Re: BUG #18992: Autovacuum triggering assert - LWLockAnyHeldByMe

On Sun, Jul 20, 2025 at 9:35 PM PG Bug reporting form
<noreply(at)postgresql(dot)org> wrote:
>
> The following bug has been logged on the website:
>
> Bug reference: 18992
> Logged by: Robins Tharakan
> Email address: tharakan(at)gmail(dot)com
> PostgreSQL version: 18beta2
> Operating system: Ubuntu
> Description:
>
> I couldn't repro the assert at will, but the test setup crashed
> thrice since yesterday and thus this report. Although this was
> on a recent version (1e9b5140c44), the test itself is running after
> a few weeks, so the issue may not be recent.
>
>
> Error Log
> =========
> TRAP: failed
> Assert("!LWLockAnyHeldByMe(&(hash_table)->control->partitions[0].lock,
> DSHASH_NUM_PARTITIONS, sizeof(dshash_partition))"), File: "dshash.c", Line:
> 400, PID: 147794
> postgres: 1e9b5140c44(at)sqith: autovacuum worker
> (ExceptionalCondition+0xbb)[0x5a609cb46036]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker
> (dshash_find+0xab)[0x5a609c6a81f2]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker
> (pgstat_drop_entry+0xc2)[0x5a609c968cb7]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker (+0x73c443)[0x5a609c95c443]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker
> (shmem_exit+0xa6)[0x5a609c8ef83e]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker (+0x6cf6e2)[0x5a609c8ef6e2]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker
> (proc_exit+0x74)[0x5a609c8ef626]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker
> (AutoVacWorkerMain+0x19c)[0x5a609c8231ad]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker
> (postmaster_child_launch+0x174)[0x5a609c82ad34]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker (+0x612191)[0x5a609c832191]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker (+0x612328)[0x5a609c832328]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker (+0x611dd5)[0x5a609c831dd5]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker (+0x60ec84)[0x5a609c82ec84]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker
> (PostmasterMain+0x1546)[0x5a609c82e5e4]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker (main+0x38c)[0x5a609c6ca6f3]
> /lib/x86_64-linux-gnu/libc.so.6(+0x2a1ca)[0x7f726022a1ca]
> /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0x8b)[0x7f726022a28b]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker (_start+0x25)[0x5a609c307fb5]
>
>
> TRAP: failed
> Assert("!LWLockAnyHeldByMe(&(hash_table)->control->partitions[0].lock,
> DSHASH_NUM_PARTITIONS, sizeof(dshash_partition))"), File: "dshash.c", Line:
> 400, PID: 147794
> postgres: 1e9b5140c44(at)sqith: autovacuum worker
> (ExceptionalCondition+0xbb)[0x5a609cb46036]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker
> (dshash_find+0xab)[0x5a609c6a81f2]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker
> (pgstat_drop_entry+0xc2)[0x5a609c968cb7]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker (+0x73c443)[0x5a609c95c443]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker
> (shmem_exit+0xa6)[0x5a609c8ef83e]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker (+0x6cf6e2)[0x5a609c8ef6e2]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker
> (proc_exit+0x74)[0x5a609c8ef626]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker
> (AutoVacWorkerMain+0x19c)[0x5a609c8231ad]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker
> (postmaster_child_launch+0x174)[0x5a609c82ad34]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker (+0x612191)[0x5a609c832191]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker (+0x612328)[0x5a609c832328]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker (+0x611dd5)[0x5a609c831dd5]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker (+0x60ec84)[0x5a609c82ec84]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker
> (PostmasterMain+0x1546)[0x5a609c82e5e4]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker (main+0x38c)[0x5a609c6ca6f3]
> /lib/x86_64-linux-gnu/libc.so.6(+0x2a1ca)[0x7f726022a1ca]
> /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0x8b)[0x7f726022a28b]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker (_start+0x25)[0x5a609c307fb5]
> 2025-07-19 20:07:07.398 ACST [55365] LOG: autovacuum worker (PID 147794)
> was terminated by signal 6: Aborted
>
>
>
> 2025-07-20 06:17:50.376 ACST [1190828] FATAL: can't attach the same segment
> more than once
> TRAP: failed
> Assert("!LWLockAnyHeldByMe(&(hash_table)->control->partitions[0].lock,
> DSHASH_NUM_PARTITIONS, sizeof(dshash_partition))"), File: "dshash.c", Line:
> 400, PID: 1190928
> postgres: 1e9b5140c44(at)sqith: autovacuum worker
