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 MAX_SIMUL_LWLOCKS   200
 
#define T_NAME(lock)   GetLWTrancheName((lock)->tranche)
 
#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

 StaticAssertDecl (lengthof(BuiltinTrancheNames)==LWTRANCHE_FIRST_USER_DEFINED - NUM_INDIVIDUAL_LWLOCKS, "missing entries in BuiltinTrancheNames[]")
 
static void InitializeLWLocks (void)
 
static void LWLockReportWaitStart (LWLock *lock)
 
static void LWLockReportWaitEnd (void)
 
static const char * GetLWTrancheName (uint16 trancheId)
 
static int NumLWLocksForNamedTranches (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
 
const char *const IndividualLWLockNames []
 
static const char *const BuiltinTrancheNames []
 
static const char ** LWLockTrancheNames = NULL
 
static int LWLockTrancheNamesAllocated = 0
 
LWLockPaddedMainLWLockArray = NULL
 
static int num_held_lwlocks = 0
 
static LWLockHandle held_lwlocks [MAX_SIMUL_LWLOCKS]
 
static 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 208 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)    GetLWTrancheName((lock)->tranche)

Typedef Documentation

◆ LWLockHandle

typedef struct LWLockHandle LWLockHandle

◆ NamedLWLockTrancheRequest

Function Documentation

◆ CreateLWLocks()

void CreateLWLocks ( void  )

Definition at line 468 of file lwlock.c.

References i, InitializeLWLocks(), IsUnderPostmaster, LW_VAL_EXCLUSIVE, LWLOCK_MINIMAL_SIZE, LWLOCK_PADDED_SIZE, LWLockRegisterTranche(), LWLockShmemSize(), LWTRANCHE_FIRST_USER_DEFINED, MAX_BACKENDS, NamedLWLockTrancheRequests, ShmemAlloc(), and StaticAssertStmt.

Referenced by CreateSharedMemoryAndSemaphores().

469 {
471  "MAX_BACKENDS too big for lwlock.c");
472 
474  sizeof(LWLock) <= LWLOCK_PADDED_SIZE,
475  "Miscalculated LWLock padding");
476 
477  if (!IsUnderPostmaster)
478  {
479  Size spaceLocks = LWLockShmemSize();
480  int *LWLockCounter;
481  char *ptr;
482 
483  /* Allocate space */
484  ptr = (char *) ShmemAlloc(spaceLocks);
485 
486  /* Leave room for dynamic allocation of tranches */
487  ptr += sizeof(int);
488 
489  /* Ensure desired alignment of LWLock array */
490  ptr += LWLOCK_PADDED_SIZE - ((uintptr_t) ptr) % LWLOCK_PADDED_SIZE;
491 
492  MainLWLockArray = (LWLockPadded *) ptr;
493 
494  /*
495  * Initialize the dynamic-allocation counter for tranches, which is
496  * stored just before the first LWLock.
497  */
498  LWLockCounter = (int *) ((char *) MainLWLockArray - sizeof(int));
499  *LWLockCounter = LWTRANCHE_FIRST_USER_DEFINED;
500 
501  /* Initialize all LWLocks */
503  }
504 
505  /* Register named extension LWLock tranches in the current process. */
506  for (int i = 0; i < NamedLWLockTrancheRequests; i++)
508  NamedLWLockTrancheArray[i].trancheName);
509 }
Definition: lwlock.h:31
void * ShmemAlloc(Size size)
Definition: shmem.c:161
NamedLWLockTranche * NamedLWLockTrancheArray
Definition: lwlock.c:239
Size LWLockShmemSize(void)
Definition: lwlock.c:435
void LWLockRegisterTranche(int tranche_id, const char *tranche_name)
Definition: lwlock.c:653
#define StaticAssertStmt(condition, errmessage)
Definition: c.h:859
#define LWLOCK_MINIMAL_SIZE
Definition: lwlock.h:73
#define MAX_BACKENDS
Definition: postmaster.h:75
int NamedLWLockTrancheRequests
Definition: lwlock.c:236
bool IsUnderPostmaster
Definition: globals.c:109
unsigned int uint32
Definition: c.h:374
static void InitializeLWLocks(void)
Definition: lwlock.c:515
size_t Size
Definition: c.h:473
#define LW_VAL_EXCLUSIVE
Definition: lwlock.c:103
int i
#define LWLOCK_PADDED_SIZE
Definition: lwlock.h:72
LWLockPadded * MainLWLockArray
Definition: lwlock.c:200

◆ GetLWLockIdentifier()

const char* GetLWLockIdentifier ( uint32  classId,
uint16  eventId 
)

Definition at line 809 of file lwlock.c.

References Assert, GetLWTrancheName(), and PG_WAIT_LWLOCK.

Referenced by pgstat_get_wait_event().

810 {
811  Assert(classId == PG_WAIT_LWLOCK);
812  /* The event IDs are just tranche numbers. */
813  return GetLWTrancheName(eventId);
814 }
static const char * GetLWTrancheName(uint16 trancheId)
Definition: lwlock.c:781
#define Assert(condition)
Definition: c.h:745
#define PG_WAIT_LWLOCK
Definition: pgstat.h:784

◆ GetLWTrancheName()

static const char * GetLWTrancheName ( uint16  trancheId)
static

Definition at line 781 of file lwlock.c.

References BuiltinTrancheNames, IndividualLWLockNames, LWLockTrancheNames, LWLockTrancheNamesAllocated, and LWTRANCHE_FIRST_USER_DEFINED.

Referenced by GetLWLockIdentifier().

782 {
783  /* Individual LWLock? */
784  if (trancheId < NUM_INDIVIDUAL_LWLOCKS)
785  return IndividualLWLockNames[trancheId];
786 
787  /* Built-in tranche? */
788  if (trancheId < LWTRANCHE_FIRST_USER_DEFINED)
789  return BuiltinTrancheNames[trancheId - NUM_INDIVIDUAL_LWLOCKS];
790 
791  /*
792  * It's an extension tranche, so look in LWLockTrancheNames[]. However,
793  * it's possible that the tranche has never been registered in the current
794  * process, in which case give up and return "extension".
795  */
796  trancheId -= LWTRANCHE_FIRST_USER_DEFINED;
797 
798  if (trancheId >= LWLockTrancheNamesAllocated ||
799  LWLockTrancheNames[trancheId] == NULL)
800  return "extension";
801 
802  return LWLockTrancheNames[trancheId];
803 }
static int LWLockTrancheNamesAllocated
Definition: lwlock.c:193
const char *const IndividualLWLockNames[]
static const char *const BuiltinTrancheNames[]
Definition: lwlock.c:130
static const char ** LWLockTrancheNames
Definition: lwlock.c:192

◆ GetNamedLWLockTranche()

LWLockPadded* GetNamedLWLockTranche ( const char *  tranche_name)

Definition at line 599 of file lwlock.c.

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

Referenced by pgss_shmem_startup().

600 {
601  int lock_pos;
602  int i;
603 
604  /*
605  * Obtain the position of base address of LWLock belonging to requested
606  * tranche_name in MainLWLockArray. LWLocks for named tranches are placed
607  * in MainLWLockArray after fixed locks.
608  */
609  lock_pos = NUM_FIXED_LWLOCKS;
610  for (i = 0; i < NamedLWLockTrancheRequests; i++)
611  {
612  if (strcmp(NamedLWLockTrancheRequestArray[i].tranche_name,
613  tranche_name) == 0)
614  return &MainLWLockArray[lock_pos];
615 
617  }
618 
619  elog(ERROR, "requested tranche is not registered");
620 
621  /* just to keep compiler quiet */
622  return NULL;
623 }
#define NUM_FIXED_LWLOCKS
Definition: lwlock.h:127
#define ERROR
Definition: elog.h:43
int NamedLWLockTrancheRequests
Definition: lwlock.c:236
static NamedLWLockTrancheRequest * NamedLWLockTrancheRequestArray
Definition: lwlock.c:227
#define elog(elevel,...)
Definition: elog.h:214
int i
LWLockPadded * MainLWLockArray
Definition: lwlock.c:200

◆ InitializeLWLocks()

static void InitializeLWLocks ( void  )
static

Definition at line 515 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, NumLWLocksForNamedTranches(), NamedLWLockTrancheRequest::tranche_name, NamedLWLockTranche::trancheId, and NamedLWLockTranche::trancheName.

Referenced by CreateLWLocks().

