Thread

Concurrency Issue with pg_ctl causing processes to hang in PostgreSQL 15.12

Srirama Kucherlapati <sriram.rk@in.ibm.com> — 2025-09-02T07:26:32Z

Hi all,
We are encountering a concurrency issue with pg_ctl in PostgreSQL 15.12, two separate processes  are invoking pg_ctl simultaneously on different databases directories:
-   One process is attempting to stop a database.
-   Another process is concurrently executing pg_ctl status to check the PG server state.


Below are the running pg_ctl processes. Here to mention both the DB directories are entirely different.

    pgadmin 25559346 26870100  0  Aug 28   - 0:00 -ksh -c pg_ctl status -D /pgmount/PG/DB/
    pgadmin 25690410 27591028  0  Aug 28   - 0:00 -ksh -c pg_ctl stop -D /pgmount/MS/DB/



This concurrent usage results in both processes hanging indefinitely.
Below are the stacks of both the processes

    # dbx -a 25559346
    Waiting to attach to process 25559346 ...
    Successfully attached to ksh.
    warning: Directory containing ksh could not be determined.
    Apply ‘use’ command to initialize source path.Type ‘help’ for help.
    reading symbolic information ...warning: no source compiled with -gstopped in pause at 0xd01b7104
    0xd01b7104 (pause+0x204) 80410014      lwz  r2,0x14(r1)

    (dbx) t
    pause() at 0xd01b7104
    IPRA.(??, ??, ??, ??, ??) at 0x100387f4
    sh_exec(??, ??, ??) at 0x1003a120
    IPRA.(??) at 0x10009328
    IPRA.(??) at 0x1000a98c
    copyto(??, ??, ??) at 0x1000af0c
    mac_expand(??) at 0x1000b960
    mac_trim(??, ??) at 0x1000b5dc
    env_setlist(??, ??) at 0x10022034
    IPRA.(??, ??, ??, ??, ??) at 0x10038c90
    sh_exec(??, ??, ??) at 0x1003a120
    IPRA.() at 0x10001b48
    main(??, ??) at 0x10000e3c


    # dbx -a 25690410
    Waiting to attach to process 25690410 ...
    Successfully attached to ksh.
    warning: Directory containing ksh could not be determined.
    Apply ‘use’ command to initialize source path.Type ‘help’ for help.
    reading symbolic information ...warning: no source compiled with -gstopped in pause at 0xd01b7104
    0xd01b7104 (pause+0x204) 80410014      lwz  r2,0x14(r1)
    (dbx) th
    (dbx) t
    pause() at 0xd01b7104
    IPRA.(??, ??, ??, ??, ??) at 0x100387f4
    sh_exec(??, ??, ??) at 0x1003a120
    IPRA.(??) at 0x10009328
    IPRA.(??) at 0x1000a98c
    copyto(??, ??, ??) at 0x1000af0c
    mac_expand(??) at 0x1000b960
    mac_trim(??, ??) at 0x1000b5dc
    env_setlist(??, ??) at 0x10022034
    IPRA.(??, ??, ??, ??, ??) at 0x10038c90
    sh_exec(??, ??, ??) at 0x1003a120
    IPRA.() at 0x10001b48
    main(??, ??) at 0x10000e3c


Is this a known issue in PostgreSQL 15.12?
Are there recommended workarounds or configuration changes to avoid this behaviour?
Is there any way for pg_ctl to internally lock, to prevent such hangs?
Do we need to serialize pg_ctl stop and status, even if we are running different database?



Warm regards,
Sriram.