PostgreSQL Source Code  git master
lwlock.c File Reference
#include "postgres.h"
#include "miscadmin.h"
#include "pgstat.h"
#include "pg_trace.h"
#include "postmaster/postmaster.h"
#include "replication/slot.h"
#include "storage/ipc.h"
#include "storage/predicate.h"
#include "storage/proc.h"
#include "storage/proclist.h"
#include "storage/spin.h"
#include "utils/memutils.h"
Include dependency graph for lwlock.c:

Go to the source code of this file.

Data Structures

struct  LWLockHandle
 
struct  NamedLWLockTrancheRequest
 

Macros

#define LW_FLAG_HAS_WAITERS   ((uint32) 1 << 30)
 
#define LW_FLAG_RELEASE_OK   ((uint32) 1 << 29)
 
#define LW_FLAG_LOCKED   ((uint32) 1 << 28)
 
#define LW_VAL_EXCLUSIVE   ((uint32) 1 << 24)
 
#define LW_VAL_SHARED   1
 
#define LW_LOCK_MASK   ((uint32) ((1 << 25)-1))
 
#define LW_SHARED_MASK   ((uint32) ((1 << 24)-1))
 
#define T_NAME(lock)   (LWLockTrancheArray[(lock)->tranche])
 
#define MAX_SIMUL_LWLOCKS   200
 
#define PRINT_LWDEBUG(a, b, c)   ((void)0)
 
#define LOG_LWDEBUG(a, b, c)   ((void)0)
 

Typedefs

typedef struct LWLockHandle LWLockHandle
 
typedef struct NamedLWLockTrancheRequest NamedLWLockTrancheRequest
 

Functions

static void InitializeLWLocks (void)
 
static void RegisterLWLockTranches (void)
 
static void LWLockReportWaitStart (LWLock *lock)
 
static void LWLockReportWaitEnd (void)
 
static int NumLWLocksByNamedTranches (void)
 
Size LWLockShmemSize (void)
 
void CreateLWLocks (void)
 
void InitLWLockAccess (void)
 
LWLockPaddedGetNamedLWLockTranche (const char *tranche_name)
 
int LWLockNewTrancheId (void)
 
void LWLockRegisterTranche (int tranche_id, const char *tranche_name)
 
void RequestNamedLWLockTranche (const char *tranche_name, int num_lwlocks)
 
void LWLockInitialize (LWLock *lock, int tranche_id)
 
const char * GetLWLockIdentifier (uint32 classId, uint16 eventId)
 
static bool LWLockAttemptLock (LWLock *lock, LWLockMode mode)
 
static void LWLockWaitListLock (LWLock *lock)
 
static void LWLockWaitListUnlock (LWLock *lock)
 
static void LWLockWakeup (LWLock *lock)
 
static void LWLockQueueSelf (LWLock *lock, LWLockMode mode)
 
static void LWLockDequeueSelf (LWLock *lock)
 
bool LWLockAcquire (LWLock *lock, LWLockMode mode)
 
bool LWLockConditionalAcquire (LWLock *lock, LWLockMode mode)
 
bool LWLockAcquireOrWait (LWLock *lock, LWLockMode mode)
 
static bool LWLockConflictsWithVar (LWLock *lock, uint64 *valptr, uint64 oldval, uint64 *newval, bool *result)
 
bool LWLockWaitForVar (LWLock *lock, uint64 *valptr, uint64 oldval, uint64 *newval)
 
void LWLockUpdateVar (LWLock *lock, uint64 *valptr, uint64 val)
 
void LWLockRelease (LWLock *lock)
 
void LWLockReleaseClearVar (LWLock *lock, uint64 *valptr, uint64 val)
 
void LWLockReleaseAll (void)
 
bool LWLockHeldByMe (LWLock *l)
 
bool LWLockHeldByMeInMode (LWLock *l, LWLockMode mode)
 

Variables

slock_tShmemLock
 
static const char ** LWLockTrancheArray = NULL
 
static int LWLockTranchesAllocated = 0
 
LWLockPaddedMainLWLockArray = NULL
 
static int num_held_lwlocks = 0
 
static LWLockHandle held_lwlocks [MAX_SIMUL_LWLOCKS]
 
NamedLWLockTrancheRequestNamedLWLockTrancheRequestArray = NULL
 
static int NamedLWLockTrancheRequestsAllocated = 0
 
int NamedLWLockTrancheRequests = 0
 
NamedLWLockTrancheNamedLWLockTrancheArray = NULL
 
static bool lock_named_request_allowed = true
 

Macro Definition Documentation

◆ LOG_LWDEBUG

#define LOG_LWDEBUG (   a,
  b,
  c 
)    ((void)0)

◆ LW_FLAG_HAS_WAITERS

#define LW_FLAG_HAS_WAITERS   ((uint32) 1 << 30)

Definition at line 99 of file lwlock.c.

Referenced by LWLockDequeueSelf(), LWLockQueueSelf(), LWLockRelease(), and LWLockWakeup().

◆ LW_FLAG_LOCKED

#define LW_FLAG_LOCKED   ((uint32) 1 << 28)

Definition at line 101 of file lwlock.c.

