{
sigemptyset(&UnBlockSig);
- /* Note: InitializeLatchSupport() modifies UnBlockSig. */
+ /* Note: InitializeWaitEventSupport() modifies UnBlockSig. */
/* First set all signals, then clear some. */
sigfillset(&BlockSig);
pqsignal(SIGCHLD, handle_pm_child_exit_signal);
/* This may configure SIGURG, depending on platform. */
- InitializeLatchSupport();
+ InitializeWaitEventSupport();
InitProcessLocalLatch();
/*
signalfuncs.o \
sinval.o \
sinvaladt.o \
- standby.o
+ standby.o \
+ waiteventset.o
include $(top_srcdir)/src/backend/common.mk
* latch.c
* Routines for inter-process latches
*
- * The poll() implementation uses the so-called self-pipe trick to overcome the
- * race condition involved with poll() and setting a global flag in the signal
- * handler. When a latch is set and the current process is waiting for it, the
- * signal handler wakes up the poll() in WaitLatch by writing a byte to a pipe.
- * A signal by itself doesn't interrupt poll() on all platforms, and even on
- * platforms where it does, a signal that arrives just before the poll() call
- * does not prevent poll() from entering sleep. An incoming byte on a pipe
- * however reliably interrupts the sleep, and causes poll() to return
- * immediately even if the signal arrives before poll() begins.
- *
- * The epoll() implementation overcomes the race with a different technique: it
- * keeps SIGURG blocked and consumes from a signalfd() descriptor instead. We
- * don't need to register a signal handler or create our own self-pipe. We
- * assume that any system that has Linux epoll() also has Linux signalfd().
- *
- * The kqueue() implementation waits for SIGURG with EVFILT_SIGNAL.
- *
- * The Windows implementation uses Windows events that are inherited by all
- * postmaster child processes. There's no need for the self-pipe trick there.
+ * The latch interface is a reliable replacement for the common pattern of
+ * using pg_usleep() or select() to wait until a signal arrives, where the
+ * signal handler sets a flag variable. See latch.h for more information
+ * on how to use them.
*
* Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*/
#include "postgres.h"
-#include <fcntl.h>
-#include <limits.h>
-#include <signal.h>
-#include <unistd.h>
-#ifdef HAVE_SYS_EPOLL_H
-#include <sys/epoll.h>
-#endif
-#ifdef HAVE_SYS_EVENT_H
-#include <sys/event.h>
-#endif
-#ifdef HAVE_SYS_SIGNALFD_H
-#include <sys/signalfd.h>
-#endif
-#ifdef HAVE_POLL_H
-#include <poll.h>
-#endif
-
-#include "libpq/pqsignal.h"
#include "miscadmin.h"
-#include "pgstat.h"
#include "port/atomics.h"
-#include "portability/instr_time.h"
-#include "postmaster/postmaster.h"
-#include "storage/fd.h"
-#include "storage/ipc.h"
#include "storage/latch.h"
-#include "storage/pmsignal.h"
-#include "utils/memutils.h"
+#include "storage/waiteventset.h"
#include "utils/resowner.h"
-/*
- * Select the fd readiness primitive to use. Normally the "most modern"
- * primitive supported by the OS will be used, but for testing it can be
- * useful to manually specify the used primitive. If desired, just add a
- * define somewhere before this block.
- */
-#if defined(WAIT_USE_EPOLL) || defined(WAIT_USE_POLL) || \
- defined(WAIT_USE_KQUEUE) || defined(WAIT_USE_WIN32)
-/* don't overwrite manual choice */
-#elif defined(HAVE_SYS_EPOLL_H)
-#define WAIT_USE_EPOLL
-#elif defined(HAVE_KQUEUE)
-#define WAIT_USE_KQUEUE
-#elif defined(HAVE_POLL)
-#define WAIT_USE_POLL
-#elif WIN32
-#define WAIT_USE_WIN32
-#else
-#error "no wait set implementation available"
-#endif
-
-/*
- * By default, we use a self-pipe with poll() and a signalfd with epoll(), if
- * available. For testing the choice can also be manually specified.
- */
-#if defined(WAIT_USE_POLL) || defined(WAIT_USE_EPOLL)
-#if defined(WAIT_USE_SELF_PIPE) || defined(WAIT_USE_SIGNALFD)
-/* don't overwrite manual choice */
-#elif defined(WAIT_USE_EPOLL) && defined(HAVE_SYS_SIGNALFD_H)
-#define WAIT_USE_SIGNALFD
-#else
-#define WAIT_USE_SELF_PIPE
-#endif
-#endif
-
-/* typedef in latch.h */
-struct WaitEventSet
-{
- ResourceOwner owner;
-
- int nevents; /* number of registered events */
- int nevents_space; /* maximum number of events in this set */
-
- /*
- * Array, of nevents_space length, storing the definition of events this
- * set is waiting for.
- */
- WaitEvent *events;
-
- /*
- * If WL_LATCH_SET is specified in any wait event, latch is a pointer to
- * said latch, and latch_pos the offset in the ->events array. This is
- * useful because we check the state of the latch before performing doing
- * syscalls related to waiting.
- */
- Latch *latch;
- int latch_pos;
-
- /*
- * WL_EXIT_ON_PM_DEATH is converted to WL_POSTMASTER_DEATH, but this flag
- * is set so that we'll exit immediately if postmaster death is detected,
- * instead of returning.
- */
- bool exit_on_postmaster_death;
-
-#if defined(WAIT_USE_EPOLL)
- int epoll_fd;
- /* epoll_wait returns events in a user provided arrays, allocate once */
- struct epoll_event *epoll_ret_events;
-#elif defined(WAIT_USE_KQUEUE)
- int kqueue_fd;
- /* kevent returns events in a user provided arrays, allocate once */
- struct kevent *kqueue_ret_events;
- bool report_postmaster_not_running;
-#elif defined(WAIT_USE_POLL)
- /* poll expects events to be waited on every poll() call, prepare once */
- struct pollfd *pollfds;
-#elif defined(WAIT_USE_WIN32)
-
- /*
- * Array of windows events. The first element always contains
- * pgwin32_signal_event, so the remaining elements are offset by one (i.e.
- * event->pos + 1).
- */
- HANDLE *handles;
-#endif
-};
-
/* A common WaitEventSet used to implement WaitLatch() */
static WaitEventSet *LatchWaitSet;
#define LatchWaitSetLatchPos 0
#define LatchWaitSetPostmasterDeathPos 1
-#ifndef WIN32
-/* Are we currently in WaitLatch? The signal handler would like to know. */
-static volatile sig_atomic_t waiting = false;
-#endif
-
-#ifdef WAIT_USE_SIGNALFD
-/* On Linux, we'll receive SIGURG via a signalfd file descriptor. */
-static int signal_fd = -1;
-#endif
-
-#ifdef WAIT_USE_SELF_PIPE
-/* Read and write ends of the self-pipe */
-static int selfpipe_readfd = -1;
-static int selfpipe_writefd = -1;
-
-/* Process owning the self-pipe --- needed for checking purposes */
-static int selfpipe_owner_pid = 0;
-
-/* Private function prototypes */
-static void latch_sigurg_handler(SIGNAL_ARGS);
-static void sendSelfPipeByte(void);
-#endif
-
-#if defined(WAIT_USE_SELF_PIPE) || defined(WAIT_USE_SIGNALFD)
-static void drain(void);
-#endif
-
-#if defined(WAIT_USE_EPOLL)
-static void WaitEventAdjustEpoll(WaitEventSet *set, WaitEvent *event, int action);
-#elif defined(WAIT_USE_KQUEUE)
-static void WaitEventAdjustKqueue(WaitEventSet *set, WaitEvent *event, int old_events);
-#elif defined(WAIT_USE_POLL)
-static void WaitEventAdjustPoll(WaitEventSet *set, WaitEvent *event);
-#elif defined(WAIT_USE_WIN32)
-static void WaitEventAdjustWin32(WaitEventSet *set, WaitEvent *event);
-#endif
-
-static inline int WaitEventSetWaitBlock(WaitEventSet *set, int cur_timeout,
- WaitEvent *occurred_events, int nevents);
-
-/* ResourceOwner support to hold WaitEventSets */
-static void ResOwnerReleaseWaitEventSet(Datum res);
-
-static const ResourceOwnerDesc wait_event_set_resowner_desc =
-{
- .name = "WaitEventSet",
- .release_phase = RESOURCE_RELEASE_AFTER_LOCKS,
- .release_priority = RELEASE_PRIO_WAITEVENTSETS,
- .ReleaseResource = ResOwnerReleaseWaitEventSet,
- .DebugPrint = NULL
-};
-
-/* Convenience wrappers over ResourceOwnerRemember/Forget */
-static inline void
-ResourceOwnerRememberWaitEventSet(ResourceOwner owner, WaitEventSet *set)
-{
- ResourceOwnerRemember(owner, PointerGetDatum(set), &wait_event_set_resowner_desc);
-}
-static inline void
-ResourceOwnerForgetWaitEventSet(ResourceOwner owner, WaitEventSet *set)
-{
- ResourceOwnerForget(owner, PointerGetDatum(set), &wait_event_set_resowner_desc);
-}
-
-
-/*
- * Initialize the process-local latch infrastructure.
- *
- * This must be called once during startup of any process that can wait on
- * latches, before it issues any InitLatch() or OwnLatch() calls.
- */
-void
-InitializeLatchSupport(void)
-{
-#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
-}
-
void
InitializeLatchWaitSet(void)
{
latch->owner_pid = MyProcPid;
latch->is_shared = false;
-#if defined(WAIT_USE_SELF_PIPE)
- /* Assert InitializeLatchSupport has been called in this process */
- Assert(selfpipe_readfd >= 0 && selfpipe_owner_pid == MyProcPid);
-#elif defined(WAIT_USE_SIGNALFD)
- /* Assert InitializeLatchSupport has been called in this process */
- Assert(signal_fd >= 0);
-#elif defined(WAIT_USE_WIN32)
+#ifdef WIN32
latch->event = CreateEvent(NULL, TRUE, FALSE, NULL);
if (latch->event == NULL)
elog(ERROR, "CreateEvent failed: error code %lu", GetLastError());
/* Sanity checks */
Assert(latch->is_shared);
-#if defined(WAIT_USE_SELF_PIPE)
- /* Assert InitializeLatchSupport has been called in this process */
- Assert(selfpipe_readfd >= 0 && selfpipe_owner_pid == MyProcPid);
-#elif defined(WAIT_USE_SIGNALFD)
- /* Assert InitializeLatchSupport has been called in this process */
- Assert(signal_fd >= 0);
-#endif
-
owner_pid = latch->owner_pid;
if (owner_pid != 0)
elog(PANIC, "latch already owned by PID %d", owner_pid);
if (owner_pid == 0)
return;
else if (owner_pid == MyProcPid)
- {
-#if defined(WAIT_USE_SELF_PIPE)
- if (waiting)
- sendSelfPipeByte();
-#else
- if (waiting)
- kill(MyProcPid, SIGURG);
-#endif
- }
+ WakeupMyProc();
else
- kill(owner_pid, SIGURG);
+ WakeupOtherProc(owner_pid);
#else
*/
pg_memory_barrier();
}
-
-/*
- * Create a WaitEventSet with space for nevents different events to wait for.
- *
- * These events can then be efficiently waited upon together, using
- * WaitEventSetWait().
- *
- * The WaitEventSet is tracked by the given 'resowner'. Use NULL for session
- * lifetime.
- */
-WaitEventSet *
-CreateWaitEventSet(ResourceOwner resowner, int nevents)
-{
- 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;
-}
-
-/*
- * Free a previously created WaitEventSet.
- *
- * Note: preferably, this shouldn't have to free any resources that could be
- * inherited across an exec(). If it did, we'd likely leak those resources in
- * many scenarios. For the epoll case, we ensure that by setting EPOLL_CLOEXEC
- * when the FD is created. For the Windows case, we assume that the handles
- * involved are non-inheritable.
- */
-void
-FreeWaitEventSet(WaitEventSet *set)
-{
- 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);
-}
-
-/*
- * Free a previously created WaitEventSet in a child process after a fork().
- */
-void
-FreeWaitEventSetAfterFork(WaitEventSet *set)
-{
-#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);
-}
-
-/* ---
- * Add an event to the set. Possible events are:
- * - WL_LATCH_SET: Wait for the latch to be set
- * - WL_POSTMASTER_DEATH: Wait for postmaster to die
- * - WL_SOCKET_READABLE: Wait for socket to become readable,
- * can be combined in one event with other WL_SOCKET_* events
- * - WL_SOCKET_WRITEABLE: Wait for socket to become writeable,
- * can be combined with other WL_SOCKET_* events
- * - WL_SOCKET_CONNECTED: Wait for socket connection to be established,
- * can be combined with other WL_SOCKET_* events (on non-Windows
- * platforms, this is the same as WL_SOCKET_WRITEABLE)
- * - WL_SOCKET_ACCEPT: Wait for new connection to a server socket,
- * can be combined with other WL_SOCKET_* events (on non-Windows
- * platforms, this is the same as WL_SOCKET_READABLE)
- * - WL_SOCKET_CLOSED: Wait for socket to be closed by remote peer.
- * - WL_EXIT_ON_PM_DEATH: Exit immediately if the postmaster dies
- *
- * Returns the offset in WaitEventSet->events (starting from 0), which can be
- * used to modify previously added wait events using ModifyWaitEvent().
- *
- * In the WL_LATCH_SET case the latch must be owned by the current process,
- * i.e. it must be a process-local latch initialized with InitLatch, or a
- * shared latch associated with the current process by calling OwnLatch.
- *
- * In the WL_SOCKET_READABLE/WRITEABLE/CONNECTED/ACCEPT cases, EOF and error
- * conditions cause the socket to be reported as readable/writable/connected,
- * so that the caller can deal with the condition.
