#include "postgres.h"
#include "miscadmin.h"
#include "pg_trace.h"
#include "pgstat.h"
#include "port/pg_bitutils.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	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 (LW_VAL_EXCLUSIVE >(uint32) MAX_BACKENDS, "MAX_BACKENDS too big for lwlock.c")

	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)

LWLockPadded *	GetNamedLWLockTranche (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 *lock)

bool	LWLockAnyHeldByMe (LWLock *lock, int nlocks, size_t stride)

bool	LWLockHeldByMeInMode (LWLock *lock, LWLockMode mode)

Variables
slock_t *	ShmemLock

const char *const	IndividualLWLockNames []

static const char *const	BuiltinTrancheNames []

static const char **	LWLockTrancheNames = NULL

static int	LWLockTrancheNamesAllocated = 0

LWLockPadded *	MainLWLockArray = NULL

static int	num_held_lwlocks = 0

static LWLockHandle	held_lwlocks [MAX_SIMUL_LWLOCKS]

static NamedLWLockTrancheRequest *	NamedLWLockTrancheRequestArray = NULL

static int	NamedLWLockTrancheRequestsAllocated = 0

int	NamedLWLockTrancheRequests = 0

NamedLWLockTranche *	NamedLWLockTrancheArray = NULL

Macro Definition Documentation

◆ LOG_LWDEBUG

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

Definition at line 323 of file lwlock.c.

◆ LW_FLAG_HAS_WAITERS

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

Definition at line 100 of file lwlock.c.

◆ LW_FLAG_LOCKED

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

Definition at line 102 of file lwlock.c.

◆ LW_FLAG_RELEASE_OK

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

Definition at line 101 of file lwlock.c.

◆ LW_LOCK_MASK

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

Definition at line 107 of file lwlock.c.

◆ LW_SHARED_MASK

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

Definition at line 109 of file lwlock.c.

◆ LW_VAL_EXCLUSIVE

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

Definition at line 104 of file lwlock.c.

◆ LW_VAL_SHARED

#define LW_VAL_SHARED 1

Definition at line 105 of file lwlock.c.

◆ MAX_SIMUL_LWLOCKS

#define MAX_SIMUL_LWLOCKS 200

Definition at line 220 of file lwlock.c.

◆ PRINT_LWDEBUG

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

Definition at line 322 of file lwlock.c.

◆ T_NAME

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

Definition at line 258 of file lwlock.c.

Typedef Documentation

◆ LWLockHandle

typedef struct LWLockHandle LWLockHandle

◆ NamedLWLockTrancheRequest

typedef struct NamedLWLockTrancheRequest NamedLWLockTrancheRequest

Function Documentation

◆ CreateLWLocks()

void CreateLWLocks ( void )

Definition at line 474 of file lwlock.c.

 {
     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 named extension LWLock tranches in the current process. */
     for (int i = 0; i < NamedLWLockTrancheRequests; i++)
         LWLockRegisterTranche(NamedLWLockTrancheArray[i].trancheId,
                               NamedLWLockTrancheArray[i].trancheName);
 }

References i, InitializeLWLocks(), IsUnderPostmaster, LWLOCK_PADDED_SIZE, LWLockRegisterTranche(), LWLockShmemSize(), LWTRANCHE_FIRST_USER_DEFINED, MainLWLockArray, NamedLWLockTrancheArray, NamedLWLockTrancheRequests, and ShmemAlloc().

Referenced by CreateSharedMemoryAndSemaphores().

◆ GetLWLockIdentifier()

const char* GetLWLockIdentifier	(	uint32	classId,
		uint16	eventId
	)

Definition at line 794 of file lwlock.c.

 {
     Assert(classId == PG_WAIT_LWLOCK);
     /* The event IDs are just tranche numbers. */
     return GetLWTrancheName(eventId);
 }

References Assert(), GetLWTrancheName(), and PG_WAIT_LWLOCK.

Referenced by pgstat_get_wait_event().

◆ GetLWTrancheName()

static const char * GetLWTrancheName ( uint16 trancheId )

static

Definition at line 766 of file lwlock.c.

 {
     /* Individual LWLock? */
     if (trancheId < NUM_INDIVIDUAL_LWLOCKS)
         return IndividualLWLockNames[trancheId];
  
     /* Built-in tranche? */
     if (trancheId < LWTRANCHE_FIRST_USER_DEFINED)
         return BuiltinTrancheNames[trancheId - NUM_INDIVIDUAL_LWLOCKS];
  
     /*
      * It's an extension tranche, so look in LWLockTrancheNames[].  However,
      * it's possible that the tranche has never been registered in the current
      * process, in which case give up and return "extension".
      */
     trancheId -= LWTRANCHE_FIRST_USER_DEFINED;
  
     if (trancheId >= LWLockTrancheNamesAllocated ||
         LWLockTrancheNames[trancheId] == NULL)
         return "extension";
  
     return LWLockTrancheNames[trancheId];
 }

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

Referenced by GetLWLockIdentifier().

◆ GetNamedLWLockTranche()

LWLockPadded* GetNamedLWLockTranche ( const char * tranche_name )

Definition at line 597 of file lwlock.c.

 {
     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;
     }
  
     elog(ERROR, "requested tranche is not registered");
  
     /* just to keep compiler quiet */
     return NULL;
 }

References elog(), ERROR, i, MainLWLockArray, NamedLWLockTrancheRequestArray, NamedLWLockTrancheRequests, NUM_FIXED_LWLOCKS, and NamedLWLockTrancheRequest::num_lwlocks.

Referenced by pgss_shmem_startup().

◆ InitializeLWLocks()

static void InitializeLWLocks ( void )

static

Definition at line 514 of file lwlock.c.

