#include "postgres.h"
#include "miscadmin.h"
#include "pgstat.h"
#include "pg_trace.h"
#include "postmaster/postmaster.h"
#include "replication/slot.h"
#include "storage/ipc.h"
#include "storage/predicate.h"
#include "storage/proc.h"
#include "storage/proclist.h"
#include "storage/spin.h"
#include "utils/memutils.h"

Include dependency graph for lwlock.c:

Data Structures
struct	LWLockHandle

struct	NamedLWLockTrancheRequest

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

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

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

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

#define	LW_VAL_SHARED 1

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

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

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

#define	MAX_SIMUL_LWLOCKS 200

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

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

Typedefs
typedef struct LWLockHandle	LWLockHandle

typedef struct NamedLWLockTrancheRequest	NamedLWLockTrancheRequest

Functions
static void	InitializeLWLocks (void)

static void	RegisterLWLockTranches (void)

static void	LWLockReportWaitStart (LWLock *lock)

static void	LWLockReportWaitEnd (void)

static int	NumLWLocksByNamedTranches (void)

Size	LWLockShmemSize (void)

void	CreateLWLocks (void)

void	InitLWLockAccess (void)

LWLockPadded *	GetNamedLWLockTranche (const char *tranche_name)

int	LWLockNewTrancheId (void)

void	LWLockRegisterTranche (int tranche_id, 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_t *	ShmemLock

static char **	LWLockTrancheArray = NULL

static int	LWLockTranchesAllocated = 0

LWLockPadded *	MainLWLockArray = NULL

static int	num_held_lwlocks = 0

static LWLockHandle	held_lwlocks [MAX_SIMUL_LWLOCKS]

NamedLWLockTrancheRequest *	NamedLWLockTrancheRequestArray = NULL

static int	NamedLWLockTrancheRequestsAllocated = 0

int	NamedLWLockTrancheRequests = 0

NamedLWLockTranche *	NamedLWLockTrancheArray = NULL

static bool	lock_named_request_allowed = true

Macro Definition Documentation

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

Definition at line 228 of file lwlock.c.

Referenced by LWLockAcquire(), LWLockAcquireOrWait(), LWLockConditionalAcquire(), LWLockRelease(), LWLockWaitForVar(), and LWLockWakeup().

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

Definition at line 99 of file lwlock.c.

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

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

Definition at line 101 of file lwlock.c.

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

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

Definition at line 100 of file lwlock.c.

Referenced by LWLockAcquire(), LWLockDequeueSelf(), LWLockInitialize(), LWLockRelease(), LWLockWaitForVar(), and LWLockWakeup().

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

Definition at line 106 of file lwlock.c.

Referenced by LWLockAttemptLock(), and LWLockRelease().

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

Definition at line 108 of file lwlock.c.

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

Definition at line 103 of file lwlock.c.

Referenced by CreateLWLocks(), LWLockAttemptLock(), LWLockConflictsWithVar(), LWLockRelease(), and LWLockUpdateVar().

#define LW_VAL_SHARED 1

Definition at line 104 of file lwlock.c.

Referenced by LWLockAttemptLock(), and LWLockRelease().

#define MAX_SIMUL_LWLOCKS 200

Definition at line 133 of file lwlock.c.

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

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

Definition at line 227 of file lwlock.c.

Referenced by LWLockAcquire(), LWLockAcquireOrWait(), LWLockConditionalAcquire(), LWLockRelease(), LWLockUpdateVar(), and LWLockWaitForVar().

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

Definition at line 117 of file lwlock.c.

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

Typedef Documentation

typedef struct LWLockHandle LWLockHandle

typedef struct NamedLWLockTrancheRequest NamedLWLockTrancheRequest

Function Documentation

void CreateLWLocks ( void )

Definition at line 381 of file lwlock.c.

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

Referenced by CreateSharedMemoryAndSemaphores().

 {
     StaticAssertExpr(LW_VAL_EXCLUSIVE > (uint32) MAX_BACKENDS,
                      "MAX_BACKENDS too big for lwlock.c");
 
     StaticAssertExpr(sizeof(LWLock) <= LWLOCK_MINIMAL_SIZE &&
                      sizeof(LWLock) <= LWLOCK_PADDED_SIZE,
                      "Miscalculated LWLock padding");
 
     if (!IsUnderPostmaster)
     {
         Size        spaceLocks = LWLockShmemSize();
         int        *LWLockCounter;
         char       *ptr;
 
         /* Allocate space */
         ptr = (char *) ShmemAlloc(spaceLocks);
 
         /* Leave room for dynamic allocation of tranches */
         ptr += sizeof(int);
 
         /* Ensure desired alignment of LWLock array */
         ptr += LWLOCK_PADDED_SIZE - ((uintptr_t) ptr) % LWLOCK_PADDED_SIZE;
 
         MainLWLockArray = (LWLockPadded *) ptr;
 
         /*
          * Initialize the dynamic-allocation counter for tranches, which is
          * stored just before the first LWLock.
          */
         LWLockCounter = (int *) ((char *) MainLWLockArray - sizeof(int));
         *LWLockCounter = LWTRANCHE_FIRST_USER_DEFINED;
 
         /* Initialize all LWLocks */
         InitializeLWLocks();
     }
 
     /* Register all LWLock tranches */
     RegisterLWLockTranches();
 }

const char* GetLWLockIdentifier	(	uint32	classId,
		uint16	eventId
	)

Definition at line 703 of file lwlock.c.

References Assert, LWLockTrancheArray, LWLockTranchesAllocated, NULL, and PG_WAIT_LWLOCK.

Referenced by pgstat_get_wait_event().

 {
     Assert(classId == PG_WAIT_LWLOCK);
 
     /*
      * It is quite possible that user has registered tranche in one of the
      * backends (e.g. by allocating lwlocks in dynamic shared memory) but not
      * all of them, so we can't assume the tranche is registered here.
      */
     if (eventId >= LWLockTranchesAllocated ||
         LWLockTrancheArray[eventId] == NULL)
         return "extension";
 
     return LWLockTrancheArray[eventId];
 }

LWLockPadded* GetNamedLWLockTranche ( const char * tranche_name )

Definition at line 541 of file lwlock.c.

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

Referenced by pgss_shmem_startup().

