From: Chao Li <li.evan.chao@gmail.com>
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Subject: PoC: Add condition variable support to WaitEventSetWait()
Message-Id: <F12DAA03-F4FA-4F12-8F17-B7C4BE361ED0@gmail.com>
Date: Tue, 31 Mar 2026 15:28:42 +0800
To: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
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Hi,

There is an XXX comment in WalSndWait():
```
     * XXX: A desirable future improvement would be to add support for =
CVs
     * into WaitEventSetWait().
```

I have been exploring a possible approach for that. This patch is a PoC =
that adds ConditionVariable support to WaitEventSet. This v1 is mainly =
intended to gather feedback on the design, so I have only done some =
basic testing so far, such as a normal logical replication workflow.

I=E2=80=99d like to highlight a few key points about the design:

1. In the current WalSndWait(), although it prepares to sleep on a =
ConditionVariable, it does not actually check whether the CV has been =
signaled. In this PoC, I kept that same behavior. However, I tried to =
make the WaitEventSet support for CVs generic, so that if we want to add =
actual signal checking in the future, that would be possible.

2. To keep the design generic, this patch introduces a new wait event =
type, WL_CONDITION_VARIABLE. A WL_CONDITION_VARIABLE event occupies a =
position in the event array, similar to latch and socket events. When a =
CV is signaled, the corresponding WL_CONDITION_VARIABLE event is =
returned in occurred_events.

3. The WaitEventSet APIs AddWaitEventToSet() and ModifyWaitEvent() are =
extended to support CVs by adding one more parameter =E2=80=9Ccv" to =
both APIs. The downside of this approach is that all call sites of these =
two APIs need to be updated. I also considered adding separate APIs for =
CVs, such as AddWaitEventToSetForCV() and ModifyWaitEventForCV(), since =
CVs do not rely on the kernel and it might therefore make sense to =
decouple them from socket and latch handling. But for v1, I chose the =
more generic approach. I=E2=80=99d be interested in hearing comments on =
this part of the design.

4. One important point is that this patch extends the WaitEventSet =
abstraction, not the underlying kernel wait primitives. A =
ConditionVariable is still a userspace/shared-memory concept, but with =
this design it can participate in the same waiting framework as sockets =
and latches. I think that is useful because it allows mixed waits to be =
handled through one interface.

Here is the v1 patch.

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/


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	filename=v1-0001-Add-condition-variable-support-to-WaitEventSetWai.patch
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Date:=20Tue,=2031=20Mar=202026=2008:25:12=20+0800=0ASubject:=20[PATCH=20=
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WalSndWait()=20currently=20combines=20WaitEventSetWait()=20with=20manual=0A=
ConditionVariablePrepareToSleep()=20/=20ConditionVariableCancelSleep()=0A=
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wait-event=20set=20itself.=0A=0AAuthor:=20Chao=20Li=20<lic@highgo.com>=0A=
---=0A=20src/backend/executor/nodeAppend.c=20=20=20=20=20=20=20=20=20=20=20=
=20=20|=20=20=204=20+-=0A=20src/backend/libpq/be-secure.c=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20|=20=20=204=20+-=0A=20=
src/backend/libpq/pqcomm.c=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20|=20=2012=20+-=0A=20src/backend/postmaster/postmaster.c=20=20=
=20=20=20=20=20=20=20=20=20|=20=20=204=20+-=0A=20=
src/backend/postmaster/syslogger.c=20=20=20=20=20=20=20=20=20=20=20=20|=20=
=20=204=20+-=0A=20src/backend/replication/walsender.c=20=20=20=20=20=20=20=
=20=20=20=20|=20=2017=20++-=0A=20src/backend/storage/ipc/latch.c=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20|=20=2016=20+--=0A=20=
src/backend/storage/ipc/waiteventset.c=20=20=20=20=20=20=20=20|=20116=20=
+++++++++++++++++-=0A=20src/backend/storage/lmgr/condition_variable.c=20=
|=20=2033=20+++--=0A=20src/backend/utils/init/miscinit.c=20=20=20=20=20=20=
=20=20=20=20=20=20=20|=20=20=204=20+-=0A=20src/include/libpq/libpq.h=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20|=20=20=203=20=