- *
- * The user_data pointer specified here will be set for the events returned
- * by WaitEventSetWait(), allowing to easily associate additional data with
- * events.
- */
-int
-AddWaitEventToSet(WaitEventSet *set, uint32 events, pgsocket fd, Latch *latch,
- void *user_data)
-{
- 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;
-}
-
-/*
- * Change the event mask and, in the WL_LATCH_SET case, the latch associated
- * with the WaitEvent. The latch may be changed to NULL to disable the latch
- * temporarily, and then set back to a latch later.
- *
- * 'pos' is the id returned by AddWaitEventToSet.
- */
-void
-ModifyWaitEvent(WaitEventSet *set, int pos, uint32 events, Latch *latch)
-{
- 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
-}
-
-#if defined(WAIT_USE_EPOLL)
-/*
- * action can be one of EPOLL_CTL_ADD | EPOLL_CTL_MOD | EPOLL_CTL_DEL
- */
-static void
-WaitEventAdjustEpoll(WaitEventSet *set, WaitEvent *event, int action)
-{
- struct epoll_event epoll_ev;
- int rc;
-
- /* pointer to our event, returned by epoll_wait */
- epoll_ev.data.ptr = event;
- /* always wait for errors */
- epoll_ev.events = EPOLLERR | EPOLLHUP;
-
- /* prepare pollfd entry once */
- if (event->events == WL_LATCH_SET)
- {
- Assert(set->latch != NULL);
- epoll_ev.events |= EPOLLIN;
- }
- else if (event->events == WL_POSTMASTER_DEATH)
- {
- epoll_ev.events |= EPOLLIN;
- }
- else
- {
- Assert(event->fd != PGINVALID_SOCKET);
- Assert(event->events & (WL_SOCKET_READABLE |
- WL_SOCKET_WRITEABLE |
- WL_SOCKET_CLOSED));
-
- if (event->events & WL_SOCKET_READABLE)
- epoll_ev.events |= EPOLLIN;
- if (event->events & WL_SOCKET_WRITEABLE)
- epoll_ev.events |= EPOLLOUT;
- if (event->events & WL_SOCKET_CLOSED)
- epoll_ev.events |= EPOLLRDHUP;
- }
-
- /*
- * Even though unused, we also pass epoll_ev as the data argument if
- * EPOLL_CTL_DEL is passed as action. There used to be an epoll bug
- * requiring that, and actually it makes the code simpler...
- */
- rc = epoll_ctl(set->epoll_fd, action, event->fd, &epoll_ev);
-
- if (rc < 0)
- ereport(ERROR,
- (errcode_for_socket_access(),
- errmsg("%s() failed: %m",
- "epoll_ctl")));
-}
-#endif
-
-#if defined(WAIT_USE_POLL)
-static void
-WaitEventAdjustPoll(WaitEventSet *set, WaitEvent *event)
-{
- struct pollfd *pollfd = &set->pollfds[event->pos];
-
- pollfd->revents = 0;
- pollfd->fd = event->fd;
-
- /* prepare pollfd entry once */
- if (event->events == WL_LATCH_SET)
- {
- Assert(set->latch != NULL);
- pollfd->events = POLLIN;
- }
- else if (event->events == WL_POSTMASTER_DEATH)
- {
- pollfd->events = POLLIN;
- }
- else
- {
- Assert(event->events & (WL_SOCKET_READABLE |
- WL_SOCKET_WRITEABLE |
- WL_SOCKET_CLOSED));
- pollfd->events = 0;
- if (event->events & WL_SOCKET_READABLE)
- pollfd->events |= POLLIN;
- if (event->events & WL_SOCKET_WRITEABLE)
- pollfd->events |= POLLOUT;
-#ifdef POLLRDHUP
- if (event->events & WL_SOCKET_CLOSED)
- pollfd->events |= POLLRDHUP;
-#endif
- }
-
- Assert(event->fd != PGINVALID_SOCKET);
-}
-#endif
-
-#if defined(WAIT_USE_KQUEUE)
-
-/*
- * On most BSD family systems, the udata member of struct kevent is of type
- * void *, so we could directly convert to/from WaitEvent *. Unfortunately,
- * NetBSD has it as intptr_t, so here we wallpaper over that difference with
- * an lvalue cast.
- */
-#define AccessWaitEvent(k_ev) (*((WaitEvent **)(&(k_ev)->udata)))
-
-static inline void
-WaitEventAdjustKqueueAdd(struct kevent *k_ev, int filter, int action,
- WaitEvent *event)
-{
- k_ev->ident = event->fd;
- k_ev->filter = filter;
- k_ev->flags = action;
- k_ev->fflags = 0;
- k_ev->data = 0;
- AccessWaitEvent(k_ev) = event;
-}
-
-static inline void
-WaitEventAdjustKqueueAddPostmaster(struct kevent *k_ev, WaitEvent *event)
-{
- /* For now postmaster death can only be added, not removed. */
- k_ev->ident = PostmasterPid;
- k_ev->filter = EVFILT_PROC;
- k_ev->flags = EV_ADD;
- k_ev->fflags = NOTE_EXIT;
- k_ev->data = 0;
- AccessWaitEvent(k_ev) = event;
-}
-
-static inline void
-WaitEventAdjustKqueueAddLatch(struct kevent *k_ev, WaitEvent *event)
-{
- /* For now latch can only be added, not removed. */
- k_ev->ident = SIGURG;
- k_ev->filter = EVFILT_SIGNAL;
- k_ev->flags = EV_ADD;
- k_ev->fflags = 0;
- k_ev->data = 0;
- AccessWaitEvent(k_ev) = event;
-}
-
-/*
- * old_events is the previous event mask, used to compute what has changed.
- */
-static void
-WaitEventAdjustKqueue(WaitEventSet *set, WaitEvent *event, int old_events)
-{
- int rc;
- struct kevent k_ev[2];
- int count = 0;
- bool new_filt_read = false;
- bool old_filt_read = false;
- bool new_filt_write = false;
- bool old_filt_write = false;
-
- if (old_events == event->events)
- return;
-
- Assert(event->events != WL_LATCH_SET || set->latch != NULL);
- Assert(event->events == WL_LATCH_SET ||
- event->events == WL_POSTMASTER_DEATH ||
- (event->events & (WL_SOCKET_READABLE |
- WL_SOCKET_WRITEABLE |
- WL_SOCKET_CLOSED)));
-
- if (event->events == WL_POSTMASTER_DEATH)
- {
- /*
- * Unlike all the other implementations, we detect postmaster death
- * using process notification instead of waiting on the postmaster
- * alive pipe.
- */
- WaitEventAdjustKqueueAddPostmaster(&k_ev[count++], event);
- }
- else if (event->events == WL_LATCH_SET)
- {
- /* We detect latch wakeup using a signal event. */
- WaitEventAdjustKqueueAddLatch(&k_ev[count++], event);
- }
- else
- {
- /*
- * We need to compute the adds and deletes required to get from the
- * old event mask to the new event mask, since kevent treats readable
- * and writable as separate events.
- */
- if (old_events & (WL_SOCKET_READABLE | WL_SOCKET_CLOSED))
- old_filt_read = true;
- if (event->events & (WL_SOCKET_READABLE | WL_SOCKET_CLOSED))
- new_filt_read = true;
- if (old_events & WL_SOCKET_WRITEABLE)
- old_filt_write = true;
- if (event->events & WL_SOCKET_WRITEABLE)
- new_filt_write = true;
- if (old_filt_read && !new_filt_read)
- WaitEventAdjustKqueueAdd(&k_ev[count++], EVFILT_READ, EV_DELETE,
- event);
- else if (!old_filt_read && new_filt_read)
- WaitEventAdjustKqueueAdd(&k_ev[count++], EVFILT_READ, EV_ADD,
- event);
- if (old_filt_write && !new_filt_write)
- WaitEventAdjustKqueueAdd(&k_ev[count++], EVFILT_WRITE, EV_DELETE,
- event);
- else if (!old_filt_write && new_filt_write)
- WaitEventAdjustKqueueAdd(&k_ev[count++], EVFILT_WRITE, EV_ADD,
- event);
- }
-
- /* For WL_SOCKET_READ -> WL_SOCKET_CLOSED, no change needed. */
- if (count == 0)
- return;
-
- Assert(count <= 2);
-
- rc = kevent(set->kqueue_fd, &k_ev[0], count, NULL, 0, NULL);
-
- /*
- * When adding the postmaster's pid, we have to consider that it might
- * already have exited and perhaps even been replaced by another process
- * with the same pid. If so, we have to defer reporting this as an event
- * until the next call to WaitEventSetWaitBlock().
- */
-
- if (rc < 0)
- {
- if (event->events == WL_POSTMASTER_DEATH &&
- (errno == ESRCH || errno == EACCES))
- set->report_postmaster_not_running = true;
- else
- ereport(ERROR,
- (errcode_for_socket_access(),
- errmsg("%s() failed: %m",
- "kevent")));
- }
- else if (event->events == WL_POSTMASTER_DEATH &&
- PostmasterPid != getppid() &&
- !PostmasterIsAlive())
- {
- /*
- * The extra PostmasterIsAliveInternal() check prevents false alarms
- * on systems that give a different value for getppid() while being
- * traced by a debugger.
- */
- set->report_postmaster_not_running = true;
- }
-}
-
-#endif
-
-#if defined(WAIT_USE_WIN32)
-static void
-WaitEventAdjustWin32(WaitEventSet *set, WaitEvent *event)
-{
- HANDLE *handle = &set->handles[event->pos + 1];
-
- if (event->events == WL_LATCH_SET)
- {
- Assert(set->latch != NULL);
- *handle = set->latch->event;
- }
- else if (event->events == WL_POSTMASTER_DEATH)
- {
- *handle = PostmasterHandle;
- }
- else
- {
- int flags = FD_CLOSE; /* always check for errors/EOF */
-
- if (event->events & WL_SOCKET_READABLE)
- flags |= FD_READ;
- if (event->events & WL_SOCKET_WRITEABLE)
- flags |= FD_WRITE;
- if (event->events & WL_SOCKET_CONNECTED)
- flags |= FD_CONNECT;
- if (event->events & WL_SOCKET_ACCEPT)
- flags |= FD_ACCEPT;
-
- if (*handle == WSA_INVALID_EVENT)
- {
- *handle = WSACreateEvent();
- if (*handle == WSA_INVALID_EVENT)
- elog(ERROR, "failed to create event for socket: error code %d",
- WSAGetLastError());
- }
- if (WSAEventSelect(event->fd, *handle, flags) != 0)
- elog(ERROR, "failed to set up event for socket: error code %d",
- WSAGetLastError());
-
- Assert(event->fd != PGINVALID_SOCKET);
- }
-}
-#endif
-
-/*
- * Wait for events added to the set to happen, or until the timeout is
- * reached. At most nevents occurred events are returned.
- *
- * If timeout = -1, block until an event occurs; if 0, check sockets for
- * readiness, but don't block; if > 0, block for at most timeout milliseconds.
- *
- * Returns the number of events occurred, or 0 if the timeout was reached.
- *
- * Returned events will have the fd, pos, user_data fields set to the
- * values associated with the registered event.
- */
-int
-WaitEventSetWait(WaitEventSet *set, long timeout,
- WaitEvent *occurred_events, int nevents,
- uint32 wait_event_info)
-{
- 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;
-}
-
-
-#if defined(WAIT_USE_EPOLL)
-
-/*
- * Wait using linux's epoll_wait(2).
- *
- * This is the preferable wait method, as several readiness notifications are
- * delivered, without having to iterate through all of set->events. The return
- * epoll_event struct contain a pointer to our events, making association
- * easy.
- */
-static inline int
-WaitEventSetWaitBlock(WaitEventSet *set, int cur_timeout,
- WaitEvent *occurred_events, int nevents)
-{
- int returned_events = 0;
- int rc;
- WaitEvent *cur_event;
- struct epoll_event *cur_epoll_event;
-
- /* Sleep */
- rc = epoll_wait(set->epoll_fd, set->epoll_ret_events,
- Min(nevents, set->nevents_space), cur_timeout);
-
- /* Check return code */
- if (rc < 0)
- {
- /* EINTR is okay, otherwise complain */
- if (errno != EINTR)
- {
- waiting = false;
- ereport(ERROR,
- (errcode_for_socket_access(),
- errmsg("%s() failed: %m",
- "epoll_wait")));
- }
- return 0;
- }
- else if (rc == 0)
- {
- /* timeout exceeded */
- return -1;
- }
-
- /*
- * At least one event occurred, iterate over the returned epoll events
- * until they're either all processed, or we've returned all the events
- * the caller desired.
- */
- for (cur_epoll_event = set->epoll_ret_events;
- cur_epoll_event < (set->epoll_ret_events + rc) &&
- returned_events < nevents;
- cur_epoll_event++)
- {
- /* epoll's data pointer is set to the associated WaitEvent */
- cur_event = (WaitEvent *) cur_epoll_event->data.ptr;
-
- occurred_events->pos = cur_event->pos;
- occurred_events->user_data = cur_event->user_data;
- occurred_events->events = 0;
-
- if (cur_event->events == WL_LATCH_SET &&
- cur_epoll_event->events & (EPOLLIN | EPOLLERR | EPOLLHUP))
- {
- /* Drain the signalfd. */
- drain();
-
- if (set->latch && set->latch->maybe_sleeping && set->latch->is_set)
- {
- occurred_events->fd = PGINVALID_SOCKET;
- occurred_events->events = WL_LATCH_SET;
- occurred_events++;
- returned_events++;
- }
- }
- else if (cur_event->events == WL_POSTMASTER_DEATH &&
- cur_epoll_event->events & (EPOLLIN | EPOLLERR | EPOLLHUP))
- {
- /*
- * We expect an EPOLLHUP when the remote end is closed, but
- * because we don't expect the pipe to become readable or to have
- * any errors either, treat those cases as postmaster death, too.
