waiteventset.h File Reference

#include "utils/resowner.h"

Include dependency graph for waiteventset.h:

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Go to the source code of this file.

Data Structures
struct	WaitEvent

Macros
#define	WL_LATCH_SET   (1 << 0)
#define	WL_SOCKET_READABLE   (1 << 1)
#define	WL_SOCKET_WRITEABLE   (1 << 2)
#define	WL_TIMEOUT   (1 << 3) /* not for WaitEventSetWait() */
#define	WL_POSTMASTER_DEATH   (1 << 4)
#define	WL_EXIT_ON_PM_DEATH   (1 << 5)
#define	WL_SOCKET_CONNECTED   WL_SOCKET_WRITEABLE
#define	WL_SOCKET_CLOSED   (1 << 7)
#define	WL_SOCKET_ACCEPT   WL_SOCKET_READABLE
#define	WL_SOCKET_MASK

Typedefs
typedef struct WaitEvent	WaitEvent
typedef struct WaitEventSet	WaitEventSet

Functions
void	InitializeWaitEventSupport (void)
WaitEventSet *	CreateWaitEventSet (ResourceOwner resowner, int nevents)
void	FreeWaitEventSet (WaitEventSet *set)
void	FreeWaitEventSetAfterFork (WaitEventSet *set)
int	AddWaitEventToSet (WaitEventSet *set, uint32 events, pgsocket fd, struct Latch *latch, void *user_data)
void	ModifyWaitEvent (WaitEventSet *set, int pos, uint32 events, struct Latch *latch)
int	WaitEventSetWait (WaitEventSet *set, long timeout, WaitEvent *occurred_events, int nevents, uint32 wait_event_info)
int	GetNumRegisteredWaitEvents (WaitEventSet *set)
bool	WaitEventSetCanReportClosed (void)
void	WakeupMyProc (void)
void	WakeupOtherProc (int pid)

Macro Definition Documentation

WL_EXIT_ON_PM_DEATH

#define WL_EXIT_ON_PM_DEATH   (1 << 5)

Definition at line 39 of file waiteventset.h.

WL_LATCH_SET

#define WL_LATCH_SET   (1 << 0)

Definition at line 34 of file waiteventset.h.

WL_POSTMASTER_DEATH

#define WL_POSTMASTER_DEATH   (1 << 4)

Definition at line 38 of file waiteventset.h.

WL_SOCKET_ACCEPT

#define WL_SOCKET_ACCEPT   WL_SOCKET_READABLE

Definition at line 51 of file waiteventset.h.

WL_SOCKET_CLOSED

#define WL_SOCKET_CLOSED   (1 << 7)

Definition at line 46 of file waiteventset.h.

WL_SOCKET_CONNECTED

#define WL_SOCKET_CONNECTED   WL_SOCKET_WRITEABLE

Definition at line 44 of file waiteventset.h.

WL_SOCKET_MASK

#define WL_SOCKET_MASK

Value:

                             (WL_SOCKET_READABLE | \
                             WL_SOCKET_WRITEABLE | \
                             WL_SOCKET_CONNECTED | \
                             WL_SOCKET_ACCEPT | \
                             WL_SOCKET_CLOSED)

Definition at line 53 of file waiteventset.h.

WL_SOCKET_READABLE

#define WL_SOCKET_READABLE   (1 << 1)

Definition at line 35 of file waiteventset.h.

WL_SOCKET_WRITEABLE

#define WL_SOCKET_WRITEABLE   (1 << 2)

Definition at line 36 of file waiteventset.h.

WL_TIMEOUT

#define WL_TIMEOUT   (1 << 3) /* not for WaitEventSetWait() */

Definition at line 37 of file waiteventset.h.

Typedef Documentation

WaitEvent

typedef struct WaitEvent WaitEvent

WaitEventSet

typedef struct WaitEventSet WaitEventSet

Definition at line 71 of file waiteventset.h.

Function Documentation

AddWaitEventToSet()

int AddWaitEventToSet	(	WaitEventSet *	set,
		uint32	events,
		pgsocket	fd,
		struct Latch *	latch,
		void *	user_data
	)

Definition at line 569 of file waiteventset.c.

