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Add Win32 semaphore implementation, rather than mimicking SysV
semaphores. Qingqing Zhou
1 parent 291724d commit 908f317

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3 files changed

+215
-10
lines changed

3 files changed

+215
-10
lines changed

‎configure.in

Lines changed: 14 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,5 @@
11
dnl Process this file with autoconf to produce a configure script.
2-
dnl $PostgreSQL: pgsql/configure.in,v 1.462 2006/04/29 00:51:41 momjian Exp $
2+
dnl $PostgreSQL: pgsql/configure.in,v 1.463 2006/04/29 16:34:41 momjian Exp $
33
dnl
44
dnl Developers, please strive to achieve this order:
55
dnl
@@ -1269,17 +1269,22 @@ AC_FUNC_MEMCMP
12691269

12701270

12711271
# Select semaphore implementation type.
1272-
if test x"$USE_NAMED_POSIX_SEMAPHORES" = x"1" ; then
1273-
AC_DEFINE(USE_NAMED_POSIX_SEMAPHORES, 1, [Define to select named POSIX semaphores.])
1274-
SEMA_IMPLEMENTATION="src/backend/port/posix_sema.c"
1275-
else
1276-
if test x"$USE_UNNAMED_POSIX_SEMAPHORES" = x"1" ; then
1277-
AC_DEFINE(USE_UNNAMED_POSIX_SEMAPHORES, 1, [Define to select unnamed POSIX semaphores.])
1272+
if test "$PORTNAME" != "win32"; then
1273+
if test x"$USE_NAMED_POSIX_SEMAPHORES" = x"1" ; then
1274+
AC_DEFINE(USE_NAMED_POSIX_SEMAPHORES, 1, [Define to select named POSIX semaphores.])
12781275
SEMA_IMPLEMENTATION="src/backend/port/posix_sema.c"
12791276
else
1280-
AC_DEFINE(USE_SYSV_SEMAPHORES, 1, [Define to select SysV-style semaphores.])
1281-
SEMA_IMPLEMENTATION="src/backend/port/sysv_sema.c"
1277+
if test x"$USE_UNNAMED_POSIX_SEMAPHORES" = x"1" ; then
1278+
AC_DEFINE(USE_UNNAMED_POSIX_SEMAPHORES, 1, [Define to select unnamed POSIX semaphores.])
1279+
SEMA_IMPLEMENTATION="src/backend/port/posix_sema.c"
1280+
else
1281+
AC_DEFINE(USE_SYSV_SEMAPHORES, 1, [Define to select SysV-style semaphores.])
1282+
SEMA_IMPLEMENTATION="src/backend/port/sysv_sema.c"
1283+
fi
12821284
fi
1285+
else
1286+
AC_DEFINE(USE_WIN32_SEMAPHORES, 1, [Define to select Win32-style semaphores.])
1287+
SEMA_IMPLEMENTATION="src/backend/port/win32_sema.c"
12831288
fi
12841289