- *
- * Be paranoid about a spurious event signaling the postmaster as
- * being dead. There have been reports about that happening with
- * older primitives (select(2) to be specific), and a spurious
- * WL_POSTMASTER_DEATH event would be painful. Re-checking doesn't
- * cost much.
- */
- if (!PostmasterIsAliveInternal())
- {
- if (set->exit_on_postmaster_death)
- proc_exit(1);
- occurred_events->fd = PGINVALID_SOCKET;
- occurred_events->events = WL_POSTMASTER_DEATH;
- occurred_events++;
- returned_events++;
- }
- }
- else if (cur_event->events & (WL_SOCKET_READABLE |
- WL_SOCKET_WRITEABLE |
- WL_SOCKET_CLOSED))
- {
- Assert(cur_event->fd != PGINVALID_SOCKET);
-
- if ((cur_event->events & WL_SOCKET_READABLE) &&
- (cur_epoll_event->events & (EPOLLIN | EPOLLERR | EPOLLHUP)))
- {
- /* data available in socket, or EOF */
- occurred_events->events |= WL_SOCKET_READABLE;
- }
-
- if ((cur_event->events & WL_SOCKET_WRITEABLE) &&
- (cur_epoll_event->events & (EPOLLOUT | EPOLLERR | EPOLLHUP)))
- {
- /* writable, or EOF */
- occurred_events->events |= WL_SOCKET_WRITEABLE;
- }
-
- if ((cur_event->events & WL_SOCKET_CLOSED) &&
- (cur_epoll_event->events & (EPOLLRDHUP | EPOLLERR | EPOLLHUP)))
- {
- /* remote peer shut down, or error */
- occurred_events->events |= WL_SOCKET_CLOSED;
- }
-
- if (occurred_events->events != 0)
- {
- occurred_events->fd = cur_event->fd;
- occurred_events++;
- returned_events++;
- }
- }
- }
-
- return returned_events;
-}
-
-#elif defined(WAIT_USE_KQUEUE)
-
-/*
- * Wait using kevent(2) on BSD-family systems and macOS.
- *
- * For now this mirrors the epoll code, but in future it could modify the fd
- * set in the same call to kevent as it uses for waiting instead of doing that
- * with separate system calls.
- */
-static int
-WaitEventSetWaitBlock(WaitEventSet *set, int cur_timeout,
- WaitEvent *occurred_events, int nevents)
-{
- int returned_events = 0;
- int rc;
- WaitEvent *cur_event;
- struct kevent *cur_kqueue_event;
- struct timespec timeout;
- struct timespec *timeout_p;
-
- if (cur_timeout < 0)
- timeout_p = NULL;
- else
- {
- timeout.tv_sec = cur_timeout / 1000;
- timeout.tv_nsec = (cur_timeout % 1000) * 1000000;
- timeout_p = &timeout;
- }
-
- /*
- * Report postmaster events discovered by WaitEventAdjustKqueue() or an
- * earlier call to WaitEventSetWait().
- */
- if (unlikely(set->report_postmaster_not_running))
- {
- if (set->exit_on_postmaster_death)
- proc_exit(1);
- occurred_events->fd = PGINVALID_SOCKET;
- occurred_events->events = WL_POSTMASTER_DEATH;
- return 1;
- }
-
- /* Sleep */
- rc = kevent(set->kqueue_fd, NULL, 0,
- set->kqueue_ret_events,
- Min(nevents, set->nevents_space),
- timeout_p);
-
- /* Check return code */
- if (rc < 0)
- {
- /* EINTR is okay, otherwise complain */
- if (errno != EINTR)
- {
- waiting = false;
- ereport(ERROR,
- (errcode_for_socket_access(),
- errmsg("%s() failed: %m",
- "kevent")));
- }
- return 0;
- }
- else if (rc == 0)
- {
- /* timeout exceeded */
- return -1;
- }
-
- /*
- * At least one event occurred, iterate over the returned kqueue events
- * until they're either all processed, or we've returned all the events
- * the caller desired.
- */
- for (cur_kqueue_event = set->kqueue_ret_events;
- cur_kqueue_event < (set->kqueue_ret_events + rc) &&
- returned_events < nevents;
- cur_kqueue_event++)
- {
- /* kevent's udata points to the associated WaitEvent */
- cur_event = AccessWaitEvent(cur_kqueue_event);
-
- occurred_events->pos = cur_event->pos;
- occurred_events->user_data = cur_event->user_data;
- occurred_events->events = 0;
-
- if (cur_event->events == WL_LATCH_SET &&
- cur_kqueue_event->filter == EVFILT_SIGNAL)
- {
- if (set->latch && set->latch->maybe_sleeping && set->latch->is_set)
- {
- occurred_events->fd = PGINVALID_SOCKET;
- occurred_events->events = WL_LATCH_SET;
- occurred_events++;
- returned_events++;
- }
- }
- else if (cur_event->events == WL_POSTMASTER_DEATH &&
- cur_kqueue_event->filter == EVFILT_PROC &&
- (cur_kqueue_event->fflags & NOTE_EXIT) != 0)
- {
- /*
- * The kernel will tell this kqueue object only once about the
- * exit of the postmaster, so let's remember that for next time so
- * that we provide level-triggered semantics.
- */
- set->report_postmaster_not_running = true;
-
- if (set->exit_on_postmaster_death)
- proc_exit(1);
- occurred_events->fd = PGINVALID_SOCKET;
- occurred_events->events = WL_POSTMASTER_DEATH;
- occurred_events++;
- returned_events++;
- }
- else if (cur_event->events & (WL_SOCKET_READABLE |
- WL_SOCKET_WRITEABLE |
- WL_SOCKET_CLOSED))
- {
- Assert(cur_event->fd >= 0);
-
- if ((cur_event->events & WL_SOCKET_READABLE) &&
- (cur_kqueue_event->filter == EVFILT_READ))
- {
- /* readable, or EOF */
- occurred_events->events |= WL_SOCKET_READABLE;
- }
-
- if ((cur_event->events & WL_SOCKET_CLOSED) &&
- (cur_kqueue_event->filter == EVFILT_READ) &&
- (cur_kqueue_event->flags & EV_EOF))
- {
- /* the remote peer has shut down */
- occurred_events->events |= WL_SOCKET_CLOSED;
- }
-
- if ((cur_event->events & WL_SOCKET_WRITEABLE) &&
- (cur_kqueue_event->filter == EVFILT_WRITE))
- {
- /* writable, or EOF */
- occurred_events->events |= WL_SOCKET_WRITEABLE;
- }
-
- if (occurred_events->events != 0)
- {
- occurred_events->fd = cur_event->fd;
- occurred_events++;
- returned_events++;
- }
- }
- }
-
- return returned_events;
-}
-
-#elif defined(WAIT_USE_POLL)
-
-/*
- * Wait using poll(2).
- *
- * This allows to receive readiness notifications for several events at once,
- * but requires iterating through all of set->pollfds.
- */
-static inline int
-WaitEventSetWaitBlock(WaitEventSet *set, int cur_timeout,
- WaitEvent *occurred_events, int nevents)
-{
- int returned_events = 0;
- int rc;
- WaitEvent *cur_event;
- struct pollfd *cur_pollfd;
-
- /* Sleep */
- rc = poll(set->pollfds, set->nevents, (int) cur_timeout);
-
- /* Check return code */
- if (rc < 0)
- {
- /* EINTR is okay, otherwise complain */
- if (errno != EINTR)
- {
- waiting = false;
- ereport(ERROR,
- (errcode_for_socket_access(),
- errmsg("%s() failed: %m",
- "poll")));
- }
- return 0;
- }
- else if (rc == 0)
- {
- /* timeout exceeded */
- return -1;
- }
-
- for (cur_event = set->events, cur_pollfd = set->pollfds;
- cur_event < (set->events + set->nevents) &&
- returned_events < nevents;
- cur_event++, cur_pollfd++)
- {
- /* no activity on this FD, skip */
- if (cur_pollfd->revents == 0)
- continue;
-
- occurred_events->pos = cur_event->pos;
- occurred_events->user_data = cur_event->user_data;
- occurred_events->events = 0;
-
- if (cur_event->events == WL_LATCH_SET &&
- (cur_pollfd->revents & (POLLIN | POLLHUP | POLLERR | POLLNVAL)))
- {
- /* There's data in the self-pipe, clear it. */
- drain();
-
- if (set->latch && set->latch->maybe_sleeping && set->latch->is_set)
- {
- occurred_events->fd = PGINVALID_SOCKET;
- occurred_events->events = WL_LATCH_SET;
- occurred_events++;
- returned_events++;
- }
- }
- else if (cur_event->events == WL_POSTMASTER_DEATH &&
- (cur_pollfd->revents & (POLLIN | POLLHUP | POLLERR | POLLNVAL)))
- {
- /*
- * We expect an POLLHUP when the remote end is closed, but because
- * we don't expect the pipe to become readable or to have any
- * errors either, treat those cases as postmaster death, too.
- *
- * Be paranoid about a spurious event signaling the postmaster as
- * being dead. There have been reports about that happening with
- * older primitives (select(2) to be specific), and a spurious
- * WL_POSTMASTER_DEATH event would be painful. Re-checking doesn't
- * cost much.
- */
- if (!PostmasterIsAliveInternal())
- {
- if (set->exit_on_postmaster_death)
- proc_exit(1);
- occurred_events->fd = PGINVALID_SOCKET;
- occurred_events->events = WL_POSTMASTER_DEATH;
- occurred_events++;
- returned_events++;
- }
- }
- else if (cur_event->events & (WL_SOCKET_READABLE |
- WL_SOCKET_WRITEABLE |
- WL_SOCKET_CLOSED))
- {
- int errflags = POLLHUP | POLLERR | POLLNVAL;
-
- Assert(cur_event->fd >= PGINVALID_SOCKET);
-
- if ((cur_event->events & WL_SOCKET_READABLE) &&
- (cur_pollfd->revents & (POLLIN | errflags)))
- {
- /* data available in socket, or EOF */
- occurred_events->events |= WL_SOCKET_READABLE;
- }
-
- if ((cur_event->events & WL_SOCKET_WRITEABLE) &&
- (cur_pollfd->revents & (POLLOUT | errflags)))
- {
- /* writeable, or EOF */
- occurred_events->events |= WL_SOCKET_WRITEABLE;
- }
-
-#ifdef POLLRDHUP
- if ((cur_event->events & WL_SOCKET_CLOSED) &&
- (cur_pollfd->revents & (POLLRDHUP | errflags)))
- {
- /* remote peer closed, or error */
- occurred_events->events |= WL_SOCKET_CLOSED;
- }
-#endif
-
- if (occurred_events->events != 0)
- {
- occurred_events->fd = cur_event->fd;
- occurred_events++;
- returned_events++;
- }
- }
- }
- return returned_events;
-}
-
-#elif defined(WAIT_USE_WIN32)
-
-/*
- * Wait using Windows' WaitForMultipleObjects(). Each call only "consumes" one
- * event, so we keep calling until we've filled up our output buffer to match
- * the behavior of the other implementations.
- *
- * https://blogs.msdn.microsoft.com/oldnewthing/20150409-00/?p=44273
- */
-static inline int
-WaitEventSetWaitBlock(WaitEventSet *set, int cur_timeout,
- WaitEvent *occurred_events, int nevents)
-{
- int returned_events = 0;
- DWORD rc;
- WaitEvent *cur_event;
-
- /* Reset any wait events that need it */
- for (cur_event = set->events;
- cur_event < (set->events + set->nevents);
- cur_event++)
- {
- if (cur_event->reset)
- {
- WaitEventAdjustWin32(set, cur_event);
- cur_event->reset = false;
- }
-
- /*
- * We associate the socket with a new event handle for each
- * WaitEventSet. FD_CLOSE is only generated once if the other end
- * closes gracefully. Therefore we might miss the FD_CLOSE
- * notification, if it was delivered to another event after we stopped
- * waiting for it. Close that race by peeking for EOF after setting
- * up this handle to receive notifications, and before entering the
- * sleep.
- *
- * XXX If we had one event handle for the lifetime of a socket, we
- * wouldn't need this.
- */
- if (cur_event->events & WL_SOCKET_READABLE)
- {
- char c;
- WSABUF buf;
- DWORD received;
- DWORD flags;
-
- buf.buf = &c;
- buf.len = 1;
- flags = MSG_PEEK;
- if (WSARecv(cur_event->fd, &buf, 1, &received, &flags, NULL, NULL) == 0)
- {
- occurred_events->pos = cur_event->pos;
- occurred_events->user_data = cur_event->user_data;
- occurred_events->events = WL_SOCKET_READABLE;
- occurred_events->fd = cur_event->fd;
- return 1;
- }
- }
-
- /*
- * Windows does not guarantee to log an FD_WRITE network event
- * indicating that more data can be sent unless the previous send()
- * failed with WSAEWOULDBLOCK. While our caller might well have made
- * such a call, we cannot assume that here. Therefore, if waiting for
- * write-ready, force the issue by doing a dummy send(). If the dummy
- * send() succeeds, assume that the socket is in fact write-ready, and
- * return immediately. Also, if it fails with something other than
- * WSAEWOULDBLOCK, return a write-ready indication to let our caller
- * deal with the error condition.
- */
- if (cur_event->events & WL_SOCKET_WRITEABLE)
- {
- char c;
- WSABUF buf;
- DWORD sent;
- int r;
-
- buf.buf = &c;
- buf.len = 0;
-
- r = WSASend(cur_event->fd, &buf, 1, &sent, 0, NULL, NULL);
- if (r == 0 || WSAGetLastError() != WSAEWOULDBLOCK)
- {
- occurred_events->pos = cur_event->pos;
- occurred_events->user_data = cur_event->user_data;
- occurred_events->events = WL_SOCKET_WRITEABLE;
- occurred_events->fd = cur_event->fd;
- return 1;
- }
- }
- }
-
- /*
- * Sleep.
