Add Win32 semaphore implementation, rather than mimicking SysV
semaphores. Qingqing Zhou
This commit is contained in:
Bruce Momjian
parent
291724dfa8
commit
908f317b73
23
configure.in
23
configure.in
@ -1,5 +1,5 @@
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dnl Process this file with autoconf to produce a configure script.
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dnl $PostgreSQL: pgsql/configure.in,v 1.462 2006/04/29 00:51:41 momjian Exp $
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dnl $PostgreSQL: pgsql/configure.in,v 1.463 2006/04/29 16:34:41 momjian Exp $
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dnl
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dnl Developers, please strive to achieve this order:
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dnl
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@ -1269,17 +1269,22 @@ AC_FUNC_MEMCMP
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# Select semaphore implementation type.
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if test x"$USE_NAMED_POSIX_SEMAPHORES" = x"1" ; then
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AC_DEFINE(USE_NAMED_POSIX_SEMAPHORES, 1, [Define to select named POSIX semaphores.])
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SEMA_IMPLEMENTATION="src/backend/port/posix_sema.c"
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else
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if test x"$USE_UNNAMED_POSIX_SEMAPHORES" = x"1" ; then
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AC_DEFINE(USE_UNNAMED_POSIX_SEMAPHORES, 1, [Define to select unnamed POSIX semaphores.])
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if test "$PORTNAME" != "win32"; then
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if test x"$USE_NAMED_POSIX_SEMAPHORES" = x"1" ; then
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AC_DEFINE(USE_NAMED_POSIX_SEMAPHORES, 1, [Define to select named POSIX semaphores.])
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SEMA_IMPLEMENTATION="src/backend/port/posix_sema.c"
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else
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AC_DEFINE(USE_SYSV_SEMAPHORES, 1, [Define to select SysV-style semaphores.])
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SEMA_IMPLEMENTATION="src/backend/port/sysv_sema.c"
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if test x"$USE_UNNAMED_POSIX_SEMAPHORES" = x"1" ; then
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AC_DEFINE(USE_UNNAMED_POSIX_SEMAPHORES, 1, [Define to select unnamed POSIX semaphores.])
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SEMA_IMPLEMENTATION="src/backend/port/posix_sema.c"
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else
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AC_DEFINE(USE_SYSV_SEMAPHORES, 1, [Define to select SysV-style semaphores.])
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SEMA_IMPLEMENTATION="src/backend/port/sysv_sema.c"
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fi
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fi
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else
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AC_DEFINE(USE_WIN32_SEMAPHORES, 1, [Define to select Win32-style semaphores.])
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SEMA_IMPLEMENTATION="src/backend/port/win32_sema.c"
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fi
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195
src/backend/port/win32_sema.c
Normal file
195
src/backend/port/win32_sema.c
Normal file
@ -0,0 +1,195 @@
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/*-------------------------------------------------------------------------
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*
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* win32_sema.c
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* Microsoft Windows Win32 Semaphores Emulation
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*
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* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/port/win32_sema.c,v 1.1 2006/04/29 16:34:41 momjian Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "miscadmin.h"
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#include "storage/ipc.h"
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#include "storage/pg_sema.h"
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static HANDLE *mySemSet; /* IDs of sema sets acquired so far */
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static int numSems; /* number of sema sets acquired so far */
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static int maxSems; /* allocated size of mySemaSet array */
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static void ReleaseSemaphores(int code, Datum arg);
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/*
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* PGReserveSemaphores --- initialize semaphore support
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*
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* In the Win32 implementation, we acquire semaphores on-demand; the
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* maxSemas parameter is just used to size the array that keeps track of
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* acquired semas for subsequent releasing. We use anonymous semaphores
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* so the semaphores are automatically freed when the last referencing
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* process exits.