+-=0A=20src/include/storage/condition_variable.h=20=20=20=20=20=20|=20=20=
=201=20+=0A=20src/include/storage/waiteventset.h=20=20=20=20=20=20=20=20=20=
=20=20=20|=20=20=207=20+-=0A=2013=20files=20changed,=20179=20=
insertions(+),=2046=20deletions(-)=0A=0Adiff=20--git=20=
a/src/backend/executor/nodeAppend.c=20=
b/src/backend/executor/nodeAppend.c=0Aindex=2085c85569b5e..27895b96b50=20=
100644=0A---=20a/src/backend/executor/nodeAppend.c=0A+++=20=
b/src/backend/executor/nodeAppend.c=0A@@=20-1045,7=20+1045,7=20@@=20=
ExecAppendAsyncEventWait(AppendState=20*node)=0A=20=09=
Assert(node->as_eventset=20=3D=3D=20NULL);=0A=20=09node->as_eventset=20=3D=
=20CreateWaitEventSet(CurrentResourceOwner,=20nevents);=0A=20=09=
AddWaitEventToSet(node->as_eventset,=20WL_EXIT_ON_PM_DEATH,=20=
PGINVALID_SOCKET,=0A-=09=09=09=09=09=20=20NULL,=20NULL);=0A+=09=09=09=09=09=
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subplan=20a=20chance=20to=20add=20an=20event.=20*/=0A=20=09i=20=3D=20-1;=0A=
@@=20-1081,7=20+1081,7=20@@=20ExecAppendAsyncEventWait(AppendState=20=
*node)=0A=20=09=20*=20extensions=20too.=0A=20=09=20*/=0A=20=09=
AddWaitEventToSet(node->as_eventset,=20WL_LATCH_SET,=20PGINVALID_SOCKET,=0A=
-=09=09=09=09=09=20=20MyLatch,=20NULL);=0A+=09=09=09=09=09=20=20MyLatch,=20=
NULL,=20NULL);=0A=20=0A=20=09/*=20Return=20at=20most=20EVENT_BUFFER_SIZE=20=
events=20in=20one=20call.=20*/=0A=20=09if=20(nevents=20>=20=
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b/src/backend/libpq/be-secure.c=0Aindex=20617704bb993..0a406a050d9=20=
100644=0A---=20a/src/backend/libpq/be-secure.c=0A+++=20=
b/src/backend/libpq/be-secure.c=0A@@=20-217,7=20+217,7=20@@=20retry:=0A=20=
=0A=20=09=09Assert(waitfor);=0A=20=0A-=09=09ModifyWaitEvent(FeBeWaitSet,=20=
FeBeWaitSetSocketPos,=20waitfor,=20NULL);=0A+=09=09=
ModifyWaitEvent(FeBeWaitSet,=20FeBeWaitSetSocketPos,=20waitfor,=20NULL,=20=
NULL);=0A=20=0A=20=09=09WaitEventSetWait(FeBeWaitSet,=20-1=20/*=20no=20=
timeout=20*/=20,=20&event,=201,=0A=20=09=09=09=09=09=09=20=
WAIT_EVENT_CLIENT_READ);=0A@@=20-342,7=20+342,7=20@@=20retry:=0A=20=0A=20=
=09=09Assert(waitfor);=0A=20=0A-=09=09ModifyWaitEvent(FeBeWaitSet,=20=
FeBeWaitSetSocketPos,=20waitfor,=20NULL);=0A+=09=09=
ModifyWaitEvent(FeBeWaitSet,=20FeBeWaitSetSocketPos,=20waitfor,=20NULL,=20=
NULL);=0A=20=0A=20=09=09WaitEventSetWait(FeBeWaitSet,=20-1=20/*=20no=20=
timeout=20*/=20,=20&event,=201,=0A=20=09=09=09=09=09=09=20=
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b/src/backend/libpq/pqcomm.c=0Aindex=204a442f22df6..5d3a5c22db0=20100644=0A=
---=20a/src/backend/libpq/pqcomm.c=0A+++=20b/src/backend/libpq/pqcomm.c=0A=
@@=20-177,6=20+177,7=20@@=20pq_init(ClientSocket=20*client_sock)=0A=20=09=
Port=09=20=20=20*port;=0A=20=09int=09=09=09socket_pos=20=
PG_USED_FOR_ASSERTS_ONLY;=0A=20=09int=09=09=09latch_pos=20=
PG_USED_FOR_ASSERTS_ONLY;=0A+=09int=09=09=09cv_pos=20=
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struct=20and=20copy=20the=20ClientSocket=20contents=20to=20it=20*/=0A=20=09=
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pq_init(ClientSocket=20*client_sock)=0A=20=0A=20=09FeBeWaitSet=20=3D=20=
CreateWaitEventSet(NULL,=20FeBeWaitSetNEvents);=0A=20=09socket_pos=20=3D=20=
AddWaitEventToSet(FeBeWaitSet,=20WL_SOCKET_WRITEABLE,=0A-=09=09=09=09=09=09=
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=20MyLatch,=20NULL,=20NULL);=0A+=09cv_pos=20=3D=20=
AddWaitEventToSet(FeBeWaitSet,=20WL_CONDITION_VARIABLE,=20=
PGINVALID_SOCKET,=0A+=09=09=09=09=09=09=09=20=20=20NULL,=20NULL,=20=
NULL);=0A=20=09AddWaitEventToSet(FeBeWaitSet,=20WL_POSTMASTER_DEATH,=20=
PGINVALID_SOCKET,=0A-=09=09=09=09=09=20=20NULL,=20NULL);=0A+=09=09=09=09=09=
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positions=20match=20the=20order=20we=20added=20them,=20but=20let's=20=
sanity=0A@@=20-319,6=20+322,7=20@@=20pq_init(ClientSocket=20=
*client_sock)=0A=20=09=20*/=0A=20=09Assert(socket_pos=20=3D=3D=20=
FeBeWaitSetSocketPos);=0A=20=09Assert(latch_pos=20=3D=3D=20=
FeBeWaitSetLatchPos);=0A+=09Assert(cv_pos=20=3D=3D=20FeBeWaitSetCVPos);=0A=
=20=0A=20=09return=20port;=0A=20}=0A@@=20-2063,7=20+2067,7=20@@=20=
pq_check_connection(void)=0A=20=09=20*=20It's=20OK=20to=20modify=20the=20=
