BUG #18992: Autovacuum triggering assert - LWLockAnyHeldByMe

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.

-
robins
https://robins.in