516 {
517  int numNamedLocks = NumLWLocksForNamedTranches();
518  int id;
519  int i;
520  int j;
521  LWLockPadded *lock;
522 
523  /* Initialize all individual LWLocks in main array */
524  for (id = 0, lock = MainLWLockArray; id < NUM_INDIVIDUAL_LWLOCKS; id++, lock++)
525  LWLockInitialize(&lock->lock, id);
526 
527  /* Initialize buffer mapping LWLocks in main array */
528  lock = MainLWLockArray + NUM_INDIVIDUAL_LWLOCKS;
529  for (id = 0; id < NUM_BUFFER_PARTITIONS; id++, lock++)
531 
532  /* Initialize lmgrs' LWLocks in main array */
533  lock = MainLWLockArray + NUM_INDIVIDUAL_LWLOCKS + NUM_BUFFER_PARTITIONS;
534  for (id = 0; id < NUM_LOCK_PARTITIONS; id++, lock++)
536 
537  /* Initialize predicate lmgrs' LWLocks in main array */
538  lock = MainLWLockArray + NUM_INDIVIDUAL_LWLOCKS +
539  NUM_BUFFER_PARTITIONS + NUM_LOCK_PARTITIONS;
540  for (id = 0; id < NUM_PREDICATELOCK_PARTITIONS; id++, lock++)
542 
543  /*
544  * Copy the info about any named tranches into shared memory (so that
545  * other processes can see it), and initialize the requested LWLocks.
546  */
548  {
549  char *trancheNames;
550 
552  &MainLWLockArray[NUM_FIXED_LWLOCKS + numNamedLocks];
553 
554  trancheNames = (char *) NamedLWLockTrancheArray +
557 
558  for (i = 0; i < NamedLWLockTrancheRequests; i++)
559  {
560  NamedLWLockTrancheRequest *request;
561  NamedLWLockTranche *tranche;
562  char *name;
563 
564  request = &NamedLWLockTrancheRequestArray[i];
565  tranche = &NamedLWLockTrancheArray[i];
566 
567  name = trancheNames;
568  trancheNames += strlen(request->tranche_name) + 1;
569  strcpy(name, request->tranche_name);
570  tranche->trancheId = LWLockNewTrancheId();
571  tranche->trancheName = name;
572 
573  for (j = 0; j < request->num_lwlocks; j++, lock++)
574  LWLockInitialize(&lock->lock, tranche->trancheId);
575  }
576  }
577 }
int LWLockNewTrancheId(void)
Definition: lwlock.c:629
char tranche_name[NAMEDATALEN]
Definition: lwlock.c:223
NamedLWLockTranche * NamedLWLockTrancheArray
Definition: lwlock.c:239
#define NUM_FIXED_LWLOCKS
Definition: lwlock.h:127
int NamedLWLockTrancheRequests
Definition: lwlock.c:236
static int NumLWLocksForNamedTranches(void)
Definition: lwlock.c:420
#define NUM_BUFFER_PARTITIONS
Definition: lwlock.h:111
char * trancheName
Definition: lwlock.h:95
void LWLockInitialize(LWLock *lock, int tranche_id)
Definition: lwlock.c:745
LWLock lock
Definition: lwlock.h:78
const char * name
Definition: encode.c:561
static NamedLWLockTrancheRequest * NamedLWLockTrancheRequestArray
Definition: lwlock.c:227
int i
LWLockPadded * MainLWLockArray
Definition: lwlock.c:200
#define NUM_LOCK_PARTITIONS
Definition: lwlock.h:115
#define NUM_PREDICATELOCK_PARTITIONS
Definition: lwlock.h:119

◆ InitLWLockAccess()

void InitLWLockAccess ( void  )

Definition at line 583 of file lwlock.c.

Referenced by InitProcess().

584 {
585 #ifdef LWLOCK_STATS
586  init_lwlock_stats();
587 #endif
588 }

◆ LWLockAcquire()

bool LWLockAcquire ( LWLock lock,
LWLockMode  mode 
)

Definition at line 1208 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(), ApplyLauncherMain(), apw_detach_shmem(), apw_dump_now(), apw_init_shmem(), apw_load_buffers(), asyncQueueAddEntries(), asyncQueueAdvanceTail(), asyncQueueReadAllNotifications(), asyncQueueUnregister(), 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(), ComputeXidHorizons(), 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(), FlushRelationsAllBuffers(), ForceTransactionIdLimitUpdate(), ForwardSyncRequest(), FreeWorkerInfo(), GetBackgroundWorkerPid(), GetBackgroundWorkerTypeByPid(), GetBlockerStatusData(), GetConflictingVirtualXIDs(), GetCurrentVirtualXIDs(), GetLastImportantRecPtr(), GetLastSegSwitchData(), GetLatestCommitTsData(), GetLockConflicts(), GetLockStatusData(), GetMultiXactIdMembers(), GetNewMultiXactId(), GetNewObjectId(), GetNewTransactionId(), GetOldestActiveTransactionId(), GetOldestMultiXactId(), GetOldestRestartPoint(), GetOldestSafeDecodingTransactionId(), GetOldSnapshotFromTimeMapping(), GetOldSnapshotTimeMapping(), GetPredicateLockStatusData(), GetPreparedTransactionList(), GetRunningTransactionData(), GetRunningTransactionLocks(), GetSafeSnapshot(), GetSafeSnapshotBlockingPids(), GetSerializableTransactionSnapshotInt(), GetSnapshotData(), GetVirtualXIDsDelayingChkpt(), HandleAutoVacLauncherInterrupts(), HaveVirtualXIDsDelayingChkpt(), InstallXLogFileSegment(), InvalidateBuffer(), InvalidateObsoleteReplicationSlots(), 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(), 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_statements_internal(), pg_xact_status(), pgss_shmem_startup(), pgss_store(), PostPrepare_Locks(), PostPrepare_MultiXact(), PostPrepare_Twophase(), PreCommit_CheckForSerializationFailure(), PreCommit_Notify(), predicatelock_twophase_recover(), PredicateLockPageSplit(), PredicateLockTwoPhaseFinish(), PrefetchSharedBuffer(), PrescanPreparedTransactions(), ProcArrayAdd(), ProcArrayApplyRecoveryInfo(), ProcArrayApplyXidAssignment(), ProcArrayClearTransaction(), ProcArrayEndTransaction(), 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(), ReplicationSlotAcquireInternal(), 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(), SerialAdd(), SerialGetMinConflictCommitSeqNo(), SerialSetActiveSerXmin(), SetCommitTsLimit(), SetMultiXactIdLimit(), SetOffsetVacuumLimit(), SetTransactionIdLimit(), SetXidCommitTsInPage(), SharedInvalBackendInit(), ShmemInitStruct(), SICleanupQueue(), SIGetDataEntries(), SignalBackends(), SIInsertDataEntries(), SimpleLruReadPage(), SimpleLruReadPage_ReadOnly(), SimpleLruTruncate(), SimpleLruWaitIO(), SimpleLruWriteAll(), SlruDeleteSegment(), SlruInternalWritePage(), SnapBuildInitialSnapshot(), ss_get_location(), StandbyRecoverPreparedTransactions(), StartBufferIO(), StartupCLOG(), StartupDecodingContext(), StartupSUBTRANS(), StartupXLOG(), sts_parallel_scan_next(), SubTransSetParent(), SummarizeOldestCommittedSxact(), SyncOneBuffer(), SyncRepCancelWait(), SyncRepCleanupAtProcExit(), SyncRepReleaseWaiters(), SyncRepUpdateSyncStandbysDefined(), SyncRepWaitForLSN(), TablespaceCreateDbspace(), tbm_shared_iterate(), TerminateBackgroundWorker(), TerminateOtherDBBackends(), TransactionGroupUpdateXidStatus(), TransactionIdGetCommitTsData(), TransactionIdIsActive(), TransactionIdIsInProgress(), TransactionIdSetPageStatus(), TransactionTreeSetCommitTsData(), TransferPredicateLocksToNewTarget(), TrimCLOG(), TrimMultiXact(), TruncateMultiXact(), TwoPhaseGetGXact(), UpdateMinRecoveryPoint(), vac_truncate_clog(), 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(), XLogBackgroundFlush(), and XLogReportParameters().

