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 467 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().

468 {
470  "MAX_BACKENDS too big for lwlock.c");
471 
473  sizeof(LWLock) <= LWLOCK_PADDED_SIZE,
474  "Miscalculated LWLock padding");
475 
476  if (!IsUnderPostmaster)
477  {
478  Size spaceLocks = LWLockShmemSize();
479  int *LWLockCounter;
480  char *ptr;
481 
482  /* Allocate space */
483  ptr = (char *) ShmemAlloc(spaceLocks);
484 
485  /* Leave room for dynamic allocation of tranches */
486  ptr += sizeof(int);
487 
488  /* Ensure desired alignment of LWLock array */
489  ptr += LWLOCK_PADDED_SIZE - ((uintptr_t) ptr) % LWLOCK_PADDED_SIZE;
490 
491  MainLWLockArray = (LWLockPadded *) ptr;
492 
493  /*
494  * Initialize the dynamic-allocation counter for tranches, which is
495  * stored just before the first LWLock.
496  */
497  LWLockCounter = (int *) ((char *) MainLWLockArray - sizeof(int));
498  *LWLockCounter = LWTRANCHE_FIRST_USER_DEFINED;
499 
500  /* Initialize all LWLocks */
502  }
503 
504  /* Register named extension LWLock tranches in the current process. */
505  for (int i = 0; i < NamedLWLockTrancheRequests; i++)
507  NamedLWLockTrancheArray[i].trancheName);
508 }
Definition: lwlock.h:31
void * ShmemAlloc(Size size)
Definition: shmem.c:161
NamedLWLockTranche * NamedLWLockTrancheArray
Definition: lwlock.c:239
Size LWLockShmemSize(void)
Definition: lwlock.c:434
void LWLockRegisterTranche(int tranche_id, const char *tranche_name)
Definition: lwlock.c:651
#define StaticAssertStmt(condition, errmessage)
Definition: c.h:918
#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:110
unsigned int uint32
Definition: c.h:441
static void InitializeLWLocks(void)
Definition: lwlock.c:514
size_t Size
Definition: c.h:540
#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 807 of file lwlock.c.

References Assert, GetLWTrancheName(), and PG_WAIT_LWLOCK.

Referenced by pgstat_get_wait_event().

808 {
809  Assert(classId == PG_WAIT_LWLOCK);
810  /* The event IDs are just tranche numbers. */
811  return GetLWTrancheName(eventId);
812 }
static const char * GetLWTrancheName(uint16 trancheId)
Definition: lwlock.c:779
#define Assert(condition)
Definition: c.h:804
#define PG_WAIT_LWLOCK
Definition: pgstat.h:895

◆ GetLWTrancheName()

static const char * GetLWTrancheName ( uint16  trancheId)
static

Definition at line 779 of file lwlock.c.

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

Referenced by GetLWLockIdentifier().

780 {
781  /* Individual LWLock? */
782  if (trancheId < NUM_INDIVIDUAL_LWLOCKS)
783  return IndividualLWLockNames[trancheId];
784 
785  /* Built-in tranche? */
786  if (trancheId < LWTRANCHE_FIRST_USER_DEFINED)
787  return BuiltinTrancheNames[trancheId - NUM_INDIVIDUAL_LWLOCKS];
788 
789  /*
790  * It's an extension tranche, so look in LWLockTrancheNames[]. However,
791  * it's possible that the tranche has never been registered in the current
792  * process, in which case give up and return "extension".
793  */
794  trancheId -= LWTRANCHE_FIRST_USER_DEFINED;
795 
796  if (trancheId >= LWLockTrancheNamesAllocated ||
797  LWLockTrancheNames[trancheId] == NULL)
798  return "extension";
799 
800  return LWLockTrancheNames[trancheId];
801 }
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 597 of file lwlock.c.

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

Referenced by pgss_shmem_startup().

598 {
599  int lock_pos;
600  int i;
601 
602  /*
603  * Obtain the position of base address of LWLock belonging to requested
604  * tranche_name in MainLWLockArray. LWLocks for named tranches are placed
605  * in MainLWLockArray after fixed locks.
606  */
607  lock_pos = NUM_FIXED_LWLOCKS;
608  for (i = 0; i < NamedLWLockTrancheRequests; i++)
609  {
610  if (strcmp(NamedLWLockTrancheRequestArray[i].tranche_name,
611  tranche_name) == 0)
612  return &MainLWLockArray[lock_pos];
613 
615  }
616 
617  elog(ERROR, "requested tranche is not registered");
618 
619  /* just to keep compiler quiet */
620  return NULL;
621 }
#define NUM_FIXED_LWLOCKS
Definition: lwlock.h:127
#define ERROR
Definition: elog.h:45
int NamedLWLockTrancheRequests
Definition: lwlock.c:236
static NamedLWLockTrancheRequest * NamedLWLockTrancheRequestArray
Definition: lwlock.c:227
#define elog(elevel,...)
Definition: elog.h:228
int i
LWLockPadded * MainLWLockArray
Definition: lwlock.c:200

◆ InitializeLWLocks()

static void InitializeLWLocks ( void  )
static

Definition at line 514 of file lwlock.c.

References BUFFER_MAPPING_LWLOCK_OFFSET, i, LWLockPadded::lock, LWLockHandle::lock, LOCK_MANAGER_LWLOCK_OFFSET, 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(), PREDICATELOCK_MANAGER_LWLOCK_OFFSET, NamedLWLockTrancheRequest::tranche_name, NamedLWLockTranche::trancheId, and NamedLWLockTranche::trancheName.

Referenced by CreateLWLocks().

515 {
516  int numNamedLocks = NumLWLocksForNamedTranches();
517  int id;
518  int i;
519  int j;
520  LWLockPadded *lock;
521 
522  /* Initialize all individual LWLocks in main array */
523  for (id = 0, lock = MainLWLockArray; id < NUM_INDIVIDUAL_LWLOCKS; id++, lock++)
524  LWLockInitialize(&lock->lock, id);
525 
526  /* Initialize buffer mapping LWLocks in main array */
528  for (id = 0; id < NUM_BUFFER_PARTITIONS; id++, lock++)
530 
531  /* Initialize lmgrs' LWLocks in main array */
533  for (id = 0; id < NUM_LOCK_PARTITIONS; id++, lock++)
535 
536  /* Initialize predicate lmgrs' LWLocks in main array */
538  for (id = 0; id < NUM_PREDICATELOCK_PARTITIONS; id++, lock++)
540 
541  /*
542  * Copy the info about any named tranches into shared memory (so that
543  * other processes can see it), and initialize the requested LWLocks.
544  */
546  {
547  char *trancheNames;
548 
550  &MainLWLockArray[NUM_FIXED_LWLOCKS + numNamedLocks];
551 
552  trancheNames = (char *) NamedLWLockTrancheArray +
555 
556  for (i = 0; i < NamedLWLockTrancheRequests; i++)
557  {
558  NamedLWLockTrancheRequest *request;
559  NamedLWLockTranche *tranche;
560  char *name;
561 
562  request = &NamedLWLockTrancheRequestArray[i];
563  tranche = &NamedLWLockTrancheArray[i];
564 
565  name = trancheNames;
566  trancheNames += strlen(request->tranche_name) + 1;
567  strcpy(name, request->tranche_name);
568  tranche->trancheId = LWLockNewTrancheId();
569  tranche->trancheName = name;
570 
571  for (j = 0; j < request->num_lwlocks; j++, lock++)
572  LWLockInitialize(&lock->lock, tranche->trancheId);
573  }
574  }
575 }
#define BUFFER_MAPPING_LWLOCK_OFFSET
Definition: lwlock.h:122
int LWLockNewTrancheId(void)
Definition: lwlock.c:627
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:419
#define NUM_BUFFER_PARTITIONS
Definition: lwlock.h:111
char * trancheName
Definition: lwlock.h:95
void LWLockInitialize(LWLock *lock, int tranche_id)
Definition: lwlock.c:743
#define PREDICATELOCK_MANAGER_LWLOCK_OFFSET
Definition: lwlock.h:125
LWLock lock
Definition: lwlock.h:78
const char * name
Definition: encode.c:515
static NamedLWLockTrancheRequest * NamedLWLockTrancheRequestArray
Definition: lwlock.c:227
#define LOCK_MANAGER_LWLOCK_OFFSET
Definition: lwlock.h:123
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 581 of file lwlock.c.