 {
     int         numNamedLocks = NumLWLocksForNamedTranches();
     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 + BUFFER_MAPPING_LWLOCK_OFFSET;
     for (id = 0; id < NUM_BUFFER_PARTITIONS; id++, lock++)
         LWLockInitialize(&lock->lock, LWTRANCHE_BUFFER_MAPPING);
  
     /* Initialize lmgrs' LWLocks in main array */
     lock = MainLWLockArray + LOCK_MANAGER_LWLOCK_OFFSET;
     for (id = 0; id < NUM_LOCK_PARTITIONS; id++, lock++)
         LWLockInitialize(&lock->lock, LWTRANCHE_LOCK_MANAGER);
  
     /* Initialize predicate lmgrs' LWLocks in main array */
     lock = MainLWLockArray + PREDICATELOCK_MANAGER_LWLOCK_OFFSET;
     for (id = 0; id < NUM_PREDICATELOCK_PARTITIONS; id++, lock++)
         LWLockInitialize(&lock->lock, LWTRANCHE_PREDICATE_LOCK_MANAGER);
  
     /*
      * Copy the info about any named tranches into shared memory (so that
      * other processes can see it), and initialize the requested LWLocks.
      */
     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);
         }
     }
 }

References BUFFER_MAPPING_LWLOCK_OFFSET, i, j, LWLockPadded::lock, LOCK_MANAGER_LWLOCK_OFFSET, LWLockInitialize(), LWLockNewTrancheId(), LWTRANCHE_BUFFER_MAPPING, LWTRANCHE_LOCK_MANAGER, LWTRANCHE_PREDICATE_LOCK_MANAGER, MainLWLockArray, name, NamedLWLockTrancheArray, NamedLWLockTrancheRequestArray, 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().

◆ InitLWLockAccess()

void InitLWLockAccess ( void )

Definition at line 581 of file lwlock.c.

 {
 #ifdef LWLOCK_STATS
     init_lwlock_stats();
 #endif
 }

Referenced by InitProcess().

◆ LWLockAcquire()

bool LWLockAcquire	(	LWLock *	lock,
		LWLockMode	mode
	)

Definition at line 1195 of file lwlock.c.

 {
     PGPROC     *proc = MyProc;
     bool        result = true;
     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("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.
          *
          * 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.
          */
         LOG_LWDEBUG("LWLockAcquire", lock, "waiting");
  
 #ifdef LWLOCK_STATS
         lwstats->block_count++;
 #endif
  
         LWLockReportWaitStart(lock);
         if (TRACE_POSTGRESQL_LWLOCK_WAIT_START_ENABLED())
             TRACE_POSTGRESQL_LWLOCK_WAIT_START(T_NAME(lock), mode);
  
         for (;;)
         {
             PGSemaphoreLock(proc->sem);
             if (proc->lwWaiting == LW_WS_NOT_WAITING)
                 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
  
         if (TRACE_POSTGRESQL_LWLOCK_WAIT_DONE_ENABLED())
             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;
     }
  
     if (TRACE_POSTGRESQL_LWLOCK_ACQUIRE_ENABLED())
         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;
 }

