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Commita5fe473

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Minor cleanup for access/transam/parallel.c.
ParallelMessagePending *must* be marked volatile, because it's setby a signal handler. On the other hand, it's pointless forHandleParallelMessageInterrupt to save/restore errno; that must be,and is, done at the outer level of the SIGUSR1 signal handler.Calling CHECK_FOR_INTERRUPTS() inside HandleParallelMessages, which itselfis called from CHECK_FOR_INTERRUPTS(), seems both useless and hazardous.The comment claiming that this is needed to handle the error queue goingaway is certainly misguided, in any case.Improve a couple of error message texts, and useERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE to report loss of parallel workerconnection, since that's what's used in e.g. tqueue.c. (Maybe it would beworth inventing a dedicated ERRCODE for this type of failure? But I do notthink ERRCODE_INTERNAL_ERROR is appropriate.)Minor stylistic cleanups.
1 parent887feef commita5fe473

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2 files changed

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-20
lines changed

2 files changed

+18
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lines changed

‎src/backend/access/transam/parallel.c

Lines changed: 12 additions & 13 deletions
Original file line numberDiff line numberDiff line change
@@ -14,9 +14,9 @@
1414

1515
#include"postgres.h"
1616

17+
#include"access/parallel.h"
1718
#include"access/xact.h"
1819
#include"access/xlog.h"
19-
#include"access/parallel.h"
2020
#include"catalog/namespace.h"
2121
#include"commands/async.h"
2222
#include"libpq/libpq.h"
@@ -35,6 +35,7 @@
3535
#include"utils/resowner.h"
3636
#include"utils/snapmgr.h"
3737

38+
3839
/*
3940
* We don't want to waste a lot of memory on an error queue which, most of
4041
* the time, will process only a handful of small messages. However, it is
@@ -94,7 +95,7 @@ typedef struct FixedParallelState
9495
intParallelWorkerNumber=-1;
9596

9697
/* Is there a parallel message pending which we need to receive? */
97-
boolParallelMessagePending= false;
98+
volatileboolParallelMessagePending= false;
9899

99100
/* Are we initializing a parallel worker? */
100101
boolInitializingParallelWorker= false;
@@ -106,12 +107,13 @@ static FixedParallelState *MyFixedParallelState;
106107
staticdlist_headpcxt_list=DLIST_STATIC_INIT(pcxt_list);
107108

108109
/* Private functions. */
109-
staticvoidHandleParallelMessage(ParallelContext*,int,StringInfomsg);
110+
staticvoidHandleParallelMessage(ParallelContext*pcxt,inti,StringInfomsg);
110111
staticvoidParallelErrorContext(void*arg);
111112
staticvoidParallelExtensionTrampoline(dsm_segment*seg,shm_toc*toc);
112113
staticvoidParallelWorkerMain(Datummain_arg);
113114
staticvoidWaitForParallelWorkersToExit(ParallelContext*pcxt);
114115

116+
115117
/*
116118
* Establish a new parallel context. This should be done after entering
117119
* parallel mode, and (unless there is an error) the context should be
@@ -681,17 +683,17 @@ ParallelContextActive(void)
681683

682684
/*
683685
* Handle receipt of an interrupt indicating a parallel worker message.
686+
*
687+
* Note: this is called within a signal handler! All we can do is set
688+
* a flag that will cause the next CHECK_FOR_INTERRUPTS() to invoke
689+
* HandleParallelMessages().
684690
*/
685691
void
686692
HandleParallelMessageInterrupt(void)
687693
{
688-
intsave_errno=errno;
689-
690694
InterruptPending= true;
691695
ParallelMessagePending= true;
692696
SetLatch(MyLatch);
693-
694-
errno=save_errno;
695697
}
696698

697699
/*
@@ -742,11 +744,8 @@ HandleParallelMessages(void)
742744
}
743745
else
744746
ereport(ERROR,
745-
(errcode(ERRCODE_INTERNAL_ERROR),/* XXX: wrong errcode? */
746-
errmsg("lost connection to parallel worker")));
747-
748-
/* This might make the error queue go away. */
749-
CHECK_FOR_INTERRUPTS();
747+
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
748+
errmsg("lost connection to parallel worker")));
750749
}
751750
}
752751
}
@@ -833,7 +832,7 @@ HandleParallelMessage(ParallelContext *pcxt, int i, StringInfo msg)
833832

834833
default:
835834
{
836-
elog(ERROR,"unknown message type: %c (%d bytes)",
835+
elog(ERROR,"unrecognized message type received from parallel worker: %c (message length%d bytes)",
837836
msgtype,msg->len);
838837
}
839838
}

‎src/include/access/parallel.h

Lines changed: 6 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -19,7 +19,6 @@
1919
#include"postmaster/bgworker.h"
2020
#include"storage/shm_mq.h"
2121
#include"storage/shm_toc.h"
22-
#include"utils/elog.h"
2322

2423
typedefvoid (*parallel_worker_main_type) (dsm_segment*seg,shm_toc*toc);
2524

@@ -47,25 +46,25 @@ typedef struct ParallelContext
4746
ParallelWorkerInfo*worker;
4847
}ParallelContext;
4948

50-
externboolParallelMessagePending;
49+
externvolatileboolParallelMessagePending;
5150
externintParallelWorkerNumber;
5251
externboolInitializingParallelWorker;
5352

5453
#defineIsParallelWorker()(ParallelWorkerNumber >= 0)
5554

5655
externParallelContext*CreateParallelContext(parallel_worker_main_typeentrypoint,intnworkers);
5756
externParallelContext*CreateParallelContextForExternalFunction(char*library_name,char*function_name,intnworkers);
58-
externvoidInitializeParallelDSM(ParallelContext*);
57+
externvoidInitializeParallelDSM(ParallelContext*pcxt);
5958
externvoidReinitializeParallelDSM(ParallelContext*pcxt);
60-
externvoidLaunchParallelWorkers(ParallelContext*);
61-
externvoidWaitForParallelWorkersToFinish(ParallelContext*);
62-
externvoidDestroyParallelContext(ParallelContext*);
59+
externvoidLaunchParallelWorkers(ParallelContext*pcxt);
60+
externvoidWaitForParallelWorkersToFinish(ParallelContext*pcxt);
61+
externvoidDestroyParallelContext(ParallelContext*pcxt);
6362
externboolParallelContextActive(void);
6463

6564
externvoidHandleParallelMessageInterrupt(void);
6665
externvoidHandleParallelMessages(void);
6766
externvoidAtEOXact_Parallel(boolisCommit);
6867
externvoidAtEOSubXact_Parallel(boolisCommit,SubTransactionIdmySubId);
69-
externvoidParallelWorkerReportLastRecEnd(XLogRecPtr);
68+
externvoidParallelWorkerReportLastRecEnd(XLogRecPtrlast_xlog_end);
7069

7170
#endif/* PARALLEL_H */

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