Referenced by InitProcess().

582 {
583 #ifdef LWLOCK_STATS
584  init_lwlock_stats();
585 #endif
586 }

◆ LWLockAcquire()

bool LWLockAcquire ( LWLock lock,
LWLockMode  mode 
)

Definition at line 1206 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(), 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(), FindAndDropRelFileNodeBuffers(), FinishPreparedTransaction(), FlushDatabaseBuffers(), FlushRelationBuffers(), FlushRelationsAllBuffers(), ForceTransactionIdLimitUpdate(), ForwardSyncRequest(), FreeWorkerInfo(), get_xid_status(), 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(), pgstat_reset_replslot_counter(), 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(), ReadMultiXactIdRange(), 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_guts(), replorigin_get_progress(), replorigin_session_advance(), replorigin_session_get_progress(), replorigin_session_reset(), replorigin_session_setup(), resize(), RestoreScratchTarget(), restoreTwoPhaseData(), SaveSlotToPath(), SerialAdd(), SerialGetMinConflictCommitSeqNo(), SerialSetActiveSerXmin(), set_indexsafe_procflags(), SetCommitTsLimit(), SetMultiXactIdLimit(), SetOffsetVacuumLimit(), SetTransactionIdLimit(), SetXidCommitTsInPage(), SharedInvalBackendInit(), ShmemInitStruct(), SICleanupQueue(), SIGetDataEntries(), SignalBackends(), SignalVirtualTransaction(), 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(), update_cached_xid_range(), 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().

1207 {
1208  PGPROC *proc = MyProc;
1209  bool result = true;
1210  int extraWaits = 0;
1211 #ifdef LWLOCK_STATS
1212  lwlock_stats *lwstats;
1213 
1214  lwstats = get_lwlock_stats_entry(lock);
1215 #endif
1216 
1218 
1219  PRINT_LWDEBUG("LWLockAcquire", lock, mode);
1220 
1221 #ifdef LWLOCK_STATS
1222  /* Count lock acquisition attempts */
1223  if (mode == LW_EXCLUSIVE)
1224  lwstats->ex_acquire_count++;
1225  else
1226  lwstats->sh_acquire_count++;
1227 #endif /* LWLOCK_STATS */
1228 
1229  /*
1230  * We can't wait if we haven't got a PGPROC. This should only occur
1231  * during bootstrap or shared memory initialization. Put an Assert here
1232  * to catch unsafe coding practices.
1233  */
1234  Assert(!(proc == NULL && IsUnderPostmaster));
1235 
1236  /* Ensure we will have room to remember the lock */
1238  elog(ERROR, "too many LWLocks taken");
1239 
1240  /*
1241  * Lock out cancel/die interrupts until we exit the code section protected
1242  * by the LWLock. This ensures that interrupts will not interfere with
1243  * manipulations of data structures in shared memory.
1244  */
1245  HOLD_INTERRUPTS();
1246 
1247  /*
1248  * Loop here to try to acquire lock after each time we are signaled by
1249  * LWLockRelease.
1250  *
1251  * NOTE: it might seem better to have LWLockRelease actually grant us the
1252  * lock, rather than retrying and possibly having to go back to sleep. But
1253  * in practice that is no good because it means a process swap for every
1254  * lock acquisition when two or more processes are contending for the same
1255  * lock. Since LWLocks are normally used to protect not-very-long
1256  * sections of computation, a process needs to be able to acquire and
1257  * release the same lock many times during a single CPU time slice, even
1258  * in the presence of contention. The efficiency of being able to do that
1259  * outweighs the inefficiency of sometimes wasting a process dispatch
1260  * cycle because the lock is not free when a released waiter finally gets
1261  * to run. See pgsql-hackers archives for 29-Dec-01.
1262  */
1263  for (;;)
1264  {
1265  bool mustwait;
1266 
1267  /*
1268  * Try to grab the lock the first time, we're not in the waitqueue
1269  * yet/anymore.
1270  */
1271  mustwait = LWLockAttemptLock(lock, mode);
1272 
1273  if (!mustwait)
1274  {
1275  LOG_LWDEBUG("LWLockAcquire", lock, "immediately acquired lock");
1276  break; /* got the lock */
1277  }
1278 
1279  /*
1280  * Ok, at this point we couldn't grab the lock on the first try. We
1281  * cannot simply queue ourselves to the end of the list and wait to be
1282  * woken up because by now the lock could long have been released.
1283  * Instead add us to the queue and try to grab the lock again. If we
1284  * succeed we need to revert the queuing and be happy, otherwise we
1285  * recheck the lock. If we still couldn't grab it, we know that the
1286  * other locker will see our queue entries when releasing since they
1287  * existed before we checked for the lock.
1288  */
1289 
1290  /* add to the queue */
1291  LWLockQueueSelf(lock, mode);
1292 
1293  /* we're now guaranteed to be woken up if necessary */
1294  mustwait = LWLockAttemptLock(lock, mode);
1295 
1296  /* ok, grabbed the lock the second time round, need to undo queueing */
1297  if (!mustwait)
1298  {
1299  LOG_LWDEBUG("LWLockAcquire", lock, "acquired, undoing queue");
1300 
1301  LWLockDequeueSelf(lock);
1302  break;
1303  }
1304 
1305  /*
1306  * Wait until awakened.
1307  *
1308  * Since we share the process wait semaphore with the regular lock
1309  * manager and ProcWaitForSignal, and we may need to acquire an LWLock
1310  * while one of those is pending, it is possible that we get awakened
1311  * for a reason other than being signaled by LWLockRelease. If so,
1312  * loop back and wait again. Once we've gotten the LWLock,
1313  * re-increment the sema by the number of additional signals received,
1314  * so that the lock manager or signal manager will see the received
1315  * signal when it next waits.
1316  */
1317  LOG_LWDEBUG("LWLockAcquire", lock, "waiting");
1318 
1319 #ifdef LWLOCK_STATS
1320  lwstats->block_count++;
1321 #endif
1322 
1323  LWLockReportWaitStart(lock);
1324  TRACE_POSTGRESQL_LWLOCK_WAIT_START(T_NAME(lock), mode);
1325 
1326  for (;;)
1327  {
1328  PGSemaphoreLock(proc->sem);
1329  if (!proc->lwWaiting)
1330  break;
1331  extraWaits++;
1332  }
1333 
1334  /* Retrying, allow LWLockRelease to release waiters again. */
1336 
1337 #ifdef LOCK_DEBUG
1338  {
1339  /* not waiting anymore */
1340  uint32 nwaiters PG_USED_FOR_ASSERTS_ONLY = pg_atomic_fetch_sub_u32(&lock->nwaiters, 1);
1341 
1342  Assert(nwaiters < MAX_BACKENDS);
1343  }
1344 #endif
1345 
1346  TRACE_POSTGRESQL_LWLOCK_WAIT_DONE(T_NAME(lock), mode);
1348 
1349  LOG_LWDEBUG("LWLockAcquire", lock, "awakened");
1350 
1351  /* Now loop back and try to acquire lock again. */
1352  result = false;
1353  }
1354 
1355  TRACE_POSTGRESQL_LWLOCK_ACQUIRE(T_NAME(lock), mode);
1356 
1357  /* Add lock to list of locks held by this backend */
1360 
1361  /*
1362  * Fix the process wait semaphore's count for any absorbed wakeups.
1363  */
1364  while (extraWaits-- > 0)
1365  PGSemaphoreUnlock(proc->sem);
1366 
1367  return result;
1368 }
#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:824
void PGSemaphoreUnlock(PGSemaphore sema)
Definition: posix_sema.c:340
PGPROC * MyProc
Definition: proc.c:68
bool lwWaiting
Definition: proc.h:170
#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:45
#define MAX_BACKENDS
Definition: postmaster.h:75
LWLockMode mode
Definition: lwlock.c:214
bool IsUnderPostmaster
Definition: globals.c:110
static void LWLockReportWaitEnd(void)
Definition: lwlock.c:770
unsigned int uint32
Definition: c.h:441
static void LWLockDequeueSelf(LWLock *lock)
Definition: lwlock.c:1111
#define AssertArg(condition)
Definition: c.h:806
static void LWLockReportWaitStart(LWLock *lock)
Definition: lwlock.c:761
static void LWLockQueueSelf(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:1067
static int num_held_lwlocks
Definition: lwlock.c:217
#define Assert(condition)
Definition: c.h:804
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:117
#define elog(elevel,...)
Definition: elog.h:228
static uint32 pg_atomic_fetch_or_u32(volatile pg_atomic_uint32 *ptr, uint32 or_)
Definition: atomics.h:372
PGSemaphore sem
Definition: proc.h:127
Definition: proc.h:121
#define PG_USED_FOR_ASSERTS_ONLY
Definition: c.h:155
#define LOG_LWDEBUG(a, b, c)
Definition: lwlock.c:313