{
    WaitEvent  *event;
 
    /* not enough space */
    Assert(set->nevents < set->nevents_space);
 
    if (events == WL_EXIT_ON_PM_DEATH)
    {
        events = WL_POSTMASTER_DEATH;
        set->exit_on_postmaster_death = true;
    }
 
    if (latch)
    {
        if (latch->owner_pid != MyProcPid)
            elog(ERROR, "cannot wait on a latch owned by another process");
        if (set->latch)
            elog(ERROR, "cannot wait on more than one latch");
        if ((events & WL_LATCH_SET) != WL_LATCH_SET)
            elog(ERROR, "latch events only support being set");
    }
    else
    {
        if (events & WL_LATCH_SET)
            elog(ERROR, "cannot wait on latch without a specified latch");
    }
 
    /* waiting for socket readiness without a socket indicates a bug */
    if (fd == PGINVALID_SOCKET && (events & WL_SOCKET_MASK))
        elog(ERROR, "cannot wait on socket event without a socket");
 
    event = &set->events[set->nevents];
    event->pos = set->nevents++;
    event->fd = fd;
    event->events = events;
    event->user_data = user_data;
#ifdef WIN32
    event->reset = false;
#endif
 
    if (events == WL_LATCH_SET)
    {
        set->latch = latch;
        set->latch_pos = event->pos;
#if defined(WAIT_USE_SELF_PIPE)
        event->fd = selfpipe_readfd;
#elif defined(WAIT_USE_SIGNALFD)
        event->fd = signal_fd;
#else
        event->fd = PGINVALID_SOCKET;
#ifdef WAIT_USE_EPOLL
        return event->pos;
#endif
#endif
    }
    else if (events == WL_POSTMASTER_DEATH)
    {
#ifndef WIN32
        event->fd = postmaster_alive_fds[POSTMASTER_FD_WATCH];
#endif
    }
 
    /* perform wait primitive specific initialization, if needed */
#if defined(WAIT_USE_EPOLL)
    WaitEventAdjustEpoll(set, event, EPOLL_CTL_ADD);
#elif defined(WAIT_USE_KQUEUE)
    WaitEventAdjustKqueue(set, event, 0);
#elif defined(WAIT_USE_POLL)
    WaitEventAdjustPoll(set, event);
#elif defined(WAIT_USE_WIN32)
    WaitEventAdjustWin32(set, event);
#endif
 
    return event->pos;
}

References Assert(), elog, ERROR, WaitEventSet::events, WaitEventSet::exit_on_postmaster_death, fd(), WaitEventSet::latch, WaitEventSet::latch_pos, MyProcPid, WaitEventSet::nevents, WaitEventSet::nevents_space, Latch::owner_pid, PGINVALID_SOCKET, WaitEvent::pos, postmaster_alive_fds, POSTMASTER_FD_WATCH, selfpipe_readfd, WaitEventAdjustPoll(), WL_EXIT_ON_PM_DEATH, WL_LATCH_SET, WL_POSTMASTER_DEATH, and WL_SOCKET_MASK.

Referenced by ConfigurePostmasterWaitSet(), ExecAppendAsyncEventWait(), InitializeLatchWaitSet(), postgresForeignAsyncConfigureWait(), pq_init(), SysLoggerMain(), and WaitLatchOrSocket().

CreateWaitEventSet()

WaitEventSet * CreateWaitEventSet	(	ResourceOwner	resowner,
		int	nevents
	)

Definition at line 363 of file waiteventset.c.

{
    WaitEventSet *set;
    char       *data;
    Size        sz = 0;
 
    /*
     * Use MAXALIGN size/alignment to guarantee that later uses of memory are
     * aligned correctly. E.g. epoll_event might need 8 byte alignment on some
     * platforms, but earlier allocations like WaitEventSet and WaitEvent
     * might not be sized to guarantee that when purely using sizeof().
     */
    sz += MAXALIGN(sizeof(WaitEventSet));
    sz += MAXALIGN(sizeof(WaitEvent) * nevents);
 