1209 {
1210  PGPROC *proc = MyProc;
1211  bool result = true;
1212  int extraWaits = 0;
1213 #ifdef LWLOCK_STATS
1214  lwlock_stats *lwstats;
1215 
1216  lwstats = get_lwlock_stats_entry(lock);
1217 #endif
1218 
1220 
1221  PRINT_LWDEBUG("LWLockAcquire", lock, mode);
1222 
1223 #ifdef LWLOCK_STATS
1224  /* Count lock acquisition attempts */
1225  if (mode == LW_EXCLUSIVE)
1226  lwstats->ex_acquire_count++;
1227  else
1228  lwstats->sh_acquire_count++;
1229 #endif /* LWLOCK_STATS */
1230 
1231  /*
1232  * We can't wait if we haven't got a PGPROC. This should only occur
1233  * during bootstrap or shared memory initialization. Put an Assert here
1234  * to catch unsafe coding practices.
1235  */
1236  Assert(!(proc == NULL && IsUnderPostmaster));
1237 
1238  /* Ensure we will have room to remember the lock */
1240  elog(ERROR, "too many LWLocks taken");
1241 
1242  /*
1243  * Lock out cancel/die interrupts until we exit the code section protected
1244  * by the LWLock. This ensures that interrupts will not interfere with
1245  * manipulations of data structures in shared memory.
1246  */
1247  HOLD_INTERRUPTS();
1248 
1249  /*
1250  * Loop here to try to acquire lock after each time we are signaled by
1251  * LWLockRelease.
1252  *
1253  * NOTE: it might seem better to have LWLockRelease actually grant us the
1254  * lock, rather than retrying and possibly having to go back to sleep. But
1255  * in practice that is no good because it means a process swap for every
1256  * lock acquisition when two or more processes are contending for the same
1257  * lock. Since LWLocks are normally used to protect not-very-long
1258  * sections of computation, a process needs to be able to acquire and
1259  * release the same lock many times during a single CPU time slice, even
1260  * in the presence of contention. The efficiency of being able to do that
1261  * outweighs the inefficiency of sometimes wasting a process dispatch
1262  * cycle because the lock is not free when a released waiter finally gets
1263  * to run. See pgsql-hackers archives for 29-Dec-01.
1264  */
1265  for (;;)
1266  {
1267  bool mustwait;
1268 
1269  /*
1270  * Try to grab the lock the first time, we're not in the waitqueue
1271  * yet/anymore.
1272  */
1273  mustwait = LWLockAttemptLock(lock, mode);
1274 
1275  if (!mustwait)
1276  {
1277  LOG_LWDEBUG("LWLockAcquire", lock, "immediately acquired lock");
1278  break; /* got the lock */
1279  }
1280 
1281  /*
1282  * Ok, at this point we couldn't grab the lock on the first try. We
1283  * cannot simply queue ourselves to the end of the list and wait to be
1284  * woken up because by now the lock could long have been released.
1285  * Instead add us to the queue and try to grab the lock again. If we
1286  * succeed we need to revert the queuing and be happy, otherwise we
1287  * recheck the lock. If we still couldn't grab it, we know that the
1288  * other locker will see our queue entries when releasing since they
1289  * existed before we checked for the lock.
1290  */
1291 
1292  /* add to the queue */
1293  LWLockQueueSelf(lock, mode);
1294 
1295  /* we're now guaranteed to be woken up if necessary */
1296  mustwait = LWLockAttemptLock(lock, mode);
1297 
1298  /* ok, grabbed the lock the second time round, need to undo queueing */
1299  if (!mustwait)
1300  {
1301  LOG_LWDEBUG("LWLockAcquire", lock, "acquired, undoing queue");
1302 
1303  LWLockDequeueSelf(lock);
1304  break;
1305  }
1306 
1307  /*
1308  * Wait until awakened.
1309  *
1310  * Since we share the process wait semaphore with the regular lock
1311  * manager and ProcWaitForSignal, and we may need to acquire an LWLock
1312  * while one of those is pending, it is possible that we get awakened
1313  * for a reason other than being signaled by LWLockRelease. If so,
1314  * loop back and wait again. Once we've gotten the LWLock,
1315  * re-increment the sema by the number of additional signals received,
1316  * so that the lock manager or signal manager will see the received
1317  * signal when it next waits.
1318  */
1319  LOG_LWDEBUG("LWLockAcquire", lock, "waiting");
1320 
1321 #ifdef LWLOCK_STATS
1322  lwstats->block_count++;
1323 #endif
1324 
1325  LWLockReportWaitStart(lock);
1326  TRACE_POSTGRESQL_LWLOCK_WAIT_START(T_NAME(lock), mode);
1327 
1328  for (;;)
1329  {
1330  PGSemaphoreLock(proc->sem);
1331  if (!proc->lwWaiting)
1332  break;
1333  extraWaits++;
1334  }
1335 
1336  /* Retrying, allow LWLockRelease to release waiters again. */
1338 
1339 #ifdef LOCK_DEBUG
1340  {
1341  /* not waiting anymore */
1342  uint32 nwaiters PG_USED_FOR_ASSERTS_ONLY = pg_atomic_fetch_sub_u32(&lock->nwaiters, 1);
1343 
1344  Assert(nwaiters < MAX_BACKENDS);
1345  }
1346 #endif
1347 
1348  TRACE_POSTGRESQL_LWLOCK_WAIT_DONE(T_NAME(lock), mode);
1350 
1351  LOG_LWDEBUG("LWLockAcquire", lock, "awakened");
1352 
1353  /* Now loop back and try to acquire lock again. */
1354  result = false;
1355  }
1356 
1357  TRACE_POSTGRESQL_LWLOCK_ACQUIRE(T_NAME(lock), mode);
1358 
1359  /* Add lock to list of locks held by this backend */
1362 
1363  /*
1364  * Fix the process wait semaphore's count for any absorbed wakeups.
1365  */
1366  while (extraWaits-- > 0)
1367  PGSemaphoreUnlock(proc->sem);
1368 
1369  return result;
1370 }
#define T_NAME(lock)
Definition: lwlock.c:248
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:826
void PGSemaphoreUnlock(PGSemaphore sema)
Definition: posix_sema.c:340
PGPROC * MyProc
Definition: proc.c:67
bool lwWaiting
Definition: proc.h:161
#define MAX_SIMUL_LWLOCKS
Definition: lwlock.c:208
pg_atomic_uint32 state
Definition: lwlock.h:34
static LWLockHandle held_lwlocks[MAX_SIMUL_LWLOCKS]
Definition: lwlock.c:218
#define ERROR
Definition: elog.h:43
#define MAX_BACKENDS
Definition: postmaster.h:75
LWLockMode mode
Definition: lwlock.c:214
bool IsUnderPostmaster
Definition: globals.c:109
static void LWLockReportWaitEnd(void)
Definition: lwlock.c:772
unsigned int uint32
Definition: c.h:374
static void LWLockDequeueSelf(LWLock *lock)
Definition: lwlock.c:1113
#define AssertArg(condition)
Definition: c.h:747
static void LWLockReportWaitStart(LWLock *lock)
Definition: lwlock.c:763
static void LWLockQueueSelf(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:1069
static int num_held_lwlocks
Definition: lwlock.c:217
#define Assert(condition)
Definition: c.h:745
LWLock * lock
Definition: lwlock.c:213
#define PRINT_LWDEBUG(a, b, c)
Definition: lwlock.c:312
#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:118
Definition: proc.h:112
#define PG_USED_FOR_ASSERTS_ONLY
Definition: c.h:121
#define LOG_LWDEBUG(a, b, c)
Definition: lwlock.c:313

◆ LWLockAcquireOrWait()

bool LWLockAcquireOrWait ( LWLock lock,
LWLockMode  mode 
)

Definition at line 1435 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().

1436 {
1437  PGPROC *proc = MyProc;
1438  bool mustwait;
1439  int extraWaits = 0;
1440 #ifdef LWLOCK_STATS
1441  lwlock_stats *lwstats;
1442 
1443  lwstats = get_lwlock_stats_entry(lock);
1444 #endif
1445 
1447 
1448  PRINT_LWDEBUG("LWLockAcquireOrWait", lock, mode);
1449 
1450  /* Ensure we will have room to remember the lock */
1452  elog(ERROR, "too many LWLocks taken");
1453 
1454  /*
1455  * Lock out cancel/die interrupts until we exit the code section protected
1456  * by the LWLock. This ensures that interrupts will not interfere with
1457  * manipulations of data structures in shared memory.
1458  */
1459  HOLD_INTERRUPTS();
1460 
1461  /*
1462  * NB: We're using nearly the same twice-in-a-row lock acquisition
1463  * protocol as LWLockAcquire(). Check its comments for details.
1464  */
1465  mustwait = LWLockAttemptLock(lock, mode);
1466 
1467  if (mustwait)
1468  {
1470 
1471  mustwait = LWLockAttemptLock(lock, mode);
1472 
1473  if (mustwait)
1474  {
1475  /*
1476  * Wait until awakened. Like in LWLockAcquire, be prepared for
1477  * bogus wakeups, because we share the semaphore with
1478  * ProcWaitForSignal.
1479  */
1480  LOG_LWDEBUG("LWLockAcquireOrWait", lock, "waiting");
1481 
1482 #ifdef LWLOCK_STATS
1483  lwstats->block_count++;
1484 #endif
1485 
1486  LWLockReportWaitStart(lock);
1487  TRACE_POSTGRESQL_LWLOCK_WAIT_START(T_NAME(lock), mode);
1488 
1489  for (;;)
1490  {
1491  PGSemaphoreLock(proc->sem);
1492  if (!proc->lwWaiting)
1493  break;
1494  extraWaits++;
1495  }
1496 
1497 #ifdef LOCK_DEBUG
1498  {
1499  /* not waiting anymore */
1500  uint32 nwaiters PG_USED_FOR_ASSERTS_ONLY = pg_atomic_fetch_sub_u32(&lock->nwaiters, 1);
1501 
1502  Assert(nwaiters < MAX_BACKENDS);
1503  }
1504 #endif
1505  TRACE_POSTGRESQL_LWLOCK_WAIT_DONE(T_NAME(lock), mode);
1507 
1508  LOG_LWDEBUG("LWLockAcquireOrWait", lock, "awakened");
1509  }
1510  else
1511  {
1512  LOG_LWDEBUG("LWLockAcquireOrWait", lock, "acquired, undoing queue");
1513 
1514  /*
1515  * Got lock in the second attempt, undo queueing. We need to treat
1516  * this as having successfully acquired the lock, otherwise we'd
1517  * not necessarily wake up people we've prevented from acquiring
1518  * the lock.
1519  */
1520  LWLockDequeueSelf(lock);
1521  }
1522  }
1523 
1524  /*
1525  * Fix the process wait semaphore's count for any absorbed wakeups.
1526  */
1527  while (extraWaits-- > 0)
1528  PGSemaphoreUnlock(proc->sem);
1529 
1530  if (mustwait)
1531  {
1532  /* Failed to get lock, so release interrupt holdoff */
1534  LOG_LWDEBUG("LWLockAcquireOrWait", lock, "failed");
1535  TRACE_POSTGRESQL_LWLOCK_ACQUIRE_OR_WAIT_FAIL(T_NAME(lock), mode);
1536  }
1537  else
1538  {
1539  LOG_LWDEBUG("LWLockAcquireOrWait", lock, "succeeded");
1540  /* Add lock to list of locks held by this backend */
1543  TRACE_POSTGRESQL_LWLOCK_ACQUIRE_OR_WAIT(T_NAME(lock), mode);
1544  }
1545 
1546  return !mustwait;
1547 }
#define T_NAME(lock)
Definition: lwlock.c:248
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:826
void PGSemaphoreUnlock(PGSemaphore sema)
Definition: posix_sema.c:340
PGPROC * MyProc
Definition: proc.c:67
bool lwWaiting
Definition: proc.h:161
#define MAX_SIMUL_LWLOCKS
Definition: lwlock.c:208
#define RESUME_INTERRUPTS()
Definition: miscadmin.h:118
static LWLockHandle held_lwlocks[MAX_SIMUL_LWLOCKS]
Definition: lwlock.c:218
#define ERROR
Definition: elog.h:43
#define MAX_BACKENDS
Definition: postmaster.h:75
LWLockMode mode
Definition: lwlock.c:214
static void LWLockReportWaitEnd(void)
Definition: lwlock.c:772
unsigned int uint32
Definition: c.h:374
static void LWLockDequeueSelf(LWLock *lock)
Definition: lwlock.c:1113
static void LWLockReportWaitStart(LWLock *lock)
Definition: lwlock.c:763
static void LWLockQueueSelf(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:1069
static int num_held_lwlocks
Definition: lwlock.c:217
#define Assert(condition)
Definition: c.h:745
LWLock * lock
Definition: lwlock.c:213
#define PRINT_LWDEBUG(a, b, c)
Definition: lwlock.c:312
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:118
Definition: proc.h:112
#define PG_USED_FOR_ASSERTS_ONLY
Definition: c.h:121
#define LOG_LWDEBUG(a, b, c)
Definition: lwlock.c:313

