lwlock.c File Reference

#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:

Go to the source code of this file.

Data Structures
struct	LWLockHandle
struct	NamedLWLockTrancheRequest

Macros
#define	LW_FLAG_HAS_WAITERS   ((uint32) 1 << 30)
#define	LW_FLAG_RELEASE_OK   ((uint32) 1 << 29)
#define	LW_FLAG_LOCKED   ((uint32) 1 << 28)
#define	LW_VAL_EXCLUSIVE   ((uint32) 1 << 24)
#define	LW_VAL_SHARED   1
#define	LW_LOCK_MASK   ((uint32) ((1 << 25)-1))
#define	LW_SHARED_MASK   ((uint32) ((1 << 24)-1))
#define	MAX_SIMUL_LWLOCKS   200
#define	T_NAME(lock)    GetLWTrancheName((lock)->tranche)
#define	PRINT_LWDEBUG(a, b, c)   ((void)0)
#define	LOG_LWDEBUG(a, b, c)   ((void)0)

Typedefs
typedef struct LWLockHandle	LWLockHandle
typedef struct NamedLWLockTrancheRequest	NamedLWLockTrancheRequest

Functions
	StaticAssertDecl (lengthof(BuiltinTrancheNames)==LWTRANCHE_FIRST_USER_DEFINED - NUM_INDIVIDUAL_LWLOCKS, "missing entries in BuiltinTrancheNames[]")
static void	InitializeLWLocks (void)
static void	LWLockReportWaitStart (LWLock *lock)
static void	LWLockReportWaitEnd (void)
static const char *	GetLWTrancheName (uint16 trancheId)
static int	NumLWLocksForNamedTranches (void)
Size	LWLockShmemSize (void)
void	CreateLWLocks (void)
void	InitLWLockAccess (void)
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 *l)
bool	LWLockHeldByMeInMode (LWLock *l, 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
static bool	lock_named_request_allowed = true

Macro Definition Documentation

LOG_LWDEBUG

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

Definition at line 312 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 207 of file lwlock.c.

PRINT_LWDEBUG

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

Definition at line 311 of file lwlock.c.

T_NAME

#define T_NAME

(

lock

)

GetLWTrancheName((lock)->tranche)

Definition at line 247 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 466 of file lwlock.c.

{
    StaticAssertStmt(LW_VAL_EXCLUSIVE > (uint32) MAX_BACKENDS,
                     "MAX_BACKENDS too big for lwlock.c");
 
    StaticAssertStmt(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 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, LW_VAL_EXCLUSIVE, LWLOCK_PADDED_SIZE, LWLockRegisterTranche(), LWLockShmemSize(), LWTRANCHE_FIRST_USER_DEFINED, MainLWLockArray, MAX_BACKENDS, NamedLWLockTrancheArray, NamedLWLockTrancheRequests, ShmemAlloc(), and StaticAssertStmt.

Referenced by CreateSharedMemoryAndSemaphores().

GetLWLockIdentifier()

const char* GetLWLockIdentifier	(	uint32	classId,
		uint16	eventId
	)

Definition at line 800 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 772 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 595 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 512 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 579 of file lwlock.c.

{
#ifdef LWLOCK_STATS
    init_lwlock_stats();
#endif
}

Referenced by InitProcess().

LWLockAcquire()

bool LWLockAcquire	(	LWLock *	lock,
		LWLockMode	mode
	)