#if defined(WAIT_USE_EPOLL)
    sz += MAXALIGN(sizeof(struct epoll_event) * nevents);
#elif defined(WAIT_USE_KQUEUE)
    sz += MAXALIGN(sizeof(struct kevent) * nevents);
#elif defined(WAIT_USE_POLL)
    sz += MAXALIGN(sizeof(struct pollfd) * nevents);
#elif defined(WAIT_USE_WIN32)
    /* need space for the pgwin32_signal_event */
    sz += MAXALIGN(sizeof(HANDLE) * (nevents + 1));
#endif
 
    if (resowner != NULL)
        ResourceOwnerEnlarge(resowner);
 
    data = (char *) MemoryContextAllocZero(TopMemoryContext, sz);
 
    set = (WaitEventSet *) data;
    data += MAXALIGN(sizeof(WaitEventSet));
 
    set->events = (WaitEvent *) data;
    data += MAXALIGN(sizeof(WaitEvent) * nevents);
 
#if defined(WAIT_USE_EPOLL)
    set->epoll_ret_events = (struct epoll_event *) data;
    data += MAXALIGN(sizeof(struct epoll_event) * nevents);
#elif defined(WAIT_USE_KQUEUE)
    set->kqueue_ret_events = (struct kevent *) data;
    data += MAXALIGN(sizeof(struct kevent) * nevents);
#elif defined(WAIT_USE_POLL)
    set->pollfds = (struct pollfd *) data;
    data += MAXALIGN(sizeof(struct pollfd) * nevents);
#elif defined(WAIT_USE_WIN32)
    set->handles = (HANDLE) data;
    data += MAXALIGN(sizeof(HANDLE) * nevents);
#endif
 
    set->latch = NULL;
    set->nevents_space = nevents;
    set->exit_on_postmaster_death = false;
 
    if (resowner != NULL)
    {
        ResourceOwnerRememberWaitEventSet(resowner, set);
        set->owner = resowner;
    }
 
#if defined(WAIT_USE_EPOLL)
    if (!AcquireExternalFD())
        elog(ERROR, "AcquireExternalFD, for epoll_create1, failed: %m");
    set->epoll_fd = epoll_create1(EPOLL_CLOEXEC);
    if (set->epoll_fd < 0)
    {
        ReleaseExternalFD();
        elog(ERROR, "epoll_create1 failed: %m");
    }
#elif defined(WAIT_USE_KQUEUE)
    if (!AcquireExternalFD())
        elog(ERROR, "AcquireExternalFD, for kqueue, failed: %m");
    set->kqueue_fd = kqueue();
    if (set->kqueue_fd < 0)
    {
        ReleaseExternalFD();
        elog(ERROR, "kqueue failed: %m");
    }
    if (fcntl(set->kqueue_fd, F_SETFD, FD_CLOEXEC) == -1)
    {
        int         save_errno = errno;
 
        close(set->kqueue_fd);
        ReleaseExternalFD();
        errno = save_errno;
        elog(ERROR, "fcntl(F_SETFD) failed on kqueue descriptor: %m");
    }
    set->report_postmaster_not_running = false;
#elif defined(WAIT_USE_WIN32)
 
    /*
     * To handle signals while waiting, we need to add a win32 specific event.
     * We accounted for the additional event at the top of this routine. See
     * port/win32/signal.c for more details.
     *
     * Note: pgwin32_signal_event should be first to ensure that it will be
     * reported when multiple events are set.  We want to guarantee that
     * pending signals are serviced.
     */
    set->handles[0] = pgwin32_signal_event;
    StaticAssertStmt(WSA_INVALID_EVENT == NULL, "");
#endif
 
    return set;
}

References AcquireExternalFD(), close, data, elog, ERROR, WaitEventSet::events, WaitEventSet::exit_on_postmaster_death, WaitEventSet::latch, MAXALIGN, MemoryContextAllocZero(), WaitEventSet::nevents_space, WaitEventSet::owner, pgwin32_signal_event, WaitEventSet::pollfds, ReleaseExternalFD(), ResourceOwnerEnlarge(), ResourceOwnerRememberWaitEventSet(), StaticAssertStmt, and TopMemoryContext.

Referenced by ConfigurePostmasterWaitSet(), ExecAppendAsyncEventWait(), InitializeLatchWaitSet(), pq_init(), SysLoggerMain(), and WaitLatchOrSocket().

FreeWaitEventSet()

void FreeWaitEventSet

(

WaitEventSet *

set

)

Definition at line 480 of file waiteventset.c.