References Assert(), elog(), ERROR, held_lwlocks, HOLD_INTERRUPTS, IsUnderPostmaster, LWLockHandle::lock, LOG_LWDEBUG, LW_EXCLUSIVE, LW_FLAG_RELEASE_OK, LW_SHARED, LW_WS_NOT_WAITING, LWLockAttemptLock(), LWLockDequeueSelf(), LWLockQueueSelf(), LWLockReportWaitEnd(), LWLockReportWaitStart(), PGPROC::lwWaiting, MAX_BACKENDS, MAX_SIMUL_LWLOCKS, LWLockHandle::mode, 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(), 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(), AtEOXact_LogicalRepWorkers(), 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(), 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_backup_start(), do_pg_backup_stop(), 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(), dshash_seq_next(), 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(), FindAndDropRelationBuffers(), FinishPreparedTransaction(), FlushDatabaseBuffers(), FlushRelationBuffers(), FlushRelationsAllBuffers(), ForceTransactionIdLimitUpdate(), ForwardSyncRequest(), FreeWorkerInfo(), GetBackgroundWorkerPid(), GetBackgroundWorkerTypeByPid(), GetBlockerStatusData(), GetConflictingVirtualXIDs(), GetCurrentVirtualXIDs(), GetLastImportantRecPtr(), GetLastSegSwitchData(), GetLatestCommitTsData(), GetLeaderApplyWorkerPid(), 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(), InvalidatePossiblyObsoleteSlot(), IsInstallXLogFileSegmentActive(), KnownAssignedXidsCompress(), KnownAssignedXidsReset(), lock_twophase_recover(), LockAcquireExtended(), LockBuffer(), LockErrorCleanup(), LockGXact(), LockHasWaiters(), LockRefindAndRelease(), LockRelease(), LockReleaseAll(), LockWaiterCount(), logicalrep_launcher_attach_dshmem(), logicalrep_pa_worker_stop(), logicalrep_worker_attach(), logicalrep_worker_detach(), logicalrep_worker_launch(), logicalrep_worker_stop(), logicalrep_worker_stop_internal(), logicalrep_worker_wakeup(), LookupGXact(), 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_archiver_reset_all_cb(), pgstat_archiver_snapshot_cb(), pgstat_bgwriter_reset_all_cb(), pgstat_bgwriter_snapshot_cb(), pgstat_build_snapshot(), pgstat_checkpointer_reset_all_cb(), pgstat_checkpointer_snapshot_cb(), pgstat_flush_io(), pgstat_flush_wal(), pgstat_io_reset_all_cb(), pgstat_io_snapshot_cb(), pgstat_lock_entry(), pgstat_lock_entry_shared(), pgstat_reset_matching_entries(), pgstat_reset_slru_counter_internal(), pgstat_slru_flush(), pgstat_slru_snapshot_cb(), pgstat_wal_reset_all_cb(), pgstat_wal_snapshot_cb(), 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(), ReachedEndOfBackup(), read_relmap_file(), ReadBuffer_common(), ReadMultiXactCounts(), ReadMultiXactIdRange(), ReadNextFullTransactionId(), ReadNextMultiXactId(), ReadReplicationSlot(), RecordNewMultiXact(), RecoverPreparedTransactions(), RegisterDynamicBackgroundWorker(), RegisterPredicateLockingXid(), RelationCacheInitFilePreInvalidate(), ReleaseOneSerializableXact(), ReleasePredicateLocks(), relmap_redo(), RemoveScratchTarget(), ReplicationOriginExitCleanup(), ReplicationSlotAcquire(), ReplicationSlotCleanup(), ReplicationSlotCreate(), ReplicationSlotDropPtr(), ReplicationSlotName(), ReplicationSlotRelease(), ReplicationSlotsComputeLogicalRestartLSN(), ReplicationSlotsComputeRequiredLSN(), ReplicationSlotsComputeRequiredXmin(), ReplicationSlotsCountDBSlots(), ReplicationSlotsDropDBSlots(), replorigin_advance(), replorigin_get_progress(), replorigin_session_advance(), replorigin_session_get_progress(), replorigin_session_reset(), replorigin_session_setup(), replorigin_state_clear(), resize(), RestoreScratchTarget(), restoreTwoPhaseData(), SaveSlotToPath(), SearchNamedReplicationSlot(), SerialAdd(), SerialGetMinConflictCommitSeqNo(), SerialSetActiveSerXmin(), set_indexsafe_procflags(), SetCommitTsLimit(), SetInstallXLogFileSegmentActive(), SetMultiXactIdLimit(), SetNextObjectId(), SetOffsetVacuumLimit(), SetTransactionIdLimit(), SetXidCommitTsInPage(), SharedInvalBackendInit(), ShmemInitStruct(), SICleanupQueue(), SIGetDataEntries(), SignalBackends(), SignalVirtualTransaction(), SIInsertDataEntries(), SimpleLruReadPage(), SimpleLruReadPage_ReadOnly(), SimpleLruTruncate(), SimpleLruWaitIO(), SimpleLruWriteAll(), SlruDeleteSegment(), SlruInternalWritePage(), SnapBuildInitialSnapshot(), ss_get_location(), StandbyRecoverPreparedTransactions(), StartupCLOG(), StartupDecodingContext(), StartupSUBTRANS(), StartupXLOG(), sts_parallel_scan_next(), SubTransSetParent(), SummarizeOldestCommittedSxact(), SwitchIntoArchiveRecovery(), SyncOneBuffer(), SyncRepCancelWait(), SyncRepCleanupAtProcExit(), SyncRepReleaseWaiters(), SyncRepUpdateSyncStandbysDefined(), SyncRepWaitForLSN(), TablespaceCreateDbspace(), tbm_shared_iterate(), TerminateBackgroundWorker(), TerminateOtherDBBackends(), test_slru_page_exists(), test_slru_page_read(), test_slru_page_write(), TransactionGroupUpdateXidStatus(), TransactionIdGetCommitTsData(), TransactionIdIsActive(), TransactionIdIsInProgress(), TransactionIdSetPageStatus(), TransactionTreeSetCommitTsData(), TransferPredicateLocksToNewTarget(), TrimCLOG(), TrimMultiXact(), TruncateMultiXact(), TwoPhaseGetGXact(), TwoPhaseGetXidByVirtualXID(), update_cached_xid_range(), UpdateMinRecoveryPoint(), vac_truncate_clog(), vacuum_rel(), VirtualXactLock(), VirtualXactLockTableCleanup(), VirtualXactLockTableInsert(), wait_for_relation_state_change(), wait_for_worker_state_change(), WaitForReplicationWorkerAttach(), WALInsertLockAcquire(), WALInsertLockAcquireExclusive(), write_relcache_init_file(), xact_redo(), XidCacheRemoveRunningXids(), xlog_redo(), XLogBackgroundFlush(), XLogReportParameters(), and XLogShutdownWalRcv().

◆ LWLockAcquireOrWait()

bool LWLockAcquireOrWait	(	LWLock *	lock,
		LWLockMode	mode
	)

Definition at line 1423 of file lwlock.c.

 {
     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.
              */
             LOG_LWDEBUG("LWLockAcquireOrWait", lock, "waiting");
  
 #ifdef LWLOCK_STATS
             lwstats->block_count++;
 #endif
  
             LWLockReportWaitStart(lock);
             if (TRACE_POSTGRESQL_LWLOCK_WAIT_START_ENABLED())
                 TRACE_POSTGRESQL_LWLOCK_WAIT_START(T_NAME(lock), mode);
  
             for (;;)
             {
                 PGSemaphoreLock(proc->sem);
                 if (proc->lwWaiting == LW_WS_NOT_WAITING)
                     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
             if (TRACE_POSTGRESQL_LWLOCK_WAIT_DONE_ENABLED())
                 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");
         if (TRACE_POSTGRESQL_LWLOCK_ACQUIRE_OR_WAIT_FAIL_ENABLED())
             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;
         if (TRACE_POSTGRESQL_LWLOCK_ACQUIRE_OR_WAIT_ENABLED())
             TRACE_POSTGRESQL_LWLOCK_ACQUIRE_OR_WAIT(T_NAME(lock), mode);
     }
  
     return !mustwait;
 }

References Assert(), elog(), ERROR, held_lwlocks, HOLD_INTERRUPTS, LWLockHandle::lock, LOG_LWDEBUG, LW_EXCLUSIVE, LW_SHARED, LW_WAIT_UNTIL_FREE, LW_WS_NOT_WAITING, LWLockAttemptLock(), LWLockDequeueSelf(), LWLockQueueSelf(), LWLockReportWaitEnd(), LWLockReportWaitStart(), PGPROC::lwWaiting, MAX_BACKENDS, MAX_SIMUL_LWLOCKS, LWLockHandle::mode, 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().