Definition at line 1199 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
 
    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.
         *
         * 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)
                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(), AssertArg, elog, ERROR, held_lwlocks, 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, 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(), AtPrepare_PredicateLocks(), attach_internal(), autoprewarm_main(), autoprewarm_start_worker(), AutoVacLauncherMain(), AutoVacuumRequestWork(), AutoVacWorkerMain(), BackendIdGetProc(), BackendIdGetTransactionIds(), BackendPidGetProc(), BackendXidGetPid(), BecomeLockGroupLeader(), BecomeLockGroupMember(), BootStrapCLOG(), BootStrapMultiXact(), BootStrapSUBTRANS(), BootStrapXLOG(), BufferAlloc(), CancelDBBackends(), check_for_freed_segments(), CheckDeadLock(), CheckForSerializableConflictOut(), CheckPointPredicate(), CheckPointRelationMap(), CheckPointReplicationOrigin(), CheckPointReplicationSlots(), CheckPointTwoPhase(), CheckRecoveryConsistency(), CheckTableForSerializableConflictIn(), CheckTargetForConflictsIn(), choose_next_subplan_for_leader(), choose_next_subplan_for_worker(), CleanupInvalidationState(), ClearOldPredicateLocks(), clog_redo(), commit_ts_redo(), ComputeXidHorizons(), copy_replication_slot(), CountDBBackends(), CountDBConnections(), CountOtherDBBackends(), CountUserBackends(), CreateCheckPoint(), CreateEndOfRecoveryRecord(), CreateInitDecodingContext(), CreatePredicateLock(), CreateRestartPoint(), DeactivateCommitTs(), DeleteChildTargetLocks(), DeleteLockTarget(), destroy_superblock(), do_autovacuum(), do_pg_start_backup(), do_pg_stop_backup(), do_start_worker(), DropAllPredicateLocksFromTable(), DropSubscription(), DropTableSpace(), dsa_allocate_extended(), dsa_dump(), dsa_free(), dsa_pin(), dsa_release_in_place(), dsa_set_size_limit(), dsa_trim(), dsa_unpin(), dshash_delete_key(), dshash_dump(), dshash_find(), dshash_find_or_insert(), dsm_attach(), dsm_create(), dsm_detach(), dsm_pin_segment(), dsm_unpin_segment(), ensure_active_superblock(), entry_reset(), Exec_ListenPreCommit(), ExecParallelHashMergeCounters(), ExecParallelHashPopChunkQueue(), ExecParallelHashTupleAlloc(), ExecParallelHashTuplePrealloc(), ExpireAllKnownAssignedTransactionIds(), ExpireOldKnownAssignedTransactionIds(), ExpireTreeKnownAssignedTransactionIds(), ExtendCLOG(), ExtendCommitTs(), ExtendMultiXactMember(), ExtendMultiXactOffset(), ExtendSUBTRANS(), FastPathGetRelationLockEntry(), FastPathTransferRelationLocks(), FindAndDropRelFileNodeBuffers(), FinishPreparedTransaction(), FlushDatabaseBuffers(), FlushRelationBuffers(), FlushRelationsAllBuffers(), ForceTransactionIdLimitUpdate(), ForwardSyncRequest(), FreeWorkerInfo(), GetBackgroundWorkerPid(), GetBackgroundWorkerTypeByPid(), GetBlockerStatusData(), GetConflictingVirtualXIDs(), GetCurrentVirtualXIDs(), GetLastImportantRecPtr(), GetLastSegSwitchData(), GetLatestCommitTsData(), GetLockConflicts(), GetLockStatusData(), GetMultiXactIdMembers(), GetNewMultiXactId(), GetNewObjectId(), GetNewTransactionId(), GetOldestActiveTransactionId(), GetOldestMultiXactId(), GetOldestRestartPoint(), GetOldestSafeDecodingTransactionId(), GetOldSnapshotFromTimeMapping(), GetOldSnapshotTimeMapping(), GetPredicateLockStatusData(), GetPreparedTransactionList(), GetRunningTransactionData(), GetRunningTransactionLocks(), GetSafeSnapshot(), GetSafeSnapshotBlockingPids(), GetSerializableTransactionSnapshotInt(), GetSnapshotData(), GetVirtualXIDsDelayingChkpt(), HandleAutoVacLauncherInterrupts(), HaveVirtualXIDsDelayingChkpt(), InstallXLogFileSegment(), InvalidateBuffer(), InvalidateObsoleteReplicationSlots(), InvalidatePossiblyObsoleteSlot(), KnownAssignedXidsAdd(), KnownAssignedXidsReset(), load_relmap_file(), 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(), 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(), PostPrepare_Locks(), PostPrepare_MultiXact(), PostPrepare_Twophase(), PreCommit_CheckForSerializationFailure(), PreCommit_Notify(), predicatelock_twophase_recover(), PredicateLockPageSplit(), PredicateLockTwoPhaseFinish(), PrefetchSharedBuffer(), PrescanPreparedTransactions(), ProcArrayAdd(), ProcArrayApplyRecoveryInfo(), ProcArrayApplyXidAssignment(), ProcArrayClearTransaction(), ProcArrayEndTransaction(), ProcArrayGetReplicationSlotXmin(), ProcArrayGroupClearXid(), ProcArrayInstallImportedXmin(), ProcArrayInstallRestoredXmin(), ProcArrayRemove(), ProcArraySetReplicationSlotXmin(), process_syncing_tables_for_apply(), ProcKill(), ProcSleep(), ReadBuffer_common(), ReadMultiXactCounts(), ReadMultiXactIdRange(), ReadNextFullTransactionId(), ReadNextMultiXactId(), ReadRecord(), ReadReplicationSlot(), RecordNewMultiXact(), RecoverPreparedTransactions(), RegisterDynamicBackgroundWorker(), RegisterPredicateLockingXid(), RelationCacheInitFilePreInvalidate(), ReleaseOneSerializableXact(), ReleasePredicateLocks(), relmap_redo(), RemoveScratchTarget(), ReplicationOriginExitCleanup(), ReplicationSlotAcquire(), ReplicationSlotCleanup(), ReplicationSlotCreate(), ReplicationSlotDropPtr(), ReplicationSlotRelease(), ReplicationSlotsComputeLogicalRestartLSN(), ReplicationSlotsComputeRequiredLSN(), ReplicationSlotsComputeRequiredXmin(), ReplicationSlotsCountDBSlots(), ReplicationSlotsDropDBSlots(), replorigin_advance(), replorigin_drop_guts(), replorigin_get_progress(), replorigin_session_advance(), replorigin_session_get_progress(), replorigin_session_reset(), replorigin_session_setup(), resize(), RestoreScratchTarget(), restoreTwoPhaseData(), SaveSlotToPath(), SearchNamedReplicationSlot(), SerialAdd(), SerialGetMinConflictCommitSeqNo(), SerialSetActiveSerXmin(), set_indexsafe_procflags(), SetCommitTsLimit(), 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(), SyncOneBuffer(), SyncRepCancelWait(), SyncRepCleanupAtProcExit(), SyncRepReleaseWaiters(), SyncRepUpdateSyncStandbysDefined(), SyncRepWaitForLSN(), TablespaceCreateDbspace(), tbm_shared_iterate(), TerminateBackgroundWorker(), TerminateOtherDBBackends(), 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(), WaitForWALToBecomeAvailable(), 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 1427 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)
                    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, 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().