> (ExceptionalCondition+0xbb)[0x56d3cc97c036]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker
> (dshash_find+0xab)[0x56d3cc4de1f2]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker
> (pgstat_drop_entry+0xc2)[0x56d3cc79ecb7]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker (+0x73c443)[0x56d3cc792443]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker
> (shmem_exit+0xa6)[0x56d3cc72583e]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker (+0x6cf6e2)[0x56d3cc7256e2]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker
> (proc_exit+0x74)[0x56d3cc725626]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker
> (AutoVacWorkerMain+0x19c)[0x56d3cc6591ad]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker
> (postmaster_child_launch+0x174)[0x56d3cc660d34]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker (+0x612191)[0x56d3cc668191]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker (+0x612328)[0x56d3cc668328]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker (+0x611dd5)[0x56d3cc667dd5]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker (+0x60ec84)[0x56d3cc664c84]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker
> (PostmasterMain+0x1546)[0x56d3cc6645e4]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker (main+0x38c)[0x56d3cc5006f3]
> /lib/x86_64-linux-gnu/libc.so.6(+0x2a1ca)[0x758b0e42a1ca]
> /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0x8b)[0x758b0e42a28b]
> postgres: 1e9b5140c44(at)sqith: autovacuum worker (_start+0x25)[0x56d3cc13dfb5]
> 2025-07-20 06:18:22.919 ACST [169020] LOG: autovacuum worker (PID 1190928)
> was terminated by signal 6: Aborted
>
>
>
> Backtrace
> =========
> (gdb) bt
> #0 __pthread_kill_implementation (no_tid=0, signo=6, threadid=<optimised
> out>) at ./nptl/pthread_kill.c:44
> #1 __pthread_kill_internal (signo=6, threadid=<optimised out>) at
> ./nptl/pthread_kill.c:78
> #2 __GI___pthread_kill (threadid=<optimised out>, signo=signo(at)entry=6) at
> ./nptl/pthread_kill.c:89
> #3 0x00007f726024527e in __GI_raise (sig=sig(at)entry=6) at
> ../sysdeps/posix/raise.c:26
> #4 0x00007f72602288ff in __GI_abort () at ./stdlib/abort.c:79
> #5 0x00005a609cb46069 in ExceptionalCondition (conditionName=0x5a609cd3af40
> "!LWLockAnyHeldByMe(&(hash_table)->control->partitions[0].lock,
> DSHASH_NUM_PARTITIONS, sizeof(dshash_partition))", fileName=0x5a609cd3af03
> "dshash.c", lineNumber=400) at assert.c:66
> #6 0x00005a609c6a81f2 in dshash_find (hash_table=0x5a60ab734b10,
> key=0x7ffe06d72500, exclusive=true) at dshash.c:400
> #7 0x00005a609c968cb7 in pgstat_drop_entry (kind=6, dboid=0, objid=5015) at
> pgstat_shmem.c:988
> #8 0x00005a609c95c443 in pgstat_shutdown_hook (code=0, arg=0) at
> pgstat.c:622
> #9 0x00005a609c8ef83e in shmem_exit (code=0) at ipc.c:243
> #10 0x00005a609c8ef6e2 in proc_exit_prepare (code=0) at ipc.c:198
> #11 0x00005a609c8ef626 in proc_exit (code=0) at ipc.c:111
> #12 0x00005a609c8231ad in AutoVacWorkerMain (startup_data=0x0,
> startup_data_len=0) at autovacuum.c:1456
> #13 0x00005a609c82ad34 in postmaster_child_launch
> (child_type=B_AUTOVAC_WORKER, child_slot=10002, startup_data=0x0,
> startup_data_len=0, client_sock=0x0) at launch_backend.c:290
> #14 0x00005a609c832191 in StartChildProcess (type=B_AUTOVAC_WORKER) at
> postmaster.c:3973
> #15 0x00005a609c832328 in StartAutovacuumWorker () at postmaster.c:4037
> #16 0x00005a609c831dd5 in process_pm_pmsignal () at postmaster.c:3794
> #17 0x00005a609c82ec84 in ServerLoop () at postmaster.c:1695
> #18 0x00005a609c82e5e4 in PostmasterMain (argc=3, argv=0x5a60ab733940) at
> postmaster.c:1400
> #19 0x00005a609c6ca6f3 in main (argc=3, argv=0x5a60ab733940) at main.c:231
>
>
> Backtrace Full
> ==============
> #0 __pthread_kill_implementation (no_tid=0, signo=6, threadid=<optimised
> out>) at ./nptl/pthread_kill.c:44
> tid = <optimised out>
> ret = 0
> pd = <optimised out>
> old_mask = {__val = {18446744073709551568}}
> ret = <optimised out>
> pd = <optimised out>
> old_mask = <optimised out>
> ret = <optimised out>
> tid = <optimised out>
> ret = <optimised out>
> resultvar = <optimised out>
> resultvar = <optimised out>
> __arg3 = <optimised out>
> __arg2 = <optimised out>
> __arg1 = <optimised out>
> _a3 = <optimised out>
> _a2 = <optimised out>
> _a1 = <optimised out>
> __futex = <optimised out>
> resultvar = <optimised out>
> __arg3 = <optimised out>
> __arg2 = <optimised out>
> __arg1 = <optimised out>
> _a3 = <optimised out>
> _a2 = <optimised out>
> _a1 = <optimised out>
> __futex = <optimised out>
> __private = <optimised out>
> __oldval = <optimised out>
> #1 __pthread_kill_internal (signo=6, threadid=<optimised out>) at
> ./nptl/pthread_kill.c:78
> No locals.
