PostgreSQL Source Code  git master
lwlock.c File Reference
#include "postgres.h"
#include "miscadmin.h"
#include "pg_trace.h"
#include "pgstat.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

typedef struct LWLockHandle LWLockHandle

◆ NamedLWLockTrancheRequest

Function Documentation

◆ CreateLWLocks()

void CreateLWLocks ( void  )

Definition at line 382 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().

383 {
385  "MAX_BACKENDS too big for lwlock.c");
386 
388  sizeof(LWLock) <= LWLOCK_PADDED_SIZE,
389  "Miscalculated LWLock padding");
390 
391  if (!IsUnderPostmaster)
392  {
393  Size spaceLocks = LWLockShmemSize();
394  int *LWLockCounter;
395  char *ptr;
396 
397  /* Allocate space */
398  ptr = (char *) ShmemAlloc(spaceLocks);
399 
400  /* Leave room for dynamic allocation of tranches */
401  ptr += sizeof(int);
402 
403  /* Ensure desired alignment of LWLock array */
404  ptr += LWLOCK_PADDED_SIZE - ((uintptr_t) ptr) % LWLOCK_PADDED_SIZE;
405 
406  MainLWLockArray = (LWLockPadded *) ptr;
407 
408  /*
409  * Initialize the dynamic-allocation counter for tranches, which is
410  * stored just before the first LWLock.
411  */
412  LWLockCounter = (int *) ((char *) MainLWLockArray - sizeof(int));
413  *LWLockCounter = LWTRANCHE_FIRST_USER_DEFINED;
414 
415  /* Initialize all LWLocks */
417  }
418 
419  /* Register all LWLock tranches */
421 }
Definition: lwlock.h:32
void * ShmemAlloc(Size size)
Definition: shmem.c:161
Size LWLockShmemSize(void)
Definition: lwlock.c:350
static void RegisterLWLockTranches(void)
Definition: lwlock.c:492
#define StaticAssertStmt(condition, errmessage)
Definition: c.h:852
#define LWLOCK_MINIMAL_SIZE
Definition: lwlock.h:74
#define MAX_BACKENDS
Definition: postmaster.h:75
bool IsUnderPostmaster
Definition: globals.c:109
unsigned int uint32
Definition: c.h:367
static void InitializeLWLocks(void)
Definition: lwlock.c:427
size_t Size
Definition: c.h:466
#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 715 of file lwlock.c.

References Assert, LWLockTrancheArray, LWLockTranchesAllocated, and PG_WAIT_LWLOCK.

Referenced by pgstat_get_wait_event().

716 {
717  Assert(classId == PG_WAIT_LWLOCK);
718 
719  /*
720  * It is quite possible that user has registered tranche in one of the
721  * backends (e.g. by allocating lwlocks in dynamic shared memory) but not
722  * all of them, so we can't assume the tranche is registered here.
723  */
724  if (eventId >= LWLockTranchesAllocated ||
725  LWLockTrancheArray[eventId] == NULL)
726  return "extension";
727 
728  return LWLockTrancheArray[eventId];
729 }
static int LWLockTranchesAllocated
Definition: lwlock.c:115
static const char ** LWLockTrancheArray
Definition: lwlock.c:114
#define Assert(condition)
Definition: c.h:738
#define PG_WAIT_LWLOCK
Definition: pgstat.h:737

◆ GetNamedLWLockTranche()

LWLockPadded* GetNamedLWLockTranche ( const char *  tranche_name)

Definition at line 553 of file lwlock.c.

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

Referenced by pgss_shmem_startup().

554 {
555  int lock_pos;
556  int i;
557 
558  /*
559  * Obtain the position of base address of LWLock belonging to requested
560  * tranche_name in MainLWLockArray. LWLocks for named tranches are placed
561  * in MainLWLockArray after fixed locks.
562  */
563  lock_pos = NUM_FIXED_LWLOCKS;
564  for (i = 0; i < NamedLWLockTrancheRequests; i++)
565  {
566  if (strcmp(NamedLWLockTrancheRequestArray[i].tranche_name,
567  tranche_name) == 0)
568  return &MainLWLockArray[lock_pos];
569 
571  }
572 
573  if (i >= NamedLWLockTrancheRequests)
574  elog(ERROR, "requested tranche is not registered");
575 
576  /* just to keep compiler quiet */
577  return NULL;
578 }
#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
#define elog(elevel,...)
Definition: elog.h:214
int i
LWLockPadded * MainLWLockArray
Definition: lwlock.c:125

◆ InitializeLWLocks()

static void InitializeLWLocks ( void  )
static

Definition at line 427 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().

428 {
429  int numNamedLocks = NumLWLocksByNamedTranches();
430  int id;
431  int i;
432  int j;
433  LWLockPadded *lock;
434 
435  /* Initialize all individual LWLocks in main array */
436  for (id = 0, lock = MainLWLockArray; id < NUM_INDIVIDUAL_LWLOCKS; id++, lock++)
437  LWLockInitialize(&lock->lock, id);
438 
439  /* Initialize buffer mapping LWLocks in main array */
440  lock = MainLWLockArray + NUM_INDIVIDUAL_LWLOCKS;
441  for (id = 0; id < NUM_BUFFER_PARTITIONS; id++, lock++)
443 
444  /* Initialize lmgrs' LWLocks in main array */
445  lock = MainLWLockArray + NUM_INDIVIDUAL_LWLOCKS + NUM_BUFFER_PARTITIONS;
446  for (id = 0; id < NUM_LOCK_PARTITIONS; id++, lock++)
448 
449  /* Initialize predicate lmgrs' LWLocks in main array */
450  lock = MainLWLockArray + NUM_INDIVIDUAL_LWLOCKS +
451  NUM_BUFFER_PARTITIONS + NUM_LOCK_PARTITIONS;
452  for (id = 0; id < NUM_PREDICATELOCK_PARTITIONS; id++, lock++)
454 
455  /* Initialize named tranches. */
457  {
458  char *trancheNames;
459 
461  &MainLWLockArray[NUM_FIXED_LWLOCKS + numNamedLocks];
462 
463  trancheNames = (char *) NamedLWLockTrancheArray +
466 
467  for (i = 0; i < NamedLWLockTrancheRequests; i++)
468  {
469  NamedLWLockTrancheRequest *request;
470  NamedLWLockTranche *tranche;
471  char *name;
472 
473  request = &NamedLWLockTrancheRequestArray[i];
474  tranche = &NamedLWLockTrancheArray[i];
475 
476  name = trancheNames;
477  trancheNames += strlen(request->tranche_name) + 1;
478  strcpy(name, request->tranche_name);
479  tranche->trancheId = LWLockNewTrancheId();
480  tranche->trancheName = name;
481 
482  for (j = 0; j < request->num_lwlocks; j++, lock++)
483  LWLockInitialize(&lock->lock, tranche->trancheId);
484  }
485  }
486 }
int LWLockNewTrancheId(void)
Definition: lwlock.c:584
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:679
LWLock lock
Definition: lwlock.h:79
static int NumLWLocksByNamedTranches(void)
Definition: lwlock.c:335
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 537 of file lwlock.c.

Referenced by InitProcess().

538 {
539 #ifdef LWLOCK_STATS
540  init_lwlock_stats();
541 #endif
542 }

◆ LWLockAcquire()

bool LWLockAcquire ( LWLock lock,
LWLockMode  mode 
)

Definition at line 1123 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(), AbsorbSyncRequests(), ActivateCommitTs(), AdvanceNextFullTransactionIdPastXid(), 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(), copy_replication_slot(), 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(), ForwardSyncRequest(), 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(), HandleAutoVacLauncherInterrupts(), 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_get_replication_slots(), pg_get_shmem_allocations(), 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(), ProcKill(), ProcSleep(), ReadBuffer_common(), ReadMultiXactCounts(), ReadNextFullTransactionId(), ReadNextMultiXactId(), ReadRecord(), 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(), TerminateOtherDBBackends(), 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(), XidCacheRemoveRunningXids(), xlog_redo(), and XLogBackgroundFlush().