LWLockAttemptLock()

static bool LWLockAttemptLock ( LWLock *  lock, LWLockMode  mode  )

static

Definition at line 817 of file lwlock.c.

{
    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();
}

References AssertArg, 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 1370 of file lwlock.c.

{
    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");
        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 AssertArg, 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(), 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 1554 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 1104 of file lwlock.c.

{
    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 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)
                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(), 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().

LWLockHeldByMe()

bool LWLockHeldByMe

(

LWLock *

l

)

Definition at line 1919 of file lwlock.c.

{
    int         i;
 
    for (i = 0; i < num_held_lwlocks; i++)
    {
        if (held_lwlocks[i].lock == l)
            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_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(), TransactionIdInRecentPast(), TwoPhaseGetGXact(), and UnpinBuffer().

LWLockHeldByMeInMode()

bool LWLockHeldByMeInMode	(	LWLock *	l,
		LWLockMode	mode
	)

Definition at line 1937 of file lwlock.c.

{
    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;
}

References held_lwlocks, i, mode, and num_held_lwlocks.

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

LWLockInitialize()

void LWLockInitialize	(	LWLock *	lock,
		int	tranche_id
	)

Definition at line 736 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(), ReplicationOriginShmemInit(), ReplicationSlotsShmemInit(), SimpleLruInit(), sts_initialize(), tbm_prepare_shared_iterate(), and XLOGShmemInit().

LWLockNewTrancheId()

int LWLockNewTrancheId

(

void

)

Definition at line 625 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(), and InitializeLWLocks().

LWLockQueueSelf()

static void LWLockQueueSelf ( LWLock *  lock, LWLockMode  mode  )

static

Definition at line 1060 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)
        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
 
}

References elog, LW_FLAG_HAS_WAITERS, LW_WAIT_UNTIL_FREE, 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 649 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 = (const char **)
                repalloc(LWLockTrancheNames, newalloc * sizeof(char *));
            memset(LWLockTrancheNames + LWLockTrancheNamesAllocated,
                   0,
                   (newalloc - LWLockTrancheNamesAllocated) * sizeof(char *));
        }
        LWLockTrancheNamesAllocated = newalloc;
    }
 
    LWLockTrancheNames[tranche_id] = tranche_name;
}

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

Referenced by apw_init_shmem(), and CreateLWLocks().

