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Commitee3f8d3

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pgstat: Bring up pgstat in BaseInit() to fix uninitialized use of pgstat by AV.
Previously pgstat_initialize() was called in InitPostgres() andAuxiliaryProcessMain(). As it turns out there was at least one case where wereported stats before pgstat_initialize() was called, seeAutoVacWorkerMain()'s intentionally early call to pgstat_report_autovac().This turns out to not be a problem with the current pgstat implementation aspgstat_initialize() only registers a shutdown callback. But in the sharedmemory based stats implementation we are working towards pgstat_initialize()has to do more work.Afterb406478 BaseInit() is a central place where initialization shared bynormal backends and auxiliary backends can be put. Obviously BaseInit() iscalled before InitPostgres() registers ShutdownPostgres. PreviouslyShutdownPostgres was the first before_shmem_exit callback, now that's commonlypgstats. That should be fine.Previously pgstat_initialize() was not called in bootstrap mode, but theredoes not appear to be a need for that. It's now done unconditionally.To detect future issues like this, assertions are added to a few placesverifying that the pgstat subsystem is initialized and not yet shut down.Author: Andres Freund <andres@anarazel.de>Discussion:https://postgr.es/m/20210405092914.mmxqe7j56lsjfsej@alap3.anarazel.deDiscussion:https://postgr.es/m/20210802164124.ufo5buo4apl6yuvs@alap3.anarazel.de
1 parent5c056b0 commitee3f8d3

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3 files changed

+65
-13
lines changed

3 files changed

+65
-13
lines changed

‎src/backend/postmaster/auxprocess.c‎

Lines changed: 0 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -125,8 +125,6 @@ AuxiliaryProcessMain(AuxProcType auxtype)
125125
*/
126126
CreateAuxProcessResourceOwner();
127127

128-
/* Initialize statistics reporting */
129-
pgstat_initialize();
130128

131129
/* Initialize backend status information */
132130
pgstat_beinit();

‎src/backend/postmaster/pgstat.c‎

Lines changed: 51 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -295,6 +295,15 @@ static List *pending_write_requests = NIL;
295295
*/
296296
staticinstr_timetotal_func_time;
297297

298+
/*
299+
* For assertions that check pgstat is not used before initialization / after
300+
* shutdown.
301+
*/
302+
#ifdefUSE_ASSERT_CHECKING
303+
staticboolpgstat_is_initialized= false;
304+
staticboolpgstat_is_shutdown= false;
305+
#endif
306+
298307

299308
/* ----------
300309
* Local function forward declarations
@@ -330,6 +339,7 @@ static void pgstat_send_connstats(bool disconnect, TimestampTz last_report);
330339
staticPgStat_TableStatus*get_tabstat_entry(Oidrel_id,boolisshared);
331340

332341
staticvoidpgstat_setup_memcxt(void);
342+
staticvoidpgstat_assert_is_up(void);
333343

334344
staticvoidpgstat_setheader(PgStat_MsgHdr*hdr,StatMsgTypemtype);
335345
staticvoidpgstat_send(void*msg,intlen);
@@ -854,6 +864,8 @@ pgstat_report_stat(bool disconnect)
854864
TabStatusArray*tsa;
855865
inti;
856866

867+
pgstat_assert_is_up();
868+
857869
/*
858870
* Don't expend a clock check if nothing to do.
859871
*
@@ -1960,6 +1972,8 @@ pgstat_init_function_usage(FunctionCallInfo fcinfo,
19601972
PgStat_BackendFunctionEntry*
19611973
find_funcstat_entry(Oidfunc_id)
19621974
{
1975+
pgstat_assert_is_up();
1976+
19631977
if (pgStatFunctions==NULL)
19641978
returnNULL;
19651979

@@ -2078,6 +2092,8 @@ get_tabstat_entry(Oid rel_id, bool isshared)
20782092
TabStatusArray*tsa;
20792093
boolfound;
20802094

2095+
pgstat_assert_is_up();
2096+
20812097
/*
20822098
* Create hash table if we don't have it already.
20832099
*/
@@ -2938,6 +2954,8 @@ pgstat_fetch_replslot(NameData slotname)
29382954
staticvoid
29392955
pgstat_shutdown_hook(intcode,Datumarg)
29402956
{
2957+
Assert(!pgstat_is_shutdown);
2958+
29412959
/*
29422960
* If we got as far as discovering our own database ID, we can report what
29432961
* we did to the collector. Otherwise, we'd be sending an invalid
@@ -2946,20 +2964,26 @@ pgstat_shutdown_hook(int code, Datum arg)
29462964
*/
29472965
if (OidIsValid(MyDatabaseId))
29482966
pgstat_report_stat(true);
2967+
2968+
#ifdefUSE_ASSERT_CHECKING
2969+
pgstat_is_shutdown= true;
2970+
#endif
29492971
}
29502972