1124 {
1125  PGPROC *proc = MyProc;
1126  bool result = true;
1127  int extraWaits = 0;
1128 #ifdef LWLOCK_STATS
1129  lwlock_stats *lwstats;
1130 
1131  lwstats = get_lwlock_stats_entry(lock);
1132 #endif
1133 
1135 
1136  PRINT_LWDEBUG("LWLockAcquire", lock, mode);
1137 
1138 #ifdef LWLOCK_STATS
1139  /* Count lock acquisition attempts */
1140  if (mode == LW_EXCLUSIVE)
1141  lwstats->ex_acquire_count++;
1142  else
1143  lwstats->sh_acquire_count++;
1144 #endif /* LWLOCK_STATS */
1145 
1146  /*
1147  * We can't wait if we haven't got a PGPROC. This should only occur
1148  * during bootstrap or shared memory initialization. Put an Assert here
1149  * to catch unsafe coding practices.
1150  */
1151  Assert(!(proc == NULL && IsUnderPostmaster));
1152 
1153  /* Ensure we will have room to remember the lock */
1155  elog(ERROR, "too many LWLocks taken");
1156 
1157  /*
1158  * Lock out cancel/die interrupts until we exit the code section protected
1159  * by the LWLock. This ensures that interrupts will not interfere with
1160  * manipulations of data structures in shared memory.
1161  */
1162  HOLD_INTERRUPTS();
1163 
1164  /*
1165  * Loop here to try to acquire lock after each time we are signaled by
1166  * LWLockRelease.
1167  *
1168  * NOTE: it might seem better to have LWLockRelease actually grant us the
1169  * lock, rather than retrying and possibly having to go back to sleep. But
1170  * in practice that is no good because it means a process swap for every
1171  * lock acquisition when two or more processes are contending for the same
1172  * lock. Since LWLocks are normally used to protect not-very-long
1173  * sections of computation, a process needs to be able to acquire and
1174  * release the same lock many times during a single CPU time slice, even
1175  * in the presence of contention. The efficiency of being able to do that
1176  * outweighs the inefficiency of sometimes wasting a process dispatch
1177  * cycle because the lock is not free when a released waiter finally gets
1178  * to run. See pgsql-hackers archives for 29-Dec-01.
1179  */
1180  for (;;)
1181  {
1182  bool mustwait;
1183 
1184  /*
1185  * Try to grab the lock the first time, we're not in the waitqueue
1186  * yet/anymore.
1187  */
1188  mustwait = LWLockAttemptLock(lock, mode);
1189 
1190  if (!mustwait)
1191  {
1192  LOG_LWDEBUG("LWLockAcquire", lock, "immediately acquired lock");
1193  break; /* got the lock */
1194  }
1195 
1196  /*
1197  * Ok, at this point we couldn't grab the lock on the first try. We
1198  * cannot simply queue ourselves to the end of the list and wait to be
1199  * woken up because by now the lock could long have been released.
1200  * Instead add us to the queue and try to grab the lock again. If we
1201  * succeed we need to revert the queuing and be happy, otherwise we
1202  * recheck the lock. If we still couldn't grab it, we know that the
1203  * other locker will see our queue entries when releasing since they
1204  * existed before we checked for the lock.
1205  */
1206 
1207  /* add to the queue */
1208  LWLockQueueSelf(lock, mode);
1209 
1210  /* we're now guaranteed to be woken up if necessary */
1211  mustwait = LWLockAttemptLock(lock, mode);
1212 
1213  /* ok, grabbed the lock the second time round, need to undo queueing */
1214  if (!mustwait)
1215  {
1216  LOG_LWDEBUG("LWLockAcquire", lock, "acquired, undoing queue");
1217 
1218  LWLockDequeueSelf(lock);
1219  break;
1220  }
1221 
1222  /*
1223  * Wait until awakened.
1224  *
1225  * Since we share the process wait semaphore with the regular lock
1226  * manager and ProcWaitForSignal, and we may need to acquire an LWLock
1227  * while one of those is pending, it is possible that we get awakened
1228  * for a reason other than being signaled by LWLockRelease. If so,
1229  * loop back and wait again. Once we've gotten the LWLock,
1230  * re-increment the sema by the number of additional signals received,
1231  * so that the lock manager or signal manager will see the received
1232  * signal when it next waits.
1233  */
1234  LOG_LWDEBUG("LWLockAcquire", lock, "waiting");
1235 
1236 #ifdef LWLOCK_STATS
1237  lwstats->block_count++;
1238 #endif
1239 
1240  LWLockReportWaitStart(lock);
1241  TRACE_POSTGRESQL_LWLOCK_WAIT_START(T_NAME(lock), mode);
1242 
1243  for (;;)
1244  {
1245  PGSemaphoreLock(proc->sem);
1246  if (!proc->lwWaiting)
1247  break;
1248  extraWaits++;
1249  }
1250 
1251  /* Retrying, allow LWLockRelease to release waiters again. */
1253 
1254 #ifdef LOCK_DEBUG
1255  {
1256  /* not waiting anymore */
1257  uint32 nwaiters PG_USED_FOR_ASSERTS_ONLY = pg_atomic_fetch_sub_u32(&lock->nwaiters, 1);
1258 
1259  Assert(nwaiters < MAX_BACKENDS);
1260  }
1261 #endif
1262 
1263  TRACE_POSTGRESQL_LWLOCK_WAIT_DONE(T_NAME(lock), mode);
1265 
1266  LOG_LWDEBUG("LWLockAcquire", lock, "awakened");
1267 
1268  /* Now loop back and try to acquire lock again. */
1269  result = false;
1270  }
1271 
1272  TRACE_POSTGRESQL_LWLOCK_ACQUIRE(T_NAME(lock), mode);
1273 
1274  /* Add lock to list of locks held by this backend */
1277 
1278  /*
1279  * Fix the process wait semaphore's count for any absorbed wakeups.
1280  */
1281  while (extraWaits-- > 0)
1282  PGSemaphoreUnlock(proc->sem);
1283 
1284  return result;
1285 }
#define T_NAME(lock)
Definition: lwlock.c:117
static PgChecksumMode mode
Definition: pg_checksums.c:61
static uint32 pg_atomic_fetch_sub_u32(volatile pg_atomic_uint32 *ptr, int32 sub_)
Definition: atomics.h:343
static bool LWLockAttemptLock(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:741
void PGSemaphoreUnlock(PGSemaphore sema)
Definition: posix_sema.c:340
PGPROC * MyProc
Definition: proc.c:67
bool lwWaiting
Definition: proc.h:130
#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:109
static void LWLockReportWaitEnd(void)
Definition: lwlock.c:706
unsigned int uint32
Definition: c.h:367
static void LWLockDequeueSelf(LWLock *lock)
Definition: lwlock.c:1028
#define AssertArg(condition)
Definition: c.h:740
static void LWLockReportWaitStart(LWLock *lock)
Definition: lwlock.c:697
static void LWLockQueueSelf(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:984
static int num_held_lwlocks
Definition: lwlock.c:142
#define Assert(condition)
Definition: c.h:738
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:320
#define HOLD_INTERRUPTS()
Definition: miscadmin.h:116
#define elog(elevel,...)
Definition: elog.h:214
static uint32 pg_atomic_fetch_or_u32(volatile pg_atomic_uint32 *ptr, uint32 or_)
Definition: atomics.h:372
PGSemaphore sem
Definition: proc.h:101
Definition: proc.h:95
#define PG_USED_FOR_ASSERTS_ONLY
Definition: c.h:121
#define LOG_LWDEBUG(a, b, c)
Definition: lwlock.c:228

◆ LWLockAcquireOrWait()

bool LWLockAcquireOrWait ( LWLock lock,
LWLockMode  mode 
)

Definition at line 1350 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().