◆ LWLockAnyHeldByMe()

bool LWLockAnyHeldByMe	(	LWLock *	lock,
		int	nlocks,
		size_t	stride
	)

Definition at line 1937 of file lwlock.c.

 {
     char       *held_lock_addr;
     char       *begin;
     char       *end;
     int         i;
  
     begin = (char *) lock;
     end = begin + nlocks * stride;
     for (i = 0; i < num_held_lwlocks; i++)
     {
         held_lock_addr = (char *) held_lwlocks[i].lock;
         if (held_lock_addr >= begin &&
             held_lock_addr < end &&
             (held_lock_addr - begin) % stride == 0)
             return true;
     }
     return false;
 }

References held_lwlocks, i, and num_held_lwlocks.

◆ LWLockAttemptLock()

static bool LWLockAttemptLock	(	LWLock *	lock,
		LWLockMode	mode
	)

static

Definition at line 811 of file lwlock.c.

 {
     uint32      old_state;
  
     Assert(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();
 }

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

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

◆ LWLockConditionalAcquire()

bool LWLockConditionalAcquire	(	LWLock *	lock,
		LWLockMode	mode
	)

Definition at line 1366 of file lwlock.c.

 {
     bool        mustwait;
  
     Assert(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");
         if (TRACE_POSTGRESQL_LWLOCK_CONDACQUIRE_FAIL_ENABLED())
             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;
         if (TRACE_POSTGRESQL_LWLOCK_CONDACQUIRE_ENABLED())
             TRACE_POSTGRESQL_LWLOCK_CONDACQUIRE(T_NAME(lock), mode);
     }
     return !mustwait;
 }

References Assert(), elog(), ERROR, held_lwlocks, HOLD_INTERRUPTS, LWLockHandle::lock, LOG_LWDEBUG, LW_EXCLUSIVE, LW_SHARED, LWLockAttemptLock(), MAX_SIMUL_LWLOCKS, LWLockHandle::mode, mode, num_held_lwlocks, PRINT_LWDEBUG, RESUME_INTERRUPTS, and T_NAME.

Referenced by BufferAlloc(), ConditionalLockBuffer(), pgstat_flush_io(), pgstat_flush_wal(), pgstat_lock_entry(), pgstat_lock_entry_shared(), pgstat_slru_flush(), ProcArrayEndTransaction(), SimpleLruWaitIO(), ss_report_location(), TransactionIdSetPageStatus(), and XLogNeedsFlush().

◆ LWLockConflictsWithVar()

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

static

Definition at line 1550 of file lwlock.c.

 {
     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;
 }

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

Referenced by LWLockWaitForVar().

◆ LWLockDequeueSelf()

static void LWLockDequeueSelf ( LWLock * lock )

static

Definition at line 1106 of file lwlock.c.

 {
     bool        on_waitlist;
  
 #ifdef LWLOCK_STATS
     lwlock_stats *lwstats;
  
     lwstats = get_lwlock_stats_entry(lock);
  
     lwstats->dequeue_self_count++;
 #endif
  
     LWLockWaitListLock(lock);
  
     /*
      * Remove ourselves from the waitlist, unless we've already been
      * removed. The removal happens with the wait list lock held, so there's
      * no race in this check.
      */
     on_waitlist = MyProc->lwWaiting == LW_WS_WAITING;
     if (on_waitlist)
         proclist_delete(&lock->waiters, MyProc->pgprocno, lwWaitLink);
  
     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 (on_waitlist)
         MyProc->lwWaiting = LW_WS_NOT_WAITING;
     else
     {
         int         extraWaits = 0;
  
         /*
          * Somebody else dequeued us and has or will wake us up. Deal with the
          * superfluous absorption of a wakeup.
          */
  
         /*
          * Reset RELEASE_OK flag 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 == LW_WS_NOT_WAITING)
                 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
 }

References Assert(), LW_FLAG_HAS_WAITERS, LW_FLAG_RELEASE_OK, LW_WS_NOT_WAITING, LW_WS_WAITING, 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_is_empty(), PGPROC::sem, LWLock::state, and LWLock::waiters.

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

◆ LWLockHeldByMe()

bool LWLockHeldByMe ( LWLock * lock )

Definition at line 1919 of file lwlock.c.

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

References held_lwlocks, i, and num_held_lwlocks.

Referenced by alloc_object(), check_for_freed_segments_locked(), CompactCheckpointerRequestQueue(), delete_item(), DeleteLockTarget(), dshash_dump(), ensure_active_superblock(), FlushOneBuffer(), get_best_segment(), GetOldestSafeDecodingTransactionId(), GetSnapshotDataReuse(), init_span(), InvalidatePossiblyObsoleteSlot(), logicalrep_pa_worker_count(), logicalrep_sync_worker_count(), logicalrep_worker_find(), logicalrep_worker_wakeup_ptr(), logicalrep_workers_find(), MaintainLatestCompletedXid(), MaintainLatestCompletedXidRecovery(), make_new_segment(), MarkBufferDirtyHint(), OnConflict_CheckForSerializationFailure(), ProcArrayEndTransaction(), ProcArraySetReplicationSlotXmin(), ReleaseOneSerializableXact(), RemoveScratchTarget(), RemoveTargetIfNoLongerUsed(), resize(), RestoreScratchTarget(), SetNewSxactGlobalXmin(), test_slru_page_readonly(), TransactionIdInRecentPast(), TwoPhaseGetGXact(), and UnpinBuffer().

◆ LWLockHeldByMeInMode()

bool LWLockHeldByMeInMode	(	LWLock *	lock,
		LWLockMode	mode
	)

Definition at line 1963 of file lwlock.c.

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

References held_lwlocks, i, mode, and num_held_lwlocks.

