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MEDIUM: stick-tables: Avoid freeing elements while holding a lock

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In stksess_trash_oldest(), and process_tables_expire(), avoid freeing
elements while holding two locks, as it could be very costly.
Instead, build a linked list of elements to be free'd, and do so once we
no longer hold any lock.

This may help with github issue #3380, and may be backported to 3.3.
This commit is contained in:
Olivier Houchard 2026-05-20 16:07:13 +02:00 committed by Olivier Houchard
parent 482b6763a3
commit 3e25104a9c
1 changed files with 21 additions and 3 deletions
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24
src/stick_table.c
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@ -276,6 +276,7 @@ int stktable_trash_oldest(struct stktable *t)
{
struct stksess *ts;
struct eb32_node *eb;
struct list tofree_list;
int max_search; // no more than 50% misses
int max_per_bucket;
int done_per_bucket;
@ -289,7 +290,7 @@ int stktable_trash_oldest(struct stktable *t)
/* start from a random bucket number to avoid starvation in the last ones */
bucket = init_bucket = statistical_prng_range(CONFIG_HAP_TBL_BUCKETS - 1);
LIST_INIT(&tofree_list);
to_batch = STKTABLE_MAX_UPDATES_AT_ONCE;
max_search = to_batch * 2; // no more than 50% misses
@ -390,7 +391,8 @@ int stktable_trash_oldest(struct stktable *t)
ebmb_delete(&ts->key);
MT_LIST_DELETE(&ts->pend_updts);
eb32_delete(&ts->upd);
__stksess_free(t, ts);
LIST_APPEND(&tofree_list, mt_list_to_list(&ts->pend_updts));
batched++;
done_per_bucket++;
@ -417,6 +419,12 @@ int stktable_trash_oldest(struct stktable *t)
bucket = 0;
} while (max_search > 0 && bucket != init_bucket);
while (!LIST_ISEMPTY(&tofree_list)) {
ts = LIST_ELEM(tofree_list.n, struct stksess *, pend_updts);
LIST_DELETE(mt_list_to_list(&ts->pend_updts));
__stksess_free(t, ts);
}
return batched;
}
@ -953,6 +961,7 @@ struct task *process_tables_expire(struct task *task, void *context, unsigned in
struct stktable *t;
struct stksess *ts;
struct eb32_node *table_eb, *eb;
struct list tofree_list;
int updt_locked;
int to_visit;
int task_exp;
@ -960,6 +969,8 @@ struct task *process_tables_expire(struct task *task, void *context, unsigned in
task_exp = TICK_ETERNITY;
LIST_INIT(&tofree_list);
bucket = (ps - &per_bucket[0]);
to_visit = STKTABLE_MAX_UPDATES_AT_ONCE;
@ -1088,7 +1099,7 @@ struct task *process_tables_expire(struct task *task, void *context, unsigned in
ebmb_delete(&ts->key);
MT_LIST_DELETE(&ts->pend_updts);
eb32_delete(&ts->upd);
__stksess_free(t, ts);
LIST_APPEND(&tofree_list, mt_list_to_list(&ts->pend_updts));
}
if (updt_locked)
@ -1110,6 +1121,13 @@ struct task *process_tables_expire(struct task *task, void *context, unsigned in
if (!tick_isset(task_exp) || (tick_isset(next_exp_table) && tick_is_lt(next_exp_table, task_exp)))
task_exp = next_exp_table;
HA_RWLOCK_WRUNLOCK(STK_TABLE_LOCK, &t->buckets[bucket].sh_lock);
while (!LIST_ISEMPTY(&tofree_list)) {
ts = LIST_ELEM(tofree_list.n, struct stksess *, pend_updts);
LIST_DELETE(mt_list_to_list(&ts->pend_updts));
__stksess_free(t, ts);
}
tmpnode = eb32_next(table_eb);
if (table_eb->key != next_exp_table) {