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Commitde35a97

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committed
Handle WAIT_IO_COMPLETION return from WaitForMultipleObjectsEx().
This return code is possible wherever we pass bAlertable = TRUE; itarises when Windows caused the current thread to run an "I/O completionroutine" or an "asynchronous procedure call". PostgreSQL does notprovoke either of those Windows facilities, hence this bug remaininglargely unnoticed, but other local code might do so. Due to a shortageof complaints, no back-patch for now.Per report from Shiv Shivaraju Gowda, this bug can causePGSemaphoreLock() to PANIC. The bug can also cause select() to reporttimeout expiration too early, which might confuse pgstat_init() andCheckRADIUSAuth().
1 parente565ff7 commitde35a97

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2 files changed

+37
-24
lines changed

2 files changed

+37
-24
lines changed

‎src/backend/port/win32/socket.c

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -623,7 +623,8 @@ pgwin32_select(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, c
623623
return0;
624624
}
625625

626-
if (r==WAIT_OBJECT_0+numevents)
626+
/* Signal-like events. */
627+
if (r==WAIT_OBJECT_0+numevents||r==WAIT_IO_COMPLETION)
627628
{
628629
pgwin32_dispatch_queued_signals();
629630
errno=EINTR;

‎src/backend/port/win32_sema.c

Lines changed: 35 additions & 23 deletions
Original file line numberDiff line numberDiff line change
@@ -118,8 +118,10 @@ PGSemaphoreReset(PGSemaphore sema)
118118
void
119119
PGSemaphoreLock(PGSemaphoresema,boolinterruptOK)
120120
{
121-
DWORDret;
122121
HANDLEwh[2];
122+
booldone= false;
123+
124+
ImmediateInterruptOK=interruptOK;
123125

124126
/*
125127
* Note: pgwin32_signal_event should be first to ensure that it will be
@@ -135,34 +137,44 @@ PGSemaphoreLock(PGSemaphore sema, bool interruptOK)
135137
* no hidden magic about whether the syscall will internally service a
136138
* signal --- we do that ourselves.
137139
*/
138-
do
140+
while (!done)
139141
{
140-
ImmediateInterruptOK=interruptOK;
141-
CHECK_FOR_INTERRUPTS();
142+
DWORDrc;
142143

143-
ret=WaitForMultipleObjectsEx(2,wh, FALSE,INFINITE, TRUE);
144+
CHECK_FOR_INTERRUPTS();
144145

145-
if (ret==WAIT_OBJECT_0)
146+
rc=WaitForMultipleObjectsEx(2,wh, FALSE,INFINITE, TRUE);
147+
switch (rc)
146148
{
147-
/* Signal event is set - we have a signal to deliver */
148-
pgwin32_dispatch_queued_signals();
149-
errno=EINTR;
149+
caseWAIT_OBJECT_0:
150+
/* Signal event is set - we have a signal to deliver */
151+
pgwin32_dispatch_queued_signals();
152+
break;
153+
caseWAIT_OBJECT_0+1:
154+
/* We got it! */
155+
done= true;
156+
break;
157+
caseWAIT_IO_COMPLETION:
158+
/*
159+
* The system interrupted the wait to execute an I/O
160+
* completion routine or asynchronous procedure call in this
161+
* thread. PostgreSQL does not provoke either of these, but
162+
* atypical loaded DLLs or even other processes might do so.
163+
* Now, resume waiting.
164+
*/
165+
break;
166+
caseWAIT_FAILED:
167+
ereport(FATAL,
168+
(errmsg("could not lock semaphore: error code %lu",
169+
GetLastError())));
170+
break;
171+
default:
172+
elog(FATAL,"unexpected return code from WaitForMultipleObjectsEx(): %lu",rc);
173+
break;
150174
}
151-
elseif (ret==WAIT_OBJECT_0+1)
152-
{
153-
/* We got it! */
154-
errno=0;
155-
}
156-
else
157-
/* Otherwise we are in trouble */
158-
errno=EIDRM;
159-
160-
ImmediateInterruptOK= false;
161-
}while (errno==EINTR);
175+
}
162176

163-
if (errno!=0)
164-
ereport(FATAL,
165-
(errmsg("could not lock semaphore: error code %lu",GetLastError())));
177+
ImmediateInterruptOK= false;
166178
}
167179

168180
/*

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