Hello Nathan,
04.09.2025 23:37, Nathan Bossart wrote:
On Thu, Sep 04, 2025 at 12:30:27PM -0500, Sami Imseih wrote:
I liked removing the repalloc calls inside this routine and did not think
it was worth optimizing. I am OK with reverting it back. Although v1
is incorrect since it's still initializing
NamedLWLockTrancheRequestArray to MAX_NAMED_TRANCHES
Committed with that fix.
Furthermore, the
MAX_NAMED_TRANCHES check isn't actually needed because InitializeLWLocks()
will do the same check via its calls to LWLockNewTrancheId() for all the
named tranche requests.
I thought about that one and decided to add the error message there, since
requesting a tranche happens way before LWLockNewTrancheId is called
during CreateLWLocks, so it was more about erroring out slightly earlier.
But it may be ok to also just remove it.
We needed it before because the array could only ever hold
MAX_NAMED_TRANCHES requests.
I've discovered (with SQLsmith) that the new possible error makes
pg_prewarm/autoprewarm fail when the error triggered during it's
initialization and then another instance tries to acquire apw_state->lock.
Please try the following:
psql -c "CREATE EXTENSION test_dsa; CREATE EXTENSION pg_prewarm;"
psql -c "SELECT test_dsa_resowners() FROM generate_series(1, 256)" >/dev/null
psql -c "SELECT pg_sleep(0.5); SELECT autoprewarm_dump_now()" &
psql -c "SELECT pg_sleep(1); SELECT autoprewarm_dump_now()"
with
debug_parallel_query = 'on'
min_dynamic_shared_memory = '1GB'
in postgresql.conf
it causes PANIC for me (on roughly 5 out or 10 runs) as below:
CREATE EXTENSION
CREATE EXTENSION
pg_sleep
----------
(1 row)
ERROR: maximum number of tranches already registered
DETAIL: No more than 256 tranches may be registered.
pg_sleep
----------
(1 row)
server closed the connection unexpectedly
This probably means the server terminated abnormally
before or while processing the request.
PANIC: stuck spinlock detected at LWLockWaitListLock, lwlock.c:882
...
#5 0x000057831e809d1d in errfinish (filename=0x57831ea53edd "s_lock.c", lineno=89, funcname=0x57831ea53ee8 <__func__.0>
"s_lock_stuck") at elog.c:609
#6 0x000057831e5f2185 in s_lock_stuck (file=0x57831ea5184c "lwlock.c", line=882, func=0x57831ea51c30 <__func__.5>
"LWLockWaitListLock") at s_lock.c:89
#7 0x000057831e5f2291 in perform_spin_delay (status=0x7ffdf9fabbe0) at
s_lock.c:135
#8 0x000057831e5e4015 in LWLockWaitListLock (lock=0x736a16ad6500) at
lwlock.c:886
#9 0x000057831e5e4475 in LWLockQueueSelf (lock=0x736a16ad6500,
mode=LW_EXCLUSIVE) at lwlock.c:1055
#10 0x000057831e5e4728 in LWLockAcquire (lock=0x736a16ad6500,
mode=LW_EXCLUSIVE) at lwlock.c:1259
#11 0x0000736a63dbcc82 in apw_dump_now (is_bgworker=false, dump_unlogged=true)
at autoprewarm.c:676
#12 0x0000736a63dbd5c9 in autoprewarm_dump_now (fcinfo=0x57835c770fe8) at
autoprewarm.c:854
...
Best regards,
Alexander