29512973
/* ----------
29522974
* pgstat_initialize() -
29532975
*
2954-
*Initialize pgstats state, and set up our on-proc-exit hook.
2955-
*Called from InitPostgres and AuxiliaryProcessMain.
2976+
*Initialize pgstats state, and set up our on-proc-exit hook. Called from
2977+
*BaseInit().
29562978
*
29572979
*NOTE: MyDatabaseId isn't set yet; so the shutdown hook has to be careful.
29582980
* ----------
29592981
*/
29602982
void
29612983
pgstat_initialize(void)
29622984
{
2985+
Assert(!pgstat_is_initialized);
2986+
29632987
/*
29642988
* Initialize prevWalUsage with pgWalUsage so that pgstat_send_wal() can
29652989
* calculate how much pgWalUsage counters are increased by subtracting
@@ -2969,6 +2993,10 @@ pgstat_initialize(void)
29692993

29702994
/* Set up a process-exit hook to clean up */
29712995
on_shmem_exit(pgstat_shutdown_hook,0);
2996+
2997+
#ifdefUSE_ASSERT_CHECKING
2998+
pgstat_is_initialized= true;
2999+
#endif
29723000
}
29733001

29743002
/* ------------------------------------------------------------
@@ -3001,6 +3029,8 @@ pgstat_send(void *msg, int len)
30013029
{
30023030
intrc;
30033031

3032+
pgstat_assert_is_up();
3033+
30043034
if (pgStatSock==PGINVALID_SOCKET)
30053035
return;
30063036

@@ -3053,6 +3083,8 @@ pgstat_send_bgwriter(void)
30533083
/* We assume this initializes to zeroes */
30543084
staticconstPgStat_MsgBgWriterall_zeroes;
30553085

3086+
pgstat_assert_is_up();
3087+
30563088
/*
30573089
* This function can be called even if nothing at all has happened. In
30583090
* this case, avoid sending a completely empty message to the stats
@@ -4629,6 +4661,8 @@ backend_read_statsfile(void)
46294661
Oidinquiry_db;
46304662
intcount;
46314663

4664+
pgstat_assert_is_up();
4665+
46324666
/* already read it? */
46334667
if (pgStatDBHash)
46344668
return;
@@ -4765,6 +4799,17 @@ pgstat_setup_memcxt(void)
47654799
ALLOCSET_SMALL_SIZES);
47664800
}
47674801

4802+
/*
4803+
* Stats should only be reported after pgstat_initialize() and before
4804+
* pgstat_shutdown(). This check is put in a few central places to catch
4805+
* violations of this rule more easily.
4806+
*/
4807+
staticvoid
4808+
pgstat_assert_is_up(void)
4809+
{
4810+
Assert(pgstat_is_initialized&& !pgstat_is_shutdown);
4811+
}
4812+
47684813

47694814
/* ----------
47704815
* pgstat_clear_snapshot() -
@@ -4779,6 +4824,8 @@ pgstat_setup_memcxt(void)
47794824
void
47804825
pgstat_clear_snapshot(void)
47814826
{
4827+
pgstat_assert_is_up();
4828+
47824829
/* Release memory, if any was allocated */
47834830
if (pgStatLocalContext)
47844831
MemoryContextDelete(pgStatLocalContext);
@@ -5897,6 +5944,8 @@ pgstat_slru_name(int slru_idx)
58975944
staticinlinePgStat_MsgSLRU*
58985945
slru_entry(intslru_idx)
58995946
{
5947+
pgstat_assert_is_up();
5948+
59005949
/*
59015950
* The postmaster should never register any SLRU statistics counts; if it
59025951
* did, the counts would be duplicated into child processes via fork().

‎src/backend/utils/init/postinit.c‎

Lines changed: 14 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -517,6 +517,14 @@ BaseInit(void)
517517
*/
518518
DebugFileOpen();
519519

520+
/*
521+
* Initialize statistics reporting. This needs to happen early to ensure
522+
* that pgstat's shutdown callback runs after the shutdown callbacks of
523+
* all subsystems that can produce stats (like e.g. transaction commits
524+
* can).
525+
*/
526+
pgstat_initialize();
527+
520528
/* Do local initialization of file, storage and buffer managers */
521529
InitFileAccess();
522530
InitSync();
@@ -646,10 +654,6 @@ InitPostgres(const char *in_dbname, Oid dboid, const char *username,
646654
/* Initialize portal manager */
647655
EnablePortalManager();
648656

649-
/* Initialize stats collection --- must happen before first xact */
650-
if (!bootstrap)
651-
pgstat_initialize();
652-
653657
/* Initialize status reporting */
654658
if (!bootstrap)
655659
pgstat_beinit();
@@ -662,11 +666,12 @@ InitPostgres(const char *in_dbname, Oid dboid, const char *username,
662666

663667
/*
664668
* Set up process-exit callback to do pre-shutdown cleanup. This is the
665-
* first before_shmem_exit callback we register; thus, this will be the
666-
* last thing we do before low-level modules like the buffer manager begin
667-
* to close down. We need to have this in place before we begin our first
668-
* transaction --- if we fail during the initialization transaction, as is
669-
* entirely possible, we need the AbortTransaction call to clean up.
669+
* one of the first before_shmem_exit callbacks we register; thus, this
670+
* will be one the last things we do before low-level modules like the
671+
* buffer manager begin to close down. We need to have this in place
672+
* before we begin our first transaction --- if we fail during the
673+
* initialization transaction, as is entirely possible, we need the
674+
* AbortTransaction call to clean up.
670675
*/
671676
before_shmem_exit(ShutdownPostgres,0);
672677

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