 {
     int         lock_pos;
     int         i;
 
     /*
      * Obtain the position of base address of LWLock belonging to requested
      * tranche_name in MainLWLockArray.  LWLocks for named tranches are placed
      * in MainLWLockArray after fixed locks.
      */
     lock_pos = NUM_FIXED_LWLOCKS;
     for (i = 0; i < NamedLWLockTrancheRequests; i++)
     {
         if (strcmp(NamedLWLockTrancheRequestArray[i].tranche_name,
                    tranche_name) == 0)
             return &MainLWLockArray[lock_pos];
 
         lock_pos += NamedLWLockTrancheRequestArray[i].num_lwlocks;
     }
 
     if (i >= NamedLWLockTrancheRequests)
         elog(ERROR, "requested tranche is not registered");
 
     /* just to keep compiler quiet */
     return NULL;
 }

static void InitializeLWLocks ( void )

static

Definition at line 426 of file lwlock.c.

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

Referenced by CreateLWLocks().

 {
     int         numNamedLocks = NumLWLocksByNamedTranches();
     int         id;
     int         i;
     int         j;
     LWLockPadded *lock;
 
     /* Initialize all individual LWLocks in main array */
     for (id = 0, lock = MainLWLockArray; id < NUM_INDIVIDUAL_LWLOCKS; id++, lock++)
         LWLockInitialize(&lock->lock, id);
 
     /* Initialize buffer mapping LWLocks in main array */
     lock = MainLWLockArray + NUM_INDIVIDUAL_LWLOCKS;
     for (id = 0; id < NUM_BUFFER_PARTITIONS; id++, lock++)
         LWLockInitialize(&lock->lock, LWTRANCHE_BUFFER_MAPPING);
 
     /* Initialize lmgrs' LWLocks in main array */
     lock = MainLWLockArray + NUM_INDIVIDUAL_LWLOCKS + NUM_BUFFER_PARTITIONS;
     for (id = 0; id < NUM_LOCK_PARTITIONS; id++, lock++)
         LWLockInitialize(&lock->lock, LWTRANCHE_LOCK_MANAGER);
 
     /* Initialize predicate lmgrs' LWLocks in main array */
     lock = MainLWLockArray + NUM_INDIVIDUAL_LWLOCKS +
         NUM_BUFFER_PARTITIONS + NUM_LOCK_PARTITIONS;
     for (id = 0; id < NUM_PREDICATELOCK_PARTITIONS; id++, lock++)
         LWLockInitialize(&lock->lock, LWTRANCHE_PREDICATE_LOCK_MANAGER);
 
     /* Initialize named tranches. */
     if (NamedLWLockTrancheRequests > 0)
     {
         char       *trancheNames;
 
         NamedLWLockTrancheArray = (NamedLWLockTranche *)
             &MainLWLockArray[NUM_FIXED_LWLOCKS + numNamedLocks];
 
         trancheNames = (char *) NamedLWLockTrancheArray +
             (NamedLWLockTrancheRequests * sizeof(NamedLWLockTranche));
         lock = &MainLWLockArray[NUM_FIXED_LWLOCKS];
 
         for (i = 0; i < NamedLWLockTrancheRequests; i++)
         {
             NamedLWLockTrancheRequest *request;
             NamedLWLockTranche *tranche;
             char       *name;
 
             request = &NamedLWLockTrancheRequestArray[i];
             tranche = &NamedLWLockTrancheArray[i];
 
             name = trancheNames;
             trancheNames += strlen(request->tranche_name) + 1;
             strcpy(name, request->tranche_name);
             tranche->trancheId = LWLockNewTrancheId();
             tranche->trancheName = name;
 
             for (j = 0; j < request->num_lwlocks; j++, lock++)
                 LWLockInitialize(&lock->lock, tranche->trancheId);
         }
     }
 }

void InitLWLockAccess ( void )

Definition at line 525 of file lwlock.c.

Referenced by InitProcess().

 {
 #ifdef LWLOCK_STATS
     init_lwlock_stats();
 #endif
 }

bool LWLockAcquire	(	LWLock *	lock,
		LWLockMode	mode
	)

Definition at line 1111 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, NULL, num_held_lwlocks, pg_atomic_fetch_or_u32(), pg_atomic_fetch_sub_u32(), PG_USED_FOR_ASSERTS_ONLY, PGSemaphoreLock(), PGSemaphoreUnlock(), PRINT_LWDEBUG, result, PGPROC::sem, LWLock::state, and T_NAME.

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

 {
     PGPROC     *proc = MyProc;
     bool        result = true;
     int         extraWaits = 0;
 #ifdef LWLOCK_STATS
     lwlock_stats *lwstats;
 
     lwstats = get_lwlock_stats_entry(lock);
 #endif
 
     AssertArg(mode == LW_SHARED || mode == LW_EXCLUSIVE);
 
     PRINT_LWDEBUG("LWLockAcquire", lock, mode);
 
 #ifdef LWLOCK_STATS
     /* Count lock acquisition attempts */
     if (mode == LW_EXCLUSIVE)
         lwstats->ex_acquire_count++;
     else
         lwstats->sh_acquire_count++;
 #endif                          /* LWLOCK_STATS */
 
     /*
      * We can't wait if we haven't got a PGPROC.  This should only occur
      * during bootstrap or shared memory initialization.  Put an Assert here
      * to catch unsafe coding practices.
      */
     Assert(!(proc == NULL && IsUnderPostmaster));
 
     /* Ensure we will have room to remember the lock */
     if (num_held_lwlocks >= MAX_SIMUL_LWLOCKS)
         elog(ERROR, "too many LWLocks taken");
 
     /*
      * Lock out cancel/die interrupts until we exit the code section protected
      * by the LWLock.  This ensures that interrupts will not interfere with
      * manipulations of data structures in shared memory.
      */
     HOLD_INTERRUPTS();
 
     /*
      * Loop here to try to acquire lock after each time we are signaled by
      * LWLockRelease.
      *
      * NOTE: it might seem better to have LWLockRelease actually grant us the
      * lock, rather than retrying and possibly having to go back to sleep. But
      * in practice that is no good because it means a process swap for every
      * lock acquisition when two or more processes are contending for the same
      * lock.  Since LWLocks are normally used to protect not-very-long
      * sections of computation, a process needs to be able to acquire and
      * release the same lock many times during a single CPU time slice, even
      * in the presence of contention.  The efficiency of being able to do that
      * outweighs the inefficiency of sometimes wasting a process dispatch
      * cycle because the lock is not free when a released waiter finally gets
      * to run.  See pgsql-hackers archives for 29-Dec-01.
      */
     for (;;)
     {
         bool        mustwait;
 
         /*
          * Try to grab the lock the first time, we're not in the waitqueue
          * yet/anymore.
          */
         mustwait = LWLockAttemptLock(lock, mode);
 
         if (!mustwait)
         {
             LOG_LWDEBUG("LWLockAcquire", lock, "immediately acquired lock");
             break;              /* got the lock */
         }
 
