size size)
Definition: mcxt.c:693
int i

Variable Documentation

◆ MainLWLockArray

PGDLLIMPORT LWLockPadded* MainLWLockArray

Definition at line 125 of file lwlock.c.

Referenced by PostmasterMarkPIDForWorkerNotify().

◆ MainLWLockNames

char* MainLWLockNames[]

Referenced by RegisterLWLockTranches().

◆ NamedLWLockTrancheArray

PGDLLIMPORT NamedLWLockTranche* NamedLWLockTrancheArray

Definition at line 156 of file lwlock.c.

Referenced by PostmasterMarkPIDForWorkerNotify().

◆ NamedLWLockTrancheRequests