mirror of https://github.com/postgres/postgres
Previously latches for windows and unix had been implemented in different files. A later patch introduce an expanded wait infrastructure, keeping the implementation separate would introduce too much duplication. This basically just moves the functions, without too much change. The reason to keep this separate is that it allows blame to continue working a little less badly; and to make review a tiny bit easier. Discussion: 20160114143931.GG10941@awork2.anarazel.depull/11/head
Andres Freund
10 years ago
parent
326d73c86f
commit
72e2d21c12
@ -1,5 +1,4 @@ |
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/dynloader.c |
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/pg_latch.c |
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/pg_sema.c |
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/pg_shmem.c |
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/tas.s |
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|
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@ -1,349 +0,0 @@ |
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/*-------------------------------------------------------------------------
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* |
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* win32_latch.c |
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* Routines for inter-process latches |
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* |
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* See unix_latch.c for header comments for the exported functions; |
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* the API presented here is supposed to be the same as there. |
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* |
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* The Windows implementation uses Windows events that are inherited by |
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* all postmaster child processes. |
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* |
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* Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group |
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* Portions Copyright (c) 1994, Regents of the University of California |
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* |
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* IDENTIFICATION |
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* src/backend/port/win32_latch.c |
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* |
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*------------------------------------------------------------------------- |
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*/ |
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#include "postgres.h" |
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#include <fcntl.h> |
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#include <limits.h> |
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#include <signal.h> |
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#include <unistd.h> |
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#include "miscadmin.h" |
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#include "portability/instr_time.h" |
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#include "postmaster/postmaster.h" |
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#include "storage/barrier.h" |
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#include "storage/latch.h" |
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#include "storage/pmsignal.h" |
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#include "storage/shmem.h" |
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void |
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InitializeLatchSupport(void) |
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{ |
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/* currently, nothing to do here for Windows */ |
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} |
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void |
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InitLatch(volatile Latch *latch) |
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{ |
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latch->is_set = false; |
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latch->owner_pid = MyProcPid; |
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latch->is_shared = false; |
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latch->event = CreateEvent(NULL, TRUE, FALSE, NULL); |
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if (latch->event == NULL) |
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elog(ERROR, "CreateEvent failed: error code %lu", GetLastError()); |
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} |
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|
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void |
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InitSharedLatch(volatile Latch *latch) |
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{ |
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SECURITY_ATTRIBUTES sa; |
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latch->is_set = false; |
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latch->owner_pid = 0; |
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latch->is_shared = true; |
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/*
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* Set up security attributes to specify that the events are inherited. |
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*/ |
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ZeroMemory(&sa, sizeof(sa)); |
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sa.nLength = sizeof(sa); |
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sa.bInheritHandle = TRUE; |
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latch->event = CreateEvent(&sa, TRUE, FALSE, NULL); |
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if (latch->event == NULL) |
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elog(ERROR, "CreateEvent failed: error code %lu", GetLastError()); |
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} |
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void |
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OwnLatch(volatile Latch *latch) |
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{ |
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/* Sanity checks */ |
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Assert(latch->is_shared); |
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if (latch->owner_pid != 0) |
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elog(ERROR, "latch already owned"); |
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latch->owner_pid = MyProcPid; |
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} |
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void |
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DisownLatch(volatile Latch *latch) |
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{ |
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Assert(latch->is_shared); |
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Assert(latch->owner_pid == MyProcPid); |
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latch->owner_pid = 0; |
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} |
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int |
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WaitLatch(volatile Latch *latch, int wakeEvents, long timeout) |
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{ |
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return WaitLatchOrSocket(latch, wakeEvents, PGINVALID_SOCKET, timeout); |
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} |
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int |
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WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock, |
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long timeout) |
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{ |
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DWORD rc; |
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instr_time start_time, |
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cur_time; |
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long cur_timeout; |
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HANDLE events[4]; |
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HANDLE latchevent; |
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HANDLE sockevent = WSA_INVALID_EVENT; |
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int numevents; |
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int result = 0; |