◆ LWLockAcquireOrWait()

bool LWLockAcquireOrWait ( LWLock lock,
LWLockMode  mode 
)

Definition at line 1433 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().

1434 {
1435  PGPROC *proc = MyProc;
1436  bool mustwait;
1437  int extraWaits = 0;
1438 #ifdef LWLOCK_STATS
1439  lwlock_stats *lwstats;
1440 
1441  lwstats = get_lwlock_stats_entry(lock);
1442 #endif
1443 
1445 
1446  PRINT_LWDEBUG("LWLockAcquireOrWait", lock, mode);
1447 
1448  /* Ensure we will have room to remember the lock */
1450  elog(ERROR, "too many LWLocks taken");
1451 
1452  /*
1453  * Lock out cancel/die interrupts until we exit the code section protected
1454  * by the LWLock. This ensures that interrupts will not interfere with
1455  * manipulations of data structures in shared memory.
1456  */
1457  HOLD_INTERRUPTS();
1458 
1459  /*
1460  * NB: We're using nearly the same twice-in-a-row lock acquisition
1461  * protocol as LWLockAcquire(). Check its comments for details.
1462  */
1463  mustwait = LWLockAttemptLock(lock, mode);
1464 
1465  if (mustwait)
1466  {
1468 
1469  mustwait = LWLockAttemptLock(lock, mode);
1470 
1471  if (mustwait)
1472  {
1473  /*
1474  * Wait until awakened. Like in LWLockAcquire, be prepared for
1475  * bogus wakeups, because we share the semaphore with
1476  * ProcWaitForSignal.
1477  */
1478  LOG_LWDEBUG("LWLockAcquireOrWait", lock, "waiting");
1479 
1480 #ifdef LWLOCK_STATS
1481  lwstats->block_count++;
1482 #endif
1483 
1484  LWLockReportWaitStart(lock);
1485  TRACE_POSTGRESQL_LWLOCK_WAIT_START(T_NAME(lock), mode);
1486 
1487  for (;;)
1488  {
1489  PGSemaphoreLock(proc->sem);
1490  if (!proc->lwWaiting)
1491  break;
1492  extraWaits++;
1493  }
1494 
1495 #ifdef LOCK_DEBUG
1496  {
1497  /* not waiting anymore */
1498  uint32 nwaiters PG_USED_FOR_ASSERTS_ONLY = pg_atomic_fetch_sub_u32(&lock->nwaiters, 1);
1499 
1500  Assert(nwaiters < MAX_BACKENDS);
1501  }
1502 #endif
1503  TRACE_POSTGRESQL_LWLOCK_WAIT_DONE(T_NAME(lock), mode);
1505 
1506  LOG_LWDEBUG("LWLockAcquireOrWait", lock, "awakened");
1507  }
1508  else
1509  {
1510  LOG_LWDEBUG("LWLockAcquireOrWait", lock, "acquired, undoing queue");
1511 
1512  /*
1513  * Got lock in the second attempt, undo queueing. We need to treat
1514  * this as having successfully acquired the lock, otherwise we'd
1515  * not necessarily wake up people we've prevented from acquiring
1516  * the lock.
1517  */
1518  LWLockDequeueSelf(lock);
1519  }
1520  }
1521 
1522  /*
1523  * Fix the process wait semaphore's count for any absorbed wakeups.
1524  */
1525  while (extraWaits-- > 0)
1526  PGSemaphoreUnlock(proc->sem);
1527 
1528  if (mustwait)
1529  {
1530  /* Failed to get lock, so release interrupt holdoff */
1532  LOG_LWDEBUG("LWLockAcquireOrWait", lock, "failed");
1533  TRACE_POSTGRESQL_LWLOCK_ACQUIRE_OR_WAIT_FAIL(T_NAME(lock), mode);
1534  }
1535  else
1536  {
1537  LOG_LWDEBUG("LWLockAcquireOrWait", lock, "succeeded");
1538  /* Add lock to list of locks held by this backend */
1541  TRACE_POSTGRESQL_LWLOCK_ACQUIRE_OR_WAIT(T_NAME(lock), mode);
1542  }
1543 
1544  return !mustwait;
1545 }
#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:824
void PGSemaphoreUnlock(PGSemaphore sema)
Definition: posix_sema.c:340
PGPROC * MyProc
Definition: proc.c:68
bool lwWaiting
Definition: proc.h:170
#define MAX_SIMUL_LWLOCKS
Definition: lwlock.c:208
#define RESUME_INTERRUPTS()
Definition: miscadmin.h:119
static LWLockHandle held_lwlocks[MAX_SIMUL_LWLOCKS]
Definition: lwlock.c:218
#define ERROR
Definition: elog.h:45
#define MAX_BACKENDS
Definition: postmaster.h:75
LWLockMode mode
Definition: lwlock.c:214
static void LWLockReportWaitEnd(void)
Definition: lwlock.c:770
unsigned int uint32
Definition: c.h:441
static void LWLockDequeueSelf(LWLock *lock)
Definition: lwlock.c:1111
static void LWLockReportWaitStart(LWLock *lock)
Definition: lwlock.c:761
static void LWLockQueueSelf(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:1067
static int num_held_lwlocks
Definition: lwlock.c:217
#define Assert(condition)
Definition: c.h:804
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:117
#define elog(elevel,...)
Definition: elog.h:228
PGSemaphore sem
Definition: proc.h:127
Definition: proc.h:121
#define PG_USED_FOR_ASSERTS_ONLY
Definition: c.h:155
#define LOG_LWDEBUG(a, b, c)
Definition: lwlock.c:313