Referenced by LWLockWaitListLock(), LWLockWaitListUnlock(), and LWLockWakeup().

◆ LW_FLAG_RELEASE_OK

#define LW_FLAG_RELEASE_OK   ((uint32) 1 << 29)

◆ LW_LOCK_MASK

#define LW_LOCK_MASK   ((uint32) ((1 << 25)-1))

Definition at line 106 of file lwlock.c.

Referenced by LWLockAttemptLock(), and LWLockRelease().

◆ LW_SHARED_MASK

#define LW_SHARED_MASK   ((uint32) ((1 << 24)-1))

Definition at line 108 of file lwlock.c.

◆ LW_VAL_EXCLUSIVE

#define LW_VAL_EXCLUSIVE   ((uint32) 1 << 24)

◆ LW_VAL_SHARED

#define LW_VAL_SHARED   1

Definition at line 104 of file lwlock.c.

Referenced by LWLockAttemptLock(), and LWLockRelease().

◆ MAX_SIMUL_LWLOCKS

#define MAX_SIMUL_LWLOCKS   200

Definition at line 133 of file lwlock.c.

Referenced by LWLockAcquire(), LWLockAcquireOrWait(), and LWLockConditionalAcquire().

◆ PRINT_LWDEBUG

#define PRINT_LWDEBUG (   a,
  b,
  c 
)    ((void)0)

◆ T_NAME

#define T_NAME (   lock)    (LWLockTrancheArray[(lock)->tranche])

Typedef Documentation

◆ LWLockHandle

◆ NamedLWLockTrancheRequest

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 StaticAssertStmt.

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 StaticAssertStmt(condition, errmessage)
Definition: c.h:784
#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:314
static void InitializeLWLocks(void)
Definition: lwlock.c:426
size_t Size
Definition: c.h:422
#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:688
#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

◆ InitializeLWLocks()

static void InitializeLWLocks ( void  )
static

Definition at line 426 of file lwlock.c.

References i, LWLockPadded::lock, LWLockHandle::lock, LWLockInitialize(), LWLockNewTrancheId(), LWTRANCHE_BUFFER_MAPPING, LWTRANCHE_LOCK_MANAGER, LWTRANCHE_PREDICATE_LOCK_MANAGER, name, NamedLWLockTrancheRequests, NUM_BUFFER_PARTITIONS, NUM_FIXED_LWLOCKS, NUM_LOCK_PARTITIONS, NamedLWLockTrancheRequest::num_lwlocks, NUM_PREDICATELOCK_PARTITIONS, NumLWLocksByNamedTranches(), NamedLWLockTrancheRequest::tranche_name, NamedLWLockTranche::trancheId, and NamedLWLockTranche::trancheName.

Referenced by CreateLWLocks().

427 {
428  int numNamedLocks = NumLWLocksByNamedTranches();
429  int id;
430  int i;
431  int j;
432  LWLockPadded *lock;
433 
434  /* Initialize all individual LWLocks in main array */
435  for (id = 0, lock = MainLWLockArray; id < NUM_INDIVIDUAL_LWLOCKS; id++, lock++)
436  LWLockInitialize(&lock->lock, id);
437 
438  /* Initialize buffer mapping LWLocks in main array */
439  lock = MainLWLockArray + NUM_INDIVIDUAL_LWLOCKS;
440  for (id = 0; id < NUM_BUFFER_PARTITIONS; id++, lock++)
442 
443  /* Initialize lmgrs' LWLocks in main array */
444  lock = MainLWLockArray + NUM_INDIVIDUAL_LWLOCKS + NUM_BUFFER_PARTITIONS;
445  for (id = 0; id < NUM_LOCK_PARTITIONS; id++, lock++)
447 
448  /* Initialize predicate lmgrs' LWLocks in main array */
449  lock = MainLWLockArray + NUM_INDIVIDUAL_LWLOCKS +
450  NUM_BUFFER_PARTITIONS + NUM_LOCK_PARTITIONS;
451  for (id = 0; id < NUM_PREDICATELOCK_PARTITIONS; id++, lock++)
453 
454  /* Initialize named tranches. */
456  {
457  char *trancheNames;
458 
460  &MainLWLockArray[NUM_FIXED_LWLOCKS + numNamedLocks];
461 
462  trancheNames = (char *) NamedLWLockTrancheArray +
465 
466  for (i = 0; i < NamedLWLockTrancheRequests; i++)
467  {
468  NamedLWLockTrancheRequest *request;
469  NamedLWLockTranche *tranche;
470  char *name;
471 
472  request = &NamedLWLockTrancheRequestArray[i];
473  tranche = &NamedLWLockTrancheArray[i];
474 
475  name = trancheNames;
476  trancheNames += strlen(request->tranche_name) + 1;
477  strcpy(name, request->tranche_name);
478  tranche->trancheId = LWLockNewTrancheId();
479  tranche->trancheName = name;
480 
481  for (j = 0; j < request->num_lwlocks; j++, lock++)
482  LWLockInitialize(&lock->lock, tranche->trancheId);
483  }
484  }
485 }
int LWLockNewTrancheId(void)
Definition: lwlock.c:581
char tranche_name[NAMEDATALEN]
Definition: lwlock.c:148
NamedLWLockTranche * NamedLWLockTrancheArray
Definition: lwlock.c:156
#define NUM_FIXED_LWLOCKS
Definition: lwlock.h:129
int NamedLWLockTrancheRequests
Definition: lwlock.c:154
#define NUM_BUFFER_PARTITIONS
Definition: lwlock.h:113
char * trancheName
Definition: lwlock.h:97
void LWLockInitialize(LWLock *lock, int tranche_id)
Definition: lwlock.c:676
LWLock lock
Definition: lwlock.h:79
static int NumLWLocksByNamedTranches(void)
Definition: lwlock.c:334
const char * name
Definition: encode.c:521
NamedLWLockTrancheRequest * NamedLWLockTrancheRequestArray
Definition: lwlock.c:152
int i
LWLockPadded * MainLWLockArray
Definition: lwlock.c:125
#define NUM_LOCK_PARTITIONS
Definition: lwlock.h:117
#define NUM_PREDICATELOCK_PARTITIONS
Definition: lwlock.h:121