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int pmdeath_eventno = 0; |
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Assert(wakeEvents != 0); /* must have at least one wake event */ |
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/* waiting for socket readiness without a socket indicates a bug */ |
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if (sock == PGINVALID_SOCKET && |
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(wakeEvents & (WL_SOCKET_READABLE | WL_SOCKET_WRITEABLE)) != 0) |
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elog(ERROR, "cannot wait on socket event without a socket"); |
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if ((wakeEvents & WL_LATCH_SET) && latch->owner_pid != MyProcPid) |
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elog(ERROR, "cannot wait on a latch owned by another process"); |
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/*
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* Initialize timeout if requested. We must record the current time so |
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* that we can determine the remaining timeout if WaitForMultipleObjects |
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* is interrupted. |
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*/ |
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if (wakeEvents & WL_TIMEOUT) |
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{ |
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INSTR_TIME_SET_CURRENT(start_time); |
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Assert(timeout >= 0 && timeout <= INT_MAX); |
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cur_timeout = timeout; |
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} |
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else |
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cur_timeout = INFINITE; |
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/*
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* Construct an array of event handles for WaitforMultipleObjects(). |
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* |
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* Note: pgwin32_signal_event should be first to ensure that it will be |
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* reported when multiple events are set. We want to guarantee that |
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* pending signals are serviced. |
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*/ |
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latchevent = latch->event; |
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events[0] = pgwin32_signal_event; |
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events[1] = latchevent; |
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numevents = 2; |
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if (wakeEvents & (WL_SOCKET_READABLE | WL_SOCKET_WRITEABLE)) |
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{ |
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/* Need an event object to represent events on the socket */ |
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int flags = FD_CLOSE; /* always check for errors/EOF */ |
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if (wakeEvents & WL_SOCKET_READABLE) |
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flags |= FD_READ; |
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if (wakeEvents & WL_SOCKET_WRITEABLE) |
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flags |= FD_WRITE; |
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sockevent = WSACreateEvent(); |
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if (sockevent == WSA_INVALID_EVENT) |
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elog(ERROR, "failed to create event for socket: error code %u", |
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WSAGetLastError()); |
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if (WSAEventSelect(sock, sockevent, flags) != 0) |
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elog(ERROR, "failed to set up event for socket: error code %u", |
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WSAGetLastError()); |
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events[numevents++] = sockevent; |
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} |
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if (wakeEvents & WL_POSTMASTER_DEATH) |
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{ |
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pmdeath_eventno = numevents; |
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events[numevents++] = PostmasterHandle; |
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} |
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/* Ensure that signals are serviced even if latch is already set */ |
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pgwin32_dispatch_queued_signals(); |
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do |
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{ |
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/*
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* The comment in unix_latch.c's equivalent to this applies here as |
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* well. At least after mentally replacing self-pipe with windows |
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* event. There's no danger of overflowing, as "Setting an event that |
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* is already set has no effect.". |
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*/ |
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if ((wakeEvents & WL_LATCH_SET) && latch->is_set) |
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{ |
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result |= WL_LATCH_SET; |
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/*
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* Leave loop immediately, avoid blocking again. We don't attempt |
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* to report any other events that might also be satisfied. |
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*/ |
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break; |
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} |
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rc = WaitForMultipleObjects(numevents, events, FALSE, cur_timeout); |
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if (rc == WAIT_FAILED) |
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elog(ERROR, "WaitForMultipleObjects() failed: error code %lu", |
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GetLastError()); |
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else if (rc == WAIT_TIMEOUT) |
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{ |
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result |= WL_TIMEOUT; |
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} |
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else if (rc == WAIT_OBJECT_0) |
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{ |
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/* Service newly-arrived signals */ |
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pgwin32_dispatch_queued_signals(); |
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} |
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else if (rc == WAIT_OBJECT_0 + 1) |
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{ |
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/*
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* Reset the event. We'll re-check the, potentially, set latch on |
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* next iteration of loop, but let's not waste the cycles to |
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* update cur_timeout below. |
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*/ |
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if (!ResetEvent(latchevent)) |
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elog(ERROR, "ResetEvent failed: error code %lu", GetLastError()); |
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continue; |
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} |
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else if ((wakeEvents & (WL_SOCKET_READABLE | WL_SOCKET_WRITEABLE)) && |
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rc == WAIT_OBJECT_0 + 2) /* socket is at event slot 2 */ |
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{ |
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WSANETWORKEVENTS resEvents; |
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ZeroMemory(&resEvents, sizeof(resEvents)); |