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(), AtPrepare_PredicateLocks(), attach_internal(), autoprewarm_main(), autoprewarm_start_worker(), AutoVacLauncherMain(), AutoVacuumRequestWork(), AutoVacWorkerMain(), BackendIdGetProc(), BackendIdGetTransactionIds(), BackendPidGetProc(), BackendXidGetPid(), BecomeLockGroupLeader(), BecomeLockGroupMember(), BootStrapCLOG(), BootStrapMultiXact(), BootStrapSUBTRANS(), BootStrapXLOG(), BufferAlloc(), CancelDBBackends(), check_for_freed_segments(), CheckDeadLock(), CheckForSerializableConflictOut(), CheckPointPredicate(), CheckPointRelationMap(), CheckPointReplicationOrigin(), CheckPointReplicationSlots(), CheckPointTwoPhase(), CheckRecoveryConsistency(), CheckTableForSerializableConflictIn(), CheckTargetForConflictsIn(), choose_next_subplan_for_leader(), choose_next_subplan_for_worker(), CleanupInvalidationState(), ClearOldPredicateLocks(), clog_redo(), commit_ts_redo(), ComputeXidHorizons(), copy_replication_slot(), CountDBBackends(), CountDBConnections(), CountOtherDBBackends(), CountUserBackends(), CreateCheckPoint(), CreateEndOfRecoveryRecord(), CreateInitDecodingContext(), CreatePredicateLock(), CreateRestartPoint(), DeactivateCommitTs(), DeleteChildTargetLocks(), DeleteLockTarget(), destroy_superblock(), do_autovacuum(), do_pg_start_backup(), do_pg_stop_backup(), do_start_worker(), DropAllPredicateLocksFromTable(), DropSubscription(), DropTableSpace(), dsa_allocate_extended(), dsa_dump(), dsa_free(), dsa_pin(), dsa_release_in_place(), dsa_set_size_limit(), dsa_trim(), dsa_unpin(), dshash_delete_entry(), dshash_delete_key(), dshash_dump(), dshash_find(), dshash_find_or_insert(), dshash_release_lock(), dsm_attach(), dsm_create(), dsm_detach(), dsm_pin_segment(), dsm_unpin_segment(), ensure_active_superblock(), entry_reset(), Exec_ListenPreCommit(), ExecParallelHashMergeCounters(), ExecParallelHashPopChunkQueue(), ExecParallelHashTupleAlloc(), ExecParallelHashTuplePrealloc(), ExpireAllKnownAssignedTransactionIds(), ExpireOldKnownAssignedTransactionIds(), ExpireTreeKnownAssignedTransactionIds(), ExtendCLOG(), ExtendCommitTs(), ExtendMultiXactMember(), ExtendMultiXactOffset(), ExtendSUBTRANS(), FastPathGetRelationLockEntry(), FastPathTransferRelationLocks(), find_multixact_start(), FindAndDropRelFileNodeBuffers(), FinishPreparedTransaction(), FlushDatabaseBuffers(), FlushRelationBuffers(), FlushRelationsAllBuffers(), ForceTransactionIdLimitUpdate(), ForwardSyncRequest(), FreeWorkerInfo(), GetBackgroundWorkerPid(), GetBackgroundWorkerTypeByPid(), GetBlockerStatusData(), GetConflictingVirtualXIDs(), GetCurrentVirtualXIDs(), GetLastImportantRecPtr(), GetLastSegSwitchData(), GetLatestCommitTsData(), GetLockConflicts(), GetLockStatusData(), GetMultiXactIdMembers(), GetNewMultiXactId(), GetNewObjectId(), GetNewTransactionId(), GetOldestActiveTransactionId(), GetOldestMultiXactId(), GetOldestRestartPoint(), GetOldestSafeDecodingTransactionId(), GetOldSnapshotFromTimeMapping(), GetOldSnapshotTimeMapping(), GetPredicateLockStatusData(), GetPreparedTransactionList(), GetRunningTransactionLocks(), GetSafeSnapshot(), GetSafeSnapshotBlockingPids(), GetSerializableTransactionSnapshotInt(), GetSnapshotData(), GetVirtualXIDsDelayingChkpt(), HandleAutoVacLauncherInterrupts(), HaveVirtualXIDsDelayingChkpt(), InstallXLogFileSegment(), InvalidateBuffer(), InvalidateObsoleteReplicationSlots(), InvalidatePossiblyObsoleteSlot(), KnownAssignedXidsAdd(), KnownAssignedXidsReset(), load_relmap_file(), 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(), 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(), PostPrepare_Locks(), PostPrepare_MultiXact(), PostPrepare_Twophase(), PreCommit_CheckForSerializationFailure(), PreCommit_Notify(), predicatelock_twophase_recover(), PredicateLockPageSplit(), PredicateLockTwoPhaseFinish(), PrefetchSharedBuffer(), PrescanPreparedTransactions(), ProcArrayAdd(), ProcArrayApplyRecoveryInfo(), ProcArrayApplyXidAssignment(), ProcArrayClearTransaction(), ProcArrayEndTransaction(), ProcArrayGetReplicationSlotXmin(), ProcArrayGroupClearXid(), ProcArrayInstallImportedXmin(), ProcArrayInstallRestoredXmin(), ProcArrayRemove(), ProcArraySetReplicationSlotXmin(), process_syncing_tables_for_apply(), ProcKill(), ProcSleep(), ReadMultiXactCounts(), ReadMultiXactIdRange(), ReadNextFullTransactionId(), ReadNextMultiXactId(), ReadRecord(), ReadReplicationSlot(), RecordNewMultiXact(), RecoverPreparedTransactions(), RegisterDynamicBackgroundWorker(), RegisterPredicateLockingXid(), RelationCacheInitFilePostInvalidate(), ReleaseOneSerializableXact(), ReleasePredicateLocks(), relmap_redo(), RemoveScratchTarget(), ReplicationOriginExitCleanup(), ReplicationSlotAcquire(), ReplicationSlotCleanup(), ReplicationSlotCreate(), ReplicationSlotDropPtr(), ReplicationSlotRelease(), ReplicationSlotsComputeLogicalRestartLSN(), ReplicationSlotsComputeRequiredLSN(), ReplicationSlotsComputeRequiredXmin(), ReplicationSlotsCountDBSlots(), ReplicationSlotsDropDBSlots(), replorigin_advance(), replorigin_drop_guts(), replorigin_get_progress(), replorigin_session_advance(), replorigin_session_get_progress(), replorigin_session_reset(), replorigin_session_setup(), resize(), RestoreScratchTarget(), restoreTwoPhaseData(), SaveSlotToPath(), SearchNamedReplicationSlot(), SerialAdd(), SerialGetMinConflictCommitSeqNo(), SerialSetActiveSerXmin(), set_indexsafe_procflags(), SetCommitTsLimit(), 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(), SyncOneBuffer(), SyncRepCancelWait(), SyncRepCleanupAtProcExit(), SyncRepReleaseWaiters(), SyncRepUpdateSyncStandbysDefined(), SyncRepWaitForLSN(), TablespaceCreateDbspace(), tbm_shared_iterate(), TerminateBackgroundWorker(), TerminateOtherDBBackends(), 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(), WaitForWALToBecomeAvailable(), 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 763 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 754 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 433 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);
 