{
    if (set->owner)
    {
        ResourceOwnerForgetWaitEventSet(set->owner, set);
        set->owner = NULL;
    }
 
#if defined(WAIT_USE_EPOLL)
    close(set->epoll_fd);
    ReleaseExternalFD();
#elif defined(WAIT_USE_KQUEUE)
    close(set->kqueue_fd);
    ReleaseExternalFD();
#elif defined(WAIT_USE_WIN32)
    for (WaitEvent *cur_event = set->events;
         cur_event < (set->events + set->nevents);
         cur_event++)
    {
        if (cur_event->events & WL_LATCH_SET)
        {
            /* uses the latch's HANDLE */
        }
        else if (cur_event->events & WL_POSTMASTER_DEATH)
        {
            /* uses PostmasterHandle */
        }
        else
        {
            /* Clean up the event object we created for the socket */
            WSAEventSelect(cur_event->fd, NULL, 0);
            WSACloseEvent(set->handles[cur_event->pos + 1]);
        }
    }
#endif
 
    pfree(set);
}

References close, WaitEventSet::events, WaitEventSet::nevents, WaitEventSet::owner, pfree(), ReleaseExternalFD(), ResourceOwnerForgetWaitEventSet(), WL_LATCH_SET, and WL_POSTMASTER_DEATH.

Referenced by ConfigurePostmasterWaitSet(), ExecAppendAsyncEventWait(), ResOwnerReleaseWaitEventSet(), and WaitLatchOrSocket().

FreeWaitEventSetAfterFork()

void FreeWaitEventSetAfterFork

(

WaitEventSet *

set

)

Definition at line 523 of file waiteventset.c.

{
#if defined(WAIT_USE_EPOLL)
    close(set->epoll_fd);
    ReleaseExternalFD();
#elif defined(WAIT_USE_KQUEUE)
    /* kqueues are not normally inherited by child processes */
    ReleaseExternalFD();
#endif
 
    pfree(set);
}

References close, pfree(), and ReleaseExternalFD().

Referenced by ClosePostmasterPorts().

GetNumRegisteredWaitEvents()

int GetNumRegisteredWaitEvents

(

WaitEventSet *

set

)

Definition at line 1882 of file waiteventset.c.

{
    return set->nevents;
}

References WaitEventSet::nevents.

Referenced by ExecAppendAsyncEventWait(), and postgresForeignAsyncConfigureWait().

InitializeWaitEventSupport()

void InitializeWaitEventSupport

(

void

)

Definition at line 240 of file waiteventset.c.

{
#if defined(WAIT_USE_SELF_PIPE)
    int         pipefd[2];
 
    if (IsUnderPostmaster)
    {
        /*
         * We might have inherited connections to a self-pipe created by the
         * postmaster.  It's critical that child processes create their own
         * self-pipes, of course, and we really want them to close the
         * inherited FDs for safety's sake.
         */
        if (selfpipe_owner_pid != 0)
        {
            /* Assert we go through here but once in a child process */
            Assert(selfpipe_owner_pid != MyProcPid);
            /* Release postmaster's pipe FDs; ignore any error */
            (void) close(selfpipe_readfd);
            (void) close(selfpipe_writefd);
            /* Clean up, just for safety's sake; we'll set these below */
            selfpipe_readfd = selfpipe_writefd = -1;
            selfpipe_owner_pid = 0;
            /* Keep fd.c's accounting straight */
            ReleaseExternalFD();
            ReleaseExternalFD();
        }
        else
        {
            /*
             * Postmaster didn't create a self-pipe ... or else we're in an
             * EXEC_BACKEND build, in which case it doesn't matter since the
             * postmaster's pipe FDs were closed by the action of FD_CLOEXEC.
             * fd.c won't have state to clean up, either.
             */
            Assert(selfpipe_readfd == -1);
        }
    }
    else
    {
        /* In postmaster or standalone backend, assert we do this but once */
        Assert(selfpipe_readfd == -1);
        Assert(selfpipe_owner_pid == 0);
    }
 