1351 {
1352  PGPROC *proc = MyProc;
1353  bool mustwait;
1354  int extraWaits = 0;
1355 #ifdef LWLOCK_STATS
1356  lwlock_stats *lwstats;
1357 
1358  lwstats = get_lwlock_stats_entry(lock);
1359 #endif
1360 
1362 
1363  PRINT_LWDEBUG("LWLockAcquireOrWait", lock, mode);
1364 
1365  /* Ensure we will have room to remember the lock */
1367  elog(ERROR, "too many LWLocks taken");
1368 
1369  /*
1370  * Lock out cancel/die interrupts until we exit the code section protected
1371  * by the LWLock. This ensures that interrupts will not interfere with
1372  * manipulations of data structures in shared memory.
1373  */
1374  HOLD_INTERRUPTS();
1375 
1376  /*
1377  * NB: We're using nearly the same twice-in-a-row lock acquisition
1378  * protocol as LWLockAcquire(). Check its comments for details.
1379  */
1380  mustwait = LWLockAttemptLock(lock, mode);
1381 
1382  if (mustwait)
1383  {
1385 
1386  mustwait = LWLockAttemptLock(lock, mode);
1387 
1388  if (mustwait)
1389  {
1390  /*
1391  * Wait until awakened. Like in LWLockAcquire, be prepared for
1392  * bogus wakeups, because we share the semaphore with
1393  * ProcWaitForSignal.
1394  */
1395  LOG_LWDEBUG("LWLockAcquireOrWait", lock, "waiting");
1396 
1397 #ifdef LWLOCK_STATS
1398  lwstats->block_count++;
1399 #endif
1400 
1401  LWLockReportWaitStart(lock);
1402  TRACE_POSTGRESQL_LWLOCK_WAIT_START(T_NAME(lock), mode);
1403 
1404  for (;;)
1405  {
1406  PGSemaphoreLock(proc->sem);
1407  if (!proc->lwWaiting)
1408  break;
1409  extraWaits++;
1410  }
1411 
1412 #ifdef LOCK_DEBUG
1413  {
1414  /* not waiting anymore */
1415  uint32 nwaiters PG_USED_FOR_ASSERTS_ONLY = pg_atomic_fetch_sub_u32(&lock->nwaiters, 1);
1416 
1417  Assert(nwaiters < MAX_BACKENDS);
1418  }
1419 #endif
1420  TRACE_POSTGRESQL_LWLOCK_WAIT_DONE(T_NAME(lock), mode);
1422 
1423  LOG_LWDEBUG("LWLockAcquireOrWait", lock, "awakened");
1424  }
1425  else
1426  {
1427  LOG_LWDEBUG("LWLockAcquireOrWait", lock, "acquired, undoing queue");
1428 
1429  /*
1430  * Got lock in the second attempt, undo queueing. We need to treat
1431  * this as having successfully acquired the lock, otherwise we'd
1432  * not necessarily wake up people we've prevented from acquiring
1433  * the lock.
1434  */
1435  LWLockDequeueSelf(lock);
1436  }
1437  }
1438 
1439  /*
1440  * Fix the process wait semaphore's count for any absorbed wakeups.
1441  */
1442  while (extraWaits-- > 0)
1443  PGSemaphoreUnlock(proc->sem);
1444 
1445  if (mustwait)
1446  {
1447  /* Failed to get lock, so release interrupt holdoff */
1449  LOG_LWDEBUG("LWLockAcquireOrWait", lock, "failed");
1450  TRACE_POSTGRESQL_LWLOCK_ACQUIRE_OR_WAIT_FAIL(T_NAME(lock), mode);
1451  }
1452  else
1453  {
1454  LOG_LWDEBUG("LWLockAcquireOrWait", lock, "succeeded");
1455  /* Add lock to list of locks held by this backend */
1458  TRACE_POSTGRESQL_LWLOCK_ACQUIRE_OR_WAIT(T_NAME(lock), mode);
1459  }
1460 
1461  return !mustwait;
1462 }
#define T_NAME(lock)
Definition: lwlock.c:117
static PgChecksumMode mode
Definition: pg_checksums.c:61
static uint32 pg_atomic_fetch_sub_u32(volatile pg_atomic_uint32 *ptr, int32 sub_)
Definition: atomics.h:343
static bool LWLockAttemptLock(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:741
void PGSemaphoreUnlock(PGSemaphore sema)
Definition: posix_sema.c:340
PGPROC * MyProc
Definition: proc.c:67
bool lwWaiting
Definition: proc.h:130
#define MAX_SIMUL_LWLOCKS
Definition: lwlock.c:133
#define RESUME_INTERRUPTS()
Definition: miscadmin.h:118
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:706
unsigned int uint32
Definition: c.h:367
static void LWLockDequeueSelf(LWLock *lock)
Definition: lwlock.c:1028
static void LWLockReportWaitStart(LWLock *lock)
Definition: lwlock.c:697
static void LWLockQueueSelf(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:984
static int num_held_lwlocks
Definition: lwlock.c:142
#define Assert(condition)
Definition: c.h:738
LWLock * lock
Definition: lwlock.c:138
#define PRINT_LWDEBUG(a, b, c)
Definition: lwlock.c:227
void PGSemaphoreLock(PGSemaphore sema)
Definition: posix_sema.c:320
#define HOLD_INTERRUPTS()
Definition: miscadmin.h:116
#define elog(elevel,...)
Definition: elog.h:214
PGSemaphore sem
Definition: proc.h:101
Definition: proc.h:95
#define PG_USED_FOR_ASSERTS_ONLY
Definition: c.h:121
#define LOG_LWDEBUG(a, b, c)
Definition: lwlock.c:228

◆ LWLockAttemptLock()

static bool LWLockAttemptLock ( LWLock lock,
LWLockMode  mode 
)
static

Definition at line 741 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().

742 {
743  uint32 old_state;
744 
746 
747  /*
748  * Read once outside the loop, later iterations will get the newer value
749  * via compare & exchange.
750  */
751  old_state = pg_atomic_read_u32(&lock->state);
752 
753  /* loop until we've determined whether we could acquire the lock or not */
754  while (true)
755  {
756  uint32 desired_state;
757  bool lock_free;
758 
759  desired_state = old_state;
760 
761  if (mode == LW_EXCLUSIVE)
762  {
763  lock_free = (old_state & LW_LOCK_MASK) == 0;
764  if (lock_free)
765  desired_state += LW_VAL_EXCLUSIVE;
766  }
767  else
768  {
769  lock_free = (old_state & LW_VAL_EXCLUSIVE) == 0;
770  if (lock_free)
771  desired_state += LW_VAL_SHARED;
772  }
773 
774  /*
775  * Attempt to swap in the state we are expecting. If we didn't see
776  * lock to be free, that's just the old value. If we saw it as free,
777  * we'll attempt to mark it acquired. The reason that we always swap
778  * in the value is that this doubles as a memory barrier. We could try
779  * to be smarter and only swap in values if we saw the lock as free,
780  * but benchmark haven't shown it as beneficial so far.
781  *
782  * Retry if the value changed since we last looked at it.
783  */
785  &old_state, desired_state))
786  {
787  if (lock_free)
788  {
789  /* Great! Got the lock. */
790 #ifdef LOCK_DEBUG
791  if (mode == LW_EXCLUSIVE)
792  lock->owner = MyProc;
793 #endif
794  return false;
795  }
796  else
797  return true; /* somebody else has the lock */
798  }
799  }
800  pg_unreachable();
801 }
static PgChecksumMode mode
Definition: pg_checksums.c:61
#define pg_unreachable()
Definition: c.h:191
static bool pg_atomic_compare_exchange_u32(volatile pg_atomic_uint32 *ptr, uint32 *expected, uint32 newval)
Definition: atomics.h:311
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:367
#define AssertArg(condition)
Definition: c.h:740
#define LW_VAL_EXCLUSIVE
Definition: lwlock.c:103
static uint32 pg_atomic_read_u32(volatile pg_atomic_uint32 *ptr)
Definition: atomics.h:241

◆ LWLockConditionalAcquire()

bool LWLockConditionalAcquire ( LWLock lock,
LWLockMode  mode 
)

Definition at line 1295 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().