- *
- * Need to wait for ->nevents + 1, because signal handle is in [0].
- */
- rc = WaitForMultipleObjects(set->nevents + 1, set->handles, FALSE,
- cur_timeout);
-
- /* Check return code */
- if (rc == WAIT_FAILED)
- elog(ERROR, "WaitForMultipleObjects() failed: error code %lu",
- GetLastError());
- else if (rc == WAIT_TIMEOUT)
- {
- /* timeout exceeded */
- return -1;
- }
-
- if (rc == WAIT_OBJECT_0)
- {
- /* Service newly-arrived signals */
- pgwin32_dispatch_queued_signals();
- return 0; /* retry */
- }
-
- /*
- * With an offset of one, due to the always present pgwin32_signal_event,
- * the handle offset directly corresponds to a wait event.
- */
- cur_event = (WaitEvent *) &set->events[rc - WAIT_OBJECT_0 - 1];
-
- for (;;)
- {
- int next_pos;
- int count;
-
- occurred_events->pos = cur_event->pos;
- occurred_events->user_data = cur_event->user_data;
- occurred_events->events = 0;
-
- if (cur_event->events == WL_LATCH_SET)
- {
- /*
- * We cannot use set->latch->event to reset the fired event if we
- * aren't waiting on this latch now.
- */
- if (!ResetEvent(set->handles[cur_event->pos + 1]))
- elog(ERROR, "ResetEvent failed: error code %lu", GetLastError());
-
- if (set->latch && set->latch->maybe_sleeping && set->latch->is_set)
- {
- occurred_events->fd = PGINVALID_SOCKET;
- occurred_events->events = WL_LATCH_SET;
- occurred_events++;
- returned_events++;
- }
- }
- else if (cur_event->events == WL_POSTMASTER_DEATH)
- {
- /*
- * Postmaster apparently died. Since the consequences of falsely
- * returning WL_POSTMASTER_DEATH could be pretty unpleasant, we
- * take the trouble to positively verify this with
- * PostmasterIsAlive(), even though there is no known reason to
- * think that the event could be falsely set on Windows.
- */
- if (!PostmasterIsAliveInternal())
- {
- if (set->exit_on_postmaster_death)
- proc_exit(1);
- occurred_events->fd = PGINVALID_SOCKET;
- occurred_events->events = WL_POSTMASTER_DEATH;
- occurred_events++;
- returned_events++;
- }
- }
- else if (cur_event->events & WL_SOCKET_MASK)
- {
- WSANETWORKEVENTS resEvents;
- HANDLE handle = set->handles[cur_event->pos + 1];
-
- Assert(cur_event->fd);
-
- occurred_events->fd = cur_event->fd;
-
- ZeroMemory(&resEvents, sizeof(resEvents));
- if (WSAEnumNetworkEvents(cur_event->fd, handle, &resEvents) != 0)
- elog(ERROR, "failed to enumerate network events: error code %d",
- WSAGetLastError());
- if ((cur_event->events & WL_SOCKET_READABLE) &&
- (resEvents.lNetworkEvents & FD_READ))
- {
- /* data available in socket */
- occurred_events->events |= WL_SOCKET_READABLE;
-
- /*------
- * WaitForMultipleObjects doesn't guarantee that a read event
- * will be returned if the latch is set at the same time. Even
- * if it did, the caller might drop that event expecting it to
- * reoccur on next call. So, we must force the event to be
- * reset if this WaitEventSet is used again in order to avoid
- * an indefinite hang.
- *
- * Refer
- * https://msdn.microsoft.com/en-us/library/windows/desktop/ms741576(v=vs.85).aspx
- * for the behavior of socket events.
- *------
- */
- cur_event->reset = true;
- }
- if ((cur_event->events & WL_SOCKET_WRITEABLE) &&
- (resEvents.lNetworkEvents & FD_WRITE))
- {
- /* writeable */
- occurred_events->events |= WL_SOCKET_WRITEABLE;
- }
- if ((cur_event->events & WL_SOCKET_CONNECTED) &&
- (resEvents.lNetworkEvents & FD_CONNECT))
- {
- /* connected */
- occurred_events->events |= WL_SOCKET_CONNECTED;
- }
- if ((cur_event->events & WL_SOCKET_ACCEPT) &&
- (resEvents.lNetworkEvents & FD_ACCEPT))
- {
- /* incoming connection could be accepted */
- occurred_events->events |= WL_SOCKET_ACCEPT;
- }
- if (resEvents.lNetworkEvents & FD_CLOSE)
- {
- /* EOF/error, so signal all caller-requested socket flags */
- occurred_events->events |= (cur_event->events & WL_SOCKET_MASK);
- }
-
- if (occurred_events->events != 0)
- {
- occurred_events++;
- returned_events++;
- }
- }
-
- /* Is the output buffer full? */
- if (returned_events == nevents)
- break;
-
- /* Have we run out of possible events? */
- next_pos = cur_event->pos + 1;
- if (next_pos == set->nevents)
- break;
-
- /*
- * Poll the rest of the event handles in the array starting at
- * next_pos being careful to skip over the initial signal handle too.
- * This time we use a zero timeout.
- */
- count = set->nevents - next_pos;
- rc = WaitForMultipleObjects(count,
- set->handles + 1 + next_pos,
- false,
- 0);
-
- /*
- * We don't distinguish between errors and WAIT_TIMEOUT here because
- * we already have events to report.
- */
- if (rc < WAIT_OBJECT_0 || rc >= WAIT_OBJECT_0 + count)
- break;
-
- /* We have another event to decode. */
- cur_event = &set->events[next_pos + (rc - WAIT_OBJECT_0)];
- }
-
- return returned_events;
-}
-#endif
-
-/*
- * Return whether the current build options can report WL_SOCKET_CLOSED.
- */
-bool
-WaitEventSetCanReportClosed(void)
-{
-#if (defined(WAIT_USE_POLL) && defined(POLLRDHUP)) || \
- defined(WAIT_USE_EPOLL) || \
- defined(WAIT_USE_KQUEUE)
- return true;
-#else
- return false;
-#endif
-}
-
-/*
- * Get the number of wait events registered in a given WaitEventSet.
- */
-int
-GetNumRegisteredWaitEvents(WaitEventSet *set)
-{
- return set->nevents;
-}
-
-#if defined(WAIT_USE_SELF_PIPE)
-
-/*
- * SetLatch uses SIGURG to wake up the process waiting on the latch.
- *
- * Wake up WaitLatch, if we're waiting.
- */
-static void
-latch_sigurg_handler(SIGNAL_ARGS)
-{
- if (waiting)
- sendSelfPipeByte();
-}
-
-/* Send one byte to the self-pipe, to wake up WaitLatch */
-static void
-sendSelfPipeByte(void)
-{
- int rc;
- char dummy = 0;
-
-retry:
- rc = write(selfpipe_writefd, &dummy, 1);
- if (rc < 0)
- {
- /* If interrupted by signal, just retry */
- if (errno == EINTR)
- goto retry;
-
- /*
- * If the pipe is full, we don't need to retry, the data that's there
- * already is enough to wake up WaitLatch.
- */
- if (errno == EAGAIN || errno == EWOULDBLOCK)
- return;
-
- /*
- * Oops, the write() failed for some other reason. We might be in a
- * signal handler, so it's not safe to elog(). We have no choice but
- * silently ignore the error.
- */
- return;
- }
-}
-
-#endif
-
-#if defined(WAIT_USE_SELF_PIPE) || defined(WAIT_USE_SIGNALFD)
-
-/*
- * Read all available data from self-pipe or signalfd.
- *
- * Note: this is only called when waiting = true. If it fails and doesn't
- * return, it must reset that flag first (though ideally, this will never
- * happen).
- */
-static void
-drain(void)
-{
- char buf[1024];
- int rc;
- int fd;
-
-#ifdef WAIT_USE_SELF_PIPE
- fd = selfpipe_readfd;
-#else
- fd = signal_fd;
-#endif
-
- for (;;)
- {
- rc = read(fd, buf, sizeof(buf));
- if (rc < 0)
- {
- if (errno == EAGAIN || errno == EWOULDBLOCK)
- break; /* the descriptor is empty */
- else if (errno == EINTR)
- continue; /* retry */
- else
- {
- waiting = false;
-#ifdef WAIT_USE_SELF_PIPE
- elog(ERROR, "read() on self-pipe failed: %m");
-#else
- elog(ERROR, "read() on signalfd failed: %m");
-#endif
- }
- }
- else if (rc == 0)
- {
- waiting = false;
-#ifdef WAIT_USE_SELF_PIPE
- elog(ERROR, "unexpected EOF on self-pipe");
-#else
- elog(ERROR, "unexpected EOF on signalfd");
-#endif
- }
- else if (rc < sizeof(buf))
- {
- /* we successfully drained the pipe; no need to read() again */
- break;
- }
- /* else buffer wasn't big enough, so read again */
- }
-}
-
-#endif
-
-static void
-ResOwnerReleaseWaitEventSet(Datum res)
-{
- WaitEventSet *set = (WaitEventSet *) DatumGetPointer(res);
-
- Assert(set->owner != NULL);
- set->owner = NULL;
- FreeWaitEventSet(set);
-}
'sinval.c',
'sinvaladt.c',
'standby.c',
+ 'waiteventset.c',
)
--- /dev/null
+/*-------------------------------------------------------------------------
+ *
+ * waiteventset.c
+ * ppoll()/pselect() like abstraction
+ *
+ * WaitEvents are an abstraction for waiting for one or more events at a time.
+ * The waiting can be done in a race free fashion, similar ppoll() or
+ * pselect() (as opposed to plain poll()/select()).
+ *
+ * You can wait for:
+ * - a latch being set from another process or from signal handler in the same
+ * process (WL_LATCH_SET)
+ * - data to become readable or writeable on a socket (WL_SOCKET_*)
+ * - postmaster death (WL_POSTMASTER_DEATH or WL_EXIT_ON_PM_DEATH)
+ * - timeout (WL_TIMEOUT)
+ *
+ * Implementation
+ * --------------
+ *
+ * The poll() implementation uses the so-called self-pipe trick to overcome the
+ * race condition involved with poll() and setting a global flag in the signal
+ * handler. When a latch is set and the current process is waiting for it, the
+ * signal handler wakes up the poll() in WaitLatch by writing a byte to a pipe.
+ * A signal by itself doesn't interrupt poll() on all platforms, and even on
+ * platforms where it does, a signal that arrives just before the poll() call
+ * does not prevent poll() from entering sleep. An incoming byte on a pipe
+ * however reliably interrupts the sleep, and causes poll() to return
+ * immediately even if the signal arrives before poll() begins.
+ *
+ * The epoll() implementation overcomes the race with a different technique: it
+ * keeps SIGURG blocked and consumes from a signalfd() descriptor instead. We
+ * don't need to register a signal handler or create our own self-pipe. We
+ * assume that any system that has Linux epoll() also has Linux signalfd().
+ *
+ * The kqueue() implementation waits for SIGURG with EVFILT_SIGNAL.
+ *
+ * The Windows implementation uses Windows events that are inherited by all
+ * postmaster child processes. There's no need for the self-pipe trick there.
+ *
+ * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ * src/backend/storage/ipc/waiteventset.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include <fcntl.h>
+#include <limits.h>
+#include <signal.h>
+#include <unistd.h>
+#ifdef HAVE_SYS_EPOLL_H
+#include <sys/epoll.h>
+#endif
+#ifdef HAVE_SYS_EVENT_H
+#include <sys/event.h>
+#endif
+#ifdef HAVE_SYS_SIGNALFD_H
+#include <sys/signalfd.h>
+#endif
+#ifdef HAVE_POLL_H
+#include <poll.h>
+#endif
+
+#include "libpq/pqsignal.h"
+#include "miscadmin.h"
+#include "pgstat.h"
+#include "portability/instr_time.h"
+#include "postmaster/postmaster.h"
+#include "storage/fd.h"
+#include "storage/ipc.h"
+#include "storage/pmsignal.h"
+#include "storage/latch.h"
+#include "storage/waiteventset.h"
+#include "utils/memutils.h"
+#include "utils/resowner.h"
+
+/*
+ * Select the fd readiness primitive to use. Normally the "most modern"
+ * primitive supported by the OS will be used, but for testing it can be
+ * useful to manually specify the used primitive. If desired, just add a
+ * define somewhere before this block.
+ */
+#if defined(WAIT_USE_EPOLL) || defined(WAIT_USE_POLL) || \
+ defined(WAIT_USE_KQUEUE) || defined(WAIT_USE_WIN32)
+/* don't overwrite manual choice */
+#elif defined(HAVE_SYS_EPOLL_H)
+#define WAIT_USE_EPOLL
+#elif defined(HAVE_KQUEUE)
+#define WAIT_USE_KQUEUE
+#elif defined(HAVE_POLL)
+#define WAIT_USE_POLL
+#elif WIN32
+#define WAIT_USE_WIN32
+#else
+#error "no wait set implementation available"
+#endif
+
+/*
+ * By default, we use a self-pipe with poll() and a signalfd with epoll(), if
+ * available. For testing the choice can also be manually specified.
+ */
+#if defined(WAIT_USE_POLL) || defined(WAIT_USE_EPOLL)
+#if defined(WAIT_USE_SELF_PIPE) || defined(WAIT_USE_SIGNALFD)
+/* don't overwrite manual choice */
+#elif defined(WAIT_USE_EPOLL) && defined(HAVE_SYS_SIGNALFD_H)
+#define WAIT_USE_SIGNALFD
+#else
+#define WAIT_USE_SELF_PIPE
+#endif
+#endif
+
+/* typedef in waiteventset.h */
+struct WaitEventSet
+{
+ ResourceOwner owner;
+
+ int nevents; /* number of registered events */
+ int nevents_space; /* maximum number of events in this set */
+
+ /*
+ * Array, of nevents_space length, storing the definition of events this
+ * set is waiting for.