socket=20event=20filter=20without=20restoring,=20because=0A=20=09=20*=20=
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*/=0A-=09ModifyWaitEvent(FeBeWaitSet,=20FeBeWaitSetSocketPos,=20=
WL_SOCKET_CLOSED,=20NULL);=0A+=09ModifyWaitEvent(FeBeWaitSet,=20=
FeBeWaitSetSocketPos,=20WL_SOCKET_CLOSED,=20NULL,=20NULL);=0A=20=0A=20=
retry:=0A=20=09rc=20=3D=20WaitEventSetWait(FeBeWaitSet,=200,=20events,=20=
lengthof(events),=200);=0Adiff=20--git=20=
a/src/backend/postmaster/postmaster.c=20=
b/src/backend/postmaster/postmaster.c=0Aindex=20abf0c97569e..f96cce8730d=20=
100644=0A---=20a/src/backend/postmaster/postmaster.c=0A+++=20=
b/src/backend/postmaster/postmaster.c=0A@@=20-1638,13=20+1638,13=20@@=20=
ConfigurePostmasterWaitSet(bool=20accept_connections)=0A=20=09=
pm_wait_set=20=3D=20CreateWaitEventSet(NULL,=0A=20=09=09=09=09=09=09=09=09=
=09=20accept_connections=20?=20(1=20+=20NumListenSockets)=20:=201);=0A=20=
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MyLatch,=0A-=09=09=09=09=09=20=20NULL);=0A+=09=09=09=09=09=20=20NULL,=20=
NULL);=0A=20=0A=20=09if=20(accept_connections)=0A=20=09{=0A=20=09=09for=20=
(int=20i=20=3D=200;=20i=20<=20NumListenSockets;=20i++)=0A=20=09=09=09=
AddWaitEventToSet(pm_wait_set,=20WL_SOCKET_ACCEPT,=20ListenSockets[i],=0A=
-=09=09=09=09=09=09=09=20=20NULL,=20NULL);=0A+=09=09=09=09=09=09=09=20=20=
NULL,=20NULL,=20NULL);=0A=20=09}=0A=20}=0A=20=0Adiff=20--git=20=
a/src/backend/postmaster/syslogger.c=20=
b/src/backend/postmaster/syslogger.c=0Aindex=200c2a7bc8578..4db7df8e4a5=20=
100644=0A---=20a/src/backend/postmaster/syslogger.c=0A+++=20=
b/src/backend/postmaster/syslogger.c=0A@@=20-338,9=20+338,9=20@@=20=
SysLoggerMain(const=20void=20*startup_data,=20size_t=20startup_data_len)=0A=
=20=09=20*=20(including=20the=20postmaster).=0A=20=09=20*/=0A=20=09wes=20=
=3D=20CreateWaitEventSet(NULL,=202);=0A-=09AddWaitEventToSet(wes,=20=
WL_LATCH_SET,=20PGINVALID_SOCKET,=20MyLatch,=20NULL);=0A+=09=
AddWaitEventToSet(wes,=20WL_LATCH_SET,=20PGINVALID_SOCKET,=20MyLatch,=20=
NULL,=20NULL);=0A=20#ifndef=20WIN32=0A-=09AddWaitEventToSet(wes,=20=
WL_SOCKET_READABLE,=20syslogPipe[0],=20NULL,=20NULL);=0A+=09=
AddWaitEventToSet(wes,=20WL_SOCKET_READABLE,=20syslogPipe[0],=20NULL,=20=
NULL,=20NULL);=0A=20#endif=0A=20=0A=20=09/*=20main=20worker=20loop=20*/=0A=
diff=20--git=20a/src/backend/replication/walsender.c=20=
b/src/backend/replication/walsender.c=0Aindex=2066507e9c2dd..d2749a2ca67=20=
100644=0A---=20a/src/backend/replication/walsender.c=0A+++=20=
b/src/backend/replication/walsender.c=0A@@=20-3846,8=20+3846,9=20@@=20=
static=20void=0A=20WalSndWait(uint32=20socket_events,=20long=20timeout,=20=
uint32=20wait_event)=0A=20{=0A=20=09WaitEvent=09event;=0A+=09=
ConditionVariable=20*cv=20=3D=20NULL;=0A=20=0A-=09=
ModifyWaitEvent(FeBeWaitSet,=20FeBeWaitSetSocketPos,=20socket_events,=20=
NULL);=0A+=09ModifyWaitEvent(FeBeWaitSet,=20FeBeWaitSetSocketPos,=20=
socket_events,=20NULL,=20NULL);=0A=20=0A=20=09/*=0A=20=09=20*=20We=20use=20=
a=20condition=20variable=20to=20efficiently=20wake=20up=20walsenders=20=
in=0A@@=20-3867,9=20+3868,6=20@@=20WalSndWait(uint32=20socket_events,=20=
long=20timeout,=20uint32=20wait_event)=0A=20=09=20*=20release=20for=20=
every=20iteration,=20just=20to=20wake=20up=20only=20the=20waiting=0A=20=09=
=20*=20walsenders.=20It=20makes=20WalSndWakeup()=20callers'=20life=20=
easy.=0A=20=09=20*=0A-=09=20*=20XXX:=20A=20desirable=20future=20=
improvement=20would=20be=20to=20add=20support=20for=20CVs=0A-=09=20*=20=
into=20WaitEventSetWait().=0A-=09=20*=0A=20=09=20*=20And,=20we=20use=20=
separate=20shared=20memory=20CVs=20for=20physical=20and=20logical=0A=20=09=
=20*=20walsenders=20for=20selective=20wake=20ups,=20see=20WalSndWakeup()=20=
for=20more=20details.=0A=20=09=20*=0A@@=20-3878,20=20+3876,19=20@@=20=
WalSndWait(uint32=20socket_events,=20long=20timeout,=20uint32=20=
wait_event)=0A=20=09=20*=20the=20receipt=20of=20the=20LSN.=0A=20=09=20*/=0A=
=20=09if=20(wait_event=20=3D=3D=20=
WAIT_EVENT_WAIT_FOR_STANDBY_CONFIRMATION)=0A-=09=09=
ConditionVariablePrepareToSleep(&WalSndCtl->wal_confirm_rcv_cv);=0A+=09=09=
cv=20=3D=20&WalSndCtl->wal_confirm_rcv_cv;=0A=20=09else=20if=20=
(MyWalSnd->kind=20=3D=3D=20REPLICATION_KIND_PHYSICAL)=0A-=09=09=