1296 {
1297  bool mustwait;
1298 
1300 
1301  PRINT_LWDEBUG("LWLockConditionalAcquire", lock, mode);
1302 
1303  /* Ensure we will have room to remember the lock */
1305  elog(ERROR, "too many LWLocks taken");
1306 
1307  /*
1308  * Lock out cancel/die interrupts until we exit the code section protected
1309  * by the LWLock. This ensures that interrupts will not interfere with
1310  * manipulations of data structures in shared memory.
1311  */
1312  HOLD_INTERRUPTS();
1313 
1314  /* Check for the lock */
1315  mustwait = LWLockAttemptLock(lock, mode);
1316 
1317  if (mustwait)
1318  {
1319  /* Failed to get lock, so release interrupt holdoff */
1321 
1322  LOG_LWDEBUG("LWLockConditionalAcquire", lock, "failed");
1323  TRACE_POSTGRESQL_LWLOCK_CONDACQUIRE_FAIL(T_NAME(lock), mode);
1324  }
1325  else
1326  {
1327  /* Add lock to list of locks held by this backend */
1330  TRACE_POSTGRESQL_LWLOCK_CONDACQUIRE(T_NAME(lock), mode);
1331  }
1332  return !mustwait;
1333 }
#define T_NAME(lock)
Definition: lwlock.c:117
static PgChecksumMode mode
Definition: pg_checksums.c:61
static bool LWLockAttemptLock(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:741
#define MAX_SIMUL_LWLOCKS
Definition: lwlock.c:133
#define RESUME_INTERRUPTS()
Definition: miscadmin.h:118
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:740
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:116
#define elog(elevel,...)
Definition: elog.h:214
#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 1474 of file lwlock.c.

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

Referenced by LWLockWaitForVar().

1477 {
1478  bool mustwait;
1479  uint64 value;
1480 
1481  /*
1482  * Test first to see if it the slot is free right now.
1483  *
1484  * XXX: the caller uses a spinlock before this, so we don't need a memory
1485  * barrier here as far as the current usage is concerned. But that might
1486  * not be safe in general.
1487  */
1488  mustwait = (pg_atomic_read_u32(&lock->state) & LW_VAL_EXCLUSIVE) != 0;
1489 
1490  if (!mustwait)
1491  {
1492  *result = true;
1493  return false;
1494  }
1495 
1496  *result = false;
1497 
1498  /*
1499  * Read value using the lwlock's wait list lock, as we can't generally
1500  * rely on atomic 64 bit reads/stores. TODO: On platforms with a way to
1501  * do atomic 64 bit reads/writes the spinlock should be optimized away.
1502  */
1503  LWLockWaitListLock(lock);
1504  value = *valptr;
1505  LWLockWaitListUnlock(lock);
1506 
1507  if (value != oldval)
1508  {
1509  mustwait = false;
1510  *newval = value;
1511  }
1512  else
1513  {
1514  mustwait = true;
1515  }
1516 
1517  return mustwait;
1518 }
static void LWLockWaitListUnlock(LWLock *lock)
Definition: lwlock.c:864
pg_atomic_uint32 state
Definition: lwlock.h:35
static struct @143 value
#define newval
static void LWLockWaitListLock(LWLock *lock)
Definition: lwlock.c:812
#define LW_VAL_EXCLUSIVE
Definition: lwlock.c:103
static uint32 pg_atomic_read_u32(volatile pg_atomic_uint32 *ptr)
Definition: atomics.h:241

◆ LWLockDequeueSelf()

static void LWLockDequeueSelf ( LWLock lock)
static

Definition at line 1028 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().

1029 {
1030  bool found = false;
1031  proclist_mutable_iter iter;
1032 
1033 #ifdef LWLOCK_STATS
1034  lwlock_stats *lwstats;
1035 
1036  lwstats = get_lwlock_stats_entry(lock);
1037 
1038  lwstats->dequeue_self_count++;
1039 #endif
1040 
1041  LWLockWaitListLock(lock);
1042 
1043  /*
1044  * Can't just remove ourselves from the list, but we need to iterate over
1045  * all entries as somebody else could have dequeued us.
1046  */
1047  proclist_foreach_modify(iter, &lock->waiters, lwWaitLink)
1048  {
1049  if (iter.cur == MyProc->pgprocno)
1050  {
1051  found = true;
1052  proclist_delete(&lock->waiters, iter.cur, lwWaitLink);
1053  break;
1054  }
1055  }
1056 
1057  if (proclist_is_empty(&lock->waiters) &&
1058  (pg_atomic_read_u32(&lock->state) & LW_FLAG_HAS_WAITERS) != 0)
1059  {
1061  }
1062 
1063  /* XXX: combine with fetch_and above? */
1064  LWLockWaitListUnlock(lock);
1065 
1066  /* clear waiting state again, nice for debugging */
1067  if (found)
1068  MyProc->lwWaiting = false;
1069  else
1070  {
1071  int extraWaits = 0;
1072 
1073  /*
1074  * Somebody else dequeued us and has or will wake us up. Deal with the
1075  * superfluous absorption of a wakeup.
1076  */
1077 
1078  /*
1079  * Reset RELEASE_OK flag if somebody woke us before we removed
1080  * ourselves - they'll have set it to false.
1081  */
1083 
1084  /*
1085  * Now wait for the scheduled wakeup, otherwise our ->lwWaiting would
1086  * get reset at some inconvenient point later. Most of the time this
1087  * will immediately return.
1088  */
1089  for (;;)
1090  {
1092  if (!MyProc->lwWaiting)
1093  break;
1094  extraWaits++;
1095  }
1096 
1097  /*
1098  * Fix the process wait semaphore's count for any absorbed wakeups.
1099  */
1100  while (extraWaits-- > 0)
1102  }
1103 
1104 #ifdef LOCK_DEBUG
1105  {
1106  /* not waiting anymore */
1107  uint32 nwaiters PG_USED_FOR_ASSERTS_ONLY = pg_atomic_fetch_sub_u32(&lock->nwaiters, 1);
1108 
1109  Assert(nwaiters < MAX_BACKENDS);
1110  }
1111 #endif
1112 }
static uint32 pg_atomic_fetch_sub_u32(volatile pg_atomic_uint32 *ptr, int32 sub_)
Definition: atomics.h:343
void PGSemaphoreUnlock(PGSemaphore sema)
Definition: posix_sema.c:340
#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:130
static void LWLockWaitListUnlock(LWLock *lock)
Definition: lwlock.c:864
#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:358
unsigned int uint32
Definition: c.h:367
#define Assert(condition)
Definition: c.h:738
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:320
static void LWLockWaitListLock(LWLock *lock)
Definition: lwlock.c:812
int pgprocno
Definition: proc.h:110
static uint32 pg_atomic_fetch_or_u32(volatile pg_atomic_uint32 *ptr, uint32 or_)
Definition: atomics.h:372
PGSemaphore sem
Definition: proc.h:101
#define PG_USED_FOR_ASSERTS_ONLY
Definition: c.h:121
static uint32 pg_atomic_read_u32(volatile pg_atomic_uint32 *ptr)
Definition: atomics.h:241

◆ LWLockHeldByMe()

◆ LWLockHeldByMeInMode()

bool LWLockHeldByMeInMode ( LWLock l,
LWLockMode  mode 
)

Definition at line 1861 of file lwlock.c.