+ */
+ WaitEvent *events;
+
+ /*
+ * If WL_LATCH_SET is specified in any wait event, latch is a pointer to
+ * said latch, and latch_pos the offset in the ->events array. This is
+ * useful because we check the state of the latch before performing doing
+ * syscalls related to waiting.
+ */
+ Latch *latch;
+ int latch_pos;
+
+ /*
+ * WL_EXIT_ON_PM_DEATH is converted to WL_POSTMASTER_DEATH, but this flag
+ * is set so that we'll exit immediately if postmaster death is detected,
+ * instead of returning.
+ */
+ bool exit_on_postmaster_death;
+
+#if defined(WAIT_USE_EPOLL)
+ int epoll_fd;
+ /* epoll_wait returns events in a user provided arrays, allocate once */
+ struct epoll_event *epoll_ret_events;
+#elif defined(WAIT_USE_KQUEUE)
+ int kqueue_fd;
+ /* kevent returns events in a user provided arrays, allocate once */
+ struct kevent *kqueue_ret_events;
+ bool report_postmaster_not_running;
+#elif defined(WAIT_USE_POLL)
+ /* poll expects events to be waited on every poll() call, prepare once */
+ struct pollfd *pollfds;
+#elif defined(WAIT_USE_WIN32)
+
+ /*
+ * Array of windows events. The first element always contains
+ * pgwin32_signal_event, so the remaining elements are offset by one (i.e.
+ * event->pos + 1).
+ */
+ HANDLE *handles;
+#endif
+};
+
+#ifndef WIN32
+/* Are we currently in WaitLatch? The signal handler would like to know. */
+static volatile sig_atomic_t waiting = false;
+#endif
+
+#ifdef WAIT_USE_SIGNALFD
+/* On Linux, we'll receive SIGURG via a signalfd file descriptor. */
+static int signal_fd = -1;
+#endif
+
+#ifdef WAIT_USE_SELF_PIPE
+/* Read and write ends of the self-pipe */
+static int selfpipe_readfd = -1;
+static int selfpipe_writefd = -1;
+
+/* Process owning the self-pipe --- needed for checking purposes */
+static int selfpipe_owner_pid = 0;
+
+/* Private function prototypes */
+static void latch_sigurg_handler(SIGNAL_ARGS);
+static void sendSelfPipeByte(void);
+#endif
+
+#if defined(WAIT_USE_SELF_PIPE) || defined(WAIT_USE_SIGNALFD)
+static void drain(void);
+#endif
+
+#if defined(WAIT_USE_EPOLL)
+static void WaitEventAdjustEpoll(WaitEventSet *set, WaitEvent *event, int action);
+#elif defined(WAIT_USE_KQUEUE)
+static void WaitEventAdjustKqueue(WaitEventSet *set, WaitEvent *event, int old_events);
+#elif defined(WAIT_USE_POLL)
+static void WaitEventAdjustPoll(WaitEventSet *set, WaitEvent *event);
+#elif defined(WAIT_USE_WIN32)
+static void WaitEventAdjustWin32(WaitEventSet *set, WaitEvent *event);
+#endif
+
+static inline int WaitEventSetWaitBlock(WaitEventSet *set, int cur_timeout,
+ WaitEvent *occurred_events, int nevents);
+
+/* ResourceOwner support to hold WaitEventSets */
+static void ResOwnerReleaseWaitEventSet(Datum res);
+
+static const ResourceOwnerDesc wait_event_set_resowner_desc =
+{
+ .name = "WaitEventSet",
+ .release_phase = RESOURCE_RELEASE_AFTER_LOCKS,
+ .release_priority = RELEASE_PRIO_WAITEVENTSETS,
+ .ReleaseResource = ResOwnerReleaseWaitEventSet,
+ .DebugPrint = NULL
+};
+
+/* Convenience wrappers over ResourceOwnerRemember/Forget */
+static inline void
+ResourceOwnerRememberWaitEventSet(ResourceOwner owner, WaitEventSet *set)
+{
+ ResourceOwnerRemember(owner, PointerGetDatum(set), &wait_event_set_resowner_desc);
+}
+static inline void
+ResourceOwnerForgetWaitEventSet(ResourceOwner owner, WaitEventSet *set)
+{
+ ResourceOwnerForget(owner, PointerGetDatum(set), &wait_event_set_resowner_desc);
+}
+
+
+/*
+ * Initialize the process-local wait event infrastructure.
+ *
+ * This must be called once during startup of any process that can wait on
+ * latches, before it issues any InitLatch() or OwnLatch() calls.
+ */
+void
+InitializeWaitEventSupport(void)
+{
+#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
+}
+
+/*
+ * Create a WaitEventSet with space for nevents different events to wait for.
+ *
+ * These events can then be efficiently waited upon together, using
+ * WaitEventSetWait().
+ *
+ * The WaitEventSet is tracked by the given 'resowner'. Use NULL for session
+ * lifetime.
+ */
+WaitEventSet *
+CreateWaitEventSet(ResourceOwner resowner, int nevents)
+{
+ 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;
+}
+
+/*
+ * Free a previously created WaitEventSet.
+ *
+ * Note: preferably, this shouldn't have to free any resources that could be
+ * inherited across an exec(). If it did, we'd likely leak those resources in
+ * many scenarios. For the epoll case, we ensure that by setting EPOLL_CLOEXEC
+ * when the FD is created. For the Windows case, we assume that the handles
+ * involved are non-inheritable.
+ */
+void
+FreeWaitEventSet(WaitEventSet *set)
+{
+ 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);
+}
+
+/*
+ * Free a previously created WaitEventSet in a child process after a fork().
+ */
+void
+FreeWaitEventSetAfterFork(WaitEventSet *set)
+{
+#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);
+}
+
+/* ---
+ * Add an event to the set. Possible events are:
+ * - WL_LATCH_SET: Wait for the latch to be set
+ * - WL_POSTMASTER_DEATH: Wait for postmaster to die
+ * - WL_SOCKET_READABLE: Wait for socket to become readable,
+ * can be combined in one event with other WL_SOCKET_* events
+ * - WL_SOCKET_WRITEABLE: Wait for socket to become writeable,
+ * can be combined with other WL_SOCKET_* events
+ * - WL_SOCKET_CONNECTED: Wait for socket connection to be established,
+ * can be combined with other WL_SOCKET_* events (on non-Windows
+ * platforms, this is the same as WL_SOCKET_WRITEABLE)
+ * - WL_SOCKET_ACCEPT: Wait for new connection to a server socket,
+ * can be combined with other WL_SOCKET_* events (on non-Windows
+ * platforms, this is the same as WL_SOCKET_READABLE)
+ * - WL_SOCKET_CLOSED: Wait for socket to be closed by remote peer.
+ * - WL_EXIT_ON_PM_DEATH: Exit immediately if the postmaster dies
+ *
+ * Returns the offset in WaitEventSet->events (starting from 0), which can be
+ * used to modify previously added wait events using ModifyWaitEvent().
+ *
+ * In the WL_LATCH_SET case the latch must be owned by the current process,
+ * i.e. it must be a process-local latch initialized with InitLatch, or a
+ * shared latch associated with the current process by calling OwnLatch.
+ *
+ * In the WL_SOCKET_READABLE/WRITEABLE/CONNECTED/ACCEPT cases, EOF and error
+ * conditions cause the socket to be reported as readable/writable/connected,
+ * so that the caller can deal with the condition.
+ *
+ * The user_data pointer specified here will be set for the events returned
+ * by WaitEventSetWait(), allowing to easily associate additional data with
+ * events.
+ */
+int
+AddWaitEventToSet(WaitEventSet *set, uint32 events, pgsocket fd, Latch *latch,
+ void *user_data)
+{
+ 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;
+}
+
+/*
+ * Change the event mask and, in the WL_LATCH_SET case, the latch associated
+ * with the WaitEvent. The latch may be changed to NULL to disable the latch
+ * temporarily, and then set back to a latch later.
+ *
+ * 'pos' is the id returned by AddWaitEventToSet.
+ */
+void
+ModifyWaitEvent(WaitEventSet *set, int pos, uint32 events, Latch *latch)
+{
+ 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
+}
+
+#if defined(WAIT_USE_EPOLL)
+/*
+ * action can be one of EPOLL_CTL_ADD | EPOLL_CTL_MOD | EPOLL_CTL_DEL
+ */
+static void
+WaitEventAdjustEpoll(WaitEventSet *set, WaitEvent *event, int action)
+{
+ struct epoll_event epoll_ev;
+ int rc;
+
+ /* pointer to our event, returned by epoll_wait */
+ epoll_ev.data.ptr = event;
+ /* always wait for errors */
+ epoll_ev.events = EPOLLERR | EPOLLHUP;
+
+ /* prepare pollfd entry once */
+ if (event->events == WL_LATCH_SET)
+ {
+ Assert(set->latch != NULL);
+ epoll_ev.events |= EPOLLIN;
+ }
+ else if (event->events == WL_POSTMASTER_DEATH)
+ {
+ epoll_ev.events |= EPOLLIN;
+ }
+ else
+ {
+ Assert(event->fd != PGINVALID_SOCKET);
+ Assert(event->events & (WL_SOCKET_READABLE |
+ WL_SOCKET_WRITEABLE |
+ WL_SOCKET_CLOSED));
+
+ if (event->events & WL_SOCKET_READABLE)
+ epoll_ev.events |= EPOLLIN;
+ if (event->events & WL_SOCKET_WRITEABLE)
+ epoll_ev.events |= EPOLLOUT;
+ if (event->events & WL_SOCKET_CLOSED)
+ epoll_ev.events |= EPOLLRDHUP;
+ }
+
+ /*
+ * Even though unused, we also pass epoll_ev as the data argument if
+ * EPOLL_CTL_DEL is passed as action. There used to be an epoll bug
+ * requiring that, and actually it makes the code simpler...
+ */
+ rc = epoll_ctl(set->epoll_fd, action, event->fd, &epoll_ev);
+
+ if (rc < 0)
+ ereport(ERROR,
+ (errcode_for_socket_access(),
+ errmsg("%s() failed: %m",
+ "epoll_ctl")));
+}
+#endif
+
+#if defined(WAIT_USE_POLL)
+static void
+WaitEventAdjustPoll(WaitEventSet *set, WaitEvent *event)
+{
+ struct pollfd *pollfd = &set->pollfds[event->pos];
+
+ pollfd->revents = 0;
+ pollfd->fd = event->fd;
+
+ /* prepare pollfd entry once */
+ if (event->events == WL_LATCH_SET)
+ {
+ Assert(set->latch != NULL);
+ pollfd->events = POLLIN;
+ }
+ else if (event->events == WL_POSTMASTER_DEATH)
+ {
+ pollfd->events = POLLIN;
+ }
+ else
+ {
+ Assert(event->events & (WL_SOCKET_READABLE |
+ WL_SOCKET_WRITEABLE |
+ WL_SOCKET_CLOSED));
+ pollfd->events = 0;
+ if (event->events & WL_SOCKET_READABLE)
+ pollfd->events |= POLLIN;
+ if (event->events & WL_SOCKET_WRITEABLE)
+ pollfd->events |= POLLOUT;
+#ifdef POLLRDHUP
+ if (event->events & WL_SOCKET_CLOSED)
+ pollfd->events |= POLLRDHUP;
+#endif
+ }
+
+ Assert(event->fd != PGINVALID_SOCKET);
+}
+#endif
+
+#if defined(WAIT_USE_KQUEUE)
+
+/*
+ * On most BSD family systems, the udata member of struct kevent is of type
+ * void *, so we could directly convert to/from WaitEvent *. Unfortunately,
+ * NetBSD has it as intptr_t, so here we wallpaper over that difference with
+ * an lvalue cast.
+ */
+#define AccessWaitEvent(k_ev) (*((WaitEvent **)(&(k_ev)->udata)))
+
+static inline void
+WaitEventAdjustKqueueAdd(struct kevent *k_ev, int filter, int action,
+ WaitEvent *event)
+{
+ k_ev->ident = event->fd;
+ k_ev->filter = filter;
+ k_ev->flags = action;
+ k_ev->fflags = 0;
+ k_ev->data = 0;
+ AccessWaitEvent(k_ev) = event;
+}
+
+static inline void
+WaitEventAdjustKqueueAddPostmaster(struct kevent *k_ev, WaitEvent *event)
+{
+ /* For now postmaster death can only be added, not removed. */
+ k_ev->ident = PostmasterPid;
+ k_ev->filter = EVFILT_PROC;
+ k_ev->flags = EV_ADD;
+ k_ev->fflags = NOTE_EXIT;
+ k_ev->data = 0;
+ AccessWaitEvent(k_ev) = event;
+}
+
+static inline void
+WaitEventAdjustKqueueAddLatch(struct kevent *k_ev, WaitEvent *event)
+{
+ /* For now latch can only be added, not removed. */
+ k_ev->ident = SIGURG;
+ k_ev->filter = EVFILT_SIGNAL;
+ k_ev->flags = EV_ADD;
+ k_ev->fflags = 0;
+ k_ev->data = 0;
+ AccessWaitEvent(k_ev) = event;
+}
+
+/*
+ * old_events is the previous event mask, used to compute what has changed.