Referenced by DeleteLockTarget(), dshash_delete_current(), dshash_delete_entry(), dshash_seq_next(), InvalidatePossiblyObsoleteSlot(), IsBufferCleanupOK(), logicalrep_worker_cleanup(), logicalrep_worker_stop_internal(), MarkAsPreparingGuts(), MarkBufferDirty(), PrepareRedoAdd(), PrepareRedoRemove(), ProcArrayEndTransactionInternal(), ProcessTwoPhaseBuffer(), RemoveGXact(), SyncRepWakeQueue(), TransactionIdSetPageStatusInternal(), and TransferPredicateLocksToNewTarget().

◆ LWLockInitialize()

void LWLockInitialize	(	LWLock *	lock,
		int	tranche_id
	)

Definition at line 730 of file lwlock.c.

 {
     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);
 }

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(), pgstat_init_entry(), ReplicationOriginShmemInit(), ReplicationSlotsShmemInit(), SimpleLruInit(), StatsShmemInit(), sts_initialize(), tbm_prepare_shared_iterate(), test_slru_shmem_startup(), and XLOGShmemInit().

◆ LWLockNewTrancheId()

int LWLockNewTrancheId ( void )

Definition at line 627 of file lwlock.c.

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

References MainLWLockArray, ShmemLock, SpinLockAcquire, and SpinLockRelease.

Referenced by apw_init_shmem(), InitializeLWLocks(), and test_slru_shmem_startup().

◆ LWLockQueueSelf()

static void LWLockQueueSelf	(	LWLock *	lock,
		LWLockMode	mode
	)

static

Definition at line 1063 of file lwlock.c.

 {
     /*
      * 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 != LW_WS_NOT_WAITING)
         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 = LW_WS_WAITING;
     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
 }

References elog(), LW_FLAG_HAS_WAITERS, LW_WAIT_UNTIL_FREE, LW_WS_NOT_WAITING, LW_WS_WAITING, LWLockWaitListLock(), LWLockWaitListUnlock(), PGPROC::lwWaiting, PGPROC::lwWaitMode, 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().

◆ LWLockRegisterTranche()

void LWLockRegisterTranche	(	int	tranche_id,
		const char *	tranche_name
	)

Definition at line 651 of file lwlock.c.

 {
     /* This should only be called for user-defined tranches. */
     if (tranche_id < LWTRANCHE_FIRST_USER_DEFINED)
         return;
  
     /* Convert to array index. */
     tranche_id -= LWTRANCHE_FIRST_USER_DEFINED;
  
     /* If necessary, create or enlarge array. */
     if (tranche_id >= LWLockTrancheNamesAllocated)
     {
         int         newalloc;
  
         newalloc = pg_nextpower2_32(Max(8, tranche_id + 1));
  
         if (LWLockTrancheNames == NULL)
             LWLockTrancheNames = (const char **)
                 MemoryContextAllocZero(TopMemoryContext,
                                        newalloc * sizeof(char *));
         else
             LWLockTrancheNames =
                 repalloc0_array(LWLockTrancheNames, const char *, LWLockTrancheNamesAllocated, newalloc);
         LWLockTrancheNamesAllocated = newalloc;
     }
  
     LWLockTrancheNames[tranche_id] = tranche_name;
 }

References LWLockTrancheNames, LWLockTrancheNamesAllocated, LWTRANCHE_FIRST_USER_DEFINED, Max, MemoryContextAllocZero(), pg_nextpower2_32(), repalloc0_array, and TopMemoryContext.

Referenced by apw_init_shmem(), CreateLWLocks(), and test_slru_shmem_startup().

◆ LWLockRelease()

void LWLockRelease ( LWLock * lock )

Definition at line 1803 of file lwlock.c.

 {
     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));
  
     if (TRACE_POSTGRESQL_LWLOCK_RELEASE_ENABLED())
         TRACE_POSTGRESQL_LWLOCK_RELEASE(T_NAME(lock));
  
     /*
      * 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);
     }
  
     /*
      * Now okay to allow cancel/die interrupts.
      */
     RESUME_INTERRUPTS();
 }