References i, and num_held_lwlocks.

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

1862 {
1863  int i;
1864 
1865  for (i = 0; i < num_held_lwlocks; i++)
1866  {
1867  if (held_lwlocks[i].lock == l && held_lwlocks[i].mode == mode)
1868  return true;
1869  }
1870  return false;
1871 }
static PgChecksumMode mode
Definition: pg_checksums.c:61
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 679 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(), InitPredicateLocks(), InitProcGlobal(), ReplicationOriginShmemInit(), ReplicationSlotsShmemInit(), SimpleLruInit(), sts_initialize(), tbm_prepare_shared_iterate(), and XLOGShmemInit().

680 {
682 #ifdef LOCK_DEBUG
683  pg_atomic_init_u32(&lock->nwaiters, 0);
684 #endif
685  lock->tranche = tranche_id;
686  proclist_init(&lock->waiters);
687 }
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:223

◆ LWLockNewTrancheId()

int LWLockNewTrancheId ( void  )

Definition at line 584 of file lwlock.c.

References ShmemLock, SpinLockAcquire, and SpinLockRelease.

Referenced by apw_init_shmem(), and InitializeLWLocks().

585 {
586  int result;
587  int *LWLockCounter;
588 
589  LWLockCounter = (int *) ((char *) MainLWLockArray - sizeof(int));
591  result = (*LWLockCounter)++;
593 
594  return result;
595 }
#define SpinLockAcquire(lock)
Definition: spin.h:62
#define SpinLockRelease(lock)
Definition: spin.h:64
slock_t * ShmemLock
Definition: shmem.c:88
LWLockPadded * MainLWLockArray
Definition: lwlock.c:125

◆ LWLockQueueSelf()

static void LWLockQueueSelf ( LWLock lock,
LWLockMode  mode 
)
static

Definition at line 984 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().

985 {
986  /*
987  * If we don't have a PGPROC structure, there's no way to wait. This
988  * should never occur, since MyProc should only be null during shared
989  * memory initialization.
990  */
991  if (MyProc == NULL)
992  elog(PANIC, "cannot wait without a PGPROC structure");
993 
994  if (MyProc->lwWaiting)
995  elog(PANIC, "queueing for lock while waiting on another one");
996 
997  LWLockWaitListLock(lock);
998 
999  /* setting the flag is protected by the spinlock */
1001 
1002  MyProc->lwWaiting = true;
1003  MyProc->lwWaitMode = mode;
1004 
1005  /* LW_WAIT_UNTIL_FREE waiters are always at the front of the queue */
1006  if (mode == LW_WAIT_UNTIL_FREE)
1007  proclist_push_head(&lock->waiters, MyProc->pgprocno, lwWaitLink);
1008  else
1009  proclist_push_tail(&lock->waiters, MyProc->pgprocno, lwWaitLink);
1010 
1011  /* Can release the mutex now */
1012  LWLockWaitListUnlock(lock);
1013 
1014 #ifdef LOCK_DEBUG
1015  pg_atomic_fetch_add_u32(&lock->nwaiters, 1);
1016 #endif
1017 
1018 }
static PgChecksumMode mode
Definition: pg_checksums.c:61
#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:130
static void LWLockWaitListUnlock(LWLock *lock)
Definition: lwlock.c:864
uint8 lwWaitMode
Definition: proc.h:131
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:328
#define proclist_push_tail(list, procno, link_member)
Definition: proclist.h:191
static void LWLockWaitListLock(LWLock *lock)
Definition: lwlock.c:812
int pgprocno
Definition: proc.h:110
#define elog(elevel,...)
Definition: elog.h:214
static uint32 pg_atomic_fetch_or_u32(volatile pg_atomic_uint32 *ptr, uint32 or_)
Definition: atomics.h:372

◆ LWLockRegisterTranche()

void LWLockRegisterTranche ( int  tranche_id,
const char *  tranche_name 
)

Definition at line 604 of file lwlock.c.

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

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

605 {
606  Assert(LWLockTrancheArray != NULL);
607 
608  if (tranche_id >= LWLockTranchesAllocated)
609  {
611  int j = LWLockTranchesAllocated;
612 
613  while (i <= tranche_id)
614  i *= 2;
615 
616  LWLockTrancheArray = (const char **)
617  repalloc(LWLockTrancheArray, i * sizeof(char *));
619  while (j < LWLockTranchesAllocated)
620  LWLockTrancheArray[j++] = NULL;
621  }
622 
623  LWLockTrancheArray[tranche_id] = tranche_name;
624 }
static int LWLockTranchesAllocated
Definition: lwlock.c:115
static const char ** LWLockTrancheArray
Definition: lwlock.c:114
#define Assert(condition)
Definition: c.h:738
void * repalloc(void *pointer, Size size)
Definition: mcxt.c:1069
int i

◆ LWLockRelease()

void LWLockRelease ( LWLock lock)

Definition at line 1727 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(), AbsorbSyncRequests(), ActivateCommitTs(), AdvanceNextFullTransactionIdPastXid(), 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(), copy_replication_slot(), 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(), ForwardSyncRequest(), 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(), HandleAutoVacLauncherInterrupts(), 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_get_replication_slots(), pg_get_shmem_allocations(), 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(), ProcKill(), ProcSleep(), ReadMultiXactCounts(), ReadNextFullTransactionId(), ReadNextMultiXactId(), ReadRecord(), 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(), TerminateOtherDBBackends(), 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(), XidCacheRemoveRunningXids(), xlog_redo(), XLogBackgroundFlush(), XLogFlush(), and XLogNeedsFlush().

1728 {
1729  LWLockMode mode;
1730  uint32 oldstate;
1731  bool check_waiters;
1732  int i;
1733 
1734  /*
1735  * Remove lock from list of locks held. Usually, but not always, it will
1736  * be the latest-acquired lock; so search array backwards.
1737  */
1738  for (i = num_held_lwlocks; --i >= 0;)
1739  if (lock == held_lwlocks[i].lock)
1740  break;
1741 
1742  if (i < 0)
1743  elog(ERROR, "lock %s is not held", T_NAME(lock));
1744 
1745  mode = held_lwlocks[i].mode;
1746 
1747  num_held_lwlocks--;
1748  for (; i < num_held_lwlocks; i++)
1749  held_lwlocks[i] = held_lwlocks[i + 1];
1750 
1751  PRINT_LWDEBUG("LWLockRelease", lock, mode);
1752 
1753  /*
1754  * Release my hold on lock, after that it can immediately be acquired by
1755  * others, even if we still have to wakeup other waiters.
1756  */
1757  if (mode == LW_EXCLUSIVE)
1758  oldstate = pg_atomic_sub_fetch_u32(&lock->state, LW_VAL_EXCLUSIVE);
1759  else
1760  oldstate = pg_atomic_sub_fetch_u32(&lock->state, LW_VAL_SHARED);
1761 
1762  /* nobody else can have that kind of lock */
1763  Assert(!(oldstate & LW_VAL_EXCLUSIVE));
1764 
1765 
1766  /*
1767  * We're still waiting for backends to get scheduled, don't wake them up
1768  * again.
1769  */
1770  if ((oldstate & (LW_FLAG_HAS_WAITERS | LW_FLAG_RELEASE_OK)) ==
1772  (oldstate & LW_LOCK_MASK) == 0)
1773  check_waiters = true;
1774  else
1775  check_waiters = false;
1776 
1777  /*
1778  * As waking up waiters requires the spinlock to be acquired, only do so
1779  * if necessary.
1780  */
1781  if (check_waiters)
1782  {
1783  /* XXX: remove before commit? */
1784  LOG_LWDEBUG("LWLockRelease", lock, "releasing waiters");
1785  LWLockWakeup(lock);
1786  }
1787 
1788  TRACE_POSTGRESQL_LWLOCK_RELEASE(T_NAME(lock));
1789 
1790  /*
1791  * Now okay to allow cancel/die interrupts.
1792  */
1794 }
#define T_NAME(lock)
Definition: lwlock.c:117
static PgChecksumMode mode
Definition: pg_checksums.c:61
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:401
#define LW_LOCK_MASK
Definition: lwlock.c:106
#define LW_VAL_SHARED
Definition: lwlock.c:104
#define RESUME_INTERRUPTS()
Definition: miscadmin.h:118
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:877
unsigned int uint32
Definition: c.h:367
static int num_held_lwlocks
Definition: lwlock.c:142
#define Assert(condition)
Definition: c.h:738
#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
#define elog(elevel,...)
Definition: elog.h:214
int i
#define LOG_LWDEBUG(a, b, c)
Definition: lwlock.c:228

