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Commit0cfc67b

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Add HOLD/RESUME_INTERRUPTS in HandleCatchupInterrupt/HandleNotifyInterrupt.
This prevents a possible longjmp out of the signal handler if a timeoutor SIGINT occurs while something within the handler has transiently setImmediateInterruptOK. For safety we must hold off the timeout or cancelerror until we're back in mainline, or at least till we reach the end ofthe signal handler when ImmediateInterruptOK was true at entry. Thissyncs these functions with the logic now present in handle_sig_alarm.AFAICT there is no live bug here in 9.0 and up, because I don't think wecurrently can wait for any heavyweight lock inside these functions, andthere is no other code (except read-from-client) that will turn onImmediateInterruptOK. However, that was not true pre-9.0: in olderbranches ProcessIncomingNotify might block trying to lock pg_listener, andthen a SIGINT could lead to undesirable control flow. It might be allright anyway given the relatively narrow code ranges in which NOTIFYinterrupts are enabled, but for safety's sake I'm back-patching this.
1 parent478af9b commit0cfc67b

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2 files changed

+20
-8
lines changed

2 files changed

+20
-8
lines changed

‎src/backend/commands/async.c

Lines changed: 10 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -1652,11 +1652,15 @@ HandleNotifyInterrupt(void)
16521652

16531653
/*
16541654
* We may be called while ImmediateInterruptOK is true; turn it off
1655-
* while messing with the NOTIFY state. (We would have to save and
1656-
* restore it anyway, because PGSemaphore operations inside
1657-
* ProcessIncomingNotify() might reset it.)
1655+
* while messing with the NOTIFY state. This prevents problems if
1656+
* SIGINT or similar arrives while we're working. Just to be real
1657+
* sure, bump the interrupt holdoff counter as well. That way, even
1658+
* if something inside ProcessIncomingNotify() transiently sets
1659+
* ImmediateInterruptOK (eg while waiting on a lock), we won't get
1660+
* interrupted until we're done with the notify interrupt.
16581661
*/
16591662
ImmediateInterruptOK= false;
1663+
HOLD_INTERRUPTS();
16601664

16611665
/*
16621666
* I'm not sure whether some flavors of Unix might allow another
@@ -1686,8 +1690,10 @@ HandleNotifyInterrupt(void)
16861690
}
16871691

16881692
/*
1689-
* Restore ImmediateInterruptOK, and check for interrupts if needed.
1693+
* Restore the holdoff level and ImmediateInterruptOK, and check for
1694+
* interrupts if needed.
16901695
*/
1696+
RESUME_INTERRUPTS();
16911697
ImmediateInterruptOK=save_ImmediateInterruptOK;
16921698
if (save_ImmediateInterruptOK)
16931699
CHECK_FOR_INTERRUPTS();

‎src/backend/storage/ipc/sinval.c

Lines changed: 10 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -180,11 +180,15 @@ HandleCatchupInterrupt(void)
180180

181181
/*
182182
* We may be called while ImmediateInterruptOK is true; turn it off
183-
* while messing with the catchup state. (We would have to save and
184-
* restore it anyway, because PGSemaphore operations inside
185-
* ProcessCatchupEvent() might reset it.)
183+
* while messing with the catchup state. This prevents problems if
184+
* SIGINT or similar arrives while we're working. Just to be real
185+
* sure, bump the interrupt holdoff counter as well. That way, even
186+
* if something inside ProcessCatchupEvent() transiently sets
187+
* ImmediateInterruptOK (eg while waiting on a lock), we won't get
188+
* interrupted until we're done with the catchup interrupt.
186189
*/
187190
ImmediateInterruptOK= false;
191+
HOLD_INTERRUPTS();
188192

189193
/*
190194
* I'm not sure whether some flavors of Unix might allow another
@@ -208,8 +212,10 @@ HandleCatchupInterrupt(void)
208212
}
209213

210214
/*
211-
* Restore ImmediateInterruptOK, and check for interrupts if needed.
215+
* Restore the holdoff level and ImmediateInterruptOK, and check for
216+
* interrupts if needed.
212217
*/
218+
RESUME_INTERRUPTS();
213219
ImmediateInterruptOK=save_ImmediateInterruptOK;
214220
if (save_ImmediateInterruptOK)
215221
CHECK_FOR_INTERRUPTS();

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