pg_sema.h File Reference

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Typedefs
typedef PGSemaphoreData *	PGSemaphore
Functions
void	PGReserveSemaphores (int maxSemas, int port)
void	PGSemaphoreCreate (PGSemaphore sema)
void	PGSemaphoreReset (PGSemaphore sema)
void	PGSemaphoreLock (PGSemaphore sema, bool interruptOK)
void	PGSemaphoreUnlock (PGSemaphore sema)
bool	PGSemaphoreTryLock (PGSemaphore sema)

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Typedef Documentation

typedef PGSemaphoreData* PGSemaphore

Definition at line 62 of file pg_sema.h.

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Function Documentation

void PGReserveSemaphores	(	int	maxSemas,
		int	port
	)

Definition at line 154 of file posix_sema.c.

References elog, malloc, maxSemaSets, maxSems, mySemaSets, mySemPointers, mySemSet, nextSemaKey, nextSemaNumber, nextSemKey, NULL, numSemaSets, numSems, on_shmem_exit(), PANIC, ReleaseSemaphores(), and SEMAS_PER_SET.

Referenced by CreateSharedMemoryAndSemaphores(), and main().

{
    mySemPointers = (sem_t **) malloc(maxSemas * sizeof(sem_t *));
    if (mySemPointers == NULL)
        elog(PANIC, "out of memory");
    numSems = 0;
    maxSems = maxSemas;
    nextSemKey = port * 1000;

    on_shmem_exit(ReleaseSemaphores, 0);
}

void PGSemaphoreCreate

(

PGSemaphore

sema

)

Definition at line 187 of file posix_sema.c.

References Assert, elog, ereport, errmsg(), IpcSemaphoreCreate(), IpcSemaphoreInitialize(), IsUnderPostmaster, maxSemaSets, maxSems, mySemaSets, mySemPointers, mySemSet, nextSemaNumber, NULL, numSemaSets, numSems, PANIC, PosixSemaphoreCreate(), and SEMAS_PER_SET.

Referenced by InitProcGlobal(), main(), and s_init_lock_sema().

{
    sem_t      *newsem;

    /* Can't do this in a backend, because static state is postmaster's */
    Assert(!IsUnderPostmaster);

    if (numSems >= maxSems)
        elog(PANIC, "too many semaphores created");

#ifdef USE_NAMED_POSIX_SEMAPHORES
    *sema = newsem = PosixSemaphoreCreate();
#else
    PosixSemaphoreCreate(sema);
    newsem = sema;
#endif

    /* Remember new sema for ReleaseSemaphores */
    mySemPointers[numSems++] = newsem;
}

void PGSemaphoreLock	(	PGSemaphore	sema,
		bool	interruptOK
	)

Definition at line 239 of file posix_sema.c.

References CHECK_FOR_INTERRUPTS, EINTR, elog, ereport, errmsg(), FALSE, FATAL, ImmediateInterruptOK, PG_SEM_REF, pgwin32_dispatch_queued_signals(), pgwin32_signal_event, and TRUE.

Referenced by LWLockAcquire(), LWLockAcquireOrWait(), main(), ProcSleep(), and ProcWaitForSignal().

{
    int         errStatus;

    /*
     * See notes in sysv_sema.c's implementation of PGSemaphoreLock. Just as
     * that code does for semop(), we handle both the case where sem_wait()
     * returns errno == EINTR after a signal, and the case where it just keeps
     * waiting.
     */
    do
    {
        ImmediateInterruptOK = interruptOK;
        CHECK_FOR_INTERRUPTS();
        errStatus = sem_wait(PG_SEM_REF(sema));
        ImmediateInterruptOK = false;
    } while (errStatus < 0 && errno == EINTR);

    if (errStatus < 0)
        elog(FATAL, "sem_wait failed: %m");
}

void PGSemaphoreReset

(

PGSemaphore

sema

)

Definition at line 214 of file posix_sema.c.

References EAGAIN, EINTR, elog, FATAL, IpcSemaphoreInitialize(), PG_SEM_REF, and PGSemaphoreTryLock().

Referenced by InitAuxiliaryProcess(), InitProcess(), and main().

{
    /*
     * There's no direct API for this in POSIX, so we have to ratchet the
     * semaphore down to 0 with repeated trywait's.
     */
    for (;;)
    {
        if (sem_trywait(PG_SEM_REF(sema)) < 0)
        {
            if (errno == EAGAIN || errno == EDEADLK)
                break;          /* got it down to 0 */
            if (errno == EINTR)
                continue;       /* can this happen? */
            elog(FATAL, "sem_trywait failed: %m");
        }
    }
}

bool PGSemaphoreTryLock

(

PGSemaphore

sema

)

Definition at line 292 of file posix_sema.c.

References EAGAIN, EINTR, elog, ereport, errmsg(), EWOULDBLOCK, FATAL, and PG_SEM_REF.

Referenced by main(), PGSemaphoreReset(), and tas_sema().

{
    int         errStatus;

    /*
     * Note: if errStatus is -1 and errno == EINTR then it means we returned
     * from the operation prematurely because we were sent a signal.  So we
     * try and lock the semaphore again.
     */
    do
    {
        errStatus = sem_trywait(PG_SEM_REF(sema));
    } while (errStatus < 0 && errno == EINTR);

    if (errStatus < 0)
    {
        if (errno == EAGAIN || errno == EDEADLK)
            return false;       /* failed to lock it */
        /* Otherwise we got trouble */
        elog(FATAL, "sem_trywait failed: %m");
    }

    return true;
}

void PGSemaphoreUnlock

(

PGSemaphore

sema

)

Definition at line 267 of file posix_sema.c.

References EINTR, elog, ereport, errmsg(), FATAL, NULL, and PG_SEM_REF.

Referenced by CheckDeadLock(), IpcSemaphoreCreate(), LWLockAcquire(), LWLockAcquireOrWait(), LWLockRelease(), main(), ProcSendSignal(), ProcWakeup(), and s_unlock_sema().

{
    int         errStatus;

    /*
     * Note: if errStatus is -1 and errno == EINTR then it means we returned
     * from the operation prematurely because we were sent a signal.  So we
     * try and unlock the semaphore again. Not clear this can really happen,
     * but might as well cope.
     */
    do
    {
        errStatus = sem_post(PG_SEM_REF(sema));
    } while (errStatus < 0 && errno == EINTR);

    if (errStatus < 0)
        elog(FATAL, "sem_post failed: %m");
}