ConditionVariablePrepareToSleep(&WalSndCtl->wal_flush_cv);=0A+=09=09cv=20=
=3D=20&WalSndCtl->wal_flush_cv;=0A=20=09else=20if=20(MyWalSnd->kind=20=3D=3D=
=20REPLICATION_KIND_LOGICAL)=0A-=09=09=
ConditionVariablePrepareToSleep(&WalSndCtl->wal_replay_cv);=0A+=09=09cv=20=
=3D=20&WalSndCtl->wal_replay_cv;=0A+=0A+=09ModifyWaitEvent(FeBeWaitSet,=20=
FeBeWaitSetCVPos,=20WL_CONDITION_VARIABLE,=20NULL,=20cv);=0A=20=0A=20=09=
if=20(WaitEventSetWait(FeBeWaitSet,=20timeout,=20&event,=201,=20=
wait_event)=20=3D=3D=201=20&&=0A=20=09=09(event.events=20&=20=
WL_POSTMASTER_DEATH))=0A=20=09{=0A-=09=09ConditionVariableCancelSleep();=0A=
=20=09=09proc_exit(1);=0A=20=09}=0A-=0A-=09=
ConditionVariableCancelSleep();=0A=20}=0A=20=0A=20/*=0Adiff=20--git=20=
a/src/backend/storage/ipc/latch.c=20b/src/backend/storage/ipc/latch.c=0A=
index=208537e9fef2d..9b148d0f52b=20100644=0A---=20=
a/src/backend/storage/ipc/latch.c=0A+++=20=
b/src/backend/storage/ipc/latch.c=0A@@=20-41,7=20+41,7=20@@=20=
InitializeLatchWaitSet(void)=0A=20=09/*=20Set=20up=20the=20WaitEventSet=20=
used=20by=20WaitLatch().=20*/=0A=20=09LatchWaitSet=20=3D=20=
CreateWaitEventSet(NULL,=202);=0A=20=09latch_pos=20=3D=20=
AddWaitEventToSet(LatchWaitSet,=20WL_LATCH_SET,=20PGINVALID_SOCKET,=0A-=09=
=09=09=09=09=09=09=09=20=20MyLatch,=20NULL);=0A+=09=09=09=09=09=09=09=09=20=
=20MyLatch,=20NULL,=20NULL);=0A=20=09Assert(latch_pos=20=3D=3D=20=
LatchWaitSetLatchPos);=0A=20=0A=20=09/*=0A@@=20-51,7=20+51,7=20@@=20=
InitializeLatchWaitSet(void)=0A=20=09if=20(IsUnderPostmaster)=0A=20=09{=0A=
=20=09=09latch_pos=20=3D=20AddWaitEventToSet(LatchWaitSet,=20=
WL_EXIT_ON_PM_DEATH,=0A-=09=09=09=09=09=09=09=09=09=20=20=
PGINVALID_SOCKET,=20NULL,=20NULL);=0A+=09=09=09=09=09=09=09=09=09=20=20=
PGINVALID_SOCKET,=20NULL,=20NULL,=20NULL);=0A=20=09=09Assert(latch_pos=20=
=3D=3D=20LatchWaitSetPostmasterDeathPos);=0A=20=09}=0A=20}=0A@@=20=
-186,12=20+186,12=20@@=20WaitLatch(Latch=20*latch,=20int=20wakeEvents,=20=
long=20timeout,=0A=20=09=20*/=0A=20=09if=20(!(wakeEvents=20&=20=
WL_LATCH_SET))=0A=20=09=09latch=20=3D=20NULL;=0A-=09=
ModifyWaitEvent(LatchWaitSet,=20LatchWaitSetLatchPos,=20WL_LATCH_SET,=20=
latch);=0A+=09ModifyWaitEvent(LatchWaitSet,=20LatchWaitSetLatchPos,=20=
WL_LATCH_SET,=20latch,=20NULL);=0A=20=0A=20=09if=20(IsUnderPostmaster)=0A=
=20=09=09ModifyWaitEvent(LatchWaitSet,=20LatchWaitSetPostmasterDeathPos,=0A=
=20=09=09=09=09=09=09(wakeEvents=20&=20(WL_EXIT_ON_PM_DEATH=20|=20=
WL_POSTMASTER_DEATH)),=0A-=09=09=09=09=09=09NULL);=0A+=09=09=09=09=09=09=
NULL,=20NULL);=0A=20=0A=20=09if=20(WaitEventSetWait(LatchWaitSet,=0A=20=09=
=09=09=09=09=09=20(wakeEvents=20&=20WL_TIMEOUT)=20?=20timeout=20:=20-1,=0A=
@@=20-235,7=20+235,7=20@@=20WaitLatchOrSocket(Latch=20*latch,=20int=20=
wakeEvents,=20pgsocket=20sock,=0A=20=0A=20=09if=20(wakeEvents=20&=20=
WL_LATCH_SET)=0A=20=09=09AddWaitEventToSet(set,=20WL_LATCH_SET,=20=
PGINVALID_SOCKET,=0A-=09=09=09=09=09=09=20=20latch,=20NULL);=0A+=09=09=09=
=09=09=09=20=20latch,=20NULL,=20NULL);=0A=20=0A=20=09/*=20=
Postmaster-managed=20callers=20must=20handle=20postmaster=20death=20=
somehow.=20*/=0A=20=09Assert(!IsUnderPostmaster=20||=0A@@=20-244,18=20=
+244,18=20@@=20WaitLatchOrSocket(Latch=20*latch,=20int=20wakeEvents,=20=
pgsocket=20sock,=0A=20=0A=20=09if=20((wakeEvents=20&=20=
WL_POSTMASTER_DEATH)=20&&=20IsUnderPostmaster)=0A=20=09=09=
AddWaitEventToSet(set,=20WL_POSTMASTER_DEATH,=20PGINVALID_SOCKET,=0A-=09=09=
=09=09=09=09=20=20NULL,=20NULL);=0A+=09=09=09=09=09=09=20=20NULL,=20=
NULL,=20NULL);=0A=20=0A=20=09if=20((wakeEvents=20&=20=
WL_EXIT_ON_PM_DEATH)=20&&=20IsUnderPostmaster)=0A=20=09=09=
AddWaitEventToSet(set,=20WL_EXIT_ON_PM_DEATH,=20PGINVALID_SOCKET,=0A-=09=09=
=09=09=09=09=20=20NULL,=20NULL);=0A+=09=09=09=09=09=09=20=20NULL,=20=
NULL,=20NULL);=0A=20=0A=20=09if=20(wakeEvents=20&=20WL_SOCKET_MASK)=0A=20=
=09{=0A=20=09=09int=09=09=09ev;=0A=20=0A=20=09=09ev=20=3D=20wakeEvents=20=
&=20WL_SOCKET_MASK;=0A-=09=09AddWaitEventToSet(set,=20ev,=20sock,=20=
NULL,=20NULL);=0A+=09=09AddWaitEventToSet(set,=20ev,=20sock,=20NULL,=20=
NULL,=20NULL);=0A=20=09}=0A=20=0A=20=09rc=20=3D=20WaitEventSetWait(set,=20=
timeout,=20&event,=201,=20wait_event_info);=0Adiff=20--git=20=
a/src/backend/storage/ipc/waiteventset.c=20=