References Assert(), elog(), ERROR, held_lwlocks, 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, mode, num_held_lwlocks, pg_atomic_sub_fetch_u32(), PRINT_LWDEBUG, RESUME_INTERRUPTS, LWLock::state, 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(), AtEOXact_LogicalRepWorkers(), 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(), 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_backup_start(), do_pg_backup_stop(), 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(), dshash_seq_next(), dshash_seq_term(), 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(), FindAndDropRelationBuffers(), FinishPreparedTransaction(), FlushDatabaseBuffers(), FlushRelationBuffers(), FlushRelationsAllBuffers(), ForceTransactionIdLimitUpdate(), ForwardSyncRequest(), FreeWorkerInfo(), GetBackgroundWorkerPid(), GetBackgroundWorkerTypeByPid(), GetBlockerStatusData(), GetConflictingVirtualXIDs(), GetCurrentVirtualXIDs(), GetLastImportantRecPtr(), GetLastSegSwitchData(), GetLatestCommitTsData(), GetLeaderApplyWorkerPid(), 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(), InvalidatePossiblyObsoleteSlot(), IsInstallXLogFileSegmentActive(), KnownAssignedXidsCompress(), KnownAssignedXidsReset(), lock_twophase_recover(), LockAcquireExtended(), LockBuffer(), LockErrorCleanup(), LockGXact(), LockHasWaiters(), LockRefindAndRelease(), LockRelease(), LockReleaseAll(), LockWaiterCount(), logicalrep_launcher_attach_dshmem(), logicalrep_pa_worker_stop(), logicalrep_worker_attach(), logicalrep_worker_detach(), logicalrep_worker_launch(), logicalrep_worker_stop(), logicalrep_worker_stop_internal(), logicalrep_worker_wakeup(), LogStandbySnapshot(), LookupGXact(), 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_archiver_reset_all_cb(), pgstat_archiver_snapshot_cb(), pgstat_bgwriter_reset_all_cb(), pgstat_bgwriter_snapshot_cb(), pgstat_build_snapshot(), pgstat_checkpointer_reset_all_cb(), pgstat_checkpointer_snapshot_cb(), pgstat_flush_io(), pgstat_flush_wal(), pgstat_io_reset_all_cb(), pgstat_io_snapshot_cb(), pgstat_reset_matching_entries(), pgstat_reset_slru_counter_internal(), pgstat_slru_flush(), pgstat_slru_snapshot_cb(), pgstat_unlock_entry(), pgstat_wal_reset_all_cb(), pgstat_wal_snapshot_cb(), 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(), ReachedEndOfBackup(), read_relmap_file(), ReadMultiXactCounts(), ReadMultiXactIdRange(), ReadNextFullTransactionId(), ReadNextMultiXactId(), ReadReplicationSlot(), RecordNewMultiXact(), RecoverPreparedTransactions(), RegisterDynamicBackgroundWorker(), RegisterPredicateLockingXid(), RelationCacheInitFilePostInvalidate(), ReleaseOneSerializableXact(), ReleasePredicateLocks(), relmap_redo(), RemoveScratchTarget(), ReplicationOriginExitCleanup(), ReplicationSlotAcquire(), ReplicationSlotCleanup(), ReplicationSlotCreate(), ReplicationSlotDropPtr(), ReplicationSlotName(), ReplicationSlotRelease(), ReplicationSlotsComputeLogicalRestartLSN(), ReplicationSlotsComputeRequiredLSN(), ReplicationSlotsComputeRequiredXmin(), ReplicationSlotsCountDBSlots(), ReplicationSlotsDropDBSlots(), replorigin_advance(), replorigin_get_progress(), replorigin_session_advance(), replorigin_session_get_progress(), replorigin_session_reset(), replorigin_session_setup(), replorigin_state_clear(), resize(), RestoreScratchTarget(), restoreTwoPhaseData(), SaveSlotToPath(), SearchNamedReplicationSlot(), SerialAdd(), SerialGetMinConflictCommitSeqNo(), SerialSetActiveSerXmin(), set_indexsafe_procflags(), SetCommitTsLimit(), SetInstallXLogFileSegmentActive(), SetMultiXactIdLimit(), SetNextObjectId(), 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(), StartupCLOG(), StartupDecodingContext(), StartupSUBTRANS(), StartupXLOG(), sts_parallel_scan_next(), SubTransGetParent(), SubTransSetParent(), SummarizeOldestCommittedSxact(), SwitchIntoArchiveRecovery(), SyncOneBuffer(), SyncRepCancelWait(), SyncRepCleanupAtProcExit(), SyncRepReleaseWaiters(), SyncRepUpdateSyncStandbysDefined(), SyncRepWaitForLSN(), TablespaceCreateDbspace(), tbm_shared_iterate(), TerminateBackgroundWorker(), TerminateOtherDBBackends(), test_slru_page_exists(), test_slru_page_read(), test_slru_page_readonly(), test_slru_page_write(), TransactionGroupUpdateXidStatus(), TransactionIdGetCommitTsData(), TransactionIdGetStatus(), TransactionIdIsActive(), TransactionIdIsInProgress(), TransactionIdSetPageStatus(), TransactionTreeSetCommitTsData(), TransferPredicateLocksToNewTarget(), TrimCLOG(), TrimMultiXact(), TruncateMultiXact(), TwoPhaseGetGXact(), TwoPhaseGetXidByVirtualXID(), update_cached_xid_range(), UpdateMinRecoveryPoint(), vac_truncate_clog(), vacuum_rel(), VirtualXactLock(), VirtualXactLockTableCleanup(), VirtualXactLockTableInsert(), wait_for_relation_state_change(), wait_for_worker_state_change(), WaitForReplicationWorkerAttach(), WaitOnLock(), write_relcache_init_file(), xact_redo(), XidCacheRemoveRunningXids(), xlog_redo(), XLogBackgroundFlush(), XLogFlush(), XLogNeedsFlush(), XLogReportParameters(), and XLogShutdownWalRcv().

◆ LWLockReleaseAll()

void LWLockReleaseAll ( void )

Definition at line 1902 of file lwlock.c.

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

References held_lwlocks, HOLD_INTERRUPTS, LWLockRelease(), and num_held_lwlocks.

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

◆ LWLockReleaseClearVar()

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

Definition at line 1876 of file lwlock.c.

 {
     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);
 }

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

Referenced by WALInsertLockRelease().

◆ LWLockReportWaitEnd()

static void LWLockReportWaitEnd ( void )

inlinestatic

Definition at line 757 of file lwlock.c.

 {
     pgstat_report_wait_end();
 }

References pgstat_report_wait_end().

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

◆ LWLockReportWaitStart()

static void LWLockReportWaitStart ( LWLock * lock )

inlinestatic

Definition at line 748 of file lwlock.c.

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

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

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

◆ LWLockShmemSize()

Size LWLockShmemSize ( void )

Definition at line 444 of file lwlock.c.

 {
     Size        size;
     int         i;
     int         numLocks = NUM_FIXED_LWLOCKS;
  
     /* Calculate total number of locks needed in the main array. */
     numLocks += NumLWLocksForNamedTranches();
  
     /* 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);
  
     return size;
 }

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

Referenced by CalculateShmemSize(), and CreateLWLocks().

◆ LWLockUpdateVar()

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

Definition at line 1745 of file lwlock.c.

