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Commit8ebc908

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Improve Windows implementation of WaitLatch/WaitLatchOrSocket.
Ensure that signal handlers are serviced before this function returns.This should make the behavior more like Unix. Also, add some moreerror checking, and make some other cosmetic improvements.No back-patch since it's not clear whether this is fixing any live bugthat would affect 9.1. I'm more concerned about 9.2 anyway given ourconsiderable recent expansions in the usage of WaitLatch.
1 parent53216e3 commit8ebc908

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1 file changed

+39
-21
lines changed

1 file changed

+39
-21
lines changed

‎src/backend/port/win32_latch.c‎

Lines changed: 39 additions & 21 deletions
Original file line numberDiff line numberDiff line change
@@ -115,14 +115,19 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock,
115115
else
116116
timeout=INFINITE;
117117

118-
/* Construct an array of event handles for WaitforMultipleObjects() */
118+
/*
119+
* Construct an array of event handles for WaitforMultipleObjects().
120+
*
121+
* Note: pgwin32_signal_event should be first to ensure that it will be
122+
* reported when multiple events are set. We want to guarantee that
123+
* pending signals are serviced.
124+
*/
119125
latchevent=latch->event;
120126

121-
events[0]=latchevent;
122-
events[1]=pgwin32_signal_event;
127+
events[0]=pgwin32_signal_event;
128+
events[1]=latchevent;
123129
numevents=2;
124-
if ((wakeEvents&WL_SOCKET_READABLE)||
125-
(wakeEvents&WL_SOCKET_WRITEABLE))
130+
if (wakeEvents& (WL_SOCKET_READABLE |WL_SOCKET_WRITEABLE))
126131
{
127132
intflags=0;
128133

@@ -132,7 +137,13 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock,
132137
flags |=FD_WRITE;
133138

134139
sockevent=WSACreateEvent();
135-
WSAEventSelect(sock,sockevent,flags);
140+
if (sockevent==WSA_INVALID_EVENT)
141+
elog(ERROR,"failed to create event for socket: error code %u",
142+
WSAGetLastError());
143+
if (WSAEventSelect(sock,sockevent,flags)!=0)
144+
elog(ERROR,"failed to set up event for socket: error code %u",
145+
WSAGetLastError());
146+
136147
events[numevents++]=sockevent;
137148
}
138149
if (wakeEvents&WL_POSTMASTER_DEATH)
@@ -141,6 +152,9 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock,
141152
events[numevents++]=PostmasterHandle;
142153
}
143154

155+
/* Ensure that signals are serviced even if latch is already set */
156+
pgwin32_dispatch_queued_signals();
157+
144158
do
145159
{
146160
/*
@@ -151,6 +165,7 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock,
151165
*/
152166
if (!ResetEvent(latchevent))
153167
elog(ERROR,"ResetEvent failed: error code %lu",GetLastError());
168+
154169
if ((wakeEvents&WL_LATCH_SET)&&latch->is_set)
155170
{
156171
result |=WL_LATCH_SET;
@@ -164,21 +179,20 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock,
164179
rc=WaitForMultipleObjects(numevents,events, FALSE,timeout);
165180

166181
if (rc==WAIT_FAILED)
167-
elog(ERROR,"WaitForMultipleObjects() failed: error code %lu",GetLastError());
168-
169-
/* Participate in Windows signal emulation */
170-
elseif (rc==WAIT_OBJECT_0+1)
171-
pgwin32_dispatch_queued_signals();
172-
182+
elog(ERROR,"WaitForMultipleObjects() failed: error code %lu",
183+
GetLastError());
173184
elseif (rc==WAIT_TIMEOUT)
174185
{
175186
result |=WL_TIMEOUT;
176187
}
177-
elseif ((wakeEvents&WL_POSTMASTER_DEATH)&&
178-
rc==WAIT_OBJECT_0+pmdeath_eventno)
188+
elseif (rc==WAIT_OBJECT_0)
179189
{
180-
/* Postmaster died */
181-
result |=WL_POSTMASTER_DEATH;
190+
/* Service newly-arrived signals */
191+
pgwin32_dispatch_queued_signals();
192+
}
193+
elseif (rc==WAIT_OBJECT_0+1)
194+
{
195+
/* Latch is set, we'll handle that on next iteration of loop */
182196
}
183197
elseif ((wakeEvents& (WL_SOCKET_READABLE |WL_SOCKET_WRITEABLE))&&
184198
rc==WAIT_OBJECT_0+2)/* socket is at event slot 2 */
@@ -187,9 +201,8 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock,
187201

188202
ZeroMemory(&resEvents,sizeof(resEvents));
189203
if (WSAEnumNetworkEvents(sock,sockevent,&resEvents)==SOCKET_ERROR)
190-
ereport(FATAL,
191-
(errmsg_internal("failed to enumerate network events: error code %lu",GetLastError())));
192-
204+
elog(ERROR,"failed to enumerate network events: error code %lu",
205+
GetLastError());
193206
if ((wakeEvents&WL_SOCKET_READABLE)&&
194207
(resEvents.lNetworkEvents&FD_READ))
195208
{
@@ -201,8 +214,13 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock,
201214
result |=WL_SOCKET_WRITEABLE;
202215
}
203216
}
204-
/* Otherwise it must be the latch event */
205-
elseif (rc!=WAIT_OBJECT_0)
217+
elseif ((wakeEvents&WL_POSTMASTER_DEATH)&&
218+
rc==WAIT_OBJECT_0+pmdeath_eventno)
219+
{
220+
/* Postmaster died */
221+
result |=WL_POSTMASTER_DEATH;
222+
}
223+
else
206224
elog(ERROR,"unexpected return code from WaitForMultipleObjects(): %lu",rc);
207225
}
208226
while (result==0);

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