    /*
     * Set up the self-pipe that allows a signal handler to wake up the
     * poll()/epoll_wait() in WaitLatch. Make the write-end non-blocking, so
     * that SetLatch won't block if the event has already been set many times
     * filling the kernel buffer. Make the read-end non-blocking too, so that
     * we can easily clear the pipe by reading until EAGAIN or EWOULDBLOCK.
     * Also, make both FDs close-on-exec, since we surely do not want any
     * child processes messing with them.
     */
    if (pipe(pipefd) < 0)
        elog(FATAL, "pipe() failed: %m");
    if (fcntl(pipefd[0], F_SETFL, O_NONBLOCK) == -1)
        elog(FATAL, "fcntl(F_SETFL) failed on read-end of self-pipe: %m");
    if (fcntl(pipefd[1], F_SETFL, O_NONBLOCK) == -1)
        elog(FATAL, "fcntl(F_SETFL) failed on write-end of self-pipe: %m");
    if (fcntl(pipefd[0], F_SETFD, FD_CLOEXEC) == -1)
        elog(FATAL, "fcntl(F_SETFD) failed on read-end of self-pipe: %m");
    if (fcntl(pipefd[1], F_SETFD, FD_CLOEXEC) == -1)
        elog(FATAL, "fcntl(F_SETFD) failed on write-end of self-pipe: %m");
 
    selfpipe_readfd = pipefd[0];
    selfpipe_writefd = pipefd[1];
    selfpipe_owner_pid = MyProcPid;
 
    /* Tell fd.c about these two long-lived FDs */
    ReserveExternalFD();
    ReserveExternalFD();
 
    pqsignal(SIGURG, latch_sigurg_handler);
#endif
 
#ifdef WAIT_USE_SIGNALFD
    sigset_t    signalfd_mask;
 
    if (IsUnderPostmaster)
    {
        /*
         * It would probably be safe to re-use the inherited signalfd since
         * signalfds only see the current process's pending signals, but it
         * seems less surprising to close it and create our own.
         */
        if (signal_fd != -1)
        {
            /* Release postmaster's signal FD; ignore any error */
            (void) close(signal_fd);
            signal_fd = -1;
            ReleaseExternalFD();
        }
    }
 
    /* Block SIGURG, because we'll receive it through a signalfd. */
    sigaddset(&UnBlockSig, SIGURG);
 
    /* Set up the signalfd to receive SIGURG notifications. */
    sigemptyset(&signalfd_mask);
    sigaddset(&signalfd_mask, SIGURG);
    signal_fd = signalfd(-1, &signalfd_mask, SFD_NONBLOCK | SFD_CLOEXEC);
    if (signal_fd < 0)
        elog(FATAL, "signalfd() failed");
    ReserveExternalFD();
#endif
 
#ifdef WAIT_USE_KQUEUE
    /* Ignore SIGURG, because we'll receive it via kqueue. */
    pqsignal(SIGURG, SIG_IGN);
#endif
}

References Assert(), close, elog, FATAL, IsUnderPostmaster, latch_sigurg_handler(), MyProcPid, pqsignal, ReleaseExternalFD(), ReserveExternalFD(), selfpipe_owner_pid, selfpipe_readfd, selfpipe_writefd, and UnBlockSig.

Referenced by InitPostmasterChild(), InitStandaloneProcess(), and PostmasterMain().

ModifyWaitEvent()

void ModifyWaitEvent	(	WaitEventSet *	set,
		int	pos,
		uint32	events,
		struct Latch *	latch
	)

Definition at line 655 of file waiteventset.c.

{
    WaitEvent  *event;
#if defined(WAIT_USE_KQUEUE)
    int         old_events;
#endif
 
    Assert(pos < set->nevents);
 
    event = &set->events[pos];
#if defined(WAIT_USE_KQUEUE)
    old_events = event->events;
#endif
 
    /*
     * Allow switching between WL_POSTMASTER_DEATH and WL_EXIT_ON_PM_DEATH.
     *
     * Note that because WL_EXIT_ON_PM_DEATH is mapped to WL_POSTMASTER_DEATH
     * in AddWaitEventToSet(), this needs to be checked before the fast-path
     * below that checks if 'events' has changed.
     */
    if (event->events == WL_POSTMASTER_DEATH)
    {
        if (events != WL_POSTMASTER_DEATH && events != WL_EXIT_ON_PM_DEATH)
            elog(ERROR, "cannot remove postmaster death event");
        set->exit_on_postmaster_death = ((events & WL_EXIT_ON_PM_DEATH) != 0);
        return;
    }
 