◆ LWLockAttemptLock()

static bool LWLockAttemptLock ( LWLock lock,
LWLockMode  mode 
)
static

Definition at line 824 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().

825 {
826  uint32 old_state;
827 
829 
830  /*
831  * Read once outside the loop, later iterations will get the newer value
832  * via compare & exchange.
833  */
834  old_state = pg_atomic_read_u32(&lock->state);
835 
836  /* loop until we've determined whether we could acquire the lock or not */
837  while (true)
838  {
839  uint32 desired_state;
840  bool lock_free;
841 
842  desired_state = old_state;
843 
844  if (mode == LW_EXCLUSIVE)
845  {
846  lock_free = (old_state & LW_LOCK_MASK) == 0;
847  if (lock_free)
848  desired_state += LW_VAL_EXCLUSIVE;
849  }
850  else
851  {
852  lock_free = (old_state & LW_VAL_EXCLUSIVE) == 0;
853  if (lock_free)
854  desired_state += LW_VAL_SHARED;
855  }
856 
857  /*
858  * Attempt to swap in the state we are expecting. If we didn't see
859  * lock to be free, that's just the old value. If we saw it as free,
860  * we'll attempt to mark it acquired. The reason that we always swap
861  * in the value is that this doubles as a memory barrier. We could try
862  * to be smarter and only swap in values if we saw the lock as free,
863  * but benchmark haven't shown it as beneficial so far.
864  *
865  * Retry if the value changed since we last looked at it.
866  */
868  &old_state, desired_state))
869  {
870  if (lock_free)
871  {
872  /* Great! Got the lock. */
873 #ifdef LOCK_DEBUG
874  if (mode == LW_EXCLUSIVE)
875  lock->owner = MyProc;
876 #endif
877  return false;
878  }
879  else
880  return true; /* somebody else has the lock */
881  }
882  }
883  pg_unreachable();
884 }
static PgChecksumMode mode
Definition: pg_checksums.c:61
#define pg_unreachable()
Definition: c.h:258
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:68
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:441
#define AssertArg(condition)
Definition: c.h:806
#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 1378 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().

1379 {
1380  bool mustwait;
1381 
1383 
1384  PRINT_LWDEBUG("LWLockConditionalAcquire", lock, mode);
1385 
1386  /* Ensure we will have room to remember the lock */
1388  elog(ERROR, "too many LWLocks taken");
1389 
1390  /*
1391  * Lock out cancel/die interrupts until we exit the code section protected
1392  * by the LWLock. This ensures that interrupts will not interfere with
1393  * manipulations of data structures in shared memory.
1394  */
1395  HOLD_INTERRUPTS();
1396 
1397  /* Check for the lock */
1398  mustwait = LWLockAttemptLock(lock, mode);
1399 
1400  if (mustwait)
1401  {
1402  /* Failed to get lock, so release interrupt holdoff */
1404 
1405  LOG_LWDEBUG("LWLockConditionalAcquire", lock, "failed");
1406  TRACE_POSTGRESQL_LWLOCK_CONDACQUIRE_FAIL(T_NAME(lock), mode);
1407  }
1408  else
1409  {
1410  /* Add lock to list of locks held by this backend */
1413  TRACE_POSTGRESQL_LWLOCK_CONDACQUIRE(T_NAME(lock), mode);
1414  }
1415  return !mustwait;
1416 }
#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:824
#define MAX_SIMUL_LWLOCKS
Definition: lwlock.c:208
#define RESUME_INTERRUPTS()
Definition: miscadmin.h:119
static LWLockHandle held_lwlocks[MAX_SIMUL_LWLOCKS]
Definition: lwlock.c:218
#define ERROR
Definition: elog.h:45
LWLockMode mode
Definition: lwlock.c:214
#define AssertArg(condition)
Definition: c.h:806
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:117
#define elog(elevel,...)
Definition: elog.h:228
#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 1557 of file lwlock.c.

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

Referenced by LWLockWaitForVar().

1560 {
1561  bool mustwait;
1562  uint64 value;
1563 
1564  /*
1565  * Test first to see if it the slot is free right now.
1566  *
1567  * XXX: the caller uses a spinlock before this, so we don't need a memory
1568  * barrier here as far as the current usage is concerned. But that might
1569  * not be safe in general.
1570  */
1571  mustwait = (pg_atomic_read_u32(&lock->state) & LW_VAL_EXCLUSIVE) != 0;
1572 
1573  if (!mustwait)
1574  {
1575  *result = true;
1576  return false;
1577  }
1578 
1579  *result = false;
1580 
1581  /*
1582  * Read value using the lwlock's wait list lock, as we can't generally
1583  * rely on atomic 64 bit reads/stores. TODO: On platforms with a way to
1584  * do atomic 64 bit reads/writes the spinlock should be optimized away.
1585  */
1586  LWLockWaitListLock(lock);
1587  value = *valptr;
1588  LWLockWaitListUnlock(lock);
1589 
1590  if (value != oldval)
1591  {
1592  mustwait = false;
1593  *newval = value;
1594  }
1595  else
1596  {
1597  mustwait = true;
1598  }
1599 
1600  return mustwait;
1601 }
static void LWLockWaitListUnlock(LWLock *lock)
Definition: lwlock.c:947
pg_atomic_uint32 state
Definition: lwlock.h:34
static struct @141 value
#define newval
static void LWLockWaitListLock(LWLock *lock)
Definition: lwlock.c:895
#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 1111 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().