         /*
          * Ok, at this point we couldn't grab the lock on the first try. We
          * cannot simply queue ourselves to the end of the list and wait to be
          * woken up because by now the lock could long have been released.
          * Instead add us to the queue and try to grab the lock again. If we
          * succeed we need to revert the queuing and be happy, otherwise we
          * recheck the lock. If we still couldn't grab it, we know that the
          * other locker will see our queue entries when releasing since they
          * existed before we checked for the lock.
          */
 
         /* add to the queue */
         LWLockQueueSelf(lock, mode);
 
         /* we're now guaranteed to be woken up if necessary */
         mustwait = LWLockAttemptLock(lock, mode);
 
         /* ok, grabbed the lock the second time round, need to undo queueing */
         if (!mustwait)
         {
             LOG_LWDEBUG("LWLockAcquire", lock, "acquired, undoing queue");
 
             LWLockDequeueSelf(lock);
             break;
         }
 
         /*
          * Wait until awakened.
          *
          * Since we share the process wait semaphore with the regular lock
          * manager and ProcWaitForSignal, and we may need to acquire an LWLock
          * while one of those is pending, it is possible that we get awakened
          * for a reason other than being signaled by LWLockRelease. If so,
          * loop back and wait again.  Once we've gotten the LWLock,
          * re-increment the sema by the number of additional signals received,
          * so that the lock manager or signal manager will see the received
          * signal when it next waits.
          */
         LOG_LWDEBUG("LWLockAcquire", lock, "waiting");
 
 #ifdef LWLOCK_STATS
         lwstats->block_count++;
 #endif
 
         LWLockReportWaitStart(lock);
         TRACE_POSTGRESQL_LWLOCK_WAIT_START(T_NAME(lock), mode);
 
         for (;;)
         {
             PGSemaphoreLock(proc->sem);
             if (!proc->lwWaiting)
                 break;
             extraWaits++;
         }
 
         /* Retrying, allow LWLockRelease to release waiters again. */
         pg_atomic_fetch_or_u32(&lock->state, LW_FLAG_RELEASE_OK);
 
 #ifdef LOCK_DEBUG
         {
             /* not waiting anymore */
             uint32      nwaiters PG_USED_FOR_ASSERTS_ONLY = pg_atomic_fetch_sub_u32(&lock->nwaiters, 1);
 
             Assert(nwaiters < MAX_BACKENDS);
         }
 #endif
 
         TRACE_POSTGRESQL_LWLOCK_WAIT_DONE(T_NAME(lock), mode);
         LWLockReportWaitEnd();
 
         LOG_LWDEBUG("LWLockAcquire", lock, "awakened");
 
         /* Now loop back and try to acquire lock again. */
         result = false;
     }
 
     TRACE_POSTGRESQL_LWLOCK_ACQUIRE(T_NAME(lock), mode);
 
     /* Add lock to list of locks held by this backend */
     held_lwlocks[num_held_lwlocks].lock = lock;
     held_lwlocks[num_held_lwlocks++].mode = mode;
 
     /*
      * Fix the process wait semaphore's count for any absorbed wakeups.
      */
     while (extraWaits-- > 0)
         PGSemaphoreUnlock(proc->sem);
 
     return result;
 }

bool LWLockAcquireOrWait	(	LWLock *	lock,
		LWLockMode	mode
	)

Definition at line 1338 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().

 {
     PGPROC     *proc = MyProc;
     bool        mustwait;
     int         extraWaits = 0;
 #ifdef LWLOCK_STATS
     lwlock_stats *lwstats;
 
     lwstats = get_lwlock_stats_entry(lock);
 #endif
 
     Assert(mode == LW_SHARED || mode == LW_EXCLUSIVE);
 
     PRINT_LWDEBUG("LWLockAcquireOrWait", lock, mode);
 
     /* Ensure we will have room to remember the lock */
     if (num_held_lwlocks >= MAX_SIMUL_LWLOCKS)
         elog(ERROR, "too many LWLocks taken");
 
     /*
      * Lock out cancel/die interrupts until we exit the code section protected
      * by the LWLock.  This ensures that interrupts will not interfere with
      * manipulations of data structures in shared memory.
      */
     HOLD_INTERRUPTS();
 
     /*
      * NB: We're using nearly the same twice-in-a-row lock acquisition
      * protocol as LWLockAcquire(). Check its comments for details.
      */
     mustwait = LWLockAttemptLock(lock, mode);
 
     if (mustwait)
     {
         LWLockQueueSelf(lock, LW_WAIT_UNTIL_FREE);
 
         mustwait = LWLockAttemptLock(lock, mode);
 
         if (mustwait)
         {
             /*
              * Wait until awakened.  Like in LWLockAcquire, be prepared for
              * bogus wakeups, because we share the semaphore with
              * ProcWaitForSignal.
              */
             LOG_LWDEBUG("LWLockAcquireOrWait", lock, "waiting");
 
 #ifdef LWLOCK_STATS
             lwstats->block_count++;
 #endif
 
             LWLockReportWaitStart(lock);
             TRACE_POSTGRESQL_LWLOCK_WAIT_START(T_NAME(lock), mode);
 
             for (;;)
             {
                 PGSemaphoreLock(proc->sem);
                 if (!proc->lwWaiting)
                     break;
                 extraWaits++;
             }
 
 #ifdef LOCK_DEBUG
             {
                 /* not waiting anymore */
                 uint32      nwaiters PG_USED_FOR_ASSERTS_ONLY = pg_atomic_fetch_sub_u32(&lock->nwaiters, 1);
 
                 Assert(nwaiters < MAX_BACKENDS);
             }
 #endif
             TRACE_POSTGRESQL_LWLOCK_WAIT_DONE(T_NAME(lock), mode);
             LWLockReportWaitEnd();
 
             LOG_LWDEBUG("LWLockAcquireOrWait", lock, "awakened");
         }
         else
         {
             LOG_LWDEBUG("LWLockAcquireOrWait", lock, "acquired, undoing queue");
 
             /*
              * Got lock in the second attempt, undo queueing. We need to treat
              * this as having successfully acquired the lock, otherwise we'd
              * not necessarily wake up people we've prevented from acquiring
              * the lock.
              */
             LWLockDequeueSelf(lock);
         }
     }
 
     /*
      * Fix the process wait semaphore's count for any absorbed wakeups.
      */
     while (extraWaits-- > 0)
         PGSemaphoreUnlock(proc->sem);
 
     if (mustwait)
     {
         /* Failed to get lock, so release interrupt holdoff */
         RESUME_INTERRUPTS();
         LOG_LWDEBUG("LWLockAcquireOrWait", lock, "failed");
         TRACE_POSTGRESQL_LWLOCK_ACQUIRE_OR_WAIT_FAIL(T_NAME(lock), mode);
     }
     else
     {
         LOG_LWDEBUG("LWLockAcquireOrWait", lock, "succeeded");
         /* Add lock to list of locks held by this backend */
         held_lwlocks[num_held_lwlocks].lock = lock;
         held_lwlocks[num_held_lwlocks++].mode = mode;
         TRACE_POSTGRESQL_LWLOCK_ACQUIRE_OR_WAIT(T_NAME(lock), mode);
     }
 
     return !mustwait;
 }

static bool LWLockAttemptLock	(	LWLock *	lock,
		LWLockMode	mode
	)

static

Definition at line 729 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().