◆ LWLockAttemptLock()

static bool LWLockAttemptLock ( LWLock lock,
LWLockMode  mode 
)
static

Definition at line 826 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().

827 {
828  uint32 old_state;
829 
831 
832  /*
833  * Read once outside the loop, later iterations will get the newer value
834  * via compare & exchange.
835  */
836  old_state = pg_atomic_read_u32(&lock->state);
837 
838  /* loop until we've determined whether we could acquire the lock or not */
839  while (true)
840  {
841  uint32 desired_state;
842  bool lock_free;
843 
844  desired_state = old_state;
845 
846  if (mode == LW_EXCLUSIVE)
847  {
848  lock_free = (old_state & LW_LOCK_MASK) == 0;
849  if (lock_free)
850  desired_state += LW_VAL_EXCLUSIVE;
851  }
852  else
853  {
854  lock_free = (old_state & LW_VAL_EXCLUSIVE) == 0;
855  if (lock_free)
856  desired_state += LW_VAL_SHARED;
857  }
858 
859  /*
860  * Attempt to swap in the state we are expecting. If we didn't see
861  * lock to be free, that's just the old value. If we saw it as free,
862  * we'll attempt to mark it acquired. The reason that we always swap
863  * in the value is that this doubles as a memory barrier. We could try
864  * to be smarter and only swap in values if we saw the lock as free,
865  * but benchmark haven't shown it as beneficial so far.
866  *
867  * Retry if the value changed since we last looked at it.
868  */
870  &old_state, desired_state))
871  {
872  if (lock_free)
873  {
874  /* Great! Got the lock. */
875 #ifdef LOCK_DEBUG
876  if (mode == LW_EXCLUSIVE)
877  lock->owner = MyProc;
878 #endif
879  return false;
880  }
881  else
882  return true; /* somebody else has the lock */
883  }
884  }
885  pg_unreachable();
886 }
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:34
#define LW_LOCK_MASK
Definition: lwlock.c:106
#define LW_VAL_SHARED
Definition: lwlock.c:104
unsigned int uint32
Definition: c.h:374
#define AssertArg(condition)
Definition: c.h:747
#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 1380 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().

1381 {
1382  bool mustwait;
1383 
1385 
1386  PRINT_LWDEBUG("LWLockConditionalAcquire", lock, mode);
1387 
1388  /* Ensure we will have room to remember the lock */
1390  elog(ERROR, "too many LWLocks taken");
1391 
1392  /*
1393  * Lock out cancel/die interrupts until we exit the code section protected
1394  * by the LWLock. This ensures that interrupts will not interfere with
1395  * manipulations of data structures in shared memory.
1396  */
1397  HOLD_INTERRUPTS();
1398 
1399  /* Check for the lock */
1400  mustwait = LWLockAttemptLock(lock, mode);
1401 
1402  if (mustwait)
1403  {
1404  /* Failed to get lock, so release interrupt holdoff */
1406 
1407  LOG_LWDEBUG("LWLockConditionalAcquire", lock, "failed");
1408  TRACE_POSTGRESQL_LWLOCK_CONDACQUIRE_FAIL(T_NAME(lock), mode);
1409  }
1410  else
1411  {
1412  /* Add lock to list of locks held by this backend */
1415  TRACE_POSTGRESQL_LWLOCK_CONDACQUIRE(T_NAME(lock), mode);
1416  }
1417  return !mustwait;
1418 }
#define T_NAME(lock)
Definition: lwlock.c:248
static PgChecksumMode mode
Definition: pg_checksums.c:61
static bool LWLockAttemptLock(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:826
#define MAX_SIMUL_LWLOCKS
Definition: lwlock.c:208
#define RESUME_INTERRUPTS()
Definition: miscadmin.h:118
static LWLockHandle held_lwlocks[MAX_SIMUL_LWLOCKS]
Definition: lwlock.c:218
#define ERROR
Definition: elog.h:43
LWLockMode mode
Definition: lwlock.c:214
#define AssertArg(condition)
Definition: c.h:747
static int num_held_lwlocks
Definition: lwlock.c:217
LWLock * lock
Definition: lwlock.c:213
#define PRINT_LWDEBUG(a, b, c)
Definition: lwlock.c:312
#define HOLD_INTERRUPTS()
Definition: miscadmin.h:116
#define elog(elevel,...)
Definition: elog.h:214
#define LOG_LWDEBUG(a, b, c)
Definition: lwlock.c:313

◆ LWLockConflictsWithVar()

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

Definition at line 1559 of file lwlock.c.

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

Referenced by LWLockWaitForVar().

1562 {
1563  bool mustwait;
1564  uint64 value;
1565 
1566  /*
1567  * Test first to see if it the slot is free right now.
1568  *
1569  * XXX: the caller uses a spinlock before this, so we don't need a memory
1570  * barrier here as far as the current usage is concerned. But that might
1571  * not be safe in general.
1572  */
1573  mustwait = (pg_atomic_read_u32(&lock->state) & LW_VAL_EXCLUSIVE) != 0;
1574 
1575  if (!mustwait)
1576  {
1577  *result = true;
1578  return false;
1579  }
1580 
1581  *result = false;
1582 
1583  /*
1584  * Read value using the lwlock's wait list lock, as we can't generally
1585  * rely on atomic 64 bit reads/stores. TODO: On platforms with a way to
1586  * do atomic 64 bit reads/writes the spinlock should be optimized away.
1587  */
1588  LWLockWaitListLock(lock);
1589  value = *valptr;
1590  LWLockWaitListUnlock(lock);
1591 
1592  if (value != oldval)
1593  {
1594  mustwait = false;
1595  *newval = value;
1596  }
1597  else
1598  {
1599  mustwait = true;
1600  }
1601 
1602  return mustwait;
1603 }
static void LWLockWaitListUnlock(LWLock *lock)
Definition: lwlock.c:949
pg_atomic_uint32 state
Definition: lwlock.h:34
static struct @143 value
#define newval
static void LWLockWaitListLock(LWLock *lock)
Definition: lwlock.c:897
#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 1113 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().