 {
     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);
  
         /* see LWLockWakeup() */
         Assert(waiter->lwWaiting == LW_WS_WAITING);
         waiter->lwWaiting = LW_WS_PENDING_WAKEUP;
     }
  
     /* 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 = LW_WS_NOT_WAITING;
         PGSemaphoreUnlock(waiter->sem);
     }
 }

References Assert(), proclist_mutable_iter::cur, GetPGProcByNumber, LW_EXCLUSIVE, LW_VAL_EXCLUSIVE, LW_WAIT_UNTIL_FREE, LW_WS_NOT_WAITING, LW_WS_PENDING_WAKEUP, LW_WS_WAITING, 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, LWLock::waiters, and wakeup.

Referenced by WALInsertLockAcquireExclusive(), and WALInsertLockUpdateInsertingAt().

◆ LWLockWaitForVar()

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

Definition at line 1610 of file lwlock.c.

 {
     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.
          *
          * 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.
          */
         LOG_LWDEBUG("LWLockWaitForVar", lock, "waiting");
  
 #ifdef LWLOCK_STATS
         lwstats->block_count++;
 #endif
  
         LWLockReportWaitStart(lock);
         if (TRACE_POSTGRESQL_LWLOCK_WAIT_START_ENABLED())
             TRACE_POSTGRESQL_LWLOCK_WAIT_START(T_NAME(lock), LW_EXCLUSIVE);
  
         for (;;)
         {
             PGSemaphoreLock(proc->sem);
             if (proc->lwWaiting == LW_WS_NOT_WAITING)
                 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
  
         if (TRACE_POSTGRESQL_LWLOCK_WAIT_DONE_ENABLED())
             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. */
     }
  
     /*
      * 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;
 }

References Assert(), HOLD_INTERRUPTS, LOG_LWDEBUG, LW_EXCLUSIVE, LW_FLAG_RELEASE_OK, LW_WAIT_UNTIL_FREE, LW_WS_NOT_WAITING, LWLockConflictsWithVar(), LWLockDequeueSelf(), LWLockQueueSelf(), LWLockReportWaitEnd(), LWLockReportWaitStart(), PGPROC::lwWaiting, MAX_BACKENDS, MyProc, newval, 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().

◆ LWLockWaitListLock()

static void LWLockWaitListLock ( LWLock * lock )

static

Definition at line 882 of file lwlock.c.

 {
     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
 }

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().

◆ LWLockWaitListUnlock()

static void LWLockWaitListUnlock ( LWLock * lock )

static

Definition at line 934 of file lwlock.c.

 {
     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);
 }

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().

◆ LWLockWakeup()

static void LWLockWakeup ( LWLock * lock )

static

Definition at line 947 of file lwlock.c.

 {
     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;
         }
  
         /*
          * Signal that the process isn't on the wait list anymore. This allows
          * LWLockDequeueSelf() to remove itself of the waitlist with a
          * proclist_delete(), rather than having to check if it has been
          * removed from the list.
          */
         Assert(waiter->lwWaiting == LW_WS_WAITING);
         waiter->lwWaiting = LW_WS_PENDING_WAKEUP;
  
         /*
          * 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 = LW_WS_NOT_WAITING;
         PGSemaphoreUnlock(waiter->sem);
     }
 }

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, LW_WS_NOT_WAITING, LW_WS_PENDING_WAKEUP, LW_WS_WAITING, 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, LWLock::waiters, and wakeup.

Referenced by LWLockRelease().

◆ NumLWLocksForNamedTranches()

static int NumLWLocksForNamedTranches ( void )

static

Definition at line 429 of file lwlock.c.

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

References i, NamedLWLockTrancheRequestArray, and NamedLWLockTrancheRequests.

Referenced by InitializeLWLocks(), and LWLockShmemSize().

◆ RequestNamedLWLockTranche()

void RequestNamedLWLockTranche	(	const char *	tranche_name,
		int	num_lwlocks
	)

Definition at line 693 of file lwlock.c.

 {
     NamedLWLockTrancheRequest *request;
  
     if (!process_shmem_requests_in_progress)
         elog(FATAL, "cannot request additional LWLocks outside shmem_request_hook");
  
     if (NamedLWLockTrancheRequestArray == NULL)
     {
         NamedLWLockTrancheRequestsAllocated = 16;
         NamedLWLockTrancheRequestArray = (NamedLWLockTrancheRequest *)
             MemoryContextAlloc(TopMemoryContext,
                                NamedLWLockTrancheRequestsAllocated
                                * sizeof(NamedLWLockTrancheRequest));
     }
  
     if (NamedLWLockTrancheRequests >= NamedLWLockTrancheRequestsAllocated)
     {
         int         i = pg_nextpower2_32(NamedLWLockTrancheRequests + 1);
  
         NamedLWLockTrancheRequestArray = (NamedLWLockTrancheRequest *)
             repalloc(NamedLWLockTrancheRequestArray,
                      i * sizeof(NamedLWLockTrancheRequest));
         NamedLWLockTrancheRequestsAllocated = i;
     }
  
     request = &NamedLWLockTrancheRequestArray[NamedLWLockTrancheRequests];
     Assert(strlen(tranche_name) + 1 <= NAMEDATALEN);
     strlcpy(request->tranche_name, tranche_name, NAMEDATALEN);
     request->num_lwlocks = num_lwlocks;
     NamedLWLockTrancheRequests++;
 }

References Assert(), elog(), FATAL, i, MemoryContextAlloc(), NAMEDATALEN, NamedLWLockTrancheRequestArray, NamedLWLockTrancheRequests, NamedLWLockTrancheRequestsAllocated, NamedLWLockTrancheRequest::num_lwlocks, pg_nextpower2_32(), process_shmem_requests_in_progress, repalloc(), strlcpy(), TopMemoryContext, and NamedLWLockTrancheRequest::tranche_name.

Referenced by pgss_shmem_request().