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if (WSAEnumNetworkEvents(sock, sockevent, &resEvents) != 0) |
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elog(ERROR, "failed to enumerate network events: error code %u", |
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WSAGetLastError()); |
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if ((wakeEvents & WL_SOCKET_READABLE) && |
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(resEvents.lNetworkEvents & FD_READ)) |
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{ |
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result |= WL_SOCKET_READABLE; |
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} |
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if ((wakeEvents & WL_SOCKET_WRITEABLE) && |
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(resEvents.lNetworkEvents & FD_WRITE)) |
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{ |
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result |= WL_SOCKET_WRITEABLE; |
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} |
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if (resEvents.lNetworkEvents & FD_CLOSE) |
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{ |
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if (wakeEvents & WL_SOCKET_READABLE) |
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result |= WL_SOCKET_READABLE; |
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if (wakeEvents & WL_SOCKET_WRITEABLE) |
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result |= WL_SOCKET_WRITEABLE; |
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} |
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} |
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else if ((wakeEvents & WL_POSTMASTER_DEATH) && |
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rc == WAIT_OBJECT_0 + pmdeath_eventno) |
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{ |
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/*
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* Postmaster apparently died. Since the consequences of falsely |
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* returning WL_POSTMASTER_DEATH could be pretty unpleasant, we |
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* take the trouble to positively verify this with |
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* PostmasterIsAlive(), even though there is no known reason to |
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* think that the event could be falsely set on Windows. |
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*/ |
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if (!PostmasterIsAlive()) |
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result |= WL_POSTMASTER_DEATH; |
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} |
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else |
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elog(ERROR, "unexpected return code from WaitForMultipleObjects(): %lu", rc); |
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/* If we're not done, update cur_timeout for next iteration */ |
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if (result == 0 && (wakeEvents & WL_TIMEOUT)) |
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{ |
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INSTR_TIME_SET_CURRENT(cur_time); |
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INSTR_TIME_SUBTRACT(cur_time, start_time); |
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cur_timeout = timeout - (long) INSTR_TIME_GET_MILLISEC(cur_time); |
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if (cur_timeout <= 0) |
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{ |
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/* Timeout has expired, no need to continue looping */ |
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result |= WL_TIMEOUT; |
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} |
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} |
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} while (result == 0); |
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/* Clean up the event object we created for the socket */ |
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if (sockevent != WSA_INVALID_EVENT) |
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{ |
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WSAEventSelect(sock, NULL, 0); |
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WSACloseEvent(sockevent); |
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} |
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return result; |
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} |
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/*
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* The comments above the unix implementation (unix_latch.c) of this function |
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* apply here as well. |
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*/ |
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void |
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SetLatch(volatile Latch *latch) |
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{ |
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HANDLE handle; |
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/*
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* The memory barrier has be to be placed here to ensure that any flag |
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* variables possibly changed by this process have been flushed to main |
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* memory, before we check/set is_set. |
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*/ |
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pg_memory_barrier(); |
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/* Quick exit if already set */ |
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if (latch->is_set) |
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return; |
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latch->is_set = true; |
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/*
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* See if anyone's waiting for the latch. It can be the current process if |
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* we're in a signal handler. |
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* |
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* Use a local variable here just in case somebody changes the event field |
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* concurrently (which really should not happen). |
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*/ |
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handle = latch->event; |
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if (handle) |
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{ |
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SetEvent(handle); |
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/*
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* Note that we silently ignore any errors. We might be in a signal |
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* handler or other critical path where it's not safe to call elog(). |
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*/ |
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} |
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} |
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void |
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ResetLatch(volatile Latch *latch) |
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{ |
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/* Only the owner should reset the latch */ |
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Assert(latch->owner_pid == MyProcPid); |
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latch->is_set = false; |
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/*
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* Ensure that the write to is_set gets flushed to main memory before we |
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* examine any flag variables. Otherwise a concurrent SetLatch might |
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* falsely conclude that it needn't signal us, even though we have missed |
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* seeing some flag updates that SetLatch was supposed to inform us of. |
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*/ |
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pg_memory_barrier(); |
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} |
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