◆ 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:314
static void LWLockDequeueSelf(LWLock *lock)
Definition: lwlock.c:1025
#define AssertArg(condition)
Definition: c.h:690
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:688
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:123
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:314
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:688
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:123
Definition: proc.h:95
#define LOG_LWDEBUG(a, b, c)
Definition: lwlock.c:228

◆ LWLockAttemptLock()

static bool LWLockAttemptLock ( LWLock lock,
LWLockMode  mode 
)
static

Definition at line 738 of file lwlock.c.

References AssertArg, LW_EXCLUSIVE, LW_LOCK_MASK, LW_SHARED, LW_VAL_EXCLUSIVE, LW_VAL_SHARED, MyProc, pg_atomic_compare_exchange_u32(), pg_atomic_read_u32(), pg_unreachable, and LWLock::state.

Referenced by LWLockAcquire(), LWLockAcquireOrWait(), and LWLockConditionalAcquire().

739 {
740  uint32 old_state;
741 
742  AssertArg(mode == LW_EXCLUSIVE || mode == LW_SHARED);
743 
744  /*
745  * Read once outside the loop, later iterations will get the newer value
746  * via compare & exchange.
747  */
748  old_state = pg_atomic_read_u32(&lock->state);
749 
750  /* loop until we've determined whether we could acquire the lock or not */
751  while (true)
752  {
753  uint32 desired_state;
754  bool lock_free;
755 
756  desired_state = old_state;
757 
758  if (mode == LW_EXCLUSIVE)
759  {
760  lock_free = (old_state & LW_LOCK_MASK) == 0;
761  if (lock_free)
762  desired_state += LW_VAL_EXCLUSIVE;
763  }
764  else
765  {
766  lock_free = (old_state & LW_VAL_EXCLUSIVE) == 0;
767  if (lock_free)
768  desired_state += LW_VAL_SHARED;
769  }
770 
771  /*
772  * Attempt to swap in the state we are expecting. If we didn't see
773  * lock to be free, that's just the old value. If we saw it as free,
774  * we'll attempt to mark it acquired. The reason that we always swap
775  * in the value is that this doubles as a memory barrier. We could try
776  * to be smarter and only swap in values if we saw the lock as free,
777  * but benchmark haven't shown it as beneficial so far.
778  *
779  * Retry if the value changed since we last looked at it.
780  */
782  &old_state, desired_state))
783  {
784  if (lock_free)
785  {
786  /* Great! Got the lock. */
787 #ifdef LOCK_DEBUG
788  if (mode == LW_EXCLUSIVE)
789  lock->owner = MyProc;
790 #endif
791  return false;
792  }
793  else
794  return true; /* somebody else has the lock */
795  }
796  }
797  pg_unreachable();
798 }
#define pg_unreachable()
Definition: c.h:193
static bool pg_atomic_compare_exchange_u32(volatile pg_atomic_uint32 *ptr, uint32 *expected, uint32 newval)
Definition: atomics.h:322
PGPROC * MyProc
Definition: proc.c:67
pg_atomic_uint32 state
Definition: lwlock.h:35
#define LW_LOCK_MASK
Definition: lwlock.c:106
#define LW_VAL_SHARED
Definition: lwlock.c:104
unsigned int uint32
Definition: c.h:314
#define AssertArg(condition)
Definition: c.h:690
#define LW_VAL_EXCLUSIVE
Definition: lwlock.c:103
static uint32 pg_atomic_read_u32(volatile pg_atomic_uint32 *ptr)
Definition: atomics.h:252

◆ 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:690
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

◆ LWLockConflictsWithVar()

static bool LWLockConflictsWithVar ( LWLock lock,
uint64 *  valptr,
uint64  oldval,
uint64 *  newval,
bool result 
)
static

Definition at line 1471 of file lwlock.c.