 {
     uint32      old_state;
 
     AssertArg(mode == LW_EXCLUSIVE || mode == LW_SHARED);
 
     /*
      * Read once outside the loop, later iterations will get the newer value
      * via compare & exchange.
      */
     old_state = pg_atomic_read_u32(&lock->state);
 
     /* loop until we've determined whether we could acquire the lock or not */
     while (true)
     {
         uint32      desired_state;
         bool        lock_free;
 
         desired_state = old_state;
 
         if (mode == LW_EXCLUSIVE)
         {
             lock_free = (old_state & LW_LOCK_MASK) == 0;
             if (lock_free)
                 desired_state += LW_VAL_EXCLUSIVE;
         }
         else
         {
             lock_free = (old_state & LW_VAL_EXCLUSIVE) == 0;
             if (lock_free)
                 desired_state += LW_VAL_SHARED;
         }
 
         /*
          * Attempt to swap in the state we are expecting. If we didn't see
          * lock to be free, that's just the old value. If we saw it as free,
          * we'll attempt to mark it acquired. The reason that we always swap
          * in the value is that this doubles as a memory barrier. We could try
          * to be smarter and only swap in values if we saw the lock as free,
          * but benchmark haven't shown it as beneficial so far.
          *
          * Retry if the value changed since we last looked at it.
          */
         if (pg_atomic_compare_exchange_u32(&lock->state,
                                            &old_state, desired_state))
         {
             if (lock_free)
             {
                 /* Great! Got the lock. */
 #ifdef LOCK_DEBUG
                 if (mode == LW_EXCLUSIVE)
                     lock->owner = MyProc;
 #endif
                 return false;
             }
             else
                 return true;    /* somebody else has the lock */
         }
     }
     pg_unreachable();
 }

bool LWLockConditionalAcquire	(	LWLock *	lock,
		LWLockMode	mode
	)

Definition at line 1283 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(), and XLogNeedsFlush().

 {
     bool        mustwait;
 
     AssertArg(mode == LW_SHARED || mode == LW_EXCLUSIVE);
 
     PRINT_LWDEBUG("LWLockConditionalAcquire", lock, mode);
 
     /* Ensure we will have room to remember the lock */
     if (num_held_lwlocks >= MAX_SIMUL_LWLOCKS)
         elog(ERROR, "too many LWLocks taken");
 
     /*
      * Lock out cancel/die interrupts until we exit the code section protected
      * by the LWLock.  This ensures that interrupts will not interfere with
      * manipulations of data structures in shared memory.
      */
     HOLD_INTERRUPTS();
 
     /* Check for the lock */
     mustwait = LWLockAttemptLock(lock, mode);
 
     if (mustwait)
     {
         /* Failed to get lock, so release interrupt holdoff */
         RESUME_INTERRUPTS();
 
         LOG_LWDEBUG("LWLockConditionalAcquire", lock, "failed");
         TRACE_POSTGRESQL_LWLOCK_CONDACQUIRE_FAIL(T_NAME(lock), mode);
     }
     else
     {
         /* Add lock to list of locks held by this backend */
         held_lwlocks[num_held_lwlocks].lock = lock;
         held_lwlocks[num_held_lwlocks++].mode = mode;
         TRACE_POSTGRESQL_LWLOCK_CONDACQUIRE(T_NAME(lock), mode);
     }
     return !mustwait;
 }

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

static

Definition at line 1462 of file lwlock.c.

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

Referenced by LWLockWaitForVar().

 {
     bool        mustwait;
     uint64      value;
 
     /*
      * Test first to see if it the slot is free right now.
      *
      * XXX: the caller uses a spinlock before this, so we don't need a memory
      * barrier here as far as the current usage is concerned.  But that might
      * not be safe in general.
      */
     mustwait = (pg_atomic_read_u32(&lock->state) & LW_VAL_EXCLUSIVE) != 0;
 
     if (!mustwait)
     {
         *result = true;
         return false;
     }
 
     *result = false;
 
     /*
      * Read value using the lwlock's wait list lock, as we can't generally
      * rely on atomic 64 bit reads/stores.  TODO: On platforms with a way to
      * do atomic 64 bit reads/writes the spinlock should be optimized away.
      */
     LWLockWaitListLock(lock);
     value = *valptr;
     LWLockWaitListUnlock(lock);
 
     if (value != oldval)
     {
         mustwait = false;
         *newval = value;
     }
     else
     {
         mustwait = true;
     }
 
     return mustwait;
 }

static void LWLockDequeueSelf ( LWLock * lock )

static

Definition at line 1016 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().

 {
     bool        found = false;
     proclist_mutable_iter iter;
 
 #ifdef LWLOCK_STATS
     lwlock_stats *lwstats;
 
     lwstats = get_lwlock_stats_entry(lock);
 
     lwstats->dequeue_self_count++;
 #endif
 
     LWLockWaitListLock(lock);
 
     /*
      * Can't just remove ourselves from the list, but we need to iterate over
      * all entries as somebody else could have dequeued us.
      */
     proclist_foreach_modify(iter, &lock->waiters, lwWaitLink)
     {
         if (iter.cur == MyProc->pgprocno)
         {
             found = true;
             proclist_delete(&lock->waiters, iter.cur, lwWaitLink);
             break;
         }
     }
 
     if (proclist_is_empty(&lock->waiters) &&
         (pg_atomic_read_u32(&lock->state) & LW_FLAG_HAS_WAITERS) != 0)
     {
         pg_atomic_fetch_and_u32(&lock->state, ~LW_FLAG_HAS_WAITERS);
     }
 
     /* XXX: combine with fetch_and above? */
     LWLockWaitListUnlock(lock);
 