◆ StaticAssertDecl() [1/2]

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

◆ StaticAssertDecl() [2/2]

StaticAssertDecl	(	LW_VAL_EXCLUSIVE	,
		(uint32)	MAX_BACKENDS,
		"MAX_BACKENDS too big for lwlock.c"
	)

Variable Documentation

◆ BuiltinTrancheNames

const char* const BuiltinTrancheNames[]

static

Definition at line 134 of file lwlock.c.

Referenced by GetLWTrancheName().

◆ held_lwlocks

LWLockHandle held_lwlocks[MAX_SIMUL_LWLOCKS]

static

Definition at line 230 of file lwlock.c.

Referenced by LWLockAcquire(), LWLockAcquireOrWait(), LWLockAnyHeldByMe(), LWLockConditionalAcquire(), LWLockHeldByMe(), LWLockHeldByMeInMode(), LWLockRelease(), and LWLockReleaseAll().

◆ IndividualLWLockNames

const char* const IndividualLWLockNames[]

extern

Referenced by GetLWTrancheName().

◆ LWLockTrancheNames

const char** LWLockTrancheNames = NULL

static

Definition at line 204 of file lwlock.c.

Referenced by GetLWTrancheName(), and LWLockRegisterTranche().

◆ LWLockTrancheNamesAllocated

int LWLockTrancheNamesAllocated = 0

static

Definition at line 205 of file lwlock.c.

Referenced by GetLWTrancheName(), and LWLockRegisterTranche().

◆ MainLWLockArray

LWLockPadded* MainLWLockArray = NULL

Definition at line 212 of file lwlock.c.

Referenced by BufMappingPartitionLock(), BufMappingPartitionLockByIndex(), CreateLWLocks(), GetNamedLWLockTranche(), InitializeLWLocks(), and LWLockNewTrancheId().

◆ NamedLWLockTrancheArray

NamedLWLockTranche* NamedLWLockTrancheArray = NULL

Definition at line 251 of file lwlock.c.

Referenced by CreateLWLocks(), and InitializeLWLocks().

◆ NamedLWLockTrancheRequestArray

NamedLWLockTrancheRequest* NamedLWLockTrancheRequestArray = NULL

static

Definition at line 239 of file lwlock.c.

Referenced by GetNamedLWLockTranche(), InitializeLWLocks(), LWLockShmemSize(), NumLWLocksForNamedTranches(), and RequestNamedLWLockTranche().

◆ NamedLWLockTrancheRequests

int NamedLWLockTrancheRequests = 0

Definition at line 248 of file lwlock.c.

Referenced by CreateLWLocks(), GetNamedLWLockTranche(), InitializeLWLocks(), LWLockShmemSize(), NumLWLocksForNamedTranches(), and RequestNamedLWLockTranche().

◆ NamedLWLockTrancheRequestsAllocated

int NamedLWLockTrancheRequestsAllocated = 0

static

Definition at line 240 of file lwlock.c.

Referenced by RequestNamedLWLockTranche().

◆ num_held_lwlocks

int num_held_lwlocks = 0

static

Definition at line 229 of file lwlock.c.

Referenced by LWLockAcquire(), LWLockAcquireOrWait(), LWLockAnyHeldByMe(), LWLockConditionalAcquire(), LWLockHeldByMe(), LWLockHeldByMeInMode(), LWLockRelease(), and LWLockReleaseAll().

◆ ShmemLock

slock_t* ShmemLock

extern

Definition at line 88 of file shmem.c.

Referenced by InitShmemAllocation(), LWLockNewTrancheId(), and ShmemAllocRaw().

Data Structures

Macros

Typedefs

Functions

Variables

Macro Definition Documentation

◆ LOG_LWDEBUG

◆ LW_FLAG_HAS_WAITERS

◆ LW_FLAG_LOCKED

◆ LW_FLAG_RELEASE_OK

◆ LW_LOCK_MASK

◆ LW_SHARED_MASK

◆ LW_VAL_EXCLUSIVE

◆ LW_VAL_SHARED

◆ MAX_SIMUL_LWLOCKS

◆ PRINT_LWDEBUG

◆ T_NAME

Typedef Documentation

◆ LWLockHandle

◆ NamedLWLockTrancheRequest

Function Documentation

◆ CreateLWLocks()

◆ GetLWLockIdentifier()

◆ GetLWTrancheName()

◆ GetNamedLWLockTranche()

◆ InitializeLWLocks()

◆ InitLWLockAccess()

◆ LWLockAcquire()

◆ LWLockAcquireOrWait()

◆ LWLockAnyHeldByMe()

◆ LWLockAttemptLock()

◆ LWLockConditionalAcquire()

◆ LWLockConflictsWithVar()

◆ LWLockDequeueSelf()

◆ LWLockHeldByMe()

◆ LWLockHeldByMeInMode()

◆ LWLockInitialize()

◆ LWLockNewTrancheId()

◆ LWLockQueueSelf()

◆ LWLockRegisterTranche()

◆ LWLockRelease()

◆ LWLockReleaseAll()

◆ LWLockReleaseClearVar()

◆ LWLockReportWaitEnd()

◆ LWLockReportWaitStart()

◆ LWLockShmemSize()

◆ LWLockUpdateVar()

◆ LWLockWaitForVar()

◆ LWLockWaitListLock()

◆ LWLockWaitListUnlock()

◆ LWLockWakeup()

◆ NumLWLocksForNamedTranches()

◆ RequestNamedLWLockTranche()

◆ StaticAssertDecl() [1/2]

◆ StaticAssertDecl() [2/2]

Variable Documentation

◆ BuiltinTrancheNames

◆ held_lwlocks

◆ IndividualLWLockNames

◆ LWLockTrancheNames

◆ LWLockTrancheNamesAllocated

◆ MainLWLockArray

◆ NamedLWLockTrancheArray

◆ NamedLWLockTrancheRequestArray

◆ NamedLWLockTrancheRequests

◆ NamedLWLockTrancheRequestsAllocated

◆ num_held_lwlocks

◆ ShmemLock