1114 {
1115  bool found = false;
1116  proclist_mutable_iter iter;
1117 
1118 #ifdef LWLOCK_STATS
1119  lwlock_stats *lwstats;
1120 
1121  lwstats = get_lwlock_stats_entry(lock);
1122 
1123  lwstats->dequeue_self_count++;
1124 #endif
1125 
1126  LWLockWaitListLock(lock);
1127 
1128  /*
1129  * Can't just remove ourselves from the list, but we need to iterate over
1130  * all entries as somebody else could have dequeued us.
1131  */
1132  proclist_foreach_modify(iter, &lock->waiters, lwWaitLink)
1133  {
1134  if (iter.cur == MyProc->pgprocno)
1135  {
1136  found = true;
1137  proclist_delete(&lock->waiters, iter.cur, lwWaitLink);
1138  break;
1139  }
1140  }
1141 
1142  if (proclist_is_empty(&lock->waiters) &&
1143  (pg_atomic_read_u32(&lock->state) & LW_FLAG_HAS_WAITERS) != 0)
1144  {
1146  }
1147 
1148  /* XXX: combine with fetch_and above? */
1149  LWLockWaitListUnlock(lock);
1150 
1151  /* clear waiting state again, nice for debugging */
1152  if (found)
1153  MyProc->lwWaiting = false;
1154  else
1155  {
1156  int extraWaits = 0;
1157 
1158  /*
1159  * Somebody else dequeued us and has or will wake us up. Deal with the
1160  * superfluous absorption of a wakeup.
1161  */
1162 
1163  /*
1164  * Reset RELEASE_OK flag if somebody woke us before we removed
1165  * ourselves - they'll have set it to false.
1166  */
1168 
1169  /*
1170  * Now wait for the scheduled wakeup, otherwise our ->lwWaiting would
1171  * get reset at some inconvenient point later. Most of the time this
1172  * will immediately return.
1173  */
1174  for (;;)
1175  {
1177  if (!MyProc->lwWaiting)
1178  break;
1179  extraWaits++;
1180  }
1181 
1182  /*
1183  * Fix the process wait semaphore's count for any absorbed wakeups.
1184  */
1185  while (extraWaits-- > 0)
1187  }
1188 
1189 #ifdef LOCK_DEBUG
1190  {
1191  /* not waiting anymore */
1192  uint32 nwaiters PG_USED_FOR_ASSERTS_ONLY = pg_atomic_fetch_sub_u32(&lock->nwaiters, 1);
1193 
1194  Assert(nwaiters < MAX_BACKENDS);
1195  }
1196 #endif
1197 }
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:35
bool lwWaiting
Definition: proc.h:161
static void LWLockWaitListUnlock(LWLock *lock)
Definition: lwlock.c:949
#define proclist_foreach_modify(iter, lhead, link_member)
Definition: proclist.h:206
pg_atomic_uint32 state
Definition: lwlock.h:34
#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:374
#define Assert(condition)
Definition: c.h:745
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:897
int pgprocno
Definition: proc.h:141
static uint32 pg_atomic_fetch_or_u32(volatile pg_atomic_uint32 *ptr, uint32 or_)
Definition: atomics.h:372
PGSemaphore sem
Definition: proc.h:118
#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 1946 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(), SearchNamedReplicationSlot(), SyncRepWakeQueue(), TransactionIdSetPageStatusInternal(), and TransferPredicateLocksToNewTarget().

1947 {
1948  int i;
1949 
1950  for (i = 0; i < num_held_lwlocks; i++)
1951  {
1952  if (held_lwlocks[i].lock == l && held_lwlocks[i].mode == mode)
1953  return true;
1954  }
1955  return false;
1956 }
static PgChecksumMode mode
Definition: pg_checksums.c:61
static LWLockHandle held_lwlocks[MAX_SIMUL_LWLOCKS]
Definition: lwlock.c:218
static int num_held_lwlocks
Definition: lwlock.c:217
int i

◆ LWLockInitialize()

void LWLockInitialize ( LWLock lock,
int  tranche_id 
)

Definition at line 745 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().

746 {
748 #ifdef LOCK_DEBUG
749  pg_atomic_init_u32(&lock->nwaiters, 0);
750 #endif
751  lock->tranche = tranche_id;
752  proclist_init(&lock->waiters);
753 }
proclist_head waiters
Definition: lwlock.h:35
pg_atomic_uint32 state
Definition: lwlock.h:34
uint16 tranche
Definition: lwlock.h:33
#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 629 of file lwlock.c.

References ShmemLock, SpinLockAcquire, and SpinLockRelease.

Referenced by apw_init_shmem(), and InitializeLWLocks().

630 {
631  int result;
632  int *LWLockCounter;
633 
634  LWLockCounter = (int *) ((char *) MainLWLockArray - sizeof(int));
636  result = (*LWLockCounter)++;
638 
639  return result;
640 }
#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:200

◆ LWLockQueueSelf()

static void LWLockQueueSelf ( LWLock lock,
LWLockMode  mode 
)
static

Definition at line 1069 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().

1070 {
1071  /*
1072  * If we don't have a PGPROC structure, there's no way to wait. This
1073  * should never occur, since MyProc should only be null during shared
1074  * memory initialization.
1075  */
1076  if (MyProc == NULL)
1077  elog(PANIC, "cannot wait without a PGPROC structure");
1078 
1079  if (MyProc->lwWaiting)
1080  elog(PANIC, "queueing for lock while waiting on another one");
1081 
1082  LWLockWaitListLock(lock);
1083 
1084  /* setting the flag is protected by the spinlock */
1086 
1087  MyProc->lwWaiting = true;
1088  MyProc->lwWaitMode = mode;
1089 
1090  /* LW_WAIT_UNTIL_FREE waiters are always at the front of the queue */
1091  if (mode == LW_WAIT_UNTIL_FREE)
1092  proclist_push_head(&lock->waiters, MyProc->pgprocno, lwWaitLink);
1093  else
1094  proclist_push_tail(&lock->waiters, MyProc->pgprocno, lwWaitLink);
1095 
1096  /* Can release the mutex now */
1097  LWLockWaitListUnlock(lock);
1098 
1099 #ifdef LOCK_DEBUG
1100  pg_atomic_fetch_add_u32(&lock->nwaiters, 1);
1101 #endif
1102 
1103 }
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:35
bool lwWaiting
Definition: proc.h:161
static void LWLockWaitListUnlock(LWLock *lock)
Definition: lwlock.c:949
uint8 lwWaitMode
Definition: proc.h:162
pg_atomic_uint32 state
Definition: lwlock.h:34
#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:897
int pgprocno
Definition: proc.h:141
#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 653 of file lwlock.c.

References LWLockTrancheNames, LWLockTrancheNamesAllocated, LWTRANCHE_FIRST_USER_DEFINED, Max, MemoryContextAllocZero(), repalloc(), and TopMemoryContext.

Referenced by apw_init_shmem(), and CreateLWLocks().

654 {
655  /* This should only be called for user-defined tranches. */
656  if (tranche_id < LWTRANCHE_FIRST_USER_DEFINED)
657  return;
658 
659  /* Convert to array index. */
660  tranche_id -= LWTRANCHE_FIRST_USER_DEFINED;
661 
662  /* If necessary, create or enlarge array. */
663  if (tranche_id >= LWLockTrancheNamesAllocated)
664  {
665  int newalloc;
666 
667  newalloc = Max(LWLockTrancheNamesAllocated, 8);
668  while (newalloc <= tranche_id)
669  newalloc *= 2;
670 
671  if (LWLockTrancheNames == NULL)
672  LWLockTrancheNames = (const char **)
674  newalloc * sizeof(char *));
675  else
676  {
677  LWLockTrancheNames = (const char **)
678  repalloc(LWLockTrancheNames, newalloc * sizeof(char *));
680  0,
681  (newalloc - LWLockTrancheNamesAllocated) * sizeof(char *));
682  }
683  LWLockTrancheNamesAllocated = newalloc;
684  }
685 
686  LWLockTrancheNames[tranche_id] = tranche_name;
687 }
static int LWLockTrancheNamesAllocated
Definition: lwlock.c:193
MemoryContext TopMemoryContext
Definition: mcxt.c:44
void * MemoryContextAllocZero(MemoryContext context, Size size)
Definition: mcxt.c:840
#define Max(x, y)
Definition: c.h:921
void * repalloc(void *pointer, Size size)
Definition: mcxt.c:1070
static const char ** LWLockTrancheNames
Definition: lwlock.c:192

◆ LWLockRelease()

void LWLockRelease ( LWLock lock)

Definition at line 1812 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(), ApplyLauncherMain(), apw_detach_shmem(), apw_dump_now(), apw_init_shmem(), apw_load_buffers(), asyncQueueAddEntries(), asyncQueueAdvanceTail(), asyncQueueReadAllNotifications(), asyncQueueUnregister(), 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(), ComputeXidHorizons(), 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(), FlushRelationsAllBuffers(), ForceTransactionIdLimitUpdate(), ForwardSyncRequest(), FreeWorkerInfo(), GetBackgroundWorkerPid(), GetBackgroundWorkerTypeByPid(), GetBlockerStatusData(), GetConflictingVirtualXIDs(), GetCurrentVirtualXIDs(), GetLastImportantRecPtr(), GetLastSegSwitchData(), GetLatestCommitTsData(), GetLockConflicts(), GetLockStatusData(), GetMultiXactIdMembers(), GetNewMultiXactId(), GetNewObjectId(), GetNewTransactionId(), GetOldestActiveTransactionId(), GetOldestMultiXactId(), GetOldestRestartPoint(), GetOldestSafeDecodingTransactionId(), GetOldSnapshotFromTimeMapping(), GetOldSnapshotTimeMapping(), GetPredicateLockStatusData(), GetPreparedTransactionList(), GetRunningTransactionLocks(), GetSafeSnapshot(), GetSafeSnapshotBlockingPids(), GetSerializableTransactionSnapshotInt(), GetSnapshotData(), GetVirtualXIDsDelayingChkpt(), HandleAutoVacLauncherInterrupts(), HaveVirtualXIDsDelayingChkpt(), InstallXLogFileSegment(), InvalidateBuffer(), InvalidateObsoleteReplicationSlots(), 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(), 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_statements_internal(), pg_xact_status(), pgss_shmem_startup(), pgss_store(), PostPrepare_Locks(), PostPrepare_MultiXact(), PostPrepare_Twophase(), PreCommit_CheckForSerializationFailure(), PreCommit_Notify(), predicatelock_twophase_recover(), PredicateLockPageSplit(), PredicateLockTwoPhaseFinish(), PrefetchSharedBuffer(), PrescanPreparedTransactions(), ProcArrayAdd(), ProcArrayApplyRecoveryInfo(), ProcArrayApplyXidAssignment(), ProcArrayClearTransaction(), 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(), ReplicationSlotAcquireInternal(), 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(), SerialAdd(), SerialGetMinConflictCommitSeqNo(), SerialSetActiveSerXmin(), SetCommitTsLimit(), SetMultiXactIdLimit(), SetOffsetVacuumLimit(), SetTransactionIdLimit(), SetXidCommitTsInPage(), SharedInvalBackendInit(), ShmemInitStruct(), SICleanupQueue(), SIGetDataEntries(), SignalBackends(), SIInsertDataEntries(), SimpleLruReadPage(), SimpleLruReadPage_ReadOnly(), SimpleLruTruncate(), SimpleLruWaitIO(), SimpleLruWriteAll(), 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(), SyncRepReleaseWaiters(), SyncRepUpdateSyncStandbysDefined(), SyncRepWaitForLSN(), TablespaceCreateDbspace(), tbm_shared_iterate(), TerminateBackgroundWorker(), TerminateBufferIO(), TerminateOtherDBBackends(), TransactionGroupUpdateXidStatus(), TransactionIdGetCommitTsData(), TransactionIdGetStatus(), TransactionIdIsActive(), TransactionIdIsInProgress(), TransactionIdSetPageStatus(), TransactionTreeSetCommitTsData(), TransferPredicateLocksToNewTarget(), TrimCLOG(), TrimMultiXact(), TruncateMultiXact(), TwoPhaseGetGXact(), UpdateMinRecoveryPoint(), vac_truncate_clog(), 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(), XLogNeedsFlush(), and XLogReportParameters().