    /*
     * If neither the event mask nor the associated latch changes, return
     * early. That's an important optimization for some sockets, where
     * ModifyWaitEvent is frequently used to switch from waiting for reads to
     * waiting on writes.
     */
    if (events == event->events &&
        (!(event->events & WL_LATCH_SET) || set->latch == latch))
        return;
 
    if (event->events & WL_LATCH_SET && events != event->events)
        elog(ERROR, "cannot modify latch event");
 
    /* FIXME: validate event mask */
    event->events = events;
 
    if (events == WL_LATCH_SET)
    {
        if (latch && latch->owner_pid != MyProcPid)
            elog(ERROR, "cannot wait on a latch owned by another process");
        set->latch = latch;
 
        /*
         * On Unix, we don't need to modify the kernel object because the
         * underlying pipe (if there is one) is the same for all latches so we
         * can return immediately.  On Windows, we need to update our array of
         * handles, but we leave the old one in place and tolerate spurious
         * wakeups if the latch is disabled.
         */
#if defined(WAIT_USE_WIN32)
        if (!latch)
            return;
#else
        return;
#endif
    }
 
#if defined(WAIT_USE_EPOLL)
    WaitEventAdjustEpoll(set, event, EPOLL_CTL_MOD);
#elif defined(WAIT_USE_KQUEUE)
    WaitEventAdjustKqueue(set, event, old_events);
#elif defined(WAIT_USE_POLL)
    WaitEventAdjustPoll(set, event);
#elif defined(WAIT_USE_WIN32)
    WaitEventAdjustWin32(set, event);
#endif
}

References Assert(), elog, ERROR, WaitEventSet::events, WaitEvent::events, WaitEventSet::exit_on_postmaster_death, WaitEventSet::latch, MyProcPid, Latch::owner_pid, WaitEventAdjustPoll(), WL_EXIT_ON_PM_DEATH, WL_LATCH_SET, and WL_POSTMASTER_DEATH.

Referenced by pq_check_connection(), secure_read(), secure_write(), SwitchBackToLocalLatch(), SwitchToSharedLatch(), WaitLatch(), and WalSndWait().

WaitEventSetCanReportClosed()

bool WaitEventSetCanReportClosed

(

void

)

Definition at line 1867 of file waiteventset.c.

{
#if (defined(WAIT_USE_POLL) && defined(POLLRDHUP)) || \
    defined(WAIT_USE_EPOLL) || \
    defined(WAIT_USE_KQUEUE)
    return true;
#else
    return false;
#endif
}

Referenced by check_client_connection_check_interval().

WaitEventSetWait()

int WaitEventSetWait	(	WaitEventSet *	set,
		long	timeout,
		WaitEvent *	occurred_events,
		int	nevents,
		uint32	wait_event_info
	)

Definition at line 1037 of file waiteventset.c.

{
    int         returned_events = 0;
    instr_time  start_time;
    instr_time  cur_time;
    long        cur_timeout = -1;
 
    Assert(nevents > 0);
 
    /*
     * Initialize timeout if requested.  We must record the current time so
     * that we can determine the remaining timeout if interrupted.
     */
    if (timeout >= 0)
    {
        INSTR_TIME_SET_CURRENT(start_time);
        Assert(timeout >= 0 && timeout <= INT_MAX);
        cur_timeout = timeout;
    }
    else
        INSTR_TIME_SET_ZERO(start_time);
 
    pgstat_report_wait_start(wait_event_info);
 
#ifndef WIN32
    waiting = true;
#else
    /* Ensure that signals are serviced even if latch is already set */
    pgwin32_dispatch_queued_signals();
#endif
    while (returned_events == 0)
    {
        int         rc;
 
