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PG-646: pg_stat_monitor hangs in pgsm_store 

A potential lock contention could've been caused when an OOM warning
was being emitted by the pgsm_store function. This could lead the
pg_store_error function calling pgsm_store function and thereby trying
to acquire and exclusive lock when a shared was already by the same
process. This warning is now guarded by protection block.
pull/434/head
Hamid Akhtar 2023-11-23 15:55:26 +05:00 committed by Muhammad Usama
parent 0a8ac38de9
commit 4863020ccd
1 changed files with 13 additions and 14 deletions
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27
pg_stat_monitor.c
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@ -1776,10 +1776,6 @@ pgsm_store(pgsmEntry * entry)
pgsm = pgsm_get_ss(); pgsm = pgsm_get_ss();
/*
* We should lock the hash table here what if the bucket is removed; e.g.
* reset is called - HAMID
*/
prev_bucket_id = pg_atomic_read_u64(&pgsm->current_wbucket); prev_bucket_id = pg_atomic_read_u64(&pgsm->current_wbucket);
bucketid = get_next_wbucket(pgsm); bucketid = get_next_wbucket(pgsm);
@ -1882,6 +1878,11 @@ pgsm_store(pgsmEntry * entry)
if (shared_hash_entry == NULL) if (shared_hash_entry == NULL)
{ {
LWLockRelease(pgsm->lock);
if (DsaPointerIsValid(dsa_query_pointer))
dsa_free(query_dsa_area, dsa_query_pointer);
/* /*
* Out of memory; report only if the state has changed now. * Out of memory; report only if the state has changed now.
* Otherwise we risk filling up the log file with these message. * Otherwise we risk filling up the log file with these message.
@ -1890,18 +1891,16 @@ pgsm_store(pgsmEntry * entry)
{ {
pgsm->pgsm_oom = true; pgsm->pgsm_oom = true;
ereport(WARNING, PGSM_DISABLE_ERROR_CAPUTRE();
(errcode(ERRCODE_OUT_OF_MEMORY), {
errmsg("[pg_stat_monitor] pgsm_store: Hash table is out of memory and can no longer store queries!"), ereport(WARNING,
errdetail("You may reset the view or when the buckets are deallocated, pg_stat_monitor will resume saving " \ (errcode(ERRCODE_OUT_OF_MEMORY),
"queries. Alternatively, try increasing the value of pg_stat_monitor.pgsm_max."))); errmsg("[pg_stat_monitor] pgsm_store: Hash table is out of memory and can no longer store queries!"),
errdetail("You may reset the view or when the buckets are deallocated, pg_stat_monitor will resume saving " \
"queries. Alternatively, try increasing the value of pg_stat_monitor.pgsm_max.")));
} PGSM_END_DISABLE_ERROR_CAPTURE();
} }
LWLockRelease(pgsm->lock);
if (DsaPointerIsValid(dsa_query_pointer))
dsa_free(query_dsa_area, dsa_query_pointer);
return; return;
} }
else else