References LW_VAL_EXCLUSIVE, LWLockWaitListLock(), LWLockWaitListUnlock(), pg_atomic_read_u32(), LWLock::state, and value.

Referenced by LWLockWaitForVar().

1474 {
1475  bool mustwait;
1476  uint64 value;
1477 
1478  /*
1479  * Test first to see if it the slot is free right now.
1480  *
1481  * XXX: the caller uses a spinlock before this, so we don't need a memory
1482  * barrier here as far as the current usage is concerned. But that might
1483  * not be safe in general.
1484  */
1485  mustwait = (pg_atomic_read_u32(&lock->state) & LW_VAL_EXCLUSIVE) != 0;
1486 
1487  if (!mustwait)
1488  {
1489  *result = true;
1490  return false;
1491  }
1492 
1493  *result = false;
1494 
1495  /*
1496  * Read value using the lwlock's wait list lock, as we can't generally
1497  * rely on atomic 64 bit reads/stores. TODO: On platforms with a way to
1498  * do atomic 64 bit reads/writes the spinlock should be optimized away.
1499  */
1500  LWLockWaitListLock(lock);
1501  value = *valptr;
1502  LWLockWaitListUnlock(lock);
1503 
1504  if (value != oldval)
1505  {
1506  mustwait = false;
1507  *newval = value;
1508  }
1509  else
1510  {
1511  mustwait = true;
1512  }
1513 
1514  return mustwait;
1515 }
static struct @130 value
static void LWLockWaitListUnlock(LWLock *lock)
Definition: lwlock.c:861
pg_atomic_uint32 state
Definition: lwlock.h:35
#define newval
static void LWLockWaitListLock(LWLock *lock)
Definition: lwlock.c:809
#define LW_VAL_EXCLUSIVE
Definition: lwlock.c:103
static uint32 pg_atomic_read_u32(volatile pg_atomic_uint32 *ptr)
Definition: atomics.h:252

◆ LWLockDequeueSelf()

static void LWLockDequeueSelf ( LWLock lock)
static

Definition at line 1025 of file lwlock.c.

References Assert, proclist_mutable_iter::cur, LW_FLAG_HAS_WAITERS, LW_FLAG_RELEASE_OK, LWLockWaitListLock(), LWLockWaitListUnlock(), PGPROC::lwWaiting, MAX_BACKENDS, MyProc, pg_atomic_fetch_and_u32(), pg_atomic_fetch_or_u32(), pg_atomic_fetch_sub_u32(), pg_atomic_read_u32(), PG_USED_FOR_ASSERTS_ONLY, PGPROC::pgprocno, PGSemaphoreLock(), PGSemaphoreUnlock(), proclist_delete, proclist_foreach_modify, proclist_is_empty(), PGPROC::sem, LWLock::state, and LWLock::waiters.

Referenced by LWLockAcquire(), LWLockAcquireOrWait(), and LWLockWaitForVar().

1026 {
1027  bool found = false;
1028  proclist_mutable_iter iter;
1029 
1030 #ifdef LWLOCK_STATS
1031  lwlock_stats *lwstats;
1032 
1033  lwstats = get_lwlock_stats_entry(lock);
1034 
1035  lwstats->dequeue_self_count++;
1036 #endif
1037 
1038  LWLockWaitListLock(lock);
1039 
1040  /*
1041  * Can't just remove ourselves from the list, but we need to iterate over
1042  * all entries as somebody else could have dequeued us.
1043  */
1044  proclist_foreach_modify(iter, &lock->waiters, lwWaitLink)
1045  {
1046  if (iter.cur == MyProc->pgprocno)
1047  {
1048  found = true;
1049  proclist_delete(&lock->waiters, iter.cur, lwWaitLink);
1050  break;
1051  }
1052  }
1053 
1054  if (proclist_is_empty(&lock->waiters) &&
1055  (pg_atomic_read_u32(&lock->state) & LW_FLAG_HAS_WAITERS) != 0)
1056  {
1058  }
1059 
1060  /* XXX: combine with fetch_and above? */
1061  LWLockWaitListUnlock(lock);
1062 
1063  /* clear waiting state again, nice for debugging */
1064  if (found)
1065  MyProc->lwWaiting = false;
1066  else
1067  {
1068  int extraWaits = 0;
1069 
1070  /*
1071  * Somebody else dequeued us and has or will wake us up. Deal with the
1072  * superfluous absorption of a wakeup.
1073  */
1074 
1075  /*
1076  * Reset releaseOk if somebody woke us before we removed ourselves -
1077  * they'll have set it to false.
1078  */
1080 
1081  /*
1082  * Now wait for the scheduled wakeup, otherwise our ->lwWaiting would
1083  * get reset at some inconvenient point later. Most of the time this
1084  * will immediately return.
1085  */
1086  for (;;)
1087  {
1089  if (!MyProc->lwWaiting)
1090  break;
1091  extraWaits++;
1092  }
1093 
1094  /*
1095  * Fix the process wait semaphore's count for any absorbed wakeups.
1096  */
1097  while (extraWaits-- > 0)
1099  }
1100 
1101 #ifdef LOCK_DEBUG
1102  {
1103  /* not waiting anymore */
1104  uint32 nwaiters PG_USED_FOR_ASSERTS_ONLY = pg_atomic_fetch_sub_u32(&lock->nwaiters, 1);
1105 
1106  Assert(nwaiters < MAX_BACKENDS);
1107  }
1108 #endif
1109 }
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
#define LW_FLAG_HAS_WAITERS
Definition: lwlock.c:99
PGPROC * MyProc
Definition: proc.c:67
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
pg_atomic_uint32 state
Definition: lwlock.h:35
#define proclist_delete(list, procno, link_member)
Definition: proclist.h:187
#define MAX_BACKENDS
Definition: postmaster.h:75
static uint32 pg_atomic_fetch_and_u32(volatile pg_atomic_uint32 *ptr, uint32 and_)
Definition: atomics.h:369
unsigned int uint32
Definition: c.h:314
#define Assert(condition)
Definition: c.h:688
static bool proclist_is_empty(proclist_head *list)
Definition: proclist.h:38
#define LW_FLAG_RELEASE_OK
Definition: lwlock.c:100
void PGSemaphoreLock(PGSemaphore sema)
Definition: posix_sema.c:303
static void LWLockWaitListLock(LWLock *lock)
Definition: lwlock.c:809
int pgprocno
Definition: proc.h:110
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:123
static uint32 pg_atomic_read_u32(volatile pg_atomic_uint32 *ptr)
Definition: atomics.h:252