b/src/backend/storage/ipc/waiteventset.c=0Aindex=20=
0f228e1e7b8..2382e0cae2a=20100644=0A---=20=
a/src/backend/storage/ipc/waiteventset.c=0A+++=20=
b/src/backend/storage/ipc/waiteventset.c=0A@@=20-73,6=20+73,7=20@@=0A=20=
#include=20"storage/fd.h"=0A=20#include=20"storage/ipc.h"=0A=20#include=20=
"storage/pmsignal.h"=0A+#include=20"storage/condition_variable.h"=0A=20=
#include=20"storage/latch.h"=0A=20#include=20"storage/waiteventset.h"=0A=20=
#include=20"utils/memutils.h"=0A@@=20-137,6=20+138,15=20@@=20struct=20=
WaitEventSet=0A=20=09Latch=09=20=20=20*latch;=0A=20=09int=09=09=09=
latch_pos;=0A=20=0A+=09/*=0A+=09=20*=20If=20WL_CONDITION_VARIABLE=20is=20=
specified=20in=20any=20wait=20event,=20cv=20is=20a=0A+=09=20*=20pointer=20=
to=20said=20condition=20variable,=20and=20cv_pos=20the=20offset=20in=20=
the=0A+=09=20*=20->events=20array.=0A+=09=20*/=0A+=09ConditionVariable=20=
*cv;=0A+=09int=09=09=09cv_pos;=0A+=09bool=09=09cv_maybe_signaled;=09/*=20=
Decide=20if=20check=20signaled=20after=20poll=20*/=0A+=0A=20=09/*=0A=20=09=
=20*=20WL_EXIT_ON_PM_DEATH=20is=20converted=20to=20WL_POSTMASTER_DEATH,=20=
but=20this=20flag=0A=20=09=20*=20is=20set=20so=20that=20we'll=20exit=20=
immediately=20if=20postmaster=20death=20is=20detected,=0A@@=20-414,6=20=
+424,8=20@@=20CreateWaitEventSet(ResourceOwner=20resowner,=20int=20=
nevents)=0A=20#endif=0A=20=0A=20=09set->latch=20=3D=20NULL;=0A+=09=
set->cv=20=3D=20NULL;=0A+=09set->cv_maybe_signaled=20=3D=20false;=0A=20=09=
set->nevents_space=20=3D=20nevents;=0A=20=09=
set->exit_on_postmaster_death=20=3D=20false;=0A=20=0A@@=20-550,6=20=
+562,7=20@@=20FreeWaitEventSetAfterFork(WaitEventSet=20*set)=0A=20=20*=09=
=20platforms,=20this=20is=20the=20same=20as=20WL_SOCKET_READABLE)=0A=20=20=
*=20-=20WL_SOCKET_CLOSED:=20Wait=20for=20socket=20to=20be=20closed=20by=20=
remote=20peer.=0A=20=20*=20-=20WL_EXIT_ON_PM_DEATH:=20Exit=20immediately=20=
if=20the=20postmaster=20dies=0A+=20*=20-=20WL_CONDITION_VARIABLE:=20Wait=20=
for=20a=20condition=20variable=20to=20be=20signaled.=0A=20=20*=0A=20=20*=20=
Returns=20the=20offset=20in=20WaitEventSet->events=20(starting=20from=20=
0),=20which=20can=20be=0A=20=20*=20used=20to=20modify=20previously=20=
added=20wait=20events=20using=20ModifyWaitEvent().=0A@@=20-568,7=20=
+581,7=20@@=20FreeWaitEventSetAfterFork(WaitEventSet=20*set)=0A=20=20*/=0A=
=20int=0A=20AddWaitEventToSet(WaitEventSet=20*set,=20uint32=20events,=20=
pgsocket=20fd,=20Latch=20*latch,=0A-=09=09=09=09=20=20void=20*user_data)=0A=
+=09=09=09=09=20=20ConditionVariable=20*cv,=20void=20*user_data)=0A=20{=0A=
=20=09WaitEvent=20=20*event;=0A=20=0A@@=20-596,6=20+609,18=20@@=20=
AddWaitEventToSet(WaitEventSet=20*set,=20uint32=20events,=20pgsocket=20=
fd,=20Latch=20*latch,=0A=20=09=09=09elog(ERROR,=20"cannot=20wait=20on=20=
latch=20without=20a=20specified=20latch");=0A=20=09}=0A=20=0A+=09/*=0A+=09=
=20*=20When=20add=20a=20CV=20event,=20we=20allow=20a=20NULL=20cv,=20=
because=20it=20can=20be=20set=20later=0A+=09=20*=20with=20=
ModifyWaitEvent.=0A+=09=20*/=0A+=09if=20(cv)=0A+=09{=0A+=09=09if=20=
(set->cv)=0A+=09=09=09elog(ERROR,=20"cannot=20wait=20on=20more=20than=20=
one=20condition=20variable");=0A+=09=09if=20((events=20&=20=
WL_CONDITION_VARIABLE)=20!=3D=20WL_CONDITION_VARIABLE)=0A+=09=09=09=
elog(ERROR,=20"condition=20variable=20events=20only=20support=20being=20=
set");=0A+=09}=0A+=0A=20=09/*=20waiting=20for=20socket=20readiness=20=
without=20a=20socket=20indicates=20a=20bug=20*/=0A=20=09if=20(fd=20=3D=3D=20=
PGINVALID_SOCKET=20&&=20(events=20&=20WL_SOCKET_MASK))=0A=20=09=09=
elog(ERROR,=20"cannot=20wait=20on=20socket=20event=20without=20a=20=
socket");=0A@@=20-624,6=20+649,13=20@@=20AddWaitEventToSet(WaitEventSet=20=
*set,=20uint32=20events,=20pgsocket=20fd,=20Latch=20*latch,=0A=20#endif=0A=
=20#endif=0A=20=09}=0A+=09else=20if=20(events=20=3D=3D=20=
WL_CONDITION_VARIABLE)=0A+=09{=0A+=09=09set->cv=20=3D=20cv;=0A+=09=09=
set->cv_pos=20=3D=20event->pos;=0A+=09=09event->fd=20=3D=20=
PGINVALID_SOCKET;=0A+=09=09return=20event->pos;=0A+=09}=0A=20=09else=20=
if=20(events=20=3D=3D=20WL_POSTMASTER_DEATH)=0A=20=09{=0A=20#ifndef=20=
WIN32=0A@@=20-653,14=20+685,15=20@@=20AddWaitEventToSet(WaitEventSet=20=
*set,=20uint32=20events,=20pgsocket=20fd,=20Latch=20*latch,=0A=20=20*=20=