◆ LWLockReleaseAll()

void LWLockReleaseAll ( void  )

Definition at line 1826 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().

1827 {
1828  while (num_held_lwlocks > 0)
1829  {
1830  HOLD_INTERRUPTS(); /* match the upcoming RESUME_INTERRUPTS */
1831 
1833  }
1834 }
void LWLockRelease(LWLock *lock)
Definition: lwlock.c:1727
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:116

◆ LWLockReleaseClearVar()

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

Definition at line 1800 of file lwlock.c.

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

Referenced by WALInsertLockRelease().

1801 {
1802  LWLockWaitListLock(lock);
1803 
1804  /*
1805  * Set the variable's value before releasing the lock, that prevents race
1806  * a race condition wherein a new locker acquires the lock, but hasn't yet
1807  * set the variables value.
1808  */
1809  *valptr = val;
1810  LWLockWaitListUnlock(lock);
1811 
1812  LWLockRelease(lock);
1813 }
static void LWLockWaitListUnlock(LWLock *lock)
Definition: lwlock.c:864
void LWLockRelease(LWLock *lock)
Definition: lwlock.c:1727
static void LWLockWaitListLock(LWLock *lock)
Definition: lwlock.c:812
long val
Definition: informix.c:664

◆ LWLockReportWaitEnd()

static void LWLockReportWaitEnd ( void  )
inlinestatic

Definition at line 706 of file lwlock.c.

References pgstat_report_wait_end().

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

707 {
709 }
static void pgstat_report_wait_end(void)
Definition: pgstat.h:1330

◆ LWLockReportWaitStart()

static void LWLockReportWaitStart ( LWLock lock)
inlinestatic

Definition at line 697 of file lwlock.c.

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

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

698 {
700 }
uint16 tranche
Definition: lwlock.h:34
static void pgstat_report_wait_start(uint32 wait_event_info)
Definition: pgstat.h:1306
#define PG_WAIT_LWLOCK
Definition: pgstat.h:737

◆ LWLockShmemSize()

Size LWLockShmemSize ( void  )

Definition at line 350 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().

351 {
352  Size size;
353  int i;
354  int numLocks = NUM_FIXED_LWLOCKS;
355 
356  numLocks += NumLWLocksByNamedTranches();
357 
358  /* Space for the LWLock array. */
359  size = mul_size(numLocks, sizeof(LWLockPadded));
360 
361  /* Space for dynamic allocation counter, plus room for alignment. */
362  size = add_size(size, sizeof(int) + LWLOCK_PADDED_SIZE);
363 
364  /* space for named tranches. */
366 
367  /* space for name of each tranche. */
368  for (i = 0; i < NamedLWLockTrancheRequests; i++)
369  size = add_size(size, strlen(NamedLWLockTrancheRequestArray[i].tranche_name) + 1);
370 
371  /* Disallow named LWLocks' requests after startup */
373 
374  return size;
375 }
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:515
Size add_size(Size s1, Size s2)
Definition: shmem.c:498
size_t Size
Definition: c.h:466
static int NumLWLocksByNamedTranches(void)
Definition: lwlock.c:335
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 1673 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().

1674 {
1675  proclist_head wakeup;
1676  proclist_mutable_iter iter;
1677 
1678  PRINT_LWDEBUG("LWLockUpdateVar", lock, LW_EXCLUSIVE);
1679 
1680  proclist_init(&wakeup);
1681 
1682  LWLockWaitListLock(lock);
1683 
1685 
1686  /* Update the lock's value */
1687  *valptr = val;
1688 
1689  /*
1690  * See if there are any LW_WAIT_UNTIL_FREE waiters that need to be woken
1691  * up. They are always in the front of the queue.
1692  */
1693  proclist_foreach_modify(iter, &lock->waiters, lwWaitLink)
1694  {
1695  PGPROC *waiter = GetPGProcByNumber(iter.cur);
1696 
1697  if (waiter->lwWaitMode != LW_WAIT_UNTIL_FREE)
1698  break;
1699 
1700  proclist_delete(&lock->waiters, iter.cur, lwWaitLink);
1701  proclist_push_tail(&wakeup, iter.cur, lwWaitLink);
1702  }
1703 
1704  /* We are done updating shared state of the lock itself. */
1705  LWLockWaitListUnlock(lock);
1706 
1707  /*
1708  * Awaken any waiters I removed from the queue.
1709  */
1710  proclist_foreach_modify(iter, &wakeup, lwWaitLink)
1711  {
1712  PGPROC *waiter = GetPGProcByNumber(iter.cur);
1713 
1714  proclist_delete(&wakeup, iter.cur, lwWaitLink);
1715  /* check comment in LWLockWakeup() about this barrier */
1716  pg_write_barrier();
1717  waiter->lwWaiting = false;
1718  PGSemaphoreUnlock(waiter->sem);
1719  }
1720 }
#define GetPGProcByNumber(n)
Definition: proc.h:282
void PGSemaphoreUnlock(PGSemaphore sema)
Definition: posix_sema.c:340
proclist_head waiters
Definition: lwlock.h:36
bool lwWaiting
Definition: proc.h:130
static void LWLockWaitListUnlock(LWLock *lock)
Definition: lwlock.c:864
#define proclist_foreach_modify(iter, lhead, link_member)
Definition: proclist.h:206
uint8 lwWaitMode
Definition: proc.h:131
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:738
#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:812
#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:159
PGSemaphore sem
Definition: proc.h:101
Definition: proc.h:95
long val
Definition: informix.c:664
static uint32 pg_atomic_read_u32(volatile pg_atomic_uint32 *ptr)
Definition: atomics.h:241

◆ LWLockWaitForVar()

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

Definition at line 1534 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().

