Re: margay fails assertion in stats/dsa/dsm code

Hi,

On 2022-07-02 11:10:07 +1200, Thomas Munro wrote:
> 2022-07-01 18:25:25.848 CEST [27738:21] pg_regress/prepared_xacts
> ERROR:  could not open shared memory segment "/PostgreSQL.499018794":
> File exists
> 2022-07-01 18:25:25.848 CEST [27738:22] pg_regress/prepared_xacts
> STATEMENT:  SELECT * FROM pxtest1;
> TRAP: FailedAssertion("!hash_table->find_locked", File: "dshash.c",
> Line: 312, PID: 27784)
> /home/marcel/build-farm-14/buildroot/HEAD/pgsql.build/tmp_install/home/marcel/build-farm-14/buildroot/HEAD/inst/bin/postgres'ExceptionalCondition+0x64
> [0x1008bb8b0]
> /home/marcel/build-farm-14/buildroot/HEAD/pgsql.build/tmp_install/home/marcel/build-farm-14/buildroot/HEAD/inst/bin/postgres'dshash_detach+0x48
> [0x10058674c]
> /home/marcel/build-farm-14/buildroot/HEAD/pgsql.build/tmp_install/home/marcel/build-farm-14/buildroot/HEAD/inst/bin/postgres'pgstat_detach_shmem+0x68
> [0x10075e630]
> /home/marcel/build-farm-14/buildroot/HEAD/pgsql.build/tmp_install/home/marcel/build-farm-14/buildroot/HEAD/inst/bin/postgres'pgstat_shutdown_hook+0x94
> [0x10075989c]
> /home/marcel/build-farm-14/buildroot/HEAD/pgsql.build/tmp_install/home/marcel/build-farm-14/buildroot/HEAD/inst/bin/postgres'shmem_exit+0x84
> [0x100701198]
> /home/marcel/build-farm-14/buildroot/HEAD/pgsql.build/tmp_install/home/marcel/build-farm-14/buildroot/HEAD/inst/bin/postgres'proc_exit_prepare+0x88
> [0x100701394]
> /home/marcel/build-farm-14/buildroot/HEAD/pgsql.build/tmp_install/home/marcel/build-farm-14/buildroot/HEAD/inst/bin/postgres'proc_exit+0x4
> [0x10070148c]
> /home/marcel/build-farm-14/buildroot/HEAD/pgsql.build/tmp_install/home/marcel/build-farm-14/buildroot/HEAD/inst/bin/postgres'StartBackgroundWorker+0x150
> [0x10066957c]
> /home/marcel/build-farm-14/buildroot/HEAD/pgsql.build/tmp_install/home/marcel/build-farm-14/buildroot/HEAD/inst/bin/postgres'maybe_start_bgworkers+0x604
> [0x1006717ec]
> /home/marcel/build-farm-14/buildroot/HEAD/pgsql.build/tmp_install/home/marcel/build-farm-14/buildroot/HEAD/inst/bin/postgres'sigusr1_handler+0x190
> [0x100672510]
> 
> So that's an exception safety problem in dshash or pgstat's new usage
> thereof, which is arguably independent of Solaris and probably
> deserves a new thread.  You don't need Solaris to see it, you can just
> add in some random fault injection.

FWIW potentially relevant thread for that aspect: https://postgr.es/m/20220311012712.botrpsikaufzteyt%40alap3.anarazel.de

What do you think about the proposal at the end of that email?

Greetings,

Andres Freund