◆ LWLockHeldByMe()

◆ LWLockHeldByMeInMode()

bool LWLockHeldByMeInMode ( LWLock l,
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

◆ LWLockQueueSelf()

static void LWLockQueueSelf ( LWLock lock,
LWLockMode  mode 
)
static

Definition at line 981 of file lwlock.c.

References elog, LW_FLAG_HAS_WAITERS, LW_WAIT_UNTIL_FREE, LWLockWaitListLock(), LWLockWaitListUnlock(), PGPROC::lwWaiting, PGPROC::lwWaitMode, LWLockHandle::mode, MyProc, PANIC, pg_atomic_fetch_add_u32(), pg_atomic_fetch_or_u32(), PGPROC::pgprocno, proclist_push_head, proclist_push_tail, LWLock::state, and LWLock::waiters.

Referenced by LWLockAcquire(), LWLockAcquireOrWait(), and LWLockWaitForVar().

982 {
983  /*
984  * If we don't have a PGPROC structure, there's no way to wait. This
985  * should never occur, since MyProc should only be null during shared
986  * memory initialization.
987  */
988  if (MyProc == NULL)
989  elog(PANIC, "cannot wait without a PGPROC structure");
990 
991  if (MyProc->lwWaiting)
992  elog(PANIC, "queueing for lock while waiting on another one");
993 
994  LWLockWaitListLock(lock);
995 
996  /* setting the flag is protected by the spinlock */
998 
999  MyProc->lwWaiting = true;
1000  MyProc->lwWaitMode = mode;
1001 
1002  /* LW_WAIT_UNTIL_FREE waiters are always at the front of the queue */
1003  if (mode == LW_WAIT_UNTIL_FREE)
1004  proclist_push_head(&lock->waiters, MyProc->pgprocno, lwWaitLink);
1005  else
1006  proclist_push_tail(&lock->waiters, MyProc->pgprocno, lwWaitLink);
1007 
1008  /* Can release the mutex now */
1009  LWLockWaitListUnlock(lock);
1010 
1011 #ifdef LOCK_DEBUG
1012  pg_atomic_fetch_add_u32(&lock->nwaiters, 1);
1013 #endif
1014 
1015 }
#define LW_FLAG_HAS_WAITERS
Definition: lwlock.c:99
PGPROC * MyProc
Definition: proc.c:67
proclist_head waiters
Definition: lwlock.h:36
bool lwWaiting
Definition: proc.h:127
static void LWLockWaitListUnlock(LWLock *lock)
Definition: lwlock.c:861
uint8 lwWaitMode
Definition: proc.h:128
pg_atomic_uint32 state
Definition: lwlock.h:35
#define PANIC
Definition: elog.h:53
#define proclist_push_head(list, procno, link_member)
Definition: proclist.h:189
static uint32 pg_atomic_fetch_add_u32(volatile pg_atomic_uint32 *ptr, int32 add_)
Definition: atomics.h:339
#define proclist_push_tail(list, procno, link_member)
Definition: proclist.h:191
static void LWLockWaitListLock(LWLock *lock)
Definition: lwlock.c:809
int pgprocno
Definition: proc.h:110
static uint32 pg_atomic_fetch_or_u32(volatile pg_atomic_uint32 *ptr, uint32 or_)
Definition: atomics.h:383
#define elog
Definition: elog.h:219

◆ 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 apw_init_shmem(), 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:688
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:314
static int num_held_lwlocks
Definition: lwlock.c:142
#define Assert(condition)
Definition: c.h:688
#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

◆ LWLockReportWaitEnd()

static void LWLockReportWaitEnd ( void  )
inlinestatic

Definition at line 703 of file lwlock.c.