+ */
+static void
+WaitEventAdjustKqueue(WaitEventSet *set, WaitEvent *event, int old_events)
+{
+ int rc;
+ struct kevent k_ev[2];
+ int count = 0;
+ bool new_filt_read = false;
+ bool old_filt_read = false;
+ bool new_filt_write = false;
+ bool old_filt_write = false;
+
+ if (old_events == event->events)
+ return;
+
+ Assert(event->events != WL_LATCH_SET || set->latch != NULL);
+ Assert(event->events == WL_LATCH_SET ||
+ event->events == WL_POSTMASTER_DEATH ||
+ (event->events & (WL_SOCKET_READABLE |
+ WL_SOCKET_WRITEABLE |
+ WL_SOCKET_CLOSED)));
+
+ if (event->events == WL_POSTMASTER_DEATH)
+ {
+ /*
+ * Unlike all the other implementations, we detect postmaster death
+ * using process notification instead of waiting on the postmaster
+ * alive pipe.
+ */
+ WaitEventAdjustKqueueAddPostmaster(&k_ev[count++], event);
+ }
+ else if (event->events == WL_LATCH_SET)
+ {
+ /* We detect latch wakeup using a signal event. */
+ WaitEventAdjustKqueueAddLatch(&k_ev[count++], event);
+ }
+ else
+ {
+ /*
+ * We need to compute the adds and deletes required to get from the
+ * old event mask to the new event mask, since kevent treats readable
+ * and writable as separate events.
+ */
+ if (old_events & (WL_SOCKET_READABLE | WL_SOCKET_CLOSED))
+ old_filt_read = true;
+ if (event->events & (WL_SOCKET_READABLE | WL_SOCKET_CLOSED))
+ new_filt_read = true;
+ if (old_events & WL_SOCKET_WRITEABLE)
+ old_filt_write = true;
+ if (event->events & WL_SOCKET_WRITEABLE)
+ new_filt_write = true;
+ if (old_filt_read && !new_filt_read)
+ WaitEventAdjustKqueueAdd(&k_ev[count++], EVFILT_READ, EV_DELETE,
+ event);
+ else if (!old_filt_read && new_filt_read)
+ WaitEventAdjustKqueueAdd(&k_ev[count++], EVFILT_READ, EV_ADD,
+ event);
+ if (old_filt_write && !new_filt_write)
+ WaitEventAdjustKqueueAdd(&k_ev[count++], EVFILT_WRITE, EV_DELETE,
+ event);
+ else if (!old_filt_write && new_filt_write)
+ WaitEventAdjustKqueueAdd(&k_ev[count++], EVFILT_WRITE, EV_ADD,
+ event);
+ }
+
+ /* For WL_SOCKET_READ -> WL_SOCKET_CLOSED, no change needed. */
+ if (count == 0)
+ return;
+
+ Assert(count <= 2);
+
+ rc = kevent(set->kqueue_fd, &k_ev[0], count, NULL, 0, NULL);
+
+ /*
+ * When adding the postmaster's pid, we have to consider that it might
+ * already have exited and perhaps even been replaced by another process
+ * with the same pid. If so, we have to defer reporting this as an event
+ * until the next call to WaitEventSetWaitBlock().
+ */
+
+ if (rc < 0)
+ {
+ if (event->events == WL_POSTMASTER_DEATH &&
+ (errno == ESRCH || errno == EACCES))
+ set->report_postmaster_not_running = true;
+ else
+ ereport(ERROR,
+ (errcode_for_socket_access(),
+ errmsg("%s() failed: %m",
+ "kevent")));
+ }
+ else if (event->events == WL_POSTMASTER_DEATH &&
+ PostmasterPid != getppid() &&
+ !PostmasterIsAlive())
+ {
+ /*
+ * The extra PostmasterIsAliveInternal() check prevents false alarms
+ * on systems that give a different value for getppid() while being
+ * traced by a debugger.
+ */
+ set->report_postmaster_not_running = true;
+ }
+}
+
+#endif
+
+#if defined(WAIT_USE_WIN32)
+static void
+WaitEventAdjustWin32(WaitEventSet *set, WaitEvent *event)
+{
+ HANDLE *handle = &set->handles[event->pos + 1];
+
+ if (event->events == WL_LATCH_SET)
+ {
+ Assert(set->latch != NULL);
+ *handle = set->latch->event;
+ }
+ else if (event->events == WL_POSTMASTER_DEATH)
+ {
+ *handle = PostmasterHandle;
+ }
+ else
+ {
+ int flags = FD_CLOSE; /* always check for errors/EOF */
+
+ if (event->events & WL_SOCKET_READABLE)
+ flags |= FD_READ;
+ if (event->events & WL_SOCKET_WRITEABLE)
+ flags |= FD_WRITE;
+ if (event->events & WL_SOCKET_CONNECTED)
+ flags |= FD_CONNECT;
+ if (event->events & WL_SOCKET_ACCEPT)
+ flags |= FD_ACCEPT;
+
+ if (*handle == WSA_INVALID_EVENT)
+ {
+ *handle = WSACreateEvent();
+ if (*handle == WSA_INVALID_EVENT)
+ elog(ERROR, "failed to create event for socket: error code %d",
+ WSAGetLastError());
+ }
+ if (WSAEventSelect(event->fd, *handle, flags) != 0)
+ elog(ERROR, "failed to set up event for socket: error code %d",
+ WSAGetLastError());
+
+ Assert(event->fd != PGINVALID_SOCKET);
+ }
+}
+#endif
+
+/*
+ * Wait for events added to the set to happen, or until the timeout is
+ * reached. At most nevents occurred events are returned.
+ *
+ * If timeout = -1, block until an event occurs; if 0, check sockets for
+ * readiness, but don't block; if > 0, block for at most timeout milliseconds.
+ *
+ * Returns the number of events occurred, or 0 if the timeout was reached.
+ *
+ * Returned events will have the fd, pos, user_data fields set to the
+ * values associated with the registered event.
+ */
+int
+WaitEventSetWait(WaitEventSet *set, long timeout,
+ WaitEvent *occurred_events, int nevents,
+ uint32 wait_event_info)
+{
+ 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;
+}
+
+
+#if defined(WAIT_USE_EPOLL)
+
+/*
+ * Wait using linux's epoll_wait(2).
+ *
+ * This is the preferable wait method, as several readiness notifications are
+ * delivered, without having to iterate through all of set->events. The return
+ * epoll_event struct contain a pointer to our events, making association
+ * easy.
+ */
+static inline int
+WaitEventSetWaitBlock(WaitEventSet *set, int cur_timeout,
+ WaitEvent *occurred_events, int nevents)
+{
+ int returned_events = 0;
+ int rc;
+ WaitEvent *cur_event;
+ struct epoll_event *cur_epoll_event;
+
+ /* Sleep */
+ rc = epoll_wait(set->epoll_fd, set->epoll_ret_events,
+ Min(nevents, set->nevents_space), cur_timeout);
+
+ /* Check return code */
+ if (rc < 0)
+ {
+ /* EINTR is okay, otherwise complain */
+ if (errno != EINTR)
+ {
+ waiting = false;
+ ereport(ERROR,
+ (errcode_for_socket_access(),
+ errmsg("%s() failed: %m",
+ "epoll_wait")));
+ }
+ return 0;
+ }
+ else if (rc == 0)
+ {
+ /* timeout exceeded */
+ return -1;
+ }
+
+ /*
+ * At least one event occurred, iterate over the returned epoll events
+ * until they're either all processed, or we've returned all the events
+ * the caller desired.
+ */
+ for (cur_epoll_event = set->epoll_ret_events;
+ cur_epoll_event < (set->epoll_ret_events + rc) &&
+ returned_events < nevents;
+ cur_epoll_event++)
+ {
+ /* epoll's data pointer is set to the associated WaitEvent */
+ cur_event = (WaitEvent *) cur_epoll_event->data.ptr;
+
+ occurred_events->pos = cur_event->pos;
+ occurred_events->user_data = cur_event->user_data;
+ occurred_events->events = 0;
+
+ if (cur_event->events == WL_LATCH_SET &&
+ cur_epoll_event->events & (EPOLLIN | EPOLLERR | EPOLLHUP))
+ {
+ /* Drain the signalfd. */
+ drain();
+
+ if (set->latch && set->latch->maybe_sleeping && set->latch->is_set)
+ {
+ occurred_events->fd = PGINVALID_SOCKET;
+ occurred_events->events = WL_LATCH_SET;
+ occurred_events++;
+ returned_events++;
+ }
+ }
+ else if (cur_event->events == WL_POSTMASTER_DEATH &&
+ cur_epoll_event->events & (EPOLLIN | EPOLLERR | EPOLLHUP))
+ {
+ /*
+ * We expect an EPOLLHUP when the remote end is closed, but
+ * because we don't expect the pipe to become readable or to have
+ * any errors either, treat those cases as postmaster death, too.
+ *
+ * Be paranoid about a spurious event signaling the postmaster as
+ * being dead. There have been reports about that happening with
+ * older primitives (select(2) to be specific), and a spurious
+ * WL_POSTMASTER_DEATH event would be painful. Re-checking doesn't
+ * cost much.
+ */
+ if (!PostmasterIsAliveInternal())
+ {
+ if (set->exit_on_postmaster_death)
+ proc_exit(1);
+ occurred_events->fd = PGINVALID_SOCKET;
+ occurred_events->events = WL_POSTMASTER_DEATH;
+ occurred_events++;
+ returned_events++;
+ }
+ }
+ else if (cur_event->events & (WL_SOCKET_READABLE |
+ WL_SOCKET_WRITEABLE |
+ WL_SOCKET_CLOSED))
+ {
+ Assert(cur_event->fd != PGINVALID_SOCKET);
+
+ if ((cur_event->events & WL_SOCKET_READABLE) &&
+ (cur_epoll_event->events & (EPOLLIN | EPOLLERR | EPOLLHUP)))
+ {
+ /* data available in socket, or EOF */
+ occurred_events->events |= WL_SOCKET_READABLE;
+ }
+
+ if ((cur_event->events & WL_SOCKET_WRITEABLE) &&
+ (cur_epoll_event->events & (EPOLLOUT | EPOLLERR | EPOLLHUP)))
+ {
+ /* writable, or EOF */
+ occurred_events->events |= WL_SOCKET_WRITEABLE;
+ }
+
+ if ((cur_event->events & WL_SOCKET_CLOSED) &&
+ (cur_epoll_event->events & (EPOLLRDHUP | EPOLLERR | EPOLLHUP)))
+ {
+ /* remote peer shut down, or error */
+ occurred_events->events |= WL_SOCKET_CLOSED;
+ }
+
+ if (occurred_events->events != 0)
+ {
+ occurred_events->fd = cur_event->fd;
+ occurred_events++;
+ returned_events++;
+ }
+ }
+ }
+
+ return returned_events;
+}
+
+#elif defined(WAIT_USE_KQUEUE)
+
+/*
+ * Wait using kevent(2) on BSD-family systems and macOS.
+ *
+ * For now this mirrors the epoll code, but in future it could modify the fd
+ * set in the same call to kevent as it uses for waiting instead of doing that
+ * with separate system calls.
+ */
+static int
+WaitEventSetWaitBlock(WaitEventSet *set, int cur_timeout,
+ WaitEvent *occurred_events, int nevents)
+{
+ int returned_events = 0;
+ int rc;
+ WaitEvent *cur_event;
+ struct kevent *cur_kqueue_event;
+ struct timespec timeout;
+ struct timespec *timeout_p;
+
+ if (cur_timeout < 0)
+ timeout_p = NULL;
+ else
+ {
+ timeout.tv_sec = cur_timeout / 1000;
+ timeout.tv_nsec = (cur_timeout % 1000) * 1000000;
+ timeout_p = &timeout;
+ }
+
+ /*
+ * Report postmaster events discovered by WaitEventAdjustKqueue() or an
+ * earlier call to WaitEventSetWait().
+ */
+ if (unlikely(set->report_postmaster_not_running))
+ {
+ if (set->exit_on_postmaster_death)
+ proc_exit(1);
+ occurred_events->fd = PGINVALID_SOCKET;
+ occurred_events->events = WL_POSTMASTER_DEATH;
+ return 1;
+ }
+
+ /* Sleep */
+ rc = kevent(set->kqueue_fd, NULL, 0,
+ set->kqueue_ret_events,
+ Min(nevents, set->nevents_space),
+ timeout_p);
+
+ /* Check return code */
+ if (rc < 0)
+ {
+ /* EINTR is okay, otherwise complain */
+ if (errno != EINTR)
+ {
+ waiting = false;
+ ereport(ERROR,
+ (errcode_for_socket_access(),
+ errmsg("%s() failed: %m",
+ "kevent")));
+ }
+ return 0;
+ }
+ else if (rc == 0)
+ {
+ /* timeout exceeded */
+ return -1;
+ }
+
+ /*
+ * At least one event occurred, iterate over the returned kqueue events
+ * until they're either all processed, or we've returned all the events
+ * the caller desired.
+ */
+ for (cur_kqueue_event = set->kqueue_ret_events;
+ cur_kqueue_event < (set->kqueue_ret_events + rc) &&
+ returned_events < nevents;
+ cur_kqueue_event++)
+ {
+ /* kevent's udata points to the associated WaitEvent */
+ cur_event = AccessWaitEvent(cur_kqueue_event);
+
+ occurred_events->pos = cur_event->pos;
+ occurred_events->user_data = cur_event->user_data;
+ occurred_events->events = 0;
+
+ if (cur_event->events == WL_LATCH_SET &&
+ cur_kqueue_event->filter == EVFILT_SIGNAL)
+ {
+ if (set->latch && set->latch->maybe_sleeping && set->latch->is_set)
+ {
+ occurred_events->fd = PGINVALID_SOCKET;
+ occurred_events->events = WL_LATCH_SET;
+ occurred_events++;
+ returned_events++;
+ }
+ }
+ else if (cur_event->events == WL_POSTMASTER_DEATH &&
+ cur_kqueue_event->filter == EVFILT_PROC &&
+ (cur_kqueue_event->fflags & NOTE_EXIT) != 0)
+ {
+ /*
+ * The kernel will tell this kqueue object only once about the
+ * exit of the postmaster, so let's remember that for next time so
+ * that we provide level-triggered semantics.