1112 {
1113  bool found = false;
1114  proclist_mutable_iter iter;
1115 
1116 #ifdef LWLOCK_STATS
1117  lwlock_stats *lwstats;
1118 
1119  lwstats = get_lwlock_stats_entry(lock);
1120 
1121  lwstats->dequeue_self_count++;
1122 #endif
1123 
1124  LWLockWaitListLock(lock);
1125 
1126  /*
1127  * Can't just remove ourselves from the list, but we need to iterate over
1128  * all entries as somebody else could have dequeued us.
1129  */
1130  proclist_foreach_modify(iter, &lock->waiters, lwWaitLink)
1131  {
1132  if (iter.cur == MyProc->pgprocno)
1133  {
1134  found = true;
1135  proclist_delete(&lock->waiters, iter.cur, lwWaitLink);
1136  break;
1137  }
1138  }
1139 
1140  if (proclist_is_empty(&lock->waiters) &&
1141  (pg_atomic_read_u32(&lock->state) & LW_FLAG_HAS_WAITERS) != 0)
1142  {
1144  }
1145 
1146  /* XXX: combine with fetch_and above? */
1147  LWLockWaitListUnlock(lock);
1148 
1149  /* clear waiting state again, nice for debugging */
1150  if (found)
1151  MyProc->lwWaiting = false;
1152  else
1153  {
1154  int extraWaits = 0;
1155 
1156  /*
1157  * Somebody else dequeued us and has or will wake us up. Deal with the
1158  * superfluous absorption of a wakeup.
1159  */
1160 
1161  /*
1162  * Reset RELEASE_OK flag if somebody woke us before we removed
1163  * ourselves - they'll have set it to false.
1164  */
1166 
1167  /*
1168  * Now wait for the scheduled wakeup, otherwise our ->lwWaiting would
1169  * get reset at some inconvenient point later. Most of the time this
1170  * will immediately return.
1171  */
1172  for (;;)
1173  {
1175  if (!MyProc->lwWaiting)
1176  break;
1177  extraWaits++;
1178  }
1179 
1180  /*
1181  * Fix the process wait semaphore's count for any absorbed wakeups.
1182  */
1183  while (extraWaits-- > 0)
1185  }
1186 
1187 #ifdef LOCK_DEBUG
1188  {
1189  /* not waiting anymore */
1190  uint32 nwaiters PG_USED_FOR_ASSERTS_ONLY = pg_atomic_fetch_sub_u32(&lock->nwaiters, 1);
1191 
1192  Assert(nwaiters < MAX_BACKENDS);
1193  }
1194 #endif
1195 }
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:68
proclist_head waiters
Definition: lwlock.h:35
bool lwWaiting
Definition: proc.h:170
static void LWLockWaitListUnlock(LWLock *lock)
Definition: lwlock.c:947
#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:441
#define Assert(condition)
Definition: c.h:804
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:895
int pgprocno
Definition: proc.h:150
static uint32 pg_atomic_fetch_or_u32(volatile pg_atomic_uint32 *ptr, uint32 or_)
Definition: atomics.h:372
PGSemaphore sem
Definition: proc.h:127
#define PG_USED_FOR_ASSERTS_ONLY
Definition: c.h:155
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 1942 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(), ProcArrayEndTransactionInternal(), ProcessTwoPhaseBuffer(), RemoveGXact(), SearchNamedReplicationSlot(), SyncRepWakeQueue(), TransactionIdSetPageStatusInternal(), and TransferPredicateLocksToNewTarget().

1943 {
1944  int i;
1945 
1946  for (i = 0; i < num_held_lwlocks; i++)
1947  {
1948  if (held_lwlocks[i].lock == l && held_lwlocks[i].mode == mode)
1949  return true;
1950  }
1951  return false;
1952 }
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 743 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().

744 {
746 #ifdef LOCK_DEBUG
747  pg_atomic_init_u32(&lock->nwaiters, 0);
748 #endif
749  lock->tranche = tranche_id;
750  proclist_init(&lock->waiters);
751 }
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 627 of file lwlock.c.

References ShmemLock, SpinLockAcquire, and SpinLockRelease.

Referenced by apw_init_shmem(), and InitializeLWLocks().

628 {
629  int result;
630  int *LWLockCounter;
631 
632  LWLockCounter = (int *) ((char *) MainLWLockArray - sizeof(int));
634  result = (*LWLockCounter)++;
636 
637  return result;
638 }
#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 1067 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().

1068 {
1069  /*
1070  * If we don't have a PGPROC structure, there's no way to wait. This
1071  * should never occur, since MyProc should only be null during shared
1072  * memory initialization.
1073  */
1074  if (MyProc == NULL)
1075  elog(PANIC, "cannot wait without a PGPROC structure");
1076 
1077  if (MyProc->lwWaiting)
1078  elog(PANIC, "queueing for lock while waiting on another one");
1079 
1080  LWLockWaitListLock(lock);
1081 
1082  /* setting the flag is protected by the spinlock */
1084 
1085  MyProc->lwWaiting = true;
1086  MyProc->lwWaitMode = mode;
1087 
1088  /* LW_WAIT_UNTIL_FREE waiters are always at the front of the queue */
1089  if (mode == LW_WAIT_UNTIL_FREE)
1090  proclist_push_head(&lock->waiters, MyProc->pgprocno, lwWaitLink);
1091  else
1092  proclist_push_tail(&lock->waiters, MyProc->pgprocno, lwWaitLink);
1093 
1094  /* Can release the mutex now */
1095  LWLockWaitListUnlock(lock);
1096 
1097 #ifdef LOCK_DEBUG
1098  pg_atomic_fetch_add_u32(&lock->nwaiters, 1);
1099 #endif
1100 
1101 }
static PgChecksumMode mode
Definition: pg_checksums.c:61
#define LW_FLAG_HAS_WAITERS
Definition: lwlock.c:99
PGPROC * MyProc
Definition: proc.c:68
proclist_head waiters
Definition: lwlock.h:35
bool lwWaiting
Definition: proc.h:170
static void LWLockWaitListUnlock(LWLock *lock)
Definition: lwlock.c:947
uint8 lwWaitMode
Definition: proc.h:171
pg_atomic_uint32 state
Definition: lwlock.h:34
#define PANIC
Definition: elog.h:55
#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:895
int pgprocno
Definition: proc.h:150
#define elog(elevel,...)
Definition: elog.h:228
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 651 of file lwlock.c.

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

Referenced by apw_init_shmem(), and CreateLWLocks().

652 {
653  /* This should only be called for user-defined tranches. */
654  if (tranche_id < LWTRANCHE_FIRST_USER_DEFINED)
655  return;
656 
657  /* Convert to array index. */
658  tranche_id -= LWTRANCHE_FIRST_USER_DEFINED;
659 
660  /* If necessary, create or enlarge array. */
661  if (tranche_id >= LWLockTrancheNamesAllocated)
662  {
663  int newalloc;
664 
665  newalloc = Max(LWLockTrancheNamesAllocated, 8);
666  while (newalloc <= tranche_id)
667  newalloc *= 2;
668 
669  if (LWLockTrancheNames == NULL)
670  LWLockTrancheNames = (const char **)
672  newalloc * sizeof(char *));
673  else
674  {
675  LWLockTrancheNames = (const char **)
676  repalloc(LWLockTrancheNames, newalloc * sizeof(char *));
678  0,
679  (newalloc - LWLockTrancheNamesAllocated) * sizeof(char *));
680  }
681  LWLockTrancheNamesAllocated = newalloc;
682  }
683 
684  LWLockTrancheNames[tranche_id] = tranche_name;
685 }
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:980
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 1808 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(), 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(), FindAndDropRelFileNodeBuffers(), FinishPreparedTransaction(), FlushDatabaseBuffers(), FlushRelationBuffers(), FlushRelationsAllBuffers(), ForceTransactionIdLimitUpdate(), ForwardSyncRequest(), FreeWorkerInfo(), get_xid_status(), 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(), pgstat_reset_replslot_counter(), 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(), ReadMultiXactIdRange(), 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_guts(), replorigin_get_progress(), replorigin_session_advance(), replorigin_session_get_progress(), replorigin_session_reset(), replorigin_session_setup(), resize(), RestoreScratchTarget(), restoreTwoPhaseData(), SaveSlotToPath(), SerialAdd(), SerialGetMinConflictCommitSeqNo(), SerialSetActiveSerXmin(), set_indexsafe_procflags(), SetCommitTsLimit(), SetMultiXactIdLimit(), SetOffsetVacuumLimit(), SetTransactionIdLimit(), SetXidCommitTsInPage(), SharedInvalBackendInit(), ShmemInitStruct(), SICleanupQueue(), SIGetDataEntries(), SignalBackends(), SignalVirtualTransaction(), 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(), update_cached_xid_range(), 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().