     /* clear waiting state again, nice for debugging */
     if (found)
         MyProc->lwWaiting = false;
     else
     {
         int         extraWaits = 0;
 
         /*
          * Somebody else dequeued us and has or will wake us up. Deal with the
          * superfluous absorption of a wakeup.
          */
 
         /*
          * Reset releaseOk if somebody woke us before we removed ourselves -
          * they'll have set it to false.
          */
         pg_atomic_fetch_or_u32(&lock->state, LW_FLAG_RELEASE_OK);
 
         /*
          * Now wait for the scheduled wakeup, otherwise our ->lwWaiting would
          * get reset at some inconvenient point later. Most of the time this
          * will immediately return.
          */
         for (;;)
         {
             PGSemaphoreLock(MyProc->sem);
             if (!MyProc->lwWaiting)
                 break;
             extraWaits++;
         }
 
         /*
          * Fix the process wait semaphore's count for any absorbed wakeups.
          */
         while (extraWaits-- > 0)
             PGSemaphoreUnlock(MyProc->sem);
     }
 
 #ifdef LOCK_DEBUG
     {
         /* not waiting anymore */
         uint32      nwaiters PG_USED_FOR_ASSERTS_ONLY = pg_atomic_fetch_sub_u32(&lock->nwaiters, 1);
 
         Assert(nwaiters < MAX_BACKENDS);
     }
 #endif
 }

bool LWLockHeldByMe ( LWLock * l )

Definition at line 1831 of file lwlock.c.

References i, and num_held_lwlocks.

Referenced by alloc_object(), CompactCheckpointerRequestQueue(), DeleteLockTarget(), ensure_active_superblock(), FlushOneBuffer(), get_best_segment(), GetOldestSafeDecodingTransactionId(), init_span(), logicalrep_sync_worker_count(), logicalrep_worker_find(), make_new_segment(), MarkBufferDirtyHint(), OnConflict_CheckForSerializationFailure(), ProcArraySetReplicationSlotXmin(), ReleaseOneSerializableXact(), RemoveScratchTarget(), RemoveTargetIfNoLongerUsed(), RestoreScratchTarget(), SetNewSxactGlobalXmin(), TransactionIdInRecentPast(), TransferPredicateLocksToNewTarget(), and UnpinBuffer().

 {
     int         i;
 
     for (i = 0; i < num_held_lwlocks; i++)
     {
         if (held_lwlocks[i].lock == l)
             return true;
     }
     return false;
 }

bool LWLockHeldByMeInMode	(	LWLock *	l,
		LWLockMode	mode
	)

Definition at line 1849 of file lwlock.c.

References i, and num_held_lwlocks.

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

 {
     int         i;
 
     for (i = 0; i < num_held_lwlocks; i++)
     {
         if (held_lwlocks[i].lock == l && held_lwlocks[i].mode == mode)
             return true;
     }
     return false;
 }

void LWLockInitialize	(	LWLock *	lock,
		int	tranche_id
	)

Definition at line 667 of file lwlock.c.

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

Referenced by create_internal(), InitBufferPool(), InitializeLWLocks(), InitProcGlobal(), ReplicationOriginShmemInit(), ReplicationSlotsShmemInit(), SimpleLruInit(), tbm_prepare_shared_iterate(), and XLOGShmemInit().

 {
     pg_atomic_init_u32(&lock->state, LW_FLAG_RELEASE_OK);
 #ifdef LOCK_DEBUG
     pg_atomic_init_u32(&lock->nwaiters, 0);
 #endif
     lock->tranche = tranche_id;
     proclist_init(&lock->waiters);
 }

int LWLockNewTrancheId ( void )

Definition at line 572 of file lwlock.c.

References result, ShmemLock, SpinLockAcquire, and SpinLockRelease.

Referenced by InitializeLWLocks().

 {
     int         result;
     int        *LWLockCounter;
 
     LWLockCounter = (int *) ((char *) MainLWLockArray - sizeof(int));
     SpinLockAcquire(ShmemLock);
     result = (*LWLockCounter)++;
     SpinLockRelease(ShmemLock);
 
     return result;
 }

static void LWLockQueueSelf	(	LWLock *	lock,
		LWLockMode	mode
	)

static

Definition at line 972 of file lwlock.c.

References elog, LW_FLAG_HAS_WAITERS, LW_WAIT_UNTIL_FREE, LWLockWaitListLock(), LWLockWaitListUnlock(), PGPROC::lwWaiting, PGPROC::lwWaitMode, MyProc, NULL, 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().

 {
     /*
      * If we don't have a PGPROC structure, there's no way to wait. This
      * should never occur, since MyProc should only be null during shared
      * memory initialization.
      */
     if (MyProc == NULL)
         elog(PANIC, "cannot wait without a PGPROC structure");
 
     if (MyProc->lwWaiting)
         elog(PANIC, "queueing for lock while waiting on another one");
 
     LWLockWaitListLock(lock);
 
     /* setting the flag is protected by the spinlock */
     pg_atomic_fetch_or_u32(&lock->state, LW_FLAG_HAS_WAITERS);
 
     MyProc->lwWaiting = true;
     MyProc->lwWaitMode = mode;
 
     /* LW_WAIT_UNTIL_FREE waiters are always at the front of the queue */
     if (mode == LW_WAIT_UNTIL_FREE)
         proclist_push_head(&lock->waiters, MyProc->pgprocno, lwWaitLink);
     else
         proclist_push_tail(&lock->waiters, MyProc->pgprocno, lwWaitLink);
 
     /* Can release the mutex now */
     LWLockWaitListUnlock(lock);
 
 #ifdef LOCK_DEBUG
     pg_atomic_fetch_add_u32(&lock->nwaiters, 1);
 #endif
 
 }

void LWLockRegisterTranche	(	int	tranche_id,
		char *	tranche_name
	)

Definition at line 592 of file lwlock.c.

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

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

 {
     Assert(LWLockTrancheArray != NULL);
 
     if (tranche_id >= LWLockTranchesAllocated)
     {
         int         i = LWLockTranchesAllocated;
         int         j = LWLockTranchesAllocated;
 
         while (i <= tranche_id)
             i *= 2;
 
         LWLockTrancheArray = (char **)
             repalloc(LWLockTrancheArray, i * sizeof(char *));
         LWLockTranchesAllocated = i;
         while (j < LWLockTranchesAllocated)
             LWLockTrancheArray[j++] = NULL;
     }
 
     LWLockTrancheArray[tranche_id] = tranche_name;
 }

void LWLockRelease ( LWLock * lock )

Definition at line 1715 of file lwlock.c.