1813 {
1814  LWLockMode mode;
1815  uint32 oldstate;
1816  bool check_waiters;
1817  int i;
1818 
1819  /*
1820  * Remove lock from list of locks held. Usually, but not always, it will
1821  * be the latest-acquired lock; so search array backwards.
1822  */
1823  for (i = num_held_lwlocks; --i >= 0;)
1824  if (lock == held_lwlocks[i].lock)
1825  break;
1826 
1827  if (i < 0)
1828  elog(ERROR, "lock %s is not held", T_NAME(lock));
1829 
1830  mode = held_lwlocks[i].mode;
1831 
1832  num_held_lwlocks--;
1833  for (; i < num_held_lwlocks; i++)
1834  held_lwlocks[i] = held_lwlocks[i + 1];
1835 
1836  PRINT_LWDEBUG("LWLockRelease", lock, mode);
1837 
1838  /*
1839  * Release my hold on lock, after that it can immediately be acquired by
1840  * others, even if we still have to wakeup other waiters.
1841  */
1842  if (mode == LW_EXCLUSIVE)
1843  oldstate = pg_atomic_sub_fetch_u32(&lock->state, LW_VAL_EXCLUSIVE);
1844  else
1845  oldstate = pg_atomic_sub_fetch_u32(&lock->state, LW_VAL_SHARED);
1846 
1847  /* nobody else can have that kind of lock */
1848  Assert(!(oldstate & LW_VAL_EXCLUSIVE));
1849 
1850 
1851  /*
1852  * We're still waiting for backends to get scheduled, don't wake them up
1853  * again.
1854  */
1855  if ((oldstate & (LW_FLAG_HAS_WAITERS | LW_FLAG_RELEASE_OK)) ==
1857  (oldstate & LW_LOCK_MASK) == 0)
1858  check_waiters = true;
1859  else
1860  check_waiters = false;
1861 
1862  /*
1863  * As waking up waiters requires the spinlock to be acquired, only do so
1864  * if necessary.
1865  */
1866  if (check_waiters)
1867  {
1868  /* XXX: remove before commit? */
1869  LOG_LWDEBUG("LWLockRelease", lock, "releasing waiters");
1870  LWLockWakeup(lock);
1871  }
1872 
1873  TRACE_POSTGRESQL_LWLOCK_RELEASE(T_NAME(lock));
1874 
1875  /*
1876  * Now okay to allow cancel/die interrupts.
1877  */
1879 }
#define T_NAME(lock)
Definition: lwlock.c:248
static PgChecksumMode mode
Definition: pg_checksums.c:61
LWLockMode
Definition: lwlock.h:130
#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:218
#define ERROR
Definition: elog.h:43
LWLockMode mode
Definition: lwlock.c:214
static void LWLockWakeup(LWLock *lock)
Definition: lwlock.c:962
unsigned int uint32
Definition: c.h:374
static int num_held_lwlocks
Definition: lwlock.c:217
#define Assert(condition)
Definition: c.h:745
#define PRINT_LWDEBUG(a, b, c)
Definition: lwlock.c:312
#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:313

◆ LWLockReleaseAll()

void LWLockReleaseAll ( void  )

Definition at line 1911 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().

1912 {
1913  while (num_held_lwlocks > 0)
1914  {
1915  HOLD_INTERRUPTS(); /* match the upcoming RESUME_INTERRUPTS */
1916 
1918  }
1919 }
void LWLockRelease(LWLock *lock)
Definition: lwlock.c:1812
static LWLockHandle held_lwlocks[MAX_SIMUL_LWLOCKS]
Definition: lwlock.c:218
static int num_held_lwlocks
Definition: lwlock.c:217
#define HOLD_INTERRUPTS()
Definition: miscadmin.h:116

◆ LWLockReleaseClearVar()

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

Definition at line 1885 of file lwlock.c.

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

Referenced by WALInsertLockRelease().

1886 {
1887  LWLockWaitListLock(lock);
1888 
1889  /*
1890  * Set the variable's value before releasing the lock, that prevents race
1891  * a race condition wherein a new locker acquires the lock, but hasn't yet
1892  * set the variables value.
1893  */
1894  *valptr = val;
1895  LWLockWaitListUnlock(lock);
1896 
1897  LWLockRelease(lock);
1898 }
static void LWLockWaitListUnlock(LWLock *lock)
Definition: lwlock.c:949
void LWLockRelease(LWLock *lock)
Definition: lwlock.c:1812
static void LWLockWaitListLock(LWLock *lock)
Definition: lwlock.c:897
long val
Definition: informix.c:664

◆ LWLockReportWaitEnd()

static void LWLockReportWaitEnd ( void  )
inlinestatic

Definition at line 772 of file lwlock.c.

References pgstat_report_wait_end().

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

773 {
775 }
static void pgstat_report_wait_end(void)
Definition: pgstat.h:1386

◆ LWLockReportWaitStart()

static void LWLockReportWaitStart ( LWLock lock)
inlinestatic

Definition at line 763 of file lwlock.c.

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

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

764 {
766 }
uint16 tranche
Definition: lwlock.h:33
static void pgstat_report_wait_start(uint32 wait_event_info)
Definition: pgstat.h:1362
#define PG_WAIT_LWLOCK
Definition: pgstat.h:784

◆ LWLockShmemSize()

Size LWLockShmemSize ( void  )

Definition at line 435 of file lwlock.c.

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

Referenced by CreateLWLocks(), and CreateSharedMemoryAndSemaphores().

436 {
437  Size size;
438  int i;
439  int numLocks = NUM_FIXED_LWLOCKS;
440 
441  /* Calculate total number of locks needed in the main array. */
442  numLocks += NumLWLocksForNamedTranches();
443 
444  /* Space for the LWLock array. */
445  size = mul_size(numLocks, sizeof(LWLockPadded));
446 
447  /* Space for dynamic allocation counter, plus room for alignment. */
448  size = add_size(size, sizeof(int) + LWLOCK_PADDED_SIZE);
449 
450  /* space for named tranches. */
452 
453  /* space for name of each tranche. */
454  for (i = 0; i < NamedLWLockTrancheRequests; i++)
455  size = add_size(size, strlen(NamedLWLockTrancheRequestArray[i].tranche_name) + 1);
456 
457  /* Disallow adding any more named tranches. */
459 
460  return size;
461 }
static bool lock_named_request_allowed
Definition: lwlock.c:241
#define NUM_FIXED_LWLOCKS
Definition: lwlock.h:127
int NamedLWLockTrancheRequests
Definition: lwlock.c:236
static int NumLWLocksForNamedTranches(void)
Definition: lwlock.c:420
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:473
static NamedLWLockTrancheRequest * NamedLWLockTrancheRequestArray
Definition: lwlock.c:227
int i
#define LWLOCK_PADDED_SIZE
Definition: lwlock.h:72

◆ LWLockUpdateVar()

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

Definition at line 1758 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().

