Feedback-ID: i0fe9450f:Fastmail
Date: Thu, 6 Jun 2024 13:44:26 +0900
From: Michael Paquier <michael@paquier.xyz>
To: Floris Van Nee <florisvannee@optiver.com>
Cc: Andres Freund <andres@anarazel.de>, Tom Lane <tgl@sss.pgh.pa.us>,
	"pgsql-bugs@lists.postgresql.org" <pgsql-bugs@lists.postgresql.org>,
	Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Subject: Re: error "can only drop stats once" brings down database
Message-ID: <ZmE-qm8d9kfDfnMy@paquier.xyz>
References: <b14ae28029f64757bb64613be2549a74@Optiver.com>
 <215498.1708454947@sss.pgh.pa.us>
 <8e5cb534706a4f43bd74405c8fd91437@Optiver.com>
 <20240505160915.6boysum4f34siqct@awork3.anarazel.de>
 <20240505223546.6yvjzgqifuoiii3e@awork3.anarazel.de>
 <47ca6fcc687e408287871f7eaaaf3c3b@Optiver.com>
 <Zl6gQNSeWoBdijxZ@paquier.xyz>
 <68430b1b76d44558b7b07ae8c69151f6@Optiver.com>
MIME-Version: 1.0
Content-Type: multipart/signed; micalg=pgp-sha512;
	protocol="application/pgp-signature"; boundary="F6EDKW2PmDELAMiU"
Content-Disposition: inline
In-Reply-To: <68430b1b76d44558b7b07ae8c69151f6@Optiver.com>
Archived-At: 
 <https://www.postgresql.org/message-id/ZmE-qm8d9kfDfnMy%40paquier.xyz>
Precedence: bulk


--F6EDKW2PmDELAMiU
Content-Type: multipart/mixed; boundary="YXUgwLXGqI4Bhyfo"
Content-Disposition: inline


--YXUgwLXGqI4Bhyfo
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline

On Wed, Jun 05, 2024 at 10:31:04AM +0000, Floris Van Nee wrote:
> This patch would help in getting more info about this specific issue
> if it reoccurs, but in that case it's only helpful if it's
> backpatched.
> Agree the refcount addition makes sense.

Adding Bertrand in CC as he was similarly playing with this area.

What would both of you think about the attached.  This is a mix of
what's been proposed on the two threads, with the addition of the
refcount.
--
Michael

--YXUgwLXGqI4Bhyfo
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment; filename="pgstat-drop-debug.patch"
Content-Transfer-Encoding: quoted-printable

diff --git a/src/backend/utils/activity/pgstat_shmem.c b/src/backend/utils/=
activity/pgstat_shmem.c
index 4a4b69891d..fb79c5e771 100644
--- a/src/backend/utils/activity/pgstat_shmem.c
+++ b/src/backend/utils/activity/pgstat_shmem.c
@@ -785,7 +785,11 @@ pgstat_drop_entry_internal(PgStatShared_HashEntry *she=
nt,
 	 * backends to release their references.
 	 */
 	if (shent->dropped)
-		elog(ERROR, "can only drop stats once");
+		elog(ERROR,
+			 "trying to drop stats entry already dropped: kind=3D%s dboid=3D%u objo=
id=3D%u refcount=3D%u",
+			 pgstat_get_kind_info(shent->key.kind)->name,
+			 shent->key.dboid, shent->key.objoid,
+			 pg_atomic_read_u32(&shent->refcount));
 	shent->dropped =3D true;
=20
 	/* release refcount marking entry as not dropped */

--YXUgwLXGqI4Bhyfo--

--F6EDKW2PmDELAMiU
Content-Type: application/pgp-signature; name="signature.asc"

-----BEGIN PGP SIGNATURE-----
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=4pfw
-----END PGP SIGNATURE-----

--F6EDKW2PmDELAMiU--