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

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

 {
     LWLockMode  mode;
     uint32      oldstate;
     bool        check_waiters;
     int         i;
 
     /*
      * Remove lock from list of locks held.  Usually, but not always, it will
      * be the latest-acquired lock; so search array backwards.
      */
     for (i = num_held_lwlocks; --i >= 0;)
         if (lock == held_lwlocks[i].lock)
             break;
 
     if (i < 0)
         elog(ERROR, "lock %s is not held", T_NAME(lock));
 
     mode = held_lwlocks[i].mode;
 
     num_held_lwlocks--;
     for (; i < num_held_lwlocks; i++)
         held_lwlocks[i] = held_lwlocks[i + 1];
 
     PRINT_LWDEBUG("LWLockRelease", lock, mode);
 
     /*
      * Release my hold on lock, after that it can immediately be acquired by
      * others, even if we still have to wakeup other waiters.
      */
     if (mode == LW_EXCLUSIVE)
         oldstate = pg_atomic_sub_fetch_u32(&lock->state, LW_VAL_EXCLUSIVE);
     else
         oldstate = pg_atomic_sub_fetch_u32(&lock->state, LW_VAL_SHARED);
 
     /* nobody else can have that kind of lock */
     Assert(!(oldstate & LW_VAL_EXCLUSIVE));
 
 
     /*
      * We're still waiting for backends to get scheduled, don't wake them up
      * again.
      */
     if ((oldstate & (LW_FLAG_HAS_WAITERS | LW_FLAG_RELEASE_OK)) ==
         (LW_FLAG_HAS_WAITERS | LW_FLAG_RELEASE_OK) &&
         (oldstate & LW_LOCK_MASK) == 0)
         check_waiters = true;
     else
         check_waiters = false;
 
     /*
      * As waking up waiters requires the spinlock to be acquired, only do so
      * if necessary.
      */
     if (check_waiters)
     {
         /* XXX: remove before commit? */
         LOG_LWDEBUG("LWLockRelease", lock, "releasing waiters");
         LWLockWakeup(lock);
     }
 
     TRACE_POSTGRESQL_LWLOCK_RELEASE(T_NAME(lock));
 
     /*
      * Now okay to allow cancel/die interrupts.
      */
     RESUME_INTERRUPTS();
 }

void LWLockReleaseAll ( void )

Definition at line 1814 of file lwlock.c.

References HOLD_INTERRUPTS, LWLockRelease(), and num_held_lwlocks.

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

 {
     while (num_held_lwlocks > 0)
     {
         HOLD_INTERRUPTS();      /* match the upcoming RESUME_INTERRUPTS */
 
         LWLockRelease(held_lwlocks[num_held_lwlocks - 1].lock);
     }
 }

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

Definition at line 1788 of file lwlock.c.

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

Referenced by WALInsertLockRelease().

 {
     LWLockWaitListLock(lock);
 
     /*
      * Set the variable's value before releasing the lock, that prevents race
      * a race condition wherein a new locker acquires the lock, but hasn't yet
      * set the variables value.
      */
     *valptr = val;
     LWLockWaitListUnlock(lock);
 
     LWLockRelease(lock);
 }

static void LWLockReportWaitEnd ( void )

inlinestatic

Definition at line 694 of file lwlock.c.

References pgstat_report_wait_end().

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

 {
     pgstat_report_wait_end();
 }

static void LWLockReportWaitStart ( LWLock * lock )

inlinestatic

Definition at line 685 of file lwlock.c.

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

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

 {
     pgstat_report_wait_start(PG_WAIT_LWLOCK | lock->tranche);
 }

Size LWLockShmemSize ( void )

Definition at line 349 of file lwlock.c.

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

Referenced by CreateLWLocks(), and CreateSharedMemoryAndSemaphores().

 {
     Size        size;
     int         i;
     int         numLocks = NUM_FIXED_LWLOCKS;
 
     numLocks += NumLWLocksByNamedTranches();
 
     /* Space for the LWLock array. */
     size = mul_size(numLocks, sizeof(LWLockPadded));
 
     /* Space for dynamic allocation counter, plus room for alignment. */
     size = add_size(size, sizeof(int) + LWLOCK_PADDED_SIZE);
 
     /* space for named tranches. */
     size = add_size(size, mul_size(NamedLWLockTrancheRequests, sizeof(NamedLWLockTranche)));
 
     /* space for name of each tranche. */
     for (i = 0; i < NamedLWLockTrancheRequests; i++)
         size = add_size(size, strlen(NamedLWLockTrancheRequestArray[i].tranche_name) + 1);
 
     /* Disallow named LWLocks' requests after startup */
     lock_named_request_allowed = false;
 
     return size;
 }

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

Definition at line 1661 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().

 {
     proclist_head wakeup;
     proclist_mutable_iter iter;
 
     PRINT_LWDEBUG("LWLockUpdateVar", lock, LW_EXCLUSIVE);
 
     proclist_init(&wakeup);
 
     LWLockWaitListLock(lock);
 
     Assert(pg_atomic_read_u32(&lock->state) & LW_VAL_EXCLUSIVE);
 
     /* Update the lock's value */
     *valptr = val;
 
     /*
      * See if there are any LW_WAIT_UNTIL_FREE waiters that need to be woken
      * up. They are always in the front of the queue.
      */
     proclist_foreach_modify(iter, &lock->waiters, lwWaitLink)
     {
         PGPROC     *waiter = GetPGProcByNumber(iter.cur);
 
         if (waiter->lwWaitMode != LW_WAIT_UNTIL_FREE)
             break;
 
         proclist_delete(&lock->waiters, iter.cur, lwWaitLink);
         proclist_push_tail(&wakeup, iter.cur, lwWaitLink);
     }
 
     /* We are done updating shared state of the lock itself. */
     LWLockWaitListUnlock(lock);
 
     /*
      * Awaken any waiters I removed from the queue.
      */
     proclist_foreach_modify(iter, &wakeup, lwWaitLink)
     {
         PGPROC     *waiter = GetPGProcByNumber(iter.cur);
 
         proclist_delete(&wakeup, iter.cur, lwWaitLink);
         /* check comment in LWLockWakeup() about this barrier */
         pg_write_barrier();
         waiter->lwWaiting = false;
         PGSemaphoreUnlock(waiter->sem);
     }
 }

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

Definition at line 1522 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, result, RESUME_INTERRUPTS, PGPROC::sem, LWLock::state, and T_NAME.

Referenced by WaitXLogInsertionsToFinish().