References pgstat_report_wait_end().

Referenced by LWLockAcquire(), LWLockAcquireOrWait(), and LWLockWaitForVar().

704 {
706 }
static void pgstat_report_wait_end(void)
Definition: pgstat.h:1260

◆ LWLockReportWaitStart()

static void LWLockReportWaitStart ( LWLock lock)
inlinestatic

Definition at line 694 of file lwlock.c.

References PG_WAIT_LWLOCK, pgstat_report_wait_start(), and LWLock::tranche.

Referenced by LWLockAcquire(), LWLockAcquireOrWait(), and LWLockWaitForVar().

695 {
697 }
uint16 tranche
Definition: lwlock.h:34
static void pgstat_report_wait_start(uint32 wait_event_info)
Definition: pgstat.h:1236
#define PG_WAIT_LWLOCK
Definition: pgstat.h:737

◆ 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:422
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  val 
)

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:688
#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:314
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:688
#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:123
Definition: proc.h:95
#define LOG_LWDEBUG(a, b, c)
Definition: lwlock.c:228

◆ LWLockWaitListLock()

static void LWLockWaitListLock ( LWLock lock)
static

Definition at line 809 of file lwlock.c.

References SpinDelayStatus::delays, finish_spin_delay(), init_local_spin_delay, LW_FLAG_LOCKED, perform_spin_delay(), pg_atomic_fetch_or_u32(), pg_atomic_read_u32(), and LWLock::state.

Referenced by LWLockConflictsWithVar(), LWLockDequeueSelf(), LWLockQueueSelf(), LWLockReleaseClearVar(), LWLockUpdateVar(), and LWLockWakeup().

810 {
811  uint32 old_state;
812 #ifdef LWLOCK_STATS
813  lwlock_stats *lwstats;
814  uint32 delays = 0;
815 
816  lwstats = get_lwlock_stats_entry(lock);
817 #endif
818 
819  while (true)
820  {
821  /* always try once to acquire lock directly */
822  old_state = pg_atomic_fetch_or_u32(&lock->state, LW_FLAG_LOCKED);
823  if (!(old_state & LW_FLAG_LOCKED))
824  break; /* got lock */
825 
826  /* and then spin without atomic operations until lock is released */
827  {
828  SpinDelayStatus delayStatus;
829 
830  init_local_spin_delay(&delayStatus);
831 
832  while (old_state & LW_FLAG_LOCKED)
833  {
834  perform_spin_delay(&delayStatus);
835  old_state = pg_atomic_read_u32(&lock->state);
836  }
837 #ifdef LWLOCK_STATS
838  delays += delayStatus.delays;
839 #endif
840  finish_spin_delay(&delayStatus);
841  }
842 
843  /*
844  * Retry. The lock might obviously already be re-acquired by the time
845  * we're attempting to get it again.
846  */
847  }
848 
849 #ifdef LWLOCK_STATS
850  lwstats->spin_delay_count += delays;
851 #endif
852 }
#define init_local_spin_delay(status)
Definition: s_lock.h:1021
#define LW_FLAG_LOCKED
Definition: lwlock.c:101
pg_atomic_uint32 state
Definition: lwlock.h:35
void finish_spin_delay(SpinDelayStatus *status)
Definition: s_lock.c:175
unsigned int uint32
Definition: c.h:314
static uint32 pg_atomic_fetch_or_u32(volatile pg_atomic_uint32 *ptr, uint32 or_)
Definition: atomics.h:383
void perform_spin_delay(SpinDelayStatus *status)
Definition: s_lock.c:125
static uint32 pg_atomic_read_u32(volatile pg_atomic_uint32 *ptr)
Definition: atomics.h:252

◆ LWLockWaitListUnlock()

static void LWLockWaitListUnlock ( LWLock lock)
static

Definition at line 861 of file lwlock.c.

References Assert, LW_FLAG_LOCKED, pg_atomic_fetch_and_u32(), PG_USED_FOR_ASSERTS_ONLY, and LWLock::state.

Referenced by LWLockConflictsWithVar(), LWLockDequeueSelf(), LWLockQueueSelf(), LWLockReleaseClearVar(), and LWLockUpdateVar().

862 {
864 
865  old_state = pg_atomic_fetch_and_u32(&lock->state, ~LW_FLAG_LOCKED);
866 
867  Assert(old_state & LW_FLAG_LOCKED);
868 }
#define LW_FLAG_LOCKED
Definition: lwlock.c:101
pg_atomic_uint32 state
Definition: lwlock.h:35
static uint32 pg_atomic_fetch_and_u32(volatile pg_atomic_uint32 *ptr, uint32 and_)
Definition: atomics.h:369
unsigned int uint32
Definition: c.h:314
#define Assert(condition)
Definition: c.h:688
#define PG_USED_FOR_ASSERTS_ONLY
Definition: c.h:123

◆ LWLockWakeup()

static void LWLockWakeup ( LWLock lock)
static

Definition at line 874 of file lwlock.c.

