Hi Tomas Vondra,
> What extensions are you using? Especially extensions third-party > extensions? We are working on our own columnar extension and have modified the PostgreSQL source code to enable pg stats for foreign tables and to support autoanalyze and autovacuum on foreign tables. >From PostgreSQL 15 onward, statistics were moved to shared memory. We started >observing this issue in production after upgrading from PostgreSQL 14 to >PostgreSQL 17.2 / 17.7. Could this dsa issue be related to pg stats? > The second trace > unfortunately does not show what happened to PID 2037344 before it > crashes, which would be very interesting to know. Was it an OOM too? The process with PID 2037344 did not terminate due to an OOM intead ended with segfalut. Regards Reshmithaa B From: Tomas Vondra < mailto:[email protected] > To: "Reshmithaa"< mailto:[email protected] >, "pgsql-hackers"< mailto:[email protected] > Date: Mon, 16 Feb 2026 03:34:53 +0530 Subject: Re: Crash related to Shared Memory Hi, On 2/15/26 09:53, Reshmithaa wrote: > Hi, > > We have developed a PostgreSQL extension and are currently encountering > intermittent crashes related to shared memory on PostgreSQL 17.7. The > issue does not occur everytime, and we have not been able to reliably > reproduce it in our local environment. We have attached the relevant pg > logs and backtraces below for reference. > > We also noticed a recent commit addressing a DSM-related issue: > > https://git.postgresql.org/gitweb/? > p=postgresql.git;a=commitdiff;h=1d0fc2499 < https://git.postgresql.org/ > gitweb/?p=postgresql.git;a=commitdiff;h=1d0fc2499> > > Could you please confirm whether this change can resolve the type of > crash we are encountering? > Maybe, but it's hard to say based on the logs you provided. In the commit message you linked, Robert speculated this should not be happening in core Postgres, but that maybe extensions could trip over this. What extensions are you using? Especially extensions third-party extensions? It's interesting both traces end with a segfault, but in both cases there are "strange" errors immediately before that. In particular the first trace shows [568804]:ERROR: 53200: out of memory [568804]:DETAIL: Failed while allocating entry 2/17266/55068384. [568804]:LOCATION: pgstat_get_entry_ref, pgstat_shmem.c:510 [568804]:STATEMENT: ANALYZE tab2_temp For the process that then crashes with a segfault. The second trace unfortunately does not show what happened to PID 2037344 before it crashes, which would be very interesting to know. Was it an OOM too? But there are a couple other suspicious errors from other PIDs, like [2136038]:ERROR: XX000: dsa_area could not attach to a segment that has been freed [2136038]:LOCATION: get_segment_by_index, dsa.c:1781 I don't think this should be happening in core code, at least I don't recall seeing anything like that recently. I wonder if the cleanup after OOM could lead to the crash because the error cleanup destroys the short-lived context, in a way Robert did not envision in the commit message. But I haven't tried and it's just a speculation. FWIW even if the commit (and upgrading to 17.8) fixes the crash, I don't think that'll fix the other errors shown in the traces. You should probably look into that. regards -- Tomas Vondra