1809 {
1810  LWLockMode mode;
1811  uint32 oldstate;
1812  bool check_waiters;
1813  int i;
1814 
1815  /*
1816  * Remove lock from list of locks held. Usually, but not always, it will
1817  * be the latest-acquired lock; so search array backwards.
1818  */
1819  for (i = num_held_lwlocks; --i >= 0;)
1820  if (lock == held_lwlocks[i].lock)
1821  break;
1822 
1823  if (i < 0)
1824  elog(ERROR, "lock %s is not held", T_NAME(lock));
1825 
1826  mode = held_lwlocks[i].mode;
1827 
1828  num_held_lwlocks--;
1829  for (; i < num_held_lwlocks; i++)
1830  held_lwlocks[i] = held_lwlocks[i + 1];
1831 
1832  PRINT_LWDEBUG("LWLockRelease", lock, mode);
1833 
1834  /*
1835  * Release my hold on lock, after that it can immediately be acquired by
1836  * others, even if we still have to wakeup other waiters.
1837  */
1838  if (mode == LW_EXCLUSIVE)
1839  oldstate = pg_atomic_sub_fetch_u32(&lock->state, LW_VAL_EXCLUSIVE);
1840  else
1841  oldstate = pg_atomic_sub_fetch_u32(&lock->state, LW_VAL_SHARED);
1842 
1843  /* nobody else can have that kind of lock */
1844  Assert(!(oldstate & LW_VAL_EXCLUSIVE));
1845 
1846 
1847  /*
1848  * We're still waiting for backends to get scheduled, don't wake them up
1849  * again.
1850  */
1851  if ((oldstate & (LW_FLAG_HAS_WAITERS | LW_FLAG_RELEASE_OK)) ==
1853  (oldstate & LW_LOCK_MASK) == 0)
1854  check_waiters = true;
1855  else
1856  check_waiters = false;
1857 
1858  /*
1859  * As waking up waiters requires the spinlock to be acquired, only do so
1860  * if necessary.
1861  */
1862  if (check_waiters)
1863  {
1864  /* XXX: remove before commit? */
1865  LOG_LWDEBUG("LWLockRelease", lock, "releasing waiters");
1866  LWLockWakeup(lock);
1867  }
1868 
1869  TRACE_POSTGRESQL_LWLOCK_RELEASE(T_NAME(lock));
1870 
1871  /*
1872  * Now okay to allow cancel/die interrupts.
1873  */
1875 }
#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:119
static LWLockHandle held_lwlocks[MAX_SIMUL_LWLOCKS]
Definition: lwlock.c:218
#define ERROR
Definition: elog.h:45
LWLockMode mode
Definition: lwlock.c:214
static void LWLockWakeup(LWLock *lock)
Definition: lwlock.c:960
unsigned int uint32
Definition: c.h:441
static int num_held_lwlocks
Definition: lwlock.c:217
#define Assert(condition)
Definition: c.h:804
#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:228
int i
#define LOG_LWDEBUG(a, b, c)
Definition: lwlock.c:313

◆ LWLockReleaseAll()

void LWLockReleaseAll ( void  )

Definition at line 1907 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().

1908 {
1909  while (num_held_lwlocks > 0)
1910  {
1911  HOLD_INTERRUPTS(); /* match the upcoming RESUME_INTERRUPTS */
1912 
1914  }
1915 }
void LWLockRelease(LWLock *lock)
Definition: lwlock.c:1808
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:117

◆ LWLockReleaseClearVar()

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

Definition at line 1881 of file lwlock.c.

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

Referenced by WALInsertLockRelease().

1882 {
1883  LWLockWaitListLock(lock);
1884 
1885  /*
1886  * Set the variable's value before releasing the lock, that prevents race
1887  * a race condition wherein a new locker acquires the lock, but hasn't yet
1888  * set the variables value.
1889  */
1890  *valptr = val;
1891  LWLockWaitListUnlock(lock);
1892 
1893  LWLockRelease(lock);
1894 }
static void LWLockWaitListUnlock(LWLock *lock)
Definition: lwlock.c:947
void LWLockRelease(LWLock *lock)
Definition: lwlock.c:1808
static void LWLockWaitListLock(LWLock *lock)
Definition: lwlock.c:895
long val
Definition: informix.c:664

◆ LWLockReportWaitEnd()

static void LWLockReportWaitEnd ( void  )
inlinestatic

Definition at line 770 of file lwlock.c.

References pgstat_report_wait_end().

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

771 {
773 }
static void pgstat_report_wait_end(void)
Definition: pgstat.h:1512

◆ LWLockReportWaitStart()

static void LWLockReportWaitStart ( LWLock lock)
inlinestatic

Definition at line 761 of file lwlock.c.

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

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

762 {
764 }
uint16 tranche
Definition: lwlock.h:33
static void pgstat_report_wait_start(uint32 wait_event_info)
Definition: pgstat.h:1488
#define PG_WAIT_LWLOCK
Definition: pgstat.h:895

◆ LWLockShmemSize()

Size LWLockShmemSize ( void  )

Definition at line 434 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().

435 {
436  Size size;
437  int i;
438  int numLocks = NUM_FIXED_LWLOCKS;
439 
440  /* Calculate total number of locks needed in the main array. */
441  numLocks += NumLWLocksForNamedTranches();
442 
443  /* Space for the LWLock array. */
444  size = mul_size(numLocks, sizeof(LWLockPadded));
445 
446  /* Space for dynamic allocation counter, plus room for alignment. */
447  size = add_size(size, sizeof(int) + LWLOCK_PADDED_SIZE);
448 
449  /* space for named tranches. */
451 
452  /* space for name of each tranche. */
453  for (i = 0; i < NamedLWLockTrancheRequests; i++)
454  size = add_size(size, strlen(NamedLWLockTrancheRequestArray[i].tranche_name) + 1);
455 
456  /* Disallow adding any more named tranches. */
458 
459  return size;
460 }
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:419
Size mul_size(Size s1, Size s2)
Definition: shmem.c:519
Size add_size(Size s1, Size s2)
Definition: shmem.c:502
size_t Size
Definition: c.h:540
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 1754 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().