References Assert, proclist_mutable_iter::cur, GetPGProcByNumber, LOG_LWDEBUG, LW_EXCLUSIVE, LW_FLAG_HAS_WAITERS, LW_FLAG_LOCKED, LW_FLAG_RELEASE_OK, LW_WAIT_UNTIL_FREE, LWLockWaitListLock(), PGPROC::lwWaiting, PGPROC::lwWaitMode, pg_atomic_compare_exchange_u32(), pg_atomic_read_u32(), pg_write_barrier, PGSemaphoreUnlock(), proclist_delete, proclist_foreach_modify, proclist_init(), proclist_is_empty(), proclist_push_tail, PGPROC::sem, LWLock::state, and LWLock::waiters.

Referenced by LWLockRelease().

875 {
876  bool new_release_ok;
877  bool wokeup_somebody = false;
878  proclist_head wakeup;
880 
881  proclist_init(&wakeup);
882 
883  new_release_ok = true;
884 
885  /* lock wait list while collecting backends to wake up */
886  LWLockWaitListLock(lock);
887 
888  proclist_foreach_modify(iter, &lock->waiters, lwWaitLink)
889  {
890  PGPROC *waiter = GetPGProcByNumber(iter.cur);
891 
892  if (wokeup_somebody && waiter->lwWaitMode == LW_EXCLUSIVE)
893  continue;
894 
895  proclist_delete(&lock->waiters, iter.cur, lwWaitLink);
896  proclist_push_tail(&wakeup, iter.cur, lwWaitLink);
897 
898  if (waiter->lwWaitMode != LW_WAIT_UNTIL_FREE)
899  {
900  /*
901  * Prevent additional wakeups until retryer gets to run. Backends
902  * that are just waiting for the lock to become free don't retry
903  * automatically.
904  */
905  new_release_ok = false;
906 
907  /*
908  * Don't wakeup (further) exclusive locks.
909  */
910  wokeup_somebody = true;
911  }
912 
913  /*
914  * Once we've woken up an exclusive lock, there's no point in waking
915  * up anybody else.
916  */
917  if (waiter->lwWaitMode == LW_EXCLUSIVE)
918  break;
919  }
920 
922 
923  /* unset required flags, and release lock, in one fell swoop */
924  {
925  uint32 old_state;
926  uint32 desired_state;
927 
928  old_state = pg_atomic_read_u32(&lock->state);
929  while (true)
930  {
931  desired_state = old_state;
932 
933  /* compute desired flags */
934 
935  if (new_release_ok)
936  desired_state |= LW_FLAG_RELEASE_OK;
937  else
938  desired_state &= ~LW_FLAG_RELEASE_OK;
939 
940  if (proclist_is_empty(&wakeup))
941  desired_state &= ~LW_FLAG_HAS_WAITERS;
942 
943  desired_state &= ~LW_FLAG_LOCKED; /* release lock */
944 
945  if (pg_atomic_compare_exchange_u32(&lock->state, &old_state,
946  desired_state))
947  break;
948  }
949  }
950 
951  /* Awaken any waiters I removed from the queue. */
952  proclist_foreach_modify(iter, &wakeup, lwWaitLink)
953  {
954  PGPROC *waiter = GetPGProcByNumber(iter.cur);
955 
956  LOG_LWDEBUG("LWLockRelease", lock, "release waiter");
957  proclist_delete(&wakeup, iter.cur, lwWaitLink);
958 
959  /*
960  * Guarantee that lwWaiting being unset only becomes visible once the
961  * unlink from the link has completed. Otherwise the target backend
962  * could be woken up for other reason and enqueue for a new lock - if
963  * that happens before the list unlink happens, the list would end up
964  * being corrupted.
965  *
966  * The barrier pairs with the LWLockWaitListLock() when enqueuing for
967  * another lock.
968  */
970  waiter->lwWaiting = false;
971  PGSemaphoreUnlock(waiter->sem);
972  }
973 }
#define GetPGProcByNumber(n)
Definition: proc.h:277
#define LW_FLAG_LOCKED
Definition: lwlock.c:101
void PGSemaphoreUnlock(PGSemaphore sema)
Definition: posix_sema.c:323
#define LW_FLAG_HAS_WAITERS
Definition: lwlock.c:99
static bool pg_atomic_compare_exchange_u32(volatile pg_atomic_uint32 *ptr, uint32 *expected, uint32 newval)
Definition: atomics.h:322
proclist_head waiters
Definition: lwlock.h:36
bool lwWaiting
Definition: proc.h:127
#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
unsigned int uint32
Definition: c.h:314
#define Assert(condition)
Definition: c.h:688
static bool proclist_is_empty(proclist_head *list)
Definition: proclist.h:38
#define LW_FLAG_RELEASE_OK
Definition: lwlock.c:100
#define proclist_push_tail(list, procno, link_member)
Definition: proclist.h:191
static void LWLockWaitListLock(LWLock *lock)
Definition: lwlock.c:809
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
static uint32 pg_atomic_read_u32(volatile pg_atomic_uint32 *ptr)
Definition: atomics.h:252
#define LOG_LWDEBUG(a, b, c)
Definition: lwlock.c:228

◆ NumLWLocksByNamedTranches()

static int NumLWLocksByNamedTranches ( void  )
static

Definition at line 334 of file lwlock.c.