    /* Disallow adding any more named tranches. */
    lock_named_request_allowed = false;
 
    return size;
}

References add_size(), i, lock_named_request_allowed, 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 1749 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);
    }
 
    /* 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);
    }
}

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().

LWLockWaitForVar()

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

Definition at line 1614 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)
                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, 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 888 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 940 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 953 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;
        }
 
        /*
         * 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);
    }
}

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().

NumLWLocksForNamedTranches()

static int NumLWLocksForNamedTranches ( void  )

static

Definition at line 418 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 699 of file lwlock.c.

{
    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 = 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(), i, IsUnderPostmaster, lock_named_request_allowed, MemoryContextAlloc(), NAMEDATALEN, NamedLWLockTrancheRequestArray, NamedLWLockTrancheRequests, NamedLWLockTrancheRequestsAllocated, NamedLWLockTrancheRequest::num_lwlocks, pg_nextpower2_32(), repalloc(), strlcpy(), TopMemoryContext, and NamedLWLockTrancheRequest::tranche_name.

Referenced by _PG_init().

StaticAssertDecl()

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

Variable Documentation

BuiltinTrancheNames

const char* const BuiltinTrancheNames[]

static

Definition at line 131 of file lwlock.c.

Referenced by GetLWTrancheName().

held_lwlocks

LWLockHandle held_lwlocks[MAX_SIMUL_LWLOCKS]

static

Definition at line 217 of file lwlock.c.

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

IndividualLWLockNames

const char* const IndividualLWLockNames[]

extern

Referenced by GetLWTrancheName().

lock_named_request_allowed

bool lock_named_request_allowed = true

static

Definition at line 240 of file lwlock.c.

Referenced by LWLockShmemSize(), and RequestNamedLWLockTranche().

LWLockTrancheNames

const char** LWLockTrancheNames = NULL

static

Definition at line 191 of file lwlock.c.

Referenced by GetLWTrancheName(), and LWLockRegisterTranche().

LWLockTrancheNamesAllocated

int LWLockTrancheNamesAllocated = 0

static

Definition at line 192 of file lwlock.c.

Referenced by GetLWTrancheName(), and LWLockRegisterTranche().

MainLWLockArray

LWLockPadded* MainLWLockArray = NULL

Definition at line 199 of file lwlock.c.

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

NamedLWLockTrancheArray

NamedLWLockTranche* NamedLWLockTrancheArray = NULL

Definition at line 238 of file lwlock.c.

Referenced by CreateLWLocks(), and InitializeLWLocks().

NamedLWLockTrancheRequestArray

NamedLWLockTrancheRequest* NamedLWLockTrancheRequestArray = NULL

static

Definition at line 226 of file lwlock.c.

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

NamedLWLockTrancheRequests

int NamedLWLockTrancheRequests = 0

Definition at line 235 of file lwlock.c.

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

NamedLWLockTrancheRequestsAllocated

int NamedLWLockTrancheRequestsAllocated = 0

static

Definition at line 227 of file lwlock.c.

Referenced by RequestNamedLWLockTranche().

num_held_lwlocks

int num_held_lwlocks = 0

static

Definition at line 216 of file lwlock.c.

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