 {
     PGPROC     *proc = MyProc;
     int         extraWaits = 0;
     bool        result = false;
 #ifdef LWLOCK_STATS
     lwlock_stats *lwstats;
 
     lwstats = get_lwlock_stats_entry(lock);
 #endif
 
     PRINT_LWDEBUG("LWLockWaitForVar", lock, LW_WAIT_UNTIL_FREE);
 
     /*
      * Lock out cancel/die interrupts while we sleep on the lock.  There is no
      * cleanup mechanism to remove us from the wait queue if we got
      * interrupted.
      */
     HOLD_INTERRUPTS();
 
     /*
      * Loop here to check the lock's status after each time we are signaled.
      */
     for (;;)
     {
         bool        mustwait;
 
         mustwait = LWLockConflictsWithVar(lock, valptr, oldval, newval,
                                           &result);
 
         if (!mustwait)
             break;              /* the lock was free or value didn't match */
 
         /*
          * Add myself to wait queue. Note that this is racy, somebody else
          * could wakeup before we're finished queuing. NB: We're using nearly
          * the same twice-in-a-row lock acquisition protocol as
          * LWLockAcquire(). Check its comments for details. The only
          * difference is that we also have to check the variable's values when
          * checking the state of the lock.
          */
         LWLockQueueSelf(lock, LW_WAIT_UNTIL_FREE);
 
         /*
          * Set RELEASE_OK flag, to make sure we get woken up as soon as the
          * lock is released.
          */
         pg_atomic_fetch_or_u32(&lock->state, LW_FLAG_RELEASE_OK);
 
         /*
          * We're now guaranteed to be woken up if necessary. Recheck the lock
          * and variables state.
          */
         mustwait = LWLockConflictsWithVar(lock, valptr, oldval, newval,
                                           &result);
 
         /* Ok, no conflict after we queued ourselves. Undo queueing. */
         if (!mustwait)
         {
             LOG_LWDEBUG("LWLockWaitForVar", lock, "free, undoing queue");
 
             LWLockDequeueSelf(lock);
             break;
         }
 
         /*
          * Wait until awakened.
          *
          * Since we share the process wait semaphore with the regular lock
          * manager and ProcWaitForSignal, and we may need to acquire an LWLock
          * while one of those is pending, it is possible that we get awakened
          * for a reason other than being signaled by LWLockRelease. If so,
          * loop back and wait again.  Once we've gotten the LWLock,
          * re-increment the sema by the number of additional signals received,
          * so that the lock manager or signal manager will see the received
          * signal when it next waits.
          */
         LOG_LWDEBUG("LWLockWaitForVar", lock, "waiting");
 
 #ifdef LWLOCK_STATS
         lwstats->block_count++;
 #endif
 
         LWLockReportWaitStart(lock);
         TRACE_POSTGRESQL_LWLOCK_WAIT_START(T_NAME(lock), LW_EXCLUSIVE);
 
         for (;;)
         {
             PGSemaphoreLock(proc->sem);
             if (!proc->lwWaiting)
                 break;
             extraWaits++;
         }
 
 #ifdef LOCK_DEBUG
         {
             /* not waiting anymore */
             uint32      nwaiters PG_USED_FOR_ASSERTS_ONLY = pg_atomic_fetch_sub_u32(&lock->nwaiters, 1);
 
             Assert(nwaiters < MAX_BACKENDS);
         }
 #endif
 
         TRACE_POSTGRESQL_LWLOCK_WAIT_DONE(T_NAME(lock), LW_EXCLUSIVE);
         LWLockReportWaitEnd();
 
         LOG_LWDEBUG("LWLockWaitForVar", lock, "awakened");
 
         /* Now loop back and check the status of the lock again. */
     }
 
     TRACE_POSTGRESQL_LWLOCK_ACQUIRE(T_NAME(lock), LW_EXCLUSIVE);
 
     /*
      * Fix the process wait semaphore's count for any absorbed wakeups.
      */
     while (extraWaits-- > 0)
         PGSemaphoreUnlock(proc->sem);
 
     /*
      * Now okay to allow cancel/die interrupts.
      */
     RESUME_INTERRUPTS();
 
     return result;
 }

static void LWLockWaitListLock ( LWLock * lock )

static

Definition at line 800 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().

 {
     uint32      old_state;
 #ifdef LWLOCK_STATS
     lwlock_stats *lwstats;
     uint32      delays = 0;
 
     lwstats = get_lwlock_stats_entry(lock);
 #endif
 
     while (true)
     {
         /* always try once to acquire lock directly */
         old_state = pg_atomic_fetch_or_u32(&lock->state, LW_FLAG_LOCKED);
         if (!(old_state & LW_FLAG_LOCKED))
             break;              /* got lock */
 
         /* and then spin without atomic operations until lock is released */
         {
             SpinDelayStatus delayStatus;
 
             init_local_spin_delay(&delayStatus);
 
             while (old_state & LW_FLAG_LOCKED)
             {
                 perform_spin_delay(&delayStatus);
                 old_state = pg_atomic_read_u32(&lock->state);
             }
 #ifdef LWLOCK_STATS
             delays += delayStatus.delays;
 #endif
             finish_spin_delay(&delayStatus);
         }
 
         /*
          * Retry. The lock might obviously already be re-acquired by the time
          * we're attempting to get it again.
          */
     }
 
 #ifdef LWLOCK_STATS
     lwstats->spin_delay_count += delays;
 #endif
 }

static void LWLockWaitListUnlock ( LWLock * lock )

static

Definition at line 852 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().

 {
     uint32      old_state PG_USED_FOR_ASSERTS_ONLY;
 
     old_state = pg_atomic_fetch_and_u32(&lock->state, ~LW_FLAG_LOCKED);
 
     Assert(old_state & LW_FLAG_LOCKED);
 }

static void LWLockWakeup ( LWLock * lock )

static

Definition at line 865 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().