1759 {
1760  proclist_head wakeup;
1761  proclist_mutable_iter iter;
1762 
1763  PRINT_LWDEBUG("LWLockUpdateVar", lock, LW_EXCLUSIVE);
1764 
1765  proclist_init(&wakeup);
1766 
1767  LWLockWaitListLock(lock);
1768 
1770 
1771  /* Update the lock's value */
1772  *valptr = val;
1773 
1774  /*
1775  * See if there are any LW_WAIT_UNTIL_FREE waiters that need to be woken
1776  * up. They are always in the front of the queue.
1777  */
1778  proclist_foreach_modify(iter, &lock->waiters, lwWaitLink)
1779  {
1780  PGPROC *waiter = GetPGProcByNumber(iter.cur);
1781 
1782  if (waiter->lwWaitMode != LW_WAIT_UNTIL_FREE)
1783  break;
1784 
1785  proclist_delete(&lock->waiters, iter.cur, lwWaitLink);
1786  proclist_push_tail(&wakeup, iter.cur, lwWaitLink);
1787  }
1788 
1789  /* We are done updating shared state of the lock itself. */
1790  LWLockWaitListUnlock(lock);
1791 
1792  /*
1793  * Awaken any waiters I removed from the queue.
1794  */
1795  proclist_foreach_modify(iter, &wakeup, lwWaitLink)
1796  {
1797  PGPROC *waiter = GetPGProcByNumber(iter.cur);
1798 
1799  proclist_delete(&wakeup, iter.cur, lwWaitLink);
1800  /* check comment in LWLockWakeup() about this barrier */
1801  pg_write_barrier();
1802  waiter->lwWaiting = false;
1803  PGSemaphoreUnlock(waiter->sem);
1804  }
1805 }
#define GetPGProcByNumber(n)
Definition: proc.h:355
void PGSemaphoreUnlock(PGSemaphore sema)
Definition: posix_sema.c:340
proclist_head waiters
Definition: lwlock.h:35
bool lwWaiting
Definition: proc.h:161
static void LWLockWaitListUnlock(LWLock *lock)
Definition: lwlock.c:949
#define proclist_foreach_modify(iter, lhead, link_member)
Definition: proclist.h:206
uint8 lwWaitMode
Definition: proc.h:162
pg_atomic_uint32 state
Definition: lwlock.h:34
#define proclist_delete(list, procno, link_member)
Definition: proclist.h:187
#define Assert(condition)
Definition: c.h:745
#define PRINT_LWDEBUG(a, b, c)
Definition: lwlock.c:312
#define proclist_push_tail(list, procno, link_member)
Definition: proclist.h:191
static void LWLockWaitListLock(LWLock *lock)
Definition: lwlock.c:897
#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:118
Definition: proc.h:112
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 1619 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().

1620 {
1621  PGPROC *proc = MyProc;
1622  int extraWaits = 0;
1623  bool result = false;
1624 #ifdef LWLOCK_STATS
1625  lwlock_stats *lwstats;
1626 
1627  lwstats = get_lwlock_stats_entry(lock);
1628 #endif
1629 
1630  PRINT_LWDEBUG("LWLockWaitForVar", lock, LW_WAIT_UNTIL_FREE);
1631 
1632  /*
1633  * Lock out cancel/die interrupts while we sleep on the lock. There is no
1634  * cleanup mechanism to remove us from the wait queue if we got
1635  * interrupted.
1636  */
1637  HOLD_INTERRUPTS();
1638 
1639  /*
1640  * Loop here to check the lock's status after each time we are signaled.
1641  */
1642  for (;;)
1643  {
1644  bool mustwait;
1645 
1646  mustwait = LWLockConflictsWithVar(lock, valptr, oldval, newval,
1647  &result);
1648 
1649  if (!mustwait)
1650  break; /* the lock was free or value didn't match */
1651 
1652  /*
1653  * Add myself to wait queue. Note that this is racy, somebody else
1654  * could wakeup before we're finished queuing. NB: We're using nearly
1655  * the same twice-in-a-row lock acquisition protocol as
1656  * LWLockAcquire(). Check its comments for details. The only
1657  * difference is that we also have to check the variable's values when
1658  * checking the state of the lock.
1659  */
1661 
1662  /*
1663  * Set RELEASE_OK flag, to make sure we get woken up as soon as the
1664  * lock is released.
1665  */
1667 
1668  /*
1669  * We're now guaranteed to be woken up if necessary. Recheck the lock
1670  * and variables state.
1671  */
1672  mustwait = LWLockConflictsWithVar(lock, valptr, oldval, newval,
1673  &result);
1674 
1675  /* Ok, no conflict after we queued ourselves. Undo queueing. */
1676  if (!mustwait)
1677  {
1678  LOG_LWDEBUG("LWLockWaitForVar", lock, "free, undoing queue");
1679 
1680  LWLockDequeueSelf(lock);
1681  break;
1682  }
1683 
1684  /*
1685  * Wait until awakened.
1686  *
1687  * Since we share the process wait semaphore with the regular lock
1688  * manager and ProcWaitForSignal, and we may need to acquire an LWLock
1689  * while one of those is pending, it is possible that we get awakened
1690  * for a reason other than being signaled by LWLockRelease. If so,
1691  * loop back and wait again. Once we've gotten the LWLock,
1692  * re-increment the sema by the number of additional signals received,
1693  * so that the lock manager or signal manager will see the received
1694  * signal when it next waits.
1695  */
1696  LOG_LWDEBUG("LWLockWaitForVar", lock, "waiting");
1697 
1698 #ifdef LWLOCK_STATS
1699  lwstats->block_count++;
1700 #endif
1701 
1702  LWLockReportWaitStart(lock);
1703  TRACE_POSTGRESQL_LWLOCK_WAIT_START(T_NAME(lock), LW_EXCLUSIVE);
1704 
1705  for (;;)
1706  {
1707  PGSemaphoreLock(proc->sem);
1708  if (!proc->lwWaiting)
1709  break;
1710  extraWaits++;
1711  }
1712 
1713 #ifdef LOCK_DEBUG
1714  {
1715  /* not waiting anymore */
1716  uint32 nwaiters PG_USED_FOR_ASSERTS_ONLY = pg_atomic_fetch_sub_u32(&lock->nwaiters, 1);
1717 
1718  Assert(nwaiters < MAX_BACKENDS);
1719  }
1720 #endif
1721 
1722  TRACE_POSTGRESQL_LWLOCK_WAIT_DONE(T_NAME(lock), LW_EXCLUSIVE);
1724 
1725  LOG_LWDEBUG("LWLockWaitForVar", lock, "awakened");
1726 
1727  /* Now loop back and check the status of the lock again. */
1728  }
1729 
1730  TRACE_POSTGRESQL_LWLOCK_ACQUIRE(T_NAME(lock), LW_EXCLUSIVE);
1731 
1732  /*
1733  * Fix the process wait semaphore's count for any absorbed wakeups.
1734  */
1735  while (extraWaits-- > 0)
1736  PGSemaphoreUnlock(proc->sem);
1737 
1738  /*
1739  * Now okay to allow cancel/die interrupts.
1740  */
1742 
1743  return result;
1744 }
#define T_NAME(lock)
Definition: lwlock.c:248
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:161
pg_atomic_uint32 state
Definition: lwlock.h:34
#define RESUME_INTERRUPTS()
Definition: miscadmin.h:118
#define MAX_BACKENDS
Definition: postmaster.h:75
static void LWLockReportWaitEnd(void)
Definition: lwlock.c:772
unsigned int uint32
Definition: c.h:374
static void LWLockDequeueSelf(LWLock *lock)
Definition: lwlock.c:1113
static void LWLockReportWaitStart(LWLock *lock)
Definition: lwlock.c:763
static void LWLockQueueSelf(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:1069
#define Assert(condition)
Definition: c.h:745
#define newval
#define PRINT_LWDEBUG(a, b, c)
Definition: lwlock.c:312
#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:1559
#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:118
Definition: proc.h:112
#define PG_USED_FOR_ASSERTS_ONLY
Definition: c.h:121
#define LOG_LWDEBUG(a, b, c)
Definition: lwlock.c:313

◆ LWLockWaitListLock()

static void LWLockWaitListLock ( LWLock lock)
static

Definition at line 897 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().

898 {
899  uint32 old_state;
900 #ifdef LWLOCK_STATS
901  lwlock_stats *lwstats;
902  uint32 delays = 0;
903 
904  lwstats = get_lwlock_stats_entry(lock);
905 #endif
906 
907  while (true)
908  {
909  /* always try once to acquire lock directly */
910  old_state = pg_atomic_fetch_or_u32(&lock->state, LW_FLAG_LOCKED);
911  if (!(old_state & LW_FLAG_LOCKED))
912  break; /* got lock */
913 
914  /* and then spin without atomic operations until lock is released */
915  {
916  SpinDelayStatus delayStatus;
917 
918  init_local_spin_delay(&delayStatus);
919 
920  while (old_state & LW_FLAG_LOCKED)
921  {
922  perform_spin_delay(&delayStatus);
923  old_state = pg_atomic_read_u32(&lock->state);
924  }
925 #ifdef LWLOCK_STATS
926  delays += delayStatus.delays;
927 #endif
928  finish_spin_delay(&delayStatus);
929  }
930 
931  /*
932  * Retry. The lock might obviously already be re-acquired by the time
933  * we're attempting to get it again.
934  */
935  }
936 
937 #ifdef LWLOCK_STATS
938  lwstats->spin_delay_count += delays;
939 #endif
940 }
#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:34
void finish_spin_delay(SpinDelayStatus *status)
Definition: s_lock.c:174
unsigned int uint32
Definition: c.h:374
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 949 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().

950 {
952 
953  old_state = pg_atomic_fetch_and_u32(&lock->state, ~LW_FLAG_LOCKED);
954 
955  Assert(old_state & LW_FLAG_LOCKED);
956 }
#define LW_FLAG_LOCKED
Definition: lwlock.c:101
pg_atomic_uint32 state
Definition: lwlock.h:34
static uint32 pg_atomic_fetch_and_u32(volatile pg_atomic_uint32 *ptr, uint32 and_)
Definition: atomics.h:358
unsigned int uint32
Definition: c.h:374
#define Assert(condition)
Definition: c.h:745
#define PG_USED_FOR_ASSERTS_ONLY
Definition: c.h:121

◆ LWLockWakeup()

static void LWLockWakeup ( LWLock lock)
static

Definition at line 962 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().