1755 {
1756  proclist_head wakeup;
1757  proclist_mutable_iter iter;
1758 
1759  PRINT_LWDEBUG("LWLockUpdateVar", lock, LW_EXCLUSIVE);
1760 
1761  proclist_init(&wakeup);
1762 
1763  LWLockWaitListLock(lock);
1764 
1766 
1767  /* Update the lock's value */
1768  *valptr = val;
1769 
1770  /*
1771  * See if there are any LW_WAIT_UNTIL_FREE waiters that need to be woken
1772  * up. They are always in the front of the queue.
1773  */
1774  proclist_foreach_modify(iter, &lock->waiters, lwWaitLink)
1775  {
1776  PGPROC *waiter = GetPGProcByNumber(iter.cur);
1777 
1778  if (waiter->lwWaitMode != LW_WAIT_UNTIL_FREE)
1779  break;
1780 
1781  proclist_delete(&lock->waiters, iter.cur, lwWaitLink);
1782  proclist_push_tail(&wakeup, iter.cur, lwWaitLink);
1783  }
1784 
1785  /* We are done updating shared state of the lock itself. */
1786  LWLockWaitListUnlock(lock);
1787 
1788  /*
1789  * Awaken any waiters I removed from the queue.
1790  */
1791  proclist_foreach_modify(iter, &wakeup, lwWaitLink)
1792  {
1793  PGPROC *waiter = GetPGProcByNumber(iter.cur);
1794 
1795  proclist_delete(&wakeup, iter.cur, lwWaitLink);
1796  /* check comment in LWLockWakeup() about this barrier */
1797  pg_write_barrier();
1798  waiter->lwWaiting = false;
1799  PGSemaphoreUnlock(waiter->sem);
1800  }
1801 }
#define GetPGProcByNumber(n)
Definition: proc.h:367
void PGSemaphoreUnlock(PGSemaphore sema)
Definition: posix_sema.c:340
proclist_head waiters
Definition: lwlock.h:35
bool lwWaiting
Definition: proc.h:170
static void LWLockWaitListUnlock(LWLock *lock)
Definition: lwlock.c:947
#define proclist_foreach_modify(iter, lhead, link_member)
Definition: proclist.h:206
uint8 lwWaitMode
Definition: proc.h:171
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:804
#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:895
#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:127
Definition: proc.h:121
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 1617 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().

1618 {
1619  PGPROC *proc = MyProc;
1620  int extraWaits = 0;
1621  bool result = false;
1622 #ifdef LWLOCK_STATS
1623  lwlock_stats *lwstats;
1624 
1625  lwstats = get_lwlock_stats_entry(lock);
1626 #endif
1627 
1628  PRINT_LWDEBUG("LWLockWaitForVar", lock, LW_WAIT_UNTIL_FREE);
1629 
1630  /*
1631  * Lock out cancel/die interrupts while we sleep on the lock. There is no
1632  * cleanup mechanism to remove us from the wait queue if we got
1633  * interrupted.
1634  */
1635  HOLD_INTERRUPTS();
1636 
1637  /*
1638  * Loop here to check the lock's status after each time we are signaled.
1639  */
1640  for (;;)
1641  {
1642  bool mustwait;
1643 
1644  mustwait = LWLockConflictsWithVar(lock, valptr, oldval, newval,
1645  &result);
1646 
1647  if (!mustwait)
1648  break; /* the lock was free or value didn't match */
1649 
1650  /*
1651  * Add myself to wait queue. Note that this is racy, somebody else
1652  * could wakeup before we're finished queuing. NB: We're using nearly
1653  * the same twice-in-a-row lock acquisition protocol as
1654  * LWLockAcquire(). Check its comments for details. The only
1655  * difference is that we also have to check the variable's values when
1656  * checking the state of the lock.
1657  */
1659 
1660  /*
1661  * Set RELEASE_OK flag, to make sure we get woken up as soon as the
1662  * lock is released.
1663  */
1665 
1666  /*
1667  * We're now guaranteed to be woken up if necessary. Recheck the lock
1668  * and variables state.
1669  */
1670  mustwait = LWLockConflictsWithVar(lock, valptr, oldval, newval,
1671  &result);
1672 
1673  /* Ok, no conflict after we queued ourselves. Undo queueing. */
1674  if (!mustwait)
1675  {
1676  LOG_LWDEBUG("LWLockWaitForVar", lock, "free, undoing queue");
1677 
1678  LWLockDequeueSelf(lock);
1679  break;
1680  }
1681 
1682  /*
1683  * Wait until awakened.
1684  *
1685  * Since we share the process wait semaphore with the regular lock
1686  * manager and ProcWaitForSignal, and we may need to acquire an LWLock
1687  * while one of those is pending, it is possible that we get awakened
1688  * for a reason other than being signaled by LWLockRelease. If so,
1689  * loop back and wait again. Once we've gotten the LWLock,
1690  * re-increment the sema by the number of additional signals received,
1691  * so that the lock manager or signal manager will see the received
1692  * signal when it next waits.
1693  */
1694  LOG_LWDEBUG("LWLockWaitForVar", lock, "waiting");
1695 
1696 #ifdef LWLOCK_STATS
1697  lwstats->block_count++;
1698 #endif
1699 
1700  LWLockReportWaitStart(lock);
1701  TRACE_POSTGRESQL_LWLOCK_WAIT_START(T_NAME(lock), LW_EXCLUSIVE);
1702 
1703  for (;;)
1704  {
1705  PGSemaphoreLock(proc->sem);
1706  if (!proc->lwWaiting)
1707  break;
1708  extraWaits++;
1709  }
1710 
1711 #ifdef LOCK_DEBUG
1712  {
1713  /* not waiting anymore */
1714  uint32 nwaiters PG_USED_FOR_ASSERTS_ONLY = pg_atomic_fetch_sub_u32(&lock->nwaiters, 1);
1715 
1716  Assert(nwaiters < MAX_BACKENDS);
1717  }
1718 #endif
1719 
1720  TRACE_POSTGRESQL_LWLOCK_WAIT_DONE(T_NAME(lock), LW_EXCLUSIVE);
1722 
1723  LOG_LWDEBUG("LWLockWaitForVar", lock, "awakened");
1724 
1725  /* Now loop back and check the status of the lock again. */
1726  }
1727 
1728  /*
1729  * Fix the process wait semaphore's count for any absorbed wakeups.
1730  */
1731  while (extraWaits-- > 0)
1732  PGSemaphoreUnlock(proc->sem);
1733 
1734  /*
1735  * Now okay to allow cancel/die interrupts.
1736  */
1738 
1739  return result;
1740 }
#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:68
bool lwWaiting
Definition: proc.h:170
pg_atomic_uint32 state
Definition: lwlock.h:34
#define RESUME_INTERRUPTS()
Definition: miscadmin.h:119
#define MAX_BACKENDS
Definition: postmaster.h:75
static void LWLockReportWaitEnd(void)
Definition: lwlock.c:770
unsigned int uint32
Definition: c.h:441
static void LWLockDequeueSelf(LWLock *lock)
Definition: lwlock.c:1111
static void LWLockReportWaitStart(LWLock *lock)
Definition: lwlock.c:761
static void LWLockQueueSelf(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:1067
#define Assert(condition)
Definition: c.h:804
#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:1557
#define HOLD_INTERRUPTS()
Definition: miscadmin.h:117
static uint32 pg_atomic_fetch_or_u32(volatile pg_atomic_uint32 *ptr, uint32 or_)
Definition: atomics.h:372
PGSemaphore sem
Definition: proc.h:127
Definition: proc.h:121
#define PG_USED_FOR_ASSERTS_ONLY
Definition: c.h:155
#define LOG_LWDEBUG(a, b, c)
Definition: lwlock.c:313

◆ LWLockWaitListLock()

static void LWLockWaitListLock ( LWLock lock)
static

Definition at line 895 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().