        /*
         * Check if the latch is set already first.  If so, we either exit
         * immediately or ask the kernel for further events available right
         * now without waiting, depending on how many events the caller wants.
         *
         * If someone sets the latch between this and the
         * WaitEventSetWaitBlock() below, the setter will write a byte to the
         * pipe (or signal us and the signal handler will do that), and the
         * readiness routine will return immediately.
         *
         * On unix, If there's a pending byte in the self pipe, we'll notice
         * whenever blocking. Only clearing the pipe in that case avoids
         * having to drain it every time WaitLatchOrSocket() is used. Should
         * the pipe-buffer fill up we're still ok, because the pipe is in
         * nonblocking mode. It's unlikely for that to happen, because the
         * self pipe isn't filled unless we're blocking (waiting = true), or
         * from inside a signal handler in latch_sigurg_handler().
         *
         * On windows, we'll also notice if there's a pending event for the
         * latch when blocking, but there's no danger of anything filling up,
         * as "Setting an event that is already set has no effect.".
         *
         * Note: we assume that the kernel calls involved in latch management
         * will provide adequate synchronization on machines with weak memory
         * ordering, so that we cannot miss seeing is_set if a notification
         * has already been queued.
         */
        if (set->latch && !set->latch->is_set)
        {
            /* about to sleep on a latch */
            set->latch->maybe_sleeping = true;
            pg_memory_barrier();
            /* and recheck */
        }
 
        if (set->latch && set->latch->is_set)
        {
            occurred_events->fd = PGINVALID_SOCKET;
            occurred_events->pos = set->latch_pos;
            occurred_events->user_data =
                set->events[set->latch_pos].user_data;
            occurred_events->events = WL_LATCH_SET;
            occurred_events++;
            returned_events++;
 
            /* could have been set above */
            set->latch->maybe_sleeping = false;
 
            if (returned_events == nevents)
                break;          /* output buffer full already */
 
            /*
             * Even though we already have an event, we'll poll just once with
             * zero timeout to see what non-latch events we can fit into the
             * output buffer at the same time.
             */
            cur_timeout = 0;
            timeout = 0;
        }
 
        /*
         * Wait for events using the readiness primitive chosen at the top of
         * this file. If -1 is returned, a timeout has occurred, if 0 we have
         * to retry, everything >= 1 is the number of returned events.
         */
        rc = WaitEventSetWaitBlock(set, cur_timeout,
                                   occurred_events, nevents - returned_events);
 
        if (set->latch &&
            set->latch->maybe_sleeping)
            set->latch->maybe_sleeping = false;
 
        if (rc == -1)
            break;              /* timeout occurred */
        else
            returned_events += rc;
 
        /* If we're not done, update cur_timeout for next iteration */
        if (returned_events == 0 && timeout >= 0)
        {
            INSTR_TIME_SET_CURRENT(cur_time);
            INSTR_TIME_SUBTRACT(cur_time, start_time);
            cur_timeout = timeout - (long) INSTR_TIME_GET_MILLISEC(cur_time);
            if (cur_timeout <= 0)
                break;
        }
    }
#ifndef WIN32
    waiting = false;
#endif
 
    pgstat_report_wait_end();
 
    return returned_events;
}

References Assert(), WaitEventSet::events, WaitEvent::events, WaitEvent::fd, INSTR_TIME_GET_MILLISEC, INSTR_TIME_SET_CURRENT, INSTR_TIME_SET_ZERO, INSTR_TIME_SUBTRACT, Latch::is_set, WaitEventSet::latch, WaitEventSet::latch_pos, Latch::maybe_sleeping, pg_memory_barrier, PGINVALID_SOCKET, pgstat_report_wait_end(), pgstat_report_wait_start(), pgwin32_dispatch_queued_signals(), WaitEvent::pos, start_time, WaitEvent::user_data, WaitEventSetWaitBlock(), waiting, and WL_LATCH_SET.

Referenced by ExecAppendAsyncEventWait(), pq_check_connection(), secure_read(), secure_write(), ServerLoop(), SysLoggerMain(), WaitLatch(), WaitLatchOrSocket(), and WalSndWait().

WakeupMyProc()

void WakeupMyProc

(

void

)

Definition at line 2019 of file waiteventset.c.

{
#if defined(WAIT_USE_SELF_PIPE)
    if (waiting)
        sendSelfPipeByte();
#else
    if (waiting)
        kill(MyProcPid, SIGURG);
#endif
}

References kill, MyProcPid, sendSelfPipeByte(), and waiting.

Referenced by SetLatch().

WakeupOtherProc()

void WakeupOtherProc

(

int

pid

)

Definition at line 2032 of file waiteventset.c.

{
    kill(pid, SIGURG);
}

References kill.

Referenced by SetLatch().