963 {
964  bool new_release_ok;
965  bool wokeup_somebody = false;
966  proclist_head wakeup;
968 
969  proclist_init(&wakeup);
970 
971  new_release_ok = true;
972 
973  /* lock wait list while collecting backends to wake up */
974  LWLockWaitListLock(lock);
975 
976  proclist_foreach_modify(iter, &lock->waiters, lwWaitLink)
977  {
978  PGPROC *waiter = GetPGProcByNumber(iter.cur);
979 
980  if (wokeup_somebody && waiter->lwWaitMode == LW_EXCLUSIVE)
981  continue;
982 
983  proclist_delete(&lock->waiters, iter.cur, lwWaitLink);
984  proclist_push_tail(&wakeup, iter.cur, lwWaitLink);
985 
986  if (waiter->lwWaitMode != LW_WAIT_UNTIL_FREE)
987  {
988  /*
989  * Prevent additional wakeups until retryer gets to run. Backends
990  * that are just waiting for the lock to become free don't retry
991  * automatically.
992  */
993  new_release_ok = false;
994 
995  /*
996  * Don't wakeup (further) exclusive locks.
997  */
998  wokeup_somebody = true;
999  }
1000 
1001  /*
1002  * Once we've woken up an exclusive lock, there's no point in waking
1003  * up anybody else.
1004  */
1005  if (waiter->lwWaitMode == LW_EXCLUSIVE)
1006  break;
1007  }
1008 
1010 
1011  /* unset required flags, and release lock, in one fell swoop */
1012  {
1013  uint32 old_state;
1014  uint32 desired_state;
1015 
1016  old_state = pg_atomic_read_u32(&lock->state);
1017  while (true)
1018  {
1019  desired_state = old_state;
1020 
1021  /* compute desired flags */
1022 
1023  if (new_release_ok)
1024  desired_state |= LW_FLAG_RELEASE_OK;
1025  else
1026  desired_state &= ~LW_FLAG_RELEASE_OK;
1027 
1028  if (proclist_is_empty(&wakeup))
1029  desired_state &= ~LW_FLAG_HAS_WAITERS;
1030 
1031  desired_state &= ~LW_FLAG_LOCKED; /* release lock */
1032 
1033  if (pg_atomic_compare_exchange_u32(&lock->state, &old_state,
1034  desired_state))
1035  break;
1036  }
1037  }
1038 
1039  /* Awaken any waiters I removed from the queue. */
1040  proclist_foreach_modify(iter, &wakeup, lwWaitLink)
1041  {
1042  PGPROC *waiter = GetPGProcByNumber(iter.cur);
1043 
1044  LOG_LWDEBUG("LWLockRelease", lock, "release waiter");
1045  proclist_delete(&wakeup, iter.cur, lwWaitLink);
1046 
1047  /*
1048  * Guarantee that lwWaiting being unset only becomes visible once the
1049  * unlink from the link has completed. Otherwise the target backend
1050  * could be woken up for other reason and enqueue for a new lock - if
1051  * that happens before the list unlink happens, the list would end up
1052  * being corrupted.
1053  *
1054  * The barrier pairs with the LWLockWaitListLock() when enqueuing for
1055  * another lock.
1056  */
1057  pg_write_barrier();
1058  waiter->lwWaiting = false;
1059  PGSemaphoreUnlock(waiter->sem);
1060  }
1061 }
#define GetPGProcByNumber(n)
Definition: proc.h:355
#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:35
bool lwWaiting
Definition: proc.h:161
#define proclist_foreach_modify(iter, lhead, link_member)
Definition: proclist.h:206
uint8 lwWaitMode
Definition: proc.h:162
pg_atomic_uint32 state
Definition: lwlock.h:34
#define proclist_delete(list, procno, link_member)
Definition: proclist.h:187
unsigned int uint32
Definition: c.h:374
#define Assert(condition)
Definition: c.h:745
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:897
static void proclist_init(proclist_head *list)
Definition: proclist.h:29
#define pg_write_barrier()
Definition: atomics.h:159
PGSemaphore sem
Definition: proc.h:118
Definition: proc.h:112
static uint32 pg_atomic_read_u32(volatile pg_atomic_uint32 *ptr)
Definition: atomics.h:241
#define LOG_LWDEBUG(a, b, c)
Definition: lwlock.c:313

◆ NumLWLocksForNamedTranches()

static int NumLWLocksForNamedTranches ( void  )
static

Definition at line 420 of file lwlock.c.

References i, and NamedLWLockTrancheRequests.

Referenced by InitializeLWLocks(), and LWLockShmemSize().

421 {
422  int numLocks = 0;
423  int i;
424 
425  for (i = 0; i < NamedLWLockTrancheRequests; i++)
426  numLocks += NamedLWLockTrancheRequestArray[i].num_lwlocks;
427 
428  return numLocks;
429 }
int NamedLWLockTrancheRequests
Definition: lwlock.c:236
static NamedLWLockTrancheRequest * NamedLWLockTrancheRequestArray
Definition: lwlock.c:227
int i

◆ RequestNamedLWLockTranche()

void RequestNamedLWLockTranche ( const char *  tranche_name,
int  num_lwlocks 
)

Definition at line 705 of file lwlock.c.

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

Referenced by _PG_init().

706 {
707  NamedLWLockTrancheRequest *request;
708 
710  return; /* too late */
711 
712  if (NamedLWLockTrancheRequestArray == NULL)
713  {
718  * sizeof(NamedLWLockTrancheRequest));
719  }
720 
722  {
724 
725  while (i <= NamedLWLockTrancheRequests)
726  i *= 2;
727 
730  i * sizeof(NamedLWLockTrancheRequest));
732  }
733 
735  Assert(strlen(tranche_name) + 1 <= NAMEDATALEN);
736  strlcpy(request->tranche_name, tranche_name, NAMEDATALEN);
737  request->num_lwlocks = num_lwlocks;
739 }
static bool lock_named_request_allowed
Definition: lwlock.c:241
char tranche_name[NAMEDATALEN]
Definition: lwlock.c:223
#define NAMEDATALEN
int NamedLWLockTrancheRequests
Definition: lwlock.c:236
bool IsUnderPostmaster
Definition: globals.c:109
MemoryContext TopMemoryContext
Definition: mcxt.c:44
static int NamedLWLockTrancheRequestsAllocated
Definition: lwlock.c:228
size_t strlcpy(char *dst, const char *src, size_t siz)
Definition: strlcpy.c:45
#define Assert(condition)
Definition: c.h:745
void * repalloc(void *pointer, Size size)
Definition: mcxt.c:1070
static NamedLWLockTrancheRequest * NamedLWLockTrancheRequestArray
Definition: lwlock.c:227
void * MemoryContextAlloc(MemoryContext context, Size size)
Definition: mcxt.c:797
int i

◆ StaticAssertDecl()

StaticAssertDecl ( lengthof(BuiltinTrancheNames = =LWTRANCHE_FIRST_USER_DEFINED - NUM_INDIVIDUAL_LWLOCKS,
"missing entries in BuiltinTrancheNames [] 
)

Variable Documentation

◆ BuiltinTrancheNames

const char* const BuiltinTrancheNames[]
static

Definition at line 130 of file lwlock.c.

Referenced by GetLWTrancheName().

◆ held_lwlocks

LWLockHandle held_lwlocks[MAX_SIMUL_LWLOCKS]
static

Definition at line 218 of file lwlock.c.

◆ IndividualLWLockNames

const char* const IndividualLWLockNames[]

Referenced by GetLWTrancheName().

◆ lock_named_request_allowed

bool lock_named_request_allowed = true
static

Definition at line 241 of file lwlock.c.

Referenced by LWLockShmemSize(), and RequestNamedLWLockTranche().

◆ LWLockTrancheNames

const char** LWLockTrancheNames = NULL
static

Definition at line 192 of file lwlock.c.

Referenced by GetLWTrancheName(), and LWLockRegisterTranche().

◆ LWLockTrancheNamesAllocated

int LWLockTrancheNamesAllocated = 0
static

Definition at line 193 of file lwlock.c.

Referenced by GetLWTrancheName(), and LWLockRegisterTranche().

◆ MainLWLockArray

LWLockPadded* MainLWLockArray = NULL

Definition at line 200 of file lwlock.c.

Referenced by PostmasterMarkPIDForWorkerNotify().

◆ NamedLWLockTrancheArray

NamedLWLockTranche* NamedLWLockTrancheArray = NULL

Definition at line 239 of file lwlock.c.

Referenced by PostmasterMarkPIDForWorkerNotify().

◆ NamedLWLockTrancheRequestArray

NamedLWLockTrancheRequest* NamedLWLockTrancheRequestArray = NULL
static

Definition at line 227 of file lwlock.c.

◆ NamedLWLockTrancheRequests

◆ NamedLWLockTrancheRequestsAllocated

int NamedLWLockTrancheRequestsAllocated = 0
static

Definition at line 228 of file lwlock.c.

Referenced by RequestNamedLWLockTranche().

◆ num_held_lwlocks

◆ ShmemLock