'pos'=20is=20the=20id=20returned=20by=20AddWaitEventToSet.=0A=20=20*/=0A=20=
void=0A-ModifyWaitEvent(WaitEventSet=20*set,=20int=20pos,=20uint32=20=
events,=20Latch=20*latch)=0A+ModifyWaitEvent(WaitEventSet=20*set,=20int=20=
pos,=20uint32=20events,=20Latch=20*latch,=0A+=09=09=09=09=
ConditionVariable=20*cv)=0A=20{=0A=20=09WaitEvent=20=20*event;=0A=20#if=20=
defined(WAIT_USE_KQUEUE)=0A=20=09int=09=09=09old_events;=0A=20#endif=0A=20=
=0A-=09Assert(pos=20<=20set->nevents);=0A+=09Assert(pos=20>=3D=200=20&&=20=
pos=20<=20set->nevents);=0A=20=0A=20=09event=20=3D=20&set->events[pos];=0A=
=20#if=20defined(WAIT_USE_KQUEUE)=0A@@=20-682,6=20+715,21=20@@=20=
ModifyWaitEvent(WaitEventSet=20*set,=20int=20pos,=20uint32=20events,=20=
Latch=20*latch)=0A=20=09=09return;=0A=20=09}=0A=20=0A+=09/*=0A+=09=20*=20=
Change=20the=20condition=20variable=20associated=20with=20the=20event.=20=
=20As=20CV=20doesn't=0A+=09=20*=20rely=20on=20kernal,=20go=20ahead=20=
with=20a=20fast-path=20and=20only=20update=20the=20CV=0A+=09=20*=20=
pointer.=0A+=09=20*/=0A+=09if=20(event->events=20=3D=3D=20=
WL_CONDITION_VARIABLE)=0A+=09{=0A+=09=09if=20(events=20!=3D=20=
WL_CONDITION_VARIABLE)=0A+=09=09=09elog(ERROR,=20"cannot=20change=20=
event=20type=20of=20a=20condition=20variable=20event");=0A+=09=09if=20=
(cv=20=3D=3D=20NULL)=0A+=09=09=09elog(ERROR,=20"cannot=20set=20condition=20=
variable=20to=20NULL");=0A+=09=09set->cv=20=3D=20cv;=0A+=09=09return;=0A=
+=09}=0A+=0A=20=09/*=0A=20=09=20*=20If=20neither=20the=20event=20mask=20=
nor=20the=20associated=20latch=20changes,=20return=0A=20=09=20*=20early.=20=
That's=20an=20important=20optimization=20for=20some=20sockets,=20where=0A=
@@=20-1042,9=20+1090,11=20@@=20WaitEventSetWait(WaitEventSet=20*set,=20=
long=20timeout,=0A=20=09=09=09=09=20uint32=20wait_event_info)=0A=20{=0A=20=
=09int=09=09=09returned_events=20=3D=200;=0A+=09WaitEvent=20=20=
*first_occurred_event=20=3D=20occurred_events;=0A=20=09instr_time=09=
start_time;=0A=20=09instr_time=09cur_time;=0A=20=09long=09=09cur_timeout=20=
=3D=20-1;=0A+=09bool=09=09cv_signaled=20=3D=20false;=0A=20=0A=20=09=
Assert(nevents=20>=200);=0A=20=0A@@=20-1061,6=20+1111,9=20@@=20=
WaitEventSetWait(WaitEventSet=20*set,=20long=20timeout,=0A=20=09else=0A=20=
=09=09INSTR_TIME_SET_ZERO(start_time);=0A=20=0A+=09if=20(set->cv=20!=3D=20=
NULL)=0A+=09=09ConditionVariablePrepareToSleep(set->cv);=0A+=0A=20=09=
pgstat_report_wait_start(wait_event_info);=0A=20=0A=20#ifndef=20WIN32=0A=
@@=20-1072,6=20+1125,7=20@@=20WaitEventSetWait(WaitEventSet=20*set,=20=
long=20timeout,=0A=20=09while=20(returned_events=20=3D=3D=200)=0A=20=09{=0A=
=20=09=09int=09=09=09rc;=0A+=09=09WaitEvent=20=20*block_occurred_events=20=
=3D=20occurred_events;=0A=20=0A=20=09=09/*=0A=20=09=09=20*=20Check=20if=20=
the=20latch=20is=20set=20already=20first.=20=20If=20so,=20we=20either=20=
exit=0A@@=20-1115,6=20+1169,7=20@@=20WaitEventSetWait(WaitEventSet=20=
*set,=20long=20timeout,=0A=20=09=09=09occurred_events->user_data=20=3D=0A=
=20=09=09=09=09set->events[set->latch_pos].user_data;=0A=20=09=09=09=
occurred_events->events=20=3D=20WL_LATCH_SET;=0A+=0A=20=09=09=09=
occurred_events++;=0A=20=09=09=09returned_events++;=0A=20=0A@@=20-1133,6=20=
+1188,38=20@@=20WaitEventSetWait(WaitEventSet=20*set,=20long=20timeout,=0A=
=20=09=09=09timeout=20=3D=200;=0A=20=09=09}=0A=20=0A+=09=09if=20=
(set->cv)=0A+=09=09=09cv_signaled=20=3D=20=
ConditionVariableSignaled(set->cv);=0A+=0A+=09=09if=20(set->cv=20&&=20=
!cv_signaled)=0A+=09=09=09set->cv_maybe_signaled=20=3D=20true;=0A+=0A+=09=
=09if=20(set->cv=20&&=20cv_signaled)=0A+=09=09{=0A+=09=09=09=
occurred_events->fd=20=3D=20PGINVALID_SOCKET;=0A+=09=09=09=
occurred_events->pos=20=3D=20set->cv_pos;=0A+=09=09=09=
occurred_events->user_data=20=3D=0A+=09=09=09=09=
set->events[set->cv_pos].user_data;=0A+=09=09=09occurred_events->events=20=
=3D=20WL_CONDITION_VARIABLE;=0A+=0A+=09=09=09occurred_events++;=0A+=09=09=
=09returned_events++;=0A+=0A+=09=09=09/*=20could=20have=20been=20set=20=
above=20*/=0A+=09=09=09set->cv_maybe_signaled=20=3D=20false;=0A+=0A+=09=09=
=09if=20(returned_events=20=3D=3D=20nevents)=0A+=09=09=09=09break;=09=09=09=
/*=20output=20buffer=20full=20already=20*/=0A+=0A+=09=09=09/*=0A+=09=09=09=