12851290

‎src/backend/port/win32_sema.c

Lines changed: 195 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,195 @@
1+
/*-------------------------------------------------------------------------
2+
*
3+
* win32_sema.c
4+
* Microsoft Windows Win32 Semaphores Emulation
5+
*
6+
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
7+
*
8+
* IDENTIFICATION
9+
* $Header: /cvsroot/pgsql/src/backend/port/win32_sema.c,v 1.1 2006/04/29 16:34:41 momjian Exp $
10+
*
11+
*-------------------------------------------------------------------------
12+
*/
13+
14+
#include "postgres.h"
15+
16+
#include "miscadmin.h"
17+
#include "storage/ipc.h"
18+
#include "storage/pg_sema.h"
19+
20+
static HANDLE *mySemSet; /* IDs of sema sets acquired so far */
21+
static int numSems; /* number of sema sets acquired so far */
22+
static int maxSems; /* allocated size of mySemaSet array */
23+
24+
static void ReleaseSemaphores(int code, Datum arg);
25+
26+
/*
27+
* PGReserveSemaphores --- initialize semaphore support
28+
*
29+
* In the Win32 implementation, we acquire semaphores on-demand; the
30+
* maxSemas parameter is just used to size the array that keeps track of
31+
* acquired semas for subsequent releasing. We use anonymous semaphores
32+
* so the semaphores are automatically freed when the last referencing
33+
* process exits.
34+
*/
35+
void PGReserveSemaphores(int maxSemas, int port)
36+
{
37+
mySemSet = (HANDLE *)malloc(maxSemas * sizeof(HANDLE));
38+
if (mySemSet == NULL)
39+
elog(PANIC, "out of memory");
40+
numSems = 0;
41+
maxSems = maxSemas;
42+
43+
on_shmem_exit(ReleaseSemaphores, 0);
44+
}
45+
46+
/*
47+
* Release semaphores at shutdown or shmem reinitialization
48+
*
49+
* (called as an on_shmem_exit callback, hence funny argument list)
50+
*/
51+
static void
52+
ReleaseSemaphores(int code, Datum arg)
53+
{
54+
int i;
55+
56+
for (i = 0; i < numSems; i++)
57+
CloseHandle(mySemSet[i]);
58+
free(mySemSet);
59+
}
60+
61+
/*
62+
* PGSemaphoreCreate
63+
*
64+
* Initialize a PGSemaphore structure to represent a sema with count 1
65+
*/
66+
void PGSemaphoreCreate(PGSemaphore sema)
67+
{
68+
HANDLE cur_handle;
69+
SECURITY_ATTRIBUTES sec_attrs;
70+
71+
/* Can't do this in a backend, because static state is postmaster's */
72+
Assert(!IsUnderPostmaster);
73+
74+
if (numSems >= maxSems)
75+
elog(PANIC, "too many semaphores created");
76+
77+
ZeroMemory(&sec_attrs, sizeof(sec_attrs));
78+
sec_attrs.nLength = sizeof(sec_attrs);
79+
sec_attrs.lpSecurityDescriptor = NULL;
80+
sec_attrs.bInheritHandle = TRUE;
81+
82+
/* We don't need a named semaphore */
83+
cur_handle = CreateSemaphore(&sec_attrs, 1, 1, NULL);
84+
if (cur_handle)
85+
{
86+
/* Successfully done */
87+
*sema = cur_handle;
88+
mySemSet[numSems++] = cur_handle;
89+
}
90+
else
91+
ereport(PANIC,
92+
(errmsg("could not create semaphore: error code %d", (int)GetLastError())));
93+
}
94+
95+
/*
96+
* PGSemaphoreReset
97+
*
98+
* Reset a previously-initialized PGSemaphore to have count 0
99+
*/
100+
void PGSemaphoreReset(PGSemaphore sema)
101+
{
102+
/*
103+
* There's no direct API for this in Win32, so we have to ratchet the
104+
* semaphore down to 0 with repeated trylock's.
105+
*/
106+
while (PGSemaphoreTryLock(sema));
107+
}
108+
109+
/*
110+
* PGSemaphoreLock
111+
*
112+
* Lock a semaphore (decrement count), blocking if count would be < 0.
113+
* Serve the interrupt if interruptOK is true.
114+
*/
115+
void PGSemaphoreLock(PGSemaphore sema, bool interruptOK)
116+
{
117+
DWORD ret;
118+
HANDLE wh[2];
119+
120+
wh[0] = *sema;
121+
wh[1] = pgwin32_signal_event;
122+
123+
do
124+
{
125+
ImmediateInterruptOK = interruptOK;
126+
CHECK_FOR_INTERRUPTS();
127+
128+
errno = 0;
129+
ret = WaitForMultipleObjectsEx(2, wh, FALSE, INFINITE, TRUE);
130+
131+
if (ret == WAIT_OBJECT_0)
132+
{
133+
/* We got it! */
134+
return;
135+
}
136+
else if (ret == WAIT_OBJECT_0 + 1)
137+
{
138+
/* Signal event is set - we have a signal to deliver */
139+
pgwin32_dispatch_queued_signals();
140+
errno = EINTR;
141+
}
142+
else
143+
/* Otherwise we are in trouble */
144+
errno = EIDRM;
145+
146+
ImmediateInterruptOK = false;
147+
} while (errno == EINTR);
148+
149+
if (errno != 0)
150+
ereport(FATAL,
151+
(errmsg("could not lock semaphore: error code %d", (int) GetLastError())));
152+
}
153+
154+
/*
155+
* PGSemaphoreUnlock
156+
*
157+
* Unlock a semaphore (increment count)
158+
*/
159+
void PGSemaphoreUnlock(PGSemaphore sema)
160+
{
161+
if (!ReleaseSemaphore(*sema, 1, NULL))
162+
ereport(FATAL,
163+
(errmsg("could not unlock semaphore: error code %d", (int) GetLastError())));
164+
}
165+
166+
/*
167+
* PGSemaphoreTryLock
168+
*
169+
* Lock a semaphore only if able to do so without blocking
170+
*/
171+
bool PGSemaphoreTryLock(PGSemaphore sema)
172+
{
173+
DWORD ret;
174+
175+
ret = WaitForSingleObject(*sema, 0);
176+
177+
if (ret == WAIT_OBJECT_0)
178+
{
179+
/* We got it! */
180+
return true;
181+
}
182+
else if (ret == WAIT_TIMEOUT)
183+
{
184+
/* Can't get it */
185+
errno = EAGAIN;
186+
return false;
187+
}
188+
189+
/* Otherwise we are in trouble */
190+
ereport(FATAL,
191+
(errmsg("could not try-lock semaphore: error code %d", (int) GetLastError())));
192+
193+
/* keep compiler quiet */
194+
return false;
195+
}

‎src/include/storage/pg_sema.h

Lines changed: 6 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -13,7 +13,7 @@
1313
* Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
1414
* Portions Copyright (c) 1994, Regents of the University of California
1515
*
16-
* $PostgreSQL: pgsql/src/include/storage/pg_sema.h,v 1.8 2006/03/05 15:58:59 momjian Exp $
16+
* $PostgreSQL: pgsql/src/include/storage/pg_sema.h,v 1.9 2006/04/29 16:34:41 momjian Exp $
1717
*
1818
*-------------------------------------------------------------------------
1919
*/
@@ -54,6 +54,11 @@ typedef struct PGSemaphoreData
5454
} PGSemaphoreData;
5555
#endif
5656

57+
#ifdef USE_WIN32_SEMAPHORES
58+
59+
typedef HANDLE PGSemaphoreData;
60+
#endif
61+
5762
typedef PGSemaphoreData *PGSemaphore;
5863

5964

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