1535 {
1536  PGPROC *proc = MyProc;
1537  int extraWaits = 0;
1538  bool result = false;
1539 #ifdef LWLOCK_STATS
1540  lwlock_stats *lwstats;
1541 
1542  lwstats = get_lwlock_stats_entry(lock);
1543 #endif
1544 
1545  PRINT_LWDEBUG("LWLockWaitForVar", lock, LW_WAIT_UNTIL_FREE);
1546 
1547  /*
1548  * Lock out cancel/die interrupts while we sleep on the lock. There is no
1549  * cleanup mechanism to remove us from the wait queue if we got
1550  * interrupted.
1551  */
1552  HOLD_INTERRUPTS();
1553 
1554  /*
1555  * Loop here to check the lock's status after each time we are signaled.
1556  */
1557  for (;;)
1558  {
1559  bool mustwait;
1560 
1561  mustwait = LWLockConflictsWithVar(lock, valptr, oldval, newval,
1562  &result);
1563 
1564  if (!mustwait)
1565  break; /* the lock was free or value didn't match */
1566 
1567  /*
1568  * Add myself to wait queue. Note that this is racy, somebody else
1569  * could wakeup before we're finished queuing. NB: We're using nearly
1570  * the same twice-in-a-row lock acquisition protocol as
1571  * LWLockAcquire(). Check its comments for details. The only
1572  * difference is that we also have to check the variable's values when
1573  * checking the state of the lock.
1574  */
1576 
1577  /*
1578  * Set RELEASE_OK flag, to make sure we get woken up as soon as the
1579  * lock is released.
1580  */
1582 
1583  /*
1584  * We're now guaranteed to be woken up if necessary. Recheck the lock
1585  * and variables state.
1586  */
1587  mustwait = LWLockConflictsWithVar(lock, valptr, oldval, newval,
1588  &result);
1589 
1590  /* Ok, no conflict after we queued ourselves. Undo queueing. */
1591  if (!mustwait)
1592  {
1593  LOG_LWDEBUG("LWLockWaitForVar", lock, "free, undoing queue");
1594 
1595  LWLockDequeueSelf(lock);
1596  break;
1597  }
1598 
1599  /*
1600  * Wait until awakened.
1601  *
1602  * Since we share the process wait semaphore with the regular lock
1603  * manager and ProcWaitForSignal, and we may need to acquire an LWLock
1604  * while one of those is pending, it is possible that we get awakened
1605  * for a reason other than being signaled by LWLockRelease. If so,
1606  * loop back and wait again. Once we've gotten the LWLock,
1607  * re-increment the sema by the number of additional signals received,
1608  * so that the lock manager or signal manager will see the received
1609  * signal when it next waits.
1610  */
1611  LOG_LWDEBUG("LWLockWaitForVar", lock, "waiting");
1612 
1613 #ifdef LWLOCK_STATS
1614  lwstats->block_count++;
1615 #endif
1616 
1617  LWLockReportWaitStart(lock);
1618  TRACE_POSTGRESQL_LWLOCK_WAIT_START(T_NAME(lock), LW_EXCLUSIVE);
1619 
1620  for (;;)
1621  {
1622  PGSemaphoreLock(proc->sem);
1623  if (!proc->lwWaiting)
1624  break;
1625  extraWaits++;
1626  }
1627 
1628 #ifdef LOCK_DEBUG
1629  {
1630  /* not waiting anymore */
1631  uint32 nwaiters PG_USED_FOR_ASSERTS_ONLY = pg_atomic_fetch_sub_u32(&lock->nwaiters, 1);
1632 
1633  Assert(nwaiters < MAX_BACKENDS);
1634  }
1635 #endif
1636 
1637  TRACE_POSTGRESQL_LWLOCK_WAIT_DONE(T_NAME(lock), LW_EXCLUSIVE);
1639 
1640  LOG_LWDEBUG("LWLockWaitForVar", lock, "awakened");
1641 
1642  /* Now loop back and check the status of the lock again. */
1643  }
1644 
1645  TRACE_POSTGRESQL_LWLOCK_ACQUIRE(T_NAME(lock), LW_EXCLUSIVE);
1646 
1647  /*
1648  * Fix the process wait semaphore's count for any absorbed wakeups.
1649  */
1650  while (extraWaits-- > 0)
1651  PGSemaphoreUnlock(proc->sem);
1652 
1653  /*
1654  * Now okay to allow cancel/die interrupts.
1655  */
1657 
1658  return result;
1659 }
#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:343
void PGSemaphoreUnlock(PGSemaphore sema)
Definition: posix_sema.c:340
PGPROC * MyProc
Definition: proc.c:67
bool lwWaiting
Definition: proc.h:130
pg_atomic_uint32 state
Definition: lwlock.h:35
#define RESUME_INTERRUPTS()
Definition: miscadmin.h:118
#define MAX_BACKENDS
Definition: postmaster.h:75
static void LWLockReportWaitEnd(void)
Definition: lwlock.c:706
unsigned int uint32
Definition: c.h:367
static void LWLockDequeueSelf(LWLock *lock)
Definition: lwlock.c:1028
static void LWLockReportWaitStart(LWLock *lock)
Definition: lwlock.c:697
static void LWLockQueueSelf(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:984
#define Assert(condition)
Definition: c.h:738
#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:320
static bool LWLockConflictsWithVar(LWLock *lock, uint64 *valptr, uint64 oldval, uint64 *newval, bool *result)
Definition: lwlock.c:1474
#define HOLD_INTERRUPTS()
Definition: miscadmin.h:116
static uint32 pg_atomic_fetch_or_u32(volatile pg_atomic_uint32 *ptr, uint32 or_)
Definition: atomics.h:372
PGSemaphore sem
Definition: proc.h:101
Definition: proc.h:95
#define PG_USED_FOR_ASSERTS_ONLY
Definition: c.h:121
#define LOG_LWDEBUG(a, b, c)
Definition: lwlock.c:228

◆ LWLockWaitListLock()

static void LWLockWaitListLock ( LWLock lock)
static

Definition at line 812 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().

813 {
814  uint32 old_state;
815 #ifdef LWLOCK_STATS
816  lwlock_stats *lwstats;
817  uint32 delays = 0;
818 
819  lwstats = get_lwlock_stats_entry(lock);
820 #endif
821 
822  while (true)
823  {
824  /* always try once to acquire lock directly */
825  old_state = pg_atomic_fetch_or_u32(&lock->state, LW_FLAG_LOCKED);
826  if (!(old_state & LW_FLAG_LOCKED))
827  break; /* got lock */
828 
829  /* and then spin without atomic operations until lock is released */
830  {
831  SpinDelayStatus delayStatus;
832 
833  init_local_spin_delay(&delayStatus);
834 
835  while (old_state & LW_FLAG_LOCKED)
836  {
837  perform_spin_delay(&delayStatus);
838  old_state = pg_atomic_read_u32(&lock->state);
839  }
840 #ifdef LWLOCK_STATS
841  delays += delayStatus.delays;
842 #endif
843  finish_spin_delay(&delayStatus);
844  }
845 
846  /*
847  * Retry. The lock might obviously already be re-acquired by the time
848  * we're attempting to get it again.
849  */
850  }
851 
852 #ifdef LWLOCK_STATS
853  lwstats->spin_delay_count += delays;
854 #endif
855 }
#define init_local_spin_delay(status)
Definition: s_lock.h:1043
#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:174
unsigned int uint32
Definition: c.h:367
static uint32 pg_atomic_fetch_or_u32(volatile pg_atomic_uint32 *ptr, uint32 or_)
Definition: atomics.h:372
void perform_spin_delay(SpinDelayStatus *status)
Definition: s_lock.c:124
static uint32 pg_atomic_read_u32(volatile pg_atomic_uint32 *ptr)
Definition: atomics.h:241

◆ LWLockWaitListUnlock()

static void LWLockWaitListUnlock ( LWLock lock)
static

Definition at line 864 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().

865 {
867 
868  old_state = pg_atomic_fetch_and_u32(&lock->state, ~LW_FLAG_LOCKED);
869 
870  Assert(old_state & LW_FLAG_LOCKED);
871 }
#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:358
unsigned int uint32
Definition: c.h:367
#define Assert(condition)
Definition: c.h:738
#define PG_USED_FOR_ASSERTS_ONLY
Definition: c.h:121

◆ LWLockWakeup()

static void LWLockWakeup ( LWLock lock)
static

Definition at line 877 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().