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*/
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void PGReserveSemaphores(int maxSemas, int port)
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{
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mySemSet = (HANDLE *)malloc(maxSemas * sizeof(HANDLE));
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if (mySemSet == NULL)
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elog(PANIC, "out of memory");
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numSems = 0;
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maxSems = maxSemas;
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on_shmem_exit(ReleaseSemaphores, 0);
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}
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/*
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* Release semaphores at shutdown or shmem reinitialization
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*
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* (called as an on_shmem_exit callback, hence funny argument list)
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*/
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static void
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ReleaseSemaphores(int code, Datum arg)
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{
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int i;
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for (i = 0; i < numSems; i++)
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CloseHandle(mySemSet[i]);
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free(mySemSet);
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}
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/*
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* PGSemaphoreCreate
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*
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* Initialize a PGSemaphore structure to represent a sema with count 1
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*/
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void PGSemaphoreCreate(PGSemaphore sema)
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{
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HANDLE cur_handle;
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SECURITY_ATTRIBUTES sec_attrs;
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/* Can't do this in a backend, because static state is postmaster's */
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Assert(!IsUnderPostmaster);
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if (numSems >= maxSems)
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elog(PANIC, "too many semaphores created");
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ZeroMemory(&sec_attrs, sizeof(sec_attrs));
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sec_attrs.nLength = sizeof(sec_attrs);
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sec_attrs.lpSecurityDescriptor = NULL;
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sec_attrs.bInheritHandle = TRUE;
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/* We don't need a named semaphore */
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cur_handle = CreateSemaphore(&sec_attrs, 1, 1, NULL);
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if (cur_handle)
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{
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/* Successfully done */
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*sema = cur_handle;
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mySemSet[numSems++] = cur_handle;
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}
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else
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ereport(PANIC,
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(errmsg("could not create semaphore: error code %d", (int)GetLastError())));
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}
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/*
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* PGSemaphoreReset
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*
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* Reset a previously-initialized PGSemaphore to have count 0
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*/
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void PGSemaphoreReset(PGSemaphore sema)
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{
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/*
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* There's no direct API for this in Win32, so we have to ratchet the
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* semaphore down to 0 with repeated trylock's.
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*/
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while (PGSemaphoreTryLock(sema));
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}
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/*
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* PGSemaphoreLock
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*
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* Lock a semaphore (decrement count), blocking if count would be < 0.
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* Serve the interrupt if interruptOK is true.
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*/
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void PGSemaphoreLock(PGSemaphore sema, bool interruptOK)
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{
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DWORD ret;
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HANDLE wh[2];
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wh[0] = *sema;
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wh[1] = pgwin32_signal_event;
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do
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{
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ImmediateInterruptOK = interruptOK;
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CHECK_FOR_INTERRUPTS();
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errno = 0;
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ret = WaitForMultipleObjectsEx(2, wh, FALSE, INFINITE, TRUE);
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if (ret == WAIT_OBJECT_0)
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{
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/* We got it! */
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return;
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}
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else if (ret == WAIT_OBJECT_0 + 1)
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{
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/* Signal event is set - we have a signal to deliver */
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pgwin32_dispatch_queued_signals();
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errno = EINTR;
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}
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else
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/* Otherwise we are in trouble */
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errno = EIDRM;
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ImmediateInterruptOK = false;
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} while (errno == EINTR);
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if (errno != 0)
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ereport(FATAL,
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(errmsg("could not lock semaphore: error code %d", (int) GetLastError())));
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}
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/*
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* PGSemaphoreUnlock
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*
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* Unlock a semaphore (increment count)
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*/
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void PGSemaphoreUnlock(PGSemaphore sema)
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{
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if (!ReleaseSemaphore(*sema, 1, NULL))
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ereport(FATAL,
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(errmsg("could not unlock semaphore: error code %d", (int) GetLastError())));
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}
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/*
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* PGSemaphoreTryLock
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*
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* Lock a semaphore only if able to do so without blocking
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*/
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bool PGSemaphoreTryLock(PGSemaphore sema)
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{
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DWORD ret;
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ret = WaitForSingleObject(*sema, 0);
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if (ret == WAIT_OBJECT_0)
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{
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/* We got it! */
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return true;
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}
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else if (ret == WAIT_TIMEOUT)
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{
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/* Can't get it */
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errno = EAGAIN;
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return false;
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}
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/* Otherwise we are in trouble */
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ereport(FATAL,
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(errmsg("could not try-lock semaphore: error code %d", (int) GetLastError())));
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/* keep compiler quiet */
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return false;
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}
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@ -13,7 +13,7 @@
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* Portions Copyright (c) 1996-2006, 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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* $PostgreSQL: pgsql/src/include/storage/pg_sema.h,v 1.8 2006/03/05 15:58:59 momjian Exp $
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* $PostgreSQL: pgsql/src/include/storage/pg_sema.h,v 1.9 2006/04/29 16:34:41 momjian Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -54,6 +54,11 @@ typedef struct PGSemaphoreData
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} PGSemaphoreData;
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#endif
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#ifdef USE_WIN32_SEMAPHORES
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typedef HANDLE PGSemaphoreData;
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#endif
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typedef PGSemaphoreData *PGSemaphore;
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