 {
     bool        new_release_ok;
     bool        wokeup_somebody = false;
     proclist_head wakeup;
     proclist_mutable_iter iter;
 
     proclist_init(&wakeup);
 
     new_release_ok = true;
 
     /* lock wait list while collecting backends to wake up */
     LWLockWaitListLock(lock);
 
     proclist_foreach_modify(iter, &lock->waiters, lwWaitLink)
     {
         PGPROC     *waiter = GetPGProcByNumber(iter.cur);
 
         if (wokeup_somebody && waiter->lwWaitMode == LW_EXCLUSIVE)
             continue;
 
         proclist_delete(&lock->waiters, iter.cur, lwWaitLink);
         proclist_push_tail(&wakeup, iter.cur, lwWaitLink);
 
         if (waiter->lwWaitMode != LW_WAIT_UNTIL_FREE)
         {
             /*
              * Prevent additional wakeups until retryer gets to run. Backends
              * that are just waiting for the lock to become free don't retry
              * automatically.
              */
             new_release_ok = false;
 
             /*
              * Don't wakeup (further) exclusive locks.
              */
             wokeup_somebody = true;
         }
 
         /*
          * Once we've woken up an exclusive lock, there's no point in waking
          * up anybody else.
          */
         if (waiter->lwWaitMode == LW_EXCLUSIVE)
             break;
     }
 
     Assert(proclist_is_empty(&wakeup) || pg_atomic_read_u32(&lock->state) & LW_FLAG_HAS_WAITERS);
 
     /* unset required flags, and release lock, in one fell swoop */
     {
         uint32      old_state;
         uint32      desired_state;
 
         old_state = pg_atomic_read_u32(&lock->state);
         while (true)
         {
             desired_state = old_state;
 
             /* compute desired flags */
 
             if (new_release_ok)
                 desired_state |= LW_FLAG_RELEASE_OK;
             else
                 desired_state &= ~LW_FLAG_RELEASE_OK;
 
             if (proclist_is_empty(&wakeup))
                 desired_state &= ~LW_FLAG_HAS_WAITERS;
 
             desired_state &= ~LW_FLAG_LOCKED;   /* release lock */
 
             if (pg_atomic_compare_exchange_u32(&lock->state, &old_state,
                                                desired_state))
                 break;
         }
     }
 
     /* Awaken any waiters I removed from the queue. */
     proclist_foreach_modify(iter, &wakeup, lwWaitLink)
     {
         PGPROC     *waiter = GetPGProcByNumber(iter.cur);
 
         LOG_LWDEBUG("LWLockRelease", lock, "release waiter");
         proclist_delete(&wakeup, iter.cur, lwWaitLink);
 
         /*
          * Guarantee that lwWaiting being unset only becomes visible once the
          * unlink from the link has completed. Otherwise the target backend
          * could be woken up for other reason and enqueue for a new lock - if
          * that happens before the list unlink happens, the list would end up
          * being corrupted.
          *
          * The barrier pairs with the LWLockWaitListLock() when enqueuing for
          * another lock.
          */
         pg_write_barrier();
         waiter->lwWaiting = false;
         PGSemaphoreUnlock(waiter->sem);
     }
 }

static int NumLWLocksByNamedTranches ( void )

static

Definition at line 334 of file lwlock.c.

References i, and NamedLWLockTrancheRequests.

Referenced by InitializeLWLocks(), and LWLockShmemSize().

 {
     int         numLocks = 0;
     int         i;
 
     for (i = 0; i < NamedLWLockTrancheRequests; i++)
         numLocks += NamedLWLockTrancheRequestArray[i].num_lwlocks;
 
     return numLocks;
 }

static void RegisterLWLockTranches ( void )

static

Definition at line 491 of file lwlock.c.

References Assert, i, LWLockRegisterTranche(), LWLockTrancheArray, LWLockTranchesAllocated, LWTRANCHE_BUFFER_MAPPING, LWTRANCHE_FIRST_USER_DEFINED, LWTRANCHE_LOCK_MANAGER, LWTRANCHE_PARALLEL_QUERY_DSA, LWTRANCHE_PREDICATE_LOCK_MANAGER, LWTRANCHE_TBM, MainLWLockNames, MemoryContextAllocZero(), NamedLWLockTrancheRequests, NULL, and TopMemoryContext.

Referenced by CreateLWLocks().

 {
     int         i;
 
     if (LWLockTrancheArray == NULL)
     {
         LWLockTranchesAllocated = 64;
         LWLockTrancheArray = (char **)
             MemoryContextAllocZero(TopMemoryContext,
                                    LWLockTranchesAllocated * sizeof(char *));
         Assert(LWLockTranchesAllocated >= LWTRANCHE_FIRST_USER_DEFINED);
     }
 
     for (i = 0; i < NUM_INDIVIDUAL_LWLOCKS; ++i)
         LWLockRegisterTranche(i, MainLWLockNames[i]);
 
     LWLockRegisterTranche(LWTRANCHE_BUFFER_MAPPING, "buffer_mapping");
     LWLockRegisterTranche(LWTRANCHE_LOCK_MANAGER, "lock_manager");
     LWLockRegisterTranche(LWTRANCHE_PREDICATE_LOCK_MANAGER,
                           "predicate_lock_manager");
     LWLockRegisterTranche(LWTRANCHE_PARALLEL_QUERY_DSA,
                           "parallel_query_dsa");
     LWLockRegisterTranche(LWTRANCHE_TBM, "tbm");
 
     /* Register named tranches. */
     for (i = 0; i < NamedLWLockTrancheRequests; i++)
         LWLockRegisterTranche(NamedLWLockTrancheArray[i].trancheId,
                               NamedLWLockTrancheArray[i].trancheName);
 }

void RequestNamedLWLockTranche	(	const char *	tranche_name,
		int	num_lwlocks
	)

Definition at line 627 of file lwlock.c.

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

Referenced by _PG_init().

 {
     NamedLWLockTrancheRequest *request;
 
     if (IsUnderPostmaster || !lock_named_request_allowed)
         return;                 /* too late */
 
     if (NamedLWLockTrancheRequestArray == NULL)
     {
         NamedLWLockTrancheRequestsAllocated = 16;
         NamedLWLockTrancheRequestArray = (NamedLWLockTrancheRequest *)
             MemoryContextAlloc(TopMemoryContext,
                                NamedLWLockTrancheRequestsAllocated
                                * sizeof(NamedLWLockTrancheRequest));
     }
 
     if (NamedLWLockTrancheRequests >= NamedLWLockTrancheRequestsAllocated)
     {
         int         i = NamedLWLockTrancheRequestsAllocated;
 
         while (i <= NamedLWLockTrancheRequests)
             i *= 2;
 
         NamedLWLockTrancheRequestArray = (NamedLWLockTrancheRequest *)
             repalloc(NamedLWLockTrancheRequestArray,
                      i * sizeof(NamedLWLockTrancheRequest));
         NamedLWLockTrancheRequestsAllocated = i;
     }
 
     request = &NamedLWLockTrancheRequestArray[NamedLWLockTrancheRequests];
     Assert(strlen(tranche_name) + 1 < NAMEDATALEN);
     StrNCpy(request->tranche_name, tranche_name, NAMEDATALEN);
     request->num_lwlocks = num_lwlocks;
     NamedLWLockTrancheRequests++;
 }