878 {
879  bool new_release_ok;
880  bool wokeup_somebody = false;
881  proclist_head wakeup;
883 
884  proclist_init(&wakeup);
885 
886  new_release_ok = true;
887 
888  /* lock wait list while collecting backends to wake up */
889  LWLockWaitListLock(lock);
890 
891  proclist_foreach_modify(iter, &lock->waiters, lwWaitLink)
892  {
893  PGPROC *waiter = GetPGProcByNumber(iter.cur);
894 
895  if (wokeup_somebody && waiter->lwWaitMode == LW_EXCLUSIVE)
896  continue;
897 
898  proclist_delete(&lock->waiters, iter.cur, lwWaitLink);
899  proclist_push_tail(&wakeup, iter.cur, lwWaitLink);
900 
901  if (waiter->lwWaitMode != LW_WAIT_UNTIL_FREE)
902  {
903  /*
904  * Prevent additional wakeups until retryer gets to run. Backends
905  * that are just waiting for the lock to become free don't retry
906  * automatically.
907  */
908  new_release_ok = false;
909 
910  /*
911  * Don't wakeup (further) exclusive locks.
912  */
913  wokeup_somebody = true;
914  }
915 
916  /*
917  * Once we've woken up an exclusive lock, there's no point in waking
918  * up anybody else.
919  */
920  if (waiter->lwWaitMode == LW_EXCLUSIVE)
921  break;
922  }
923 
925 
926  /* unset required flags, and release lock, in one fell swoop */
927  {
928  uint32 old_state;
929  uint32 desired_state;
930 
931  old_state = pg_atomic_read_u32(&lock->state);
932  while (true)
933  {
934  desired_state = old_state;
935 
936  /* compute desired flags */
937 
938  if (new_release_ok)
939  desired_state |= LW_FLAG_RELEASE_OK;
940  else
941  desired_state &= ~LW_FLAG_RELEASE_OK;
942 
943  if (proclist_is_empty(&wakeup))
944  desired_state &= ~LW_FLAG_HAS_WAITERS;
945 
946  desired_state &= ~LW_FLAG_LOCKED; /* release lock */
947 
948  if (pg_atomic_compare_exchange_u32(&lock->state, &old_state,
949  desired_state))
950  break;
951  }
952  }
953 
954  /* Awaken any waiters I removed from the queue. */
955  proclist_foreach_modify(iter, &wakeup, lwWaitLink)
956  {
957  PGPROC *waiter = GetPGProcByNumber(iter.cur);
958 
959  LOG_LWDEBUG("LWLockRelease", lock, "release waiter");
960  proclist_delete(&wakeup, iter.cur, lwWaitLink);
961 
962  /*
963  * Guarantee that lwWaiting being unset only becomes visible once the
964  * unlink from the link has completed. Otherwise the target backend
965  * could be woken up for other reason and enqueue for a new lock - if
966  * that happens before the list unlink happens, the list would end up
967  * being corrupted.
968  *
969  * The barrier pairs with the LWLockWaitListLock() when enqueuing for
970  * another lock.
971  */
973  waiter->lwWaiting = false;
974  PGSemaphoreUnlock(waiter->sem);
975  }
976 }
#define GetPGProcByNumber(n)
Definition: proc.h:282
#define LW_FLAG_LOCKED
Definition: lwlock.c:101
void PGSemaphoreUnlock(PGSemaphore sema)
Definition: posix_sema.c:340
#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:311
proclist_head waiters
Definition: lwlock.h:36
bool lwWaiting
Definition: proc.h:130
#define proclist_foreach_modify(iter, lhead, link_member)
Definition: proclist.h:206
uint8 lwWaitMode
Definition: proc.h:131
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:367
#define Assert(condition)
Definition: c.h:738
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:812
static void proclist_init(proclist_head *list)
Definition: proclist.h:29
#define pg_write_barrier()
Definition: atomics.h:159
PGSemaphore sem
Definition: proc.h:101
Definition: proc.h:95
static uint32 pg_atomic_read_u32(volatile pg_atomic_uint32 *ptr)
Definition: atomics.h:241
#define LOG_LWDEBUG(a, b, c)
Definition: lwlock.c:228

◆ NumLWLocksByNamedTranches()

static int NumLWLocksByNamedTranches ( void  )
static

Definition at line 335 of file lwlock.c.

References i, and NamedLWLockTrancheRequests.

Referenced by InitializeLWLocks(), and LWLockShmemSize().

336 {
337  int numLocks = 0;
338  int i;
339 
340  for (i = 0; i < NamedLWLockTrancheRequests; i++)
341  numLocks += NamedLWLockTrancheRequestArray[i].num_lwlocks;
342 
343  return numLocks;
344 }
int NamedLWLockTrancheRequests
Definition: lwlock.c:154
NamedLWLockTrancheRequest * NamedLWLockTrancheRequestArray
Definition: lwlock.c:152
int i

◆ RegisterLWLockTranches()

static void RegisterLWLockTranches ( void  )
static

Definition at line 492 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_HASH_JOIN, LWTRANCHE_PARALLEL_QUERY_DSA, LWTRANCHE_PREDICATE_LOCK_MANAGER, LWTRANCHE_SESSION_DSA, LWTRANCHE_SESSION_RECORD_TABLE, LWTRANCHE_SESSION_TYPMOD_TABLE, LWTRANCHE_SHARED_TUPLESTORE, LWTRANCHE_SXACT, LWTRANCHE_TBM, MainLWLockNames, MemoryContextAllocZero(), NamedLWLockTrancheRequests, and TopMemoryContext.

Referenced by CreateLWLocks().

493 {
494  int i;
495 
496  if (LWLockTrancheArray == NULL)
497  {
499  LWLockTrancheArray = (const char **)
501  LWLockTranchesAllocated * sizeof(char *));
503  }
504 
505  for (i = 0; i < NUM_INDIVIDUAL_LWLOCKS; ++i)
507 
511  "predicate_lock_manager");
513  "parallel_query_dsa");
515  "session_dsa");
517  "session_record_table");
519  "session_typmod_table");
521  "shared_tuplestore");
525  LWLockRegisterTranche(LWTRANCHE_SXACT, "serializable_xact");
526 
527  /* Register named tranches. */
528  for (i = 0; i < NamedLWLockTrancheRequests; i++)
530  NamedLWLockTrancheArray[i].trancheName);
531 }
NamedLWLockTranche * NamedLWLockTrancheArray
Definition: lwlock.c:156
void LWLockRegisterTranche(int tranche_id, const char *tranche_name)
Definition: lwlock.c:604
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:44
void * MemoryContextAllocZero(MemoryContext context, Size size)
Definition: mcxt.c:839
#define Assert(condition)
Definition: c.h:738
int i
const char *const MainLWLockNames[]

◆ RequestNamedLWLockTranche()

void RequestNamedLWLockTranche ( const char *  tranche_name,
int  num_lwlocks 
)

Definition at line 639 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().

640 {
641  NamedLWLockTrancheRequest *request;
642 
644  return; /* too late */
645 
646  if (NamedLWLockTrancheRequestArray == NULL)
647  {
652  * sizeof(NamedLWLockTrancheRequest));
653  }
654 
656  {
658 
659  while (i <= NamedLWLockTrancheRequests)
660  i *= 2;
661 
664  i * sizeof(NamedLWLockTrancheRequest));
666  }
667 
669  Assert(strlen(tranche_name) + 1 < NAMEDATALEN);
670  StrNCpy(request->tranche_name, tranche_name, NAMEDATALEN);
671  request->num_lwlocks = num_lwlocks;
673 }
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:109
MemoryContext TopMemoryContext
Definition: mcxt.c:44
static int NamedLWLockTrancheRequestsAllocated
Definition: lwlock.c:153
#define Assert(condition)
Definition: c.h:738
#define StrNCpy(dst, src, len)
Definition: c.h:944
void * repalloc(void *pointer, Size size)
Definition: mcxt.c:1069
NamedLWLockTrancheRequest * NamedLWLockTrancheRequestArray
Definition: lwlock.c:152
void * MemoryContextAlloc(MemoryContext context, Size size)
Definition: mcxt.c:796
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