896 {
897  uint32 old_state;
898 #ifdef LWLOCK_STATS
899  lwlock_stats *lwstats;
900  uint32 delays = 0;
901 
902  lwstats = get_lwlock_stats_entry(lock);
903 #endif
904 
905  while (true)
906  {
907  /* always try once to acquire lock directly */
908  old_state = pg_atomic_fetch_or_u32(&lock->state, LW_FLAG_LOCKED);
909  if (!(old_state & LW_FLAG_LOCKED))
910  break; /* got lock */
911 
912  /* and then spin without atomic operations until lock is released */
913  {
914  SpinDelayStatus delayStatus;
915 
916  init_local_spin_delay(&delayStatus);
917 
918  while (old_state & LW_FLAG_LOCKED)
919  {
920  perform_spin_delay(&delayStatus);
921  old_state = pg_atomic_read_u32(&lock->state);
922  }
923 #ifdef LWLOCK_STATS
924  delays += delayStatus.delays;
925 #endif
926  finish_spin_delay(&delayStatus);
927  }
928 
929  /*
930  * Retry. The lock might obviously already be re-acquired by the time
931  * we're attempting to get it again.
932  */
933  }
934 
935 #ifdef LWLOCK_STATS
936  lwstats->spin_delay_count += delays;
937 #endif
938 }
#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:441
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 947 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().

948 {
950 
951  old_state = pg_atomic_fetch_and_u32(&lock->state, ~LW_FLAG_LOCKED);
952 
953  Assert(old_state & LW_FLAG_LOCKED);
954 }
#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:441
#define Assert(condition)
Definition: c.h:804
#define PG_USED_FOR_ASSERTS_ONLY
Definition: c.h:155

◆ LWLockWakeup()

static void LWLockWakeup ( LWLock lock)
static

Definition at line 960 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().

961 {
962  bool new_release_ok;
963  bool wokeup_somebody = false;
964  proclist_head wakeup;
966 
967  proclist_init(&wakeup);
968 
969  new_release_ok = true;
970 
971  /* lock wait list while collecting backends to wake up */
972  LWLockWaitListLock(lock);
973 
974  proclist_foreach_modify(iter, &lock->waiters, lwWaitLink)
975  {
976  PGPROC *waiter = GetPGProcByNumber(iter.cur);
977 
978  if (wokeup_somebody && waiter->lwWaitMode == LW_EXCLUSIVE)
979  continue;
980 
981  proclist_delete(&lock->waiters, iter.cur, lwWaitLink);
982  proclist_push_tail(&wakeup, iter.cur, lwWaitLink);
983 
984  if (waiter->lwWaitMode != LW_WAIT_UNTIL_FREE)
985  {
986  /*
987  * Prevent additional wakeups until retryer gets to run. Backends
988  * that are just waiting for the lock to become free don't retry
989  * automatically.
990  */
991  new_release_ok = false;
992 
993  /*
994  * Don't wakeup (further) exclusive locks.
995  */
996  wokeup_somebody = true;
997  }
998 
999  /*
1000  * Once we've woken up an exclusive lock, there's no point in waking
1001  * up anybody else.
1002  */
1003  if (waiter->lwWaitMode == LW_EXCLUSIVE)
1004  break;
1005  }
1006 
1008 
1009  /* unset required flags, and release lock, in one fell swoop */
1010  {
1011  uint32 old_state;
1012  uint32 desired_state;
1013 
1014  old_state = pg_atomic_read_u32(&lock->state);
1015  while (true)
1016  {
1017  desired_state = old_state;
1018 
1019  /* compute desired flags */
1020 
1021  if (new_release_ok)
1022  desired_state |= LW_FLAG_RELEASE_OK;
1023  else
1024  desired_state &= ~LW_FLAG_RELEASE_OK;
1025 
1026  if (proclist_is_empty(&wakeup))
1027  desired_state &= ~LW_FLAG_HAS_WAITERS;
1028 
1029  desired_state &= ~LW_FLAG_LOCKED; /* release lock */
1030 
1031  if (pg_atomic_compare_exchange_u32(&lock->state, &old_state,
1032  desired_state))
1033  break;
1034  }
1035  }
1036 
1037  /* Awaken any waiters I removed from the queue. */
1038  proclist_foreach_modify(iter, &wakeup, lwWaitLink)
1039  {
1040  PGPROC *waiter = GetPGProcByNumber(iter.cur);
1041 
1042  LOG_LWDEBUG("LWLockRelease", lock, "release waiter");
1043  proclist_delete(&wakeup, iter.cur, lwWaitLink);
1044 
1045  /*
1046  * Guarantee that lwWaiting being unset only becomes visible once the
1047  * unlink from the link has completed. Otherwise the target backend
1048  * could be woken up for other reason and enqueue for a new lock - if
1049  * that happens before the list unlink happens, the list would end up
1050  * being corrupted.
1051  *
1052  * The barrier pairs with the LWLockWaitListLock() when enqueuing for
1053  * another lock.
1054  */
1055  pg_write_barrier();
1056  waiter->lwWaiting = false;
1057  PGSemaphoreUnlock(waiter->sem);
1058  }
1059 }
#define GetPGProcByNumber(n)
Definition: proc.h:367
#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:170
#define proclist_foreach_modify(iter, lhead, link_member)
Definition: proclist.h:206
uint8 lwWaitMode
Definition: proc.h:171
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:441
#define Assert(condition)
Definition: c.h:804
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:895
static void proclist_init(proclist_head *list)
Definition: proclist.h:29
#define pg_write_barrier()
Definition: atomics.h:159
PGSemaphore sem
Definition: proc.h:127
Definition: proc.h:121
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 419 of file lwlock.c.

References i, and NamedLWLockTrancheRequests.

Referenced by InitializeLWLocks(), and LWLockShmemSize().

420 {
421  int numLocks = 0;
422  int i;
423 
424  for (i = 0; i < NamedLWLockTrancheRequests; i++)
425  numLocks += NamedLWLockTrancheRequestArray[i].num_lwlocks;
426 
427  return numLocks;
428 }
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 703 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().

704 {
705  NamedLWLockTrancheRequest *request;
706 
708  return; /* too late */
709 
710  if (NamedLWLockTrancheRequestArray == NULL)
711  {
716  * sizeof(NamedLWLockTrancheRequest));
717  }
718 
720  {
722 
723  while (i <= NamedLWLockTrancheRequests)
724  i *= 2;
725 
728  i * sizeof(NamedLWLockTrancheRequest));
730  }
731 
733  Assert(strlen(tranche_name) + 1 <= NAMEDATALEN);
734  strlcpy(request->tranche_name, tranche_name, NAMEDATALEN);
735  request->num_lwlocks = num_lwlocks;
737 }
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:110
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:804
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