+ */
+ set->report_postmaster_not_running = true;
+
+ if (set->exit_on_postmaster_death)
+ proc_exit(1);
+ occurred_events->fd = PGINVALID_SOCKET;
+ occurred_events->events = WL_POSTMASTER_DEATH;
+ occurred_events++;
+ returned_events++;
+ }
+ else if (cur_event->events & (WL_SOCKET_READABLE |
+ WL_SOCKET_WRITEABLE |
+ WL_SOCKET_CLOSED))
+ {
+ Assert(cur_event->fd >= 0);
+
+ if ((cur_event->events & WL_SOCKET_READABLE) &&
+ (cur_kqueue_event->filter == EVFILT_READ))
+ {
+ /* readable, or EOF */
+ occurred_events->events |= WL_SOCKET_READABLE;
+ }
+
+ if ((cur_event->events & WL_SOCKET_CLOSED) &&
+ (cur_kqueue_event->filter == EVFILT_READ) &&
+ (cur_kqueue_event->flags & EV_EOF))
+ {
+ /* the remote peer has shut down */
+ occurred_events->events |= WL_SOCKET_CLOSED;
+ }
+
+ if ((cur_event->events & WL_SOCKET_WRITEABLE) &&
+ (cur_kqueue_event->filter == EVFILT_WRITE))
+ {
+ /* writable, or EOF */
+ occurred_events->events |= WL_SOCKET_WRITEABLE;
+ }
+
+ if (occurred_events->events != 0)
+ {
+ occurred_events->fd = cur_event->fd;
+ occurred_events++;
+ returned_events++;
+ }
+ }
+ }
+
+ return returned_events;
+}
+
+#elif defined(WAIT_USE_POLL)
+
+/*
+ * Wait using poll(2).
+ *
+ * This allows to receive readiness notifications for several events at once,
+ * but requires iterating through all of set->pollfds.
+ */
+static inline int
+WaitEventSetWaitBlock(WaitEventSet *set, int cur_timeout,
+ WaitEvent *occurred_events, int nevents)
+{
+ int returned_events = 0;
+ int rc;
+ WaitEvent *cur_event;
+ struct pollfd *cur_pollfd;
+
+ /* Sleep */
+ rc = poll(set->pollfds, set->nevents, (int) cur_timeout);
+
+ /* Check return code */
+ if (rc < 0)
+ {
+ /* EINTR is okay, otherwise complain */
+ if (errno != EINTR)
+ {
+ waiting = false;
+ ereport(ERROR,
+ (errcode_for_socket_access(),
+ errmsg("%s() failed: %m",
+ "poll")));
+ }
+ return 0;
+ }
+ else if (rc == 0)
+ {
+ /* timeout exceeded */
+ return -1;
+ }
+
+ for (cur_event = set->events, cur_pollfd = set->pollfds;
+ cur_event < (set->events + set->nevents) &&
+ returned_events < nevents;
+ cur_event++, cur_pollfd++)
+ {
+ /* no activity on this FD, skip */
+ if (cur_pollfd->revents == 0)
+ continue;
+
+ occurred_events->pos = cur_event->pos;
+ occurred_events->user_data = cur_event->user_data;
+ occurred_events->events = 0;
+
+ if (cur_event->events == WL_LATCH_SET &&
+ (cur_pollfd->revents & (POLLIN | POLLHUP | POLLERR | POLLNVAL)))
+ {
+ /* There's data in the self-pipe, clear it. */
+ drain();
+
+ if (set->latch && set->latch->maybe_sleeping && set->latch->is_set)
+ {
+ occurred_events->fd = PGINVALID_SOCKET;
+ occurred_events->events = WL_LATCH_SET;
+ occurred_events++;
+ returned_events++;
+ }
+ }
+ else if (cur_event->events == WL_POSTMASTER_DEATH &&
+ (cur_pollfd->revents & (POLLIN | POLLHUP | POLLERR | POLLNVAL)))
+ {
+ /*
+ * We expect an POLLHUP when the remote end is closed, but because
+ * we don't expect the pipe to become readable or to have any
+ * errors either, treat those cases as postmaster death, too.
+ *
+ * Be paranoid about a spurious event signaling the postmaster as
+ * being dead. There have been reports about that happening with
+ * older primitives (select(2) to be specific), and a spurious
+ * WL_POSTMASTER_DEATH event would be painful. Re-checking doesn't
+ * cost much.
+ */
+ if (!PostmasterIsAliveInternal())
+ {
+ if (set->exit_on_postmaster_death)
+ proc_exit(1);
+ occurred_events->fd = PGINVALID_SOCKET;
+ occurred_events->events = WL_POSTMASTER_DEATH;
+ occurred_events++;
+ returned_events++;
+ }
+ }
+ else if (cur_event->events & (WL_SOCKET_READABLE |
+ WL_SOCKET_WRITEABLE |
+ WL_SOCKET_CLOSED))
+ {
+ int errflags = POLLHUP | POLLERR | POLLNVAL;
+
+ Assert(cur_event->fd >= PGINVALID_SOCKET);
+
+ if ((cur_event->events & WL_SOCKET_READABLE) &&
+ (cur_pollfd->revents & (POLLIN | errflags)))
+ {
+ /* data available in socket, or EOF */
+ occurred_events->events |= WL_SOCKET_READABLE;
+ }
+
+ if ((cur_event->events & WL_SOCKET_WRITEABLE) &&
+ (cur_pollfd->revents & (POLLOUT | errflags)))
+ {
+ /* writeable, or EOF */
+ occurred_events->events |= WL_SOCKET_WRITEABLE;
+ }
+
+#ifdef POLLRDHUP
+ if ((cur_event->events & WL_SOCKET_CLOSED) &&
+ (cur_pollfd->revents & (POLLRDHUP | errflags)))
+ {
+ /* remote peer closed, or error */
+ occurred_events->events |= WL_SOCKET_CLOSED;
+ }
+#endif
+
+ if (occurred_events->events != 0)
+ {
+ occurred_events->fd = cur_event->fd;
+ occurred_events++;
+ returned_events++;
+ }
+ }
+ }
+ return returned_events;
+}
+
+#elif defined(WAIT_USE_WIN32)
+
+/*
+ * Wait using Windows' WaitForMultipleObjects(). Each call only "consumes" one
+ * event, so we keep calling until we've filled up our output buffer to match
+ * the behavior of the other implementations.
+ *
+ * https://blogs.msdn.microsoft.com/oldnewthing/20150409-00/?p=44273
+ */
+static inline int
+WaitEventSetWaitBlock(WaitEventSet *set, int cur_timeout,
+ WaitEvent *occurred_events, int nevents)
+{
+ int returned_events = 0;
+ DWORD rc;
+ WaitEvent *cur_event;
+
+ /* Reset any wait events that need it */
+ for (cur_event = set->events;
+ cur_event < (set->events + set->nevents);
+ cur_event++)
+ {
+ if (cur_event->reset)
+ {
+ WaitEventAdjustWin32(set, cur_event);
+ cur_event->reset = false;
+ }
+
+ /*
+ * We associate the socket with a new event handle for each
+ * WaitEventSet. FD_CLOSE is only generated once if the other end
+ * closes gracefully. Therefore we might miss the FD_CLOSE
+ * notification, if it was delivered to another event after we stopped
+ * waiting for it. Close that race by peeking for EOF after setting
+ * up this handle to receive notifications, and before entering the
+ * sleep.
+ *
+ * XXX If we had one event handle for the lifetime of a socket, we
+ * wouldn't need this.
+ */
+ if (cur_event->events & WL_SOCKET_READABLE)
+ {
+ char c;
+ WSABUF buf;
+ DWORD received;
+ DWORD flags;
+
+ buf.buf = &c;
+ buf.len = 1;
+ flags = MSG_PEEK;
+ if (WSARecv(cur_event->fd, &buf, 1, &received, &flags, NULL, NULL) == 0)
+ {
+ occurred_events->pos = cur_event->pos;
+ occurred_events->user_data = cur_event->user_data;
+ occurred_events->events = WL_SOCKET_READABLE;
+ occurred_events->fd = cur_event->fd;
+ return 1;
+ }
+ }
+
+ /*
+ * Windows does not guarantee to log an FD_WRITE network event
+ * indicating that more data can be sent unless the previous send()
+ * failed with WSAEWOULDBLOCK. While our caller might well have made
+ * such a call, we cannot assume that here. Therefore, if waiting for
+ * write-ready, force the issue by doing a dummy send(). If the dummy
+ * send() succeeds, assume that the socket is in fact write-ready, and
+ * return immediately. Also, if it fails with something other than
+ * WSAEWOULDBLOCK, return a write-ready indication to let our caller
+ * deal with the error condition.
+ */
+ if (cur_event->events & WL_SOCKET_WRITEABLE)
+ {
+ char c;
+ WSABUF buf;
+ DWORD sent;
+ int r;
+
+ buf.buf = &c;
+ buf.len = 0;
+
+ r = WSASend(cur_event->fd, &buf, 1, &sent, 0, NULL, NULL);
+ if (r == 0 || WSAGetLastError() != WSAEWOULDBLOCK)
+ {
+ occurred_events->pos = cur_event->pos;
+ occurred_events->user_data = cur_event->user_data;
+ occurred_events->events = WL_SOCKET_WRITEABLE;
+ occurred_events->fd = cur_event->fd;
+ return 1;
+ }
+ }
+ }
+
+ /*
+ * Sleep.
+ *
+ * Need to wait for ->nevents + 1, because signal handle is in [0].
+ */
+ rc = WaitForMultipleObjects(set->nevents + 1, set->handles, FALSE,
+ cur_timeout);
+
+ /* Check return code */
+ if (rc == WAIT_FAILED)
+ elog(ERROR, "WaitForMultipleObjects() failed: error code %lu",
+ GetLastError());
+ else if (rc == WAIT_TIMEOUT)
+ {
+ /* timeout exceeded */
+ return -1;
+ }
+
+ if (rc == WAIT_OBJECT_0)
+ {
+ /* Service newly-arrived signals */
+ pgwin32_dispatch_queued_signals();
+ return 0; /* retry */
+ }
+
+ /*
+ * With an offset of one, due to the always present pgwin32_signal_event,
+ * the handle offset directly corresponds to a wait event.
+ */
+ cur_event = (WaitEvent *) &set->events[rc - WAIT_OBJECT_0 - 1];
+
+ for (;;)
+ {
+ int next_pos;
+ int count;
+
+ occurred_events->pos = cur_event->pos;
+ occurred_events->user_data = cur_event->user_data;
+ occurred_events->events = 0;
+
+ if (cur_event->events == WL_LATCH_SET)
+ {
+ /*
+ * We cannot use set->latch->event to reset the fired event if we
+ * aren't waiting on this latch now.
+ */
+ if (!ResetEvent(set->handles[cur_event->pos + 1]))
+ elog(ERROR, "ResetEvent failed: error code %lu", GetLastError());
+
+ if (set->latch && set->latch->maybe_sleeping && set->latch->is_set)
+ {
+ occurred_events->fd = PGINVALID_SOCKET;
+ occurred_events->events = WL_LATCH_SET;
+ occurred_events++;
+ returned_events++;
+ }
+ }
+ else if (cur_event->events == WL_POSTMASTER_DEATH)
+ {
+ /*
+ * Postmaster apparently died. Since the consequences of falsely
+ * returning WL_POSTMASTER_DEATH could be pretty unpleasant, we
+ * take the trouble to positively verify this with
+ * PostmasterIsAlive(), even though there is no known reason to
+ * think that the event could be falsely set on Windows.
+ */
+ if (!PostmasterIsAliveInternal())
+ {
+ if (set->exit_on_postmaster_death)
+ proc_exit(1);
+ occurred_events->fd = PGINVALID_SOCKET;
+ occurred_events->events = WL_POSTMASTER_DEATH;
+ occurred_events++;
+ returned_events++;
+ }
+ }
+ else if (cur_event->events & WL_SOCKET_MASK)
+ {
+ WSANETWORKEVENTS resEvents;
+ HANDLE handle = set->handles[cur_event->pos + 1];
+
+ Assert(cur_event->fd);
+
+ occurred_events->fd = cur_event->fd;
+
+ ZeroMemory(&resEvents, sizeof(resEvents));
+ if (WSAEnumNetworkEvents(cur_event->fd, handle, &resEvents) != 0)
+ elog(ERROR, "failed to enumerate network events: error code %d",
+ WSAGetLastError());
+ if ((cur_event->events & WL_SOCKET_READABLE) &&
+ (resEvents.lNetworkEvents & FD_READ))
+ {
+ /* data available in socket */
+ occurred_events->events |= WL_SOCKET_READABLE;
+
+ /*------
+ * WaitForMultipleObjects doesn't guarantee that a read event
+ * will be returned if the latch is set at the same time. Even
+ * if it did, the caller might drop that event expecting it to
+ * reoccur on next call. So, we must force the event to be
+ * reset if this WaitEventSet is used again in order to avoid
+ * an indefinite hang.
+ *
+ * Refer
+ * https://msdn.microsoft.com/en-us/library/windows/desktop/ms741576(v=vs.85).aspx
+ * for the behavior of socket events.