=20*=20Even=20though=20we=20already=20have=20an=20event,=20we'll=20poll=20=
just=20once=20with=0A+=09=09=09=20*=20zero=20timeout=20to=20see=20what=20=
non-latch=20events=20we=20can=20fit=20into=20the=0A+=09=09=09=20*=20=
output=20buffer=20at=20the=20same=20time.=0A+=09=09=09=20*/=0A+=09=09=09=
cur_timeout=20=3D=200;=0A+=09=09=09timeout=20=3D=200;=0A+=09=09}=0A+=0A=20=
=09=09/*=0A=20=09=09=20*=20Wait=20for=20events=20using=20the=20readiness=20=
primitive=20chosen=20at=20the=20top=20of=0A=20=09=09=20*=20this=20file.=20=
If=20-1=20is=20returned,=20a=20timeout=20has=20occurred,=20if=200=20we=20=
have=0A@@=20-1145,6=20+1232,25=20@@=20WaitEventSetWait(WaitEventSet=20=
*set,=20long=20timeout,=0A=20=09=09=09set->latch->maybe_sleeping)=0A=20=09=
=09=09set->latch->maybe_sleeping=20=3D=20false;=0A=20=0A+=09=09/*=20=
Check=20CV=20again=20after=20waiting=20if=20not=20done=20before=20=
waiting=20*/=0A+=09=09if=20(set->cv=20&&=20set->cv_maybe_signaled=20&&=20=
ConditionVariableSignaled(set->cv))=0A+=09=09{=0A+=09=09=09=
occurred_events->fd=20=3D=20PGINVALID_SOCKET;=0A+=09=09=09=
occurred_events->pos=20=3D=20set->cv_pos;=0A+=09=09=09=
occurred_events->user_data=20=3D=0A+=09=09=09=09=
set->events[set->cv_pos].user_data;=0A+=09=09=09occurred_events->events=20=
=3D=20WL_CONDITION_VARIABLE;=0A+=0A+=09=09=09occurred_events++;=0A+=09=09=
=09returned_events++;=0A+=0A+=09=09=09if=20(returned_events=20=3D=3D=20=
nevents)=0A+=09=09=09=09break;=09=09=09/*=20output=20buffer=20full=20=
already=20*/=0A+=09=09}=0A+=0A+=09=09if=20(set->cv=20&&=20=
set->cv_maybe_signaled)=0A+=09=09=09set->cv_maybe_signaled=20=3D=20=
false;=0A+=0A=20=09=09if=20(rc=20=3D=3D=20-1)=0A=20=09=09=09break;=09=09=09=
=09/*=20timeout=20occurred=20*/=0A=20=09=09else=0A@@=20-1166,10=20=
+1272,12=20@@=20WaitEventSetWait(WaitEventSet=20*set,=20long=20timeout,=0A=
=20=0A=20=09pgstat_report_wait_end();=0A=20=0A+=09if=20(set->cv=20!=3D=20=
NULL)=0A+=09=09ConditionVariableCancelSleep();=0A+=0A=20=09return=20=
returned_events;=0A=20}=0A=20=0A-=0A=20#if=20defined(WAIT_USE_EPOLL)=0A=20=
=0A=20/*=0Adiff=20--git=20=
a/src/backend/storage/lmgr/condition_variable.c=20=
b/src/backend/storage/lmgr/condition_variable.c=0Aindex=20=
1f16b3f7475..c04bc420bcf=20100644=0A---=20=
a/src/backend/storage/lmgr/condition_variable.c=0A+++=20=
b/src/backend/storage/lmgr/condition_variable.c=0A@@=20-182,13=20+182,7=20=
@@=20ConditionVariableTimedSleep(ConditionVariable=20*cv,=20long=20=
timeout,=0A=20=09=09=20*=20by=20something=20other=20than=20=
ConditionVariableSignal;=20though=20we=20don't=0A=20=09=09=20*=20=
guarantee=20not=20to=20return=20spuriously,=20we'll=20avoid=20this=20=
obvious=20case.=0A=20=09=09=20*/=0A-=09=09SpinLockAcquire(&cv->mutex);=0A=
-=09=09if=20(!proclist_contains(&cv->wakeup,=20MyProcNumber,=20=
cvWaitLink))=0A-=09=09{=0A-=09=09=09done=20=3D=20true;=0A-=09=09=09=
proclist_push_tail(&cv->wakeup,=20MyProcNumber,=20cvWaitLink);=0A-=09=09=
}=0A-=09=09SpinLockRelease(&cv->mutex);=0A+=09=09done=20=3D=20=
ConditionVariableSignaled(cv);=0A=20=0A=20=09=09/*=0A=20=09=09=20*=20=
Check=20for=20interrupts,=20and=20return=20spuriously=20if=20that=20=
caused=20the=0A@@=20-217,6=20+211,31=20@@=20=
ConditionVariableTimedSleep(ConditionVariable=20*cv,=20long=20timeout,=0A=
=20=09}=0A=20}=0A=20=0A+/*=0A+=20*=20Check=20whether=20this=20process=20=
was=20removed=20from=20cv's=20wait=20list=20by=20a=20CV=0A+=20*=20=
signal/broadcast.=20If=20so,=20re-add=20it=20to=20preserve=20wakeups=20=
while=20the=20caller=0A+=20*=20checks=20the=20predicate.=0A+=20*/=0A=
+bool=0A+ConditionVariableSignaled(ConditionVariable=20*cv)=0A+{=0A+=09=
bool=09=09signaled=20=3D=20false;=0A+=0A+=09/*=20Ignore=20probes=20for=20=
CVs=20we=20are=20not=20currently=20prepared=20to=20sleep=20on.=20*/=0A+=09=
if=20(cv_sleep_target=20!=3D=20cv)=0A+=09=09return=20false;=0A+=0A+=09=
SpinLockAcquire(&cv->mutex);=0A+=09if=20(!proclist_contains(&cv->wakeup,=20=
MyProcNumber,=20cvWaitLink))=0A+=09{=0A+=09=09signaled=20=3D=20true;=0A+=09=
=09proclist_push_tail(&cv->wakeup,=20MyProcNumber,=20cvWaitLink);=0A+=09=
}=0A+=09SpinLockRelease(&cv->mutex);=0A+=0A+=09return=20signaled;=0A+}=0A=
+=0A=20/*=0A=20=20*=20Cancel=20any=20pending=20sleep=20operation.=0A=20=20=
*=0Adiff=20--git=20a/src/backend/utils/init/miscinit.c=20=
