On Mon, Apr 06, 2026 at 11:36:21AM +0900, Michael Paquier wrote:
> On Mon, Apr 06, 2026 at 09:55:14AM +0900, Michael Paquier wrote:
>> Right, down to v18 where this has been introduced.  That's my bug, so
>> I'd be OK to take care of it myself, if you are OK with that of
>> course.
> 
> Note: something is wrong with -m32, for both patches.  Digging into
> that..

And I have been puzzled for a few minutes here, trying to figure out
if this was something in v18 or something with the new shmem routines.
It is nothing of the kind: test_custom_stats has been underestimating
its shared_size, using PgStat_StatCustomFixedEntry instead of
PgStatShared_CustomFixedEntry.  Interesting copy-pasto, HEAD-only,
second bug.

The attached is working correctly.  The v18 flavor is slightly
simpler.
--
Michael
From 943746c5b430b485e15c44a0b7bf099454cee7dd Mon Sep 17 00:00:00 2001
From: Michael Paquier <[email protected]>
Date: Mon, 6 Apr 2026 09:47:02 +0900
Subject: [PATCH v3] Use the allocated space properly for custom stats kind

---
 src/backend/utils/activity/pgstat_shmem.c                  | 7 ++++---
 .../modules/test_custom_stats/test_custom_fixed_stats.c    | 2 +-
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/utils/activity/pgstat_shmem.c 
b/src/backend/utils/activity/pgstat_shmem.c
index 955faf5ebc7d..b8f354c818a0 100644
--- a/src/backend/utils/activity/pgstat_shmem.c
+++ b/src/backend/utils/activity/pgstat_shmem.c
@@ -150,8 +150,7 @@ StatsShmemSize(void)
                        continue;
 
                Assert(kind_info->shared_size != 0);
-
-               sz += MAXALIGN(kind_info->shared_size);
+               sz = add_size(sz, MAXALIGN(kind_info->shared_size));
        }
 
        return sz;
@@ -189,6 +188,7 @@ StatsShmemInit(void *arg)
         * efficiency win.
         */
        ctl->raw_dsa_area = p;
+       p += pgstat_dsa_init_size();
        dsa = dsa_create_in_place(ctl->raw_dsa_area,
                                                          
pgstat_dsa_init_size(),
                                                          
LWTRANCHE_PGSTATS_DSA, NULL);
@@ -242,7 +242,8 @@ StatsShmemInit(void *arg)
                                int                     idx = kind - 
PGSTAT_KIND_CUSTOM_MIN;
 
                                Assert(kind_info->shared_size != 0);
-                               ctl->custom_data[idx] = 
ShmemAlloc(kind_info->shared_size);
+                               ctl->custom_data[idx] = p;
+                               p += MAXALIGN(kind_info->shared_size);
                                ptr = ctl->custom_data[idx];
                        }
 
diff --git a/src/test/modules/test_custom_stats/test_custom_fixed_stats.c 
b/src/test/modules/test_custom_stats/test_custom_fixed_stats.c
index f9e7c7172802..a066ce117a6d 100644
--- a/src/test/modules/test_custom_stats/test_custom_fixed_stats.c
+++ b/src/test/modules/test_custom_stats/test_custom_fixed_stats.c
@@ -50,7 +50,7 @@ static const PgStat_KindInfo custom_stats = {
        .fixed_amount = true,           /* exactly one entry */
        .write_to_file = true,          /* persist to stats file */
 
-       .shared_size = sizeof(PgStat_StatCustomFixedEntry),
+       .shared_size = sizeof(PgStatShared_CustomFixedEntry),
        .shared_data_off = offsetof(PgStatShared_CustomFixedEntry, stats),
        .shared_data_len = sizeof(((PgStatShared_CustomFixedEntry *) 0)->stats),
 
-- 
2.53.0

From f6787781026c7dcf6c9a38b0e7f8c8427a7b2da6 Mon Sep 17 00:00:00 2001
From: Michael Paquier <[email protected]>
Date: Mon, 6 Apr 2026 09:47:02 +0900
Subject: [PATCH v3] Use the allocated space properly for custom stats kind

---
 src/backend/utils/activity/pgstat_shmem.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/backend/utils/activity/pgstat_shmem.c 
b/src/backend/utils/activity/pgstat_shmem.c
index 08ec264baa3a..2b7f783ef7c4 100644
--- a/src/backend/utils/activity/pgstat_shmem.c
+++ b/src/backend/utils/activity/pgstat_shmem.c
@@ -142,8 +142,7 @@ StatsShmemSize(void)
                        continue;
 
                Assert(kind_info->shared_size != 0);
-
-               sz += MAXALIGN(kind_info->shared_size);
+               sz = add_size(sz, MAXALIGN(kind_info->shared_size));
        }
 
        return sz;
@@ -227,7 +226,8 @@ StatsShmemInit(void)
                                int                     idx = kind - 
PGSTAT_KIND_CUSTOM_MIN;
 
                                Assert(kind_info->shared_size != 0);
-                               ctl->custom_data[idx] = 
ShmemAlloc(kind_info->shared_size);
+                               ctl->custom_data[idx] = p;
+                               p += MAXALIGN(kind_info->shared_size);
                                ptr = ctl->custom_data[idx];
                        }
 
-- 
2.53.0

Attachment: signature.asc
Description: PGP signature

Reply via email to