References i, and NamedLWLockTrancheRequests.

Referenced by InitializeLWLocks(), and LWLockShmemSize().

335 {
336  int numLocks = 0;
337  int i;
338 
339  for (i = 0; i < NamedLWLockTrancheRequests; i++)
340  numLocks += NamedLWLockTrancheRequestArray[i].num_lwlocks;
341 
342  return numLocks;
343 }
int NamedLWLockTrancheRequests
Definition: lwlock.c:154
NamedLWLockTrancheRequest * NamedLWLockTrancheRequestArray
Definition: lwlock.c:152
int i

◆ RegisterLWLockTranches()

static void RegisterLWLockTranches ( void  )
static

Definition at line 491 of file lwlock.c.

References Assert, i, LWLockRegisterTranche(), LWLockTrancheArray, LWLockTranchesAllocated, LWTRANCHE_BUFFER_MAPPING, LWTRANCHE_FIRST_USER_DEFINED, LWTRANCHE_LOCK_MANAGER, LWTRANCHE_PARALLEL_APPEND, LWTRANCHE_PARALLEL_QUERY_DSA, LWTRANCHE_PREDICATE_LOCK_MANAGER, LWTRANCHE_SESSION_DSA, LWTRANCHE_SESSION_RECORD_TABLE, LWTRANCHE_SESSION_TYPMOD_TABLE, LWTRANCHE_SHARED_TUPLESTORE, LWTRANCHE_TBM, MainLWLockNames, MemoryContextAllocZero(), NamedLWLockTrancheRequests, and TopMemoryContext.

Referenced by CreateLWLocks().

492 {
493  int i;
494 
495  if (LWLockTrancheArray == NULL)
496  {
498  LWLockTrancheArray = (const char **)
500  LWLockTranchesAllocated * sizeof(char *));
502  }
503 
504  for (i = 0; i < NUM_INDIVIDUAL_LWLOCKS; ++i)
506 
510  "predicate_lock_manager");
512  "parallel_query_dsa");
514  "session_dsa");
516  "session_record_table");
518  "session_typmod_table");
520  "shared_tuplestore");
523 
524  /* Register named tranches. */
525  for (i = 0; i < NamedLWLockTrancheRequests; i++)
527  NamedLWLockTrancheArray[i].trancheName);
528 }
NamedLWLockTranche * NamedLWLockTrancheArray
Definition: lwlock.c:156
void LWLockRegisterTranche(int tranche_id, const char *tranche_name)
Definition: lwlock.c:601
static int LWLockTranchesAllocated
Definition: lwlock.c:115
int NamedLWLockTrancheRequests
Definition: lwlock.c:154
static const char ** LWLockTrancheArray
Definition: lwlock.c:114
MemoryContext TopMemoryContext
Definition: mcxt.c:43
void * MemoryContextAllocZero(MemoryContext context, Size size)
Definition: mcxt.c:728
#define Assert(condition)
Definition: c.h:688
char * MainLWLockNames[]
int i

◆ 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:688
#define StrNCpy(dst, src, len)
Definition: c.h:870
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

◆ held_lwlocks

LWLockHandle held_lwlocks[MAX_SIMUL_LWLOCKS]
static

Definition at line 143 of file lwlock.c.

◆ lock_named_request_allowed

bool lock_named_request_allowed = true
static

Definition at line 158 of file lwlock.c.

Referenced by LWLockShmemSize(), and RequestNamedLWLockTranche().

◆ LWLockTrancheArray

const char** LWLockTrancheArray = NULL
static

Definition at line 114 of file lwlock.c.

Referenced by GetLWLockIdentifier(), LWLockRegisterTranche(), and RegisterLWLockTranches().

◆ LWLockTranchesAllocated

int LWLockTranchesAllocated = 0
static

Definition at line 115 of file lwlock.c.

Referenced by GetLWLockIdentifier(), LWLockRegisterTranche(), and RegisterLWLockTranches().

◆ MainLWLockArray

LWLockPadded* MainLWLockArray = NULL

Definition at line 125 of file lwlock.c.

Referenced by PostmasterMarkPIDForWorkerNotify().

◆ NamedLWLockTrancheArray

NamedLWLockTranche* NamedLWLockTrancheArray = NULL

Definition at line 156 of file lwlock.c.

Referenced by PostmasterMarkPIDForWorkerNotify().

◆ NamedLWLockTrancheRequestArray

NamedLWLockTrancheRequest* NamedLWLockTrancheRequestArray = NULL

Definition at line 152 of file lwlock.c.

◆ NamedLWLockTrancheRequests

◆ NamedLWLockTrancheRequestsAllocated

int NamedLWLockTrancheRequestsAllocated = 0
static

Definition at line 153 of file lwlock.c.

Referenced by RequestNamedLWLockTranche().

◆ num_held_lwlocks

◆ ShmemLock