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In-Reply-To: <7de8e39c-d1c4-4783-91b9-129d90e91411@iki.fi>
From: Zsolt Parragi <zsolt.parragi@percona.com>
Date: Fri, 13 Mar 2026 23:02:05 +0000
Message-ID: 
 <CAN4CZFP5yPRyQtqZHSPB_Qb9i3VcKk1RYLjJb3HAP693CNxVbA@mail.gmail.com>
Subject: Re: Better shared data structure management and resizable shared data
 structures
To: Heikki Linnakangas <hlinnaka@iki.fi>
Cc: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>,
 Andres Freund <andres@anarazel.de>,
	pgsql-hackers <pgsql-hackers@postgresql.org>, chaturvedipalak1911@gmail.com
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 <https://www.postgresql.org/message-id/CAN4CZFP5yPRyQtqZHSPB_Qb9i3VcKk1RYLjJb3HAP693CNxVbA%40mail.gmail.com>
Precedence: bulk

Hello

 dsm_shmem_init(void)
 {
  size_t size = dsm_estimate_size();
- bool found;

  if (size == 0)
  return;

Isn't there an assignment missing from this function now? Size is
calculated but never used. With the current code if
min_dynamic_shared_memory > 0 the server can crash.

+static ShmemHashDesc WaitEventCustomHashByNameDesc =
+{
+ .name = "WaitEventCustom hash by name",
+ .ptr = &WaitEventCustomHashByName,
+
+ .init_size = WAIT_EVENT_CUSTOM_HASH_INIT_SIZE,
+ .max_size = WAIT_EVENT_CUSTOM_HASH_MAX_SIZE,
+ /* key is a NULL-terminated string */
+ .hash_info.keysize = sizeof(char[NAMEDATALEN]),
+ .hash_info.entrysize = sizeof(WaitEventCustomEntryByName),
+ .hash_flags = HASH_ELEM | HASH_BLOBS,
+};

This was HASH_STRINGS originally, and it is used with plain const
char* parameters. Shouldn't it use HASH_SRINGS as before?

  size = add_size(size, ShmemRegisteredSize());

  size = add_size(size, dsm_estimate_size());
- size = add_size(size, DSMRegistryShmemSize());
+
+ size = add_size(size, ShmemRegisteredSize());

ShmemRegisteredSize is now called twice.

+    /* Initialize the lock */
+    tranche_id = LWLockNewTrancheId("my tranche name");
+    LWLockInitialize(&amp;MyShmem->lock);

Second parameter is missing for LWLockInitialize