+ *------
+ */
+ cur_event->reset = true;
+ }
+ if ((cur_event->events & WL_SOCKET_WRITEABLE) &&
+ (resEvents.lNetworkEvents & FD_WRITE))
+ {
+ /* writeable */
+ occurred_events->events |= WL_SOCKET_WRITEABLE;
+ }
+ if ((cur_event->events & WL_SOCKET_CONNECTED) &&
+ (resEvents.lNetworkEvents & FD_CONNECT))
+ {
+ /* connected */
+ occurred_events->events |= WL_SOCKET_CONNECTED;
+ }
+ if ((cur_event->events & WL_SOCKET_ACCEPT) &&
+ (resEvents.lNetworkEvents & FD_ACCEPT))
+ {
+ /* incoming connection could be accepted */
+ occurred_events->events |= WL_SOCKET_ACCEPT;
+ }
+ if (resEvents.lNetworkEvents & FD_CLOSE)
+ {
+ /* EOF/error, so signal all caller-requested socket flags */
+ occurred_events->events |= (cur_event->events & WL_SOCKET_MASK);
+ }
+
+ if (occurred_events->events != 0)
+ {
+ occurred_events++;
+ returned_events++;
+ }
+ }
+
+ /* Is the output buffer full? */
+ if (returned_events == nevents)
+ break;
+
+ /* Have we run out of possible events? */
+ next_pos = cur_event->pos + 1;
+ if (next_pos == set->nevents)
+ break;
+
+ /*
+ * Poll the rest of the event handles in the array starting at
+ * next_pos being careful to skip over the initial signal handle too.
+ * This time we use a zero timeout.
+ */
+ count = set->nevents - next_pos;
+ rc = WaitForMultipleObjects(count,
+ set->handles + 1 + next_pos,
+ false,
+ 0);
+
+ /*
+ * We don't distinguish between errors and WAIT_TIMEOUT here because
+ * we already have events to report.
+ */
+ if (rc < WAIT_OBJECT_0 || rc >= WAIT_OBJECT_0 + count)
+ break;
+
+ /* We have another event to decode. */
+ cur_event = &set->events[next_pos + (rc - WAIT_OBJECT_0)];
+ }
+
+ return returned_events;
+}
+#endif
+
+/*
+ * Return whether the current build options can report WL_SOCKET_CLOSED.
+ */
+bool
+WaitEventSetCanReportClosed(void)
+{
+#if (defined(WAIT_USE_POLL) && defined(POLLRDHUP)) || \
+ defined(WAIT_USE_EPOLL) || \
+ defined(WAIT_USE_KQUEUE)
+ return true;
+#else
+ return false;
+#endif
+}
+
+/*
+ * Get the number of wait events registered in a given WaitEventSet.
+ */
+int
+GetNumRegisteredWaitEvents(WaitEventSet *set)
+{
+ return set->nevents;
+}
+
+#if defined(WAIT_USE_SELF_PIPE)
+
+/*
+ * SetLatch uses SIGURG to wake up the process waiting on the latch.
+ *
+ * Wake up WaitLatch, if we're waiting.
+ */
+static void
+latch_sigurg_handler(SIGNAL_ARGS)
+{
+ if (waiting)
+ sendSelfPipeByte();
+}
+
+/* Send one byte to the self-pipe, to wake up WaitLatch */
+static void
+sendSelfPipeByte(void)
+{
+ int rc;
+ char dummy = 0;
+
+retry:
+ rc = write(selfpipe_writefd, &dummy, 1);
+ if (rc < 0)
+ {
+ /* If interrupted by signal, just retry */
+ if (errno == EINTR)
+ goto retry;
+
+ /*
+ * If the pipe is full, we don't need to retry, the data that's there
+ * already is enough to wake up WaitLatch.
+ */
+ if (errno == EAGAIN || errno == EWOULDBLOCK)
+ return;
+
+ /*
+ * Oops, the write() failed for some other reason. We might be in a
+ * signal handler, so it's not safe to elog(). We have no choice but
+ * silently ignore the error.
+ */
+ return;
+ }
+}
+
+#endif
+
+#if defined(WAIT_USE_SELF_PIPE) || defined(WAIT_USE_SIGNALFD)
+
+/*
+ * Read all available data from self-pipe or signalfd.
+ *
+ * Note: this is only called when waiting = true. If it fails and doesn't
+ * return, it must reset that flag first (though ideally, this will never
+ * happen).
+ */
+static void
+drain(void)
+{
+ char buf[1024];
+ int rc;
+ int fd;
+
+#ifdef WAIT_USE_SELF_PIPE
+ fd = selfpipe_readfd;
+#else
+ fd = signal_fd;
+#endif
+
+ for (;;)
+ {
+ rc = read(fd, buf, sizeof(buf));
+ if (rc < 0)
+ {
+ if (errno == EAGAIN || errno == EWOULDBLOCK)
+ break; /* the descriptor is empty */
+ else if (errno == EINTR)
+ continue; /* retry */
+ else
+ {
+ waiting = false;
+#ifdef WAIT_USE_SELF_PIPE
+ elog(ERROR, "read() on self-pipe failed: %m");
+#else
+ elog(ERROR, "read() on signalfd failed: %m");
+#endif
+ }
+ }
+ else if (rc == 0)
+ {
+ waiting = false;
+#ifdef WAIT_USE_SELF_PIPE
+ elog(ERROR, "unexpected EOF on self-pipe");
+#else
+ elog(ERROR, "unexpected EOF on signalfd");
+#endif
+ }
+ else if (rc < sizeof(buf))
+ {
+ /* we successfully drained the pipe; no need to read() again */
+ break;
+ }
+ /* else buffer wasn't big enough, so read again */
+ }
+}
+
+#endif
+
+static void
+ResOwnerReleaseWaitEventSet(Datum res)
+{
+ WaitEventSet *set = (WaitEventSet *) DatumGetPointer(res);
+
+ Assert(set->owner != NULL);
+ set->owner = NULL;
+ FreeWaitEventSet(set);
+}
+
+#ifndef WIN32
+/*
+ * Wake up my process if it's currently sleeping in WaitEventSetWaitBlock()
+ *
+ * NB: be sure to save and restore errno around it. (That's standard practice
+ * in most signal handlers, of course, but we used to omit it in handlers that
+ * only set a flag.) XXX
+ *
+ * NB: this function is called from critical sections and signal handlers so
+ * throwing an error is not a good idea.
+ *
+ * On Windows, Latch uses SetEvent directly and this is not used.
+ */
+void
+WakeupMyProc(void)
+{
+#if defined(WAIT_USE_SELF_PIPE)
+ if (waiting)
+ sendSelfPipeByte();
+#else
+ if (waiting)
+ kill(MyProcPid, SIGURG);
+#endif
+}
+
+/* Similar to WakeupMyProc, but wake up another process */
+void
+WakeupOtherProc(int pid)
+{
+ kill(pid, SIGURG);
+}
+#endif
#endif
/* Initialize process-local latch support */
- InitializeLatchSupport();
+ InitializeWaitEventSupport();
InitProcessLocalLatch();
InitializeLatchWaitSet();
InitProcessGlobals();
/* Initialize process-local latch support */
- InitializeLatchSupport();
+ InitializeWaitEventSupport();
InitProcessLocalLatch();
InitializeLatchWaitSet();
* use of any generic handler.
*
*
- * WaitEventSets allow to wait for latches being set and additional events -
- * postmaster dying and socket readiness of several sockets currently - at the
- * same time. On many platforms using a long lived event set is more
- * efficient than using WaitLatch or WaitLatchOrSocket.
+ * See also WaitEventSets in waiteventset.h. They allow to wait for latches
+ * being set and additional events - postmaster dying and socket readiness of
+ * several sockets currently - at the same time. On many platforms using a
+ * long lived event set is more efficient than using WaitLatch or
+ * WaitLatchOrSocket.
*
*
* Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
#include <signal.h>
-#include "utils/resowner.h"
+#include "storage/waiteventset.h" /* for WL_* arguments to WaitLatch */
/*
* Latch structure should be treated as opaque and only accessed through
#endif
} Latch;
-/*
- * Bitmasks for events that may wake-up WaitLatch(), WaitLatchOrSocket(), or
- * WaitEventSetWait().
- */
-#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)
-#ifdef WIN32
-#define WL_SOCKET_CONNECTED (1 << 6)
-#else
-/* avoid having to deal with case on platforms not requiring it */
-#define WL_SOCKET_CONNECTED WL_SOCKET_WRITEABLE
-#endif
-#define WL_SOCKET_CLOSED (1 << 7)
-#ifdef WIN32
-#define WL_SOCKET_ACCEPT (1 << 8)
-#else
-/* avoid having to deal with case on platforms not requiring it */
-#define WL_SOCKET_ACCEPT WL_SOCKET_READABLE
-#endif
-#define WL_SOCKET_MASK (WL_SOCKET_READABLE | \
- WL_SOCKET_WRITEABLE | \
- WL_SOCKET_CONNECTED | \
- WL_SOCKET_ACCEPT | \
- WL_SOCKET_CLOSED)
-
-typedef struct WaitEvent
-{
- int pos; /* position in the event data structure */
- uint32 events; /* triggered events */
- pgsocket fd; /* socket fd associated with event */
- void *user_data; /* pointer provided in AddWaitEventToSet */
-#ifdef WIN32
- bool reset; /* Is reset of the event required? */
-#endif
-} WaitEvent;
-
-/* forward declaration to avoid exposing latch.c implementation details */
-typedef struct WaitEventSet WaitEventSet;
-
/*
* prototypes for functions in latch.c
*/
-extern void InitializeLatchSupport(void);
extern void InitLatch(Latch *latch);
extern void InitSharedLatch(Latch *latch);
extern void OwnLatch(Latch *latch);
extern void SetLatch(Latch *latch);
extern void ResetLatch(Latch *latch);
-extern WaitEventSet *CreateWaitEventSet(ResourceOwner resowner, int nevents);
-extern void FreeWaitEventSet(WaitEventSet *set);
-extern void FreeWaitEventSetAfterFork(WaitEventSet *set);
-extern int AddWaitEventToSet(WaitEventSet *set, uint32 events, pgsocket fd,
- Latch *latch, void *user_data);
-extern void ModifyWaitEvent(WaitEventSet *set, int pos, uint32 events, Latch *latch);
-
-extern int WaitEventSetWait(WaitEventSet *set, long timeout,
- WaitEvent *occurred_events, int nevents,
- uint32 wait_event_info);
extern int WaitLatch(Latch *latch, int wakeEvents, long timeout,
uint32 wait_event_info);
extern int WaitLatchOrSocket(Latch *latch, int wakeEvents,
pgsocket sock, long timeout, uint32 wait_event_info);
extern void InitializeLatchWaitSet(void);
-extern int GetNumRegisteredWaitEvents(WaitEventSet *set);
-extern bool WaitEventSetCanReportClosed(void);
#endif /* LATCH_H */
--- /dev/null
+/*-------------------------------------------------------------------------
+ *
+ * waiteventset.h
+ * ppoll() / pselect() like interface for waiting for events
+ *
+ * WaitEventSets allow to wait for latches being set and additional events -
+ * postmaster dying and socket readiness of several sockets currently - at the
+ * same time. On many platforms using a long lived event set is more
+ * efficient than using WaitLatch or WaitLatchOrSocket.
+ *
+ * WaitEventSetWait includes a provision for timeouts (which should be avoided
+ * when possible, as they incur extra overhead) and a provision for postmaster
+ * child processes to wake up immediately on postmaster death. See
+ * storage/ipc/waiteventset.c for detailed specifications for the exported
+ * functions.
+ *
+ *
+ * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/storage/waiteventset.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef WAITEVENTSET_H
+#define WAITEVENTSET_H
+
+#include "utils/resowner.h"
+
+/*
+ * Bitmasks for events that may wake-up WaitLatch(), WaitLatchOrSocket(), or
+ * WaitEventSetWait().
+ */
+#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)
+#ifdef WIN32
+#define WL_SOCKET_CONNECTED (1 << 6)
+#else
+/* avoid having to deal with case on platforms not requiring it */
+#define WL_SOCKET_CONNECTED WL_SOCKET_WRITEABLE
+#endif
+#define WL_SOCKET_CLOSED (1 << 7)
+#ifdef WIN32
+#define WL_SOCKET_ACCEPT (1 << 8)
+#else
+/* avoid having to deal with case on platforms not requiring it */
+#define WL_SOCKET_ACCEPT WL_SOCKET_READABLE
+#endif
+#define WL_SOCKET_MASK (WL_SOCKET_READABLE | \
+ WL_SOCKET_WRITEABLE | \
+ WL_SOCKET_CONNECTED | \
+ WL_SOCKET_ACCEPT | \
+ WL_SOCKET_CLOSED)
+
+typedef struct WaitEvent
+{
+ int pos; /* position in the event data structure */
+ uint32 events; /* triggered events */
+ pgsocket fd; /* socket fd associated with event */
+ void *user_data; /* pointer provided in AddWaitEventToSet */
+#ifdef WIN32
+ bool reset; /* Is reset of the event required? */
+#endif
+} WaitEvent;
+
+/* forward declarations to avoid exposing waiteventset.c implementation details */
+typedef struct WaitEventSet WaitEventSet;
+
+typedef struct Latch Latch;
+
+/*
+ * prototypes for functions in waiteventset.c
+ */
+extern void InitializeWaitEventSupport(void);
+
+extern WaitEventSet *CreateWaitEventSet(ResourceOwner resowner, int nevents);
+extern void FreeWaitEventSet(WaitEventSet *set);
+extern void FreeWaitEventSetAfterFork(WaitEventSet *set);
+extern int AddWaitEventToSet(WaitEventSet *set, uint32 events, pgsocket fd,
+ Latch *latch, void *user_data);
+extern void ModifyWaitEvent(WaitEventSet *set, int pos, uint32 events, Latch *latch);
+extern int WaitEventSetWait(WaitEventSet *set, long timeout,
+ WaitEvent *occurred_events, int nevents,
+ uint32 wait_event_info);
+extern int GetNumRegisteredWaitEvents(WaitEventSet *set);
+extern bool WaitEventSetCanReportClosed(void);
+
+#ifndef WIN32
+extern void WakeupMyProc(void);
+extern void WakeupOtherProc(int pid);
+#endif
+
+#endif /* WAITEVENTSET_H */
projects / thirdparty / postgresql.git / commitdiff