> #2 __GI___pthread_kill (threadid=<optimised out>, signo=signo(at)entry=6) at
> ./nptl/pthread_kill.c:89
> No locals.
> #3 0x00007f726024527e in __GI_raise (sig=sig(at)entry=6) at
> ../sysdeps/posix/raise.c:26
> ret = <optimised out>
> #4 0x00007f72602288ff in __GI_abort () at ./stdlib/abort.c:79
> save_stage = 1
> act = {__sigaction_handler = {sa_handler = 0x20, sa_sigaction =
> 0x20}, sa_mask = {__val = {2, 140129217590784, 1, 140129217603397, 3,
> 140729013182628, 12, 140129217603401, 2, 3474071045457511480,
> 3846749418945733433, 140729013182720, 3833180526369726083, 140729013182784,
> 16669054559647844352, 140729013186696}}, sa_flags = 114765976, sa_restorer =
> 0x3}
> #5 0x00005a609cb46069 in ExceptionalCondition (conditionName=0x5a609cd3af40
> "!LWLockAnyHeldByMe(&(hash_table)->control->partitions[0].lock,
> DSHASH_NUM_PARTITIONS, sizeof(dshash_partition))", fileName=0x5a609cd3af03
> "dshash.c", lineNumber=400) at assert.c:66
> No locals.
> #6 0x00005a609c6a81f2 in dshash_find (hash_table=0x5a60ab734b10,
> key=0x7ffe06d72500, exclusive=true) at dshash.c:400
> hash = 147533127
> partition = 4
> item = 0x8cb2d4700000001
> #7 0x00005a609c968cb7 in pgstat_drop_entry (kind=6, dboid=0, objid=5015) at
> pgstat_shmem.c:988
> key = {kind = 6, dboid = 0, objid = 5015}
> shent = 0x5a609c8c83ec <pgaio_shutdown+406>
> freed = true
> #8 0x00005a609c95c443 in pgstat_shutdown_hook (code=0, arg=0) at
> pgstat.c:622
> No locals.
> #9 0x00005a609c8ef83e in shmem_exit (code=0) at ipc.c:243
> __func__ = "shmem_exit"
> #10 0x00005a609c8ef6e2 in proc_exit_prepare (code=0) at ipc.c:198
> __func__ = "proc_exit_prepare"
> #11 0x00005a609c8ef626 in proc_exit (code=0) at ipc.c:111
> __func__ = "proc_exit"
> #12 0x00005a609c8231ad in AutoVacWorkerMain (startup_data=0x0,
> startup_data_len=0) at autovacuum.c:1456
> local_sigjmp_buf = {{__jmpbuf = {140729013186712,
> -5847007501798591079, 3, 0, 99370996794424, 140129240260608,
> -5847007501689539175, -1880687092341131879}, __mask_was_saved = 1,
> __saved_mask = {__val = {18446744066192964099, 99370993001878, 0,
> 99370993001878, 15511593002, 99370993001878, 0, 99371239819984,
> 99371239819904, 140729013184112, 16669054559647844352,
> 140729013184224, 140129216851989, 140729013184144,
> 16669054559647844352, 16}}}}
> dbid = 4
> __func__ = "AutoVacWorkerMain"
> #13 0x00005a609c82ad34 in postmaster_child_launch
> (child_type=B_AUTOVAC_WORKER, child_slot=10002, startup_data=0x0,
> startup_data_len=0, client_sock=0x0) at launch_backend.c:290
> pid = 0
> #14 0x00005a609c832191 in StartChildProcess (type=B_AUTOVAC_WORKER) at
> postmaster.c:3973
> pmchild = 0x7f7260f16378
> pid = 32766
> __func__ = "StartChildProcess"
>
>
> Found using SQLSmith.

So the call stack shows that it hit the exception while cleaning up
stats during proc_exit, due to an error, I am not sure how easy to
locate this, but this is an error path, so can you help with the error
reported in the log, before hitting the exception?

--
Regards,
Dilip Kumar
Google