b/src/backend/utils/init/miscinit.c=0Aindex=20ba191977697..b970c1d727c=20=
100644=0A---=20a/src/backend/utils/init/miscinit.c=0A+++=20=
b/src/backend/utils/init/miscinit.c=0A@@=20-222,7=20+222,7=20@@=20=
SwitchToSharedLatch(void)=0A=20=0A=20=09if=20(FeBeWaitSet)=0A=20=09=09=
ModifyWaitEvent(FeBeWaitSet,=20FeBeWaitSetLatchPos,=20WL_LATCH_SET,=0A-=09=
=09=09=09=09=09MyLatch);=0A+=09=09=09=09=09=09MyLatch,=20NULL);=0A=20=0A=20=
=09/*=0A=20=09=20*=20Set=20the=20shared=20latch=20as=20the=20local=20one=20=
might=20have=20been=20set.=20This=0A@@=20-249,7=20+249,7=20@@=20=
SwitchBackToLocalLatch(void)=0A=20=0A=20=09if=20(FeBeWaitSet)=0A=20=09=09=
ModifyWaitEvent(FeBeWaitSet,=20FeBeWaitSetLatchPos,=20WL_LATCH_SET,=0A-=09=
=09=09=09=09=09MyLatch);=0A+=09=09=09=09=09=09MyLatch,=20NULL);=0A=20=0A=20=
=09SetLatch(MyLatch);=0A=20}=0Adiff=20--git=20=
a/src/include/libpq/libpq.h=20b/src/include/libpq/libpq.h=0Aindex=20=
c9b934d2321..8d13eaf8393=20100644=0A---=20a/src/include/libpq/libpq.h=0A=
+++=20b/src/include/libpq/libpq.h=0A@@=20-65,7=20+65,8=20@@=20extern=20=
PGDLLIMPORT=20WaitEventSet=20*FeBeWaitSet;=0A=20=0A=20#define=20=
FeBeWaitSetSocketPos=200=0A=20#define=20FeBeWaitSetLatchPos=201=0A=
-#define=20FeBeWaitSetNEvents=203=0A+#define=20FeBeWaitSetCVPos=202=0A=
+#define=20FeBeWaitSetNEvents=204=0A=20=0A=20extern=20int=09=
ListenServerPort(int=20family,=20const=20char=20*hostName,=0A=20=09=09=09=
=09=09=09=09=20unsigned=20short=20portNumber,=20const=20char=20=
*unixSocketDir,=0Adiff=20--git=20=
a/src/include/storage/condition_variable.h=20=
b/src/include/storage/condition_variable.h=0Aindex=20=
14bd6dd55c0..fb7e4bb67f2=20100644=0A---=20=
a/src/include/storage/condition_variable.h=0A+++=20=
b/src/include/storage/condition_variable.h=0A@@=20-57,6=20+57,7=20@@=20=
extern=20void=20ConditionVariableSleep(ConditionVariable=20*cv,=20uint32=20=
wait_event_info=0A=20extern=20bool=20=
ConditionVariableTimedSleep(ConditionVariable=20*cv,=20long=20timeout,=0A=
=20=09=09=09=09=09=09=09=09=09=09uint32=20wait_event_info);=0A=20extern=20=
bool=20ConditionVariableCancelSleep(void);=0A+extern=20bool=20=
ConditionVariableSignaled(ConditionVariable=20*cv);=0A=20=0A=20/*=0A=20=20=
*=20Optionally,=20ConditionVariablePrepareToSleep=20can=20be=20called=20=
before=20entering=0Adiff=20--git=20a/src/include/storage/waiteventset.h=20=
b/src/include/storage/waiteventset.h=0Aindex=205341267f0a0..f3d569a6aa0=20=
100644=0A---=20a/src/include/storage/waiteventset.h=0A+++=20=
b/src/include/storage/waiteventset.h=0A@@=20-25,6=20+25,7=20@@=0A=20=
#ifndef=20WAITEVENTSET_H=0A=20#define=20WAITEVENTSET_H=0A=20=0A+#include=20=
"storage/condition_variable.h"=0A=20#include=20"utils/resowner.h"=0A=20=0A=
=20/*=0A@@=20-50,6=20+51,7=20@@=0A=20/*=20avoid=20having=20to=20deal=20=
with=20case=20on=20platforms=20not=20requiring=20it=20*/=0A=20#define=20=
WL_SOCKET_ACCEPT=09WL_SOCKET_READABLE=0A=20#endif=0A+#define=20=
WL_CONDITION_VARIABLE=20(1=20<<=209)=0A=20#define=20WL_SOCKET_MASK=09=09=
(WL_SOCKET_READABLE=20|=20\=0A=20=09=09=09=09=09=09=09=20=
WL_SOCKET_WRITEABLE=20|=20\=0A=20=09=09=09=09=09=09=09=20=
WL_SOCKET_CONNECTED=20|=20\=0A@@=20-81,9=20+83,10=20@@=20extern=20=
WaitEventSet=20*CreateWaitEventSet(ResourceOwner=20resowner,=20int=20=
nevents);=0A=20extern=20void=20FreeWaitEventSet(WaitEventSet=20*set);=0A=20=
extern=20void=20FreeWaitEventSetAfterFork(WaitEventSet=20*set);=0A=20=
extern=20int=09AddWaitEventToSet(WaitEventSet=20*set,=20uint32=20events,=20=
pgsocket=20fd,=0A-=09=09=09=09=09=09=09=20=20struct=20Latch=20*latch,=20=
void=20*user_data);=0A+=09=09=09=09=09=09=09=20=20struct=20Latch=20=
*latch,=20ConditionVariable=20*cv,=0A+=09=09=09=09=09=09=09=20=20void=20=
*user_data);=0A=20extern=20void=20ModifyWaitEvent(WaitEventSet=20*set,=20=
int=20pos,=20uint32=20events,=0A-=09=09=09=09=09=09=09struct=20Latch=20=
*latch);=0A+=09=09=09=09=09=09=09struct=20Latch=20*latch,=20=
ConditionVariable=20*cv);=0A=20extern=20int=09=
WaitEventSetWait(WaitEventSet=20*set,=20long=20timeout,=0A=20=09=09=09=09=
=09=09=09=20WaitEvent=20*occurred_events,=20int=20nevents,=0A=20=09=09=09=
=09=09=09=09=20uint32=20wait_event_info);=0A--=20=0A2.50.1=20(Apple=20=
Git-155)=0A=0A=

--Apple-Mail=_4A17D358-3B20-427B-9DDC-057D3AC4DFDC--