Hi,
There are instances where pgstat_setup_memcxt() and
pgstat_prep_pending_entry() are invoked before the CacheMemoryContext
has been created. This results in PgStat* contexts being created
without a parent context. Most easily reproduced/seen in autovacuum
worker via pgstat_setup_memcxt().
Attached is a patch to address this.
To see the issue one can add a line similar to this to the top of
MemoryContextCreate() in mcxt.c
fprintf(stderr, "pid: %d ctxname: %s parent is %s CacheMemoryContext is %s\n",
MyProcPid, name, parent == NULL ? "NULL" : "not NULL", CacheMemoryContext ==
NULL ? "NULL" : "Not NULL")
and startup postgres and grep for the above after autovacuum workers
have been invoked
...snip...
pid: 1427756 ctxname: PgStat Pending parent is NULL CacheMemoryContext is NULL
pid: 1427756 ctxname: PgStat Shared Ref parent is NULL CacheMemoryContext is
NULL
...snip...
or
startup postgres, attach gdb to postgres following child, break at
pgstat_setup_memcxt and wait for autovacuum worker to start...
...snip...
─── Source
─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
384 AllocSetContextCreateInternal(MemoryContext parent,
385 const char *name,
386 Size minContextSize,
387 Size initBlockSize,
388 Size maxBlockSize)
389 {
390 int freeListIndex;
391 Size firstBlockSize;
392 AllocSet set;
393 AllocBlock block;
─── Stack
──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
[0] from 0x000055b7e4088b40 in AllocSetContextCreateInternal+0 at
/home/rthompso/src/git/postgres/src/backend/utils/mmgr/aset.c:389
[1] from 0x000055b7e3f41c88 in pgstat_setup_memcxt+2544 at
/home/rthompso/src/git/postgres/src/backend/utils/activity/pgstat_shmem.c:979
[2] from 0x000055b7e3f41c88 in pgstat_get_entry_ref+2648 at
/home/rthompso/src/git/postgres/src/backend/utils/activity/pgstat_shmem.c:410
[3] from 0x000055b7e3f420ea in pgstat_get_entry_ref_locked+26 at
/home/rthompso/src/git/postgres/src/backend/utils/activity/pgstat_shmem.c:598
[4] from 0x000055b7e3f3e2c4 in pgstat_report_autovac+36 at
/home/rthompso/src/git/postgres/src/backend/utils/activity/pgstat_database.c:68
[5] from 0x000055b7e3e7f267 in AutoVacWorkerMain+807 at
/home/rthompso/src/git/postgres/src/backend/postmaster/autovacuum.c:1694
[6] from 0x000055b7e3e7f435 in StartAutoVacWorker+133 at
/home/rthompso/src/git/postgres/src/backend/postmaster/autovacuum.c:1493
[7] from 0x000055b7e3e87367 in StartAutovacuumWorker+557 at
/home/rthompso/src/git/postgres/src/backend/postmaster/postmaster.c:5539
[8] from 0x000055b7e3e87367 in sigusr1_handler+935 at
/home/rthompso/src/git/postgres/src/backend/postmaster/postmaster.c:5244
[9] from 0x00007fb02bca7420 in __restore_rt
[+]
─── Threads
────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
[1] id 1174088 name postgres from 0x000055b7e4088b40 in
AllocSetContextCreateInternal+0 at
/home/rthompso/src/git/postgres/src/backend/utils/mmgr/aset.c:389
─── Variables
──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
arg parent = 0x0, name = 0x55b7e416f179 "PgStat Shared Ref": 80 'P',
minContextSize = 0, initBlockSize = 1024, maxBlockSize = 8192
loc firstBlockSize = <optimized out>, set = <optimized out>, block = <optimized
out>, __FUNCTION__ = "AllocSetContextCreateInternal", __func__ =
"AllocSetContextCreateInternal"
────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
> > > print CacheMemoryContext == NULL
$4 = 1
> > > print parent
$5 = (MemoryContext) 0x0
Thanks,
Reid
diff --git a/src/backend/utils/activity/pgstat.c b/src/backend/utils/activity/pgstat.c
index 0d9d09c492..bf53eba660 100644
--- a/src/backend/utils/activity/pgstat.c
+++ b/src/backend/utils/activity/pgstat.c
@@ -102,6 +102,7 @@
#include "storage/lwlock.h"
#include "storage/pg_shmem.h"
#include "storage/shmem.h"
+#include "utils/catcache.h"
#include "utils/guc.h"
#include "utils/memutils.h"
#include "utils/pgstat_internal.h"
@@ -1059,6 +1060,9 @@ pgstat_prep_pending_entry(PgStat_Kind kind, Oid dboid, Oid objoid, bool *created
if (unlikely(!pgStatPendingContext))
{
+ if (unlikely(!CacheMemoryContext))
+ CreateCacheMemoryContext();
+
pgStatPendingContext =
AllocSetContextCreate(CacheMemoryContext,
"PgStat Pending",
diff --git a/src/backend/utils/activity/pgstat_shmem.c b/src/backend/utils/activity/pgstat_shmem.c
index 89060ef29a..6462510f11 100644
--- a/src/backend/utils/activity/pgstat_shmem.c
+++ b/src/backend/utils/activity/pgstat_shmem.c
@@ -14,6 +14,7 @@
#include "pgstat.h"
#include "storage/shmem.h"
+#include "utils/catcache.h"
#include "utils/memutils.h"
#include "utils/pgstat_internal.h"
@@ -974,6 +975,9 @@ pgstat_reset_entries_of_kind(PgStat_Kind kind, TimestampTz ts)
static void
pgstat_setup_memcxt(void)
{
+ if (unlikely(!CacheMemoryContext))
+ CreateCacheMemoryContext();
+
if (unlikely(!pgStatSharedRefContext))
pgStatSharedRefContext =
AllocSetContextCreate(CacheMemoryContext,
